Method of processing a wafer

Abstract

The present application provides a wafer processing method for forming device chips without reducing quality. The wafer processing method divides a wafer, which has a plurality of devices formed in each region of a front surface divided by a division predetermined line, into individual device chips, wherein the wafer processing method has the following steps: a polyester sheet arrangement step of positioning the wafer in an opening of a frame having an opening for receiving 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 through thermal compression; a division step of irradiating a laser beam having a wavelength that is transmissive to the wafer along the division predetermined line to the wafer, forming a shield tunnel in the wafer, and dividing the wafer into individual device chips; and a pickup step of lifting the device chips by blowing air, and picking up each of the device chips from the polyester sheet.

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 a 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 irradiates a laser beam having a wavelength which is transparent to the wafer to the wafer in a state in which a focal point is positioned inside the wafer.

[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 an upper surface of the chuck table, the laser beam is continuously irradiated to the wafer from the laser processing unit along each division predetermined line.

[0006] When the laser beam is irradiated to the wafer, a filament-like region called a shield tunnel is continuously formed along the division predetermined line. The shield tunnel is composed of a fine hole along a thickness direction of the wafer and an amorphous region surrounding the fine hole, and serves as a starting point of the division of the wafer (see Patent Literature 1).

[0007] Then, the frame unit is carried out from the laser processing apparatus, and the wafer is divided to form individual device chips when the adhesive tape is expanded to the radial outside. When the formed device chips are picked up from the adhesive tape, a process of irradiating the adhesive tape with ultraviolet rays or the like is performed in advance to reduce the adhesive force of the adhesive tape. As a processing apparatus that is high in production efficiency of device chips, a processing apparatus capable of continuously performing division of a wafer and ultraviolet irradiation of an adhesive tape with one apparatus is known (see Patent Literature 2).

[0008] Patent Literature 1: Japanese Patent No. 6151557

[0009] Patent Literature 2: Japanese Patent No. 3076179

[0010] The adhesive tape contains, for example, a base material layer formed of a vinyl chloride sheet or the like and a paste layer provided on the base material layer. In the laser processing apparatus, a laser beam is irradiated to the inside of the wafer in order to form a shield tunnel as a division starting point in the wafer. At this time, 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 the 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 the device chip formed from the wafer.

[0011] In this case, when the device chip is picked up from the adhesive tape, even if the 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

[0012] The present application is achieved in view of this problem, and an object thereof is to provide a processing method of a wafer, which does not cause the paste layer to adhere to the back surface side or the front surface side of the formed device chip and does not cause a decrease in quality of the device chip due to the adhesion of the paste layer.

[0013] According to one embodiment of the present application, there is provided 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, characterized by comprising: a polyester sheet arranging step of positioning the wafer in an opening of a frame having an opening for receiving 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 integrating step of integrating the wafer and the frame by the polyester sheet by heat pressure bonding by heating the polyester sheet; a division step of positioning a focal point of a laser beam having a wavelength that is transmissive through the wafer inside the wafer, and irradiating the wafer with the laser beam along the division predetermined line to continuously form a shield tunnel in the wafer, and dividing the wafer into individual device chips; and a pickup step of picking up each of the device chips from the polyester sheet by blowing air from the polyester sheet side to lift the device chips one by one.

[0014] Preferably, in the integrating step, the heat pressure bonding is performed by irradiation of infrared rays.

[0015] Further, preferably, in the integrating step, the polyester sheet is removed after the integrating is performed, from the outer periphery of the frame.

[0016] Further, preferably, in the pickup step, the polyester sheet is expanded to expand the interval between the device chips.

[0017] Further, preferably, the polyester sheet is any of a polyethylene terephthalate sheet and a polyethylene naphthalate sheet.

[0018] Further, preferably, in the integrating step, the heating temperature is 250°C to 270°C when the polyester sheet is the polyethylene terephthalate sheet, and the heating temperature is 160°C to 180°C when the polyester sheet is the polyethylene naphthalate sheet.

[0019] Further, preferably, the wafer is composed of any of Si, GaN, GaAs, and glass.

[0020] 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 not having a paste layer is used to integrate the frame and the wafer. The integrating step of integrating the frame and the wafer by the polyester sheet is performed by heat pressure bonding.

[0021] After the integration process is performed, the wafer is irradiated with a laser beam of a wavelength that is transmissive to the wafer, and the shield tunnel is formed continuously along the division predetermined line to divide the wafer. Then, air is blown from the polyester sheet side to lift the device chips one by one, and the device chips are picked up from the polyester sheet. The picked-up device chips are respectively mounted on prescribed mounting targets. In addition, when the device chips are lifted by air at the time of picking up, the load applied to the device chips at the time of peeling from the polyester sheet can be reduced.

[0022] When the shield tunnel is formed in the inside of the wafer, the light leakage of the laser beam reaches the polyester sheet. However, the polyester sheet does not have a paste layer, and thus the paste layer does not melt to adhere to the back side or the front side of the device chip.

[0023] That is, according to one embodiment of the present application, the frame unit can be formed using the polyester sheet that does not have a paste layer, and thus the adhesive tape having a paste layer is not required, and as a result, the quality reduction of the device chip due to the attachment of the paste layer does not occur.

[0024] Therefore, according to one embodiment of the present application, the processing method of the wafer is provided, and the paste layer does not adhere to the back side or the front side of the formed device chip, and the quality reduction of the device chip due to the attachment of the paste layer does not occur. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 (A) of FIG. 1 is a perspective view schematically showing the front side of a wafer, Figure 1 (B) of FIG. 1 is a perspective view schematically showing the back side of the wafer.

[0026] Figure 2 is a perspective view schematically showing a case where the wafer and a frame are positioned on a holding surface of a chuck table.

[0027] Figure 3 is a perspective view schematically showing a polyester sheet preparation process.

[0028] Figure 4 is a perspective view schematically showing an example of an integration process.

[0029] Figure 5 is a perspective view schematically showing another example of the integration process.

[0030] Figure 6 is a perspective view schematically showing still another example of the integration process.

[0031] Figure 7 (A) of FIG. 6 is a perspective view schematically showing a case where the polyester sheet is cut, Figure 7 (B) of FIG. 6 is a perspective view schematically showing a formed frame unit.

[0032] 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. Figure 8 (C) is a schematic perspective view of a shield tunnel.

[0033] Figure 9 It is a schematic perspective view showing the frame unit being moved into the pickup device.

[0034] 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.

[0035] Label Explanation

[0036] 1: Wafer; 1a: Front side; 1b: Back side; 3: Pre-defined dividing line; 3a: Shield tunnel; 3b: Fine hole; 3c: Amorphous region; 5: Device; 7: Frame; 7a: Opening; 9: Polyester sheet; 9a: Cutting mark; 11: Frame unit; 2: Chuck worktable; 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; 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: Air; 36: Collet. Detailed Implementation

[0037] Referring to the accompanying drawings, one embodiment of the present invention will be described. First, a wafer processed using the wafer processing method of this embodiment will be described. Figure 1 (A) is a perspective view schematically showing the front of chip 1. Figure 1 (B) is a perspective view schematically showing the back side of chip 1.

[0038] The wafer 1 is, for example, a generally circular substrate made of materials such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor materials, or materials such as sapphire, glass, or quartz. The glass is, for example, alkali glass, alkali-free glass, soda-lime glass, lead glass, borosilicate glass, or quartz glass.

[0039] 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, an LSI, an 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 processing method of the wafer 1 of the present embodiment, a shield tunnel is formed continuously in the wafer 1 along the division- scheduled lines 3, the wafer 1 is divided from the start of the shield tunnel, and thus each device chip is formed.

[0040] When the shield tunnel 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. Further, in the 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 by being transmitted through the wafer 1, and the laser beam is irradiated along the division- scheduled lines 3. Figure 1 Figure 1 Further, in the 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 by being transmitted through the wafer 1, and the laser beam is irradiated along the division- scheduled lines 3.

[0041] Before the wafer 1 is carried into the laser processing apparatus 12 (refer to (A) of FIG. 1) that performs laser processing of forming a shield tunnel in the wafer 1, the wafer 1, the polyester sheet, and the 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. Figure 8

[0042] 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, and thus the interval between the device chips is expanded, and the device chips are picked up by a pickup device.

[0043] The ring-shaped frame 7 (refer to FIG. 1, and the like) is formed of a material such as metal, for example, and has an opening 7a having a diameter larger than that of the wafer 1. When the frame unit is formed, the wafer 1 is positioned in the opening 7a of the frame 7 and is housed in the opening 7a. Figure 2 The polyester sheet 9 (refer to FIG. 1, and the like) is a resin sheet having flexibility, and the front surface and the back surface are flat. Further, 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 acid (a compound having two carboxyl groups) and diol (a compound having two hydroxyl groups) as monomers, and is a sheet that is transparent or translucent to visible light, such as a polyethylene terephthalate sheet or a polyethylene naphthalate sheet. However, the polyester sheet 9 is not limited thereto, and can be opaque.

[0044] Figure 3

[0045] ​​​​The polyester sheet 9 has no adhesiveness, and thus cannot be attached to the wafer 1 and the frame 7 at room temperature. However, the polyester sheet 9 has thermoplasticity, and thus can be attached to the wafer 1 and the frame 7 by locally melting when heated to a temperature near the melting point in a state where the polyester sheet 9 is joined to the wafer 1 and the frame 7 while a prescribed pressure is applied to one side. Therefore, in the processing method of the wafer 1 of the present embodiment, the wafer 1, the frame 7, and the polyester sheet 9 are integrated by the above-mentioned heat pressure bonding to form a frame unit.

[0046] Next, each process of the processing method of the wafer 1 of the present embodiment will be described. First, the polyester sheet provision process is performed in order to prepare for the integration of the wafer 1, the polyester sheet 9, and the frame 7. Figure 2 is a perspective view schematically showing a state where the wafer 1 and the frame 7 are positioned on the holding surface 2a of the chuck table 2. As shown in Figure 2 , the polyester sheet provision process is performed on the chuck table 2 having the holding surface 2a on the upper portion.

[0047] The chuck table 2 has a porous member having a larger diameter than the outer diameter of the frame 7 on the upper central portion. The upper surface of the porous member serves as the holding surface 2a of the chuck table 2. The chuck table 2 has an exhaust passage communicating with the porous member on the inside, as shown in Figure 3 , and an attraction source 2b is provided on the other end side of the exhaust passage. A switching portion 2c that switches between a communication state and a cutoff state is provided on the exhaust passage, and when the switching portion 2c is in the communication state, a negative pressure generated by the attraction source 2b is applied to an object placed on the holding surface 2a, thereby attracting and holding the object to the chuck table 2.

[0048] In the polyester sheet provision process, first, as shown in Figure 2 , 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 inside the opening 7a of the frame 7.

[0049] 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 the irradiated surface of the laser beam is to be in the division process 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 processing method of the wafer 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.

[0050] 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 provided on the back surface lb (or the front surface la) of the wafer 1 and on the outer periphery of the frame 7. Figure 3is a perspective view schematically showing a polyester sheet disposing step. As shown in Figure 3 The polyester sheet 9 is disposed on the wafer 1 and the frame 7 in a manner of covering them.

[0051] In addition, in the polyester sheet disposing step, 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 step to be performed later, if the entire holding surface 2a is not covered with the polyester sheet 9, the negative pressure leaks from the gap, and the pressure cannot be properly applied to the polyester sheet 9.

[0052] In the wafer 1 processing method of the present embodiment, next, the integration step is performed, and the polyester sheet 9 is heated and the wafer 1 and the frame 7 are integrated by the polyester sheet 9 by heat pressure bonding. Figure 4 is a perspective view schematically showing an example of the integration step. In Figure 4 , components that can be visually recognized through the polyester sheet 9 that is transparent or translucent to visible light are indicated by broken lines.

[0053] In the integration step, first, the switching portion 2c of the chuck table 2 is made to operate to become 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.

[0054] Next, heat pressure bonding is performed by heating the polyester sheet 9 while attracting the polyester sheet 9 by the suction source 2b. 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 .

[0055] 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 heat and eject air. The hot air gun 4 provides hot air 4a to the polyester sheet 9 from the upper surface while applying negative pressure to the polyester sheet 9, and when the polyester sheet 9 is heated to a predetermined temperature, the polyester sheet 9 is heat pressure bonded to the wafer 1 and the frame 7.

[0056] 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 by a member heated to a predetermined temperature. Figure 5 is a perspective view schematically showing another example of the integration step. In Figure 5 , components that can be visually recognized through the polyester sheet 9 that is transparent or translucent to visible light are indicated by broken lines.

[0057] In Figure 5In the shown integrated process, for example, a heating roller 6 having a heat source inside is used. In Figure 5 In 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 by atmospheric pressure.

[0058] Then, the heating roller 6 is heated to a prescribed temperature and is placed on one end of the holding surface 2a of the chuck table 2. Then, the heating roller 6 is made to rotate and roll 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 the direction of pressing it down by the heating roller 6, thermocompression-bonding is performed using a pressure greater than atmospheric pressure. In addition, the surface of the heating roller 6 is preferably coated with a fluororesin.

[0059] In addition, instead of the heating roller 6, a press member in the shape of an iron having a flat bottom plate with a heat source inside can be used to perform thermocompression-bonding of the polyester sheet 9. In this case, the press member is heated to a prescribed temperature to become a hot plate, and the polyester sheet 9 held by the chuck table 2 is pressed from above by the press member.

[0060] Thermocompression-bonding of the polyester sheet 9 can also be performed by other methods. Figure 6 is a perspective view schematically showing another example of an integrated process. In Figure 6 In, components that can be seen through the polyester sheet 9 that is transparent or translucent to visible light are shown by dotted lines. In Figure 6 In the shown integrated process, the polyester sheet 9 is heated using an infrared lamp 8 provided above the chuck table 2. The infrared lamp 8 is capable of irradiating at least the wavelength of infrared rays 8a to which the material of the polyester sheet 9 has absorbency.

[0061] In Figure 6 In 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 being irradiated with the infrared rays 8a. Thus, the polyester sheet 9 is thermocompression-bonded to the wafer 1 and the frame 7.

[0062] When the polyester sheet 9 is heated to a temperature near its melting point 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 portion 2c is made to operate, and the communication state of the porous member of the chuck table 2 with the suction source 2b is released, and thus the chuck table 2 is released from suction.

[0063] 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 schematically showing a case where the polyester sheet 9 is cut. Regarding the cutting, as shown in (A) of FIG. 10, 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

[0064] 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 by sandwiching the polyester sheet 9 with the frame 7 and the cutter 10. As a result, a cut mark 9a is formed on the polyester sheet 9.

[0065] 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 this region of the polyester sheet 9 remains. As a result, the unnecessary part of the polyester sheet 9 including the region that protrudes from the outer periphery of the frame 7 can be removed.

[0066] 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 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 schematically showing the frame unit 11 that is formed.

[0067] In addition, when performing the thermal compression bonding, 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 thermal compression 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.

[0068] In addition, there are cases where a part of the polyester sheet 9 does not have a clear softening point. Therefore, when performing the thermal compression bonding, the polyester sheet 9 is preferably heated to a temperature above 20°C lower than the melting point thereof and below the melting point thereof.

[0069] 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.

[0070] ​Here, heating temperature refers to the temperature of the polyester sheet 9 during the integrated process. For example, in the actual use of heat sources such as the hot air gun 4, heating roller 6, and infrared lamp 8, a model capable of setting the output temperature is used. However, even when using this heat source to heat the polyester sheet 9, 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 the specified temperature, the output temperature of the heat source can be set higher than the melting point of the polyester sheet 9.

[0071] Next, in the wafer processing method of this embodiment, a dicing process is performed, in which the wafer 1, which has become a frame unit 11, is laser-processed to diced the wafer 1 by continuously forming shield tunnels along the predetermined dicing line 3. The dicing process utilizes, for example, [the following method is used]. Figure 8 The laser processing apparatus shown in (A) is used to carry out the process. 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.

[0072] The laser processing apparatus 12 includes: a laser processing unit 14 that irradiates a wafer 1 with a laser beam 16; and a chuck stage (not shown) for holding the wafer 1. The laser processing unit 14 has a laser oscillator (not shown) capable of oscillating laser light, and is capable of emitting a laser beam 16 with a wavelength that is transparent to the wafer 1. The chuck stage is capable of moving (processing feed) in a direction parallel to the upper surface.

[0073] 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. The processing head 14a has a focusing lens (not shown) inside. The numerical aperture (NA) of this focusing lens is determined such that the value obtained by dividing the numerical aperture (NA) by the refractive index (N) of the wafer 1 is in the range of 0.05 to 0.2.

[0074] 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.

[0075] Next, the chuck table and the laser processing unit 14 are relatively moved along a processing feed direction parallel to the upper surface of the chuck table while the laser beam 16 is continuously irradiated from the laser processing unit 14 to the inside of the wafer 1. That is, the focal point 14b of the laser beam 16 is positioned at the inside of the wafer 1, and the laser beam 16 is irradiated to the wafer 1 along the division predetermined line 3.

[0076] Thus, the region called a shield tunnel 3a in the form of a filament is continuously formed along the division predetermined line 3. In Figure 8 (B) of FIG. 10, a cross-sectional view of the wafer 1 in which the shield tunnels 3a are continuously formed is schematically shown. Further, Figure 8 (C) of FIG. 10 is a perspective view schematically showing the shield tunnels 3a. The shield tunnels 3a are composed of fine holes 3b along the thickness direction of the wafer 1 and amorphous regions 3c surrounding the fine holes 3b. Further, in Figure 8 (A) of FIG. 10, the shield tunnels 3a aligned along the division predetermined line 3 are shown by solid lines.

[0077] The irradiation conditions of the laser beam 16 in the division process are set as follows, for example. However, the irradiation conditions of the laser beam 16 are not limited to this.

[0078] Wavelength: 1030 nm

[0079] Average output: 3 W

[0080] Repetition frequency: 50 kHz

[0081] Pulse width: 10 ps

[0082] Condensing spot diameter:

[0083] Feed rate: 500 mm / sec

[0084] When the laser beam 16 is thus irradiated to the wafer 1, the shield tunnels 3a are formed in the wafer 1 at intervals of 10 μm along the division predetermined line 3. Further, each of the shield tunnels 3a thus formed contains the fine holes 3b on the left and right and the amorphous regions 3c on the left and right. Therefore, the shield tunnels 3a adjacent to each other are connected in the manner as shown in Figure 8 (B) of FIG. 10, in which the amorphous regions 3c of the shield tunnels 3a are connected to each other.

[0085] After the shield tunnels 3a are formed in the wafer 1 along the one set of the division predetermined lines 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 wafer 1 is laser-processed along the other set of the division predetermined lines 3. After the shield tunnels 3a are formed along all the division predetermined lines 3 in the one direction, the chuck table is rotated around the axis perpendicular to the holding surface, and the wafer 1 is laser-processed along the division predetermined lines 3 in the other direction.

[0086] Here, when the shield tunnels 3a are formed in the wafer 1 by the laser processing unit 14 irradiating the laser beam 16, the stray light of the laser beam 16 reaches the polyester sheet 9 below the wafer 1.

[0087] For example, in the case where the polyester sheet 9 is not used in the frame unit 11 but an adhesive tape is used, when the stray light of the laser beam 16 is irradiated to the paste layer of the adhesive tape, the paste layer of the adhesive tape is melted, and a part of the paste layer is fixed to the back surface Ib side of the wafer 1. In this case, the part of the paste layer remains on the back surface side of the device chip formed by dividing the wafer 1. Therefore, the quality of the device chip becomes a problem.

[0088] On the contrary, in the wafer processing method of the embodiment, the polyester sheet 9 having no paste layer is used in the frame unit 11. Therefore, even if the stray light of the laser beam 16 reaches the polyester sheet 9, the paste layer is not fixed to the back surface Ib side of the wafer 1. Therefore, the quality of the device chip formed from the wafer 1 is kept good.

[0089] Next, the wafer 1 is divided to form device chips by expanding the polyester sheet 9 to the radial outside. Then, a pickup process is performed to pick up each of the device chips from the polyester sheet 9. In the expansion of the polyester sheet 9, the pickup device 18 shown in the lower part is used. Figure 9 The pickup device 18 is schematically shown in a perspective view in which the frame unit 11 is carried into the pickup device 18. Figure 9 The pickup device 18 is schematically shown in a perspective view in which the frame unit 11 is carried into the pickup device 18.

[0090] The pickup device 18 has a drum 20 having a larger diameter 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 having a larger diameter than the diameter of the drum 20, and is disposed at the same height as the upper end of the drum 20 to surround the upper end of the drum 20 from the outer peripheral side.

[0091] A jig 24 is provided 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 jig 24, the frame unit 11 is fixed to the frame support table 26.

[0092] The frame support table 26 is supported by a plurality of rods 28 extending in the vertical direction, and a cylinder 30 that raises and lowers the rod 28 is provided at the lower end of each rod 28. The plurality of cylinders 30 are supported by a base 32 in the shape of a circular plate. When each cylinder 30 is operated, the frame support table 26 is lowered with respect to the drum 20.

[0093] A raising mechanism 34 that raises the device chip supported by the polyester sheet 9 from below is provided inside the drum 20. The raising mechanism 34 has a function of blowing air 34a upward. In addition, a collet 36 that can suction and hold the device chip is provided above the drum 20 (see Figure 10 (B) of FIG. 8). The raising mechanism 34 and the collet 36 are movable in the horizontal direction along the upper surface of the frame support table 26. In addition, the collet 36 is connected to a suction source 36a (see Figure 10 (B) of FIG. 8) via a switching section 36b (see Figure 10 (B) of FIG. 8).

[0094] When the polyester sheet 9 is expanded, first, the height of the frame support table 26 is adjusted by operating the cylinder 30 so that the height of the upper end of the drum 20 of the pickup 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 and the frame support table 26 of the pickup device 18.

[0095] Then, the frame 7 of the frame unit 11 is fixed to the frame support table 26 by the jig 24. Figure 10 (A) of FIG. 7 is a cross-sectional view that schematically shows the frame unit 11 fixed to the frame support table 26. The shield tunnel 3a parallel to the division predetermined line 3 is formed in the wafer 1.

[0096] Next, the frame support table 26 of the frame holding unit 22 is lowered with respect to the drum 20 by operating the cylinder 30. Then, as shown in Figure 10 (B) of FIG. 8, the polyester sheet 9 is expanded to the radial outside. Figure 10 (B) of FIG. 8 is a cross-sectional view that schematically shows the expanded polyester sheet 9.

[0097] When the polyester sheet 9 is expanded, a force toward the radial outside is applied to the wafer 1, and the wafer 1 is divided from the shield tunnel 3a as a starting point, and each device chip 1c is formed. When the polyester sheet 9 is further expanded, the interval between each device chip 1c supported by the polyester sheet 9 is expanded, and the pickup of each device chip 1c becomes easy.

[0098] In the wafer processing method of the present embodiment, after the wafer 1 is divided to form individual device chips 1c, a pickup process is performed to pick up the device chips 1c from the polyester sheet 9. In the pickup process, the device chip 1c that is the pickup target is determined, the jacking mechanism 34 is moved to below the device chip 1c, and the collet 36 is moved to above the device chip 1c.

[0099] Then, the jacking mechanism 34 is activated to blow air 34a from the polyester sheet 9 side to lift the device chip 1c. Then, the switching section 36b is activated to communicate the collet 36 with the suction source 36a. Thus, the device chip 1c is suction-held by the collet 36, and the device chip 1c is picked up from the polyester sheet 9. The picked-up individual device chips 1c are used after being mounted on a prescribed wiring substrate or the like.

[0100] In addition, when the device chip 1c is lifted by blowing air 34a from the polyester sheet 9 side, the load applied to the device chip 1c when the device chip 1c is peeled from the polyester sheet 9 can be reduced.

[0101] For example, in the case where the frame unit 11 is formed using an adhesive tape, in the division process, the light leakage of the laser beam 16 irradiated to the wafer 1 reaches the adhesive tape, and the paste layer of the adhesive tape is fixed to the back surface side of the device chip. Also, the quality of the device chip due to the attachment of the paste layer becomes a problem.

[0102] In contrast, according to the wafer processing method of the present embodiment, the frame unit 11 using the polyester sheet 9 that does not have a paste layer can be formed by thermal compression bonding, and thus an adhesive tape having a paste layer is not required. As a result, the quality reduction of the device chip due to the attachment of the paste layer to the back surface side does not occur.

[0103] In addition, the present application is not limited to the description of the above-described embodiments, and various modifications can be made and implemented. For example, in the above-described embodiments, the case where the polyester sheet 9 is, for example, a polyethylene terephthalate sheet or a polyethylene naphthalate sheet is described, but one embodiment of the present application is not limited thereto. For example, the polyester sheet can be made of other materials, and can be a polytrimethylene terephthalate sheet, a polybutylene terephthalate sheet, a polybutylene naphthalate sheet, or the like.

[0104] In addition to the above, the configuration, method, and the like of the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present application.

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 having an opening for receiving the wafer, and a polyester sheet without a paste layer is placed on the back or front of the wafer and on the outer periphery of the frame. In the integration process, the polyester sheet is heated and then hot-pressed to integrate the wafer and the frame together using the polyester sheet. The dicing process involves focusing a laser beam of a wavelength transparent to the wafer onto the interior of the wafer, irradiating the wafer with the laser beam along a predetermined dicing line, continuously forming a shield tunnel within the wafer, and dividing the wafer into individual device chips; and In the pickup process, air is blown from the polyester sheet side to lift the device chips one by one, and each device chip is picked up from the polyester sheet. If the polyester sheet is not heated, it cannot be integrated with the wafer and the frame.

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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