Wafer processing method and refrigeration table

Abstract

The present invention provides a wafer processing method that prevents foreign matter from adhering to or scratching the back surface corresponding to the device area, and allows the protective tape to be peeled off from the wafer surface without damaging the outer edge of the wafer. [Solution] A method for processing a wafer 2 having a device region 8 partitioned by division lines 6 and an outer peripheral excess region 10 surrounding the device region 8 formed on its surface 2a, wherein a protective tape 40 is attached to the surface 2a, the wafer 2 is held on a chuck table with the protective tape 40 facing it, the back surface 2b of the wafer 2 corresponding to the device region 8 is ground to thin it, and a ring-shaped reinforcing portion 14 is formed in the region corresponding to the outer peripheral excess region 10, the wafer 2 is cleaned, and the protective tape 40 is peeled off from the surface 2a. When peeling off the protective tape 40, a freezing table 16 is used that supports only the ring-shaped reinforcing portion 14 and does not come into contact with the back surface 2b corresponding to the device region 8.

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer and a freezing table.

Background Art

[0002] For a wafer having a device region partitioned by a division planned line for a plurality of devices such as ICs and LSIs and an outer peripheral surplus region surrounding the device region formed on the surface, after the back surface is ground and thinned, it is divided into individual device chips by a dicing device, a laser processing device, etc., and the divided device chips are used in electric devices such as mobile phones and personal computers.

[0003] Since it becomes difficult to convey the wafer to the next process when the back surface of the wafer is ground and thinned, a protective tape is attached to the surface of the wafer, and then, after the protective tape is faced to the chuck table to hold the wafer, the applicant has proposed a technique of grinding the back surface corresponding to the device region to form a ring-shaped reinforcing portion in the region corresponding to the outer peripheral surplus region (see, for example, Patent Document 1). Then, in the next process, processing such as formation of an insulating film, wiring, and stacking of chips is performed on the back surface corresponding to the device region.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] If foreign matter adheres to or scratches the back surface corresponding to the device area, it can cause problems in subsequent processing steps. Therefore, in some cases, the outer edge of the wafer is supported by three or more claws to prevent foreign matter from adhering to or scratching the back surface corresponding to the device area, and protective tape is peeled off the wafer surface. However, this presents problems such as the claws hindering the peeling of the protective tape and scratching the outer edge of the wafer.

[0006] The object of the present invention is to provide a wafer processing method and a freezing table that prevent foreign matter from adhering to or scratching the back surface corresponding to the device area, and that allow the protective tape to be peeled off from the surface of the wafer without scratching the outer edge of the wafer. [Means for solving the problem]

[0007] According to the present invention, the following wafer processing method is provided that solves the above problems. That is, A wafer processing method in which a device region partitioned by a division line and an outer peripheral surplus region surrounding the device region are formed on the surface of the wafer, A protective tape application process in which protective tape is applied to the surface of the wafer, A holding step in which the protective tape is placed facing the chuck table to hold the wafer, A grinding step is performed to thin the back surface of the wafer held on the chuck table that corresponds to the device area, and to form a ring-shaped reinforcing portion in the area corresponding to the excess outer peripheral area. A cleaning process for cleaning wafers, The process includes a peeling step of peeling the protective tape from the surface of the wafer, A wafer processing method is provided, in which, in the peeling step, the protective tape is peeled off from the surface of the wafer using a freezing table that supports only the ring-shaped reinforcing portion formed on the back surface of the wafer and does not come into contact with the back surface corresponding to the device area.

[0008] Furthermore, the present invention provides the following freezing table that solves the above problems. That is, "The above is a freezer table, A table body having a support surface that supports a ring-shaped reinforcing portion formed on the back surface of the wafer, A freezing table is provided, which includes a cooling means disposed on the opposite side of the support surface.

[0009] Preferably, the table body has two or more support surfaces corresponding to the diameter of the wafer, the support surfaces are treated with a hydrophilic coating, and the surfaces other than the support surfaces are treated with a water-repellent coating. It is desirable that the table body is made of a material having the same coefficient of thermal expansion as the wafer. It is preferable that the table body has an atmospheric vent that opens the space enclosed by the back surface of the wafer and the table body to the atmosphere. [Effects of the Invention]

[0010] The wafer processing method of the present invention is A wafer processing method in which multiple devices are formed on the surface, comprising a device region demarcated by division lines and an outer peripheral surplus region surrounding the device region, A protective tape application process in which protective tape is applied to the surface of the wafer, A holding step in which the protective tape is placed facing the chuck table to hold the wafer, A grinding step is performed to thin the back surface of the wafer held on the chuck table that corresponds to the device area, and to form a ring-shaped reinforcing portion in the area corresponding to the excess outer peripheral area. A cleaning process for cleaning wafers, The process includes a peeling step of peeling the protective tape from the surface of the wafer, In this peeling step, the protective tape is peeled from the surface of the wafer using a refrigeration table that supports only the ring-shaped reinforcing portion formed on the back surface of the wafer and does not contact the back surface corresponding to the device region. Therefore, foreign matter does not adhere to or damage the back surface corresponding to the device region, and the protective tape can be peeled from the surface of the wafer without damaging the outer periphery of the wafer.

[0011] Further, the refrigeration table of the present invention includes a table body having a support surface that supports the ring-shaped reinforcing portion formed on the back surface of the wafer, and a cooling means disposed on the opposite side of the support surface. Therefore, foreign matter does not adhere to or damage the back surface corresponding to the device region, and the protective tape can be peeled from the surface of the wafer without damaging the outer periphery of the wafer.

Brief Description of the Drawings

[0012] [Figure 1] (a) Perspective view of the front surface side of the wafer, (b) Perspective view of the back surface side of the wafer shown in (a). [Figure 2] Perspective view of the refrigeration table according to the present invention. [Figure 3] Schematic cross-sectional view of the refrigeration table shown in FIG. 1. [Figure 4] (a) Schematic diagram showing the protective tape sticking step, (b) Perspective view of the wafer with the protective tape stuck on the surface. [Figure 5] Schematic diagram showing the holding step. [Figure 6] Schematic diagram showing the grinding step. [Figure 7] Schematic diagram showing the cleaning step. [Figure 8] Schematic diagram showing a state in which the wafer after cleaning is supported on the refrigeration table shown in FIG. 2. [Figure 9] (a) Schematic diagram showing the peeling step, (b) Schematic diagram showing a state in which the protective tape is peeled from the surface of the wafer.

Mode for Carrying Out the Invention

[0013] Hereinafter, a preferred embodiment of a wafer processing method and a freezing table according to the present invention will be described with reference to the drawings.

[0014] (Wafer 2) Figs. 1(a) and 1(b) show a wafer 2 supported by the freezing table of this embodiment. The wafer 2 can be formed from an appropriate semiconductor material such as silicon. The wafer 2 is disc-shaped, and the diameter of the wafer 2 is, for example, about 300 mm. As shown in Fig. 1(a), on the surface 2a of the wafer 2, a plurality of devices 4 such as ICs and LSIs are formed in a device region 8 partitioned by grid-like division planned lines 6, and an outer peripheral surplus region 10 surrounding the device region 8. In Fig. 1(a), for the sake of convenience, the ring-shaped boundary 12 between the device region 8 and the outer peripheral surplus region 10 is shown by a two-dot chain line, but actually, there is no line indicating the boundary 12. As shown in Fig. 1(b), on the back surface 2b side of the wafer 2, a ring-shaped reinforcing portion 14 is formed in a convex shape in a region corresponding to the outer peripheral surplus region 10, and the thickness of the outer peripheral surplus region 10 (for example, about 700 μm) is larger than the thickness of the device region 8 (for example, about 30 μm). The width (radial dimension) of the outer peripheral surplus region 10 is, for example, about 2 mm to 3 mm.

[0015] (Freezing table 16) Figs. 2 and 3 show the freezing table 16 that supports the above-mentioned wafer 2. The freezing table 16 includes a table body 18 and a cooling means 20 (see Fig. 3). The freezing table 16 supplies water (for example, pure water) between the table body 18 and the reinforcing portion 14 of the wafer 2, and freezes the supplied water by the cooling means 20, thereby freezing and fixing the reinforcing portion 14 to the table body 18.

[0016] (Table body 18 of the freezing table 16) The upper surface of the table body 18 is provided with a ring-shaped support surface 22 that supports the ring-shaped reinforcing portion 14 formed on the back surface 2b of the wafer 2. The diameter of the ring-shaped support surface 22 is approximately the same as that of the ring-shaped reinforcing portion 14, but the width (radial dimension) of the support surface 22 is greater than or equal to the width (radial dimension) of the excess outer peripheral region 10 of the wafer 2, for example, about 4 mm to 5 mm. Furthermore, in the table body 18, when the reinforcing portion 14 of the wafer 2 is supported by the support surface 22, the upper surface of the table body 18 does not come into contact with the back surface 2b corresponding to the device region 8.

[0017] The table body 18 may have two or more support surfaces 22 corresponding to the diameter of the wafer 2. As shown in Figure 2, the table body 18 of this embodiment is provided with two support surfaces 22a and 22b of different sizes. For example, the smaller support surface 22a (hereinafter referred to as "first support surface 22a") supports the reinforcing portion 14 of a wafer 2 with a diameter of 200 mm, and the larger support surface 22b (hereinafter referred to as "second support surface 22b") supports the reinforcing portion 14 of a wafer 2 with a diameter of 300 mm.

[0018] The ring-shaped support surface 22 of the table body 18 is provided with multiple (four in this embodiment) water supply holes 24 (see Figure 2) spaced apart in the circumferential direction. The water supply holes 24 of the first support surface 22a are connected to a water source 28 via a first flow path 26a, as shown in Figure 3. A first on-off valve 30a is provided in the first flow path 26a. When the first on-off valve 30a is opened, water from the water source 28 is supplied to the water supply holes 24 of the first support surface 22a via the first flow path 26a. The water supply holes 24 of the second support surface 22b are connected to a water source 28 via a second flow path 26b. A second on-off valve 30b is provided in the second flow path 26b. When the second on-off valve 30b is opened, water from the water source 28 is supplied to the water supply holes 24 of the second support surface 22b via the second flow path 26b.

[0019] Preferably, the support surface 22 of the table body 18 is treated with a hydrophilic coating, and the upper surface of the table body 18 other than the support surface 22 is treated with a water-repellent coating. This allows water supplied from the water supply hole 24 to be efficiently supplied along the support surface 22.

[0020] The support surface 22 of the table body 18 may be recessed by approximately 100 μm to 150 μm compared to the other surfaces of the upper surface of the table body 18, as shown in an enlarged view in Figure 3. This allows water supplied from the water supply hole 24 to be efficiently supplied along the support surface 22. The amount of recess in the support surface 22 is smaller than the difference between the thickness of the excess outer region 10 of the wafer 2 and the thickness of the device region 8. In other words, even if the support surface 22 is recessed, when the ring-shaped reinforcing portion 14 is supported by the support surface 22, the upper surface of the table body 18 does not come into contact with the back surface 2b corresponding to the device region 8.

[0021] It is preferable that the table body 18 is made of a material having the same coefficient of thermal expansion as the wafer 2. When the coefficient of thermal expansion of the table body 18 and the wafer 2 are the same, when the water supplied between the support surface 22 of the table body 18 and the reinforcing portion 14 of the wafer 2 is frozen, the table body 18 and the wafer 2 will contract at the same rate, thereby suppressing the generation of stress on the wafer 2 and preventing damage to the wafer 2.

[0022] Preferably, the table body 18 has an atmospheric vent 32 that opens the space enclosed by the back surface 2b of the wafer 2 and the table body 18 to the atmosphere. In this embodiment, as shown in Figures 2 and 3, the atmospheric vent 32 is formed in the center of the table body 18. When water supplied between the support surface 22 and the reinforcing part 14 is frozen, the temperature of the space enclosed by the back surface 2b of the wafer 2 and the table body 18 decreases. However, if an atmospheric vent 32 is formed, a pressure drop in the space enclosed by the back surface 2b of the wafer 2 and the table body 18 (pressure drop due to temperature drop) is prevented. Therefore, external forces caused by the pressure difference between the front surface 2a and the back surface 2b of the wafer 2 do not act on the wafer 2, and damage to the wafer 2 is prevented.

[0023] (Cooling means 20 for the freezing table 16) The cooling means 20 freezes the water supplied between the support surface 22 and the reinforcing part 14. As shown in Figure 3, the cooling means 20 of this embodiment includes a Peltier element 34 arranged in a ring shape on the opposite side of the support surface 22 of the table body 18, a power supply 36 connected to the Peltier element 34, and a switch 38 that controls the supply and interruption of current to the Peltier element 34 and controls the direction of the current supplied to the Peltier element 34. The cooling means 20 cools and freezes the water supplied between the support surface 22 and the reinforcing part 14 by supplying current to the Peltier element 34 in a predetermined direction. The cooling means 20 also heats and thaws the ice between the support surface 22 and the reinforcing part 14 by supplying current to the Peltier element 34 in the opposite direction to the predetermined direction.

[0024] In this embodiment, the first cooling means 20a is disposed on the opposite side of the first support surface 22a, and the second cooling means 20b is disposed on the opposite side of the second support surface 22b. However, the first and second cooling means 20a and 20b may both have the configuration described above. The Peltier elements 34 of the first and second cooling means 20a and 20b are formed in a shape that does not obstruct the first and second flow paths 26a and 26b.

[0025] (Wafer processing method) Next, embodiments of the wafer processing method according to the present invention will be described with reference to Figures 4 to 9.

[0026] (Protective tape application process) In this embodiment, first, a protective tape application process is performed in which a protective tape 40 is attached to the surface 2a of the wafer 2', as shown in Figures 4(a) and 4(b). The protective tape 40 is circular, and the diameter of the protective tape 40 is approximately the same as the diameter of the wafer 2. The protective tape 40 may be an adhesive tape or a thermocompression sheet. A thermocompression sheet is a sheet of thermoplastic synthetic resin (for example, a polyolefin resin), which softens or melts and exhibits adhesive force when heated to a temperature near its melting point. In the wafer 2' shown in Figures 4(a) and 4(b), unlike the wafer 2 shown in Figures 1(a) and 1(b), the ring-shaped reinforcing portion 14 has not yet been formed, and the thickness of the device region 8 and the thickness of the outer peripheral excess region 10 are the same.

[0027] (holding process) After the protective tape application process is performed, a holding process is carried out in which the protective tape 40 is brought facing the chuck table to hold the wafer 2'.

[0028] In the holding process, for example, the wafer 2' can be held on the chuck table 42 shown in Figure 5. A circular suction chuck 44 is positioned at the upper end of the chuck table 42. The suction chuck 44 is made of a porous material such as porous ceramics and is connected to a suction means (not shown). The chuck table 42 is also configured to rotate freely about its axis in the vertical direction.

[0029] In the holding process, the protective tape 40 is placed facing downwards, with the protective tape 40 facing the upper surface of the chuck table 42, and the wafer 2' is placed on the chuck table 42. Then, a suction force is generated on the upper surface of the suction chuck 44 using a suction means, and the wafer 2' is held in place by suction on the chuck table 42.

[0030] (Grinding process) After the holding process is performed, a grinding process is carried out to thin the back surface 2b of the wafer 2' held on the chuck table 42, which corresponds to the device area 8, and to form a ring-shaped reinforcing portion 14 in the area corresponding to the excess outer peripheral area 10.

[0031] The grinding process can be carried out using, for example, the grinding apparatus 46 shown in Figure 6. The grinding apparatus 46 comprises a spindle housing 48, a spindle 50 rotatably supported in the spindle housing 48 about an axis extending vertically, a motor (not shown) for rotating the spindle 50, and a disc-shaped wheel mount 52 fixed to the lower end of the spindle 50. An annular grinding wheel 56 is fastened to the lower surface of the wheel mount 52 by bolts 54. Multiple grinding wheels 58 are fixed to the outer circumference of the lower surface of the grinding wheel 56, arranged in an annular pattern at intervals in the circumferential direction. The diameter of the grinding wheels 58 is approximately the same as the radius of the wafer 2'.

[0032] In the grinding process, first, the positional relationship between the chuck table 42, which holds the wafer 2' by suction, and the grinding device 46 is adjusted. Specifically, the positional relationship between the chuck table 42 and the grinding device 46 is adjusted so that the grinding wheel 58 is positioned radially inward from the area corresponding to the outer peripheral excess area 10 and passes through the center of the wafer 2'. Next, the spindle 50 is rotated at a predetermined rotational speed (for example, 6000 rpm) in the direction indicated by arrow R1. Also, the chuck table 42 is rotated at a predetermined rotational speed (for example, 300 rpm) in the direction indicated by arrow R2. Next, the spindle 50 is lowered to bring the grinding wheel 58 into contact with the back surface 2b of the wafer 2', and grinding water is supplied to the portion of the back surface 2b of the wafer 2' into contact with the grinding wheel 58. Then, the spindle 50 is lowered at a predetermined grinding feed rate (for example, 1.0 μm / s). This allows the back surface 2b corresponding to the device region 8 to be ground down and thinned, and a ring-shaped reinforcing portion 14 to be formed in the region corresponding to the excess outer peripheral region 10, resulting in the wafer 2 shown in Figures 1(a) and 1(b).

[0033] (Washing process) After the grinding process, a cleaning process is performed to clean the wafer 2. In the cleaning process, cleaning water W (for example, pure water) is supplied to the back surface 2b of the wafer 2, where the ring-shaped reinforcement portion 14 is formed, to remove grinding debris and other contaminants from the back surface 2b (see Figure 7). Although not shown, it is preferable to use a spinner cleaning device to spinner clean the back surface 2b of the wafer 2 during the cleaning process. After removing grinding debris and other contaminants from the back surface 2b, air is blown onto the back surface 2b to dry it.

[0034] (Peeling process) After the cleaning process is performed, a peeling process is carried out to remove the protective tape 40 from the surface 2a of wafer 2.

[0035] In the peeling process, first, the wafer 2 is placed on the table body 18 of the freezing table 16. At this time, as shown in Figure 8, the protective tape 40 attached to the surface 2a of the wafer 2 is facing upwards. Also, the reinforcing portion 14 of the wafer 2 is aligned with the support surface 22 (second support surface 22b in this embodiment) of the table body 18. At this time, the reinforcing portion 14 of the wafer 2 is supported by the second support surface 22b of the table body 18, but the back surface 2b corresponding to the device area 8 does not come into contact with the upper surface of the table body 18.

[0036] When a wafer 2 is placed on the table body 18 of the freezing table 16, the reinforcing portion 14 of the wafer 2 is fixed to the second support surface 22b of the table body 18. At this time, the second on-off valve 30b is opened slightly, and water from the water source 28 is slowly supplied to the water supply hole 24 of the second support surface 22b via the second flow path 26b. As a result, water flows between the second support surface 22b and the reinforcing portion 14 by capillary action. In this way, water is supplied evenly between the second support surface 22b and the reinforcing portion 14. Next, an electric current is supplied in a predetermined direction to the Peltier element 34 of the second cooling means 20b, and the water supplied between the second support surface 22b and the reinforcing portion 14 is cooled and frozen by the Peltier element 34. In this way, the reinforcing portion 14 freezes and is fixed to the second support surface 22b.

[0037] After fixing the reinforcing portion 14 of the wafer 2 to the second support surface 22b of the table body 18, the protective tape 40 is peeled off from the surface 2a of the wafer 2 (see Figures 9(a) and 9(b)). The protective tape 40 may be peeled off by the operator's hand, or it may be peeled off using an appropriate tape peeling device (not shown). After the protective tape 40 is peeled off, current is supplied to the Peltier element 34 of the second cooling means 20b in the opposite direction to the predetermined direction. This heats and thaws the ice between the second support surface 22b and the reinforcing portion 14, and the wafer 2 is removed from the freezing table 16.

[0038] As described above, in the peeling process of this embodiment, the protective tape 40 is peeled off from the surface 2a of the wafer 2 using a freezing table 16 that holds only the ring-shaped reinforcing portion 14 formed on the back surface 2b of the wafer 2 and does not come into contact with the back surface 2b corresponding to the device area 8. Therefore, according to this embodiment, no foreign matter adheres to or scratches the back surface 2b corresponding to the device area 8, and the protective tape 40 can be peeled off from the surface 2a of the wafer 2 without damaging the outer circumference of the wafer 2. [Explanation of Symbols]

[0039] 2: Wafer 2a: Wafer surface 2b: Back side of the wafer 4: Device 6: Planned division line 8: Device area 10: Peripheral surplus area 14: Reinforcement 16: Frozen Table 18: Table body 20: Cooling means 20a: First cooling means 20b: Second cooling method 22: Support surface 22a: First support surface 22b: Second support surface 32: Atmospheric vent 40: Protective tape 42: Chuck Table

Claims

1. A method for processing a wafer in which multiple devices are formed on the surface, with a device region demarcated by division lines and an outer peripheral surplus region surrounding the device region, A protective tape application process in which protective tape is applied to the surface of the wafer, A holding step in which the protective tape is placed facing the chuck table to hold the wafer, A grinding step is performed to thin the back surface of the wafer held on the chuck table that corresponds to the device area, and to form a ring-shaped reinforcing portion in the area corresponding to the excess outer peripheral area. A cleaning process for cleaning wafers, The process includes a peeling step of peeling the protective tape from the surface of the wafer, A wafer processing method comprising peeling off the protective tape from the surface of the wafer using a freezing table that supports only the ring-shaped reinforcing portion formed on the back surface of the wafer and does not contact the back surface corresponding to the device area.

2. A freezing table according to claim 1, A table body having a support surface that supports a ring-shaped reinforcing portion formed on the back surface of the wafer, A freezer table comprising a cooling means disposed on the opposite side of the support surface.

3. The refrigeration table according to claim 2, wherein the table body has two or more support surfaces formed thereon corresponding to the diameter of the wafer, the support surfaces are treated with a hydrophilic coating, and the surfaces other than the support surfaces are treated with a water-repellent coating.

4. The refrigeration table according to claim 2, wherein the table body is formed of a material having the same coefficient of thermal expansion as the wafer.

5. The refrigeration table according to claim 2, wherein the table body has an atmospheric vent that opens the space enclosed by the back surface of the wafer and the table body to the atmosphere.

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