Wafer processing method

Abstract

A wafer processing method is provided to form device chips without compromising quality. This wafer processing method divides a wafer, in which multiple devices are formed in different areas of the front side divided by a predetermined dicing line, into individual device chips. The wafer processing method includes the following steps: a polyolefin sheet placement step, in which the wafer is positioned within an opening in a frame having an opening for receiving the wafer, and a polyolefin sheet is placed on the back side of the wafer and the outer periphery of the frame; an integration step, in which the polyolefin sheet is heated and thermo-pressed to integrate the wafer and the frame using the polyolefin sheet; a dicing step, in which a laser beam of a wavelength absorbent to the wafer is irradiated along the predetermined dicing line to form dicing grooves and divide the wafer into individual device chips; and a pick-up step, in which air is blown to lift the device chips and pick up each device chip from the polyolefin sheet.

Description

Technical Field

[0001] The present invention relates to a wafer processing method for dividing a wafer divided by a predetermined dividing line and having a plurality of devices formed in each area on the front side into individual device chips. Background Art

[0002] In the manufacturing process of device chips for electronic devices such as mobile phones and personal computers, a plurality of intersecting predetermined division lines (streets) are first set on the front side of a wafer made of materials such as semiconductors, and devices such as ICs (Integrated Circuits), LSIs (Large-Scale Integration Circuits), and LEDs (Light Emitting Diodes) are formed in each area divided by the predetermined division lines.

[0003] Then, an adhesive tape called a dicing tape is pasted on the back of the wafer so as to seal the opening of the ring-shaped frame, thereby forming a frame unit in which the wafer, the adhesive tape and the ring-shaped frame are integrated. When the wafer included in the frame unit is processed and divided along the predetermined dividing line, individual device chips are formed.

[0004] For example, a laser processing device is used to divide the wafer (see Patent Document 1). The laser processing device 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 is absorbent to the wafer.

[0005] When dividing a wafer, the frame unit is placed on the chuck table, and the wafer is held on the chuck table via an adhesive tape. Then, while the chuck table and the laser processing unit are relatively moved in a direction parallel to the upper surface of the chuck table, the laser beam is irradiated from the laser processing unit to the wafer. When the laser beam is irradiated, dividing grooves are formed on the wafer along each predetermined dividing line by ablation, and the wafer is divided.

[0006] Then, the frame unit is removed from the laser processing device, and the adhesive tape is subjected to treatment such as ultraviolet irradiation to reduce the adhesive force of the adhesive tape, and the device chip is picked up. As a processing device with high production efficiency of device chips, a processing device that can continuously perform wafer segmentation and ultraviolet irradiation on the adhesive tape using one device is known (see Patent Document 2). The device chip picked up from the adhesive tape is mounted on a predetermined wiring substrate, etc.

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 10-305420

[0008] Patent Document 2: Japanese Patent No. 3076179

[0009] The adhesive tape includes, for example, a base layer formed of a vinyl chloride sheet or the like and a paste layer disposed on the base layer. In a laser processing device, in order to reliably divide the wafer by ablation processing, the wafer is irradiated with a laser beam under conditions that can reliably form a dividing groove from the front side to the back side of the wafer. Therefore, under and around the formed dividing groove, the paste layer of the adhesive tape melts due to the influence of heat brought about by the irradiation of the laser beam, and a part of the paste layer is adhered to the back side of the device chip formed from the wafer.

[0010] In this case, when the device chip is picked up from the adhesive tape, even if the adhesive tape is subjected to treatment such as ultraviolet irradiation, a portion of the paste layer remains on the back side of the picked up device chip, thus causing a problem of reduced quality of the device chip. Summary of the invention

[0011] The present invention has been made in view of the above problem, and an object of the present invention is to provide a wafer processing method that does not cause a paste layer to adhere to the back side of a formed device chip and does not cause a quality degradation due to adhesion of the paste layer to the device chip.

[0012] According to one embodiment of the present invention, a method for processing a wafer is provided, wherein a wafer having a plurality of devices formed in respective regions on the front side divided by a predetermined dividing line is divided into individual device chips, and the method for processing the wafer comprises the following steps: a polyolefin sheet placement step, wherein the wafer is positioned in an opening of a frame having an opening for accommodating the wafer, and the polyolefin sheet is placed on the back side of the wafer and on the periphery of the frame; an integration step, wherein the polyolefin sheet is heated and the wafer and the frame are integrated with the polyolefin sheet by thermal compression; a partitioning step, wherein a laser beam having a wavelength that is absorptive to the wafer is irradiated along the predetermined dividing line to form a partitioning groove to partition the wafer into individual device chips; and a picking-up step, wherein air is blown from the side of the polyolefin sheet to lift up the device chips one by one, and the device chips are picked up from the polyolefin sheet.

[0013] In the integration step, the thermocompression bonding is preferably performed by irradiation with infrared rays.

[0014] Furthermore, in the integration step, it is preferred that the polyolefin-based sheet protruding from the outer periphery of the frame is removed after the integration is performed.

[0015] Furthermore, in the pickup step, it is preferred that the polyolefin-based sheet be expanded to increase the interval between the device chips.

[0016] In addition, the polyolefin-based sheet is preferably any of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet.

[0017] In addition, in the integration step, it is preferred that when the polyolefin sheet is the polyethylene sheet, the heating temperature is 120°C to 140°C, when the polyolefin sheet is the polypropylene sheet, the heating temperature is 160°C to 180°C, and when the polyolefin sheet is the polystyrene sheet, the heating temperature is 220°C to 240°C.

[0018] In addition, it is preferable that the wafer is made of any material among Si, GaN, GaAs and glass.

[0019] In a wafer processing method according to one embodiment of the present invention, when forming a frame unit, a polyolefin sheet without a paste layer is used instead of an adhesive tape with a paste layer to integrate the frame and the wafer. The integration step of integrating the frame and the wafer with the polyolefin sheet is achieved by thermocompression bonding.

[0020] After the integration process is performed, the wafer is irradiated with a laser beam of a wavelength that is absorbent to the wafer, and the wafer is divided by ablation to form a dividing groove along the predetermined dividing line. Then, air is blown from the polyolefin sheet side to lift up the device chips one by one, and the device chips are picked up from the polyolefin sheet. The picked up device chips are respectively installed on the specified installation objects. In addition, when the device chips are lifted up by air during picking up, the load applied to the device chips when peeling from the polyolefin sheet can be reduced.

[0021] When the wafer is subjected to ablation, the heat generated by the laser beam irradiation is transferred to the polyolefin sheet below and near the dividing grooves. However, the polyolefin sheet does not have a paste layer, so the paste layer does not melt and adhere to the back side of the device chip.

[0022] That is, according to one embodiment of the present invention, the frame unit can be formed using a polyolefin-based sheet without a paste layer, so an adhesive tape with a paste layer is not required, and as a result, the quality of the device chip is not degraded due to adhesion of the paste layer.

[0023] Therefore, according to one embodiment of the present invention, there is provided a wafer processing method in which a paste layer is not attached to the back side of a formed device chip, and quality degradation due to the attachment of the paste layer to the device chip is not caused. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a perspective view schematically showing a wafer.

[0025] Figure 2It is a perspective view schematically showing a state where a wafer and a frame are positioned on a holding surface of a chuck table.

[0026] Figure 3 It is a perspective view schematically showing the polyolefin-based sheet disposing step.

[0027] Figure 4 It is a perspective view schematically showing an example of the integration process.

[0028] Figure 5 It is a perspective view schematically showing another example of the integration process.

[0029] Figure 6 This is a perspective view schematically showing another example of the integration process.

[0030] Figure 7 (A) is a perspective view schematically showing a state where a polyolefin-based sheet is cut. Figure 7 (B) is a perspective view schematically showing the formed frame unit.

[0031] Figure 8 It is a perspective view schematically showing the dividing step.

[0032] Fig. 9 It is a perspective view schematically showing the loading of the frame unit into the pickup device.

[0033] Fig.10 (A) is a cross-sectional view schematically showing a frame unit fixed to a frame support platform, Fig.10 (B) is a cross-sectional view schematically showing the picking-up process.

[0034] Description of symbols

[0035] 1: wafer; 1a: front side; 1b: back side; 3: predetermined dividing line; 3a: dividing groove; 5: device; 7: frame; 7a: opening; 9: polyolefin sheet; 9a: cutting mark; 11: frame unit; 2: chuck table; 2a: holding surface; 2b, 36a: suction source; 2c, 36b: switching part; 4: hot air gun; 4a: hot air; 6: heating roller; 8: infrared lamp; 8a: infrared; 10: cutter; 12: laser processing device; 14: laser processing unit; 14a: processing head; 16: laser beam; 18: picking device; 20: drum; 22: frame holding unit; 24: clamp; 26: frame support platform; 28: rod; 30: cylinder; 32: base; 34: lifting mechanism; 34a: air; 36: collet. DETAILED DESCRIPTION

[0036] An embodiment of one mode of the present invention will be described with reference to the drawings. First, a wafer processed by the wafer processing method of the present embodiment will be described. Figure 1 1 is a perspective view schematically showing the wafer 1 .

[0037] The wafer 1 is a generally disk-shaped substrate made of materials such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide) or other semiconductors, or sapphire, glass, quartz, etc. The glass is, for example, alkali glass, alkali-free glass, soda-lime glass, lead glass, borosilicate glass, quartz glass, etc.

[0038] The front side 1a of the wafer 1 is divided by a plurality of predetermined dividing lines 3 arranged in a grid. In addition, devices 5 such as IC, LSI, LED, etc. are formed in each area divided by the predetermined dividing lines 3 on the front side 1a of the wafer 1. In the processing method of the wafer 1 of the present embodiment, the wafer 1 is divided by forming dividing grooves along the predetermined dividing lines 3 on the wafer 1 by ablation processing, thereby forming individual device chips.

[0039] When the wafer 1 is loaded into the laser processing device 12 (see Figure 8 ), the wafer 1, the polyolefin sheet and the frame are integrated to form a frame unit. The wafer 1 is carried into the laser processing device in the state of the frame unit for processing. Each device chip formed is supported by the polyolefin sheet. Then, the polyolefin sheet is expanded to expand the interval between the device chips, and the device chip is picked up by the pickup device.

[0040] The annular frame 7 (see Figure 2 The frame 7 is formed of a material such as metal, and has an opening 7a having a diameter larger than that of the wafer 1. When forming the frame unit, the wafer 1 is positioned in the opening 7a of the frame 7 and accommodated in the opening 7a.

[0041] Polyolefin sheet 9 (refer to Figure 3 The polyolefin sheet 9 is a flexible resin sheet with flat front and back surfaces. In addition, the polyolefin sheet 9 has a diameter larger than the outer diameter of the frame 7 and does not have a paste layer. The polyolefin sheet 9 is a sheet of a polymer synthesized using olefin as a monomer, such as a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet that is transparent or translucent to visible light. However, the polyolefin sheet 9 is not limited thereto and may be opaque.

[0042] The polyolefin sheet 9 has no adhesiveness and therefore cannot be attached to the wafer 1 and the frame 7 at room temperature. However, the polyolefin sheet 9 has thermoplasticity, and therefore, when the polyolefin sheet 9 is heated to a temperature near the melting point while being bonded to the wafer 1 and the frame 7 under a predetermined pressure, the polyolefin sheet 9 partially melts and can be bonded to the wafer 1 and the frame 7. Therefore, in the processing method of the wafer 1 of the present embodiment, the wafer 1, the frame 7, and the polyolefin sheet 9 are integrated by the above-mentioned thermocompression bonding to form a frame unit.

[0043] Next, each step of the method for processing the wafer 1 of the present embodiment will be described. First, a polyolefin-based sheet placement step is performed in order to prepare for integrating the wafer 1 , the polyolefin-based sheet 9 , and the frame 7 . Figure 2 2 is a perspective view schematically showing the state where the wafer 1 and the frame 7 are positioned on the holding surface 2a of the chuck table 2. Figure 2 As shown, the polyolefin sheet placement step is performed on a chuck table 2 having a holding surface 2a on the upper portion.

[0044] The chuck table 2 has a porous member at the center of the upper portion, the diameter of which is larger than the outer diameter of the frame 7. The upper surface of the porous member serves as a holding surface 2a of the chuck table 2. Figure 3 As shown, there is an exhaust path with one end connected to the porous component, and a suction source 2b is arranged on the other end side of the exhaust path. A switching part 2c for switching between a connected state and a disconnected state is arranged on the exhaust path. When the switching part 2c is in the connected state, a negative pressure generated by the suction source 2b acts on the object to be held placed on the holding surface 2a, so that the object to be held is sucked and held on the chuck worktable 2.

[0045] In the polyolefin sheet preparation process, first Figure 2 As shown, a wafer 1 and a frame 7 are placed on the holding surface 2a of the chuck table 2. At this time, the front surface 1a of the wafer 1 is directed downward and the wafer 1 is positioned in the opening 7a of the frame 7. Next, a polyolefin sheet 9 is disposed on the back surface 1b of the wafer 1 and the outer periphery of the frame 7. Figure 3 2 is a perspective view schematically showing the polyolefin sheet arrangement process. Figure 3 As shown, a polyolefin-based sheet 9 is disposed on the wafer 1 and the frame 7 so as to cover both.

[0046] In addition, in the polyolefin sheet placement step, a polyolefin sheet 9 having a larger diameter than the holding surface 2a of the chuck table 2 is used. This is because, when the negative pressure of the chuck table 2 is applied to the polyolefin sheet 9 in the subsequent integration step, if the entire holding surface 2a is not covered by the polyolefin sheet 9, the negative pressure leaks from the gap, and the polyolefin sheet 9 cannot be properly pressed.

[0047] In the processing method of the wafer 1 of the present embodiment, an integration step is then performed to heat the polyolefin-based sheet 9 and integrate the wafer 1 and the frame 7 via the polyolefin-based sheet 9 by thermocompression bonding. Figure 4 FIG. 1 is a perspective view schematically showing an example of an integration process. Figure 4 In FIG. 1 , components that can be viewed through the polyolefin-based sheet 9 that is transparent or translucent to visible light are indicated by dotted lines.

[0048] In the integration process, first, the switching unit 2c of the chuck table 2 is operated to establish a communication state in which the suction source 2b is connected to the porous member on the upper portion of the chuck table 2, and the negative pressure of the suction source 2b is applied to the polyolefin sheet 9. Thus, the polyolefin sheet 9 is brought into close contact with the wafer 1 and the frame 7 by atmospheric pressure.

[0049] Next, the polyolefin sheet 9 is heated while being sucked by the suction source 2b, and thermocompression bonding is performed. The polyolefin sheet 9 is heated, for example, Figure 4 As shown, the hot air gun 4 is provided above the chuck table 2 to implement the process.

[0050] The hot air gun 4 has a heating unit such as an electric heating wire and an air supply mechanism such as a fan inside, and can heat the air and spray it. While applying negative pressure to the polyolefin sheet 9, the hot air gun 4 provides hot air 4a to the polyolefin sheet 9 from the upper surface. When the polyolefin sheet 9 is heated to a predetermined temperature, the polyolefin sheet 9 is thermally pressed and bonded to the wafer 1 and the frame 7.

[0051] The polyolefin-based sheet 9 may be heated by other methods, for example, by pressing the wafer 1 and the frame 7 from above using a member heated to a predetermined temperature. Figure 5 FIG. 1 is a perspective view schematically showing another example of the integration process. Figure 5 In FIG. 1 , components that can be viewed through the polyolefin-based sheet 9 that is transparent or translucent to visible light are indicated by dotted lines.

[0052] exist Figure 5 In the integrated process shown, for example, a heating roller 6 having a heat source inside is used. Figure 5 In the integration step shown, the negative pressure of the suction source 2b is also first applied to the polyolefin sheet 9, and the polyolefin sheet 9 is brought into close contact with the wafer 1 and the frame 7 by the atmospheric pressure.

[0053] Then, the heating roller 6 is heated to a predetermined temperature and placed on one end of the holding surface 2a of the chuck table 2. Then, the heating roller 6 is rotated and rolled on the chuck table 2 from the one end to the other end. Thus, the polyolefin sheet 9 is thermally pressed and bonded to the wafer 1 and the frame 7. At this time, when a force is applied in a direction to press the polyolefin sheet 9 downward by the heating roller 6, thermal pressing is performed using a pressure greater than atmospheric pressure. In addition, it is preferable that the surface of the heating roller 6 is coated with a fluororesin.

[0054] Alternatively, an iron-shaped pressing member having a heat source inside and a flat bottom plate may be used instead of the heating roller 6 to perform thermocompression bonding of the polyolefin sheet 9. In this case, the pressing member is heated to a predetermined temperature to become a hot plate, and the polyolefin sheet 9 held by the chuck table 2 is pressed from above by the pressing member.

[0055] The polyolefin-based sheet 9 may be heated by other methods. Figure 6 FIG. 1 is a perspective view schematically showing another example of the integration process. Figure 6 In FIG. 1 , the parts that can be seen through the polyolefin sheet 9 that is transparent or translucent to visible light are indicated by dotted lines. Figure 6 In the integration step shown, the polyolefin sheet 9 is heated using an infrared lamp 8 disposed above the chuck table 2. The infrared lamp 8 can irradiate at least infrared rays 8a of a wavelength that the material of the polyolefin sheet 9 has absorption properties.

[0056] exist Figure 6 In the integration process shown, the negative pressure of the suction source 2b is first applied to the polyolefin sheet 9, so that the polyolefin sheet 9 is closely attached to the wafer 1 and the frame 7. Then, the infrared lamp 8 is operated to irradiate the polyolefin sheet 9 with infrared rays 8a to heat the polyolefin sheet 9. Thus, the polyolefin sheet 9 is thermally pressed onto the wafer 1 and the frame 7.

[0057] When the polyolefin sheet 9 is heated to a temperature near its melting point by any method, the polyolefin sheet 9 is thermocompressed and bonded to the wafer 1 and the frame 7. After the polyolefin sheet 9 is thermocompressed, the switching unit 2c is operated to release the connection between the porous member of the chuck table 2 and the suction source 2b, thereby releasing the adsorption of the chuck table 2.

[0058] Next, the polyolefin-based sheet 9 protruding from the outer periphery of the frame 7 is cut and removed. Figure 7 (A) is a perspective view schematically showing the cutting of the polyolefin sheet 9. Figure 7 As shown in (A), a ring-shaped cutter 10 is used. The cutter 10 has a through hole and can rotate around a rotation axis passing through the through hole.

[0059] First, the annular cutter 10 is positioned above the frame 7. At this time, the rotation axis of the cutter 10 is aligned with the radial direction of the chuck table 2. Next, the cutter 10 is lowered, and the polyolefin sheet 9 is sandwiched between the frame 7 and the cutter 10 to cut the polyolefin sheet 9. As a result, a cut mark 9a is formed on the polyolefin sheet 9.

[0060] In addition, the cutter 10 is made to go around the opening 7a of the frame 7 along the frame 7, and a predetermined area of ​​the polyolefin sheet 9 is surrounded by the cut mark 9a. Then, the polyolefin sheet 9 in the area on the outer peripheral side of the cut mark 9a is removed so that the polyolefin sheet 9 remains in the area. Thus, the unnecessary part of the polyolefin sheet 9 including the area protruding from the outer periphery of the frame 7 can be removed.

[0061] In addition, an ultrasonic cutter may be used to cut the polyolefin sheet, and a vibration source that causes the annular cutter 10 to vibrate at a frequency of an ultrasonic frequency band may be connected to the cutter 10. In addition, when the polyolefin sheet 9 is cut, the polyolefin sheet 9 may be cooled and hardened to facilitate cutting. As described above, the frame unit 11 in which the wafer 1 and the frame 7 are integrated via the polyolefin sheet 9 is formed. Figure 7 (B) is a perspective view schematically showing the formed frame unit 11 .

[0062] In addition, when performing heat compression bonding, the polyolefin sheet 9 is preferably heated to a temperature below its melting point. This is because, when the heating temperature exceeds the melting point, the polyolefin sheet 9 sometimes melts and cannot maintain the shape of the sheet. In addition, the polyolefin sheet 9 is preferably heated to a temperature above its softening point. This is because, if the heating temperature does not reach the softening point, heat compression bonding cannot be properly performed. That is, the polyolefin sheet 9 is preferably heated to a temperature above its softening point and below its melting point.

[0063] In addition, some polyolefin-based sheets 9 may not have a clear softening point. Therefore, when performing thermocompression bonding, the polyolefin-based sheet 9 is preferably heated to a temperature that is 20° C. lower than its melting point and is not higher than its melting point.

[0064] When the polyolefin sheet 9 is a polyethylene sheet, the heating temperature is preferably 120° C. to 140° C. When the polyolefin sheet 9 is a polypropylene sheet, the heating temperature is preferably 160° C. to 180° C. When the polyolefin sheet 9 is a polystyrene sheet, the heating temperature is preferably 220° C. to 240° C.

[0065] Here, the heating temperature refers to the temperature of the polyolefin sheet 9 when the integration process is performed. For example, among the heat sources such as the hot air gun 4, the heating roller 6, and the infrared lamp 8, a type capable of setting the output temperature is actually used, but even if the polyolefin sheet 9 is heated using the heat source, the temperature of the polyolefin sheet 9 may not reach the set output temperature. Therefore, in order to heat the polyolefin sheet 9 to a predetermined temperature, the output temperature of the heat source may be set higher than the melting point of the polyolefin sheet 9.

[0066] Next, in the wafer processing method of the present embodiment, a dividing step is performed to perform ablation processing on the wafer 1 in the state of the frame unit 11 to form dividing grooves along the planned dividing line 3 and divide the wafer 1. The dividing step is performed by, for example, Figure 8 The laser processing device shown is used for implementation. Figure 8 It is a perspective view schematically showing the dividing step.

[0067] The laser processing device 12 includes: a laser processing unit 14 for ablation processing on the wafer 1; and a chuck table (not shown) for holding the wafer 1. The laser processing unit 14 includes a laser oscillator (not shown) capable of oscillating laser light, and can emit a laser beam 16 having a wavelength that is absorptive to the wafer 1 (a wavelength that can be absorbed by the wafer 1). The chuck table can move in a direction parallel to the upper surface (processing feed).

[0068] The laser processing unit 14 irradiates the laser beam 16 emitted from the laser oscillator to the wafer 1 held by the chuck table. The processing head 14 a included in the laser processing unit 14 has a function of converging the laser beam 16 at a predetermined height position of the wafer 1 .

[0069] When ablation processing is performed on the wafer 1, the frame unit 11 is placed on the chuck table to hold the wafer 1 on the chuck table via the polyolefin sheet 9. Then, the chuck table is rotated to align the predetermined dividing line 3 of the wafer 1 with the processing feed direction of the laser processing device 12. In addition, the relative positions of the chuck table and the laser processing unit 14 are adjusted so that the processing head 14a is arranged above the extension line of the predetermined dividing line 3.

[0070] Next, the chuck table and the laser processing unit 14 are relatively moved in a processing feed direction parallel to the upper surface of the chuck table while the laser beam 16 is irradiated from the laser processing unit 14 to the wafer 1. Thus, the laser beam 16 is irradiated to the wafer 1 along the predetermined dividing line 3, and a dividing groove 3a along the predetermined dividing line 3 is formed on the wafer 1 by ablation.

[0071] The irradiation conditions of the laser beam 16 in the dividing step are set, for example, as follows. However, the irradiation conditions of the laser beam 16 are not limited thereto.

[0072] Wavelength: 355nm

[0073] Repetition frequency: 50kHz

[0074] Average output: 5W

[0075] Feed speed: 200mm / sec

[0076] After the ablation process is performed along one predetermined dividing line 3, the chuck table and the laser processing unit 14 are relatively moved in the indexing feed direction perpendicular to the processing feed direction, and the ablation process of the wafer 1 is similarly performed along the other predetermined dividing lines 3. After the dividing grooves 3a are formed along all the predetermined dividing lines 3 along one direction, the chuck table is rotated about an axis perpendicular to the holding surface, and the wafer 1 is similarly ablated along the predetermined dividing lines 3 along another direction.

[0077] The separation step is completed when the wafer 1 is ablated along all the predetermined separation lines 3 of the wafer 1. When the separation step is completed and the separation grooves 3a from the front surface 1a to the back surface 1b are formed on the wafer 1 along all the predetermined separation lines 3, the wafer 1 is separated into individual device chips.

[0078] When the wafer 1 is subjected to ablation processing by the laser processing unit 14, processing debris originating from the wafer 1 is generated from the portion irradiated by the laser beam 16, and the processing debris is scattered around the irradiated portion and adheres to the front surface 1a of the wafer 1. Even if the front surface 1a of the wafer 1 is cleaned by the cleaning unit described later after the ablation processing is performed on the wafer 1, it is not easy to completely remove the attached processing debris. When the processing debris remains on the device chip formed from the wafer 1, the quality of the device chip is reduced.

[0079] Therefore, a water-soluble liquid resin that functions as a protective film for protecting the front surface 1a of the wafer 1 may be applied in advance to the front surface 1a of the wafer 1 to be ablated by the laser processing device 12. When the liquid resin is applied to the front surface 1a of the wafer 1, the processing chips that fly when the ablation process is performed adhere to the upper surface of the liquid resin, so the processing chips do not directly adhere to the front surface 1a of the wafer 1. And, the processing chips are removed together with the liquid resin by the cleaning unit described below.

[0080] The laser processing device 12 may include a cleaning unit (not shown). In this case, the wafer 1 ablated by the laser processing unit 14 may be transported to the cleaning unit and cleaned by the cleaning unit. For example, the cleaning unit includes: a cleaning workbench that holds the frame unit 11; and a cleaning water supply nozzle that can reciprocate above the frame unit 11.

[0081] When the cleaning workbench is rotated around an axis perpendicular to the holding surface and a cleaning liquid such as pure water is supplied to the chip 1 from a cleaning water supply nozzle, and the cleaning water supply nozzle is reciprocated in a horizontal direction on a path passing above the center of the holding surface, the front side 1a of the chip 1 can be cleaned.

[0082] In the processing method of the wafer 1 of the present embodiment, a pick-up step is then performed to pick up each device chip from the polyolefin sheet 9. In the pick-up step, the device chip is picked up by using the Fig. 9 The pick-up device 18 is shown at the bottom. Fig. 9 It is a perspective view schematically showing the loading of the frame unit 11 into the pickup device 18 .

[0083] The pickup device 18 includes a cylindrical drum 20 having a diameter larger than that of the wafer 1, and a frame holding unit 22 including a frame support table 26. The frame support table 26 of the frame holding unit 22 has an opening having a diameter larger than that of the drum 20, is arranged at the same height as the upper end of the drum 20, and surrounds the upper end of the drum 20 from the outer peripheral side.

[0084] The jig 24 is disposed on the outer peripheral side of the frame support 26 . When the frame unit 11 is placed on the frame support 26 and the frame 7 of the frame unit 11 is gripped by the jig 24 , the frame unit 11 is fixed to the frame support 26 .

[0085] The frame support 26 is supported by a plurality of rods 28 extending in the vertical direction, and a cylinder 30 for raising and lowering the rod 28 is disposed at the lower end of each rod 28. The plurality of cylinders 30 are supported on a disk-shaped base 32. When each cylinder 30 is operated, the frame support 26 is lowered relative to the drum 20.

[0086] A lifting mechanism 34 is provided inside the drum 20 to lift the device chip supported by the polyolefin sheet 9 from below. The lifting mechanism 34 has the function of blowing air 34a upward. In addition, a collet 36 (see FIG. 1 ) is provided above the drum 20 to attract and hold the device chip. Fig.10 (B)). The lifting mechanism 34 and the collet 36 can move in the horizontal direction along the upper surface of the frame support platform 26. In addition, the collet 36 is connected to the switching portion 36b (see Fig.10 (B)) and the suction source 36a (refer to Fig.10 (B)) connection.

[0087] In the picking process, first, the air cylinder 30 is operated to adjust the height of the frame support table 26 so that the height of the upper end of the drum 20 of the picking device 18 coincides with the height of the upper surface of the frame support table 26. Next, the frame unit 11 carried out from the laser processing device 12 is placed on the drum 20 of the picking device 18 and the frame support table 26.

[0088] Then, the frame 7 of the frame unit 11 is fixed to the frame support stand 26 by the clamp 24 . Fig.10 (A) is a cross-sectional view schematically showing the frame unit 11 fixed to the frame support table 26. The wafer 1 is divided by forming dividing grooves 3a in the dividing step.

[0089] Next, the air cylinder 30 is operated to lower the frame support 26 of the frame holding unit 22 relative to the drum 20. Fig.10 As shown in (B), the polyolefin-based sheet 9 expands toward the outer peripheral direction. Fig.10 (B) is a cross-sectional view schematically showing the picking-up process.

[0090] When the polyolefin sheet 9 expands in the peripheral direction, the intervals between the device chips 1c supported by the polyolefin sheet 9 are expanded. As a result, the device chips 1c are less likely to contact each other, and it becomes easier to pick up each device chip 1c. Then, the device chip 1c to be picked up is determined, and the lifting mechanism 34 is moved below the device chip 1c, and the collet 36 is moved above the device chip 1c.

[0091] Then, the lifting mechanism 34 is operated to blow air 34a from the polyolefin sheet 9 side to lift the device chip 1c. Then, the switching unit 36b is operated to connect the collet 36 with the suction source 36a. Then, the device chip 1c is sucked and held by the collet 36, and the device chip 1c is picked up from the polyolefin sheet 9. Each of the picked up device chips 1c is then mounted on a predetermined wiring substrate and used.

[0092] Furthermore, when the device chip is picked up, by blowing air 34 a toward the device chip from the polyolefin sheet 9 side to lift the device chip, the load applied to the device chip when the device chip is peeled from the polyolefin sheet 9 can be reduced.

[0093] For example, when the frame unit 11 is formed using an adhesive tape, the heat generated by the irradiation of the laser beam 16 is transferred to the adhesive tape during the separation process, and the paste layer of the adhesive tape melts and adheres to the back side of the device chip. In addition, the quality of the device chip is degraded due to the adhesion of the paste layer.

[0094] In contrast, according to the wafer processing method of this embodiment, a frame unit using a polyolefin-based sheet without a paste layer can be formed by thermocompression bonding, so an adhesive tape with a paste layer is not required. As a result, the quality of the device chip is not reduced due to the paste layer adhering to the back side.

[0095] In addition, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made and implemented. For example, in the above-mentioned embodiments, the polyolefin sheet 9 is described as a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet, but one embodiment of the present invention is not limited thereto. For example, the polyolefin sheet can be made of other materials, such as a copolymer of propylene and ethylene, an olefin elastomer, etc.

[0096] In addition, the structure, method, etc. of the above-mentioned embodiment can be carried out with appropriate changes as long as it does not depart from the scope of the purpose of the present invention.

Claims

1. A wafer processing method for dividing a wafer having a plurality of devices formed in respective regions on a front surface divided by a predetermined dividing line into individual device chips, characterized in that: The wafer processing method has the following steps: a polyolefin sheet arranging step of positioning the wafer in an opening of a frame having an opening for accommodating the wafer, and arranging a polyolefin sheet without a paste layer on the back side of the wafer and on the outer periphery of the frame; An integration step of heating the polyolefin sheet and integrating the wafer and the frame by means of the polyolefin sheet through thermal compression; a dividing step of irradiating the wafer with a laser beam having a wavelength that is absorbent to the wafer along the planned dividing line to form dividing grooves and divide the wafer into individual device chips; and In the picking-up step, air is blown from the polyolefin sheet side to lift up the device chips one by one, and the device chips are picked up from the polyolefin sheet. If the polyolefin-based sheet is not heated, the polyolefin-based sheet cannot be integrated with the wafer and the frame.

2. The wafer processing method according to claim 1, characterized in that: In the integration step, the thermocompression bonding is performed by irradiation with infrared rays.

3. The wafer processing method according to claim 1, characterized in that: In the integration step, after the integration is performed, the polyolefin-based sheet protruding from the outer periphery of the frame is removed.

4. The wafer processing method according to claim 1, characterized in that: In the pickup step, the polyolefin-based sheet is expanded to increase the intervals between the device chips.

5. The wafer processing method according to claim 1, characterized in that: The polyolefin-based sheet is any one of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet.

6. The wafer processing method according to claim 5, characterized in that: In the integration process, when the polyolefin sheet is the polyethylene sheet, the heating temperature is 120°C to 140°C, when the polyolefin sheet is the polypropylene sheet, the heating temperature is 160°C to 180°C, and when the polyolefin sheet is the polystyrene sheet, the heating temperature is 220°C to 240°C.

7. The wafer processing method according to claim 1, characterized in that: The wafer is made of any material among Si, GaN, GaAs, and glass.

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