JPH0945642A - Method and device for grinding semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the nonuniformity of polishing caused by the floating of a semiconductor substrate by accurately measuring and detecting the floating of such semiconductor substrate as a wafer from the polishing surface of a polishing pad and controlling the horizontal state of the semiconductor substrate according to the floating height. SOLUTION: A polishing device 10A has a flat polishing surface 11A and consists of a rotary polishing pad 11, a holder 13 for pressing a retained semiconductor substrate 7 to the polishing surface 11A while rotating it around a rotary axis 12, a nozzle 15 for supplying a polishing liquid L between the semiconductor substrate retained at the holder and the polishing surface of a polishing pad, and a pressing device 20 which is located between the rotary axis 12 and the nozzle 15 and can apply press force to the semiconductor substrate 7 from the upper part. In addition, it has a floating height measuring device of the semiconductor substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer on which a plurality of semiconductor integrated circuit devices are formed and a bonding S.
The present invention relates to a method for polishing a semiconductor substrate such as an OI (Silicon on Insulator) substrate and its apparatus.

[0002]

2. Description of the Related Art Development of a VLSI using a so-called SOI substrate in which a thin film single crystal silicon layer is formed on the surface of an insulator is under development. Among the various SOI substrate manufacturing methods, the one that is considered to have the best crystallinity and the excellent characteristics is the bonding method of the SOI substrate. The steps of the method for manufacturing the SOI substrate are shown in FIG.
It was shown to. A method of manufacturing this SOI substrate will be briefly described with reference to FIG.

As shown in FIG. 5A, a predetermined pattern composed of a plurality of concave and convex portions 2 is formed on the surface of an element formation substrate 1 which is a single crystal silicon wafer having a mirror finished surface by using a photolithography technique. It is formed by steps. An upper insulating film 3A and a lower insulating film 3 are formed on these uneven portions 2.
An insulating film 3 formed continuously with B, for example, Si
An O ₂ film is formed, a flattening layer, for example, a polycrystalline silicon layer 4 is formed on the entire surface to further fill the step, and the surface of the polycrystalline silicon layer 4 is flatly polished.

Next, as shown in FIG. 5B, a support substrate 5 of, for example, another mirror-finished silicon wafer is attached to the flattened surface of the polycrystalline silicon layer 4, and the support substrate is then attached. 5 is ground to a predetermined thickness, and a bonded substrate 7 is manufactured by bonding the element forming substrate 1 and the supporting substrate 5. Then, as shown in FIG. 5C,
The bonded substrate 7 of FIG. 5B is turned upside down, and the upper insulating film 3B in the insulating film 3 (lower insulating film 3B in FIG. 5B).
Is used as a polishing stopper to polish the element forming substrate 1, which is a single crystal silicon wafer, from the back surface thereof, and to obtain a bonded SOI substrate 8 having a plurality of island-shaped silicon thin layers 6 separated by the insulating film 3 of SiO _2. It has gained.

By the way, in the manufacturing process of the bonded SOI substrate 8, the bonded substrate 7 is polished after the supporting substrate 5 is bonded, and the island-shaped silicon thin layer 6 in the recess of the SiO ₂ film is recessed. It depends on whether the surface of the peripheral SiO ₂ film is flush with the upper insulating film 3B and is flat and free from polishing damage.

In the conventional polishing process, the bonded substrate 7 is polished by using the polishing apparatus 10 as shown in FIG. That is, the polishing apparatus 10 has a flat polishing surface 11A and rotates at a predetermined rotation speed.
1 and a bonded substrate 7 which is a semiconductor substrate to be polished on a flat surface parallel to the polishing surface 11A of the polishing pad 11, and the element forming substrate 1 side of the bonded substrate 7 faces the polishing surface 11A. And a holder 13 capable of pressing the bonded substrate 7 against the polishing surface 11A while rotating the bonded substrate 7 held in the state of being held around the rotational shaft 12 at the same time. Located on the side of the holder 13 and the polishing pad 11, the holder 13
The polishing liquid supply device (not shown) is provided with a nozzle 15 for supplying the polishing liquid L between the bonded substrate 7 held on the substrate and the polishing surface 11A of the polishing pad 11.
Reference numeral 14 is a universal joint, and the pressure is transmitted to the bonded substrate stack 7 via the universal joint 14.

In the case of polishing the element forming substrate 1 of the bonded substrate stack 7 using the polishing apparatus 10 having such a structure, first, the bonded substrate stack 7 is mounted on the holder 13, and then the polishing pad 11 is mounted. Are rotated at a predetermined rotation speed, and the polishing pad 11 is simultaneously lowered while rotating about the rotating shaft 12, and the polishing surface 11A of the polishing pad 11 is brought into close contact with the polishing surface 11A while applying a predetermined pressing force F to the polishing surface. When the polishing liquid L is constantly jetted and supplied from the nozzle 15 of the polishing liquid supply device between 11A and the surface to be polished of the element formation substrate 1, the surface of the element formation substrate 1 of the bonded substrate 7 can be polished. it can.

[0008]

However, at the time of the above-mentioned polishing, the polishing surface 11A from the nozzle 15 of the polishing liquid supply device is removed.
The polishing liquid L is sprayed between the polishing surface of the element forming substrate 1 and the surface to be polished of the element forming substrate 1,
When supplied, due to the dynamic pressure of the polishing liquid L and the sinking action of the polishing pad 11, the film thickness of the polishing liquid L is different on the outlet side opposite to the inlet side where the polishing liquid L is jetted and supplied. In general, the film thickness of the polishing liquid L becomes thicker on the inlet side, sinks on the outlet side, and the bonded substrate 7 floats as shown by the arrow A in FIG. 6, and the bonded substrate 7 tilts due to this floating. The floating or sinking depending on the location of the bonded substrate 7 changes depending on the polishing conditions such as the number of rotations of the polishing pad 11, the supply amount of the polishing liquid L, the viscosity of the polishing liquid L, and the polishing pressure. This causes unevenness in polishing due to the polished state, which is a factor of deteriorating the in-plane uniformity of the surface to be polished of the element forming substrate 1.

Normally, such non-uniform polishing is carried out, and the bonded substrate 7 is rotated as described above in order to correct this non-uniformity to some extent. However, it was not sufficient to compensate for the non-uniformity, which was an insufficient polishing method. Further, by accurately measuring and detecting the flying height of the bonded substrate 7,
No measures have been taken to suppress this surfacing. Therefore, the present invention accurately measures and detects the levitation of a semiconductor substrate that is a bonded substrate, controls the horizontal state of the semiconductor substrate according to the levitation height, and eliminates the unevenness of polishing due to the levitation of the semiconductor substrate. It is intended to be removed.

[0010]

Therefore, in the method of polishing a semiconductor substrate according to the present invention, a semiconductor substrate and a polishing pad having a flat polishing surface and being pressed against a rotating polishing pad while rotating the semiconductor substrate are used. In polishing the thickness of the semiconductor substrate while supplying a polishing liquid from the side between and, the semiconductor substrate detects the flying height from the polishing surface of the polishing pad, and responds to the flying height. The problem is solved by applying a pressing force at a position deviated from the central axis of rotation of the semiconductor substrate to the supply side of the polishing liquid while applying the polishing force to the polishing surface of the polishing pad from above the semiconductor substrate. did.

Further, as a polishing apparatus capable of executing the above polishing method, a polishing pad having a flat polishing surface, which is rotatable, and a semiconductor substrate to be polished are held on a plane parallel to the polishing surface of the polishing pad, A holder that can pressurize the held semiconductor substrate against the polishing surface while rotating it around a rotation axis, and a semiconductor substrate and a polishing pad that are lateral to the holder and the polishing pad and are held by the holder. A polishing liquid supply device for supplying a polishing liquid between the surface and the surface, and a semiconductor substrate held between the rotary shaft of the holder and the polishing liquid supply device and held by the holder, a pressing force is applied from above the semiconductor substrate. And a flying height measuring device for measuring the flying height of the semiconductor substrate and instructing the pushing device to output a pressing force corresponding to the flying height. And solve the above mentioned problems.

Therefore, according to the method for polishing a semiconductor substrate and the apparatus for polishing the semiconductor substrate of the present invention, the flying height is detected and the pressure is applied according to the height, so that the semiconductor substrate is uniformly polished in the plane with high accuracy. Can be finished.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, with reference to the drawings, a semiconductor substrate polishing method and apparatus of the present invention will be described. FIG.
3 is a schematic sectional view of a semiconductor substrate polishing apparatus according to a first embodiment of the present invention, and FIG. 2 is a schematic sectional view of a semiconductor substrate polishing apparatus according to a second embodiment of the present invention, and FIG. FIG. 4 is a plan view of a semiconductor substrate flying height measuring apparatus that can be used in the semiconductor substrate polishing apparatus of the present invention, and FIG. 4 is a schematic sectional view taken along the line AA of FIG. The same components as those of the conventional semiconductor substrate polishing apparatus are designated by the same reference numerals.

In FIG. 1, reference numeral 10A is the first of the present invention.
The polishing apparatus for a semiconductor substrate (hereinafter, simply abbreviated as “polishing apparatus”), which is the embodiment of FIG. This polishing apparatus 10A is
A polishing pad 11 having a flat polishing surface 11A and rotating at a predetermined rotation speed, and the polishing surface 1 of the polishing pad 11.
The bonded substrate stack 7 which is a semiconductor substrate to be polished on a plane parallel to 1A is held with the element forming substrate 1 side of the bonded substrate 7 facing the polishing surface 11A, and the bonded substrate stack 7 is held. A holder 13 that can press the bonded substrate 7 against the polishing surface 11A while rotating the rotating shaft 12 about the rotating shaft 12 at the same time.
Beside the holder 13 and the polishing pad 11,
It is composed of a polishing liquid supply device (not shown) having a nozzle 15 for supplying the polishing liquid L between the bonded substrate stack 7 held by the holder 13 and the polishing surface 11A of the polishing pad 11, This is similar to the conventional polishing apparatus 10. Reference numeral 14 is a universal joint, and the pressure is transmitted to the bonded substrate stack 7 via the universal joint 14. The entire thickness of the holder 13 is dimensioned and processed very uniformly, and the entire upper surface of the holder 13 is finished into a highly accurate flat surface.

A pressing device 20 is provided between the rotary shaft 12 of the holder 13 and the nozzle 15.
The pressing device 20 includes a roller supporting device 21 that can move in the vertical direction of the arrow Y, and a roller 2 that is rotatably supported by a bearing 22 formed at the lower end of the roller supporting device 21.
And 3. The rotation axis of the roller 23 lies on a line perpendicular to the tangential direction of the rotating holder 13. Further, the roller 23 is configured to contact the upper surface of the holder 13 and apply a pressing force Fa parallel to the rotating shaft 12 to the holder, so that a pressing force can be applied from above the bonded substrate stack 7. Furthermore, this pressing device 2
0 is configured to be movable on the line in the diameter direction of the holder 13 indicated by the arrow X so that it can be pressed at an arbitrary position on the line connecting the center of the rotary shaft 12 of the holder 13 and the nozzle 15.

When polishing the element-formed substrate 1 of the bonded substrate stack 7 using the polishing apparatus 10A equipped with such a pressing device 20, first, the bonded substrate stack 7 is held by the holder 13.
Then, the polishing pad 11 is rotated at a predetermined rotation speed, and the polishing pad 11 is simultaneously lowered while rotating about the rotating shaft 12 so that a predetermined pressing force is applied to the polishing surface 11A of the polishing pad 11. While closely contacting with F, the polishing liquid L is constantly sprayed and supplied from the nozzle 15 of the polishing liquid supply device between the polishing surface 11A and the surface to be polished of the element forming substrate 1, and the pressing device 20 is also provided. Is lowered to bring the roller 23 into contact with the upper surface of the holder 13, and an auxiliary pressing force Fa capable of suppressing the floating is applied to the holder 13 and to the bonded substrate 7. Then, the surface to be polished of the element forming substrate 1 of the bonded substrate 7 is the polishing surface 11A of the polishing pad 11.
Since the surface contact can be made evenly, the surface to be polished of the element forming substrate 1 can be uniformly polished.

The main pressing force for pressing the bonded substrate 7 against the polishing surface 11A is the pressing force F by the rotating shaft 12 of the holder 13.
Therefore, the auxiliary pressing force Fa by the pressing device 20 may be a light pressure. Since the auxiliary pressing force Fa and the pressing position of the pressing device 20 differ depending on the rotation speed of the polishing pad 11 and the holder 13, the supply amount of the polishing liquid L, the viscosity of the polishing liquid L, the area of the bonded substrate 7, and the like. The setting of may be performed empirically. However, it is desirable to set by using a flying height measuring device for measuring and detecting the flying height which will be described later.

Next, a polishing apparatus 10B which is a second embodiment of the present invention will be described with reference to FIG. In the pressing device 20 of the polishing device 10A, the roller 23 has the holder 13
Although the auxiliary pressing force Fa is mechanically applied to the holder 13 at an arbitrary position on the upper surface of the holder, the pressing device 30 in the polishing apparatus 10B of this embodiment assists the holder 13 by a non-contact means. It is configured to apply a pressing force Fa. That is, the pressing device 30 of the polishing device 10B
Is a magnet supporting device 31, a magnet 32 mounted and fixed to the lower end thereof, a magnet supporting disk 33 mounted on the upper surface of the holder 13 and having a uniform thickness, and the magnet supporting disk 33. It is composed of a plurality of annular magnets 34 concentrically embedded in the upper surface of the outer peripheral portion of the magnet 32 so as to face the magnet 32 and have the same polarity as that of the magnet 32. This pressing device 3
0 also moves up and down in the direction of arrow Y, and in the diametrical direction of the holder 13 indicated by arrow X so that it can be pressed at any position on the line connecting the center of the rotary shaft 12 of the holder 13 and the nozzle 15. It is the same as the configuration of the pressing device 20 in that it is configured to be movable on a line.

When the element forming substrate 1 of the bonded substrate stack 7 is polished by using the polishing apparatus 10B equipped with the pressing device 30, the bonded substrate stack 7 is first held in the holder 13.
Then, the polishing pad 11 is rotated at a predetermined rotation speed, and the polishing pad 11 is simultaneously lowered while rotating about the rotating shaft 12 so that a predetermined pressing force is applied to the polishing surface 11A of the polishing pad 11. While being adhered while applying F, the polishing liquid L is constantly jetted and supplied from the nozzle 15 of the polishing liquid supply device between the polishing surface 11A and the surface to be polished of the element forming substrate 1 and the pressing device 30. Lower the magnet 3
2 and the annular magnet 34 are brought close to each other and repelled. Then, the auxiliary pressing force Fa due to this repulsive force works downward,
Floating of the holder 13 and the bonded substrate stack 7 can be suppressed. Therefore, the surface to be polished of the element forming substrate 1 of the bonded substrate 7 can be brought into uniform surface contact with the polishing surface 11A of the polishing pad 11, so that the surface to be polished of the element forming substrate 1 can be uniformly polished. Therefore, the desired bonded SOI substrate 8 can be obtained.

In each of the above-mentioned embodiments, an embodiment is shown in which the auxiliary pressing force Fa is applied to the holder 13 so that the surface to be polished of the bonded substrate 7 becomes a plane parallel to the polishing surface 11A of the polishing pad 11. Depending on the polishing conditions, it may be possible to more uniformly polish by inclining in a specific direction from a plane parallel to the polishing surface 11A of the polishing pad 11,
In such a case, the auxiliary pressing force Fa of any of the pressing devices 20 and 30 can be used to intentionally incline the surface to be polished of the bonded substrate 7 in a specific direction.

Next, referring to FIGS. 3 and 4, a semiconductor substrate flying height measuring device (hereinafter simply referred to as “flying height measuring device”) 40 of the present invention will be described. In these figures, the pressing devices 20 and 30 and the polishing liquid supply device are omitted in order to simplify the drawings. The flying height measuring device 40 includes a bifurcated measuring element holder 41 having two tip portions and a base portion located in the peripheral portion of the bonded substrate 7 to be polished, and a tip portion of the bifurcated portion and a bifurcated base portion. When measuring the flying heights, the measuring elements 42 mounted and fixed to and, the control device (not shown) including a computer that measures the outputs of these measuring elements 42 and generates the required pressing force Fa, and Means to move the measuring element holder 41 from the non-measurement position outside the bonded substrate 7 to the measuring position above the bonded substrate 7, and after this measurement, the measuring element holder 4
1 is moved backward from the measurement position above the bonded substrate stack 7 to the non-measurement position outside the bonded substrate stack 7 (arrow 43).

Next, a method for measuring the flying height of the bonded substrate stack 7 using the flying height measuring device 40 having such a configuration will be described. First, the polishing pad 11 and the holder 13
The bonded substrate stack 7 is placed on the polishing pad 11 while the rotation of the is stopped. Next, the driving device 43 is operated, and the measuring element holder 41 is moved from the non-measurement position outside the bonded substrate stack 7 to the measurement position above the bonded substrate stack 7, and is set. In this set state, the outputs of the three measuring elements 42 are all reset to 0 μm at intervals between each measuring element 42 and the upper surface of the holder 13.

Next, with a prescribed amount of polishing liquid L being supplied,
After the polishing pad 11 and the holder 13 are steadily rotated and a prescribed pressing force F is applied to the bonded substrate 7 by the rotating shaft 12,
Again, the distance between each measuring element 42 and the upper surface of the holder 13 is measured. At this time, the distance from each measuring element 42 is normally displaced to + or − from the value of 0 μm. Therefore, it is necessary to make a correction so that the parallel plane is the same as that at the time of stop. For that purpose, the position of the bonded substrate stack 7 where this displacement amount has the same value at all three points is pressed and balanced.
That is, the output of each measuring element 42 is input to the control device, the arithmetic operation is performed, a control signal corresponding to the output of the measuring element 42 is generated, and the pressing force Fa corresponding to this control signal is shown in FIGS. 1 and 2. It is generated by the pressing device 20 and the floating portion of the bonded substrate 7 is pressed by this pressing force Fa.

When the pressing force Fa is constant as in the pressing device 30, the pressing device 30 is responsive to this control signal.
In the diametrical direction of the bonded substrate 7 indicated by the arrow X,
It is possible to control the bonded substrate 7 to be pressed by the pressing force Fa at the pressing position. This control can also be applied to the pressing device 20.

As the measuring element 42, any element capable of detecting a height change on the order of μm may be used, but a non-contact type detecting element is preferable. As such a measuring element 42, an optical micrometer using reflection of laser light or a capacitance sensor using change in capacitance is optimal. The former optical micrometer is KL130B manufactured by Anritsu Co., Ltd., and the latter capacitance sensor is manufactured by ADE.

As the polishing liquid L, it is preferable to use an alkaline polishing liquid containing almost no abrasive grains, such as ethylenediamine or ammonia, since it polishes the single crystal silicon layer of the element forming substrate 1.

In the above description, the bonded substrate 7 is exemplified as the semiconductor substrate, and the polishing apparatus for polishing the element forming substrate 1 and the polishing method using this polishing apparatus have been described. A single-plate silicon wafer on which a large number of ICs are formed can also be used, and the polishing apparatus of the present invention can be used when performing back surface polishing. It should be added that the semiconductor substrate is not limited to the semiconductor wafer.

[0028]

As described above, according to the semiconductor substrate polishing method and apparatus of the present invention, the in-plane uniformity of the semiconductor substrate, which is the plate to be polished, is improved, and the thin film can be highly accurately polished. Becomes Further, since the amount of displacement of the polishing state with respect to the reference surface can be quantified and quantified, various excellent effects can be obtained such as automation of automatic plane correction and the like.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a semiconductor substrate polishing apparatus that is a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a semiconductor substrate polishing apparatus that is a second embodiment of the present invention.

FIG. 3 is a plan view of a flying height measuring apparatus for a semiconductor substrate that can be used in the semiconductor substrate polishing apparatus of the present invention.

FIG. 4 is a schematic cross-sectional view taken along the line AA of FIG.

FIG. 5 is a manufacturing process diagram for describing a method for manufacturing a bonded SOI substrate according to a conventional technique.

FIG. 6 is a schematic sectional view of a conventional semiconductor substrate polishing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Element formation substrate 7 Laminated substrate 10A Polishing device which is the first embodiment of the present invention 10B Polishing device which is the second embodiment of the present invention 11 Polishing pad 11A Polishing surface 12 Rotating shaft 13 Holder 15 Nozzle 20 Pressing device 23 Roller 30 Pressing Device 32 Magnet 33 Magnet Support Disc 34 Magnet 40 Semiconductor Device Flying Height Measuring Device 41 Measuring Element Holder 42 Measuring Element 43 Driving Device L Polishing Liquid

Claims (8)

[Claims] 1. A semiconductor substrate having a flat polishing surface, the semiconductor substrate being pressed against a rotating polishing pad while being rotated, and a polishing liquid being supplied laterally between the semiconductor substrate and the polishing pad. When polishing the thickness of the semiconductor substrate, the semiconductor substrate is polished at a position deviated from the rotation center axis of the semiconductor substrate to the supply side of the polishing liquid while applying a pressing force to the polishing surface of the polishing pad from above. A method for polishing a semiconductor substrate, comprising: 2. A semiconductor substrate having a flat polishing surface, the semiconductor substrate being pressed against a rotating polishing pad while the semiconductor substrate is being rotated, and a polishing liquid being supplied laterally between the semiconductor substrate and the polishing pad. In polishing the thickness of the semiconductor substrate, the semiconductor substrate detects the flying height of the polishing pad from the polishing surface, and the semiconductor substrate is pressed with a pressing force corresponding to the flying height from above to the polishing surface of the polishing pad. A method of polishing a semiconductor substrate, which comprises polishing while pressing against. 3. A rotatable polishing pad having a flat polishing surface, a semiconductor substrate to be polished is held on a plane parallel to the polishing surface of the polishing pad, and the held semiconductor substrate is rotated about a rotation axis. A holder that can pressurize the polishing surface while performing polishing, and a polishing liquid that is located beside the holder and the polishing pad and that supplies a polishing liquid between the semiconductor substrate held by the holder and the polishing surface of the polishing pad. A liquid supply device, and a pressing device that is located between the rotary shaft of the holder and the polishing liquid supply device and that can apply a pressing force to the semiconductor substrate held by the holder from above. An apparatus for polishing a semiconductor substrate, characterized in that 4. A polishing pad having a flat polishing surface, which is rotatable, and a semiconductor substrate to be polished are held on a plane parallel to the polishing surface of the polishing pad, and the held semiconductor substrate is rotated about a rotation axis. A holder that can pressurize the polishing surface while performing polishing, and a polishing liquid that is located beside the holder and the polishing pad and that supplies a polishing liquid between the semiconductor substrate held by the holder and the polishing surface of the polishing pad. A liquid supply device, a pressing device that is between the rotary shaft of the holder and the polishing liquid supply device, and can apply a pressing force from above to the semiconductor substrate held by the holder; and the semiconductor substrate And a flying height measuring device for instructing the pressing device to output a pressing force corresponding to the flying height of the semiconductor substrate polishing device. . 5. The polishing apparatus for a semiconductor substrate according to claim 3, wherein the pressing device can change its pressing position in the radial direction of rotation of the holder. 6. The polishing apparatus for a semiconductor substrate according to claim 3, wherein the pressing device comprises a roller, and the roller is configured to press the upper surface of the holder. 7. The pressing device includes a magnet, and a magnet having the same polarity as the magnet is disposed on an upper surface of the holder at a position facing the magnet, and the repulsive force of the both magnets causes the semiconductor substrate to move. The polishing apparatus for a semiconductor substrate according to claim 3, wherein the polishing apparatus is configured to press the polishing pad. 8. A measuring element holder for holding a measuring element for measuring the flying height in a non-contact state at a plurality of points in a peripheral portion of a semiconductor substrate which rotates in a plane, and when measuring the flying height, From the non-measurement position outside the semiconductor substrate to the measurement position above the semiconductor substrate, and after the measurement is completed, move the measurement element holder from the measurement position above the semiconductor substrate to outside the semiconductor substrate. A flying height measuring device for a semiconductor substrate, comprising: a driving device for retracting to a non-measurement position.