JP2020136374A - 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 on a surface into individual device chips comprises a polyolefin-based sheet arranging step, an integrating step, a frame supporting step, a dividing step, and a picking-up step. The polyolefin-based sheet arranging step arranges a polyolefin-based sheet on a rear surface of the wafer. The integrating step heats the polyolefin-based sheet by applying hot air to the polyolefin-based sheet, and integrates the wafer and the polyolefin-based sheet. The frame supporting step supports the polyolefin-based sheet by a frame composed of an inner frame including an opening having a size enough to house the wafer and an outer frame including an opening with a diameter corresponding to an outer diameter of the inner frame by holding an outer periphery of the polyolefin-based sheet between an outer peripheral wall of the inner frame and an inner peripheral wall of the outer frame using the frame. The dividing step divides the wafer into individual device chips. The picking-up step applies ultrasonic waves to the polyolefin-based sheet and pushes 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.

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 of the wafer, and the wafer, the adhesive tape, and the annular frame are integrated. Form a frame unit. 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 for dividing the wafer (see Patent Document 1). The laser processing apparatus includes a chuck table that holds the wafer via an adhesive tape, and a laser processing unit that irradiates the wafer with a laser beam having a wavelength that absorbs 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. When the laser beam is irradiated, a division groove is formed in the wafer along each planned division line by ablation, and the wafer is divided.

After that, the frame unit is taken out from the laser processing device, and the adhesive tape is subjected to a treatment such as irradiating ultraviolet rays to reduce the adhesive strength of the adhesive tape and pick up the device chip. 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). The device chip picked up from the adhesive tape is mounted on a predetermined wiring board or the like.

Japanese Unexamined Patent Publication No. 10-305420 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 the laser processing apparatus, in order to reliably divide the wafer by ablation processing, the laser beam is applied to the wafer under the condition that the dividing groove from the front surface to the back surface of the wafer can be reliably formed. Therefore, below and around the formed dividing groove, the glue layer of the adhesive tape melts due to the thermal effect of the irradiation of the laser beam, and a part of the glue layer is formed on the back surface side of the device chip formed from the wafer. Stick.

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 side of the picked up device chip. .. 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 of the present invention is that the glue layer does not adhere to the back surface side of the device chip to be formed, and the quality derived from the adhesion of the glue layer to the device chip. It is to provide a method of processing a wafer which does not cause deterioration.

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 back surface of the wafer is formed. A polyolefin-based sheet arranging step of arranging a polyolefin-based sheet, 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 frame composed of an inner frame having an opening large enough to accommodate the wafer and an outer frame having an opening having a diameter corresponding to the outer diameter of the inner frame is used. Then, a frame supporting step of supporting the polyolefin-based sheet with the frame by sandwiching the outer periphery of the polyolefin-based sheet between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame, and the wafer. A dividing step of irradiating the wafer with a laser beam having a wavelength capable of absorbing the polyolefin along the planned division line to form a dividing groove to divide the wafer into individual device chips, and a polyolefin-based sheet. In each region corresponding to each device chip, an ultrasonic wave is applied to the polyolefin-based sheet, the device chip is pushed up from the polyolefin-based sheet side, and the device chip is picked up from the polyolefin-based sheet. Provided is a method for processing a wafer, which comprises providing.

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 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.

In the wafer processing method according to one aspect of the present invention, a frame composed of an inner frame having an opening having a size capable of accommodating the wafer and an outer frame having an opening having a diameter corresponding to the outer diameter of the inner frame. Is used. Then, in the frame support step, the inner frame is inserted into the opening of the outer frame, and at this time, the polyolefin-based sheet is sandwiched between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame. The polyolefin-based 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 capable of absorbing the wafer, and a dividing groove is formed along the planned division line by ablation to divide the wafer. Then, in each region of the polyolefin-based sheet corresponding to each device chip, ultrasonic waves are applied to the polyolefin-based sheet, 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 ultrasonic waves are applied to the polyolefin-based sheet at the time of pickup, the polyolefin-based sheet can be easily peeled off, so that the load on the device chip can be reduced.

When the wafer is ablated, the heat generated by the irradiation of the laser beam is transferred to the polyolefin-based sheet below or near the dividing groove. However, since the polyolefin-based sheet does not have a glue layer, the glue layer does not melt and adhere to the back 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 side of the formed device chip and the quality does not deteriorate due to the adhesion of the glue layer to the device chip. ..

It is a perspective view which shows typically 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. 5A is a perspective view schematically showing a frame supporting process, and FIG. 5B is a perspective view schematically showing a formed frame unit. It is a perspective view which shows typically the division process. It is a perspective view which shows typically the carry-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. 1 is a perspective view schematically showing 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, the wafer 1 is divided by forming a dividing groove along the scheduled division line 3 on the wafer 1 by ablation processing to form individual device chips.

Before the wafer 1 is carried into the laser processing apparatus 6 (see FIG. 6) in which the ablation processing is performed, the wafer 1, the polyolefin-based sheet, and the frame are integrated to form a frame unit. The wafer 1 is carried into a laser processing apparatus in the state of a frame unit and processed. The individual device chips formed are supported by a polyolefin-based sheet. After that, the space between the device chips is widened by expanding the polyolefin-based sheet, and the device chips are picked up by the pickup device.

The annular frame 7 (see FIG. 5A and the like) corresponds to, for example, an inner frame 7c made of a material such as metal and having an opening large enough to accommodate the wafer 1 and an outer diameter of the inner frame 7c. It is composed of two members, an outer frame 7a having an opening having a diameter of the same. The inner frame 7c and the outer frame 7a have substantially the same height.

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 inner frame 7c 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 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 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 sheet 9 is adhered to the back surface 1b side of the wafer 1 by heating, and the outer peripheral portion of the polyolefin sheet 9 is the outer peripheral wall 7e of the inner frame 7c and the outer frame 7a. A frame unit is formed by sandwiching the inner peripheral wall 7b between the two.

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 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 surface 1a side of the wafer 1 is directed downward. Next, the polyolefin-based sheet 9 is arranged on the back surface 1b 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 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, 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 polyolefin-based sheet 9 is placed in the frame by sandwiching the outer periphery of the polyolefin-based sheet 9 between the outer peripheral wall 7e of the inner frame 7c of the frame 7 and the inner peripheral wall 7b of the outer frame 7a of the frame 7. Support with 7.

First, the polyolefin sheet 9 is placed on the inner frame 7c. At this time, the position of the polyolefin-based sheet 9 is determined so that the entire region on the upper surface of the inner frame 7c is covered with the polyolefin-based sheet 9. Next, the outer frame 7a is placed above the polyolefin sheet 9. At this time, the position of the outer frame 7a is determined so that the outer peripheral wall 7e of the inner frame 7c and the inner peripheral wall 7b of the outer frame 7a substantially overlap.

After that, the outer frame 7a placed above the polyolefin-based sheet 9 is pushed downward to accommodate the inner frame 7c in the opening of the outer frame 7a. At this time, the outer peripheral portion of the polyolefin-based sheet 9 is bent by the outer frame 7a and sandwiched between the outer peripheral wall 7e of the inner frame 7c and the inner peripheral wall 7b of the outer frame 7a. Then, as shown in FIG. 5B, the frame unit 11 in which the wafer 1, the polyolefin-based sheet 9, and the frame 7 are integrated is formed. In the frame unit 11, the polyolefin-based sheet 9 is arranged on the upper surface of the inner frame 7c of the frame 7.

Although the case where the frame support step is carried out 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 portion sandwiched between the inner frame 7c and the outer frame 7a of the frame 7 of the polyolefin sheet 9 by heating in the integration step is the outer peripheral wall 7e of the inner frame 7c and the inner peripheral wall 7b of the outer frame 7a. The polyolefin-based sheet 9 is supported by the frame 7 with a stronger force.

Further, the case where the polyolefin sheet 9 is arranged on the inner frame 7c of the frame 7 and the outer frame 7a is arranged on the polyolefin sheet 7a to carry out the frame support step has been described. However, the wafer processing method according to the present embodiment has been described. Then, the inner frame 7c and the outer frame 7a may be exchanged.

That is, the polyolefin sheet 9 may be arranged on the outer frame 7a, the inner frame 7c may be arranged on the outer frame 7a, and the inner frame 7c may be pressed from above to accommodate the inner frame 7c in the opening of the outer frame 7a. In this case, in the frame unit formed, the polyolefin sheet 9 is in contact with the lower surface of the inner frame 7c, and the wafer 1 is arranged in the opening surrounded by the inner peripheral wall 7d of the inner frame 7c.

Next, in the wafer 1 processing method according to the present embodiment, the wafer 1 in the state of the frame unit 11 is ablated to form a dividing groove along the scheduled division line 3 to divide the wafer 1. Carry out the division process. The dividing step is carried out, for example, by the laser processing apparatus shown in FIG. FIG. 6 is a perspective view schematically showing the division process.

The laser processing apparatus 6 includes a laser processing unit 8 that ablates the wafer 1 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 (wavelength that the wafer 1 can absorb) having absorbency with respect to 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 condensing the laser beam 10 at a predetermined height position on the wafer 1.

When the wafer 1 is ablated, 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. Then, the chuck table is rotated to align the scheduled division line 3 of the wafer 1 with the processing feed direction of the laser processing apparatus 6. Further, the relative positions of the chuck table and the laser processing unit 8 are adjusted so that the processing head 8a is arranged above the extension line of the scheduled division line 3.

Next, while irradiating the wafer 1 with the laser beam 10 from the laser processing unit 8, 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. Then, the laser beam 10 is irradiated to the wafer 1 along the scheduled division line 3, and the dividing groove 3a along the scheduled division line 3 is formed on the wafer 1 by ablation.

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: 355 nm
Repeat frequency: 50kHz
Average output: 5W
Feed rate: 200 mm / sec

After performing ablation processing along one scheduled division line 3, the chuck table and the laser processing unit 8 are moved relative to the indexing feed direction perpendicular to the processing feed direction, and along the other scheduled division lines 3. Similarly, the wafer 1 is ablated. After forming the split groove 3a along all the scheduled split lines 3 along one direction, the chuck table is rotated around the axis perpendicular to the holding surface and along the scheduled split lines 3 along the other direction. Similarly, the wafer 1 is ablated.

When the wafer 1 is ablated along all the planned division lines 3 of the wafer 1, the division process is completed. When the dividing step is completed and the dividing grooves 3a from the front surface 1a to the back surface 1b are formed on the wafer 1 along all the scheduled division lines 3, the wafer 1 is divided and individual device chips are formed.

When the wafer 1 is ablated by the laser processing unit 8, processing debris derived from the wafer 1 is generated from the irradiated portion of the laser beam 10, and the processing debris is scattered around the irradiated portion of the wafer 1. It adheres to the surface 1a. Even if the surface 1a of the wafer 1 is cleaned by the cleaning unit described later after the wafer 1 is ablated, it is not easy to completely remove the adhering processing chips. If the work chips remain on the device chip formed from the wafer 1, the quality of the device chip deteriorates.

Therefore, the surface 1a of the wafer 1 to be ablated by the laser processing apparatus 6 may be previously coated with a water-soluble liquid resin that functions as a protective film that protects the surface 1a of the wafer 1. When the liquid resin is applied to the surface 1a of the wafer 1, the processing chips scattered when performing the ablation processing adhere to the upper surface of the liquid resin, so that the processing chips do not directly adhere to the surface 1a of the wafer 1. .. Then, the processing waste is removed together with the liquid resin by the cleaning unit described below.

The laser processing apparatus 6 may include a cleaning unit (not shown). In this case, the wafer 1 ablated by the laser processing unit 8 is conveyed to the cleaning unit and cleaned by the cleaning unit. For example, the cleaning unit includes a cleaning table that holds the frame unit 11 and a cleaning water supply nozzle that can reciprocate above the frame unit 11.

The cleaning table is rotated around an axis perpendicular to the holding surface, and while supplying cleaning liquid such as pure water from the cleaning water supply nozzle to the wafer 1, the cleaning water supply nozzle is horizontal in a path passing above the center of the holding surface. By reciprocating in the direction, the surface 1a side of the wafer 1 can be cleaned.

In the wafer 1 processing method according to the present embodiment, a pickup step of picking up the individual device chips from the polyolefin-based sheet 9 is then carried out. In the pickup process, the pickup device 12 shown in the lower part of FIG. 7 is used. 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. Further, the frame support base 18 has an outer diameter having a size corresponding to the diameter of the opening of the inner frame 7c constituting the frame 7 of the frame unit 11.

Further, for example, a plurality of suction holes 18a are provided on the outer peripheral wall of the frame support base 18. The frame support base 18 can apply a negative pressure to the inner frame 7c of the frame 7 located on the outer peripheral side of the frame support base 18 through the suction holes 18a. When the frame unit 11 is placed on the frame support base 18 and a negative pressure is applied to the inner frame 7c of the frame 7, the frame unit 11 is fixed to the frame support base 18.

The frame support base 18 is supported by a plurality of rods 20 extending in the vertical direction, and an air cylinder 22 for raising and lowering the rods 20 is arranged at the lower end of each rod 20. The plurality of air cylinders 22 are supported by a disk-shaped base 24. When each air cylinder 22 is operated, the frame support base 18 is pulled down with respect to the drum 14.

Inside the drum 14, a push-up mechanism 26 for pushing up the device chip supported by the polyolefin-based sheet 9 from below is arranged. The push-up mechanism 26 includes, for example, an ultrasonic vibrator 26a made of piezoelectric ceramics such as lead zirconate titanate (PZT), barium titanate, lead titanate, or a crystal oscillator at the upper end. Further, a collet 28 (see FIG. 8B) capable of sucking and holding the device chip is arranged above the drum 14. The push-up mechanism 26 and the collet 28 are movable in the horizontal direction along the upper surface of the frame support base 18. Further, the collet 28 is connected to the suction source 28a (see FIG. 8B) via the switching portion 28b (see FIG. 8B).

In the pickup process, first, the height of the frame support 18 is adjusted by operating the air cylinder 22 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 match. To do. Next, the frame unit 11 carried out from the laser processing device 6 is placed on the drum 14 of the pickup device 12. At this time, the frame support base 18 is inserted into the opening of the inner frame 7c of the frame 7, and the inner peripheral wall 7d of the inner frame 7c is made to face the outer peripheral wall of the frame support base 18.

After that, a negative pressure is applied from the suction hole 18a of the frame support base 18 to the inner frame 7c of the frame 7 to fix the frame 7 of the frame unit 11 on the frame support base 18. FIG. 8A is a cross-sectional view schematically showing the frame unit 11 fixed on the frame support base 18. A dividing groove 3a is formed and divided in the wafer 1 by a dividing step.

Next, the air cylinder 22 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 in the outer peripheral direction. FIG. 8B is a cross-sectional view schematically showing the pickup process.

When the polyolefin-based sheet 9 is expanded in the outer peripheral direction, the distance between the device chips 1c supported by the polyolefin-based sheet 9 is widened. Then, the device chips 1c are less likely to come into contact with each other, and the individual device chips 1c can be easily picked up. Then, the device chip 1c to be picked up is determined, the push-up mechanism 26 is moved below the device chip 1c, and the collet 28 is moved above the device chip 1c.

After that, the ultrasonic vibrator 26a is operated to generate vibration at a frequency in the ultrasonic band, and the ultrasonic vibrator 26a is brought into contact with the region corresponding to the device chip 1c of the polyolefin sheet 9 to generate ultrasonic waves in the region. Is given. Further, the push-up mechanism 26 is operated to push up the device chip 1c from the polyolefin-based sheet 9 side. Then, the switching portion 28b is operated to communicate the collet 28 with the suction source 28a. Then, the device chip 1c is sucked and held by the collet 28, 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 ultrasonic waves are applied to the region of the polyolefin-based sheet 9 by the ultrasonic vibrator 26a, the polyolefin-based sheet 9 can be easily peeled off. 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 using the adhesive tape, the heat generated by the irradiation of the laser beam 10 in the dividing step is transferred to the adhesive tape, and the glue layer of the adhesive tape is melted and fixed to the back surface side of the device chip. To do. 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, it is possible to form a frame unit using a polyolefin sheet without a glue layer by thermocompression bonding, so that an adhesive tape having a glue layer is unnecessary. Is. 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 the scope of the object of the present invention is not deviated.

1 Wafer 1a Front surface 1b Back surface 3 Scheduled division line 3a Division groove 5 Device 7 frame 7a Outer frame 7b, 7d Inner peripheral wall 7c Inner frame 7e Outer wall 9 Polyolefin sheet 11 Frame unit 2 Chuck table 2a Holding surface 2b, 28a , 28b Switching part 4 Heat gun 4a Hot air 6 Laser processing device 8 Laser processing unit 8a Processing head 10 Laser beam 12 Pickup device 14 Drum 16 Frame holding unit 18 Frame support 18a Suction hole 20 Rod 22 Air cylinder 24 Base 26 Push-up mechanism 26a Super Sonic oscillator 28 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 process for arranging a polyolefin-based sheet on the back 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 frame composed of an inner frame having an opening large enough to accommodate the wafer and an outer frame having an opening having a diameter corresponding to the outer diameter of the inner frame is used. A frame support step of supporting the polyolefin-based sheet with the frame by sandwiching the outer periphery of the polyolefin-based sheet between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame.
A division step of irradiating the wafer with a laser beam having a wavelength capable of absorbing the wafer along the planned division line to form a division groove and dividing the wafer into individual device chips.
In the individual region corresponding to each device chip of the polyolefin-based sheet, ultrasonic waves are applied to the polyolefin-based sheet, the device chip is pushed up from the polyolefin-based sheet side, and the device chip is picked up from the polyolefin-based sheet. Pickup process and
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.

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