wafer fabrication methods

Abstract

A wafer processing method is provided to form device chips without compromising quality. This wafer processing method divides a wafer, in which multiple devices are formed in different areas of the front side divided by predetermined dicing lines, into individual device chips. The wafer processing method includes the following steps: a polyester sheet placement step, in which the wafer is positioned within an opening in a frame having an opening for receiving the wafer, and a polyester 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 polyester sheet is heated and the wafer and the frame are integrated by thermoforming using the polyester sheet; a dicing step, in which a laser beam of a wavelength transparent to the wafer is irradiated along the predetermined dicing lines to form a modified layer in the wafer, thereby dicing the wafer into individual device chips; and a pickup step, in which ultrasonic waves are applied to the polyester sheet to lift the device chip and pick it up.

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 equipment is used, for example, in wafer dicing. The laser processing equipment includes a chuck stage that holds the wafer with an adhesive tape and a laser processing unit that focuses a laser beam of wavelength that is transparent to the wafer into the interior of the wafer.

[0005] During wafer dicing, a frame unit is placed on a chuck stage, and the wafer is held on the chuck stage via an adhesive tape. Then, while the chuck stage and the laser processing unit are moved relative to each other in a direction parallel to the upper surface of the chuck stage, a laser beam is irradiated onto the wafer along each predetermined dicing line from the laser processing unit. When the laser beam is focused into the interior of the wafer, a modified layer is formed as the starting point for dicing (see Patent Document 1).

[0006] 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).

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

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

[0009] The adhesive tape, for example, comprises a substrate layer formed from a vinyl chloride sheet or the like and a paste layer disposed on the substrate layer. In a laser processing apparatus, in order to form a modified layer inside the wafer as a cleaving starting point, a laser beam is focused into the interior of the wafer; however, a portion of the laser beam leaks into the paste layer of the adhesive tape. Furthermore, due to the heat effect from 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.

[0010] 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

[0011] 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.

[0012] 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 polyester sheet placement step, in which the wafer is positioned within the opening of a frame having an opening for receiving the wafer, and a polyester sheet is placed on the back side or the front side of the wafer and on the outer periphery of the frame; an integration step, in which the polyester sheet is heated and the wafer and the frame are integrated by thermoforming using the polyester sheet; a slitting step, in which a focusing point of a laser beam with a wavelength transparent to the wafer is positioned inside the wafer, the laser beam is irradiated onto the wafer along the predetermined dividing line, a modified layer is formed in the wafer, and the wafer is divided into individual device chips; and a pickup step, in which ultrasonic waves are applied to the polyester sheet in each region corresponding to each device chip, the device chip is lifted from the polyester sheet side, and the device chip is picked up from the polyester sheet.

[0013] Preferably, the hot pressing is performed by infrared irradiation in this integrated process.

[0014] In addition, preferably, in this integrated process, after integration is carried out, the polyester sheets protruding from the outer periphery of the frame are removed.

[0015] In addition, it is preferable that the polyester sheet is expanded during the picking process to increase the spacing between the device chips.

[0016] In addition, the preferred polyester sheet is any sheet selected from polyethylene terephthalate sheet and polyethylene naphthalate sheet.

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

[0018] In addition, the wafer is preferably made of any material selected from Si, GaN, GaAs, and glass.

[0019] 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 polyester sheet without a paste layer is used to integrate the frame and the wafer. The integration process of integrating the frame and the wafer by means of the polyester sheet is achieved by thermoforming.

[0020] After the integration process, the wafer is irradiated with a laser beam of wavelength transparent to the wafer, forming a modified layer along a predetermined dividing line inside the wafer, thus dividing the wafer. Then, ultrasonic waves are applied to each region of the polyester sheet corresponding to each device chip, lifting the device chip from the polyester sheet side and picking it up. The picked-up device chips are then mounted on designated mounting objects. By applying ultrasonic waves to the polyester sheet during pickup, peeling off the polyester sheet becomes easier, thus reducing the load applied to the device chips.

[0021] When a modified layer is formed inside the wafer, light leakage from the laser beam reaches the polyester substrate. However, the polyester 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.

[0022] That is, according to one aspect of the present invention, a polyester sheet without a paste layer can be used to form the frame unit, 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.

[0023] 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

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

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

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

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

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

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

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

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

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

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

[0034] Label Explanation

[0035] 1: Wafer; 1a: Front side; 1b: Back side; 3: Pre-cut dividing line; 3a: Modified layer; 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: Ultrasonic transducer; 36: Collet. Detailed Implementation

[0036] 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.

[0037] 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.

[0038] 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 processing method of this embodiment, a modifier layer is formed inside wafer 1 along the predetermined dividing lines 3, and wafer 1 is divided starting from this modifier layer to form individual device chips.

[0039] When a modified layer is formed in wafer 1, a laser beam of a wavelength 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.

[0040] The wafer 1 is moved into the laser processing apparatus 12 (see reference) for laser processing in which a modified layer is formed in the wafer 1. Figure 8 Before that, the wafer 1, the polyester sheet, and the frame are integrated to form a frame unit. The wafer 1 is then moved into the laser processing apparatus 12 in the form of a frame unit for processing.

[0041] Furthermore, when the polyester sheet is expanded, the wafer 1 can be divided, and the individual device chips formed by dividing the wafer 1 are supported on the polyester sheet. Then, the polyester sheet is further expanded to increase the spacing between the device chips, and the device chips are picked up by a pickup device.

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

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

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

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

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

[0047] In the polyester sheet assembly process, the first step is as follows: Figure 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.

[0048] 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.

[0049] After placing the wafer 1 and the frame 7 on the holding surface 2a of the chuck stage 2, a polyester 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 3 This is a schematic three-dimensional diagram illustrating the assembly process of polyester sheets. For example... Figure 3 As shown, polyester sheets 9 are arranged on both the wafer 1 and the frame 7 in a manner that covers both.

[0050] Furthermore, in the polyester sheet installation process, a polyester 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 polyester sheet 9 in the subsequent integrated process, if the polyester 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 polyester sheet 9.

[0051] In the wafer 1 processing method of this embodiment, an integration process is then performed, in which the polyester sheet 9 is heated and the wafer 1 and the frame 7 are integrated by means of the polyester sheet 9 through hot pressing. Figure 4 This is a perspective view schematically illustrating an example of an integrated process. Figure 4 In the middle, the dashed lines indicate the parts that can be seen through the polyester sheet 9 which is transparent or translucent to visible light.

[0052] 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 polyester sheet 9. Then, atmospheric pressure is used to make the polyester sheet 9 adhere tightly to the wafer 1 and the frame 7.

[0053] Next, hot pressing is performed by simultaneously attracting the polyester sheet 9 through the attraction source 2b and heating the polyester sheet 9. The heating of the polyester 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.

[0054] 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 polyester sheet 9, hot air 4a is supplied to the polyester sheet 9 from the upper surface through the hot air gun 4. When the polyester sheet 9 is heated to the specified temperature, the polyester sheet 9 is hot-pressed onto the wafer 1 and the frame 7.

[0055] Alternatively, heating of the polyester sheet 9 can also be achieved 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 middle, the dashed lines indicate the parts that can be seen through the polyester sheet 9 which is transparent or translucent to visible light.

[0056] exist Figure 5 In 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 polyester sheet 9, and atmospheric pressure is used to make the polyester sheet 9 adhere tightly to the wafer 1 and the frame 7.

[0057] 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 heat-presses the polyester 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 polyester sheet 9 by the heating roller 6, heat 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.

[0058] 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 polyester sheet 9. In this case, the pressing member is heated to a specified temperature to become a hot plate, and the polyester sheet 9 held by the chuck table 2 is pressed from above using the pressing member.

[0059] Heating of the polyester sheet 9 can also be carried out 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 indicate components that can be seen through the polyester 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 polyester sheet 9. The infrared lamp 8 is capable of irradiating at least infrared light 8a of a wavelength that is absorbed by the polyester sheet 9.

[0060] exist Figure 6 In the integrated process shown, the negative pressure of the attraction source 2b is first applied to the polyester sheet 9, causing the polyester sheet 9 to adhere tightly to the wafer 1 and the frame 7. Next, the infrared lamp 8 is activated to irradiate the polyester sheet 9 with infrared rays 8a, thereby heating the polyester sheet 9. Thus, the polyester sheet 9 is hot-pressed onto the wafer 1 and the frame 7.

[0061] When the polyester sheet 9 is heated to a temperature near its melting point by any method, the polyester sheet 9 is hot-pressed onto the wafer 1 and the frame 7. After the polyester 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 suction of the chuck stage 2.

[0062] Next, the polyester 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 polyester 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.

[0063] 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 polyester sheet 9 is cut by clamping it between the frame 7 and the cutter 10. Thus, a cutting mark 9a is formed on the polyester sheet 9.

[0064] Furthermore, the cutter 10 is moved around the opening 7a of the frame 7, and around a predetermined area of ​​the polyester sheet 9 through the cutting mark 9a. Then, the polyester sheet 9 in the area outside the cutting mark 9a is removed in the manner that the remaining polyester sheet 9 remains in that area. Thus, unwanted portions of the polyester sheet 9, including the area protruding from the outer periphery of the frame 7, can be removed.

[0065] Furthermore, an ultrasonic cutter can be used in cutting the polyester 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 polyester sheet 9, it can be cooled and hardened to facilitate cutting. As described above, a frame unit 11 is formed by integrating the wafer 1 and the frame 7 using the polyester sheet 9. Figure 7 (B) is a schematic perspective view showing the formed frame unit 11.

[0066] Furthermore, during hot pressing, the polyester sheet 9 is preferably heated to a temperature below its melting point. This is because when the heating temperature exceeds the melting point, the polyester sheet 9 may melt and fail to maintain its sheet shape. Additionally, the polyester 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 polyester sheet 9 is preferably heated to a temperature above its softening point and below its melting point.

[0067] In addition, there are cases where some polyester sheets 9 do not have a definite softening point. Therefore, when performing hot pressing, the polyester sheets 9 are preferably heated to a temperature at least 20°C lower than their melting point and below their melting point.

[0068] Furthermore, when the polyester sheet 9 is a polyethylene terephthalate sheet, a heating temperature of 250°C to 270°C is preferred. Alternatively, when the polyester sheet 9 is a polyethylene naphthalate sheet, a heating temperature of 160°C to 180°C is preferred.

[0069] 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.

[0070] 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 form a modified layer along the predetermined dicing line 3 inside the wafer 1, thereby dicing the wafer 1. 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.

[0071] 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.

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

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

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

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

[0076] Wavelength: 1064nm

[0077] Repetition frequency: 50kHz

[0078] Average output: 1W

[0079] Feed rate: 200 mm / s

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

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

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

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

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

[0085] The pickup device 18 includes: a cylindrical drum 20 having a diameter larger than that of the wafer 1; and a frame holding unit 22 including a frame support 26. The frame support 26 of the frame holding unit 22 has an opening with a diameter larger than that of the drum 20, and is positioned at the same height as the upper end of the drum 20, surrounding the upper end of the drum 20 from the outer periphery.

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

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

[0088] Inside the drum 20 is a lifting mechanism 34 that lifts the device chip supported by the polyester sheet 9 from below. The lifting mechanism 34 has an ultrasonic transducer 34a at its upper end, which is made of piezoelectric ceramics or crystal transducers such as lead zirconate titanate (PZT), barium titanate, or lead titanate. Additionally, a collet 36 (see reference) is provided above the drum 20 to attract and hold the device chip. Figure 10 (B)). The lifting mechanism 34 and the collet 36 are movable in the horizontal direction along the upper surface of the frame support 26. In addition, the collet 36 is connected via a switching part 36b (see reference). Figure 10 (B) and with attraction source 36a (refer to) Figure 10 (B)) connection.

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

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

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

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

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

[0094] Then, the ultrasonic transducer 34a is activated to generate vibrations at the frequency of the ultrasonic band, and the ultrasonic transducer 34a is brought into contact with the area of ​​the polyester sheet 9 corresponding to the device chip 1c to impart ultrasonic waves to that area. Furthermore, 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. Thus, the device chip 1c is attracted and held by the collet 36, and picked up from the polyester sheet 9. Each picked-up device chip 1c is then mounted on a designated wiring substrate or the like for use.

[0095] Furthermore, when ultrasonic waves are applied to this region of the polyester sheet 9 via 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.

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

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

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

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

Claims

1. A 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 has the following steps: a polyester sheet provision step of positioning the wafer in an opening of a frame having an opening that receives the wafer, provision of a polyester sheet that does not have a paste layer on the back surface of the wafer or the front surface and the outer periphery of the frame in a manner that completely covers the entire wafer and frame, bringing the polyester sheet into direct contact with the back surface side of the wafer and the frame, and covering the entire holding surface of a chuck table on which the wafer and frame are placed with the polyester sheet; an integration step of, after the polyester sheet provision step, heating the polyester sheet while applying pressure to the polyester sheet, integrating the wafer and the frame by the polyester sheet by heat pressure bonding, thereby forming a frame unit; a division step of positioning a focal point of a laser beam of a wavelength that is transmissive to the wafer inside the wafer, irradiating the wafer with the laser beam along the division predetermined line, forming a modified layer in the wafer, and dividing the wafer into individual device chips; and a pickup step of imparting ultrasonic waves to the polyester sheet in each region of the polyester sheet corresponding to each device chip, lifting the device chip from the polyester sheet side, and picking up the device chip from the polyester sheet.

2. The wafer processing method according to claim 1, characterized in that, in the integration step, the heat 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 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 of Si, GaN, GaAs, and glass.

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