JP2001015476A - One-side etching method for semiconductor wafer and apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one-sided etching method and device of a semiconductor wafer for improving productivity of the semiconductor wafer by reducing the processes of one-sided etching. SOLUTION: In the etching method, etching liquid is blown from a blow-off nozzle 14, that is provided at the center of the bottom plate of an inner bath 11A of an etching bath 11 for swelling a liquid surface, and the swelled part is brought into contact with one side of a silicon wafer W that is supported at an upper part for one-sided etching, thus dispensing with the time-consuming covering process of the other surface of a wafer by a film which was required in conventional one-sided etching and a process for eliminating the film after etching. As a result, the number of processes of the one-sided etching of the silicon wafer W can be reduced, thus improving the productivity of the silicon wafer W.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for etching one side of a semiconductor wafer, and more particularly, to a method of etching one side of a semiconductor wafer mainly by bringing one side of the semiconductor wafer into contact with an etching solution. And a single-sided etching method.

[0002]

2. Description of the Related Art In manufacturing a silicon wafer, for example, LTO (Low Temperature Oxi) is used.
dation) specification, thermal oxide film specification, IG
(Intrinsic Gettering) specifications. In the LTO product, a low-temperature oxide film is applied to the etched wafer, and only the LTO film on the mirror-finished surface is removed by one-sided etching. Thereafter, an epitaxial layer is laminated on this mirror surface in an epitaxial step. In the thermal oxide film product, the etched wafer HW is covered with a thermal oxide film, and one-sided etching is performed to remove the thermal oxide film.
The exposed silicon surface is mirror-polished. IG products are IG
A thin thermal oxide film may be formed on the polished wafer PW after the processing, and the thermal oxide film on the mirror side is removed by single-sided etching. As described above, in various silicon wafers, only one side is etched to remove an oxide film and the like. Conventionally, when etching one side of this silicon wafer, the side on the side to be etched, for example, the back side not mirrored in the LTO product, is covered with a film and immersed in an etchant to remove a low-temperature oxide film from the surface. I was That is, the conventional one-sided etching method is performed by dipping a wafer into an etching solution by applying a film.

[0003]

However, according to such prior art, the following problems have occurred. That is, (1) In the conventional one-sided etching, a film covering step of a non-etched surface of a silicon wafer and a step of removing a film after etching are required. as a result,
There has been a problem that the number of work steps increases and productivity decreases. This also leads to high costs. (2) Recently, in order to prevent the generation of nodules on the outer peripheral portion (chamfered surface) of the wafer during epitaxial growth of an LTO product, there has been an increasing demand that the entire outer peripheral portion be etched cleanly.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor wafer single-side etching method and apparatus which can reduce the number of single-side etching steps and thereby increase the productivity of semiconductor wafers. That is the purpose. Another object of the present invention is to provide a method and an apparatus for single-sided etching of a semiconductor wafer which can perform reliable and uniform single-sided etching. Still another object of the present invention is to provide a method and apparatus for single-sided etching of a semiconductor wafer capable of simultaneously removing the backside oxide film of the semiconductor wafer and the oxide film on the outer peripheral portion (chamfered surface) of the semiconductor wafer without lowering the productivity. For that purpose.

[0005]

According to a first aspect of the present invention, there is provided a method for etching a single side of a semiconductor wafer, the method comprising: contacting one side of the semiconductor wafer with a liquid surface of an etchant to etch the one side of the semiconductor wafer. It is. Examples of the semiconductor wafer include a silicon wafer and a gallium arsenide wafer. An oxide film or the like may or may not be provided on one surface of the semiconductor wafer. Further, the etchant is not limited. For example, HF, HF: NH ₄ F and the like can be mentioned.

[0006] The etching rate is not limited. For example, 5
000-18000 Angstroms / min. The preferred etch rate is 6000-8000 Å / min. If it is less than 5000 Å / min, uneven etching may occur, for example, an oxide film may remain on the outer peripheral portion of the wafer. On the other hand, if it exceeds 18000 angstroms / minute, the disadvantage of over-etching occurs.

During one-sided etching, the semiconductor wafer may or may not rotate about the center point of the semiconductor wafer. However, rotation is preferable because the etchant can be uniformly brought into contact with one surface of the semiconductor wafer. The method for bringing one surface of the semiconductor wafer into contact with the liquid surface of the etchant is not limited. For example, there is a method of arranging a semiconductor wafer on a stored liquid level, and then lowering the semiconductor wafer horizontally to contact the semiconductor wafer. In addition to the above, for example, a method of raising the liquid surface by blowing out an etching solution and bringing one surface of the semiconductor wafer into contact with this portion may be mentioned. Also, holding one side of the semiconductor wafer upward,
A method in which the etchant is dropped from above may be used. The one-sided etching time varies depending on the type of the etching product, the concentration of the etching solution, and the like. For example, for 30 to 250 seconds. The temperature of the etching solution during the etching is not limited. For example, 25-45 ° C, preferably 34-36
° C. If the temperature is lower than 25 ° C., the rate is low, and there is a disadvantage that an oxide film may remain. If it exceeds 45 ° C,
The composition is changed, so that the oxide film remains or overetching occurs. During the one-sided etching, the semiconductor wafer may be swung (translated in the horizontal direction). When swinging, the wafer swing amount is 80-160m
m, preferably 110 to 130 mm. If it is less than 80 mm, uneven etching occurs, and if it exceeds 160 mm, there is a problem that overetching is caused. Due to this swing, an effect is obtained that etching can be performed more uniformly than when only rotation is performed. The above items also correspond to claim 4.

[0010] According to a second aspect of the present invention, an etching solution is blown out from below the surface of the etching solution to raise the liquid surface,
2. The method according to claim 1, wherein one side of the rotating semiconductor wafer is brought into contact with the rising portion of the liquid surface. The direction in which the etchant is blown out is not limited as long as the level can be raised by the blown out etchant. However,
Usually, it is the direction toward the liquid surface. The flow rate of the etching solution is not limited as long as the level of the solution can be raised by the blown etching solution. Note that the blown-out etchant may not be a complete etchant, but may be, for example, a component constituting a part of the solution.

The contact position of the raised portion on one side of the wafer is not limited. For example, it may be a central portion on one side of the semiconductor wafer or an outer peripheral portion of the semiconductor wafer. This is because the surface of the contacted etching solution spreads over one surface of the semiconductor wafer due to the surface tension of the etching solution. In addition, since the semiconductor wafer rotates at a predetermined rotation speed, the spread of the semiconductor wafer over the entire area of one surface is further improved. However, it is preferable to arrange the center position of the raised portion at the center of the semiconductor wafer because it prevents the etchant from flowing to the back surface (the other surface) of the semiconductor wafer and allows the semiconductor wafer to rotate stably. The rotation speed of the semiconductor wafer is not limited. However, it is usually 1 to 10 rpm. These matters also correspond to claim 6.

According to a third aspect of the present invention, during one-sided etching, vaporized from the etching solution surface is wrapped around the surface of the semiconductor wafer on the side opposite to the one side, and the wraparound vapor causes the semiconductor wafer to be scattered. 3. The method according to claim 1, wherein the other surface of the outer peripheral portion is etched. A large amount of vapor of the etching liquid is generated from the liquid surface of the etching liquid including the raised part. This vapor is used to etch the chamfered surface at the outer peripheral portion of the semiconductor wafer. The length of the other surface of the semiconductor wafer to be etched by the vapor flow is not limited.

According to a fourth aspect of the present invention, there is provided the semiconductor wafer single-side etching method according to any one of the first to third aspects, wherein one surface of the semiconductor wafer has an oxide film.

According to a fifth aspect of the present invention, there is provided an etching tank for storing an etching solution, a wafer holding means disposed above the etching tank for holding a semiconductor wafer, and provided on the wafer holding means. And a semiconductor lifting means capable of lowering the semiconductor wafer to a height at which one surface of the semiconductor wafer can come in contact with the etching solution surface in the etching bath while keeping the surface of the semiconductor wafer horizontal. This is a single-sided wafer etching apparatus. The type of holding the semiconductor wafer by the wafer holding means is not limited. For example, the semiconductor wafer may be suction-held by suction as in the invention described in claim 7. Wafer elevating means is not limited as long as the mechanism can elevate the semiconductor wafer while keeping the semiconductor wafer in a horizontal state. To raise and lower the surface of the semiconductor wafer horizontally means, in other words, to raise and lower the semiconductor wafer in a state where the semiconductor wafer is held parallel to the liquid surface of the etching solution in a stationary state.

According to a sixth aspect of the present invention, a blowout nozzle for blowing out an etching solution to raise the level of the etching solution is provided in the etching tank, and the wafer elevating means rotates the semiconductor wafer while holding the semiconductor wafer horizontally. 6. The single-sided etching apparatus for a semiconductor wafer according to claim 5, further comprising a wafer rotating unit for causing the wafer to rotate. The installation position of the etching solution blowing nozzle is not limited as long as it is below the liquid level in the etching tank. That is, not only the lower part or the center part of the etching bath but also the vicinity of the liquid surface may be used.
The structure of the wafer rotating unit is not limited. It is sufficient that the semiconductor wafer can be horizontally rotated at a predetermined speed by a driving source such as a motor.

According to a seventh aspect of the present invention, the wafer holding means has a wafer holder for adsorbing a central portion of a surface opposite to one surface of the semiconductor wafer, and the semiconductor wafer is held by the wafer holder. On the radially outer side, a flange portion is formed between the suction side surface of the semiconductor wafer and a gas sending gap for sending out an inert gas to an outer peripheral side of the suction side surface of the semiconductor wafer. A single-side etching apparatus for a semiconductor wafer according to claim 5 or 6. The shape of the wafer holder is not limited. For example, it may be plate-shaped or block-shaped. For example, a suction hole connected to an external air suction device may be formed on the contact surface of the semiconductor wafer.

The type of the inert gas is not limited. For example, such as _{N 2} gas. The flange portion here is for forming a gas sending gap for sending the inert gas to the outer peripheral side of the suction side surface of the semiconductor wafer. By sending the inert gas to the outer peripheral portion of the semiconductor wafer, it is possible to prevent the vapor from going too far toward the central portion of the semiconductor wafer beyond the outer peripheral portion of the suction side surface of the semiconductor wafer. A gas supply port for supplying an inert gas to the gas delivery gap may be provided in this flange portion, or may be provided in the wafer holder. When provided on the flange, for example, the flange may be attached to the wafer holder so as to be freely rotatable, and a gas supply pipe extending from an inert gas supply device may be connected to the gas supply port.

[0016]

According to the present invention, since one surface of a semiconductor wafer is brought into contact with the surface of an etching solution and only one surface of the semiconductor wafer is etched, a time-consuming film required in conventional one-side etching. Therefore, the step of coating the surface on the opposite side of the semiconductor wafer and the step of removing the film after etching become unnecessary. As a result, the number of steps of one-sided etching of the semiconductor wafer can be reduced, and thereby the productivity of the one-sided etching of the semiconductor wafer can be increased.

In particular, according to the second and sixth aspects of the present invention, the etching liquid is blown out from below the liquid surface of the etching liquid to raise the liquid surface, and the raised portion of the liquid surface is rotated. One side of the inside semiconductor wafer is brought into contact. At this time, even if the contact portion is a part of one surface of the semiconductor wafer, due to the surface tension of the etching solution,
This etchant spreads favorably over one surface of the semiconductor wafer. This makes it possible to perform reliable and uniform one-sided etching. Moreover, since the semiconductor wafer is rotating, the spread of the etchant over one surface of the semiconductor wafer is further improved.

According to the third and seventh aspects of the present invention, a highly volatile etching component (for example, HF) is always vaporized from the etching liquid surface. Therefore, during this one-sided etching, the vapor is made to flow to the other side of the semiconductor wafer. In this way, the escaping vapor is brought into contact with the outer peripheral portion of the other surface of the semiconductor wafer which is not in contact with the etchant. As a result, the etching of the chamfered portion can be performed by the vapor. Therefore, one surface of the semiconductor wafer and its outer peripheral portion can be etched without lowering the productivity.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, for convenience of explanation, the X direction is the apparatus length direction, the Y direction is the apparatus width direction, and the Z direction is the up and down direction. FIG. 1 is a schematic configuration diagram of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention. FIG. 2 is an enlarged sectional view of a main part of the wafer holding means during one-sided etching according to one embodiment of the present invention. FIG.
FIG. 1 is a perspective view schematically showing a drive system of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention. FIG. 4 is a bottom view showing the wafer holding means according to one embodiment of the present invention.

In these figures, reference numeral 10 denotes a single-sided etching apparatus for a semiconductor wafer (hereinafter referred to as a single-sided etching apparatus 1).
0), and the etching apparatus 10 is set in the booth 102. This single-sided etching apparatus 10
An etching bath 11, a wafer holding unit 12, and a wafer elevating unit 13 are provided. A spin dryer 103 for drying a wafer is provided in the booth 102 adjacent to the etching tank 11. An etching solution (HF: NH ₄ F = 25: 12) is stored in the etching tank 11 up to the upper part of the tank. Wafer holding means 12
Is disposed above the etching tank 11 and can horizontally hold, for example, a silicon wafer W having a thickness of 625 μm and a diameter of 6 inches. Wafer elevating means 13
Is provided in the wafer holding means 12 to raise and lower the silicon wafer W while keeping the surface of the wafer horizontal. The front and back surfaces of the silicon wafer W are covered with an oxide film having a predetermined thickness. This etching tank 11
Is composed of a separated inner tank 11A and outer tank 11B. At the center of the bottom surface of the inner tank 11A, there is provided a blowing nozzle 14 that blows out the etching liquid just above and raises the liquid surface to a predetermined height. Spout nozzle 1
4, an etching solution overflowing from the inner tank 11A and discharged to the outer tank 11B is led out via the circulation pipe 15a, filtered and returned from the blowing nozzle 14 into the inner tank 11A. Liquid circulation device 1
5 is connected.

A flow meter 15C, a circulation pump 16, and a filter 17 are connected to the circulation pipe 15a in order from the upstream side. Further, a filter can be interposed in the middle of the circulation pipe 15a. The circulating pump 16 blows out the etching solution from the nozzle 14 to a position of 0.1 mm.
It is a pump that can blow out at 5 to 5.0 liters / minute. Further, in order to keep the etching liquid at a constant temperature, an etching liquid temperature controller 100 is provided in the etching bath 11. The etching solution discharged from the outer tank 11B is circulated to the outer tank 11B via the temperature control device 100 and supplied. The temperature control device 100 has a temperature control coil 101 disposed close to the etching liquid pipe. The etching solution is adjusted to a constant temperature by causing heat exchange between the temperature control coil 101 and the etching solution.

Next, the wafer holding means 12 and the wafer elevating means 13 will be described in detail with reference to FIGS. First, the wafer elevating means 13 will be described. The wafer elevating means 13 includes a vertical rotating shaft 18 and the rotating shaft 18.
Arm 19 that rotatably supports the front end of the arm, and a traveling body 40 that supports the base end of the horizontal arm 19 so as to be vertically movable.
And The traveling body 40 can travel in the longitudinal direction of the booth 102, and transfers the wafer between the etching tank 11 and the spin dryer 103. The horizontal arm 19 is supported by a traveling body 40 so as to be able to move up and down, and a motor for driving and rotating the rotating shaft 18 and the like are built therein. That is, the configuration is such that the silicon wafer W is horizontally rotated at a predetermined rotation speed by this motor. The lower end of the rotation shaft 18 is connected to the wafer holding means 12. The wafer holding means 12 includes a disk-shaped wafer holder 21 provided at the lower end of the rotating shaft 18.
And a block body 22 extrapolated to the rotating shaft 18, and a flange 23 fixed to the lower end surface of the block body 22. The flange portion 23 is a gas sending gap a for sending N ₂ gas (inert gas) to the outer peripheral side of the back surface of the wafer between the upper surface of the silicon wafer W and the upper surface of the silicon wafer W outside the wafer holder 21 in the wafer radial direction. Is formed.

The wafer holder 21 is a thick disk.
On its lower surface, a plurality of suction holes 21b for sucking the center of the other surface (upper surface) opposite to one surface of the silicon wafer W are formed. The suction hole 21b communicates with an external negative pressure generating device via a suction hole 19b formed in each axis of the rotary shaft 18. Therefore, the silicon wafer W is sucked and held on the lower surface of the wafer holder 21 by the negative pressure generated by the operation of the negative pressure generator. The block body 22 is a cylindrical body having an opening at the lower end. And an annular plate 22c connecting the upper ends of the two.

The inner cylindrical portion 22a is fixed to the upper surface of the wafer holder 21 via a liner 24. In addition, the annular plate 22c has N
A plurality of gas holes for supplying _two gases are drilled. Gas can be supplied from the gas pipe 50 to this gas hole. That is, the gas pipe 50 is connected to and connected to the gas hole by the plurality of branch pipes 52 via the annular pipe portion 51 provided above the block body 22. Therefore, gas pipes 50 from the _{N 2} gas supply source, the pipe section 51, _{N 2} gas is supplied into the inner space via the branch pipe 52. The supply of the N ₂ gas is controlled by a control unit (not shown). This internal space communicates with the gas sending gap a, and N ₂ gas is supplied to the gas holes. The block body 22 is externally inserted by a set nut screwed to an external screw of the rotary shaft 18 without rattling in the axial direction of the shaft. On the other hand, the flange portion 23 is detachably fixed to the block body 22 via an embedding pin 26.
The gas sending gap a formed between the lower surface (one surface) of the flange portion 23 and the upper surface (the other surface) of the silicon wafer W adsorbed on the wafer holder 21 is, for example, 1 to 20 m.
m. The flange 23 has a length b of 1 to 20 mm from which the outer peripheral portion of the silicon wafer W protrudes.
It is designed to be.

Next, a single-sided etching method using the single-sided etching apparatus 10 according to one embodiment of the present invention will be described. As shown in FIGS. 1 and 2, first, the silicon wafer W is sucked and held on one surface of the wafer holder 21 by the negative pressure generated by the operation of the negative pressure generator. Thereafter, while rotating the silicon wafer W at 1 to 10 rpm by a rotation motor, the rotating shaft 18 is made to protrude, and the silicon wafer W
Is inserted horizontally into the internal space of the etching bath 11 from the opening of the bath. At this time, the height of the stopped silicon wafer W from the etching liquid surface to the lower surface of the silicon wafer is, for example, 5 to 30 mm. The front and back surfaces of the silicon wafer W are covered with a thermal oxide film having a predetermined thickness.

Next, the circulation pump 16 is operated to move 5 to 3 from the blowing nozzle 14 toward the etching liquid surface.
Blow out the etchant at 0 liter / min. As a result, the liquid level at the center of the etching liquid stored in the inner cylindrical portion 11A rises by 5 to 30 mm. Therefore, the raised portion comes into contact with the center of one surface on the mirror-finished side of the silicon wafer W horizontally held above the liquid surface. At this time, due to the surface tension of the etchant, the etchant spreads over one surface of the silicon wafer and then drops.
Thereby, the oxide film on one side of the silicon wafer W
It is reliably and uniformly removed. Moreover, the silicon wafer W is horizontally rotated by the rotation motor 19 during the one-sided etching. Therefore, the spread of the etching solution over the entire single-sided oxide film of the silicon wafer is further improved.
As a result, the effect of removing the oxide film on one side of the wafer is enhanced.

A highly volatile etching component is constantly vaporized from the etching solution level in the etching tank 11. After contacting one side of the silicon wafer W,
The same applies to the case of an etching solution that spreads in the wafer radial direction due to surface tension and falls. As a result, as shown in the partial enlarged view of FIG. 2, the vapor (etching vapor) volatilized from the liquid surface of the etching liquid flows to the other surface side of the silicon wafer W. The oxide film Wa covering the outer peripheral portion of the silicon wafer W is removed by the wrapped vapor. Thus, the oxide film in the chamfered portion can be etched simultaneously with the one-sided etching without lowering the productivity. Part of the steam that has flowed in tries to flow into the internal space of the block body 22 from the gas delivery gap a. However, in this single-sided etching, constantly, N ₂ gas supplied from the gas holes, is flowing to the outside from the gap for gas delivery a 5 to 80 liters / min. Therefore, the excessive wraparound of the vapor containing the etching component toward the central portion of the wafer is prevented. as a result,
Oxide film Wa on the other surface of the wafer, except for the outer peripheral portion of the wafer,
It remains after one-sided etching. In this case, by adjusting the blowing amount of the N ₂ gas, it is possible to adjust the amount of the vapor flowing into the other surface (front surface) of the wafer.
The amount of etching of the outer edge portion of the oxide film on the wafer surface side can be adjusted as appropriate. Most of the generated steam is led out to the etching steam processing equipment.

As described above, since one side of the silicon wafer W is brought into contact with the liquid surface of the etching solution to etch the one side of the wafer, the wafer by a complicated film which is required at the time of the conventional one side etching. Both the step of coating the other surface and the step of removing the film after etching become unnecessary. As a result, the number of single-side etching steps of the silicon wafer W can be reduced. Therefore, the productivity of the silicon wafer W can be improved. In addition, the gap a for gas delivery is 0.2 to 2.0 m.
m, the length b of the outer peripheral portion of the wafer protruding from the tip of the flange portion 23 was designed to be 0 to 5 mm. Therefore, the N ₂ gas was supplied at a supply amount of 5 to 80 liter / min. Only the oxide film Wa can be satisfactorily removed. Note that, in this embodiment, an example in which the N ₂ gas is discharged from the gas delivery gap a has been described, but the present invention is not limited to this. That is, the external discharge of the N ₂ gas does not necessarily have to be performed.

[0029]

According to the present invention, since one surface of the semiconductor wafer is etched by bringing one surface of the semiconductor wafer into contact with the liquid surface of the etching solution, the total number of steps of one-side etching is reduced, and the productivity of the semiconductor wafer is reduced. Enhanced. This is because the efficiency in the single-sided etching step can be increased as compared with the conventional case. In addition, the cost required for one-sided etching can be reduced as a whole as compared with the related art.

In particular, according to the second and sixth aspects of the present invention, the etching liquid surface is raised, and this portion is brought into contact with one surface of the semiconductor wafer. The liquid can be spread well. Thereby, reliable and uniform one-sided etching can be performed. In addition, since the semiconductor wafer is rotated during the one-sided etching, the spread of the liquid over the entire surface of the semiconductor wafer is further improved.

According to the third and seventh aspects of the present invention, the outer peripheral portion of the other surface of the semiconductor wafer which is not in direct contact with the etchant is etched (gas etched) by the etching vapor. The etching of the outer peripheral portion of the semiconductor wafer can be performed simultaneously with the single-sided etching without lowering the productivity.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an outline of an entire configuration of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the wafer holding means according to one embodiment of the present invention.

FIG. 3 is a perspective view schematically showing a drive system of the semiconductor wafer single-side etching apparatus according to one embodiment of the present invention.

FIG. 4 is a bottom view showing the wafer holding means according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Single-sided etching apparatus of semiconductor wafer, 11 Etching tank, 12 Wafer holding means, 13 Wafer elevating means, 14 Blowing nozzle, 19 Rotary motor (wafer rotating part), 21 Wafer holder, W Silicon wafer (semiconductor wafer), a gas Delivery gap.

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[Procedure amendment]

[Submission date] March 27, 2000 (2003.
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Method and Apparatus for Single-Side Etching of Semiconductor Wafer

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for etching one side of a semiconductor wafer, and more particularly, to a method of etching one side of a semiconductor wafer mainly by bringing one side of the semiconductor wafer into contact with an etching solution. And a single-sided etching method.

[0002]

2. Description of the Related Art In a silicon wafer, for example, L
TO (Low Temperature Oxidat)
ion) specification, thermal oxide film specification, IG (In)
(trinsic gettering) specifications. In the LTO product, a low-temperature oxide film is applied to the etched wafer, and only the LTO film on the mirror-finished surface is removed by one-sided etching. Thereafter, an epitaxial layer is laminated on this mirror surface in an epitaxial step. In the thermal oxide film product, the etched wafer HW is covered with a thermal oxide film, and one-sided etching is performed to remove the thermal oxide film. The exposed silicon surface is mirror-polished. In the IG product, a thin thermal oxide film may be formed on the mirror-finished wafer PW after the IG processing, and the thermal oxide film on the mirror surface is removed by one-sided etching. As described above, in various silicon wafers, only one side is etched to remove an oxide film and the like. Conventionally, when etching one side of this silicon wafer, the side on the side to be etched, for example, the back side not mirrored in the LTO product, is covered with a film and immersed in an etchant to remove a low-temperature oxide film from the surface. I was That is, the conventional one-sided etching method is performed by dipping a wafer into an etching solution by applying a film.

[0003]

However, according to such prior art, the following problems have occurred. That is, (1) In the conventional one-sided etching, a film covering step of a non-etched surface of a silicon wafer and a step of removing a film after etching are required. as a result,
There has been a problem that the number of work steps increases and productivity decreases. This also leads to high costs. (2) Recently, in order to prevent the generation of nodules on the outer peripheral portion (chamfered surface) of the wafer during epitaxial growth of an LTO product, there has been an increasing demand that the entire outer peripheral portion be etched cleanly.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor wafer single-side etching method and apparatus which can reduce the number of single-side etching steps and thereby increase the productivity of semiconductor wafers. That is the purpose. Another object of the present invention is to provide a method and an apparatus for single-sided etching of a semiconductor wafer which can perform reliable and uniform single-sided etching. Still another object of the present invention is to provide a method and apparatus for single-sided etching of a semiconductor wafer capable of simultaneously removing the backside oxide film of the semiconductor wafer and the oxide film on the outer peripheral portion (chamfered surface) of the semiconductor wafer without lowering the productivity. For that purpose.

[0005]

According to the first aspect of the present invention, an etching solution is blown out from below the surface of the etching solution to raise the liquid surface, and one side of the semiconductor wafer is brought into contact with the raised portion of the liquid surface. A method of etching a semiconductor wafer on one side, wherein when one side of the semiconductor wafer is in contact with an etching solution, vaporized from the etching solution is wrapped around the surface opposite to the one side of the semiconductor wafer. The other side of the outer peripheral portion of the semiconductor wafer is etched by the wrapped vapor,
This is a method for single-sided etching of a semiconductor wafer in which an inert gas is blown out to the other side of the semiconductor wafer to control the amount of the vapor wraparound. Examples of the semiconductor wafer include a silicon wafer and a gallium arsenide wafer. An oxide film or the like may or may not be provided on one surface of the semiconductor wafer. Further, the etchant is not limited. For example, HF,
HF: NH ₄ F and the like.

[0006] The etching rate is not limited. For example, 5
000-18000 Angstroms / min. The preferred etch rate is 6000-8000 Å / min. If it is less than 5000 Å / min, uneven etching may occur, for example, an oxide film may remain on the outer peripheral portion of the wafer. On the other hand, if it exceeds 18000 angstroms / minute, the disadvantage of over-etching occurs.

During one-sided etching, the semiconductor wafer may or may not rotate about the center point of the semiconductor wafer. However, rotation is preferable because the etchant can be uniformly brought into contact with one surface of the semiconductor wafer. The time required for single-sided etching varies depending on the type of the etching product, the concentration of the etching solution, and the like. For example, for 30 to 250 seconds. The temperature of the etching solution during the etching is not limited. For example, 25-4
The temperature is 5 ° C, preferably 34 to 36 ° C. If the temperature is lower than 25 ° C., the rate is low, and there is a disadvantage that an oxide film may remain. If the temperature exceeds 45 ° C., the composition is changed, and there arises an inconvenience that an oxide film remains or overetch occurs. In addition,
During this one-sided etching, the semiconductor wafer may be swung (translated in the horizontal direction). When swinging, the amount of wafer swing is 80 to 160 mm, preferably 110 to 13 mm.
0 mm. If it is less than 80 mm, uneven etching occurs, and if it exceeds 160 mm, there is a problem that overetching is caused. Due to this swing, an effect is obtained that etching can be performed more uniformly than when only rotation is performed. The etching liquid is blown out from below the liquid surface of the etching liquid to raise the liquid surface, and the direction of the blowing of the etching liquid when the one side of the rotating semiconductor wafer is brought into contact with the raised part of the liquid surface is determined by the blown etching liquid. The direction is not limited as long as the liquid surface can be raised. Usually, it is the direction toward the liquid surface. The flow rate of the etching solution is not limited as long as the level of the solution can be raised by the blown etching solution. Note that the blown-out etchant may not be a complete etchant, but may be, for example, a component constituting a part of the solution.

[0008] The contact position of the raised portion on one side of the wafer is not limited. For example, it may be a central portion on one side of the semiconductor wafer or an outer peripheral portion of the semiconductor wafer. This is because the surface of the contacted etching solution spreads over one surface of the semiconductor wafer due to the surface tension of the etching solution. In addition, since the semiconductor wafer rotates at a predetermined rotation speed, the spread of the semiconductor wafer over the entire area of one surface is further improved. However, it is preferable to arrange the center position of the raised portion at the center of the semiconductor wafer because it prevents the etchant from flowing to the back surface (the other surface) of the semiconductor wafer and allows the semiconductor wafer to rotate stably. The rotation speed of the semiconductor wafer is not limited. Usually 1 to 1
0 rpm. A large amount of vapor of the etching liquid is generated from the liquid surface of the etching liquid including the raised part.
Using this vapor, the chamfered surface and the other surface of the outer peripheral portion of the semiconductor wafer are etched. Further, the wraparound amount is controlled by blowing out an inert gas. As a result, it is possible to control the etching range (distance inward in the radial direction from the outer peripheral edge) of the other surface of the semiconductor wafer. The range of the other surface of the semiconductor wafer to be etched by the wraparound of the vapor can be arbitrarily controlled.

According to a second aspect of the present invention, there is provided the method for etching a single side of a semiconductor wafer according to the first aspect, wherein one side of the semiconductor wafer has an oxide film.

According to a third aspect of the present invention, there is provided an etching tank in which an etching solution is stored, a wafer holding means arranged above the etching tank to hold a semiconductor wafer, and a surface of the held semiconductor wafer. In a horizontal state, the semiconductor wafer single-side etching apparatus is provided with a wafer elevating means capable of lowering the semiconductor wafer to a position where one side of the semiconductor wafer can contact the etching liquid surface in the etching bath. The wafer holding means has a wafer holder that adsorbs a central portion of a surface opposite to one surface of the semiconductor wafer, and a flange is provided outside the wafer holder in a radial direction of the semiconductor wafer. The part sends out an inert gas between the suction side surface of the semiconductor wafer and the outer peripheral side of the suction side surface of the semiconductor wafer. To form a scan delivery for clearance,
This is a semiconductor wafer single-sided etching apparatus in which the outer edge of the semiconductor wafer is arranged radially outside of the gas delivery gap. The type of holding the semiconductor wafer by the wafer holding means is not limited. For example, the semiconductor wafer may be suction-held by suction. The wafer elevating means may be any mechanism that can elevate the semiconductor wafer while keeping the semiconductor wafer horizontal. Raising and lowering the surface of the semiconductor wafer horizontally means, in other words, raising and lowering the semiconductor wafer while keeping the semiconductor wafer parallel to the liquid level of the etching solution in a stationary state. The shape of the wafer holder may be, for example, a plate shape or a block shape. For example, a suction hole connected to an external air suction device may be formed on the contact surface of the semiconductor wafer.

As the inert gas, for example, N ₂ gas is used. The flange portion here is for forming a gas sending gap for sending out the inert gas to the outer peripheral side of the suction side surface of the semiconductor wafer. By sending the inert gas to the outer peripheral portion of the semiconductor wafer, it is possible to control the amount of the vapor flowing toward the center of the semiconductor wafer beyond the outer peripheral portion of the surface of the semiconductor wafer on the suction side.
For example, it is possible to prevent the wraparound. Since the gas sending gap is located radially inward of the outer edge of the semiconductor wafer, the control is easy.
A gas supply port for supplying an inert gas to the gas delivery gap may be provided in this flange portion, or may be provided in the wafer holder. When provided on the flange, for example, the flange may be attached to the wafer holder so as to be freely rotatable, and a gas supply pipe extending from an inert gas supply device may be connected to the gas supply port.

According to a fourth aspect of the present invention, a blowout nozzle for blowing out an etching solution to raise the level of the etching solution is provided in the etching tank, and the wafer elevating means rotates the semiconductor wafer while holding the semiconductor wafer horizontally. 4. The single-sided etching apparatus for a semiconductor wafer according to claim 3, further comprising a wafer rotating unit for causing the wafer to rotate. The installation position of the etching solution blowing nozzle is not limited as long as it is below the liquid level in the etching tank. That is, not only the lower part or the center part of the etching bath but also the vicinity of the liquid surface may be used.
The structure of the wafer rotating unit is not limited. It is sufficient that the semiconductor wafer can be horizontally rotated at a predetermined speed by a driving source such as a motor.

[0013]

According to the present invention, since one surface of a semiconductor wafer is brought into contact with the surface of an etching solution and only one surface of the semiconductor wafer is etched, a time-consuming film required in conventional one-side etching. Therefore, the step of coating the surface on the opposite side of the semiconductor wafer and the step of removing the film after etching become unnecessary. As a result, the number of steps of one-sided etching of the semiconductor wafer can be reduced, and thereby the productivity of the one-sided etching of the semiconductor wafer can be increased.

In particular, the etching liquid is blown out from below the liquid surface of the etching liquid to raise the liquid surface, and one side of the rotating semiconductor wafer is brought into contact with the raised portion of the liquid surface. At this time, even if the contact portion is a part of one surface of the semiconductor wafer, the etching solution spreads favorably over the entire surface of the semiconductor wafer due to the surface tension of the etching solution. This makes it possible to perform reliable and uniform one-sided etching. Moreover, since the semiconductor wafer is rotating, the spread of the etchant over one surface of the semiconductor wafer is further improved.

Further, a highly volatile etching component (for example, HF) is constantly vaporized from the etching liquid surface. Therefore, during this one-sided etching, the vapor is made to flow to the other side of the semiconductor wafer. In this way, the escaping vapor is brought into contact with the outer peripheral portion of the other surface of the semiconductor wafer which is not in contact with the etchant. As a result, etching of the chamfered portion and the outer peripheral edge of the other surface can be performed by the vapor.
Therefore, it is possible to perform etching on one surface of the semiconductor wafer and a portion near the outer peripheral portion thereof without lowering the productivity.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, for convenience of explanation, the X direction is the apparatus length direction, the Y direction is the apparatus width direction, and the Z direction is the up and down direction. FIG. 1 is a schematic configuration diagram of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention. FIG. 2 is an enlarged sectional view of a main part of the wafer holding means during one-sided etching according to one embodiment of the present invention. FIG.
FIG. 1 is a perspective view schematically showing a drive system of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention. FIG. 4 is a bottom view showing the wafer holding means according to one embodiment of the present invention.

In these figures, reference numeral 10 denotes a single-sided etching apparatus for a semiconductor wafer (hereinafter referred to as a single-sided etching apparatus 1).
0), and the etching apparatus 10 is set in the booth 102. This single-sided etching apparatus 10
An etching bath 11, a wafer holding unit 12, and a wafer elevating unit 13 are provided. A spin dryer 103 for drying a wafer is provided in the booth 102 adjacent to the etching tank 11. An etching solution (HF: NH ₄ F = 25: 12) is stored in the etching tank 11 up to the upper part of the tank. Wafer holding means 12
Is disposed above the etching tank 11 and can horizontally hold, for example, a silicon wafer W having a thickness of 625 μm and a diameter of 6 inches. Wafer elevating means 13
Is provided in the wafer holding means 12 to raise and lower the silicon wafer W while keeping the surface of the wafer horizontal. The front and back surfaces of the silicon wafer W are covered with an oxide film having a predetermined thickness. This etching tank 11
Is composed of a separated inner tank 11A and outer tank 11B. At the center of the bottom surface of the inner tank 11A, there is provided a blowing nozzle 14 that blows out the etching liquid just above and raises the liquid surface to a predetermined height. Spout nozzle 1
4, an etching solution overflowing from the inner tank 11A and discharged to the outer tank 11B is led out via the circulation pipe 15a, filtered and returned from the blowing nozzle 14 into the inner tank 11A. Liquid circulation device 1
5 is connected.

A flow meter 15C, a circulation pump 16 and a filter 17 are connected to the circulation pipe 15a in order from the upstream side. Further, a filter can be interposed in the middle of the circulation pipe 15a. The circulating pump 16 blows out the etching solution from the nozzle 14 to a position of 0.1 mm.
It is a pump that can blow out at 5 to 5.0 liters / minute. Further, in order to keep the etching liquid at a constant temperature, an etching liquid temperature controller 100 is provided in the etching bath 11. The etching solution discharged from the outer tank 11B is circulated to the outer tank 11B via the temperature control device 100 and supplied. The temperature control device 100 has a temperature control coil 101 disposed close to the etching liquid pipe. The etching solution is adjusted to a constant temperature by causing heat exchange between the temperature control coil 101 and the etching solution.

Next, the wafer holding means 12 and the wafer elevating means 13 will be described in detail with reference to FIGS. First, the wafer elevating means 13 will be described. The wafer elevating means 13 includes a vertical rotating shaft 18 and the rotating shaft 18.
Arm 19 that rotatably supports the front end of the arm, and a traveling body 40 that supports the base end of the horizontal arm 19 so as to be vertically movable.
And The traveling body 40 can travel in the longitudinal direction of the booth 102, and transfers the wafer between the etching tank 11 and the spin dryer 103. The horizontal arm 19 is supported by a traveling body 40 so as to be able to move up and down, and a motor for driving and rotating the rotating shaft 18 and the like are built therein. That is, the configuration is such that the silicon wafer W is horizontally rotated at a predetermined rotation speed by this motor. The lower end of the rotation shaft 18 is connected to the wafer holding means 12. The wafer holding means 12 includes a disk-shaped wafer holder 21 provided at the lower end of the rotating shaft 18.
And a block body 22 extrapolated to the rotating shaft 18, and a flange 23 fixed to the lower end surface of the block body 22. The flange portion 23 is a gas sending gap a for sending N ₂ gas (inert gas) to the outer peripheral side of the back surface of the wafer between the upper surface of the silicon wafer W and the upper surface of the silicon wafer W outside the wafer holder 21 in the wafer radial direction. Is formed.

The wafer holder 21 is a thick disk.
On its lower surface, a plurality of suction holes 21b for sucking the center of the other surface (upper surface) opposite to one surface of the silicon wafer W are formed. The suction hole 21b communicates with an external negative pressure generating device via a suction hole 19b formed in each axis of the rotary shaft 18. Therefore, the silicon wafer W is sucked and held on the lower surface of the wafer holder 21 by the negative pressure generated by the operation of the negative pressure generator. The block body 22 is a cylindrical body having an opening at the lower end. And an annular plate 22c connecting the upper ends of the two.

The inner cylindrical portion 22a is fixed to the upper surface of the wafer holder 21 via a liner 24. In addition, the annular plate 22c has N
A plurality of gas holes for supplying _two gases are drilled. Gas can be supplied from the gas pipe 50 to this gas hole. That is, the gas pipe 50 is connected to and connected to the gas hole by the plurality of branch pipes 52 via the annular pipe portion 51 provided above the block body 22. Therefore, gas pipes 50 from the _{N 2} gas supply source, the pipe section 51, _{N 2} gas is supplied into the inner space via the branch pipe 52. The supply of the N ₂ gas is controlled by a control unit (not shown). This internal space communicates with the gas sending gap a, and N ₂ gas is supplied to the gas holes. The block body 22 is externally inserted by a set nut screwed to an external screw of the rotary shaft 18 without rattling in the axial direction of the shaft. On the other hand, the flange portion 23 is detachably fixed to the block body 22 via an embedding pin 26.
The gas sending gap a formed between the lower surface (one surface) of the flange portion 23 and the upper surface (the other surface) of the silicon wafer W adsorbed on the wafer holder 21 is, for example, 1 to 20 m.
m. The flange 23 has a length b of 1 to 20 mm from which the outer peripheral portion of the silicon wafer W protrudes.
It is designed to be.

Next, a one-sided etching method using the one-sided etching apparatus 10 according to one embodiment of the present invention will be described. As shown in FIGS. 1 and 2, first, the silicon wafer W is sucked and held on one surface of the wafer holder 21 by the negative pressure generated by the operation of the negative pressure generator. Thereafter, while rotating the silicon wafer W at 1 to 10 rpm by a rotation motor, the rotating shaft 18 is made to protrude, and the silicon wafer W
Is inserted horizontally into the internal space of the etching bath 11 from the opening of the bath. At this time, the height of the stopped silicon wafer W from the etching liquid surface to the lower surface of the silicon wafer is, for example, 5 to 30 mm. The front and back surfaces of the silicon wafer W are covered with a thermal oxide film having a predetermined thickness.

Next, the circulation pump 16 is operated to move 5 to 3 from the blowing nozzle 14 toward the etching liquid surface.
Blow out the etchant at 0 liter / min. As a result, the liquid level at the center of the etching liquid stored in the inner cylindrical portion 11A rises by 5 to 30 mm. Therefore, the raised portion comes into contact with the center of one surface on the mirror-finished side of the silicon wafer W horizontally held above the liquid surface. At this time, due to the surface tension of the etchant, the etchant spreads over one surface of the silicon wafer and then drops.
Thereby, the oxide film on one side of the silicon wafer W
It is reliably and uniformly removed. Moreover, the silicon wafer W is horizontally rotated by the rotation motor 19 during the one-sided etching. Therefore, the spread of the etching solution over the entire single-sided oxide film of the silicon wafer is further improved.
As a result, the effect of removing the oxide film on one side of the wafer is enhanced.

A highly volatile etching component is constantly vaporized from the etching solution level in the etching tank 11. After contacting one side of the silicon wafer W,
The same applies to the case of an etching solution that spreads in the wafer radial direction due to surface tension and falls. As a result, as shown in the partial enlarged view of FIG. 2, the vapor (etching vapor) volatilized from the liquid surface of the etching liquid flows to the other surface side of the silicon wafer W. The oxide film Wa covering the outer peripheral portion of the silicon wafer W is removed by the wrapped vapor. Thus, the oxide film in the chamfered portion can be etched simultaneously with the one-sided etching without lowering the productivity. Part of the steam that has flowed in tries to flow into the internal space of the block body 22 from the gas delivery gap a. However, in this single-sided etching, constantly, N ₂ gas supplied from the gas holes, is flowing to the outside from the gap for gas delivery a 5 to 80 liters / min. Therefore, the excessive wraparound of the vapor containing the etching component toward the central portion of the wafer is prevented. as a result,
Oxide film Wa on the other surface of the wafer, except for the outer peripheral portion of the wafer,
It remains after one-sided etching. In this case, by adjusting the blowing amount of the N ₂ gas, it is possible to adjust the amount of the vapor flowing into the other surface (front surface) of the wafer.
The amount of etching of the outer edge portion of the oxide film on the wafer surface side can be adjusted as appropriate. Most of the generated steam is led out to the etching steam processing equipment.

As described above, since one surface of the silicon wafer W is brought into contact with the liquid surface of the etching solution and the one surface of the silicon wafer W is etched, a wafer with a complicated film which is required at the time of conventional one-side etching is required. Both the step of coating the other surface and the step of removing the film after etching become unnecessary. As a result, the number of single-side etching steps of the silicon wafer W can be reduced. Therefore, the productivity of the silicon wafer W can be improved. In addition, the gap a for gas delivery is 0.2 to 2.0 m.
m, the length b of the outer peripheral portion of the wafer protruding from the tip of the flange portion 23 was designed to be 0 to 5 mm. Therefore, the N ₂ gas was supplied at a supply amount of 5 to 80 liter / min. Only the oxide film Wa can be satisfactorily removed. Note that, in this embodiment, an example in which the N ₂ gas is discharged from the gas delivery gap a has been described, but the present invention is not limited to this. That is, the external discharge of the N ₂ gas does not necessarily have to be performed.

[0026]

According to the present invention, since one surface of the semiconductor wafer is etched by bringing one surface of the semiconductor wafer into contact with the liquid surface of the etching solution, the total number of steps of one-side etching is reduced, and the productivity of the semiconductor wafer is reduced. Enhanced. This is because the efficiency in the single-sided etching step can be increased as compared with the conventional case. In addition, the cost required for one-sided etching can be reduced as a whole as compared with the related art.

In particular, since the etching solution surface is raised and this portion is brought into contact with one surface of the semiconductor wafer, the contacting etching solution can be favorably spread over the entire surface of the semiconductor wafer. Thereby, reliable and uniform one-sided etching can be performed. Moreover, since the semiconductor wafer is rotated during the one-sided etching, the spreading of the liquid over the entire surface of the semiconductor wafer is further improved.

Further, the outer peripheral portion of the other surface of the semiconductor wafer, which is not in direct contact with the etching solution, is etched (gas etched) by the etching vapor. The part can be etched.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an outline of an entire configuration of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the wafer holding means according to one embodiment of the present invention.

FIG. 3 is a perspective view schematically showing a drive system of the semiconductor wafer single-side etching apparatus according to one embodiment of the present invention.

FIG. 4 is a bottom view showing the wafer holding means according to one embodiment of the present invention.

[Description of Signs] 10 Single-sided etching apparatus for semiconductor wafer, 11 Etching tank, 12 Wafer holding means, 13 Wafer elevating means, 14 Blow-out nozzle, 19 Rotary motor (wafer rotating unit), 21 Wafer holder, W Silicon wafer (Semiconductor) Wafer), a gap for gas delivery. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 8, 2000 (200.9.8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Method and Apparatus for Single-Side Etching of Semiconductor Wafer

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for etching one side of a semiconductor wafer, and more particularly, to a method of etching one side of a semiconductor wafer mainly by bringing one side of the semiconductor wafer into contact with an etching solution. And a single-sided etching method.

[0002]

2. Description of the Related Art In a silicon wafer, for example, L
TO (Low Temperature Oxidat)
ion) specification, thermal oxide film specification, IG (In)
(trinsic gettering) specifications. In the LTO product, a low-temperature oxide film is applied to the etched wafer, and only the LTO film on the mirror-finished surface is removed by one-sided etching. Thereafter, an epitaxial layer is laminated on this mirror surface in an epitaxial step. In the thermal oxide film product, the etched wafer HW is covered with a thermal oxide film, and one-sided etching is performed to remove the thermal oxide film. The exposed silicon surface is mirror-polished. In the IG product, a thin thermal oxide film may be formed on the mirror-finished wafer PW after the IG processing, and the thermal oxide film on the mirror surface is removed by one-sided etching. As described above, in various silicon wafers, only one side is etched to remove an oxide film and the like. Conventionally, when etching one side of this silicon wafer, the side on the side to be etched, for example, the back side not mirrored in the LTO product, is covered with a film and immersed in an etchant to remove a low-temperature oxide film from the surface. I was That is, the conventional one-sided etching method is performed by dipping a wafer into an etching solution by applying a film.

[0003]

However, according to such prior art, the following problems have occurred. That is, (1) In the conventional one-sided etching, a film covering step of a non-etched surface of a silicon wafer and a step of removing a film after etching are required. as a result,
There has been a problem that the number of work steps increases and productivity decreases. This also leads to high costs. (2) Recently, in order to prevent the generation of nodules on the outer peripheral portion (chamfered surface) of the wafer during epitaxial growth of an LTO product, there has been an increasing demand that the entire outer peripheral portion be etched cleanly.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor wafer single-side etching method and apparatus which can reduce the number of single-side etching steps and thereby increase the productivity of semiconductor wafers. That is the purpose. Another object of the present invention is to provide a method and an apparatus for single-sided etching of a semiconductor wafer which can perform reliable and uniform single-sided etching. Still another object of the present invention is to provide a method and apparatus for single-sided etching of a semiconductor wafer capable of simultaneously removing the backside oxide film of the semiconductor wafer and the oxide film on the outer peripheral portion (chamfered surface) of the semiconductor wafer without lowering the productivity. For that purpose.

[0005]

According to the first aspect of the present invention, an etching solution is blown out from below the surface of the etching solution to raise the liquid surface, and one side of the semiconductor wafer is brought into contact with the raised portion of the liquid surface. A method of etching a semiconductor wafer on one side, wherein when one side of the semiconductor wafer is in contact with an etching solution, vaporized from the etching solution is wrapped around the surface opposite to the one side of the semiconductor wafer. The other side of the outer peripheral portion of the semiconductor wafer is etched by the wrapped vapor,
This is a method for single-sided etching of a semiconductor wafer in which an inert gas is blown out to the other side of the semiconductor wafer to control the amount of the vapor wraparound. Examples of the semiconductor wafer include a silicon wafer and a gallium arsenide wafer. An oxide film or the like may or may not be provided on one surface of the semiconductor wafer. Further, the etchant is not limited. For example, HF,
HF: NH ₄ F and the like.

[0006] The etching rate is not limited. For example, 5
000-18000 Angstroms / min. The preferred etch rate is 6000-8000 Å / min. If it is less than 5000 Å / min, uneven etching may occur, for example, an oxide film may remain on the outer peripheral portion of the wafer. On the other hand, if it exceeds 18000 angstroms / minute, the disadvantage of over-etching occurs.

During one-sided etching, the semiconductor wafer may or may not rotate about the center point of the semiconductor wafer. However, rotation is preferable because the etchant can be uniformly brought into contact with one surface of the semiconductor wafer. The time required for single-sided etching varies depending on the type of the etching product, the concentration of the etching solution, and the like. For example, for 30 to 250 seconds. The temperature of the etching solution during the etching is not limited. For example, 25-4
The temperature is 5 ° C, preferably 34 to 36 ° C. If the temperature is lower than 25 ° C., the rate is low, and there is a disadvantage that an oxide film may remain. If the temperature exceeds 45 ° C., the composition is changed, and there arises an inconvenience that an oxide film remains or overetch occurs. In addition,
During this one-sided etching, the semiconductor wafer may be swung (translated in the horizontal direction). When swinging, the amount of wafer swing is 80 to 160 mm, preferably 110 to 13 mm.
0 mm. If it is less than 80 mm, uneven etching occurs, and if it exceeds 160 mm, there is a problem that overetching is caused. Due to this swing, an effect is obtained that etching can be performed more uniformly than when only rotation is performed.

When the etching liquid is blown out from below the liquid surface of the etching liquid, the liquid surface is raised, and when the one surface of the rotating semiconductor wafer is brought into contact with the raised portion of the liquid surface, the blowing direction of the etching liquid is blown. The direction is not limited as long as the liquid surface can be raised by the etchant. Usually, it is the direction toward the liquid surface. The flow rate of the etching solution is not limited as long as the level of the solution can be raised by the blown etching solution. Note that the blown-out etchant may not be a complete etchant, but may be, for example, a component constituting a part of the solution.

The contact position of the raised portion on one side of the wafer is not limited. For example, it may be a central portion on one side of the semiconductor wafer or an outer peripheral portion of the semiconductor wafer. This is because the surface of the contacted etching solution spreads over one surface of the semiconductor wafer due to the surface tension of the etching solution. In addition, since the semiconductor wafer rotates at a predetermined rotation speed, the spread of the semiconductor wafer over the entire area of one surface is further improved. However, it is preferable to arrange the center position of the raised portion at the center of the semiconductor wafer because it prevents the etchant from flowing to the back surface (the other surface) of the semiconductor wafer and allows the semiconductor wafer to rotate stably. The rotation speed of the semiconductor wafer is not limited. Usually 1 to 1
0 rpm. A large amount of vapor of the etching liquid is generated from the liquid surface of the etching liquid including the raised part.
Using this vapor, the chamfered surface and the other surface of the outer peripheral portion of the semiconductor wafer are etched. Further, the wraparound amount is controlled by blowing out an inert gas. As a result, it is possible to control the etching range (distance inward in the radial direction from the outer peripheral edge) of the other surface of the semiconductor wafer. The range of the other surface of the semiconductor wafer to be etched by the wraparound of the vapor can be arbitrarily controlled.

According to a second aspect of the present invention, there is provided the method for etching a single side of a semiconductor wafer according to the first aspect, wherein one side of the semiconductor wafer has an oxide film.

According to a third aspect of the present invention, there is provided an etching tank in which an etching solution is stored, a wafer holding means disposed above the etching tank to hold a semiconductor wafer, and a surface of the held semiconductor wafer. In a horizontal state, the semiconductor wafer single-side etching apparatus is provided with a wafer elevating means capable of lowering the semiconductor wafer to a position where one side of the semiconductor wafer can contact the etching liquid surface in the etching bath. The wafer holding means has a wafer holder that adsorbs a central portion of a surface opposite to one surface of the semiconductor wafer, and a flange is provided outside the wafer holder in a radial direction of the semiconductor wafer. The part sends out an inert gas between the suction side surface of the semiconductor wafer and the outer peripheral side of the suction side surface of the semiconductor wafer. To form a scan delivery for clearance,
By arranging the outer edge of the semiconductor wafer radially outside of the gas delivery gap and adjusting the amount of inert gas blown out from the gas delivery gap to the other surface of the outer peripheral portion of the semiconductor wafer. A single-side etching apparatus for a semiconductor wafer in which the amount of vaporized vapor from an etching solution flowing to the other side of the outer peripheral portion of the semiconductor wafer is controlled.

The type of holding the semiconductor wafer by the wafer holding means is not limited. For example, the semiconductor wafer may be suction-held by suction. The wafer elevating means may be any mechanism that can elevate the semiconductor wafer while keeping the semiconductor wafer horizontal. Raising and lowering the surface of the semiconductor wafer horizontally means, in other words, raising and lowering the semiconductor wafer while keeping the semiconductor wafer parallel to the liquid level of the etching solution in a stationary state. The shape of the wafer holder may be, for example, a plate shape or a block shape. For example, a suction hole connected to an external air suction device may be formed on the contact surface of the semiconductor wafer.

As the inert gas, for example, N ₂ gas or the like is used. The flange portion here is for forming a gas sending gap for sending out the inert gas to the outer peripheral side of the suction side surface of the semiconductor wafer. By sending the inert gas to the outer peripheral portion of the semiconductor wafer, it is possible to control the amount of the vapor flowing toward the center of the semiconductor wafer beyond the outer peripheral portion of the surface of the semiconductor wafer on the suction side.
For example, it is possible to prevent the wraparound. Since the gas sending gap is located radially inward of the outer edge of the semiconductor wafer, the control is easy.
A gas supply port for supplying an inert gas to the gas delivery gap may be provided in this flange portion, or may be provided in the wafer holder. When provided on the flange, for example, the flange may be attached to the wafer holder so as to be freely rotatable, and a gas supply pipe extending from an inert gas supply device may be connected to the gas supply port.

According to a fourth aspect of the present invention, the distance between the gas delivery gap and the outer edge of the semiconductor wafer is 1 to 20 mm,
4. The single-side etching apparatus for a semiconductor wafer according to claim 3, wherein the width of the gas delivery gap is 1 to 20 mm, and the amount of the inert gas blown out from the gas delivery gap is 5 to 80 liter / minute.

According to a fifth aspect of the present invention, a blow nozzle for blowing an etchant to raise the level of the etchant is provided in the etching bath, and the wafer elevating means rotates the semiconductor wafer while holding the semiconductor wafer horizontally. A single-sided etching apparatus for a semiconductor wafer according to claim 3 or 4, further comprising a wafer rotating unit for causing the wafer to rotate. The installation position of the etching solution blowing nozzle is not limited as long as it is below the liquid level in the etching tank. That is,
Not only the lower part or the center part of the etching bath but also the vicinity of the liquid level may be used. The structure of the wafer rotating unit is not limited.
It is sufficient that the semiconductor wafer can be horizontally rotated at a predetermined speed by a driving source such as a motor.

[0016]

According to the present invention, since one surface of a semiconductor wafer is brought into contact with the surface of an etching solution and only one surface of the semiconductor wafer is etched, a time-consuming film required in conventional one-side etching. Therefore, the step of coating the surface on the opposite side of the semiconductor wafer and the step of removing the film after etching become unnecessary. As a result, the number of steps of one-sided etching of the semiconductor wafer can be reduced, and thereby the productivity of the one-sided etching of the semiconductor wafer can be increased.

In particular, the liquid surface is raised by blowing out the etching liquid from below the liquid surface of the etching liquid, and one surface of the rotating semiconductor wafer is brought into contact with the raised portion of the liquid surface. At this time, even if the contact portion is a part of one surface of the semiconductor wafer, the etching solution spreads favorably over the entire surface of the semiconductor wafer due to the surface tension of the etching solution. This makes it possible to perform reliable and uniform one-sided etching. Moreover, since the semiconductor wafer is rotating, the spread of the etchant over one surface of the semiconductor wafer is further improved.

A highly volatile etching component (for example, HF) is constantly vaporized from the etching liquid surface. Therefore, during this one-sided etching, the vapor is made to flow to the other side of the semiconductor wafer. In this way, the escaping vapor is brought into contact with the outer peripheral portion of the other surface of the semiconductor wafer which is not in contact with the etchant. As a result, etching of the chamfered portion and the outer peripheral edge of the other surface can be performed by the vapor.
Therefore, it is possible to perform etching on one surface of the semiconductor wafer and a portion near the outer peripheral portion thereof without lowering the productivity.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, for convenience of explanation, the X direction is the apparatus length direction, the Y direction is the apparatus width direction, and the Z direction is the up and down direction. FIG. 1 is a schematic configuration diagram of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention. FIG. 2 is an enlarged sectional view of a main part of the wafer holding means during one-sided etching according to one embodiment of the present invention. FIG.
FIG. 1 is a perspective view schematically showing a drive system of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention. FIG. 4 is a bottom view showing the wafer holding means according to one embodiment of the present invention.

In these figures, reference numeral 10 denotes a single-sided etching apparatus for a semiconductor wafer (hereinafter referred to as a single-sided etching apparatus 1).
0), and the etching apparatus 10 is set in the booth 102. This single-sided etching apparatus 10
An etching bath 11, a wafer holding unit 12, and a wafer elevating unit 13 are provided. A spin dryer 103 for drying a wafer is provided in the booth 102 adjacent to the etching tank 11. An etching solution (HF: NH ₄ F = 25: 12) is stored in the etching tank 11 up to the upper part of the tank. Wafer holding means 12
Is disposed above the etching tank 11 and can horizontally hold, for example, a silicon wafer W having a thickness of 625 μm and a diameter of 6 inches. Wafer elevating means 13
Is provided in the wafer holding means 12 to raise and lower the silicon wafer W while keeping the surface of the wafer horizontal. The front and back surfaces of the silicon wafer W are covered with an oxide film having a predetermined thickness. This etching tank 11
Is composed of a separated inner tank 11A and outer tank 11B. At the center of the bottom surface of the inner tank 11A, there is provided a blowing nozzle 14 that blows out the etching liquid just above and raises the liquid surface to a predetermined height. Spout nozzle 1
4, an etching solution overflowing from the inner tank 11A and discharged to the outer tank 11B is led out via the circulation pipe 15a, filtered and returned from the blowing nozzle 14 into the inner tank 11A. Liquid circulation device 1
5 is connected.

A flow meter 15C, a circulation pump 16, and a filter 17 are connected to the circulation pipe 15a in order from the upstream side. Further, a filter can be interposed in the middle of the circulation pipe 15a. The circulating pump 16 blows out the etching solution from the nozzle 14 to a position of 0.1 mm.
It is a pump that can blow out at 5 to 5.0 liters / minute. Further, in order to keep the etching liquid at a constant temperature, an etching liquid temperature controller 100 is provided in the etching bath 11. The etching solution discharged from the outer tank 11B is circulated to the outer tank 11B via the temperature control device 100 and supplied. The temperature control device 100 has a temperature control coil 101 disposed close to the etching liquid pipe. The etching solution is adjusted to a constant temperature by causing heat exchange between the temperature control coil 101 and the etching solution.

Next, the wafer holding means 12 and the wafer elevating means 13 will be described in detail with reference to FIGS. First, the wafer elevating means 13 will be described. The wafer elevating means 13 includes a vertical rotating shaft 18 and the rotating shaft 18.
Arm 19 that rotatably supports the front end of the arm, and a traveling body 40 that supports the base end of the horizontal arm 19 so as to be vertically movable.
And The traveling body 40 can travel in the longitudinal direction of the booth 102, and transfers the wafer between the etching tank 11 and the spin dryer 103. The horizontal arm 19 is supported by a traveling body 40 so as to be able to move up and down, and a motor for driving and rotating the rotating shaft 18 and the like are built therein. That is, the configuration is such that the silicon wafer W is horizontally rotated at a predetermined rotation speed by this motor. The lower end of the rotation shaft 18 is connected to the wafer holding means 12. The wafer holding means 12 includes a disk-shaped wafer holder 21 provided at the lower end of the rotating shaft 18.
And a block body 22 extrapolated to the rotating shaft 18, and a flange 23 fixed to the lower end surface of the block body 22. The flange portion 23 has a gas sending gap a for sending N ₂ gas (inert gas) to the outer peripheral side of the back surface of the wafer between the upper surface of the silicon wafer W and the outer surface of the silicon wafer W outside the wafer holder 21 in the wafer radial direction. Is formed.

The wafer holder 21 is a thick disk.
On its lower surface, a plurality of suction holes 21b for sucking the center of the other surface (upper surface) opposite to one surface of the silicon wafer W are formed. The suction hole 21b communicates with an external negative pressure generating device via a suction hole 19b formed in each axis of the rotary shaft 18. Therefore, the silicon wafer W is sucked and held on the lower surface of the wafer holder 21 by the negative pressure generated by the operation of the negative pressure generator. The block body 22 is a cylindrical body having an opening at the lower end. And an annular plate 22c connecting the upper ends of the two.

The inner cylindrical portion 22a is fixed to the upper surface of the wafer holder 21 via a liner 24. In addition, the annular plate 22c has N
A plurality of gas holes for supplying _two gases are perforated. Gas can be supplied from the gas pipe 50 to this gas hole. That is, the gas pipe 50 is connected to and connected to the gas hole by the plurality of branch pipes 52 via the annular pipe portion 51 provided above the block body 22. Therefore, gas pipes 50 from the N ₂ gas supply source, the pipe section 51, N ₂ gas is supplied into the inner space via the branch pipe 52. The supply of the N ₂ gas is controlled by a control means (not shown). This internal space communicates with the gas delivery gap a, and N ₂ gas is supplied to the gas holes. The block body 22 is externally inserted by a set nut screwed to an external screw of the rotary shaft 18 without rattling in the axial direction of the shaft. On the other hand, the flange portion 23 is detachably fixed to the block body 22 via an embedding pin 26.
The gas sending gap a formed between the lower surface (one surface) of the flange portion 23 and the upper surface (the other surface) of the silicon wafer W adsorbed on the wafer holder 21 is, for example, 1 to 20 m.
m. The flange 23 has a length b of 1 to 20 mm from which the outer peripheral portion of the silicon wafer W protrudes.
It is designed to be.

Next, a single-sided etching method using the single-sided etching apparatus 10 according to one embodiment of the present invention will be described. As shown in FIGS. 1 and 2, first, the silicon wafer W is sucked and held on one surface of the wafer holder 21 by the negative pressure generated by the operation of the negative pressure generator. Thereafter, while rotating the silicon wafer W at 1 to 10 rpm by a rotation motor, the rotating shaft 18 is made to protrude, and the silicon wafer W
Is inserted horizontally into the internal space of the etching bath 11 from the opening of the bath. At this time, the height of the stopped silicon wafer W from the etching liquid surface to the lower surface of the silicon wafer is, for example, 5 to 30 mm. The front and back surfaces of the silicon wafer W are covered with a thermal oxide film having a predetermined thickness.

Next, the circulation pump 16 is operated to move 5 to 3 from the blowing nozzle 14 toward the etching liquid surface.
Blow out the etchant at 0 liter / min. As a result, the liquid level at the center of the etching liquid stored in the inner cylindrical portion 11A rises by 5 to 30 mm. Therefore, the raised portion comes into contact with the center of one surface on the mirror-finished side of the silicon wafer W horizontally held above the liquid surface. At this time, due to the surface tension of the etchant, the etchant spreads over one surface of the silicon wafer and then drops.
Thereby, the oxide film on one side of the silicon wafer W
It is reliably and uniformly removed. Moreover, the silicon wafer W is horizontally rotated by the rotation motor 19 during the one-sided etching. Therefore, the spread of the etching solution over the entire single-sided oxide film of the silicon wafer is further improved.
As a result, the effect of removing the oxide film on one side of the wafer is enhanced.

A highly volatile etching component is constantly vaporized from the etching solution level in the etching tank 11. After contacting one side of the silicon wafer W,
The same applies to the case of an etching solution that spreads in the wafer radial direction due to surface tension and falls. As a result, as shown in the partial enlarged view of FIG. 2, the vapor (etching vapor) volatilized from the liquid surface of the etching liquid flows to the other surface side of the silicon wafer W. The oxide film Wa covering the outer peripheral portion of the silicon wafer W is removed by the wrapped vapor. Thus, the oxide film in the chamfered portion can be etched simultaneously with the one-sided etching without lowering the productivity. Part of the steam that has flowed in tries to flow into the internal space of the block body 22 from the gas delivery gap a. However, during this one-sided etching, the N ₂ gas supplied from the gas holes constantly flows out of the gas delivery gap a at a rate of 5 to 80 L / min. Therefore, the excessive wraparound of the vapor containing the etching component toward the central portion of the wafer is prevented. as a result,
Oxide film Wa on the other surface of the wafer, except for the outer peripheral portion of the wafer,
It remains after one-sided etching. In this case, by adjusting the blowing amount of the N ₂ gas, it is possible to adjust the amount of the vapor flowing into the other surface (front surface) of the wafer.
The amount of etching of the outer edge portion of the oxide film on the wafer surface side can be adjusted as appropriate. Most of the generated steam is led out to the etching steam processing equipment.

As described above, since one side of the silicon wafer W is brought into contact with the liquid surface of the etching solution to etch the one side of the wafer, the wafer by a complicated film which is required at the time of the conventional one side etching. Both the step of coating the other surface and the step of removing the film after etching become unnecessary. As a result, the number of single-side etching steps of the silicon wafer W can be reduced. Therefore, the productivity of the silicon wafer W can be improved. In addition, the gap a for gas delivery is 0.2 to 2.0 m.
m, the length b of the wafer outer peripheral portion from the tip end of the flange portion 23 projects is designed to be 0 to 5 mm, using 5 to 80 liters / min feed amount of N ₂ gas, the wafer outer peripheral portion Only the oxide film Wa can be satisfactorily removed. In this embodiment, an example is shown in which the N ₂ gas is discharged from the gas delivery gap a, but the present invention is not limited to this. That is, the external discharge of the N ₂ gas does not necessarily have to be performed.

[0029]

According to the present invention, since one surface of the semiconductor wafer is etched by bringing one surface of the semiconductor wafer into contact with the liquid surface of the etching solution, the total number of steps of one-side etching is reduced, and the productivity of the semiconductor wafer is reduced. Enhanced. This is because the efficiency in the single-sided etching step can be increased as compared with the conventional case. In addition, the cost required for one-sided etching can be reduced as a whole as compared with the related art.

In particular, since the etching solution surface is raised and this portion is brought into contact with one surface of the semiconductor wafer, the contacting etching solution can be favorably spread over one surface of the semiconductor wafer. Thereby, reliable and uniform one-sided etching can be performed. Moreover, since the semiconductor wafer is rotated during the one-sided etching, the spreading of the liquid over the entire surface of the semiconductor wafer is further improved.

Further, the outer peripheral portion of the other surface of the semiconductor wafer, which is not in direct contact with the etching solution, is etched (gas etched) by the etching vapor. The part can be etched.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an outline of an entire configuration of a single-sided etching apparatus for a semiconductor wafer according to one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the wafer holding means according to one embodiment of the present invention.

FIG. 3 is a perspective view schematically showing a drive system of the semiconductor wafer single-side etching apparatus according to one embodiment of the present invention.

FIG. 4 is a bottom view showing the wafer holding means according to one embodiment of the present invention.

[Description of Signs] 10 Single-sided etching apparatus for semiconductor wafer, 11 Etching tank, 12 Wafer holding means, 13 Wafer elevating means, 14 Blow-out nozzle, 19 Rotary motor (wafer rotating unit), 21 Wafer holder, W Silicon wafer (Semiconductor) Wafer), a gap for gas delivery.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoki Muraki 1-5-1, Otemachi, Chiyoda-ku, Tokyo Within Mitsubishi Materials Silicon Co., Ltd. (72) Inventor Tsuneo Yoshikawa 1-5, Otemachi, Chiyoda-ku, Tokyo No. 1 F-term in Mitsubishi Materials Silicon Corporation (reference) 5F031 CA02 GA24 GA26 MA22 MA24 NA04 5F043 AA02 BB22 EE07 EE08 EE24

Claims (7)

[Claims] 2. A method for etching a semiconductor wafer, comprising the steps of: contacting one surface of a semiconductor wafer with a liquid surface of an etchant to etch the one surface of the semiconductor wafer; 2. The method according to claim 1, wherein the etching liquid is blown from below the liquid surface of the etching liquid to raise the liquid surface, and the raised surface of the liquid surface is brought into contact with one surface of the semiconductor wafer. 3. During the one-sided etching, vaporized from an etching solution surface is wrapped around the surface of the semiconductor wafer opposite to the one side, and the wraparound vapor causes
3. The method for etching one side of a semiconductor wafer according to claim 1, wherein the other side of the outer peripheral portion of the semiconductor wafer is etched. 4. The method for etching a single side of a semiconductor wafer according to claim 1, wherein one side of the semiconductor wafer has an oxide film. 5. An etching tank for storing an etching solution, a wafer holding means disposed above the etching tank for holding a semiconductor wafer, and provided on the wafer holding means for horizontally holding a surface of the semiconductor wafer. A semiconductor wafer single-side etching apparatus comprising: a wafer elevating means capable of lowering the semiconductor wafer to a position where one surface of the semiconductor wafer can come in contact with the etching liquid surface in the etching tank while maintaining the state. 6. A blowing nozzle for blowing out an etching solution to raise the level of the etching solution in the etching bath, and a wafer rotating unit for rotating the semiconductor wafer while horizontally holding the semiconductor wafer is provided in the wafer elevating means. Claim 5
2. The single-sided etching apparatus for a semiconductor wafer according to claim 1. 7. The semiconductor device according to claim 1, wherein the wafer holding means has a wafer holding member for adsorbing a central portion of a surface opposite to one surface of the semiconductor wafer. 7. A flange portion which forms a gas sending gap for sending out an inert gas to an outer peripheral side of the suction side surface of the semiconductor wafer is provided between the suction side surface of the semiconductor wafer and the wafer side. A single-sided etching apparatus for a semiconductor wafer as described in the above.