JP2020202233A - Wafer processing method - Google Patents

Abstract

To form a device chip without deteriorating quality.SOLUTION: A wafer processing method for dividing a wafer in which a plurality of devices are formed into individual device chips comprises a polyolefin-based sheet arranging step, an integrating step, a dividing step, and a picking-up step. The polyolefin-based sheet arranging step positions the wafer in an opening of a frame and arranges a polyolefin-based sheet in a rear surface or a surface of the wafer and an outer periphery of the frame, the opening housing the wafer. The integrating step heats and presses the polyolefin-based sheet and integrates the wafer and the frame via the polyolefin-based sheet. The dividing step forms a modified layer in the wafer by irradiating the wafer with a laser beam of a wavelength having permeability to the wafer along the division schedule lines and divides the wafer into individual device chips. The picking-up step cools the polyolefin-based sheet, pushes up the device chips, and picks up the device chips.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for processing a wafer in which a wafer formed in each region of a surface in which a plurality of devices are partitioned by a planned division line is divided into individual device chips.

In the manufacturing process of device chips used in electronic devices such as mobile phones and personal computers, first, a plurality of intersecting planned division 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), and LEDs (Light Emitting Diodes) are formed in each area partitioned by the planned division line.

Then, 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 the front surface of the wafer, and the wafer, the adhesive tape, and the annular frame are integrated. Form the frame unit that became. Then, when the wafer included in the frame unit is processed and divided along the planned division line, individual device chips are formed.

For example, a laser processing apparatus is used to divide the wafer. The laser machining apparatus includes a chuck table that holds the wafer via an adhesive tape, and a laser machining unit that focuses a laser beam having a wavelength that is transparent to the wafer into the inside of 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, while the chuck table and the laser processing unit are relatively moved along the direction parallel to the upper surface of the chuck table, the laser processing unit irradiates the wafer with the laser beam along each scheduled division line. When the laser beam is focused inside the wafer, a modified layer serving as a starting point of division 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 the formed device chip is picked up from the adhesive tape, the adhesive tape is subjected to a treatment such as irradiating the adhesive tape with ultraviolet rays in advance to reduce the adhesive strength of the adhesive tape. As a processing apparatus having high production efficiency of device chips, there is known a processing apparatus capable of continuously dividing a wafer and irradiating an adhesive tape with ultraviolet rays with one apparatus (see Patent Document 2).

Japanese Patent No. 3408805 Japanese Patent No. 3076179

The adhesive tape includes, for example, a base material layer formed of a vinyl chloride sheet or the like, and a glue layer disposed on the base material layer. In a laser processing device, a laser beam is focused inside a wafer in order to form a modified layer as a division starting point inside the wafer, and a part of the leaked light of the laser beam reaches the glue layer of the adhesive tape. .. Then, the glue layer of the adhesive tape is melted by the thermal influence of the irradiation of the laser beam, and a part of the glue layer is fixed to the back surface side or the front surface side of the device chip formed from the wafer.

In this case, even if the adhesive tape is irradiated with ultraviolet rays when the device chip is picked up from the adhesive tape, the part of the glue layer remains on the back surface or the front surface side of the picked up device chip. It ends up. Therefore, deterioration of the quality of the device chip becomes a problem.

The present invention has been made in view of the above problems, and an object thereof is derived from the adhesion of the glue layer to the device chip without the glue layer adhering to the back surface or the front surface side of the formed device chip. The purpose of the present invention is to provide a method for processing a wafer that does not cause deterioration in quality.

According to one aspect of the present invention, a plurality of devices are a method for processing a wafer in which a wafer formed in each region of a surface partitioned by a planned division line is divided into individual device chips, and the wafer is accommodated. A polyolefin sheet disposing step of positioning a wafer in the opening of a frame having an opening and disposing a polyolefin sheet on the back surface or the front surface of the wafer and the outer periphery of the frame, and heating the polyolefin sheet. The integration step of integrating the wafer and the frame via the polyolefin-based sheet by pressing and pressing, and the focusing point of the laser beam having a wavelength that is transparent to the wafer are positioned inside the wafer. A division step of irradiating the wafer with the laser beam along the planned division line to form a modified layer on the wafer and dividing the wafer into individual device chips, and each device chip of the polyolefin-based sheet. In each region corresponding to, the polyolefin-based sheet is cooled, the device chip is pushed up from the polyolefin-based sheet side, and the device chip is picked up from the polyolefin-based sheet. Wafer processing methods are provided.

Further, preferably, in the integration step, after the integration is performed, the polyolefin-based sheet protruding from the outer periphery of the frame is removed.

Also, preferably, in the pickup step, the polyolefin-based sheet is expanded to widen the distance between each device chip.

Further, preferably, the polyolefin-based sheet is any one of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet.

Further, preferably, in the integration step, the heating temperature is 120 ° C. to 140 ° C. when the polyolefin-based sheet is the polyethylene sheet, and the heating temperature is 160 when the polyolefin-based sheet is the polypropylene sheet. The temperature is from ° C. to 180 ° C., and when the polyolefin-based sheet is the polystyrene sheet, the heating temperature is 220 ° C. to 240 ° C.

Further, preferably, the wafer is composed of any of Si, GaN, GaAs, and glass.

In the method for processing a wafer according to one aspect of the present invention, when forming a frame unit, the frame and the wafer are formed by using a polyolefin-based sheet that does not have a glue layer without using an adhesive tape having a glue layer. Integrate. The integration step of integrating the frame and the wafer via the polyolefin-based sheet is realized by heating and pressing.

After carrying out the integration step, the wafer is irradiated with a laser beam having a wavelength that is transparent to the wafer, and a reforming layer along the planned division line is formed inside the wafer to divide the wafer. Then, in each region of the polyolefin-based sheet corresponding to each device chip, the polyolefin-based sheet is cooled, the device chip is pushed up from the polyolefin-based sheet side, and the device chip is picked up from the polyolefin-based sheet. Each of the picked-up device chips is mounted on a predetermined mounting target. When the polyolefin-based sheet is cooled at the time of pickup, the polyolefin-based sheet shrinks and the polyolefin-based sheet can be easily peeled off, so that the load on the device chip can be reduced.

When the modified layer is formed inside the wafer, the leakage light of the laser beam reaches the polyolefin-based sheet. However, since the polyolefin-based sheet does not have a glue layer, the glue layer does not melt and adhere to the back surface or the front surface side of the device chip.

That is, according to one aspect of the present invention, since the frame unit can be formed by using a polyolefin sheet without a glue layer, an adhesive tape having a glue layer is unnecessary, and as a result, a device caused by adhesion of the glue layer. There is no deterioration in chip quality.

Therefore, according to one aspect of the present invention, there is provided a method for processing a wafer in which the glue layer does not adhere to the back surface or the front surface side of the formed device chip and the quality does not deteriorate due to the adhesion of the glue layer to the device chip. Will be done.

FIG. 1A is a perspective view schematically showing the front surface of the wafer, and FIG. 1B is a perspective view schematically showing the back surface of the wafer. It is a perspective view which shows typically the state of positioning a wafer and a frame on the holding surface of a chuck table. It is a perspective view which shows typically the polyolefin-based sheet arrangement process. It is a perspective view which shows an example of the integration process typically. FIG. 5A is a perspective view schematically showing how the polyolefin-based sheet is cut, and FIG. 5B is a perspective view schematically showing the formed frame unit. FIG. 6A is a perspective view schematically showing the division process, and FIG. 6B is a cross-sectional view schematically showing the division process. It is a perspective view which shows typically the carrying-in of a frame unit into a pickup device. FIG. 8A is a cross-sectional view schematically showing a frame unit fixed on a frame support base, and FIG. 8B is a cross-sectional view schematically showing a pickup process.

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

The wafer 1 is, for example, a material such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor, or a material such as sapphire, glass, or quartz. It is a substantially disk-shaped substrate made of. The glass is, for example, alkaline glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, quartz glass and the like.

The surface 1a of the wafer 1 is partitioned by a plurality of scheduled division lines 3 arranged in a grid pattern. Further, devices 5 such as ICs, LSIs, and LEDs are formed in each region of the surface 1a of the wafer 1 divided by the planned division lines 3. In the processing method of the wafer 1 according to the present embodiment, a reforming layer along the planned division line 3 is formed inside the wafer 1, the wafer 1 is divided from the reforming layer as a starting point, and individual device chips are formed. Form.

When forming the modified layer on the wafer 1, a laser beam having a wavelength that is transparent to the wafer 1 is irradiated to the wafer 1 along the planned division line 3, and the laser beam is collected inside the wafer 1. Make it shine. At this time, the laser beam may be irradiated to the wafer 1 from the front surface 1a side shown in FIG. 1 (A), or may be irradiated to the wafer 1 from the back surface 1b side shown in FIG. 1 (B). When irradiating the wafer 1 with a laser beam from the back surface 1b side, the wafer 1 is transmitted through the wafer 1 by using an alignment means equipped with an infrared camera to detect the planned division line 3 on the front surface 1a side, and the line 3 is along the planned division line 3. And irradiate the laser beam.

Before the wafer 1 is carried into the laser processing apparatus 8 (see FIG. 6A) in which the laser processing for forming the modified layer is performed on the wafer 1, the wafer 1, the polyolefin sheet, and the frame are integrated. The frame unit is formed. The wafer 1 is carried into the laser processing apparatus 8 in the state of a frame unit and processed.

Then, the wafer 1 can be divided by expanding the polyolefin-based sheet, and the individual device chips formed by dividing the wafer 1 are supported by the polyolefin-based sheet. After that, the space between the device chips is widened by further expanding the polyolefin-based sheet, and the device chips are picked up by the pickup device.

The annular frame 7 (see FIG. 2 and the like) is made of, for example, a material such as metal and includes an opening 7a having a diameter larger than the diameter of the wafer 1. When forming the frame unit, the wafer 1 is positioned in the opening 7a of the frame 7 and is accommodated in the opening 7a.

The polyolefin-based sheet 9 (see FIG. 3 and the like) is a flexible resin-based sheet, and the front and back surfaces are flat. The polyolefin-based sheet 9 has a diameter larger than the outer diameter of the frame 7 and does not have a glue layer. The polyolefin-based sheet 9 is a polymer sheet synthesized using an alkene as a monomer, and is, for example, a polyethylene sheet, a polypropylene sheet, a polystyrene sheet, or the like, which is transparent or translucent to visible light. However, the polyolefin-based sheet 9 is not limited to this, and may be opaque.

Since the polyolefin-based sheet 9 does not have adhesiveness, it cannot be attached to the wafer 1 and the frame 7 at room temperature. However, since the polyolefin-based sheet 9 has thermoplasticity, when it is heated to a temperature near the melting point in a state where it is bonded to the wafer 1 and the frame 7 while being pressed by applying a predetermined pressure, it partially melts and the wafer 1 and the wafer 1 and the frame 7 are bonded to each other. Can be adhered to the frame 7. Therefore, in the wafer 1 processing method according to the present embodiment, the wafer 1, the frame 7, and the polyolefin sheet 9 are integrated to form a frame unit by heating and pressing as described above.

Next, each step of the wafer 1 processing method according to the present embodiment will be described. First, a polyolefin-based sheet disposing step is carried out in preparation for integrating the wafer 1, the polyolefin-based sheet 9, and the frame 7. FIG. 2 is a perspective view schematically showing how the wafer 1 and the frame 7 are positioned on the holding surface 2a of the chuck table 2. As shown in FIG. 2, the polyolefin-based sheet disposing step is carried out on a chuck table 2 having a holding surface 2a on the upper portion.

The chuck table 2 is provided with a porous member having a diameter larger than the outer diameter of the frame 7 in the center of the upper portion. The upper surface of the porous member is the holding surface 2a of the chuck table 2. As shown in FIG. 3, the chuck table 2 has an exhaust path inside which one end leads to the porous member, and a suction source 2b is arranged on the other end side of the exhaust path. The exhaust passage is provided with a switching portion 2c for switching between a communicating state and a disconnected state, and when the switching portion 2c is in the communicating state, a negative force generated by the suction source 2b on the object to be held placed on the holding surface 2a. Pressure acts to suck and hold the object to be held on the chuck table 2.

In the polyolefin-based sheet disposing step, first, as shown in FIG. 2, the wafer 1 and the frame 7 are placed on the holding surface 2a of the chuck table 2, and the wafer 1 is positioned in the opening 7a of the frame 7.

At this time, the orientation of the wafer 1 is selected in consideration of whether the irradiated surface to be irradiated with the laser beam is the front surface 1a or the back surface 1b in the division step described later. For example, when the irradiated surface is the surface 1a, the surface 1a side is directed downward. Further, for example, when the irradiated surface 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 the case where the irradiated surface of the laser beam is the surface 1a as an example, but the orientation of the wafer 1 is not limited to this.

After the wafer 1 and the frame 7 are placed on the holding surface 2a of the chuck table 2, the polyolefin sheet 9 is arranged on the back surface 1b (or the front surface 1a) of the wafer 1 and the outer periphery of the frame 7. FIG. 3 is a perspective view schematically showing a polyolefin-based sheet arrangement process. As shown in FIG. 3, a polyolefin-based sheet 9 is arranged on both the wafer 1 and the frame 7 so as to cover them.

In the polyolefin-based sheet disposing step, a polyolefin-based sheet 9 having a diameter larger than that of the holding surface 2a of the chuck table 2 is used. When the negative pressure of the chuck table 2 is applied to the polyolefin sheet 9 in the integration step to be performed later, if the entire holding surface 2a is not covered by the polyolefin sheet 9, the negative pressure leaks from the gap. This is because the pressure cannot be appropriately applied to the polyolefin sheet 9.

In the processing method of the wafer 1 according to the present embodiment, next, an integration step of heating and pressing the polyolefin-based sheet 9 to integrate the wafer 1 and the frame 7 with the polyolefin-based sheet 9 is carried out. .. FIG. 4 is a perspective view schematically showing an example of the integration process. In FIG. 4, what can be visually recognized through the polyolefin sheet 9 which is transparent or translucent with respect to visible light is shown by a broken line.

In the integration step, first, the switching portion 2c of the chuck table 2 is operated to connect the suction source 2b to the porous member on the upper part of the chuck table 2, and the negative pressure generated by the suction source 2b is applied to the polyolefin sheet 9. Make it work. Then, the polyolefin sheet 9 comes into close contact with the wafer 1 and the frame 7 due to the atmospheric pressure.

Next, the polyolefin sheet 9 is heated and further pressed to perform thermocompression bonding. As shown in FIG. 4, the heating and pressing of the polyolefin-based sheet 9 is carried out using a heat roller 4 having a heat source inside.

The heat roller 4 is heated to a predetermined temperature, and the heat roller 4 is placed on one end of the holding surface 2a of the chuck table 2. Then, the heat roller 4 is rotated, and the heat roller 4 is rolled on the chuck table 2 from one end to the other end. Then, the polyolefin-based sheet 9 is thermocompression-bonded to the wafer 1 and the frame 7. At this time, a force is applied in the direction of pushing down the polyolefin sheet 9 by the heat roller 4, and thermocompression bonding is performed at a pressure higher than the atmospheric pressure. It is preferable to coat the surface of the heat roller 4 with a fluororesin.

Further, the polyolefin sheet 9 may be heated and pressed by using an iron-shaped pressing member having a heat source inside and having a flat bottom plate instead of the heat roller 4. In this case, the pressing member is heated to a predetermined temperature to form a hot plate, and the polyolefin-based sheet 9 held on the chuck table 2 is pressed from above by the pressing member.

After the polyolefin sheet 9 is thermocompression-bonded, the switching portion 2c is operated to release the communication state between the porous member of the chuck table 2 and the suction source 2b, and the adsorption by the chuck table 2 is released.

Next, the polyolefin-based sheet 9 protruding from the outer periphery of the frame 7 is cut and removed. FIG. 5A is a perspective view schematically showing how the polyolefin sheet 9 is cut. As shown in FIG. 5A, an annular cutter 6 is used for cutting. The cutter 6 has a through hole and is rotatable around a rotation axis pierced through the through hole.

First, the annular cutter 6 is positioned above the frame 7. At this time, the rotation axis of the cutter 6 is aligned with the radial direction of the chuck table 2. Next, the cutter 6 is lowered to sandwich the polyolefin-based sheet 9 between the frame 7 and the cutter 6, and the polyolefin-based sheet 9 is cut. Then, a cutting mark 9a is formed on the polyolefin-based sheet 9.

Further, the cutter 6 is made to go around the opening 7a of the frame 7 along the frame 7, and the cut mark 9a surrounds a predetermined region of the polyolefin sheet 9. Then, the polyolefin-based sheet 9 in the region on the outer peripheral side of the cutting mark 9a is removed so as to leave the region of the polyolefin-based sheet 9. Then, the unnecessary portion of the polyolefin sheet 9 including the region protruding from the outer periphery of the frame 7 can be removed.

An ultrasonic cutter may be used for cutting the polyolefin-based sheet, or a vibration source that vibrates the above-mentioned annular cutter 6 at a frequency in the ultrasonic band may be connected to the cutter 6. Further, when cutting the polyolefin-based sheet 9, the polyolefin-based sheet 9 may be cooled and cured in order to facilitate cutting. As described above, the frame unit 11 in which the wafer 1 and the frame 7 are integrated via the polyolefin-based sheet 9 is formed. FIG. 5B is a perspective view schematically showing the formed frame unit 11.

When carrying out the integration step, the polyolefin-based sheet 9 is preferably heated to a temperature equal to or lower than its melting point. This is because if the heating temperature exceeds the melting point, the polyolefin-based sheet 9 may melt and the shape of the sheet may not be maintained. Further, the polyolefin-based sheet 9 is preferably heated to a temperature equal to or higher than its softening point. This is because the integration process cannot be properly performed unless the heating temperature reaches the softening point. That is, the polyolefin-based sheet 9 is preferably heated to a temperature above its softening point and below its melting point.

Furthermore, some polyolefin-based sheets 9 may not have clear softening points. Therefore, when carrying out the integration step, the polyolefin-based sheet 9 is preferably heated to a temperature 20 ° C. lower than its melting point and lower than its melting point.

When the polyolefin-based sheet 9 is a polyethylene sheet, the heating temperature is preferably 120 ° C to 140 ° C. When the polyolefin-based sheet 9 is a polypropylene sheet, the heating temperature is preferably 160 ° C. to 180 ° C. Further, when the polyolefin-based sheet 9 is a polystyrene sheet, the heating temperature is preferably 220 ° C. to 240 ° C.

Here, the heating temperature refers to the temperature of the polyolefin-based sheet 9 when the integration step is carried out. For example, a model in which the output temperature can be set is put into practical use as a heat source such as a heat roller 4, but even if the polyolefin-based sheet 9 is heated using the heat source, the temperature of the polyolefin-based sheet 9 is set. It may not reach the output temperature. Therefore, in order to heat the polyolefin-based sheet 9 to a predetermined temperature, the output temperature of the heat source may be set higher than the melting point of the polyolefin-based sheet 9.

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 along the planned division line 3 inside the wafer 1. A dividing step for dividing the wafer 1 is performed. The dividing step is carried out, for example, by the laser processing apparatus shown in FIG. 6 (A). FIG. 6A is a perspective view schematically showing the dividing process, and FIG. 8B is a cross-sectional view schematically showing the dividing process.

The laser processing apparatus 8 includes a laser processing unit 10 that irradiates the wafer 1 with a laser beam 12, and a chuck table (not shown) that holds the wafer 1. The laser processing unit 10 includes a laser oscillator (not shown) capable of oscillating a laser, and can emit a laser beam 12 having a wavelength that is transparent to the wafer 1 (a wavelength that can pass through the wafer 1). The chuck table can be moved (processed and fed) along a direction parallel to the upper surface.

The laser processing unit 10 irradiates the wafer 1 held on the chuck table with the laser beam 12 emitted from the laser oscillator. The processing head 10a included in the laser processing unit 10 has a mechanism for positioning the focusing point 10b of the laser beam 12 at a predetermined height position 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 by the chuck table via the polyolefin sheet 9. Next, the chuck table is rotated to align the scheduled division line 3 of the wafer 1 with the machining feed direction of the laser machining apparatus 8. Further, the relative positions of the chuck table and the laser machining unit 10 are adjusted so that the machining head 10a is arranged above the extension line of the scheduled division line 3. Then, the focusing point 10b of the laser beam 12 is positioned at a predetermined height position.

Next, the chuck table and the laser processing unit 10 are relatively moved along the processing feed direction parallel to the upper surface of the chuck table while irradiating the inside of the wafer 1 with the laser beam 12 from the laser processing unit 10. That is, the condensing point 10b of the laser beam 12 is positioned inside the wafer 1, and the laser beam 12 is irradiated to the wafer 1 along the scheduled division line 3. Then, the modified layer 3a is formed inside the wafer 1. In FIG. 6A, the modified layer 3a formed inside the wafer 1 is shown by a broken line.

The irradiation conditions of the laser beam 12 in the dividing step are set as follows, for example. However, the irradiation conditions of the laser beam 12 are not limited to this.
Wavelength: 1064 nm
Repeat frequency: 50kHz
Average output: 1W
Feed rate: 200 mm / sec

After forming the modified layer 3a inside the wafer 1 along one scheduled division line 3, the chuck table and the laser machining unit 10 are moved relative to the index feed direction perpendicular to the machining feed direction, and the other The wafer 1 is laser-machined in the same manner along the planned division line 3. After forming the modified layer 3a along all the planned division lines 3 along one direction, the chuck table is rotated around the axis perpendicular to the holding surface to form the planned division line 3 along the other direction. The wafer 1 is laser-machined in the same manner.

When the modified layer 3a is formed by condensing the laser beam 12 inside the wafer 1 by the laser processing unit 10, the leaked light of the laser beam 12 reaches the polyolefin sheet 9 below the wafer 1.

For example, when an adhesive tape is used for the frame unit 11 instead of the polyolefin sheet 9, when the adhesive layer of the adhesive tape is irradiated with the leakage light of the laser beam 12, the adhesive layer of the adhesive tape melts and the wafer 1 A part of the glue layer is fixed to the back surface 1b side. In this case, a part of the glue layer remains on the back surface side of the device chip formed by dividing the wafer 1. Therefore, deterioration of the quality of the device chip becomes a problem.

On the other hand, in the wafer processing method according to the present embodiment, the polyolefin-based sheet 9 having no glue layer in the frame unit 11 is used. Therefore, even if the leaked light of the laser beam 12 reaches the polyolefin-based sheet 9, the glue layer does not adhere to the back surface 1b side of the wafer 1. Therefore, the quality of the device chip formed from the wafer 1 is kept good.

Next, the polyolefin sheet 9 is expanded outward in the radial direction to divide the wafer 1 to form a device chip. Then, a pickup step of picking up the individual device chips from the polyolefin-based sheet 9 is performed. A pickup device 14 shown in the lower part of FIG. 7 is used to expand the polyolefin-based sheet 9. FIG. 7 is a perspective view schematically showing the loading of the frame unit 11 into the pickup device 14.

The pickup device 14 includes a cylindrical drum 16 having a diameter larger than the diameter of the wafer 1 and a frame holding unit 18 including a frame support base 22. The frame support 22 of the frame holding unit 18 has an opening having a diameter larger than the diameter of the drum 16, is arranged at the same height as the upper end of the drum 16, and the upper end of the drum 16 is on the outer peripheral side. Surround from.

A clamp 20 is arranged on the outer peripheral side of 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 20, the frame unit 11 is fixed to the frame support base 22.

The frame support base 22 is supported by a plurality of rods 24 extending in the vertical direction, and an air cylinder 26 for raising and lowering the rods 24 is arranged at the lower end of each rod 24. The plurality of air cylinders 26 are supported by a disc-shaped base 28. When each air cylinder 26 is operated, the frame support base 22 is pulled down with respect to the drum 16.

Inside the drum 16, a push-up mechanism 30 for pushing up the device chip supported by the polyolefin-based sheet 9 from below is arranged. The push-up mechanism 30 includes a cooling portion 30a including a cooling mechanism such as a Peltier element at the upper end. A collet 32 (see FIG. 8B) capable of sucking and holding the device chip is arranged above the drum 16. The push-up mechanism 30 and the collet 32 are movable in the horizontal direction along the upper surface of the frame support base 22. Further, the collet 32 is connected to the suction source 32a (see FIG. 8B) via the switching portion 32b (see FIG. 8B).

When expanding the polyolefin-based sheet 9, first, the air cylinder 26 is operated so that the height of the upper end of the drum 16 of the pickup device 14 and the height of the upper surface of the frame support 22 match. Adjust the height of the. Next, the frame unit 11 carried out from the laser processing device 8 is placed on the drum 16 and the frame support 22 of the pickup device 14.

After that, the frame 7 of the frame unit 11 is fixed on the frame support 22 by the clamp 20. FIG. 8A is a cross-sectional view schematically showing the frame unit 11 fixed on the frame support base 22. A modified layer 3a is formed inside the wafer 1 along the planned division line 3.

Next, the air cylinder 26 is operated to pull down the frame support base 22 of the frame holding unit 18 with respect to the drum 16. Then, as shown in FIG. 8B, the polyolefin-based sheet 9 is expanded radially outward. FIG. 8B is a cross-sectional view schematically showing the expanded polyolefin-based sheet 9.

When the polyolefin-based sheet 9 is expanded, a force acting outward in the radial direction acts on the wafer 1, the wafer 1 is divided starting from the modified layer 3a, and individual device chips 1c are formed. When the polyolefin-based sheet 9 is further expanded, the distance between the device chips 1c supported by the polyolefin-based sheet 9 is widened, and the individual device chips 1c can be easily picked up.

In the wafer processing method according to the present embodiment, a pickup step of picking up the device chip 1c from the polyolefin sheet 9 is carried out after the wafer 1 is divided to form individual device chips 1c. In the pick-up step, the device chip 1c to be picked up is determined, the push-up mechanism 30 is moved below the device chip 1c, and the collet 32 is moved above the device chip 1c.

After that, the cooling unit 30a is operated to lower the temperature, and the cooling unit 30a is brought into contact with the region corresponding to the device chip 1c of the polyolefin sheet 9 to cool the region. Further, the push-up mechanism 30 is operated to push up the device chip 1c from the polyolefin-based sheet 9 side. Then, the switching portion 32b is operated to communicate the collet 32 with the suction source 32a. Then, the device chip 1c is sucked and held by the collet 32, and the device chip 1c is picked up from the polyolefin sheet 9. The individual device chips 1c picked up are then mounted on a predetermined wiring board or the like for use.

When the region of the polyolefin-based sheet 9 is cooled by the cooling unit 30a, the polyolefin-based sheet 9 shrinks and a large stress is generated at the interface between the polyolefin-based sheet 9 and the device chip, which facilitates peeling. Therefore, the load applied to the device chip at the time of peeling from the polyolefin sheet 9 is reduced.

For example, when the frame unit 11 is formed by using the adhesive tape, the leaked light of the laser beam 12 irradiated to the wafer 1 reaches the adhesive tape in the dividing step, and the glue layer of the adhesive tape is on the back surface side of the device chip. Stick. Then, the deterioration of the quality of the device chip due to the adhesion of the glue layer becomes a problem.

On the other hand, according to the wafer processing method according to the present embodiment, the frame unit 11 can be formed by using the polyolefin-based sheet 9 having no glue layer by thermocompression bonding, so that the adhesive tape having the glue layer can be formed. Is unnecessary. As a result, the quality of the device chip does not deteriorate due to the adhesion of the glue layer to the back surface side.

The present invention is not limited to the description of the above embodiment, and can be implemented with various modifications. For example, in the above embodiment, the case where the polyolefin-based sheet 9 is, for example, a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet has been described, but one aspect of the present invention is not limited thereto. For example, as the polyolefin-based sheet, other materials may be used, and a copolymer of propylene and ethylene, an olefin-based elastomer, or the like may be used.

In addition, the structure, method, etc. according to the above-described embodiment can be appropriately modified and implemented as long as they do not deviate from the scope of the object of the present invention.

1 Wafer 1a Front surface 1b Back surface 3 Scheduled division line 3a Modified layer 5 Device 7 Frame 7a Opening 9 Polyolefin sheet 9a Cutting mark 11 Frame unit 2 Chuck table 2a Holding surface 2b, 32a Suction source 2c, 32b Switching part 4 Heat roller 6 Cutter 8 Laser Machining Equipment 10 Laser Machining Unit 10a Machining Head 10b Condensing Point 12 Laser Beam 14 Pickup Device 16 Drum 18 Frame Holding Unit 20 Clamp 22 Frame Support 24 Rod 26 Air Cylinder 28 Base 30 Push-up Mechanism 30a Cooling Unit 32 Collet

Claims (6)

A method of processing a wafer in which a plurality of devices divide a wafer formed in each region of a surface partitioned by a planned division line into individual device chips.
A polyolefin-based sheet arranging step of locating a wafer in the opening of a frame having an opening for accommodating a wafer and arranging a polyolefin-based sheet on the back surface or the front surface of the wafer and the outer periphery of the frame.
An integration step of heating and pressing the polyolefin-based sheet to integrate the wafer and the frame via the polyolefin-based sheet.
A focusing point of a laser beam having a wavelength that is transparent to the wafer is positioned inside the wafer, and the laser beam is irradiated to the wafer along the planned division line to form a modified layer on the wafer. Then, the dividing step of dividing the wafer into individual device chips and
In the individual region corresponding to each device chip of the polyolefin-based sheet, the polyolefin-based sheet is cooled, the device chip is pushed up from the polyolefin-based sheet side, and the device chip is picked up from the polyolefin-based sheet. ,
A method for processing a wafer, which comprises. The method for processing a wafer according to claim 1, wherein in the integration step, after the integration is performed, the polyolefin-based sheet protruding from the outer periphery of the frame is removed. The wafer processing method according to claim 1, wherein in the pickup step, the polyolefin-based sheet is expanded to widen the distance between each device chip. The method for processing a wafer according to claim 1, wherein the polyolefin-based sheet is any one of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet. In the integration step, when the polyolefin-based sheet is the polyethylene sheet, the heating temperature is 120 ° C. to 140 ° C., and when the polyolefin-based sheet is the polypropylene sheet, the heating temperature is 160 ° C. to 180 ° C. The method for processing a wafer according to claim 4, wherein the heating temperature is 220 ° C. to 240 ° C. when the polyolefin-based sheet is the polystyrene sheet. The wafer processing method according to claim 1, wherein the wafer is composed of any of Si, GaN, GaAs, and glass.