JP2020188055A - Wafer processing method - Google Patents

Abstract

To form a device chip without compromising quality.SOLUTION: A wafer processing method that divides a wafer in which a device is formed on the surface into individual device chips includes a polyolefin-based sheet disposing step of disposing a polyolefin-based sheet on the back surface or the front surface of the wafer, an integration step of heating the polyolefin-based sheet by hot air to integrate the polyolefin-based sheet with the wafer, a frame support step of sandwiching the outer peripheral portion of the polyolefin-based sheet and supporting the polyolefin-based sheet with a frame including a first frame provided with a magnet and a second frame by using the frame, a dividing step of irradiating the wafer with a laser beam having a wavelength transparent to the wafer to form a modified layer on the wafer and dividing the wafer into individual device chips, and a pickup step of heating the polyolefin-based sheet and picking up the device chip.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. It is to provide a method of processing a wafer which does not cause deterioration of quality.

According to one aspect of the present invention, 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, the back surface of the wafer or the back surface of the wafer. An integral step of arranging a polyolefin-based sheet on the surface and heating the polyolefin-based sheet by applying hot air to the polyolefin-based sheet to integrate the wafer and the polyolefin-based sheet. Before or after the conversion step and the integration step, a first frame having an opening large enough to accommodate the wafer and having a plurality of magnets, and an opening large enough to accommodate the wafer. Using a frame composed of two frames, the outer peripheral portion of the polyolefin-based sheet is sandwiched between the first frame and the second frame by the magnetic force generated by the magnet. A frame support step of supporting the polyolefin sheet with the frame and a focusing point of a laser beam having a wavelength transparent to the wafer are positioned inside the wafer, and the laser beam is placed along the planned division line. In a division step of irradiating the wafer to form a modified layer on the wafer and dividing the wafer into individual device chips, and in individual regions corresponding to each device chip of the polyolefin-based sheet, the polyolefin-based sheet is formed. Provided is a method for processing a wafer, which comprises a pick-up step of heating, pushing up the device chip from the polyolefin-based sheet side, and picking up the device chip from the polyolefin-based sheet.

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 wafer processing method according to one aspect of the present invention, the frame and the wafer are integrated by using a polyolefin-based sheet without a glue layer without using an adhesive tape having a glue layer in the frame unit. The integration step of integrating the polyolefin-based sheet and the wafer is realized by applying hot air to the polyolefin-based sheet.

The wafer processing method according to one aspect of the present invention is composed of 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 includes a plurality of magnets, and the first frame and the second frame are attracted to each other by the magnetic force generated by the magnets.

Then, in the frame support step, a polyolefin-based sheet is arranged between the first frame and the second frame, and the polyolefin-based sheet is sandwiched between the first frame and the second frame. The polyolefin sheet can be supported by the frame.

That is, even if the polyolefin-based sheet does not have a glue layer, the wafer, the polyolefin-based sheet, and the frame can be integrated to form a frame unit by carrying out the integration step and the frame support step. ..

After that, 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 the individual region corresponding to each device chip of the polyolefin-based sheet, the polyolefin-based sheet is heated, 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. If the polyolefin-based sheet is heated during pickup, the adhesive strength of the polyolefin-based sheet is reduced, and 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 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. 5 (A) is a perspective view schematically showing a frame support process, and FIG. 5 (B) is a perspective view schematically showing a 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 modified layer along the planned division line 3 is formed inside the wafer 1, the wafer 1 is divided from the modified 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 along the planned division line 3. And irradiate the laser beam.

The wafer 1, the polyolefin sheet, and the frame are integrated before the wafer 1 is carried into the laser processing apparatus 6 (see FIG. 6 (A)) in which the laser processing for forming the modified layer is performed on the wafer 1. The frame unit is formed. The wafer 1 is carried into the laser processing apparatus 6 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 FIGS. 5A and 5B, etc.) has, for example, a first frame 7a made of a material such as metal and having an opening 7b large enough to accommodate the wafer 1. It is composed of two members, a second frame 7f having an opening 7g having a size capable of accommodating the wafer 1. For example, the first frame 7a and the second frame 7f have substantially the same shape.

The first frame 7a includes a plurality of pins 7d on the upper surface 7c. Further, a plurality of magnets 7e are embedded and arranged in the upper surface 7c of the first frame 7a. The second frame 7f is provided with a plurality of through holes 7i penetrating in the thickness direction. The through hole of the second frame 7f so that the pin 7d of the first frame 7a is fitted into the through hole 7i when the first frame 7a and the second frame 7f are overlapped with each other. The 7i is formed by the number, position and size corresponding to the pins 7d of the first frame 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 diameter of the opening 7b of the first frame 7a and the opening 7g of the second frame 7f constituting 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, or a polystyrene sheet, 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 at room temperature. However, since the polyolefin-based sheet 9 has thermoplasticity, when it is heated to a temperature near the melting point while being bonded to the wafer 1 while applying a predetermined pressure, it can be partially melted and adhered to the wafer 1.

In the processing method of the wafer 1 according to the present embodiment, the polyolefin-based sheet 9 is adhered to the back surface 1b side of the wafer 1 by heating, and the outer peripheral portion of the polyolefin-based sheet 9 is formed by the first frame 7a and the second frame 7f. It is sandwiched between, to form a frame unit.

Next, each step of the wafer 1 processing method according to the present embodiment will be described. First, a polyolefin-based sheet arranging step is carried out in preparation for integrating the wafer 1 and the polyolefin-based sheet 9. 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. 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 wafer 1 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 is placed on the holding surface 2a of the chuck table 2. 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 is 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. FIG. 3 is a perspective view schematically showing a polyolefin-based sheet arrangement process. As shown in FIG. 3, the polyolefin sheet 9 is arranged on the wafer 1 so as to cover the wafer 1.

In the polyolefin-based sheet disposing step, a chuck table 2 having a holding surface 2a having a diameter smaller than the diameter of the polyolefin-based sheet 9 is used. When the negative pressure generated by 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 with 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, hot air is blown to the polyolefin-based sheet 9 to heat the polyolefin-based sheet 9, and the wafer 1 and the polyolefin-based sheet 9 are integrated. To carry 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 due to the atmospheric pressure.

Next, the polyolefin-based sheet 9 is heated while sucking the polyolefin-based sheet 9 by the suction source 2b. Heating of the polyolefin-based sheet 9 is performed, for example, by a heat gun 4 arranged above the chuck table 2 as shown in FIG.

The heat gun 4 is provided with a heating means such as a heating wire and a blowing mechanism such as a fan inside, and can heat and inject air. When hot air 4a is supplied from the upper surface to the polyolefin sheet 9 by the heat gun 4 while applying the negative pressure from the suction source 2b to the polyolefin sheet 9, and the polyolefin sheet 9 is heated to a predetermined temperature, the polyolefin sheet 9 becomes the wafer 1. Is thermocompression bonded to.

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.

When thermocompression bonding is performed, 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 thermocompression bonding cannot be performed properly 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 thermocompression bonding is performed, 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 gun 4, but even if the polyolefin-based sheet 9 is heated by 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.

In the wafer 1 processing method according to the present embodiment, a frame support step of supporting the polyolefin-based sheet 9 with the frame 7 is carried out before or after the integration step. FIG. 5A is a perspective view schematically showing a frame supporting process. In the frame support step, the outer peripheral portion of the polyolefin-based sheet 9 is sandwiched between the first frame 7a and the second frame 7f, and the polyolefin-based sheet 9 is supported by the frame 7.

First, the polyolefin sheet 9 is placed on the upper surface 7c of the first frame 7a. At this time, the position of the polyolefin-based sheet 9 is determined so as to close all the openings 7b of the first frame 7a. Next, the second frame 7f is placed on the polyolefin 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 hole 7i of the second frame 7f is fitted into the pin 7d of the first frame 7a.

When the first frame 7a and the second frame 7f are overlapped with each other, the magnetic force generated by the plurality of magnets 7e included in the first frame 7a acts to attract both frames to each other, and the outer peripheral portion of the polyolefin sheet 9 is formed. It is sandwiched between both frames. Therefore, the polyolefin-based sheet 9 is supported by the frame 7. At this time, since the pin 7d of the first frame 7a is fitted into the through hole 7i of the second frame 7f, the first frame 7a and the second frame 7f do not shift horizontally from each other.

Although the case where the frame support step is performed after the integration step has been described, the wafer processing method according to the present embodiment is not limited to this. For example, the integration step may be performed after the frame support step. In this case, the outer peripheral portion of the polyolefin-based sheet 9 is adhered to the first frame 7a and the second frame 7f by heating in the integration step, and the polyolefin-based 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 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 division process, and FIG. 6B is a cross-sectional view schematically showing the division process.

The laser processing apparatus 6 includes a laser processing unit 8 that irradiates the wafer 1 with the laser beam 10, and a chuck table (not shown) that holds the wafer 1. The laser processing unit 8 includes a laser oscillator (not shown) capable of oscillating a laser, and can emit a laser beam 10 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 8 irradiates the wafer 1 held on the chuck table with the laser beam 10 emitted from the laser oscillator. The processing head 8a included in the laser processing unit 8 has a mechanism for positioning the focusing point 8b of the laser beam 10 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 6. Further, the relative positions of the chuck table and the laser machining unit 8 are adjusted so that the machining head 8a is arranged above the extension line of the scheduled division line 3. Then, the focusing point 8b of the laser beam 10 is positioned at a predetermined height position.

Next, the chuck table and the laser processing unit 8 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 10 from the laser processing unit 8. That is, the condensing point 8b of the laser beam 10 is positioned inside the wafer 1, and the laser beam 10 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 10 in the dividing step are set as follows, for example. However, the irradiation conditions of the laser beam 10 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 8 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 laser processing unit 8 condenses the laser beam 10 inside the wafer 1 to form the modified layer 3a, the leaked light of the laser beam 10 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 10, 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 10 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. The pickup device 12 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 12.

The pickup device 12 includes a cylindrical drum 14 having a diameter larger than the diameter of the wafer 1 and a frame holding unit 16 including a frame support base 18. The frame support base 18 of the frame holding unit 16 has an opening having a diameter larger than the diameter of the drum 14, is arranged at the same height as the upper end of the drum 14, and the upper end of the drum 14 is on the outer peripheral side. Surround from.

A clamp 20 is arranged on the outer peripheral side of the frame support base 18. When the frame unit 11 is placed on the frame support base 18 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 18.

The frame support base 18 is supported by a plurality of rods 22 extending in the vertical direction, and an air cylinder 24 for raising and lowering the rods 22 is arranged at the lower end of each rod 22. The plurality of air cylinders 24 are supported by a disc-shaped base 26. When each air cylinder 24 is operated, the frame support base 18 is pulled down with respect to the drum 14.

Inside the drum 14, a push-up mechanism 28 that pushes up the device chip supported by the polyolefin-based sheet 9 from below is arranged. The push-up mechanism 28 includes a heating portion 28a including a heat source such as a Peltier element and a heating wire at the upper end. Further, a collet 30 (see FIG. 8B) capable of sucking and holding the device chip is arranged above the drum 14. The push-up mechanism 28 and the collet 30 can move in the horizontal direction along the upper surface of the frame support base 18. Further, the collet 30 is connected to the suction source 30a (see FIG. 8B) via the switching portion 30b (see FIG. 8B).

When expanding the polyolefin sheet 9, first, the air cylinder 24 is operated so that the height of the upper end of the drum 14 of the pickup device 12 and the height of the upper surface of the frame support 18 are substantially the same, and the frame support is expanded. Adjust the height of 18. For example, the height position of the upper surface of the frame support base 18 may be positioned at a height position lower than the upper end of the drum 14 by the thickness of the first frame 7a. Next, the frame unit 11 carried out from the laser processing device 6 is placed on the drum 14 of the pickup device 12.

After that, the frame 7 of the frame unit 11 is fixed on the frame support 18 by the clamp 20. FIG. 8A is a cross-sectional view schematically showing the frame unit 11 fixed on the frame support base 18. A modified layer 3a is formed inside the wafer 1 along the planned division line 3.

Next, the air cylinder 24 is operated to pull down the frame support base 18 of the frame holding unit 16 with respect to the drum 14. 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 28 is moved below the device chip 1c, and the collet 30 is moved above the device chip 1c.

After that, the heating unit 28a is operated to raise the temperature, and the heating unit 28a is brought into contact with the region corresponding to the device chip 1c of the polyolefin sheet 9 to heat the region. Further, the push-up mechanism 28 is operated to push up the device chip 1c from the polyolefin-based sheet 9 side. Then, the switching portion 30b is operated to communicate the collet 30 with the suction source 30a. Then, the device chip 1c is sucked and held by the collet 30, 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 heated by the heating unit 28a, for example, the region is heated to a temperature near the melting point of the polyolefin-based sheet 9. Since the adhesive strength of the polyolefin-based sheet 9 decreases while the temperature is close to the melting point, the load applied to the device chip when peeling from the polyolefin-based sheet 9 is reduced.

For example, when the frame unit 11 is formed using the adhesive tape, the leaked light of the laser beam 10 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 7,7a, 7f Frame 7b, 7g Opening 7c Top surface 7d pin 7e Magnet 7h Bottom surface 7i Through hole 9 Polyolefin sheet 11 Frame unit 2 Chuck table 2a Surface 2b, 30a Suction source 2c, 30b Switching part 4 Heat gun 4a Hot air 6 Laser processing device 8 Laser processing unit 8a Processing head 8b Condensing point 10 Laser beam 12 Pickup device 14 Drum 16 Frame holding unit 18 Frame support 20 Clamp 22 Rod 24 Air cylinder 26 Base 28 Push-up mechanism 28a Heating part 30 Collet

Claims (5)

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 arranging a polyolefin-based sheet on the back surface or the front surface of the wafer, and
An integration step of applying hot air to the polyolefin-based sheet to heat the polyolefin-based sheet and integrating the wafer and the polyolefin-based sheet.
Before or after the integration step, a first frame having an opening large enough to accommodate the wafer and having a plurality of magnets, and a second frame having an opening large enough to accommodate the wafer. Using a frame composed of, the outer peripheral portion of the polyolefin-based sheet is sandwiched between the first frame and the second frame by the magnetic force generated by the magnet to hold the polyolefin-based sheet. The frame support process of supporting with the frame and
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. , A division step of dividing the wafer into individual device chips,
In the individual region corresponding to each device chip of the polyolefin-based sheet, the polyolefin-based sheet is heated, 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 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 3, 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.