Method of processing a wafer

Abstract

A wafer processing method is provided, which forms device chips without reducing quality. The wafer processing method divides a wafer, in which a plurality of devices are formed in each region of a front surface divided by a division predetermined line, into individual device chips, and has: a polyester sheet arrangement step of positioning the wafer in an opening of a frame having an opening that receives the wafer, and arranging 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 joining the wafer and the frame by the polyester sheet by heat pressure bonding; a division step of irradiating a laser beam of a wavelength that is transmissive to the wafer along the division predetermined line to the wafer, forming a modified layer in the wafer, and dividing the wafer into individual device chips; and a pickup step of cooling the polyester sheet, lifting the device chips, and picking up the device chips.

Description

TECHNICAL FIELD

[0001] The present application relates to a wafer processing method for dividing a wafer in which a plurality of devices are formed in each region on a front surface divided by a division predetermined line into individual device chips. BACKGROUND

[0002] In a manufacturing process of a device chip for an electronic device such as a mobile phone or a personal computer, a plurality of division predetermined lines (streets) intersecting each other are set on a front surface of a wafer composed of a material such as a semiconductor. And, a device such as an IC (Integrated Circuit), an LSI (Large-Scale Integration circuit), an LED (Light Emitting Diode) is formed in each region divided by the division predetermined lines.

[0003] Then, an adhesive tape called a dicing tape which is pasted on a frame having a ring shape in a manner of closing an opening of the frame is pasted on the back surface or the front surface of the wafer, and a frame unit in which the wafer, the adhesive tape, and the frame having a ring shape are integrated is formed. And, when the wafer included in the frame unit is processed along the division predetermined lines to be divided, individual device chips are formed.

[0004] A laser processing device is used in the division of the wafer, for example. The laser processing device has a chuck table which holds the wafer through the adhesive tape, and a laser processing unit which converges a laser beam having a wavelength which is permeable to the wafer to the inside of the wafer, and the like.

[0005] In the division of the wafer, the frame unit is placed on the chuck table, and the wafer is held on the chuck table through the 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 to the wafer from the laser processing unit along each division predetermined line. When the laser beam is converged to the inside of the wafer, a modified layer which is a division starting point is formed (refer to Patent Literature 1).

[0006] Then, the frame unit is carried out from the laser processing device, and when the adhesive tape is expanded to the radial outside, the wafer is divided to form individual device chips. In picking up the formed device chips from the adhesive tape, a process of irradiating ultraviolet rays or the like to the adhesive tape is performed in advance to reduce the adhesive force of the adhesive tape. As a processing device in which the production efficiency of the device chips is high, a processing device which can continuously perform the division of the wafer and the ultraviolet irradiation to the adhesive tape by one device is known (refer to Patent Literature 2).

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

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

[0009] The adhesive tape, for example, includes a base material layer formed of a vinyl chloride sheet or the like and a paste layer provided on the base material layer. In a laser processing apparatus, in order to form a modified layer as a division starting point in the inside of a wafer, a laser beam is converged to the inside of the wafer, but a part of the light leakage of the laser beam reaches the paste layer of the adhesive tape. Also, due to the influence of heat caused by irradiation of the laser beam, the paste layer of the adhesive tape is melted, and a part of the paste layer is adhered to the back surface side or the front surface side of a device chip formed from the wafer.

[0010] In this case, when the device chip is picked up from the adhesive tape, even if a process of irradiating the adhesive tape with ultraviolet rays or the like is performed, the part of the paste layer remains on the back surface side or the front surface side of the picked-up device chip. Therefore, a decrease in quality of the device chip becomes a problem. SUMMARY

[0011] The present application was accomplished in view of this problem point, and aims to provide a wafer processing method which does not adhere the paste layer to the back surface side or the front surface side of a formed device chip, and does not cause a decrease in quality of the device chip due to the adhesion of the paste layer.

[0012] According to one embodiment of the present application, a wafer processing method of dividing a wafer in which a plurality of devices are formed in each region of a front surface divided by a division predetermined line into individual device chips is characterized by comprising: a polyester sheet providing step of positioning the wafer in an opening of a frame having an opening that receives the wafer, and providing 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 joining the wafer and the frame by the polyester sheet by heat pressure bonding; a division step of positioning a condensing point of a laser beam having a wavelength that is transmissive through the wafer in the inside of the wafer, irradiating the wafer with the laser beam along the division predetermined line, forming a modified layer in the wafer, and dividing the wafer into individual device chips; and a picking-up step of cooling the polyester sheet in each region of the polyester sheet corresponding to each device chip, and picking up the device chip from the polyester sheet by lifting the device chip from the polyester sheet.

[0013] Preferably, in the integration step, the heat pressure bonding is performed by irradiation of infrared rays.

[0014] Further, preferably, in the integration step, the polyester sheet that protrudes from the outer periphery of the frame is removed after the integration is performed.

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

[0016] Further, it is preferable that the polyester sheet be any of a polyethylene terephthalate sheet and a polyethylene naphthalate sheet.

[0017] Further, it is preferable that, in the integration process, the heating temperature be 250°C to 270°C when the polyester sheet is the polyethylene terephthalate sheet and the heating temperature be 160°C to 180°C when the polyester sheet is the polyethylene naphthalate sheet.

[0018] Further, it is preferable that the wafer be composed of any of Si, GaN, GaAs, and glass.

[0019] In the wafer processing method of one embodiment of the present application, when the frame unit is formed, an adhesive tape having a paste layer is not used, but a polyester sheet having no paste layer is used to integrate the frame and the wafer. The integration process in which the frame and the wafer are integrated by the polyester sheet is performed by heat press bonding.

[0020] After the integration process is performed, the wafer is irradiated with a laser beam having a wavelength that is transmissive through the wafer, a modified layer along the division predetermined line is formed in the wafer, and the wafer is divided. Then, the polyester sheet is cooled at each region of the polyester sheet corresponding to each device chip, the device chip is lifted from the side of the polyester sheet, and the device chip is picked up from the polyester sheet. The picked-up device chips are mounted on predetermined mounting targets, respectively. When the polyester sheet is cooled at the time of picking up, the polyester sheet shrinks, so that peeling of the polyester sheet becomes easy, and the load applied to the device chip can be reduced.

[0021] When the modified layer is formed in the wafer, light leakage of the laser beam reaches the polyester sheet. However, the polyester sheet has no paste layer, so that the paste layer does not melt and adhere to the back surface side or the front surface side of the device chip.

[0022] That is, according to one embodiment of the present application, the polyester sheet having no paste layer can be used to form the frame unit, so that the adhesive tape having the paste layer is not needed, and as a result, the quality of the device chip is not reduced due to the attachment of the paste layer.

[0023] Thus, according to one embodiment of the present application, the wafer processing method is provided, in which the paste layer is not attached to the back surface side or the front surface side of the formed device chip, and the quality of the device chip is not reduced due to the attachment of the paste layer. BRIEF DESCRIPTION OF DRAWINGS

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

[0025] Figure 2 This is a perspective view schematically illustrating the positioning of the wafer and frame on the holding surface of the chuck stage.

[0026] Figure 3 It is a three-dimensional diagram schematically showing the process of assembling polyester sheets.

[0027] Figure 4 This is a perspective view schematically illustrating an example of an integrated process.

[0028] Figure 5 This is a perspective view schematically illustrating another example of an integrated process.

[0029] Figure 6 This is a perspective view that schematically illustrates another example of an integrated process.

[0030] Figure 7 (A) is a perspective view schematically showing the cutting of a polyester sheet. Figure 7 (B) is a schematic three-dimensional view showing the formed frame unit.

[0031] Figure 8 (A) is a schematic perspective view showing the cutting process. Figure 8 (B) is a schematic cross-sectional view showing the splitting process.

[0032] Figure 9 It is a schematic perspective view showing the frame unit being moved into the pickup device.

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

[0034] Label Explanation

[0035] 1: Wafer; 1a: Front side; 1b: Back side; 3: Pre-cut 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 unit; 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; 14b: Focusing point; 16: Laser beam; 18: Pick-up device; 20: Drum; 22: Frame holding unit; 24: Fixture; 26: Frame support platform; 28: Rod; 30: Cylinder; 32: Base; 34: Lifting mechanism; 34a: Cooling unit; 36: Collet. DETAILED DESCRIPTION

[0036] An embodiment of one mode of the present application will be described with reference to the drawings. First, a wafer processed by a wafer processing method using the present embodiment will be described. Figure 1 (A) of FIG. 1 is a perspective view schematically showing a front surface of a wafer 1, Figure 1 (B) of FIG. 1 is a perspective view schematically showing a back surface of the wafer 1.

[0037] The wafer 1 is, for example, a substantially circular plate-like substrate or the like made of a material such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductors, or a material such as sapphire, glass, quartz, or the like. The glass is, for example, alkali glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, quartz glass, or the like.

[0038] The front surface la of the wafer 1 is divided by a plurality of division- scheduled lines 3 arranged in a lattice shape. Further, a device 5 such as an IC, LSI, LED, or the like is formed in each region of the front surface la of the wafer 1 divided by the division-scheduled lines 3. In the wafer processing method of the wafer 1 of the present embodiment, a modification layer along the division-scheduled lines 3 is formed in the inside of the wafer 1, and the wafer 1 is divided from the modification layer as a starting point, thereby forming each device chip.

[0039] When the modification layer is formed 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-scheduled lines 3, and the laser beam is converged to the inside of the wafer 1. At this time, the laser beam can be irradiated to the wafer 1 from the front surface la side as shown in (A) of FIG. 1, or can be irradiated to the wafer 1 from the back surface lb side as shown in (B) of FIG. 1. Figure 1 The laser beam can be irradiated to the wafer 1 from the front surface la side as shown in (A) of FIG. 1, or can be irradiated to the wafer 1 from the back surface lb side as shown in (B) of FIG. 1. Figure 1 Further, in a case where the laser beam is irradiated to the wafer 1 from the back surface lb side, an alignment unit having an infrared camera is used, the division-scheduled lines 3 on the front surface la side are detected through the wafer 1, and the laser beam is irradiated along the division-scheduled lines 3.

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

[0041] Further, when the polyester sheet is expanded, the wafer 1 is divided, and each device chip formed by dividing the wafer 1 is supported to the polyester sheet. Then, the polyester sheet is further expanded, thereby expanding the interval between the device chips, and the device chips are picked up by a pickup device.

[0042] Circular frame 7 (refer to) Figure 2 (e.g., made of materials such as metal), the frame 7 has an opening 7a with a diameter larger than that of the wafer 1. When forming the frame unit, the wafer 1 is positioned within the opening 7a of the frame 7 and housed within the opening 7a.

[0043] Polyester sheet 9 (reference) Figure 3 The polyester sheet 9 is a flexible resin-based sheet with a flat front and back. Furthermore, the polyester sheet 9 has a diameter larger than the outer diameter of the frame 7 and does not have a paste layer. The polyester sheet 9 is a sheet of a polymer synthesized using dicarboxylic acids (compounds having two carboxyl groups) and glycols (compounds having two hydroxyl groups) as monomers, such as polyethylene terephthalate sheets or polyethylene naphthalate sheets, which are transparent or translucent to visible light. However, the polyester sheet 9 is not limited to these and can also be opaque.

[0044] The polyester sheet 9 lacks adhesive properties and therefore cannot be bonded to the wafer 1 and frame 7 at room temperature. However, the polyester sheet 9 is thermoplastic, so when heated to a temperature near its melting point while bonding the polyester sheet 9 to the wafer 1 and frame 7 under a specified pressure, the polyester sheet 9 partially melts and can be bonded to the wafer 1 and frame 7. Therefore, in the wafer 1 processing method of this embodiment, the wafer 1, frame 7, and polyester sheet 9 are integrated by thermoforming as described above to form a frame unit.

[0045] Next, each step of the wafer 1 processing method of this embodiment will be described. First, a polyester sheet arrangement step is performed in order to prepare for the integration of wafer 1, polyester sheet 9 and frame 7. Figure 2 This is a perspective view schematically showing the wafer 1 and frame 7 positioned on the holding surface 2a of the chuck stage 2. (See diagram below.) Figure 2 As shown, a polyester sheet arrangement process is performed on a chuck worktable 2 with a holding surface 2a on the upper part.

[0046] The chuck table 2 has a porous component at its upper center with a diameter larger than the outer diameter of the frame 7. The upper surface of this porous component serves as the holding surface 2a of the chuck table 2. The chuck table 2 is as follows... Figure 3 The device shown has an exhaust passage with one end connected to the porous component, and an attraction source 2b is provided at the other end of the exhaust passage. A switching part 2c is provided on the exhaust passage to switch between a connected state and a disconnected state. When the switching part 2c is in the connected state, a negative pressure generated by the attraction source 2b is applied to the object to be held on the holding surface 2a, thereby attracting and holding the object to be held on the chuck table 2.

[0047] In the polyester sheet assembly process, the first step is as follows: 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 one of the front surface la and the back surface lb of the wafer 1 is to be the irradiated surface by the laser beam in the division process to be described later. For example, in the case where the irradiated surface is the front surface la, the front surface la side is oriented downward. Also, for example, in the case where the irradiated surface is the back surface lb, the back surface lb side is oriented downward. Hereinafter, the wafer processing method of the present embodiment will be described taking the case where the irradiated surface of the laser beam is the front surface la as an example, 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, the polyester sheet 9 is disposed on the back surface lb (or the front surface la) of the wafer 1 and on the outer periphery of the frame 7. Figure 3 is a perspective view schematically showing the polyester sheet disposing process. As shown, Figure 3 The polyester sheet 9 is disposed on the wafer 1 and the frame 7 in such a manner as to cover them.

[0050] Also, in the polyester sheet disposing process, the polyester 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 polyester sheet 9 in the integration process to be performed later, if the entire holding surface 2a is not covered with the polyester sheet 9, the negative pressure will leak from the gap, and the pressure cannot be properly applied to the polyester sheet 9.

[0051] In the wafer 1 processing method of the present embodiment, the integration process is then performed, in which the polyester sheet 9 is heated and the wafer 1 and the frame 7 are integrated by the polyester sheet 9 through thermal compression bonding. Figure 4 is a perspective view schematically showing an example of the integration process. In Figure 4 In the drawing, components that can be seen through the polyester sheet 9 that is transparent or translucent to visible light are indicated by broken lines.

[0052] In the integration process, first, the switching portion 2c of the chuck table 2 is made to operate to become in a communication state in which the suction source 2b is connected to the porous member of the upper portion of the chuck table 2, and the negative pressure of the suction source 2b is applied to the polyester sheet 9. Then, the polyester sheet 9 is made to adhere to the wafer 1 and the frame 7 by atmospheric pressure.

[0053] Next, the polyester sheet 9 is heated while being sucked by the suction source 2b to perform thermal compression bonding. The heating of the polyester sheet 9 is performed, for example, by the hot air gun 4 disposed above the chuck table 2 as shown in Figure 4

[0054] ​The hot air gun 4 has a heating unit such as an electric heating wire and a blower mechanism such as a fan inside, and can inject air heated. The hot air 4a is supplied to the polyester sheet 9 from the upper surface by the hot air gun 4 while applying a negative pressure to the polyester sheet 9, and when the polyester sheet 9 is heated to a predetermined 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 performed 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 is a perspective view schematically showing another example of the integration process. In Figure 5 In the integration process shown in

[0056] In the integration process shown in Figure 5 In the integration process shown in Figure 5 In the integration process shown in

[0057] Then, the heating roller 6 is heated to a predetermined temperature and is 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 polyester sheet 9 is thermocompression-bonded to the wafer 1 and the frame 7. At this time, when a force is applied to the polyester sheet 9 in a direction of pressing it down by the heating roller 6, the thermocompression-bonding is performed using a pressure greater than the atmospheric pressure. In addition, the surface of the heating roller 6 is preferably coated with a fluororesin.

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

[0059] The heating of the polyester sheet 9 can also be performed by other methods. Figure 6 is a perspective view schematically showing another example of the integration process. In Figure 6 In the integration process shown in Figure 6 In the integration process shown in

[0060] In the integration process shown in Figure 6In the shown integrated process, first, the negative pressure of the suction source 2b is applied to the polyester sheet 9, and the polyester sheet 9 is made to adhere to the wafer 1 and the frame 7. Next, the infrared lamp 8 is made to operate, and the polyester sheet 9 is heated by the infrared rays 8a. Thus, the polyester sheet 9 is thermocompression-bonded to the wafer 1 and the frame 7.

[0061] When the polyester sheet 9 is heated to a temperature near the melting point thereof by any method, the polyester sheet 9 is thermocompression-bonded to the wafer 1 and the frame 7. After the thermocompression-bonding of the polyester sheet 9, the switching section 2c is made to operate, and the communication state between the porous member of the chuck table 2 and the suction source 2b is released, and thus the chuck table 2 is released from the suction.

[0062] Next, the polyester sheet 9 that protrudes from the outer periphery of the frame 7 is cut off and removed. Figure 7 (A) is a perspective view that schematically shows the cutting of the polyester sheet 9. As for the cutting, as shown in (A) of FIG. 6, a circular ring-shaped cutter 10 is used. The cutter 10 has a through-hole, and is rotatable around a rotation axis that passes through the through-hole. Figure 7

[0063] First, the circular ring-shaped 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 cut off by sandwiching the polyester sheet 9 with the frame 7 and the cutter 10. Thus, a cut mark 9a is formed on the polyester sheet 9.

[0064] In addition, the cutter 10 is made to go around the frame 7 once around the opening 7a of the frame 7, and a prescribed region of the polyester sheet 9 is surrounded by the cut mark 9a. Then, the polyester sheet 9 of the region on the outer periphery side of the cut mark 9a is removed in such a way that the region of the polyester sheet 9 remains. Thus, the unnecessary part of the polyester sheet 9 including the region that protrudes from the outer periphery of the frame 7 can be removed.

[0065] In addition, an ultrasonic cutter can be used in the cutting of the polyester sheet, and a vibration source that vibrates the above-described circular ring-shaped cutter 10 at a frequency in the ultrasonic frequency band can be connected to the cutter 10. In addition, in order to make the cutting easy, the polyester sheet 9 can be cooled to harden it when cutting the polyester sheet 9. As described above, the frame unit 11 in which the wafer 1 and the frame 7 are integrated by the polyester sheet 9 is formed. Figure 7 (B) is a perspective view that schematically shows the frame unit 11 that is formed.

[0066] ​In addition, when the heat press bonding is performed, the polyester sheet 9 is preferably heated to a temperature below the melting point thereof. This is because, when the heating temperature exceeds the melting point, the polyester sheet 9 sometimes melts and the shape of the sheet cannot be maintained. In addition, the polyester sheet 9 is preferably heated to a temperature above the softening point thereof. This is because, if the heating temperature does not reach the softening point, the heat press bonding cannot be properly performed. That is, the polyester sheet 9 is preferably heated to a temperature above the softening point thereof and below the melting point thereof.

[0067] In addition, there are cases where a part of the polyester sheet 9 does not have a definite softening point. Therefore, when the heat press bonding is performed, the polyester sheet 9 is preferably heated to a temperature above 20°C below the melting point thereof and below the melting point thereof.

[0068] In addition, in the case where the polyester sheet 9 is a polyethylene terephthalate sheet, the heating temperature is preferably 250°C to 270°C. In addition, in the case where the polyester 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 sheet 9 when the integration process is performed. For example, among heat sources such as the hot air gun 4, the heating roller 6, and the infrared lamp 8, there are models in which the output temperature can be set, but even if the polyester sheet 9 is heated using such a heat source, the temperature of the polyester sheet 9 sometimes does not reach the set output temperature. Therefore, in order to heat the polyester sheet 9 to a predetermined temperature, the output temperature of the heat source can be set to be higher than the melting point of the polyester sheet 9.

[0070] Next, in the wafer processing method of the present embodiment, a dividing process is performed to laser process the wafer 1 in a state of the frame unit 11 to form a modified layer along the division predetermined line 3 in the inside of the wafer 1 and divide the wafer 1. The dividing process is performed, for example, using the laser processing apparatus shown in (A) of FIG. 10. Figure 8 (A) of FIG. 10 is a perspective view schematically showing the dividing process, Figure 8 (A) of FIG. 10 is a perspective view schematically showing the dividing process, Figure 8 (B) of FIG. 10 is a cross-sectional view schematically showing the dividing process.

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

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

[0073] When laser processing wafer 1, the frame unit 11 is placed on the chuck table, thereby holding wafer 1 on the chuck table through the polyester sheet 9. Next, the chuck table is rotated to align the predetermined dividing line 3 of wafer 1 with the processing feed direction of the laser processing apparatus 12. Furthermore, the relative position of the chuck table and the laser processing unit 14 is adjusted so that the processing head 14a is positioned above the extension of the predetermined dividing line 3. Finally, the focusing point 14b of the laser beam 16 is positioned at a predetermined height.

[0074] Next, while irradiating the interior of the wafer 1 with a laser beam 16 from the laser processing unit 14, the chuck stage and the laser processing unit 14 are moved relative to each other along a processing feed direction parallel to the upper surface of the chuck stage. That is, the focal 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 predetermined dividing line 3. Thus, a modified layer 3a is formed inside the wafer 1. Furthermore, in Figure 8 In (A), the modified layer 3a formed inside the wafer 1 is shown by dashed lines.

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

[0076] Wavelength: 1064nm

[0077] Repetition frequency: 50kHz

[0078] Average output: 1W

[0079] Feed rate: 200 mm / s

[0080] After forming a modified layer 3a inside the wafer 1 along one predetermined dividing line 3, the chuck stage and the laser processing unit 14 are moved relative to each other in an indexing feed direction perpendicular to the processing feed direction, and the wafer 1 is laser-processed in the same way along other predetermined dividing lines 3. After forming a modified layer 3a along all predetermined dividing lines 3 in one direction, the chuck stage is rotated about an axis perpendicular to the holding surface, and the wafer 1 is laser-processed in the same way along predetermined dividing lines 3 in another direction.

[0081] When the laser beam 16 is focused into the interior of the wafer 1 by the laser processing unit 14 to form the modified layer 3a, the leakage of the laser beam 16 reaches the polyester sheet 9 below the wafer 1.

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

[0083] In contrast, in the wafer processing method of this embodiment, a polyester sheet 9 without a paste layer is used in the frame unit 11. Therefore, even if light leakage from the laser beam 16 reaches the polyester sheet 9, the paste layer will not adhere to the back side 1b of the wafer 1. As a result, the quality of the device chip formed from the wafer 1 remains good.

[0084] Next, the wafer 1 is diced to form device chips by extending the polyester substrate 9 radially outward. Then, a pick-up process is performed to pick up each device chip from the polyester substrate 9. In the extension of the polyester substrate 9, [the following process is used]. Figure 9 The pickup device 18 is shown at the bottom. Figure 9 This is a perspective view schematically showing the transfer of the frame unit 11 into the pickup device 18.

[0085] 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 26. The frame support 26 of the frame holding unit 22 has an opening with a diameter larger than that of the drum 20, and is positioned at the same height as the upper end of the drum 20, surrounding the upper end of the drum 20 from the outer periphery.

[0086] A clamp 24 is provided on the outer periphery of the frame support platform 26. When the frame unit 11 is placed on the frame support platform 26 and the frame 7 of the frame unit 11 is held by the clamp 24, the frame unit 11 is fixed to the frame support platform 26.

[0087] The frame support platform 26 is supported by a plurality of rods 28 extending vertically, and each rod 28 is equipped with a cylinder 30 at its lower end to raise or lower it. The plurality of cylinders 30 are supported on a circular plate-shaped base 32. When the cylinders 30 are actuated, the frame support platform 26 is lowered relative to the drum 20.

[0088] Inside the drum 20 is a lifting mechanism 34 that lifts the device chip supported by the polyester sheet 9 from below. The lifting mechanism 34 has a cooling section 34a at its upper end, which houses a Peltier element or similar cooling mechanism. Additionally, a collet 36 (see reference) is provided above the drum 20 to attract and hold the device chip. Figure 10(B)). The lifting mechanism 34 and the collet 36 are movable in the horizontal direction along the upper surface of the frame support 26. In addition, the collet 36 is connected via a switching part 36b (see reference). Figure 10 (B) and with attraction source 36a (refer to) Figure 10 (B)) connection.

[0089] When expanding the polyester sheet 9, the height of the frame support 26 is first adjusted by actuating the cylinder 30 so that the height of the upper end of the drum 20 of the pickup device 18 is consistent with the height of the upper surface of the frame support 26. Then, the frame unit 11, which is taken out from the laser processing device 12, is placed on the drum 20 of the pickup device 18 and the frame support 26.

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

[0091] Next, the cylinder 30 is actuated, causing the frame support 26 of the frame holding unit 22 to descend relative to the drum 20. Thus, as... Figure 10 As shown in (B), the polyester sheet 9 extends radially outward. Figure 10 (B) is a schematic cross-sectional view showing the extended polyester sheet 9.

[0092] As the polyester substrate 9 expands, a radially outward force is applied to the wafer 1, dividing the wafer 1 starting from the modified layer 3a to form individual device chips 1c. When the polyester substrate 9 is further expanded, the spacing between the individual device chips 1c supported by the polyester substrate 9 is increased, making it easier to pick up each device chip 1c.

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

[0094] Then, the cooling section 34a is activated to lower the temperature, and the cooling section 34a contacts the area of ​​the polyester sheet 9 corresponding to the device chip 1c to cool that area. Furthermore, the lifting mechanism 34 is activated to lift the device chip 1c from the polyester sheet 9 side. Then, the switching section 36b is activated to connect the collet 36 to the suction source 36a. The device chip 1c is then held and picked up from the polyester sheet 9 by the collet 36. Each picked-up device chip 1c is subsequently mounted on a designated wiring substrate or the like for use.

[0095] Furthermore, when this region of the polyester sheet 9 is cooled by the cooling section 34a, the polyester sheet 9 shrinks, thereby generating greater stress at the interface between the polyester sheet 9 and the device chip, making peeling easier. Therefore, the load applied to the device chip during peeling from the polyester sheet 9 can be reduced.

[0096] For example, when using adhesive tape to form the frame unit 11, during the dicing process, leakage light from the laser beam 16 irradiating the wafer 1 reaches the adhesive tape, and the paste layer of the adhesive tape adheres to the back side of the device chip. Furthermore, the degradation of the device chip quality due to the adhesion of the paste layer becomes a problem.

[0097] In contrast, the wafer processing method according to this embodiment can form a frame unit 11 using a polyester sheet 9 without a paste layer by hot pressing, thus eliminating the need for adhesive tape with a paste layer. As a result, there is no degradation in the quality of the device chip due to a paste layer adhering to the back side.

[0098] Furthermore, the present invention is not limited to the embodiments described above, and various modifications and implementations are possible. For example, in the above embodiments, the polyester sheet 9 was described as a polyethylene terephthalate sheet or a polyethylene naphthalate sheet, but one aspect of the present invention is not limited to this. For example, other materials can be used for the polyester sheet, such as polyethylene terephthalate sheets, polyethylene terephthalate sheets, polyethylene naphthalate sheets, etc.

[0099] In addition, the structure and method of the above embodiments can be appropriately modified and implemented as long as they do not depart from the scope of the purpose of the present invention.

Claims

1. A method for processing a wafer, comprising dividing a wafer having multiple devices formed in various regions of the front side divided by predetermined dividing lines into individual device chips, characterized in that, The wafer fabrication method includes the following steps: In the polyester sheet placement process, the wafer is positioned in the opening of a frame with an opening for receiving the wafer. A polyester sheet without a paste layer is placed on the back or front side of the wafer and on the outer periphery of the frame in a manner that completely covers the wafer and the frame, so that the polyester sheet is in direct contact with the back side of the wafer and the frame, and the entire holding surface of the chuck stage that holds the wafer and the frame is covered by the polyester sheet. In the integration process, after the polyester sheet assembly process, the polyester sheet is heated while being pressured, and the wafer and the frame are integrated by hot pressing with the polyester sheet to form a frame unit. In the dicing process, a laser beam of a wavelength transparent to the wafer is focused inside the wafer, and the wafer is irradiated with the laser beam along the predetermined dicing line to form a modified layer in the wafer, thereby dicing the wafer into individual device chips; and In the picking process, the polyester sheet is cooled in each region corresponding to each device chip, the device chip is lifted from the polyester sheet side, and the device chip is picked up from the polyester sheet.

2. The wafer processing method according to claim 1, characterized in that, In this integrated process, the heat pressing is performed by irradiating with infrared light.

3. The wafer processing method according to claim 1, characterized in that, In this integrated process, after integration, the polyester sheets protruding from the outer periphery of the frame are removed.

4. The wafer processing method according to claim 1, characterized in that, In this picking process, the polyester sheet is expanded to increase the spacing between the device chips.

5. The wafer processing method according to claim 1, characterized in that, The polyester sheet is any sheet of polyethylene terephthalate sheet or polyethylene naphthalate sheet.

6. The wafer processing method according to claim 5, characterized in that, In this integrated process, when the polyester sheet is polyethylene terephthalate sheet, the heating temperature is 250°C to 270°C, and when the polyester sheet is polyethylene naphthalate sheet, the heating temperature is 160°C to 180°C.

7. The wafer processing method according to claim 1, characterized in that, The wafer can be made of any material selected from Si, GaN, GaAs, and glass.

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