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 giving ultrasonic waves to 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 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 giving ultrasonic waves to the polyester sheet in each region of the polyester sheet corresponding to the individual device chips, and picking up the device chips from the polyester sheet by lifting the device chips from the polyester sheet.

[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 that has been projected from the outer periphery of the frame is removed after the integration is performed.

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

[0017] Further, preferably, the polyester sheet is any one 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 one 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, and 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 wafer is divided by continuously forming a shield tunnel along the division predetermined line. Then, in each region of the polyester sheet corresponding to each device chip, the polyester sheet is given ultrasonic waves, and the device chip is lifted from the polyester sheet side, and the device chip is picked up from the polyester sheet. The picked-up device chips are respectively mounted on prescribed mounting objects. In addition, when the polyester sheet is given ultrasonic waves at the time of picking up, peeling of the polyester sheet becomes easy, and thus the load applied to the device chip can be reduced.

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

[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 an adhesive tape having a paste layer is not needed, and as a result, a decrease in quality of the device chip due to attachment of the paste layer does not occur.

[0024] Thus, according to one embodiment of the present application, a wafer processing method is provided, in which a paste layer is not attached to the back surface side or the front surface side of the formed device chip, and a decrease in quality of the device chip due to 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 a front surface of a wafer, Figure 1 (B) of FIG. 1 is a perspective view schematically showing a back surface 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(A) of FIG. 1 is a perspective view schematically showing a wafer 1.

[0032] Figure 8 (A) of FIG. 1 is a perspective view schematically showing a wafer 1. Figure 8 (B) of FIG. 1 is a sectional view schematically showing a wafer 1. Figure 8 (C) of FIG. 1 is a perspective view schematically showing a shield tunnel 3a.

[0033] Figure 9 (A) of FIG. 1 is a perspective view schematically showing a wafer 1.

[0034] Figure 10 (A) of FIG. 1 is a perspective view schematically showing a wafer 1. Figure 10 (B) of FIG. 1 is a sectional view schematically showing a wafer 1.

[0035] Explanation of Reference Numerals

[0036] 1: wafer; 1a: front surface; 1b: back surface; 3: division intended line; 3a: shield tunnel; 3b: fine hole; 3c: amorphous region; 5: device; 7: frame; 7a: opening; 9: polyester sheet; 9a: cut mark; 11: frame unit; 2: chuck table; 2a: holding surface; 2b, 36a: suction source; 2c, 36b: switching section; 4: hot air gun; 4a: hot air; 6: heating roller; 8: infrared lamp; 8a: infrared ray; 10: cutter; 12: laser processing apparatus; 14: laser processing unit; 14a: processing head; 14b: condensing point; 16: laser beam; 18: pickup device; 20: drum; 22: frame holding unit; 24: jig; 26: frame support table; 28: rod; 30: air cylinder; 32: base; 34: jacking mechanism; 34a: ultrasonic vibrator; 36: collet. DETAILED DESCRIPTION

[0037] An embodiment of one mode of the present application will be described with reference to the drawings. First, a wafer processed by a processing method using the wafer of the present embodiment will be described. Figure 1 (A) of FIG. 1 is a perspective view schematically showing a wafer 1. Figure 1 (B) of FIG. 1 is a sectional view schematically showing a wafer 1.

[0038] 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.

[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 shield tunnel as a starting point, 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 the 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 the 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 section 2c that switches between a communication state and a cutoff state is provided on the exhaust passage, and when the switching section 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, while continuously irradiating the interior of the wafer 1 with the 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 focusing 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.

[0076] Thus, along the predetermined dividing line 3, filamentary regions known as shield tunnel 3a are continuously formed. Figure 8 In (B), a cross-sectional view of a wafer 1 in which a shield tunnel 3a is continuously formed is schematically shown. Additionally, Figure 8 (C) is a schematic perspective view of the shield tunnel 3a. The shield tunnel 3a is composed of a fine hole 3b along the thickness direction of the wafer 1 and an amorphous region 3c surrounding the fine hole 3b. Furthermore, in Figure 8 In (A), the shield tunnels 3a running parallel to each other along the predetermined dividing line 3 are shown in solid lines.

[0077] 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.

[0078] Wavelength: 1030nm

[0079] Average output: 3W

[0080] Repetition frequency: 50kHz

[0081] Pulse width: 10ps

[0082] Focused beam diameter:

[0083] Feed rate: 500 mm / s

[0084] When the laser beam 16 is irradiated onto the wafer 1, shield tunnels 3a are formed in the wafer 1 at 10 μm intervals along the predetermined dividing line 3. Furthermore, each formed shield tunnel 3a contains... The fine pores 3b on the left and right and The left and right amorphous regions 3c. Therefore, the adjacent shield tunnels 3a are as follows: Figure 8 As shown in (B), this is the way the amorphous regions 3c are connected to each other.

[0085] After forming a shield tunnel 3a in 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 laser processing is performed on the wafer 1 along the other predetermined dividing lines 3 in the same way. After forming a shield tunnel 3a along all predetermined dividing lines 3 in one direction, the chuck stage is rotated about an axis perpendicular to the holding surface, and laser processing is performed on the wafer 1 along predetermined dividing lines 3 in another direction in the same way.

[0086] Here, when a laser beam 16 is irradiated onto the wafer 1 by the laser processing unit 14 to form a shield tunnel 3a, the leakage light from the laser beam 16 reaches the polyester sheet 9 below the wafer 1.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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 an ultrasonic transducer 34a at its upper end, which is made of, for example, piezoelectric ceramics such as lead zirconate titanate (PZT), barium titanate, or lead titanate, or a crystal transducer. 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.

[0094] 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.

[0095] 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. Shield tunnels 3a are formed in the wafer 1, arranged side by side along a predetermined dividing line 3.

[0096] 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.

[0097] As the polyester sheet 9 expands, a radially outward force is applied to the wafer 1, dividing the wafer 1 from the shield tunnel 3a into individual device chips 1c. When the polyester sheet 9 is further expanded, the spacing between the individual device chips 1c supported by the polyester sheet 9 is increased, making it easier to pick up each device chip 1c.

[0098] 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.

[0099] Then, the ultrasonic transducer 34a is activated to generate vibrations at the frequency of the ultrasonic band, and the ultrasonic transducer 34a contacts the area of ​​the polyester sheet 9 corresponding to the device chip 1c, thereby imparting ultrasonic waves to that area. Next, the lifting mechanism 34 is activated to lift the device chip 1c from the polyester sheet 9 side. Then, the switching unit 36b is activated to connect the collet 36 to the suction source 36a. The device chip 1c is then held and attracted by the collet 36, and picked up from the polyester sheet 9. Each picked-up device chip 1c is subsequently mounted on a specified wiring board or the like for use.

[0100] Furthermore, when ultrasonic waves are applied to this region of the polyester sheet 9 using the ultrasonic transducer 34a, the polyester sheet 9 is easier to peel off. Therefore, the load applied to the device chip during peeling from the polyester sheet 9 can be reduced.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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 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: the wafer processing method comprising: a polyester sheet-provisioning step of positioning the wafer in an opening of a frame having the opening to receive the wafer, and provisioning a polyester sheet not having a paste layer on the back surface or the front surface of the wafer and on the outer periphery of the frame so that the polyester sheet directly contacts the wafer and the frame; an integration step of heating the polyester sheet not having the paste layer, and integrally forming a frame unit by thermally pressure-bonding the wafer and the frame with 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, irradiating the wafer with the laser beam along the division predetermined line, continuously forming a shield tunnel in the wafer, and dividing the wafer into individual device chips; and a pickup step of imparting ultrasonic waves to 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.

2. The wafer processing method according to claim 1, characterized in that: in the integration step, the thermally pressure-bonding is performed by irradiation of infrared rays.

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

4. The wafer processing method according to claim 1, characterized in that: in the pickup step, the polyester sheet is expanded to expand the interval between the device chips.

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

6. The wafer processing method according to claim 5, characterized in that: in the integration step, the heating temperature is 250°C to 270°C in the case where the polyester sheet is the polyethylene terephthalate sheet, and the heating temperature is 160°C to 180°C in the case where the polyester sheet is the polyethylene naphthalate sheet.

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

Images