JP7214318B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method for dividing a wafer, in which a plurality of devices are formed in respective regions of a surface partitioned by dividing lines, into individual device chips.

2. Description of the Related Art In the manufacturing process of device chips used in electronic devices such as mobile phones and personal computers, first, a plurality of intersecting dividing lines (streets) are set on the surface of a wafer made of a material such as a semiconductor. Then, devices such as ICs (Integrated Circuits), LSIs (Large-Scale Integrated circuits), LEDs (Light Emitting Diodes), etc. are formed in the regions defined by the division lines.

After that, an adhesive tape called a dicing tape, which is attached to an annular frame having an opening so as to close the opening, is attached to the back surface or front surface of the wafer, and the wafer, the adhesive tape, and the annular frame are integrated. form a frame unit. Then, by processing and dividing the wafer contained in the frame unit along the planned division lines, individual device chips are formed.

A laser processing apparatus, for example, is used to divide the wafer. A laser processing apparatus includes a chuck table that holds a wafer via an adhesive tape, and a laser processing unit that converges a laser beam having a wavelength that is transmissive to the wafer inside the wafer.

When dividing the wafer, the frame unit is placed on the chuck table, and the wafer is held by the chuck table via the adhesive tape. Then, the wafer is irradiated with the laser beam from the laser processing unit along each dividing line while the chuck table and the laser processing unit are relatively moved along the direction parallel to the upper surface of the chuck table. When the laser beam is focused inside the wafer, a modified layer that serves as a starting point for splitting is formed (see Patent Document 1).

After that, when the frame unit is carried out from the laser processing apparatus and the adhesive tape is expanded radially outward, the wafer is divided to form individual device chips. When picking up the formed device chip from the adhesive tape, the adhesive tape is previously subjected to treatment such as irradiation with ultraviolet rays to reduce the adhesive strength of the adhesive tape. As a processing apparatus with high production efficiency of device chips, there is known a processing apparatus that can continuously divide a wafer and irradiate an adhesive tape with ultraviolet rays (see Patent Document 2).

Japanese Patent No. 3408805 Japanese Patent No. 3076179

The adhesive tape includes, for example, a base layer made of a vinyl chloride sheet or the like, and an adhesive layer provided on the base layer. In a laser processing apparatus, a laser beam is condensed inside the wafer in order to form a modified layer that serves as a splitting starting point inside the wafer, but part of the leakage light of the laser beam reaches the glue layer of the adhesive tape. . Then, the adhesive layer of the adhesive tape melts due to the thermal effect of the laser beam irradiation, and part of the adhesive layer adheres to the back side or front side of the device chip formed from the wafer.

In this case, when the device chip is picked up from the adhesive tape, even if the adhesive tape is subjected to a treatment such as ultraviolet irradiation, the part of the adhesive layer remains on the back or front side of the picked-up device chip. end up Therefore, deterioration in the quality of the device chip becomes a problem.

The present invention has been made in view of such problems, and its object is to prevent the glue layer from adhering to the back or front side of the device chip to be formed, and to prevent the glue layer from adhering to the device chip. It is an object of the present invention to provide a wafer processing method that does not cause deterioration in quality.

According to one aspect of the present invention, there is provided a wafer processing method for dividing a wafer in which a plurality of devices are formed in respective regions of a front surface partitioned by dividing lines into individual device chips, the method comprising: a polyester-based sheet disposing step of disposing a polyester-based sheet on the surface; an integration step of heating the polyester-based sheet and integrating the wafer and the polyester-based sheet by thermocompression bonding; A first frame having an opening sized to accommodate the wafer and having a plurality of magnets, and a second frame having an opening sized to accommodate the wafer, before or after the hardening step. Using the frame, the outer peripheral portion of the polyester-based sheet is sandwiched between the first frame and the second frame by the magnetic force generated by the magnet, and the polyester-based sheet is attached to the frame and a frame supporting step of supporting the wafer by positioning a focal point of a laser beam having a wavelength that is transmissive to the wafer inside the wafer, and irradiating the wafer with the laser beam along the dividing line. A wafer characterized by comprising a dividing step of forming a modified layer on the wafer and dividing the wafer into individual device chips, and a picking up step of picking up the individual device chips from the polyester-based sheet. A processing method is provided.

Preferably, in the integration step, the thermocompression bonding is performed by infrared irradiation.

Preferably, in the pick-up step, the polyester sheet is expanded to widen the distance between the device chips, and the device chips are pushed up from the polyester sheet side.

Also preferably, the polyester sheet is either a polyethylene terephthalate sheet or a polyethylene naphthalate sheet.

Further preferably, in the integration step, the heating temperature is 250° C. to 270° C. when the polyester sheet is the polyethylene terephthalate sheet, and the heating temperature is 250° C. to 270° C. when the polyester sheet is the polyethylene naphthalate sheet. The temperature is between 160°C and 180°C.

Also preferably, the wafer is made of Si, GaN, GaAs, or glass.

In the wafer processing method according to one aspect of the present invention, the frame unit and the wafer are integrated using a polyester-based sheet having no adhesive layer without using an adhesive tape having an adhesive layer in the frame unit. An integration process for integrating the polyester sheet and the wafer is realized by thermocompression bonding.

A wafer processing method according to an aspect of the present invention comprises a first frame having an opening large enough to accommodate the wafer, and a second frame having an opening large enough to accommodate the wafer. frame is used. The first frame has a plurality of magnets, and the first frame and the second frame are attracted to each other by magnetic forces generated by the magnets.

Then, in the frame supporting step, a polyester sheet is arranged between the first frame and the second frame, and sandwiched between the first frame and the second frame to hold the polyester sheet. A polyester sheet can be supported by a frame.

That is, even if the polyester-based sheet does not have a glue layer, the wafer, the polyester-based sheet, and the frame can be integrated to form a frame unit by performing the integrating step and the frame supporting step. .

After that, the wafer is irradiated with a laser beam having a wavelength that is transmissive to the wafer, and a modified layer is formed inside the wafer along the lines to be divided, thereby dividing the wafer. After that, the device chip is picked up from the polyester sheet. Each of the picked-up device chips is mounted on a predetermined mounting target.

Leakage light of the laser beam reaches the polyester sheet when the modified layer is formed inside the wafer. However, since the polyester-based sheet does not have an adhesive layer, the adhesive layer does not melt and adhere to the back or front side of the device chip.

That is, according to one aspect of the present invention, since the frame unit can be formed using a polyester sheet that does not have a glue layer, an adhesive tape that has a glue layer is not required, and as a result, the device caused by the adhesion of the glue layer Chip quality does not deteriorate.

Therefore, according to one aspect of the present invention, there is provided a wafer processing method in which a glue layer does not adhere to the back or front side of the device chip to be formed, and quality deterioration resulting from the adherence of the glue layer to the device chip does not occur. be done.

FIG. 1A is a perspective view schematically showing the front surface of a wafer, and FIG. 1B is a perspective view schematically showing the rear surface of the wafer. FIG. 4 is a perspective view schematically showing how the wafer is positioned on the holding surface of the chuck table; It is a perspective view which shows typically a polyester-type sheet arrangement|positioning process. It is a perspective view which shows an example of an integration process typically. It is a perspective view which shows an example of an integration process typically. It is a perspective view which shows an example of an integration process typically. FIG. 7A is a perspective view schematically showing the frame supporting process, and FIG. 7B is a perspective view schematically showing the formed frame unit. FIG. 8A is a perspective view schematically showing the dividing step, and FIG. 8B is a cross-sectional view schematically showing the dividing step. FIG. 10 is a perspective view schematically showing loading of the frame unit into the pickup device; FIG. 10(A) is a cross-sectional view schematically showing the frame unit fixed on the frame support, and FIG. 10(B) is a cross-sectional view schematically showing the pickup process.

An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. First, a wafer to be processed by the wafer processing method according to the present embodiment will be described. 1A is a perspective view schematically showing the front surface of the wafer 1, and FIG. 1B is a perspective view schematically showing the rear surface of the wafer 1. FIG.

The wafer 1 is made of materials such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductors, or materials such as sapphire, glass, or quartz. It is a substantially disc-shaped substrate or the like made of. Examples of the glass include alkali glass, alkali-free glass, soda-lime glass, lead glass, borosilicate glass, and quartz glass.

The front surface 1a of the wafer 1 is partitioned by a plurality of dividing lines 3 arranged in a lattice. Further, devices 5 such as ICs, LSIs, and LEDs are formed in respective regions defined by dividing lines 3 on the front surface 1a of the wafer 1 . In the method for processing a wafer 1 according to the present embodiment, a modified layer is formed inside the wafer 1 along the dividing line 3, the wafer 1 is divided starting from the modified layer, and individual device chips are obtained. Form.

When forming the modified layer on the wafer 1, the wafer 1 is irradiated with a laser beam having a wavelength that is transmissive to the wafer 1 along the division line 3, and the laser beam is focused inside the wafer 1. light up At this time, the laser beam may be applied to the wafer 1 from the front surface 1a side shown in FIG. 1(A), or may be applied to the wafer 1 from the rear surface 1b side shown in FIG. 1(B). When irradiating the wafer 1 with a laser beam from the rear surface 1b side, an alignment means equipped with an infrared camera is used to transmit the wafer 1 and detect the planned dividing line 3 on the front surface 1a side. to irradiate the laser beam.

Before loading the wafer 1 into a laser processing apparatus 10 (see FIG. 8A) in which laser processing is performed to form a modified layer on the wafer 1, the wafer 1, the polyester-based sheet, and the frame are integrated. to form a frame unit. The wafer 1 is loaded into the laser processing apparatus 10 in the state of a frame unit and processed.

The wafer 1 can be divided by expanding the polyester sheet, and the individual device chips formed by dividing the wafer 1 are supported by the polyester sheet. After that, the polyester-based sheet is further expanded to widen the space between the device chips, and the device chips are picked up by a pick-up device.

The annular frame 7 (see FIGS. 7(A) and 7(B), etc.) is formed of a material such as metal, for example, and includes a first frame 7a having an opening 7b large enough to accommodate the wafer 1, and a first frame 7a. , a second frame 7 f having an opening 7 g large enough to accommodate the wafer 1 . For example, the first frame 7a and the second frame 7f have substantially the same shape.

The first frame 7a has a plurality of pins 7d on its upper surface 7c. A plurality of magnets 7e are embedded in the upper surface 7c of the first frame 7a. The second frame 7f is provided with a plurality of through holes 7i passing through in the thickness direction. The through holes of the second frame 7f are formed such that the pins 7d of the first frame 7a are fitted into the through holes 7i when the first frame 7a and the second frame 7f are superimposed on each other. 7i are formed in a number, position and size corresponding to the pins 7d of the first frame 7a.

The polyester-based sheet 9 (see FIG. 3, etc.) is a resin-based sheet having flexibility, and has flat front and back surfaces. The polyester-based sheet 9 has a diameter larger than that of the opening 7b of the first frame 7a and the opening 7g of the second frame 7f, which constitute the frame 7, and does not have a glue layer. The polyester-based sheet 9 is a polymer sheet synthesized using a dicarboxylic acid (a compound having two carboxyl groups) and a diol (a compound having two hydroxyl groups) as monomers, such as a polyethylene terephthalate sheet, or , polyethylene naphthalate sheet, etc., which are transparent or translucent to visible light. However, the polyester sheet 9 is not limited to this, and may be opaque.

The polyester-based sheet 9 cannot be adhered to the wafer 1 at room temperature because it does not have adhesiveness. However, since the polyester-based sheet 9 has thermoplasticity, it can be partially melted and adhered to the wafer 1 by heating to a temperature near the melting point while being bonded to the wafer 1 while applying a predetermined pressure.

In the method for processing the wafer 1 according to the present embodiment, the polyester sheet 9 is adhered to the back surface 1b side of the wafer 1 by thermocompression bonding, and the outer peripheral portion of the polyester sheet 9 is attached to the first frame 7a and the second frame 7f. , to form a frame unit.

Next, each step of the method for processing the wafer 1 according to this embodiment will be described. First, in preparation for integrating the wafer 1 and the polyester-based sheet 9, a polyester-based sheet disposing step is carried out. FIG. 2 is a perspective view schematically showing how the wafer 1 is positioned on the holding surface 2a of the chuck table 2. As shown in FIG. As shown in FIG. 2, the process of arranging the polyester-based sheet is performed on a chuck table 2 having a holding surface 2a on its top.

The chuck table 2 has a porous member with a diameter larger than the outer diameter of the wafer 1 in the upper center. The upper surface of the porous member serves as the holding surface 2a of the chuck table 2. As shown in FIG. As shown in FIG. 3, the chuck table 2 has therein an exhaust path, one end of which communicates with the porous member, and a suction source 2b is arranged on the other end of the exhaust path. The exhaust path is provided with a switching portion 2c for switching between a connected state and a disconnected state. Pressure is applied, and the object to be held is held by suction on the chuck table 2 .

In the process of arranging the polyester sheet, first, the wafer 1 is placed on the holding surface 2a of the chuck table 2, as shown in FIG. At this time, the orientation of the wafer 1 is selected in consideration of which of the front surface 1a and the back surface 1b is to be irradiated with the laser beam in the dividing step described later. For example, when the surface to be irradiated is the surface 1a, the surface 1a side faces downward. Further, for example, when the surface to be irradiated is the back surface 1b, the back surface 1b side is directed downward. Hereinafter, the wafer processing method according to the present embodiment will be described by taking as an example the case where the surface to be irradiated with the laser beam is the surface 1a, but the orientation of the wafer 1 is not limited to this.

After placing the wafer 1 on the holding surface 2 a of the chuck table 2 , a polyester sheet 9 is arranged on the back surface 1 b (or front surface 1 a ) of the wafer 1 . FIG. 3 is a perspective view schematically showing a step of disposing a polyester-based sheet. As shown in FIG. 3, a polyester sheet 9 is placed on the wafer 1 so as to cover the wafer 1 .

In addition, in the polyester-based sheet disposing step, a chuck table 2 having a holding surface 2a with a smaller diameter than the diameter of the polyester-based sheet 9 is used. When applying the negative pressure to the polyester sheet 9 by the chuck table 2 in the integration process to be performed later, if the entire holding surface 2a is not covered with the polyester sheet 9, the negative pressure will leak through the gap. , the pressure cannot be appropriately applied to the polyester sheet 9 .

In the method for processing the wafer 1 according to the present embodiment, next, the polyester-based sheet 9 is heated, and an integration step is performed in which the wafer 1 and the polyester-based sheet 9 are integrated by thermocompression bonding. FIG. 4 is a perspective view schematically showing an example of the integration process. In FIG. 4, the dashed lines indicate what can be seen through the polyester-based sheet 9, which is transparent or translucent to visible light.

In the integration step, first, the switching portion 2c of the chuck table 2 is operated to bring the suction source 2b into a communication state in which it is connected to the porous member above the chuck table 2, and the negative pressure from the suction source 2b is applied to the polyester sheet 9. act. Then, the polyester sheet 9 is brought into close contact with the wafer 1 by the atmospheric pressure.

Next, while the polyester sheet 9 is being sucked by the suction source 2b, the polyester sheet 9 is heated to perform thermocompression bonding. For heating the polyester sheet 9, for example, an infrared lamp 4 arranged above the chuck table 2 is used as shown in FIG. The infrared lamp 4 can irradiate infrared rays 4a having a wavelength at least which the material of the polyester-based sheet 9 absorbs.

The infrared lamp 4 is operated to irradiate the polyester sheet 9 with infrared rays 4a to heat the polyester sheet 9. - 特許庁Then, the polyester sheet 9 is thermocompression bonded to the wafer 1 .

Heating of the polyester-based sheet 9 may be performed by other methods. FIG. 5 is a perspective view schematically showing another example of the integration process. In FIG. 5, what can be seen through the polyester-based sheet 9, which is transparent or translucent to visible light, is indicated by dashed lines. The integration process shown in FIG. 5 is performed by a heat gun 6 arranged above the chuck table 2 .

The heat gun 6 includes a heating means such as a heating wire and a blower mechanism such as a fan, and can heat and jet air. While a negative pressure is applied to the polyester sheet 9 by the suction source 2b, hot air 6a is supplied from the upper surface of the polyester sheet 9 by the heat gun 6 to heat the polyester sheet 9 to a predetermined temperature. It is thermocompression bonded to.

Moreover, the heating of the polyester-based sheet 9 may be performed by another method, for example, by pressing the wafer 1 from above with a member heated to a predetermined temperature. FIG. 6 is a perspective view schematically showing another example of the integration process. In FIG. 6, what can be seen through the polyester-based sheet 9, which is transparent or translucent to visible light, is indicated by a dashed line.

In the integration step shown in FIG. 6, for example, a heat roller 8 having a heat source inside is used. Also in the integration step shown in FIG. 6, first, a negative pressure is applied to the polyester-based sheet 9 by the suction source 2b, and the polyester-based sheet 9 is brought into close contact with the wafer 1 by atmospheric pressure.

After that, the heat roller 8 is heated to a predetermined temperature and placed on one end of the holding surface 2 a of the chuck table 2 . Then, the heat roller 8 is rotated to roll the heat roller 8 on the chuck table 2 from the one end to the other end. Then, the polyester sheet 9 is thermocompression bonded to the wafer 1 . At this time, when a force is applied in the direction of pressing down the polyester sheet 9 by the heat roller 8, thermocompression bonding is performed at a pressure higher than the atmospheric pressure. Incidentally, it is preferable to coat the surface of the heat roller 8 with a fluorine resin.

Alternatively, the heat roller 8 may be replaced by an iron-like pressing member having a flat bottom plate and having an internal heat source to carry out thermocompression bonding of the polyester sheet 9 . In this case, the pressing member is heated to a predetermined temperature to form a hot plate, and the polyester sheet 9 held on the chuck table 2 is pressed from above by the pressing member.

When the polyester-based sheet 9 is heated to a temperature near its melting point by any method, the polyester-based sheet 9 is thermocompression bonded to the wafer 1 . After the polyester-based sheet 9 is thermocompressed, the switching portion 2c is actuated to release the state of communication between the porous member of the chuck table 2 and the suction source 2b, thereby releasing the suction by the chuck table 2. FIG.

It should be noted that the polyester sheet 9 is preferably heated to a temperature below its melting point when the thermocompression bonding is carried out. This is because if the heating temperature exceeds the melting point, the polyester-based sheet 9 may melt and become unable to maintain the shape of the sheet. Moreover, the polyester-based sheet 9 is preferably heated to a temperature equal to or higher than its softening point. This is because thermocompression bonding cannot be properly performed unless the heating temperature reaches the softening point. That is, the polyester sheet 9 is preferably heated to a temperature above its softening point and below its melting point.

Furthermore, some polyester sheets 9 may not have a definite softening point. Therefore, the polyester sheet 9 is preferably heated to a temperature higher than or equal to 20° C. lower than its melting point and lower than its melting point when thermocompression bonding is performed.

Further, when the polyester sheet 9 is a polyethylene terephthalate sheet, the heating temperature is preferably 250.degree. C. to 270.degree. Further, when the polyester sheet 9 is a polyethylene naphthalate sheet, the heating temperature is preferably 160.degree. C. to 180.degree.

Here, the heating temperature refers to the temperature of the polyester-based sheet 9 during the integration step. For example, in the heat sources such as the infrared lamp 4, the heat gun 6, and the heat roller 8, models capable of setting the output temperature have been put into practical use. In some cases, the temperature of 9 does not reach the set output temperature. Therefore, in order to heat the polyester sheet 9 to a predetermined temperature, the output temperature of the heat source may be set higher than the melting point of the polyester sheet 9 .

In the method for processing the wafer 1 according to the present embodiment, a frame supporting step of supporting the polyester-based sheet 9 with the frame 7 is performed before or after the integrating step. FIG. 7A is a perspective view schematically showing the frame supporting process. In the frame supporting step, the polyester sheet 9 is supported by the frame 7 by sandwiching the outer peripheral portion of the polyester sheet 9 between the first frame 7a and the second frame 7f.

First, the polyester sheet 9 is placed on the upper surface 7c of the first frame 7a. At this time, the polyester sheet 9 is positioned so as to cover all the openings 7b of the first frame 7a. Next, the second frame 7f is placed on the polyester sheet 9 with the lower surface 7h facing downward. At this time, the position of the second frame 7f is determined so that the through holes 7i of the second frame 7f are fitted into the pins 7d of the first frame 7a.

When the first frame 7a and the second frame 7f are overlapped, the magnetic force generated by the plurality of magnets 7e provided in the first frame 7a acts to attract both frames to each other, and the outer peripheral portion of the polyester sheet 9 is pulled. sandwiched between the two frames. Therefore, the polyester-based sheet 9 is supported by the frame 7 . At this time, since the pins 7d of the first frame 7a are fitted into the through holes 7i of the second frame 7f, the first frame 7a and the second frame 7f are not horizontally displaced from each other.

Although the case where the frame supporting process is performed after the integration process has been described, the wafer processing method according to this embodiment is not limited to this. For example, the integration process may be performed after the frame support process. In this case, the outer peripheral portion of the polyester sheet 9 is adhered to the first frame 7a and the second frame 7f by heating in the integration process, and the polyester sheet 9 is supported by the frame 7 with a stronger force.

Next, in the wafer processing method according to the present embodiment, the wafer 1 in the state of the frame unit 11 is laser-processed to form a modified layer inside the wafer 1 along the dividing lines 3. A dividing step for dividing the wafer 1 is performed. The dividing step is performed, for example, by a laser processing apparatus shown in FIG. 8(A). FIG. 8A is a perspective view schematically showing the dividing step, and FIG. 8B is a cross-sectional view schematically showing the dividing step.

The laser processing apparatus 10 includes a laser processing unit 12 that irradiates the wafer 1 with a laser beam 14 and a chuck table (not shown) that holds the wafer 1 . The laser processing unit 12 includes a laser oscillator (not shown) capable of oscillating a laser, and can emit a laser beam 14 having a wavelength that is transmissive to the wafer 1 (a wavelength that can be transmitted through the wafer 1). The chuck table can move (process feed) along a direction parallel to the upper surface.

The laser processing unit 12 irradiates the wafer 1 held on the chuck table with a laser beam 14 emitted from the laser oscillator. A processing head 12 a provided in the laser processing unit 12 has a mechanism for positioning a focal point 12 b of the laser beam 14 at a predetermined height inside the wafer 1 .

When laser processing the wafer 1, the frame unit 11 is placed on the chuck table, and the wafer 1 is held on the chuck table with the polyester sheet 9 interposed therebetween. Next, the chuck table is rotated to align the dividing line 3 of the wafer 1 with the processing feed direction of the laser processing apparatus 10 . Also, the relative positions of the chuck table and the laser processing unit 12 are adjusted so that the processing head 12a is arranged above the extension line of the planned division line 3 . Then, the focal point 12b of the laser beam 14 is positioned at a predetermined height position.

Next, while irradiating the inside of the wafer 1 with a laser beam 14 from the laser processing unit 12, the chuck table and the laser processing unit 12 are relatively moved along the processing feed direction parallel to the upper surface of the chuck table. That is, the focal point 12b of the laser beam 14 is positioned inside the wafer 1, and the laser beam 14 is irradiated onto the wafer 1 along the line 3 to divide. Then, a modified layer 3 a is formed inside the wafer 1 . In addition, in FIG. 8A, the modified layer 3a formed inside the wafer 1 is indicated by a broken line.

The irradiation conditions of the laser beam 14 in the dividing step are set as follows, for example. However, the irradiation condition of the laser beam 14 is not limited to this.
Wavelength: 1064nm
Repetition frequency: 50 kHz
Average output: 1W
Feeding speed: 200mm/sec

After forming the modified layer 3a inside the wafer 1 along one dividing line 3, the chuck table and the laser processing unit 12 are relatively moved in the indexing feed direction perpendicular to the processing feed direction, and another Similarly, the wafer 1 is laser-processed along the division line 3 . After forming the modified layer 3a along all the planned dividing lines 3 along one direction, the chuck table is rotated around the axis perpendicular to the holding surface, and the planned dividing lines 3 along the other direction are formed. Similarly, the wafer 1 is laser-processed along the line.

When the modified layer 3 a is formed by condensing the laser beam 14 inside the wafer 1 by the laser processing unit 12 , the leakage light of the laser beam 14 reaches the polyester sheet 9 below the wafer 1 .

For example, when an adhesive tape is used for the frame unit 11 instead of the polyester-based sheet 9, when the glue layer of the adhesive tape is irradiated with the leaked light of the laser beam 14, the glue layer of the adhesive tape is melted and the wafer 1 is removed. Part of the glue layer is fixed to the back surface 1b side. In this case, part of the adhesive layer remains on the back side of the device chips formed by dividing the wafer 1 . Therefore, deterioration in the quality of the device chip becomes a problem.

On the other hand, in the wafer processing method according to the present embodiment, the frame unit 11 uses the polyester-based sheet 9 having no glue layer. Therefore, even if the leaked light of the laser beam 14 reaches the polyester sheet 9, the glue layer does not stick to the back surface 1b side of the wafer 1. FIG. Therefore, the quality of device chips formed from the wafer 1 is kept good.

Next, by expanding the polyester-based sheet 9 radially outward, the wafer 1 is divided to form device chips. After that, a pick-up step of picking up the individual device chips from the polyester-based sheet 9 is performed. A pick-up device 16 shown in the lower part of FIG. 9 is used for expanding the polyester-based sheet 9 . FIG. 9 is a perspective view schematically showing loading of the frame unit 11 into the pickup device 16. As shown in FIG.

The pickup device 16 includes a cylindrical drum 18 having a diameter larger than that of the wafer 1 and a frame holding unit 20 including a frame support 22 . The frame support base 22 of the frame holding unit 20 has an opening with a diameter larger than the diameter of the drum 18 and is arranged at the same height as the upper end of the drum 18 so that the upper end of the drum 18 faces the outer circumference. surround from

A clamp 24 is arranged on the outer peripheral side of the frame support base 22 . The frame unit 11 is fixed to the frame support base 22 when the frame unit 11 is placed on the frame support base 22 and the frame 7 of the frame unit 11 is gripped by the clamp 24 .

The frame support base 22 is supported by a plurality of rods 26 extending along the vertical direction, and an air cylinder 28 for raising and lowering the rods 26 is provided at the lower end of each rod 26 . A plurality of air cylinders 28 are supported by a disk-shaped base 30 . Actuation of each air cylinder 28 pulls the frame support 22 down relative to the drum 18 .

Inside the drum 18, a push-up mechanism 32 is arranged to push up the device chip supported by the polyester sheet 9 from below. A collet 34 (see FIG. 10B) capable of sucking and holding the device chip is arranged above the drum 18 . The push-up mechanism 32 and collet 34 are horizontally movable along the upper surface of the frame support 22 . Also, the collet 34 is connected to a suction source 34a (see FIG. 10B) via a switching portion 34b (see FIG. 10B).

When expanding the polyester-based sheet 9, first, the air cylinder 28 is operated so that the height of the upper end of the drum 18 of the pickup device 16 and the height of the upper surface of the frame support 22 approximately match each other. 22 height adjustment. For example, the height position of the upper surface of the frame support base 22 may be positioned at a height position lower than the upper end of the drum 18 by the thickness of the first frame 7a. Next, the frame unit 11 carried out from the laser processing device 10 is placed on the drum 18 of the pickup device 16 .

After that, the frame 7 of the frame unit 11 is fixed on the frame support base 22 by the clamps 24 . FIG. 10A is a cross-sectional view schematically showing the frame unit 11 fixed on the frame support base 22. FIG. Inside the wafer 1, a modified layer 3a is formed along the dividing line 3. As shown in FIG.

Next, the air cylinder 28 is operated to pull the frame support 22 of the frame holding unit 20 downward with respect to the drum 18 . Then, as shown in FIG. 10(B), the polyester sheet 9 is expanded radially outward. FIG. 10(B) is a cross-sectional view schematically showing the expanded polyester sheet 9. As shown in FIG.

When the polyester-based sheet 9 is expanded, a force directed radially outward acts on the wafer 1, and the wafer 1 is divided starting from the modified layer 3a to form individual device chips 1c. When the polyester sheet 9 is further expanded, the intervals between the device chips 1c supported by the polyester sheet 9 are widened, making it easier to pick up the individual device chips 1c.

In the wafer processing method according to the present embodiment, after the wafer 1 is divided to form individual device chips 1c, a pick-up step of picking up the device chips 1c from the polyester-based sheet 9 is performed. In the pick-up process, the device chip 1c to be picked up is determined, the push-up mechanism 32 is moved below the device chip 1c, and the collet 34 is moved above the device chip 1c.

After that, the push-up mechanism 32 is operated to push up the device chip 1c from the polyester sheet 9 side. Then, the switching portion 34b is operated to connect the collet 34 to the suction source 34a. Then, the device chip 1c is held by suction by the collet 34, and the device chip 1c is picked up from the polyester sheet 9. As shown in FIG. The individual device chips 1c picked up are then mounted on a predetermined wiring board or the like for use.

For example, when the frame unit 11 is formed using an adhesive tape, the leakage light of the laser beam 14 irradiated to the wafer 1 in the dividing process reaches the adhesive tape, and the glue layer of the adhesive tape is applied to the back side of the device chip. Stick. Then, there is a problem that the quality of the device chip is deteriorated due to adhesion of the adhesive layer.

On the other hand, according to the wafer processing method according to the present embodiment, it is possible to form the frame unit 11 using the polyester-based sheet 9 having no adhesive layer by thermocompression bonding. is unnecessary. As a result, the quality of the device chip does not deteriorate due to adhesion of the glue layer to the back surface.

It should be noted that the present invention is not limited to the description of the above embodiments, and can be implemented with various modifications. For example, in the above embodiment, the case where the polyester-based sheet 9 is, for example, a polyethylene terephthalate sheet or a polyethylene naphthalate sheet has been described, but one aspect of the present invention is not limited to this. For example, other materials may be used for the polyester-based sheet, such as a polytrimethylene terephthalate sheet, a polybutylene terephthalate sheet, a polybutylene naphthalate sheet, or the like.

In addition, the structures, methods, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention.

REFERENCE SIGNS LIST 1 wafer 1a front surface 1b rear surface 3 dividing line 3a modified layer 5 device 7, 7a, 7f frames 7b, 7g opening 7c upper surface 7d pin 7e magnet 7h lower surface 7i through hole 9 polyester sheet 11 frame unit 2 chuck table 2a holding Surface 2b, 34a Suction source 2c, 34b Switching unit 4 Infrared lamp 4a Infrared ray 6 Heat gun 6a Hot air 8 Heat roller 10 Laser processing device 12 Laser processing unit 12a Processing head 12b Focusing point 14 Laser beam 16 Pickup device 18 Drum 20 Frame holding unit 22 frame support base 24 clamp 26 rod 28 air cylinder 30 base 32 push-up mechanism 34 collet

Claims (6)

A wafer processing method for dividing a wafer in which a plurality of devices are formed in respective regions of a surface partitioned by dividing lines into individual device chips,
A polyester-based sheet disposing step of disposing a polyester-based sheet on the back surface or the front surface of the wafer;
an integration step of heating the polyester-based sheet and integrating the wafer and the polyester-based sheet by thermocompression bonding;
Before or after the integration step, a first frame having an opening sized to accommodate the wafer and having a plurality of magnets, and a second frame having an opening sized to accommodate the wafer. , and the outer peripheral portion of the polyester sheet is sandwiched between the first frame and the second frame by the magnetic force generated by the magnet, so that the polyester sheet is a frame supporting step of supporting with the frame;
A focal point of a laser beam having a wavelength that is transmissive to the wafer is positioned inside the wafer, and the laser beam is irradiated to the wafer along the dividing line to form a modified layer on the wafer. and dividing the wafer into individual device chips;
a picking up step of picking up the individual device chips from the polyester sheet;
A wafer processing method comprising: 2. The method of processing a wafer according to claim 1, wherein said thermocompression bonding is performed by irradiation of infrared rays in said integrating step. 2. The method of processing a wafer according to claim 1, wherein in said pick-up step, said polyester sheet is expanded to widen the space between the device chips, and said device chips are pushed up from said polyester sheet side. 2. The wafer processing method according to claim 1, wherein said polyester sheet is either a polyethylene terephthalate sheet or a polyethylene naphthalate sheet. In the integration step, the heating temperature is 250° C. to 270° C. when the polyester sheet is the polyethylene terephthalate sheet, and the heating temperature is 160° C. to 160° C. when the polyester sheet is the polyethylene naphthalate sheet. 5. The method of processing a wafer according to claim 4, wherein the temperature is 180.degree. 2. The method of processing a wafer according to claim 1, wherein said wafer is made of any one of Si, GaN, GaAs and glass.

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