Method for processing a wafer

Abstract

A method for processing a wafer is provided to form device chips without degrading the quality. The method for processing the wafer divides a wafer having a plurality of devices formed in respective regions on the front surface divided by dicing lines into individual device chips. The method for processing the wafer includes the following steps: a polyester film disposing step of positioning the wafer in the opening of a frame having an opening for accommodating the wafer, and disposing a polyester film on the back or front surface of the wafer and on the outer periphery of the frame; an integration step of heating the polyester film and integrally bonding the wafer and the frame through thermocompression bonding by means of the polyester film; a dicing step of irradiating a laser beam having a wavelength transmissive to the wafer along the dicing lines to form a modified layer in the wafer and dividing the wafer into individual device chips; and a pick-up step of blowing air to lift the device chips and pick up the device chips from the polyester film.

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 annular frame with an opening so as to seal the opening, and is pasted on the back or front side of the wafer to form a frame unit in which the wafer, the adhesive tape and the annular 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. The laser processing device includes a chuck table that holds the wafer via an adhesive tape, and a laser processing unit that focuses a laser beam having a wavelength that is transparent to the wafer into the interior of 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 along each predetermined dividing line to the wafer. When the laser beam is focused inside the wafer, a modified layer serving as a dividing starting point is formed (see Patent Document 1).

[0006] Then, the frame unit is removed from the laser processing device, and when the adhesive tape is extended 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 previously subjected to treatment such as ultraviolet irradiation to reduce the adhesive force of the adhesive tape. As a processing device with high production efficiency of device chips, a processing device that can continuously perform wafer division and ultraviolet irradiation on the adhesive tape using one device is known (see Patent Document 2).

[0007] Patent Document 1: Japanese Patent No. 3408805

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

[0009] The adhesive tape includes, for example, a base material layer formed of a vinyl chloride sheet or the like and a paste layer disposed on the base material layer. In a laser processing apparatus, in order to form a modified layer as a starting point for dicing inside a wafer, a laser beam is focused inside the wafer, but a part of the leaked light of the laser beam reaches the paste layer of the adhesive tape. And due to the influence of heat caused by the irradiation of the laser beam, the paste layer of the adhesive tape melts, and a part of the paste layer adheres to the back side or the front side of the device chip formed from the wafer.

[0010] In this case, when picking up the device chip from the adhesive tape, even if a process such as irradiating the adhesive tape with ultraviolet rays is performed, this part of the paste layer remains on the back side or the front side of the picked-up device chip. Therefore, a problem arises that the quality of the device chip is reduced. Summary of the Invention

[0011] The present invention has been completed in view of this problem, and an object thereof is to provide a method for processing a wafer, which does not attach a paste layer to the back side or the front side of the formed device chip and does not cause a reduction in quality due to the attachment of the paste layer on the device chip.

[0012] According to one aspect of the present invention, there is provided a method for processing a wafer, which divides a wafer having a plurality of devices formed in respective regions on the front surface divided by dicing lines into individual device chips, characterized in that the method for processing the wafer has the following steps: a polyester sheet disposing step of positioning the wafer in the opening of a frame having an opening for accommodating the wafer, and disposing a polyester sheet on the back surface or the front surface of the wafer and on the outer periphery of the frame; an integration step of heating the polyester sheet and integrally bonding the wafer and the frame with the aid of the polyester sheet by thermocompression bonding; a dicing step of positioning the focus point of a laser beam having a wavelength transmissive to the wafer inside the wafer, irradiating the wafer with the laser beam along the dicing line, forming a modified layer in the wafer, and dividing the wafer into individual device chips; and a picking-up step of blowing air from the polyester sheet side to lift the device chips one by one and picking up the device chips from the polyester sheet.

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

[0014] In addition, preferably, in the integration step, after the integration is performed, the polyester sheet protruding from the outer periphery of the frame is removed.

[0015] In addition, preferably, in the picking-up step, the polyester sheet is expanded to expand the interval between the device chips.

[0016] In addition, it is preferable that the polyester-based sheet is any one of polyethylene terephthalate sheets and polyethylene naphthalate sheets.

[0017] In addition, it is preferable that in this integrated process, when the polyester-based sheet is the polyethylene terephthalate sheet, the heating temperature is 250°C to 270°C, and when the polyester-based sheet is the polyethylene naphthalate sheet, the heating temperature is 160°C to 180°C.

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

[0019] In a method for processing a wafer according to one aspect of the present invention, when forming a frame unit, instead of using an adhesive tape having a paste layer, a polyester-based sheet without a paste layer is used to integrate the frame and the wafer. The integrated process of integrating the frame and the wafer by means of the polyester-based sheet is achieved by thermocompression bonding.

[0020] After the integrated process is performed, a laser beam having a wavelength that is transmissive to the wafer is irradiated onto the wafer, and a modified layer is formed along a dicing line in the wafer to dice the wafer. Then, by blowing air from the polyester-based sheet side, the device chips are lifted one by one, and the device chips are picked up from the polyester-based sheet. The picked-up device chips are respectively mounted on predetermined mounting objects. Among them, when the device chips are lifted by air during picking, the load applied to the device chips when peeling from the polyester-based sheet can be reduced.

[0021] When a modified layer is formed inside the wafer, the leakage light of the laser beam reaches the polyester-based sheet. However, since the polyester-based sheet does not have a paste layer, the situation where the paste layer melts and adheres to the back side or the front side of the device chip does not occur.

[0022] That is, according to one aspect of the present invention, a frame unit can be formed using a polyester-based sheet without a paste layer, so an adhesive tape having a paste layer is not required. As a result, a reduction in the quality of the device chips due to the adhesion of the paste layer does not occur.

[0023] Therefore, according to one aspect of the present invention, there is provided a method for processing a wafer, in which a paste layer does not adhere to the back side or the front side of the formed device chips, and a reduction in quality due to the adhesion of the paste layer does not occur on the device chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 (A) is a perspective view schematically showing the front side of the wafer, Figure 1 (B) is a perspective view schematically showing the back side of the wafer.

[0025] Figure 2It is a perspective view schematically showing a situation 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 a polyester sheet arranging process.

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

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

[0029] Figure 6 It is a perspective view schematically showing still another example of an integration process.

[0030] Figure 7 (A) of is a perspective view schematically showing a situation where a polyester sheet is cut, Figure 7 (B) of is a perspective view schematically showing a formed frame unit.

[0031] Figure 8 (A) of is a perspective view schematically showing a dividing process, Figure 8 (B) of is a cross-sectional view schematically showing the dividing process.

[0032] Figure 9 It is a perspective view schematically showing a frame unit being carried into a pick-up device.

[0033] Figure 10 (A) of is a cross-sectional view schematically showing a frame unit fixed to a frame support table, Figure 10 (B) of is a cross-sectional view schematically showing a pick-up process.

[0034] Reference Numeral Explanation

[0035] 1: Wafer; 1a: Front surface; 1b: Back surface; 3: Dicing line; 3a: Modified layer; 5: Device; 7: Frame; 7a: Opening; 9: Polyester 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 ray; 10: Cutter; 12: Laser processing device; 14: Laser processing unit; 14a: Processing head; 14b: Focus point; 16: Laser beam; 18: Pick-up device; 20: Drum; 22: Frame holding unit; 24: Fixture; 26: Frame support table; 28: Rod; 30: Cylinder; 32: Base; 34: Lifting mechanism; 34a: Air; 36: Collet. Detailed Description of the Invention

[0036] With reference to the accompanying drawings, an embodiment of one aspect of the present invention will be described. First, a wafer processed by the processing method of the wafer of the present embodiment will be described. Figure 1 FIG. (A) schematically shows a perspective view of the front surface of the wafer 1. Figure 1 FIG. (B) schematically shows a perspective view of the back surface of the wafer 1.

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

[0038] The front surface 1a of the wafer 1 is divided by a plurality of division predetermined lines 3 arranged in a grid pattern. In addition, devices 5 such as ICs, LSIs, and LEDs are formed in each region of the front surface 1a of the wafer 1 divided by the division predetermined lines 3. In the processing method of the wafer 1 of the present embodiment, a modified layer is formed inside the wafer 1 along the division predetermined lines 3, and the wafer 1 is divided starting from this modified layer to form individual device chips.

[0039] When forming the modified layer in the wafer 1, a laser beam having a wavelength that is transmissive to the wafer 1 is irradiated to the wafer 1 along the division predetermined lines 3, and the laser beam is focused inside the wafer 1. At this time, this laser beam can be irradiated to the wafer 1 from Figure 1 the front surface 1a side shown in FIG. (A), or can also be irradiated to the wafer 1 from Figure 1 the back surface 1b side shown in FIG. (B). In addition, when irradiating the laser beam to the wafer 1 from the back surface 1b side, an alignment unit having an infrared camera is used to detect the division predetermined lines 3 on the front surface 1a side through the wafer 1, and the laser beam is irradiated along the division predetermined lines 3.

[0040] Before loading the wafer 1 into a laser processing apparatus 12 (refer to Figure 8 ), the wafer 1, a polyester sheet, and a frame are integrated to form a frame unit. The wafer 1 is loaded into the laser processing apparatus 12 in the state of the frame unit and processed.

[0041] Moreover, when the polyester sheet is expanded, the wafer 1 can be divided, and each device chip formed by dividing the wafer 1 is supported by this polyester sheet. Then, the polyester sheet is further expanded to expand the interval between the device chips, and the device chips are picked up by a pick-up device.

[0042] The annular frame 7 (refer to Figure 2The frame 7 is formed of a material such as metal, etc., and the frame 7 has an opening 7a with a diameter larger than the diameter of the wafer 1. When forming the frame unit, the wafer 1 is positioned within the opening 7a of the frame 7 and accommodated in the opening 7a.

[0043] The polyester-based sheet 9 (refer to Figure 3 etc.) is a resin-based sheet having flexibility, with a flat front and back. Also, the polyester-based sheet 9 has a diameter larger than the outer diameter of the frame 7 and does not have an adhesive layer. The polyester-based sheet 9 is a sheet of a polymer synthesized using a dicarboxylic acid (a compound having two carboxyl groups) and a diol (a compound having two hydroxyl groups) as monomers. For example, there are sheets such as polyethylene terephthalate sheets or polyethylene naphthalate sheets that are transparent or semi-transparent to visible light. However, the polyester-based sheet 9 is not limited to this and can also be opaque.

[0044] The polyester-based sheet 9 does not have adhesiveness, so it cannot be pasted onto the wafer 1 and the frame 7 at room temperature. However, the polyester-based sheet 9 has thermoplasticity. Therefore, when heated to a temperature near the melting point while applying a prescribed pressure and in a state where the polyester-based sheet 9 is joined to the wafer 1 and the frame 7, the polyester-based sheet 9 locally melts and can be adhered to the wafer 1 and the frame 7. Thus, in the method for processing the wafer 1 of the present embodiment, the wafer 1, the frame 7, and the polyester-based sheet 9 are integrated by the above-described thermocompression bonding to form the frame unit.

[0045] Next, each process of the method for processing the wafer 1 of the present embodiment will be described. First, a polyester-based sheet disposition process is performed to prepare for integrating the wafer 1, the polyester-based sheet 9, and the frame 7. Figure 2 is a perspective view schematically showing the situation where the wafer 1 and the frame 7 are positioned on the holding surface 2a of the chuck table 2. As Figure 2 shown, the polyester-based sheet disposition process is performed on the chuck table 2 having the holding surface 2a in the upper part.

[0046] The chuck table 2 has a porous member in the upper center with a diameter larger than the outer diameter of the frame 7. The upper surface of this porous member serves as the holding surface 2a of the chuck table 2. As Figure 3 shown, the chuck table 2 has an exhaust passage inside with one end communicating with this porous member, and a suction source 2b is disposed on the other end side of this exhaust passage. A switching portion 2c for switching between a connected state and a cut-off state is disposed on the exhaust passage. When the switching portion 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, and thus the object to be held is attracted and held by the chuck table 2.

[0047] In the polyester-based sheet disposition process, first, as Figure 2As shown, the wafer 1 and the frame 7 are placed on the holding surface 2a of the chuck table 2, and the wafer 1 is positioned within the opening 7a of the frame 7.

[0048] At this time, the orientation of the wafer 1 is selected in consideration of which of the front surface 1a and the back surface 1b will be the irradiated surface irradiated with a laser beam in the subsequent dicing process. For example, when the irradiated surface is the front surface 1a, the front surface 1a side is oriented downward. Additionally, for example, when the irradiated surface is the back surface 1b, the back surface 1b side is oriented downward. Hereinafter, taking the case where the irradiated surface of the laser beam is the front surface 1a as an example, the processing method of the wafer in the present embodiment will be described, but the orientation of the wafer 1 is not limited thereto.

[0049] After the wafer 1 and the frame 7 are placed on the holding surface 2a of the chuck table 2, a polyester-based sheet 9 is disposed on the back surface 1b (or the front surface 1a) of the wafer 1 and on the outer periphery of the frame 7. Figure 3 is a perspective view schematically showing the polyester-based sheet disposing process. As Figure 3 shown, the polyester-based sheet 9 is disposed on both the wafer 1 and the frame 7 so as to cover them.

[0050] In addition, in the polyester-based sheet disposing process, a polyester-based sheet 9 having a diameter larger 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 polyester-based sheet 9 in the subsequent integration process, if the entire holding surface 2a is not covered by the polyester-based sheet 9, the negative pressure will leak from the gap and the pressure cannot be properly applied to the polyester-based sheet 9.

[0051] In the processing method of the wafer 1 in the present embodiment, then the integration process is carried out, the polyester-based sheet 9 is heated, and the wafer 1 and the frame 7 are integrated by thermocompression bonding through the polyester-based sheet 9. Figure 4 is a perspective view schematically showing an example of the integration process. In Figure 4 it, the components that can be visually recognized through the polyester-based sheet 9 that is transparent or translucent to visible light are shown by dashed lines.

[0052] In the integration process, first, the switching part 2c of the chuck table 2 is actuated to be in a communication state in which the suction source 2b is connected to the porous member at the upper part of the chuck table 2, and the negative pressure of the suction source 2b is applied to the polyester-based sheet 9. Then, the polyester-based sheet 9 is pressed against the wafer 1 and the frame 7 by the atmospheric pressure.

[0053] Next, while sucking the polyester-based sheet 9 by the suction source 2b, the polyester-based sheet 9 is heated to perform thermocompression bonding. The heating of the polyester-based sheet 9 is carried out, for example, as Figure 4 shown, by a hot air gun 4 disposed above the chuck table 2.

[0054] The hot air gun 4 has a heating unit such as a heating wire and a blowing mechanism such as a fan inside, and can heat and eject air. While applying negative pressure to the polyester sheet 9, hot air 4a is supplied to the polyester sheet 9 from the upper surface by the hot air gun 4. When the polyester sheet 9 is heated to a specified temperature, the polyester sheet 9 is thermocompression-bonded to the wafer 1 and the frame 7.

[0055] In addition, the heating of the polyester sheet 9 can also be carried out by other methods. For example, it can be carried out by pressing the wafer 1 and the frame 7 from above with a member heated to a specified temperature. Figure 5 It is a perspective view schematically showing another example of the integrated process. In Figure 5 the members that can be visually recognized through the polyester sheet 9 that is transparent or translucent to visible light are shown by dashed lines.

[0056] In Figure 5 the integrated process shown, for example, a heating roller 6 having a heat source inside is used. In Figure 5 the integrated process shown, first, the negative pressure of the suction source 2b is applied to the polyester sheet 9, and the polyester sheet 9 is pressed against the wafer 1 and the frame 7 by atmospheric pressure.

[0057] Then, the heating roller 6 is heated to a specified 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 from this end to the other end on the chuck table 2. Thus, the polyester sheet 9 is thermocompression-bonded to the wafer 1 and the frame 7. At this time, when a force is applied in the direction of pressing down the polyester sheet 9 by the heating roller 6, thermocompression bonding is carried out using a pressure greater than atmospheric pressure. In addition, it is preferable to coat the surface of the heating roller 6 with fluororesin.

[0058] In addition, an iron-like pressing member having a heat source inside and a flat bottom plate can also be used instead of the heating roller 6 to carry out the thermocompression bonding of the polyester sheet 9. In this case, the pressing member is heated to a specified temperature to become a hot plate, and the polyester sheet 9 held by the chuck table 2 is pressed from above using this pressing member.

[0059] The heating of the polyester sheet 9 can also be carried out by other methods. Figure 6 It is a perspective view schematically showing yet another example of the integrated process. In Figure 6 the members that can be visually recognized through the polyester sheet 9 that is transparent or translucent to visible light are shown by dashed lines. In Figure 6 the integrated process shown, an infrared lamp 8 disposed above the chuck table 2 is used to heat the polyester sheet 9. The infrared lamp 8 can irradiate at least infrared rays 8a having a wavelength that the material of the polyester sheet 9 has absorbency for.

[0060] In Figure 6In the integration process shown, the negative pressure of the suction source 2b is first applied to the polyester sheet 9, so that the polyester sheet 9 is closely attached to the wafer 1 and the frame 7. Then, the infrared lamp 8 is operated to irradiate the polyester sheet 9 with infrared rays 8a to heat the polyester sheet 9. Thus, the polyester sheet 9 is thermally pressed onto the wafer 1 and the frame 7.

[0061] When the polyester sheet 9 is heated to a temperature near its melting point by any method, the polyester sheet 9 is thermally pressed onto the wafer 1 and the frame 7. After the polyester sheet 9 is thermally pressed, 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.

[0062] Next, the polyester 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 state of cutting the polyester sheet 9. Figure 7 As shown in (A), a circular 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.

[0063] 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 polyester sheet 9 is sandwiched between the frame 7 and the cutter 10 to cut the polyester sheet 9. As a result, a cut mark 9a is formed on the polyester sheet 9.

[0064] 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 polyester sheet 9 is surrounded by the cut mark 9a. Then, the polyester sheet 9 in the area on the outer peripheral side of the cut mark 9a is removed so that the polyester sheet 9 remains in the area. Thus, the unnecessary part of the polyester sheet 9 including the area protruding from the outer periphery of the frame 7 can be removed.

[0065] In addition, an ultrasonic cutter may be used to cut the polyester 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 polyester sheet 9 is cut, the polyester 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 polyester sheet 9 is formed. Figure 7 (B) is a perspective view schematically showing the formed frame unit 11 .

[0066] In addition, when performing thermal compression bonding, the polyester-based sheet 9 is preferably heated to a temperature below its melting point. This is because when the heating temperature exceeds the melting point, the polyester-based sheet 9 may melt and the shape of the sheet cannot be maintained. In addition, the polyester-based 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, thermal compression bonding cannot be properly performed. That is, the polyester-based sheet 9 is preferably heated to a temperature above its softening point and below its melting point.

[0067] In addition, there is also a case where a part of the polyester-based sheet 9 does not have a clear softening point. Therefore, when performing thermal compression bonding, the polyester-based sheet 9 is preferably heated to a temperature above 20°C lower than its melting point and below its melting point.

[0068] In addition, when the polyester-based sheet 9 is a polyethylene terephthalate sheet, the heating temperature is preferably 250°C to 270°C. In addition, when the polyester-based sheet 9 is a polyethylene naphthalate sheet, the heating temperature is preferably 160°C to 180°C.

[0069] Here, the heating temperature refers to the temperature of the polyester-based sheet 9 during the integrated process. For example, among heat sources such as the hot air gun 4, the heating roller 6, and the infrared lamp 8, a model capable of setting the output temperature is actually used. However, even when the polyester-based sheet 9 is heated using this heat source, the temperature of the polyester-based sheet 9 sometimes does not reach the set output temperature. Therefore, in order to heat the polyester-based sheet 9 to a specified temperature, the output temperature of the heat source can be set higher than the melting point of the polyester-based sheet 9.

[0070] Next, in the method for processing a wafer according to the present embodiment, a dicing process is performed, and the wafer 1 in the state of the frame unit 11 is laser processed to form a modified layer along the dicing line 3 inside the wafer 1 to dice the wafer 1. The dicing process is performed using, for example, Figure 8 the laser processing apparatus shown in (A) of Figure 8 (A) of Figure 8 is a perspective view schematically showing the dicing process,

[0071] The laser processing apparatus 12 includes: a laser processing unit 14 that irradiates a laser beam 16 onto the wafer 1; and a chuck table (not shown) that holds the wafer 1. The laser processing unit 14 includes a laser oscillator (not shown) that can oscillate a laser, and can emit a laser beam 16 having a wavelength that is transmissive to the wafer 1 (a wavelength that can pass through the wafer 1). The chuck table can move in a direction parallel to the upper surface (processing feed).

[0072] The laser processing unit 14 irradiates the laser beam 16 emitted from the laser oscillator onto the wafer 1 held by the chuck table. The processing head 14a of the laser processing unit 14 has a function of positioning the focus point 14b of the laser beam 16 at a prescribed height position inside the wafer 1.

[0073] When laser-processing the wafer 1, the frame unit 11 is placed on the chuck table, and thus the wafer 1 is held on the chuck table with the polyester-based sheet 9 interposed therebetween. Next, the chuck table is rotated to align the dicing line 3 of the wafer 1 with the processing feed direction of the laser processing apparatus 12. Further, the relative positions of the chuck table and the laser processing unit 14 are adjusted such that the processing head 14a is disposed above the extension line of the dicing line 3. And the focus point 14b of the laser beam 16 is positioned at a prescribed height position.

[0074] Next, while irradiating the inside of the wafer 1 with the laser beam 16 from the laser processing unit 14, the chuck table and the laser processing unit 14 are relatively moved in the processing feed direction parallel to the upper surface of the chuck table. That is, the focus point 14b of the laser beam 16 is positioned inside the wafer 1, and the laser beam 16 is irradiated onto the wafer 1 along the dicing line 3. Then, a modified layer 3a is formed inside the wafer 1. Further, in Figure 8 the (A) of, the modified layer 3a formed inside the wafer 1 is shown by a dashed line.

[0075] The irradiation conditions of the laser beam 16 in the dicing process are set as follows, for example. However, the irradiation conditions of the laser beam 16 are not limited thereto.

[0076] Wavelength: 1064 nm

[0077] Repetition frequency: 50 kHz

[0078] Average output: 1 W

[0079] Feed speed: 200 mm / second

[0080] After the modified layer 3a is formed inside the wafer 1 along one dicing line 3, the chuck table and the laser processing unit 14 are relatively moved in the index feed direction perpendicular to the processing feed direction, and the wafer 1 is similarly laser-processed along the other dicing line 3. After the modified layer 3a is formed along all the dicing lines 3 in one direction, the chuck table is rotated about an axis perpendicular to the holding surface, and the wafer 1 is similarly laser-processed along the dicing lines 3 in the other direction.

[0081] When the laser beam 16 is converged inside the wafer 1 by the laser processing unit 14 to form the modified layer 3a, the leaked light of the laser beam 16 reaches the polyester-based sheet 9 below the wafer 1.

[0082] For example, when an adhesive tape is used instead of the polyester film 9 in the frame unit 11, if the leaked light of the laser beam 16 irradiates the paste layer of the adhesive tape, the paste layer of the adhesive tape melts, and a part of the paste layer adheres to the back surface 1b side of the wafer 1. In this case, this part of the paste layer remains on the back surface side of the device chip formed by dividing the wafer 1. Therefore, a problem of deterioration in the quality of the device chip arises.

[0083] In contrast, in the method for processing a wafer according to the present embodiment, a polyester film 9 without a paste layer is used in the frame unit 11. Therefore, even if the leaked light of the laser beam 16 reaches the polyester film 9, the paste 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 remains good.

[0084] Next, by expanding the polyester film 9 radially outward, the wafer 1 is divided to form device chips. Then, a pick-up process is performed to pick up each of the device chips from the polyester film 9. In the expansion of the polyester film 9, the pick-up device 18 shown in the Figure 9 lower part is used. Figure 9 FIG. is a perspective view schematically showing the loading of the frame unit 11 into the pick-up device 18.

[0085] The pick-up device 18 includes: a cylindrical drum 20 having a diameter larger than the diameter 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 with a diameter larger than the diameter of the drum 20, is disposed at the same height as the upper end portion of the drum 20, and surrounds the upper end portion of the drum 20 from the outer peripheral side.

[0086] A clamp 24 is disposed on the outer peripheral side of the frame support table 26. When the frame unit 11 is placed on the frame support table 26 and the frame 7 of the frame unit 11 is gripped by the clamp 24, the frame unit 11 is fixed to the frame support table 26.

[0087] The frame support table 26 is supported by a plurality of rods 28 extending in the vertical direction, and air cylinders 30 for raising and lowering the rods 28 are disposed at the lower end portions of the respective rods 28. The plurality of air cylinders 30 are supported by a disk-shaped base 32. When each air cylinder 30 is actuated, the frame support table 26 is lowered relative to the drum 20.

[0088] A lifting mechanism 34 for lifting the device chip supported by the polyester film 9 from below is disposed inside the drum 20. The lifting mechanism 34 has a function of blowing air 34a upward. In addition, a collet 36 capable of attracting and holding the device chip is disposed above the drum 20 (refer to Figure 10(B)). The lifting mechanism 34 and the collet 36 can move in the horizontal direction along the upper surface of the frame support table 26. In addition, the collet 36 is connected to the suction source 36a (see Figure 10 (B)) via the switching unit 36b (see Figure 10 (B)).

[0089] When expanding the polyester-based sheet 9, first, the 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 pickup device 18 is the same as the height of the upper surface of the frame support table 26. Then, the frame unit 11 carried out from the laser processing device 12 is placed on the drum 20 of the pickup device 18 and the frame support table 26.

[0090] Then, the frame 7 of the frame unit 11 is fixed to the frame support table 26 by the clamp 24. Figure 10 (A) is a schematic cross-sectional view showing the frame unit 11 fixed to the frame support table 26. A modified layer 3a is formed inside the wafer 1 along the dicing predetermined line 3.

[0091] Next, the cylinder 30 is operated to lower the frame support table 26 of the frame holding unit 22 relative to the drum 20. Then, as shown in Figure 10 (B), the polyester-based sheet 9 expands radially outward. Figure 10 (B) is a schematic cross-sectional view showing the expanded polyester-based sheet 9.

[0092] When the polyester-based sheet 9 expands, a force acting radially outward is applied to the wafer 1, and the wafer 1 is diced starting from the modified layer 3a to form individual device chips 1c. When the polyester-based sheet 9 is further expanded, the interval between the device chips 1c supported by the polyester-based sheet 9 is expanded, and it becomes easier to pick up each device chip 1c.

[0093] In the wafer processing method of the present embodiment, after the wafer 1 is diced to form individual device chips 1c, a pickup process is performed to pick up the device chips 1c from the polyester-based sheet 9. In the pickup process, the device chip 1c to be picked up is determined, the lifting mechanism 34 is moved below the device chip 1c, and the collet 36 is moved above the device chip 1c.

[0094] Then, the lifting mechanism 34 is operated to blow air 34a from the side of the polyester-based sheet 9 to lift the device chip 1c. Then, the switching unit 36b is operated to connect the collet 36 to the suction source 36a. Thus, the device chip 1c is attracted and held by the collet 36, and the device chip 1c is picked up from the polyester-based sheet 9. Each picked-up device chip 1c is then mounted on a predetermined wiring board or the like for use.

[0095] In addition, when picking up the device chip 1c and blowing air 34a to the device chip 1c from the side of the polyester sheet 9 to lift the device chip 1c, the load applied to the device chip 1c when peeling the device chip 1c from the polyester sheet 9 can be reduced.

[0096] For example, in the case of forming the frame unit 11 using an adhesive tape, in the dicing process, the leakage light of the laser beam 16 irradiated to the wafer 1 reaches the adhesive tape, and the paste layer of the adhesive tape adheres to the back side of the device chip. And, the reduction in the quality of the device chip due to the adhesion of the paste layer becomes a problem.

[0097] In contrast, according to the wafer processing method of the present embodiment, the frame unit 11 using the polyester sheet 9 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 reduction in the quality of the device chip due to the paste layer adhering to the back side does not occur.

[0098] In addition, the present invention is not limited to the description of the above embodiment, and various modifications can be made and implemented. For example, in the above embodiment, the case where the polyester sheet 9 is, for example, a polyethylene terephthalate sheet or a polyethylene naphthalate sheet is described, but one aspect of the present invention is not limited thereto. For example, other materials can be used for the polyester sheet, and it can be a polypropylene terephthalate sheet, a polybutylene terephthalate sheet, a polybutylene naphthalate sheet, etc.

[0099] In addition to this, the structure, method, etc. of the above embodiment can be appropriately modified and implemented as long as they do not deviate from the scope of the object of the present invention.

Claims

1. A method for processing a wafer, which divides a wafer having a plurality of devices formed in respective regions on the front surface divided by dicing predetermined lines into individual device chips, characterized in that the method for processing the wafer has the following steps: A polyester film arranging step of positioning the wafer in the opening of a frame having an opening for accommodating the wafer, and arranging a polyester film without an adhesive layer and having no adhesiveness at room temperature on the back surface or the front surface of the wafer and on the outer periphery of the frame; An integration step of heating the polyester film to a temperature near the melting point while applying a predetermined pressure to the polyester film, and integrating the wafer and the frame through thermocompression bonding by means of the polyester film in a state where the polyester film is joined to the wafer and the frame; A dicing step of positioning the focus point of a laser beam having a wavelength transmissive to the wafer inside the wafer, irradiating the laser beam along the dicing predetermined line to form a modified layer in the wafer, and dividing the wafer into individual device chips; and A picking step of blowing air from the polyester film side to lift the device chips one by one, and picking up the device chips from the polyester film.

2. The method for processing a wafer according to claim 1, characterized in that in the integration step, the thermocompression bonding is performed by irradiating infrared rays.

3. The method for processing a wafer according to claim 1, characterized in that in the integration step, after the integration is performed, the polyester film protruding from the outer periphery of the frame is removed.

4. The method for processing a wafer according to claim 1, characterized in that in the picking step, the polyester film is expanded to expand the intervals between the device chips.

5. The method for processing a wafer according to claim 1, characterized in that the polyester film is any one of polyethylene terephthalate film and polyethylene naphthalate film.

6. The method for processing a wafer according to claim 5, characterized in that in the integration step, when the polyester film is the polyethylene terephthalate film, the heating temperature is 250°C to 270°C, and when the polyester film is the polyethylene naphthalate film, the heating temperature is 160°C to 180°C.

7. The method for processing a wafer according to claim 1, characterized in that the wafer is made of any one of Si, GaN, GaAs, and glass.

8. The method for processing a wafer according to claim 1, characterized in that in the integration step, the thermocompression bonding is performed by blowing hot air to the polyester film to heat the polyester film.

9. The method for processing a wafer according to claim 1, characterized in that in the integration step, the thermocompression bonding is performed by pressing the polyester film with a roller.

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