Wafer processing method

Abstract

To provide a wafer processing method that solves problems such as a protective sheet being peeled off from the outer periphery of a wafer and the outer periphery of the wafer being damaged by cutting means.SOLUTION: A wafer processing method in which a device area in which a plurality of devices are partitioned by dividing lines and an outer peripheral surplus area surrounding the device area are formed on the surface includes a sheet installation step of installing a protective sheet large enough to cover the entire surface of the wafer, a sheet cutting step of cutting the protective sheet protruding from the outer periphery of the wafer, and a wafer treatment step of processing the back side of the wafer, and in the sheet cutting step, a laser beam is irradiated onto the protective sheet in an area corresponding to the outer periphery of the wafer to cut the protective sheet protruding from the outer periphery of the wafer.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer on which a device region partitioned by a dicing line and an outer peripheral surplus region surrounding the device region are formed on the surface.

Background Art

[0002] A wafer on which a device region partitioned by a dicing line and an outer peripheral surplus region surrounding the device region are formed on the surface is ground on the back surface to form a desired thickness, and then processed on the dicing line by a dicing device or a laser processing device, and divided into individual device chips and used in electrical devices such as mobile phones and personal computers.

[0003] Also, a half groove having a depth corresponding to the finished thickness of the wafer is formed in the dicing line formed on the surface of the wafer, and then a protective sheet is disposed on the surface of the wafer and the back surface of the wafer is ground to expose the half groove on the back surface of the wafer, thereby dividing the wafer into individual device chips. A technique called pre-dicing has been proposed.

[0004] When grinding the back surface of the wafer, in order to prevent the surface of the wafer from being damaged while being held by the chuck table of the grinding device or the device chips from being scattered by pre-dicing, a protective sheet is disposed in advance to protect the surface of the wafer (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] The protective sheets used in the technologies described in Patent Documents 1 and 2 above are generally set to be slightly larger than the surface of the wafer and are arranged to cover the wafer. Therefore, after the protective sheet is placed on the surface of the wafer, the outer peripheral region of the protective sheet is cut along the outer circumference of the wafer using a cutting means such as a cutter. However, problems arise such as the protective sheet getting caught in the cutting blade of the cutting means and peeling off from the outer circumference of the wafer, or the cutting blade damaging the outer circumference of the wafer, so improvements are needed.

[0007] The present invention has been made in view of the above facts, and its main technical problem is to provide a wafer processing method that solves problems such as the protective sheet peeling off from the outer edge of the wafer or the outer edge of the wafer being damaged by a cutting means. [Means for solving the problem]

[0008] To solve the above-mentioned main technical problems, the present invention provides a wafer processing method in which a device region partitioned by division lines and an outer peripheral excess region surrounding the device region are formed on the surface of the wafer, comprising: a sheet placement step of placing a protective sheet large enough to cover the entire surface of the wafer; a sheet cutting step of cutting the protective sheet that extends beyond the outer peripheral of the wafer; and a wafer processing step of processing the back surface of the wafer. The sheet placement process involves placing a heat-pressed sheet that is pressed onto the surface of the wafer by heat, or an adhesive sheet with an adhesive layer formed in a corresponding area of ​​the excess outer circumference of the wafer, placing a flexible layer that absorbs the unevenness of the heat-pressed sheet or adhesive sheet, and further placing a flattening sheet to flatten the flexible layer to form the protective sheet. The sheet cutting process provides a wafer processing method that involves irradiating a protective sheet in a region corresponding to the outer edge of the wafer with a laser beam to cut off the protective sheet that extends beyond the outer edge of the wafer.

[0009] moreover The wafer processing step may be a step of grinding or polishing the back surface of the wafer. [Effects of the Invention]

[0010] The wafer processing method of the present invention is a wafer in which a device region is formed on the surface of which a plurality of devices are partitioned by division lines and an outer peripheral excess region surrounding the device region, and includes a sheet placement step of placing a protective sheet that is large enough to cover the entire surface of the wafer, a sheet cutting step of cutting the protective sheet that extends beyond the outer peripheral of the wafer, and a wafer processing step of processing the back surface of the wafer. The sheet placement process involves placing a heat-pressed sheet that is pressed onto the surface of the wafer by heat, or an adhesive sheet with an adhesive layer formed in a corresponding area of ​​the excess outer circumference of the wafer, placing a flexible layer that absorbs the unevenness of the heat-pressed sheet or adhesive sheet, and further placing a flattening sheet to flatten the flexible layer to form the protective sheet. This sheet cutting process involves irradiating a laser beam onto the protective sheet in the area corresponding to the outer edge of the wafer to cut off the protective sheet that extends beyond the outer edge of the wafer. This eliminates problems such as the protective sheet peeling off from the outer edge of the wafer or the outer edge of the wafer being scratched. [Brief explanation of the drawing]

[0011] [Figure 1] (a) A perspective view showing an embodiment of the sheet arrangement process, (b) A perspective view showing a manner of heat compression bonding in the sheet arrangement process, and (c) An enlarged cross-sectional view of the outer periphery of the wafer formed by the sheet arrangement process. [Figure 2] (a) A perspective view showing another embodiment of the sheet placement process; (b) A perspective view of a wafer on which adhesive sheets have been placed according to (a); (c) A partially enlarged cross-sectional view of the outer periphery of the wafer formed by the sheet placement process. [Figure 3] (a) A perspective view showing how a flexible layer is formed in yet another embodiment of the sheet arrangement process; (b) A perspective view showing how a planarization sheet is arranged on the flexible layer shown in (a); (c) A perspective view of a wafer on which a planarization sheet is arranged; (d) An enlarged cross-sectional view of a portion of the outer periphery of the wafer formed by (c). [Figure 4] This is an overall perspective view of the laser processing equipment. [Figure 5] (a) A block diagram showing the optical system of the laser beam irradiation means installed in the laser processing apparatus shown in Figure 4. (b) A perspective view showing how the sheet cutting process is carried out using the laser beam irradiation means shown in (a). [Figure 6](a) A block diagram showing the optical system of another embodiment of the laser beam irradiation means, and (b) A perspective view showing an embodiment in which the sheet cutting process is carried out using the laser beam irradiation means shown in (a). [Figure 7] This is a perspective view showing the removal of the outer perimeter of a protective sheet that has been cut in the sheet cutting process. [Figure 8] (a) A perspective view showing an embodiment of the wafer processing process, and (b) A perspective view showing the wafer after it has been divided into individual device chips by the wafer processing process. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments relating to a wafer processing method constructed according to the present invention will be described in detail with reference to the attached drawings.

[0013] Figure 1 shows a wafer 10 processed by the wafer processing method of this embodiment. The wafer 10 is a circular semiconductor (e.g., silicon (Si)) wafer with a device region 16a, which is divided into multiple devices 12 by division lines 14, and an outer peripheral excess region 16b surrounding the device region 16a, formed on its surface 10a. In Figure 1, for illustrative purposes, the boundary L separating the device region 16a and the outer peripheral excess region 16b is shown as a dashed line, but it is not actually formed on the surface 10a of the wafer 10.

[0014] In carrying out the wafer processing method of the present invention, the above-described wafer 10 is prepared, and a sheet placement step is performed in which a protective sheet large enough to cover the entire surface 10a of the wafer 10 is placed. The protective sheet is set to a size larger than the diameter of the wafer 10, for example, a circular sheet with a diameter of 310 mm. As the protective sheet, for example, a heat-sealable sheet T1 that can be pressed by heating can be used.

[0015] If the above wafer 10 is placed on the upper surface 2a of the work table 2 with the surface 10a facing upward and fixed with wax or the like as shown in Fig. 1(a), the thermocompression bonding sheet T1 is placed on the surface 10a of the wafer 10.

[0016] As the thermocompression bonding sheet T1, for example, it can be selected from a polyolefin-based sheet or a polyester-based sheet. As the polyolefin-based sheet, for example, it can be selected from any of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet, and as the polyester-based sheet, for example, it can be selected from any of a polyethylene terephthalate sheet and a polyethylene naphthalate sheet.

[0017] If the thermocompression bonding sheet T1 is placed on the surface 10a of the wafer 10, the cylindrical heating roller 3 shown in Fig. 1(b) is positioned above the wafer 10 on which the protective sheet T1 is placed. The heating roller 3 is configured to be rotatable in the direction indicated by the arrow R1 and movable in the direction indicated by the arrow R2. The heating roller 3 incorporates an electric heater and a temperature sensor (both not shown), and the temperature of the outer peripheral surface 3a of the heating roller 3 is adjusted by an appropriate control device. The outer peripheral surface 3a of the heating roller 3 is coated with a fluororesin.

[0018] As described above, if the heating roller 3 is positioned, the electric heater of the heating roller 3 is operated to adjust the temperature of the outer peripheral surface 3a to a temperature at which the thermocompression bonding sheet T1 softens and exhibits adhesive force. When a polyethylene (PE) sheet of a polyolefin-based sheet is selected as the thermocompression bonding sheet T1, the temperature during heating is adjusted within the range of 120 to 140°C. Note that the temperature during heating for thermocompression bonding the thermocompression bonding sheet T1 is appropriately adjusted according to the material of the sheet employed and is set to a temperature at which it softens by heating and exhibits adhesive force.

[0019] Next, the heating roller 3 is rotated in the direction indicated by arrow R1 and moved in the direction indicated by arrow R2 while pressing the heat-press sheet T1 downwards with the heating roller 3, so that the heat-press sheet T1 adheres closely to the surface 10a of the wafer 10 and is pressed against the surface 10a of the wafer 10. Since the outer surface 3a of the heating roller 3 is coated with fluororesin, even if adhesive force is generated on the heat-press sheet T1, the heat-press sheet T1 will not get caught in the heating roller 3. This completes the sheet placement process. Note that since the heat-press sheet T1 is larger than the wafer 10, as shown in Figure 1(c), the outer circumference T1a of the heat-press sheet T1 protrudes outward from the outer circumference 10c of the wafer 10.

[0020] The above reference example The sheet placement process is not limited to the embodiments described above. For example, instead of the thermocompression sheet T1 described above, an adhesive sheet T2 shown in Figure 2 may be used as a protective sheet to protect the surface 10a of the wafer 10. The illustrated adhesive sheet T2 is, for example, a polyolefin sheet, and an annular adhesive layer T2c is formed on the lower surface T2a side, which is the adhesive surface, in a region corresponding to the excess outer peripheral region 16b of the wafer 10, with an adhesive agent applied. No adhesive layer is formed on the lower surface T2a of the adhesive sheet T2 in the central region (inside the adhesive layer T2c) corresponding to the device region 16a of the wafer 10, and on the upper surface T2b of the adhesive sheet T2. As shown in Figure 2(b), the sheet placement process can also be realized by placing and attaching such an adhesive sheet T2 to the surface 10a of the wafer 10. Similar to the embodiment described above, the adhesive sheet T2 is formed with a diameter larger than the wafer 10, for example, 310 mm, and as shown in Figure 2(c), the outer periphery of the adhesive layer T2c of the adhesive sheet T2 extends outward from the outer periphery 10c of the wafer 10.

[0021] Furthermore, the sheet arrangement process of the present invention is A heat-sealable sheet is placed on the surface of the wafer by heat, or an adhesive sheet has an adhesive layer formed on it corresponding to the excess area on the outer edge of the wafer. A flexible layer is then placed to absorb the irregularities of the heat-sealable sheet or adhesive sheet, and a flattening sheet is further placed to flatten the flexible layer, thereby forming the protective sheet.As described above, when a thermocompression sheet T1 or an adhesive sheet T2 is placed on the surface 10a of the wafer 10, irregularities T1b may occur due to the irregularities of the surface 10a of the wafer 10, as illustrated in Figure 3(a) (Figure 3(a) shows an example where a thermocompression sheet T1 is placed as a protective sheet). Therefore, in the embodiment shown in Figure 3, after attaching the thermocompression sheet T1, a liquid resin 22 having viscosity, for example, is supplied to the upper surface of the thermocompression sheet T1 in order to form a flexible layer that absorbs the irregularities T1b shown. A specified amount of the liquid resin 22 is dripped from the nozzle 21 of the liquid resin supply means 20 shown in the figure. Once the liquid resin 22 has been dripped, a flattening sheet T3 is laid on the upper surface of the flexible layer in order to flatten the surface of the flexible layer, as shown in Figure 3(b). The material of the flattening sheet T3 is not particularly limited, but it is a transparent resin sheet that is harder and has a uniform thickness compared to the thermocompression sheet T1, for example, a polypropylene (PP) sheet. If the liquid resin 22 that forms the flexible layer is a resin that hardens with ultraviolet light, after the flattening sheet T3 is placed, the liquid resin 22 is irradiated with ultraviolet light through the flattening sheet T3 to harden it. As a result, as shown in Figures 3(c) and (d), a protective sheet consisting of three layers, the thermocompression sheet T1, the liquid resin 22 as a flexible layer, and the flattening sheet T3, is formed on the surface 10a of the wafer 10, and the sheet placement process is completed. In this way, the protective sheet including the flexible layer and the flattening sheet T3 is also such that, as shown in Figure 3(d), the outer periphery T1a of the thermocompression sheet T1, the liquid resin 22 laminated thereon, and the outer periphery region of the flattening sheet T3 protrude outward from the outer periphery 10c of the wafer 10.

[0022] In the above description, an example was given in which a heat-sensitive adhesive sheet T1, which is pressed by heating, is attached to the surface 10a of the wafer 10, and a flexible layer (liquid resin 22) and a planarizing sheet T3 are placed on top of it. However, the present invention is not limited to this, and instead of the heat-sensitive adhesive sheet T1, the above-mentioned adhesive sheet T2 may be placed, and then the liquid resin 22 as a flexible layer and the planarizing sheet T3 may be placed in the same manner to form a protective sheet. Also, in the above embodiment, an example was shown in which a liquid resin 22 that hardens with ultraviolet light is supplied as the flexible layer, but the invention is not limited to this as long as the resin can absorb the irregularities T1b, and for example, a liquid resin that hardens over time or with a decrease in temperature may be used.

[0023] As described above, by providing a planarizing sheet T3 via a flexible layer on a thermocompression sheet T1 or adhesive sheet T2 attached to the surface 10a of the wafer 10, even if irregularities occur when a soft sheet such as the thermocompression sheet T1 or adhesive sheet T2 is attached to the surface 10a of the wafer 10, the surface 10a of the wafer 10 can be stably supported, and the influence of these irregularities in the wafer processing process described later can be avoided.

[0024] Once the sheet placement process has been carried out as described above, the wafer 10 is subjected to the sheet cutting process and wafer processing process described below. In the processes described below, a thermocompression sheet T1 is selected as the protective sheet, and the wafer 10 (see Figure 1(b)) that has undergone the sheet placement process by thermocompression is processed.

[0025] Figure 4 shows a laser processing apparatus 30 suitable for performing a sheet cutting process. The laser processing apparatus 30 comprises a base 30a, a holding means 31 disposed on the base 30a for holding a workpiece, a moving means 36 for moving the holding means 31 in the X-axis direction and in the Y-axis direction perpendicular to the X-axis direction, a laser beam irradiation means 40, and an imaging means 5 for performing alignment.

[0026] As shown in Figure 4, the holding means 31 includes a rectangular X-axis movable plate 32 mounted on a base 30a so as to be movable in the X-axis direction, a rectangular Y-axis movable plate 33 mounted on the X-axis movable plate 32 so as to be movable in the Y-axis direction, and a holding table 34 disposed on the Y-axis movable plate 33 and configured to be rotatable by having a pulse motor inside. The upper surface 34a of the holding table 34 is made of a breathable material and is connected to a suction means (not shown).

[0027] The moving means 36 includes an X-axis moving means 37 that moves the holding table 34 in the X-axis direction, and a Y-axis moving means 38 that moves the holding table 34 in the Y-axis direction. The X-axis moving means 37 converts the rotational motion of the motor 37a into linear motion via a ball screw 37b and transmits it to the X-axis movable plate 32, causing the X-axis movable plate 32 to move in the X-axis direction along a pair of guide rails 30b, 30b arranged on the base 30a along the X-axis direction. The Y-axis moving means 38 converts the rotational motion of the motor 38a into linear motion via a ball screw 38b and transmits it to the Y-axis movable plate 33, causing the Y-axis movable plate 33 to move in the Y-axis direction along a pair of guide rails 35, 35 arranged on the X-axis movable plate 32 along the Y-axis direction.

[0028] The laser processing apparatus 30 includes a frame 39 consisting of a vertical wall portion 39a erected to the side of the X-axis moving means 37 and Y-axis moving means 38 on a base 30a, and a horizontal wall portion 39b extending horizontally from the upper end of the vertical wall portion 39a. The optical system and imaging means 5 that constitute the laser beam irradiation means 40 are housed inside the horizontal wall portion 39b of the frame 39.

[0029] Figure 5(a) shows a block diagram illustrating the schematic of the optical system of the laser beam irradiation means 40. The laser beam irradiation means 40 includes an oscillator 43 that oscillates a pulsed laser beam LB according to desired laser processing conditions, an X-axis galvanometer scanner 44 that oscillates the pulsed laser beam LB oscillated by the oscillator 43 in the X-axis direction, a Y-axis galvanometer scanner 45 that oscillates the pulsed laser beam LB in the Y-axis direction, and a light concentrator 41 including an fθ lens 42 that irradiates the pulsed laser beam LB, which has oscillated in the X-axis and Y-axis directions, to a desired position on the workpiece held in the holding table 34.

[0030] The X-axis galvanoscanner 44 and Y-axis galvanoscanner 45 are known configurations having mirrors (not shown) and angle adjustment actuators for adjusting the reflection angle of the mirrors. The fθ lens 42 is configured to the dimensions corresponding to the wafer 10 and, by controlling the X-axis galvanoscanner 44 and Y-axis galvanoscanner 45, irradiates the pulsed laser beam LB, which is oscillated in the X-axis and Y-axis directions, perpendicular to a desired position on the holding surface 34a of the holding table 34. The X-axis galvanoscanner 44 and Y-axis galvanoscanner 45 are controlled by control means 46.

[0031] The control means described above is composed of a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) for storing the control program and the like, a read-write random access memory (RAM) for temporarily storing detected values, calculation results, etc., and an input interface and an output interface (details are not shown in the illustration). In addition to the laser beam irradiation means 40 described above, the control means is connected to an imaging means 5, a display means 6, an X-axis moving means 37, a Y-axis moving means 38, etc., and each operating part is controlled.

[0032] The laser processing apparatus 30 of this embodiment has a configuration that is generally as described above, and the sheet cutting process performed using this laser processing apparatus 30 will be described below.

[0033] When performing the sheet cutting process, the wafer 10 is placed on the upper surface 34a of the holding table 34 with the back surface 10b facing upwards and the heat-sealing sheet T1 facing downwards, and the suction means is activated to generate negative pressure on the upper surface 34a to hold it in place. Next, the moving means 36 is activated to position the wafer 10 together with the holding table 34 below the imaging means 5 and take an image to detect the positions of the wafer 10 and the heat-sealing sheet T1, and store this information in the control means.

[0034] Next, the moving means 36 is activated to position the wafer 10 below the concentrator 41 of the laser beam irradiation means 40. Based on the shape information of the wafer 10 and the thermocompression sheet T1 detected by the imaging means 5, the oscillator 43, X-axis galvanometer scanner 44, and Y-axis galvanometer scanner 45 of the laser beam irradiation means 40 are activated to position the focal point of the laser beam LB irradiated from the concentrator 41 onto the thermocompression sheet T1, as shown in Figure 5(b). At the same time, the laser beam LB with a wavelength that is absorbed by the thermocompression sheet T1 is irradiated in the annular region on the thermocompression sheet T1 corresponding to the outer circumference 10c of the wafer 10 while moving in the direction indicated by arrow R3, thereby cutting the outer circumference T1a of the thermocompression sheet T1 that extends beyond the outer circumference 10c of the wafer 10 in an annular shape.

[0035] The laser beam LB emitted from the oscillator 43 of the laser beam irradiation means 40 is set to the following laser processing conditions, for example. Wavelength: 355nm Repetition frequency: 10kHz Average output: 3W Spot diameter: 10 μm Machining feed rate: 100 mm / s

[0036] In the above-described embodiment, an example was shown in which a laser beam irradiation means 40 equipped with an fθ lens 42 is used to perform the sheet cutting process, but the present invention is not limited thereto. For example, instead of the above-described laser beam irradiation means 40, a laser beam irradiation means 40' as shown in Figure 6(a) may be provided. The laser beam irradiation means 40' is equipped with an oscillator 43' that has the same function as the oscillator 43 equipped in the above-described laser beam irradiation means 40, and the laser beam LB irradiated from the oscillator 43' is reflected by a reflective mirror 47 that converts the optical path and guided to a concentrator 41' equipped with a concentrating lens 42', which can then irradiate the holding table 34. Based on the information regarding the outer circumference 10c of the wafer 10 and the shape of the thermocompression sheet T1 detected by the imaging means 5, the X-axis moving means 37 and Y-axis moving means 38 of the moving means 36 are activated to position the concentrator 41' in an annular region of the thermocompression sheet T1 corresponding to the outer circumference 10c of the wafer 10, as shown in Figure 6(b). Then, while positioning the focal point of the laser beam LB irradiated from the laser beam irradiation means 40' onto the thermocompression sheet T1 and irradiating it, the holding table 34 is rotated in the direction indicated by the arrow R4 by the rotational drive means shown in the figure, thereby cutting the outer circumference T1a of the thermocompression sheet T1 that extends outward from the outer circumference 10c of the wafer 10, and the sheet cutting process is completed.

[0037] In the above-described embodiment, when performing the sheet cutting process, the wafer 10 is placed on the holding table 34 with its back surface 10b facing upwards and the thermocompression sheet T1 facing downwards, and then held in place by suction while laser processing is performed. However, the present invention is not limited to this. For example, the wafer 10 may be placed on the holding table 34 with its back surface 10b facing downwards and the thermocompression sheet T1 facing upwards, and then held in place by suction. A laser beam LB may then be irradiated from the thermocompression sheet T1 side onto the thermocompression sheet T1 in the area corresponding to the outer circumference 10c of the wafer 10 to cut the outer circumference T1a of the thermocompression sheet T1.

[0038] By performing the sheet cutting process described above, the outer periphery T1a of the heat-seal sheet T1 is cut, and as shown in Figure 7, the outer periphery T1a can be easily removed by pulling it up in the direction of arrow R5, and the heat-seal sheet T1 is processed into a shape that conforms to the outer periphery 10c of the wafer 10.

[0039] The sheet cutting process described above explains an example where a heat-sealable sheet T1 was selected as the protective sheet. 、 This is not limited to this. For example, if an adhesive sheet T2 is selected as the protective sheet, even if a flexible layer (liquid resin 22) that absorbs the unevenness of the heat-sealable sheet T1 or adhesive sheet T2 is provided as the protective sheet, and a flattening sheet T3 is provided to flatten the flexible layer, the sheet cutting process can be carried out using the same procedure as described above.

[0040] As described above, once the sheet cutting process is performed, a wafer processing process is carried out to process the back surface 10b of the wafer 10. When carrying out the wafer processing process, the wafer 10 is transported to a grinding device 50 (only a part is shown) as shown in Figure 8(a). As shown in Figure 8(a), the grinding device 50 comprises a chuck table 51 and a grinding means 52. The chuck table 51 is equipped with a rotational drive means (not shown), its upper surface is made of a breathable material, and it is connected to a suction means (not shown). The grinding means 52 comprises a rotary spindle 52a rotated by a rotational drive mechanism (not shown), a wheel mount 52b attached to the lower end of the rotary spindle 52a, and a grinding wheel 52c attached to the wheel mount 52b, on which a plurality of grinding wheels 52d are arranged in an annular pattern on its lower surface.

[0041] Once the wafer 10 is transported to the grinding device 50, the wafer 10 is placed on the chuck table 51 with its back surface 10b facing upwards and held in place by suction. Next, the rotating spindle 52a of the grinding means 52 is rotated at, for example, 6000 rpm in the direction indicated by arrow R6 in Figure 8(a), while the chuck table 51 is rotated at, for example, 300 rpm in the direction indicated by arrow R7. Then, grinding water is supplied onto the back surface 10b of the wafer 10 by a grinding water supply means (not shown), and the grinding wheel 52d is brought into contact with the back surface 10b of the wafer 10. The grinding wheel 52c is then fed downwards in the direction indicated by arrow R8 at, for example, a grinding feed rate of 1 μm / second. At this time, the amount of grinding of the wafer 10 can be measured using a contact-type measuring gauge (not shown) as the grinding progresses, and the wafer 10 is ground until the finished thickness is reached. Then, once the wafer 10 has reached a predetermined finished thickness, the grinding device 50 is stopped, completing the wafer processing step of grinding the back surface 10b of the wafer 10, and thus completing the wafer processing method in this embodiment.

[0042] Furthermore, if, before carrying out the sheet arrangement step in the wafer processing method described above, the wafer 10 is transported to a cutting device (not shown) and half grooves 100 with a depth corresponding to the finished thickness of the wafer 10 are formed on the division line 14 formed on the surface 10a of the wafer 10, then by grinding the back surface 10b of the wafer 10 in the wafer processing step described above, the half grooves 100 are exposed on the back surface 10b of the wafer 10, as shown in Figure 8(b), and the wafer 10 can be divided into individual device chips 12'.

[0043] In the embodiments described above, an embodiment was described in which the wafer 10 is transported to a grinding device 50 in the wafer processing step and the back surface 10b of the wafer 10 is ground. However, the present invention is not limited thereto, and the wafer may be transported to a polishing device (not shown) and the back surface 10b of the wafer 10 is polished.

[0044] According to the wafer processing method of this embodiment, in the sheet cutting step, a laser beam LB is irradiated onto the protective sheet in the area corresponding to the outer periphery 10c of the wafer 10 to cut the protective sheet that extends beyond the outer periphery 10c of the wafer 10. This eliminates the problems of the protective sheet peeling off from the outer periphery 10c of the wafer 10 or the outer periphery 10c of the wafer being damaged. [Explanation of Symbols]

[0045] 2: Work table 2a:Top surface 3: Heating roller 3a: Outer surface 5: Imaging means 6:Display means 10: Wafer 10a: surface 10b: Back side 10c: outer circumference 12: Devices 12': Device chip 14: Planned division line 16a: Device area 16b: Peripheral surplus region 20: Liquid resin supply means 21: Nozzle 22: Liquid resin (flexible layer) 30: Laser processing equipment 30a: Base 31: Holding means 32:X-axis movable plate 33: Y-axis movable plate 34: Holding Table 36: Means of transportation 37:X-axis movement means 38: Y-axis movement means 39: Frame 40: Laser beam irradiation means 41: Light concentrator 42: fθ lens 43: Oscillator 44: X-axis galvanometer scanner 45: Y-axis galvanometer scanner 40': Laser beam irradiation means 41': Light concentrator 42': Focusing lens 43': Oscillator 47: Reflective mirror 50: Grinding equipment 51: Chuck Table 52: Grinding methods 52a: Rotating spindle 52c: Grinding Wheel 52d: Grinding wheel T1: Heat-pressed sheet T1a: Outer perimeter T1b: Unevenness T2: Adhesive sheet T2a: Bottom surface T2b:Top surface T2c:adhesive layer T3: Flattening Sheet

Claims

1. A method for processing a wafer in which multiple devices are formed on its surface, comprising a device region demarcated by division lines and an outer peripheral surplus region surrounding the device region, A sheet placement process involves placing a protective sheet large enough to cover the entire surface of the wafer, A sheet cutting process that cuts off the protective sheet that extends beyond the outer edge of the wafer, A wafer processing process that processes the back surface of the wafer, Includes, The sheet placement process involves placing a heat-pressed sheet that is pressed onto the surface of the wafer by heat, or an adhesive sheet with an adhesive layer formed in a corresponding area of ​​the excess outer circumference of the wafer, placing a flexible layer that absorbs the unevenness of the heat-pressed sheet or adhesive sheet, and further placing a flattening sheet to flatten the flexible layer to form the protective sheet. The sheet cutting process is a wafer processing method that involves irradiating a protective sheet in a region corresponding to the outer edge of the wafer with a laser beam to cut off the protective sheet that extends beyond the outer edge of the wafer.

2. The wafer processing step is a step of performing a process of grinding or polishing the back surface of the wafer, as described in Claim 1.

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