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 polyolefin sheet arrangement step of positioning the wafer in an opening of a frame having an opening for receiving the wafer, and arranging a polyolefin 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 polyolefin sheet, and integrally joining the wafer and the frame by the polyolefin 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 to form a shield tunnel in the wafer, and dividing the wafer into individual device chips; and a pickup step of heating the polyolefin sheet, lifting the device chips, and picking up the device chips.

Description

Technical Field

[0001] The present invention relates to a method for processing wafers, which divides a wafer having multiple devices formed in different areas on the front side by predetermined dividing lines into individual device chips. Background Technology

[0002] In the manufacturing process of device chips used in electronic devices such as mobile phones or personal computers, multiple intersecting predetermined dividing lines (spacers) are first formed on the front side of a wafer made of materials such as semiconductors. Then, devices such as ICs (Integrated Circuits), LSIs (Large-Scale Integration Circuits), and LEDs (Light Emitting Diodes) are formed within the areas divided by these predetermined dividing lines.

[0003] Then, an adhesive tape, called a dicing tape, is attached to the back or front of the wafer in a manner that seals the opening on the annular frame, forming a frame unit that integrates the wafer, the adhesive tape, and the annular frame. Furthermore, when the wafer contained within the frame unit is processed and diced along the predetermined dicing lines, individual device chips are formed.

[0004] Laser processing apparatus is used, for example, in wafer dicing. The laser processing apparatus includes: a chuck stage that holds the wafer through an adhesive tape; and a laser processing unit that irradiates the wafer with a laser beam of a wavelength that is transparent to the wafer while the focal point is positioned inside the wafer.

[0005] During wafer dicing, a frame unit is placed on a chuck stage, and the wafer is held on the chuck stage by an adhesive tape. Then, while the chuck stage and the laser processing unit move relative to each other in a direction parallel to the upper surface of the chuck stage, the laser processing unit continuously irradiates the wafer along each predetermined dicing line.

[0006] When the laser beam is irradiated onto the wafer, filamentary regions known as shield tunnels are continuously formed along the predetermined slicing line. The shield tunnel consists of a fine hole along the thickness direction of the wafer and an amorphous region surrounding the fine hole, serving as the starting point for wafer slicing (see Patent Document 1).

[0007] Then, the frame unit is removed from the laser processing apparatus, and the wafer is divided into individual device chips as the adhesive tape is extended radially outward. When picking up the formed device chips from the adhesive tape, the adhesive tape is pre-treated by irradiating it with ultraviolet light to reduce the adhesive force of the adhesive tape. As a processing apparatus with high production efficiency for device chips, there is a known processing apparatus that can continuously perform wafer dicing and ultraviolet irradiation of the adhesive tape in one device (see Patent Document 2).

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

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

[0010] The adhesive tape comprises, for example, a substrate layer formed of a vinyl chloride sheet and a paste layer disposed on the substrate layer. In a laser processing apparatus, a laser beam is irradiated into the interior of a wafer to form a shield tunnel serving as a dicing starting point. At this time, a portion of the leaked light from the laser beam reaches the paste layer of the adhesive tape. Furthermore, due to the heat effect caused by the laser beam irradiation, the paste layer of the adhesive tape melts, and a portion of the paste layer adheres to the back or front side of the device chip formed from the wafer.

[0011] In this situation, even if the adhesive tape is treated with ultraviolet light or similar methods to pick up the device chip from the adhesive tape, a portion of the paste layer will remain on the back or front side of the picked-up device chip. Therefore, a decrease in the quality of the device chip becomes a problem. Summary of the Invention

[0012] The present invention was made in view of this problem and its object is to provide a wafer processing method that does not attach a paste layer to the back or front side of the formed device chip, and does not cause a quality reduction on the device chip due to the adhesion of the paste layer.

[0013] According to one aspect of the present invention, a wafer processing method is provided, which divides a wafer having multiple devices formed in each region of the front side divided by a predetermined dividing line into individual device chips. The wafer processing method is characterized by comprising the following steps: a polyolefin sheet placement step, in which the wafer is positioned within the opening of a frame having an opening for receiving the wafer, and a polyolefin sheet is placed on the back or front side of the wafer and on the outer periphery of the frame; an integration step, in which the polyolefin sheet is heated and the wafer and the frame are integrated by thermoforming using the polyolefin sheet; a slicing step, in which a focusing point of a laser beam of a wavelength transparent to the wafer is positioned inside the wafer, and the laser beam is irradiated onto the wafer along the predetermined dividing line to continuously form a shield tunnel in the wafer, thereby slicing the wafer into individual device chips; and a pickup step, in which the polyolefin sheet is heated in each region of the polyolefin sheet corresponding to each device chip, and the device chip is lifted from the polyolefin sheet side and picked up from the polyolefin sheet.

[0014] Preferably, the hot pressing is performed by infrared irradiation in this integrated process.

[0015] In addition, preferably, in this integrated process, after integration is performed, the polyolefin sheets protruding from the periphery of the frame are removed.

[0016] In addition, it is preferable that the polyolefin sheet is expanded during the picking process to increase the spacing between the device chips.

[0017] In addition, the polyolefin sheet is preferably any sheet selected from polyethylene sheet, polypropylene sheet, and polystyrene sheet.

[0018] In addition, preferably in this integrated process, when the polyolefin sheet is a polyethylene sheet, the heating temperature is 120°C to 140°C; when the polyolefin sheet is a polypropylene sheet, the heating temperature is 160°C to 180°C; and when the polyolefin sheet is a polystyrene sheet, the heating temperature is 220°C to 240°C.

[0019] In addition, the wafer is preferably made of any material selected from Si, GaN, GaAs, and glass.

[0020] In one embodiment of the wafer processing method of the present invention, when forming the frame unit, instead of using an adhesive tape with a paste layer, a polyolefin sheet without a paste layer is used to integrate the frame and the wafer. The integration process of integrating the frame and the wafer using the polyolefin sheet is achieved through thermoforming.

[0021] After the integration process, the wafer is irradiated with a laser beam of a wavelength that is transparent to the wafer, and the wafer is segmented by continuously forming a shield tunnel along a predetermined segmentation line. Then, the polyolefin sheet is heated in each region corresponding to each device chip, and the device chip is lifted from the polyolefin sheet side and picked up from the polyolefin sheet. The picked-up device chips are then mounted on designated mounting objects. In addition, when the polyolefin sheet is heated during pickup, the adhesive force of the polyolefin sheet is reduced, which can reduce the load applied to the device chip.

[0022] When a shield tunnel is formed inside the wafer, the laser beam leaks into the polyolefin substrate. However, the polyolefin substrate does not have a paste layer, so the paste layer does not melt and adhere to the back or front side of the device chip.

[0023] That is, according to one aspect of the present invention, a framework unit can be formed using a polyolefin sheet without a paste layer, thus eliminating the need for adhesive tape with a paste layer, and as a result, no degradation in the quality of the device chip due to the adhesion of the paste layer occurs.

[0024] Therefore, according to one aspect of the present invention, a wafer processing method is provided that does not attach a paste layer to the back or front side of the formed device chip, and does not cause a reduction in quality on the device chip due to the adhesion of the paste layer. Attached Figure Description

[0025] Figure 1 (A) is a schematic perspective view of the front of the chip. Figure 1 (B) is a schematic perspective view of the back side of the chip.

[0026] Figure 2 This is a perspective view schematically illustrating the positioning of the wafer and frame on the holding surface of the chuck stage.

[0027] Figure 3 This is a three-dimensional diagram schematically illustrating the assembly process of polyolefin sheets.

[0028] Figure 4 This is a perspective view schematically illustrating an example of an integrated process.

[0029] Figure 5 This is a perspective view schematically illustrating another example of an integrated process.

[0030] Figure 6 This is a perspective view that schematically illustrates another example of an integrated process.

[0031] Figure 7 (A) is a schematic perspective view showing the cutting of a polyolefin sheet. Figure 7(B) is a schematic three-dimensional view showing the 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-cut dividing line; 3a: Shield tunnel; 3b: Fine hole; 3c: Amorphous region; 5: Device; 7: Frame; 7a: Opening; 9: Polyolefin 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: Heating part; 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 side 1a of wafer 1 is divided by multiple predetermined dividing lines 3 arranged in a grid pattern. Furthermore, devices 5 such as ICs, LSIs, and LEDs are formed in each region defined by the predetermined dividing lines 3 on the front side 1a of wafer 1. In the wafer 1 fabrication method of this embodiment, a shield tunnel is continuously formed in wafer 1 along the predetermined dividing lines 3, and wafer 1 is divided starting from this shield tunnel to form individual device chips.

[0040] When a shield tunnel is formed in wafer 1, a laser beam of wavelength that is transparent to wafer 1 is irradiated along the predetermined dividing line 3, and the laser beam is focused into the interior of wafer 1. At this time, the laser beam can... Figure 1 (A) shows the front side 1a side irradiated onto the wafer 1, or it can also be from... Figure 1 The back side 1b shown in (B) is irradiated onto the wafer 1. In addition, when the laser beam is irradiated onto the wafer 1 from the back side 1b, an alignment unit with an infrared camera is used to detect the pre-defined dividing line 3 on the front side 1a through the wafer 1, and the laser beam is irradiated along the pre-defined dividing line 3.

[0041] The laser processing apparatus 12 (see reference) is used to move wafer 1 into the laser processing device 12 that performs laser processing to form a shield tunnel in wafer 1. Figure 8 Prior to (A), the wafer 1, the polyolefin substrate, and the frame are integrated to form a frame unit. The wafer 1, in the form of a frame unit, is moved into the laser processing apparatus 12 for processing.

[0042] Furthermore, when the polyolefin sheet is expanded, the wafer 1 can be divided, and the individual device chips formed by dividing the wafer 1 are supported on the polyolefin sheet. Then, the polyolefin sheet is further expanded, thereby expanding the spacing between the device chips, and the device chips are picked up by a pickup device.

[0043] 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.

[0044] Polyolefin series 9 (reference) Figure 3 The polyolefin sheet 9 (etc.) is a flexible resin-based sheet with a flat front and back. Furthermore, the polyolefin sheet 9 has a diameter larger than the outer diameter of the frame 7 and does not have a paste layer. The polyolefin sheet 9 is a sheet of a polymer synthesized using olefins as monomers, such as polyethylene sheets, polypropylene sheets, or polystyrene sheets, which are transparent or translucent to visible light. However, the polyolefin sheet 9 is not limited to these and can also be opaque.

[0045] The polyolefin sheet 9 lacks adhesive properties and therefore cannot be bonded to the wafer 1 and frame 7 at room temperature. However, the polyolefin sheet 9 is thermoplastic, so when heated to a temperature near its melting point while being bonded to the wafer 1 and frame 7 under a specified pressure, the polyolefin 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 polyolefin sheet 9 are integrated by thermoforming as described above to form a frame unit.

[0046] Next, each step of the wafer 1 processing method of this embodiment will be described. First, a polyolefin sheet arrangement step is performed in order to prepare for the integration of wafer 1, polyolefin 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. (As shown) Figure 2 As shown, a polyolefin sheet assembly process is performed on a chuck worktable 2 with a holding surface 2a on the upper part.

[0047] 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.

[0048] In the polyolefin sheet preparation process, the first step is as follows: Figure 2 As shown, a wafer 1 and a frame 7 are placed on the holding surface 2a of the chuck stage 2, and the wafer 1 is positioned within the opening 7a of the frame 7.

[0049] At this point, the orientation of wafer 1 is selected based on whether the surface irradiated by the laser beam in the dicing process described later is the front side 1a or the back side 1b. For example, if the irradiated surface is the front side 1a, the front side 1a is oriented downwards. Similarly, if the irradiated surface is the back side 1b, the back side 1b is oriented downwards. Hereinafter, the wafer processing method of this embodiment will be described using the case where the surface irradiated by the laser beam is the front side 1a as an example, but the orientation of wafer 1 is not limited to this.

[0050] After placing the wafer 1 and the frame 7 on the holding surface 2a of the chuck stage 2, a polyolefin sheet 9 is disposed on the back side 1b (or front side 1a) of the wafer 1 and on the outer periphery of the frame 7. Figure 3This is a schematic perspective view illustrating the assembly process of polyolefin sheets. For example... Figure 3 As shown, polyolefin sheets 9 are arranged on both wafer 1 and frame 7 in a manner that covers both.

[0051] Furthermore, in the polyolefin sheet installation process, a polyolefin sheet 9 with a diameter larger than the holding surface 2a of the chuck table 2 is used. This is because, when the negative pressure of the chuck table 2 is applied to the polyolefin sheet 9 in the subsequent integrated process, if the polyolefin sheet 9 does not cover the entire holding surface 2a, the negative pressure will leak from the gap, making it impossible to apply appropriate pressure to the polyolefin sheet 9.

[0052] In the wafer 1 processing method of this embodiment, an integration process is then performed, in which the polyolefin sheet 9 is heated and the wafer 1 and the frame 7 are integrated by means of the polyolefin sheet 9 through hot pressing. Figure 4 This is a perspective view schematically illustrating an example of an integrated process. Figure 4 In the diagram, dashed lines represent components that can be seen through the polyolefin sheet 9, which is transparent or translucent to visible light.

[0053] In the integrated process, the switching part 2c of the chuck stage 2 is first activated to connect the suction source 2b to the porous component on the upper part of the chuck stage 2, and the negative pressure of the suction source 2b is applied to the polyolefin sheet 9. Then, atmospheric pressure is used to make the polyolefin sheet 9 adhere tightly to the wafer 1 and the frame 7.

[0054] Next, hot pressing is performed by simultaneously attracting the polyolefin sheet 9 through the attraction source 2b and heating the polyolefin sheet 9. The heating of the polyolefin sheet 9 is, for example, as follows: Figure 4 As shown, this is achieved using a hot air gun 4 mounted above the chuck worktable 2.

[0055] The hot air gun 4 has a heating unit such as an electric heating wire and a fan and other air supply mechanism inside, which can heat the air and spray it. While applying negative pressure to the polyolefin sheet 9, hot air 4a is supplied to the polyolefin sheet 9 from the upper surface through the hot air gun 4. When the polyolefin sheet 9 is heated to the specified temperature, the polyolefin sheet 9 is hot-pressed onto the wafer 1 and the frame 7.

[0056] Alternatively, heating of the polyolefin sheet 9 can also be implemented by other methods, such as pressing the wafer 1 and frame 7 from above using a component heated to a specified temperature. Figure 5 This is a perspective view schematically illustrating another example of an integrated process. Figure 5 In the diagram, dashed lines represent components that can be seen through the polyolefin sheet 9, which is transparent or translucent to visible light.

[0057] exist Figure 5In the integrated process shown, for example, a heating roller 6 with an internal heat source is used. Figure 5 In the integrated process shown, the negative pressure of the attraction source 2b is first applied to the polyolefin sheet 9, and atmospheric pressure is used to make the polyolefin sheet 9 adhere tightly to the wafer 1 and the frame 7.

[0058] Then, the heating roller 6 is heated to a predetermined temperature and placed at one end of the holding surface 2a of the chuck table 2. The heating roller 6 is then rotated, causing it to roll from one end to the other on the chuck table 2. This thermally presses the polyolefin sheet 9 onto the wafer 1 and the frame 7. At this time, when force is applied in the direction of pressing down on the polyolefin sheet 9 by the heating roller 6, thermal pressing is performed using pressure greater than atmospheric pressure. Furthermore, it is preferable to coat the surface of the heating roller 6 with fluoropolymer resin.

[0059] Alternatively, an iron-shaped pressing member with an internal heat source and a flat bottom plate can be used instead of the heating roller 6 to perform the hot pressing of the polyolefin sheet 9. In this case, the pressing member is heated to a specified temperature to become a hot plate, and the polyolefin sheet 9 held by the chuck table 2 is pressed from above using the pressing member.

[0060] Heating of polyolefin sheet 9 can also be achieved by other methods. Figure 6 This is a perspective view schematically illustrating yet another example of an integrated process. Figure 6 In the diagram, dashed lines represent components that can be seen through the polyolefin sheet 9, which is transparent or translucent to visible light. Figure 6 In the integrated process shown, an infrared lamp 8 disposed above the chuck worktable 2 is used to heat the polyolefin sheet 9. The infrared lamp 8 is capable of irradiating at least infrared light 8a of a wavelength that is absorbed by the material of the polyolefin sheet 9.

[0061] exist Figure 6 In the integrated process shown, the negative pressure of the attraction source 2b is first applied to the polyolefin sheet 9, causing the polyolefin sheet 9 to adhere tightly to the wafer 1 and the frame 7. Next, the infrared lamp 8 is activated to irradiate the polyolefin sheet 9 with infrared rays 8a, thereby heating the polyolefin sheet 9. Then, the polyolefin sheet 9 is hot-pressed onto the wafer 1 and the frame 7.

[0062] When the polyolefin sheet 9 is heated to a temperature near its melting point by any method, the polyolefin sheet 9 is hot-pressed onto the wafer 1 and the frame 7. After the polyolefin sheet 9 is hot-pressed, the switching unit 2c is activated to disconnect the porous component of the chuck stage 2 from the suction source 2b, thereby releasing the adsorption of the chuck stage 2.

[0063] Next, the polyolefin sheet 9 protruding from the outer periphery of the frame 7 is cut off and removed. Figure 7 (A) is a perspective view schematically showing the cutting of polyolefin sheet 9. Regarding the cutting, as... Figure 7 As shown in (A), a ring-shaped cutter 10 is used. The cutter 10 has a through hole and is able to rotate about a rotation axis passing through the through hole.

[0064] First, the annular cutter 10 is positioned above the frame 7. At this time, the rotation axis of the cutter 10 is aligned radially with the chuck table 2. Next, the cutter 10 is lowered, and the polyolefin sheet 9 is cut by clamping it between the frame 7 and the cutter 10. Thus, a cutting mark 9a is formed on the polyolefin sheet 9.

[0065] Furthermore, the cutter 10 is moved around the opening 7a of the frame 7, and around a predetermined area of ​​the polyolefin sheet 9 through the cutting mark 9a. Then, the polyolefin sheet 9 in the area outside the cutting mark 9a is removed in the manner that the remaining polyolefin sheet 9 remains in that area. Thus, unwanted portions of the polyolefin sheet 9, including the area protruding from the outer periphery of the frame 7, can be removed.

[0066] Furthermore, an ultrasonic cutter can be used in cutting the polyolefin sheet, and a vibration source that causes the aforementioned annular cutter 10 to vibrate at the frequency of the ultrasonic band can be connected to the cutter 10. Additionally, when cutting the polyolefin sheet 9, to facilitate cutting, the polyolefin sheet 9 can be cooled and hardened. As described above, a frame unit 11 is formed by integrating the wafer 1 and the frame 7 using the polyolefin sheet 9. Figure 7 (B) is a schematic perspective view showing the formed frame unit 11.

[0067] Furthermore, during hot pressing, the polyolefin sheet 9 is preferably heated to a temperature below its melting point. This is because when the heating temperature exceeds the melting point, the polyolefin sheet 9 may melt and fail to maintain its sheet shape. Additionally, the polyolefin sheet 9 is preferably heated to a temperature above its softening point. This is because if the heating temperature does not reach the softening point, hot pressing cannot be properly performed. In other words, the polyolefin sheet 9 is preferably heated to a temperature above its softening point and below its melting point.

[0068] In addition, there are cases where some polyolefin sheets 9 do not have a defined softening point. Therefore, when performing hot pressing, the polyolefin sheets 9 are preferably heated to a temperature at least 20°C lower than their melting point and below their melting point.

[0069] Furthermore, when the polyolefin sheet 9 is a polyethylene sheet, a heating temperature of 120°C to 140°C is preferred. When the polyolefin sheet 9 is a polypropylene sheet, a heating temperature of 160°C to 180°C is preferred. When the polyolefin sheet 9 is a polystyrene sheet, a heating temperature of 220°C to 240°C is preferred.

[0070] Here, heating temperature refers to the temperature of the polyolefin 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 polyolefin sheet 9, the temperature of the polyolefin sheet 9 sometimes does not reach the set output temperature. Therefore, in order to heat the polyolefin sheet 9 to the specified temperature, the output temperature of the heat source can be set higher than the melting point of the polyolefin 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] During laser processing of wafer 1, frame unit 11 is placed on the chuck stage, thereby holding wafer 1 on the chuck stage through polyolefin sheet 9. Next, the chuck stage is rotated to align the predetermined dividing line 3 of wafer 1 with the processing feed direction of laser processing apparatus 12. Furthermore, the relative position of the chuck stage and laser processing unit 14 is adjusted such that processing head 14a is positioned above the extension of the predetermined dividing line 3. Finally, the focusing point 14b of 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 of the laser beam 16 reaches the polyolefin sheet 9 below the wafer 1.

[0087] For example, if an adhesive tape is used instead of a polyolefin 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 fabrication method of this embodiment, a polyolefin 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 polyolefin 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 polyolefin substrate 9 radially outward. Then, a pick-up process is performed to pick up each device chip from the polyolefin substrate 9. In the extension of the polyolefin 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 polyolefin sheet 9 from below. The lifting mechanism 34 has a heating section 34a at its upper end, which houses a Peltier element, heating wire, and other heat sources. Additionally, a collet 36 (see reference) is located 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 polyolefin 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 polyolefin sheet 9 extends radially outward. Figure 10 (B) is a schematic cross-sectional view showing the extended polyolefin sheet 9.

[0097] As the polyolefin sheet 9 expands, a radially outward force is applied to the wafer 1, dividing the wafer 1 from the shield tunnel 3a to form individual device chips 1c. When the polyolefin sheet 9 is further expanded, the spacing between the individual device chips 1c supported by the polyolefin 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 polyolefin wafer 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 heating element 34a is activated to raise the temperature, and the heating element 34a contacts the area of ​​the polyolefin sheet 9 corresponding to the device chip 1c, heating that area. Next, the lifting mechanism 34 is activated to lift the device chip 1c from the polyolefin 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 polyolefin sheet 9. Each picked-up device chip 1c is then mounted on a specified wiring substrate or the like for use.

[0100] Furthermore, when this region of the polyolefin sheet 9 is heated using the heating element 34a, for example, the region is heated to a temperature near the melting point of the polyolefin sheet 9. Since the adhesive strength of the polyolefin sheet 9 decreases during the period when it is at a temperature near its melting point, the load applied to the device chip when peeling it from the polyolefin 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 polyolefin 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 polyolefin sheet 9 was described as a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet, but one aspect of the present invention is not limited to this. For example, other materials can be used for the polyolefin sheet, such as copolymers of propylene and ethylene, olefin elastomers, 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 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 polyolefin sheet placement process, the wafer is positioned in the opening of a frame with an opening for receiving the wafer, and a polyolefin sheet without a paste layer is placed on the back or front of the wafer and on the outer periphery of the frame, so that the polyolefin sheet is in direct contact with the wafer and the frame. In the integration process, after the polyolefin sheet assembly process, the polyolefin sheet without a paste layer is heated and pressure is applied. The wafer and the frame are integrated by means of the polyolefin sheet through hot pressing, thereby forming a frame unit. 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 picking process, the polyolefin sheet is heated in each region corresponding to each device chip, the device chip is lifted from the side of the polyolefin sheet, and the device chip is picked up from the polyolefin 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 polyolefin sheets protruding from the periphery of the frame are removed.

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

5. The wafer processing method according to claim 1, characterized in that, The polyolefin sheet can be any sheet of polyethylene, polypropylene, or polystyrene.

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

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

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