Method for forming protective layer and method for processing work-piece

Abstract

To provide a new technique that can remove warpage and undulation included in a shape of a work-piece.SOLUTION: A method for forming a protective layer, which forms the protective layer for coating one side of a plate-like work-piece, comprises: a first protective layer forming step of forming a first protective layer constituted of water-soluble resin on the one side of the work-piece; a resin supply step of laying a film made of resin on a flat table and supplying liquid resin that is cured by external stimuli onto the film; a step of making the first protective layer face the liquid resin laid on the surface of the film to press the liquid resin; and a second protective layer forming step of curing the liquid resin by giving external stimuli to the liquid resin to form a second protective layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for processing a workpiece including deformation elements such as undulation and warpage. [Background technology]

[0002] Semiconductor device chips are essential components in various electronic devices. These chips are manufactured using disk-shaped workpieces made of semiconductors such as silicon (Si), silicon carbide (SiC), and gallium arsenide (GaAs).

[0003] Disk-shaped workpieces are generally cut from cylindrical ingots using a blade saw, wire saw, etc. The shape of the workpiece cut in this way often includes a curvature (warping) throughout the entire surface and minute waviness.

[0004] Therefore, workpieces cut from an ingot are often flattened to remove warpage and waviness before being used to manufacture chips for semiconductor devices.

[0005] As an effective method for removing warpage and waviness contained in the shape of a workpiece, for example, as shown in Patent Document 1, a method is known in which a cured ultraviolet curable resin is applied to one side of the workpiece and then the other side of the workpiece is ground. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-148866 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the method described in Patent Document 1, the UV-curable resin remains on the surface of the workpiece during peeling, which can cause problems with the workpiece being adsorbed and fixed properly during backside grinding, or can cause the workpiece to crack during grinding.In addition, the remaining UV-curable resin can cause contamination inside the equipment.

[0008] In view of the above problems, the present invention proposes a novel technique for removing warpage and waviness contained in the shape of a workpiece. [Means for solving the problem]

[0009] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0010] According to one aspect of the present invention, there is provided a method for forming a protective layer that covers one side of a plate-shaped workpiece, the method comprising: a first protective layer forming step of forming a first protective layer made of a water-soluble resin on one side of the workpiece; a resin supplying step of laying a resin film on a flat table and supplying a liquid resin that hardens in response to an external stimulus onto the film; a pressing step of bringing the first protective layer face-to-face with the liquid resin laid on the surface of the film and pressing the liquid resin; and a second protective layer forming step of applying an external stimulus to the liquid resin to harden the liquid resin and form a second protective layer.

[0011] According to one aspect of the present invention, the first protective layer made of the water-soluble resin is formed by spin coating.

[0012] According to one embodiment of the present invention, the first protective layer made of the water-soluble resin has a thickness of 5 μm or less.

[0013] According to one aspect of the present invention, there is provided a method for processing a workpiece, the method comprising: a first grinding step for holding the film on a chuck table to expose the back surface of the workpiece and grinding the back surface of the workpiece, the first grinding step for peeling the film, the second protective layer, and the first protective layer from the workpiece, and a second grinding step for holding the back surface of the workpiece on a chuck table to expose the front surface of the workpiece and grinding the front surface of the workpiece. [Effects of the Invention]

[0014] The present invention provides the following effects. That is, according to one aspect of the present invention, both the front and back surfaces of the workpiece are ground, thereby obtaining a workpiece in which warping and waviness on both surfaces are eliminated. Furthermore, because the first protective layer that comes into contact with the workpiece is made of a water-soluble resin, even if the water-soluble resin remains on the workpiece, it can be removed with the grinding water during grinding, preventing the water-soluble resin from remaining inside the device and causing contamination inside the device. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing an outline of the configuration of a protective film forming apparatus. [Figure 2] FIG. 1 is a diagram illustrating steps constituting one embodiment of the present invention. [Figure 3] 10(A) and 10(B) are diagrams illustrating a first protective layer forming step. [Figure 4] 10(A) and 10(B) are diagrams illustrating the resin supply step. [Figure 5] 10(A) and 10(B) are diagrams illustrating the pressing step. [Figure 6] 10(A) and 10(B) are diagrams illustrating the second protective layer forming step. [Figure 7] 10(A) and 10(B) are diagrams illustrating the first grinding step. [Figure 8] (A) and (B) are diagrams showing the peeling step. [Figure 9]10(A) and 10(B) are diagrams illustrating the second grinding step. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing an outline of the configuration of a protective film forming apparatus 1 used in a method for forming a protective film. Fig. 1 shows how, in the protective film forming apparatus 1, a first protective layer H1 made of a water-soluble resin formed on a wafer, which is a workpiece W, faces a liquid resin 25 laid on the upper surface of a film S.

[0017] The protective film forming apparatus 1 is composed of a table 2 (lower surface plate), a holding means 4 (holding pad), a lifting means 6, an ultraviolet light irradiation means 5, a liquid resin supply means 3, and a control device 7 for controlling various operating parts.

[0018] The table 2 has a horizontal upper surface 2a and is configured to transmit ultraviolet light, and is made of a transparent material such as glass. A suction groove that leads to a suction source (not shown) is formed on the horizontal upper surface 2a, and by generating negative pressure on the upper surface 2a, the upper surface 2a is configured to function as a suction holding surface.

[0019] The holding means 4 (upper surface plate) is disposed above the horizontal upper surface 2a of the table 2, and its horizontal lower surface 4a has suction grooves formed therein that communicate with a suction source (not shown), and by generating negative pressure on the lower surface 4a, the lower surface 4a is configured as a suction holding surface. One side (upper surface) of the wafer, which is the workpiece W, is suction-held by the lower surface 4a, and the first protective layer H1 on the other side (lower surface) is exposed.

[0020] The holding means 4 is fixed to the underside of the lifting base 61 of the lifting means 6, and moves up and down together with the lifting base 61. The lifting means 6 has an actuator (not shown), and the lifting base 61 moves up and down by operating the actuator.

[0021] The ultraviolet light irradiation means 5 is disposed below the table 2 and has a light source 5a for emitting ultraviolet light. As will be described in detail later, the ultraviolet light passes through the table 2 and the film S and hardens the liquid resin 25.

[0022] The liquid resin supply means 3 has a supply nozzle 3a for supplying liquid resin 25 onto the upper surface of a film S or the like laid on the table 2. The supply nozzle 3a is configured to be movable by an actuator (not shown), and can be positioned at a supply position where the supply nozzle 3a is positioned at the center of the table 2, and at a retracted position where the supply nozzle 3a is away from the table 2. The supply nozzle 3a is connected to a liquid resin supply source (not shown), and can supply a predetermined amount of liquid resin 25 onto the upper surface of the film S.

[0023] Next, a description will be given of a method for forming a protective layer using the protective film forming apparatus 1 configured as above. Figure 2 is a diagram showing steps constituting one embodiment of the present invention.

[0024] <First protective layer formation step> As shown in FIGS. 3(A) and 3(B), this is a step of forming a first protective layer H1 made of a water-soluble resin on one side of the workpiece W.

[0025] Specifically, in the spin coater 8, the workpiece W is placed on a holding surface 82a of a turntable 82 that rotates in a horizontal plane, with the surface Wa exposed. The turntable 82 is driven to rotate by a motor (not shown), causing the holding surface 82a to rotate at a predetermined rotation speed. The holding surface 82a is connected to a suction source (not shown), and negative pressure is generated on the holding surface 82a, thereby suction-holding the workpiece W.

[0026] The workpiece W is a disk-shaped material made of a semiconductor such as silicon (Si), silicon carbide (SiC), or gallium arsenide (GaAs), and is cut from a cylindrical ingot using a blade saw, wire saw, etc. The front surface Wa and back surface Wb of the workpiece W will have warping or undulations, which will be removed in a subsequent process.

[0027] Then, water-soluble resin 85 is dropped from a supply nozzle 84 onto the center of the surface Wa of the rotating workpiece W, and centrifugal force causes the water-soluble resin 85 to spread over the surface Wa of the workpiece W, forming a first protective layer H1 made of the water-soluble resin 85 on the surface Wa.

[0028] The water-soluble resin 85 for forming the first protective layer H1 is, for example, polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP), which can be easily dissolved and removed by water.

[0029] The thickness of the first protective layer H1 can be, for example, 5 μm or less. As will be described later, the first protective layer H1 is to be removed, and its purpose is to ensure removability when peeled off in a later process. From the viewpoint of the consumption amount of the first protective layer H1, it is preferable to keep the consumption amount to 5 μm or less.

[0030] The above-described formation of the first protective layer H1 is performed by so-called spin coating, in which the water-soluble resin 85 is spread by centrifugal force to coat the surface Wa of the workpiece W, and the first protective layer H1 (water-soluble resin 85) adheres to the surface Wa after a predetermined time has passed since coating. Note that the first protective layer H1 may also be formed by other methods, such as a casting method.

[0031] <Resin supply step> As shown in Figures 4(A) and (B), in the protective film forming apparatus 1 (Figure 1), this is a step in which a resin film S is laid on a flat table 2 and a liquid resin 25 that hardens when exposed to an external stimulus is supplied onto the film S.

[0032] Specifically, first, a resin film S is laid on the horizontal upper surface 2a of the table 2. The film S is made of, for example, a film made of a transparent PET (polyethylene terephthalate) material that transmits ultraviolet light.

[0033] The film S is, for example, circular and configured to have a diameter larger than the surface Wa of the workpiece W (first protective layer H1 (FIG. 3(B)). Alternatively, the film S may have substantially the same shape as the upper surface 2a of the table 2 and cover substantially the entire area of ​​the upper surface 2a. Alternatively, the film S may be rectangular in shape instead of circular.

[0034] As shown in Fig. 1, a supply nozzle 3a is positioned above the approximate center of the film S, and liquid resin 25 is dripped from the supply nozzle 3a, thereby supplying a predetermined amount of liquid resin 25 to the upper surface 2a, resulting in the state shown in Fig. 4(B). The liquid resin 25 is, for example, an ultraviolet-curable resin, such as "ResiFlat" (registered trademark) manufactured by Disco Corporation. After curing, the liquid resin 25 transmits ultraviolet light.

[0035] <Pressing step> As shown in FIGS. 5(A) and 5(B), this is a step in which the first protective layer H1 is placed facing the liquid resin 25 laid on the surface of the film S, and the liquid resin is pressed.

[0036] Specifically, first, in Fig. 1, the supply nozzle 3a is retracted away from a position above the table 2. Then, as shown in Fig. 5(A), the back surface Wb of the workpiece W is suction-held by the lower surface 4a of the holding means 4 to expose the first protective layer H1 downward, and as shown in Fig. 5(B), the workpiece W is lowered by the elevating means 6 (Fig. 1). When the front surface H1a of the first protective layer H1 reaches the liquid resin 25, the liquid resin 25 is pressed and spread without any gaps between the first protective layer H1 and the film S. As a result, a film of the liquid resin 25 is formed between the first protective layer H1 and the film S.

[0037] <Second protective layer formation step> As shown in FIGS. 6(A) and 6(B), this is a step in which an external stimulus is applied to the liquid resin 25 to harden the liquid resin 25, thereby forming a second protective layer H2.

[0038] Specifically, as shown in Fig. 6(A), the suction holding of the workpiece W is released and the holding means 4 is retracted away from the workpiece W. Next, ultraviolet light UV is irradiated from below by the ultraviolet light irradiation means 5 (Fig. 1), and the liquid resin 25 is irradiated with ultraviolet light UV through the table 2 to harden the liquid resin 25. As a result, the liquid resin 25 having a predetermined thickness is hardened, and a second protective layer H2 is formed, as shown in Fig. 6(B).

[0039] In this embodiment, the external stimulus for hardening the liquid resin 25 is irradiation with ultraviolet light. However, other external stimuli may be used, for example, heat, in which case it is possible to use a thermosetting resin as the liquid resin.

[0040] <First grinding step> As shown in Figures 7(A) and (B), this is a step in which a composite member integrating a film S, a second protective layer H2, a first protective layer H1, and a workpiece W is used as a workpiece Wk for grinding, the film S is held on a chuck table 71 to expose the back surface Wb of the workpiece W, and the back surface Wb of the workpiece W is ground.

[0041] Specifically, first, the film S of the workpiece Wk is sucked and held on the chuck table 71 of the grinding device. Here, in the workpiece Wk, the film S, the second protective layer H2, the first protective layer H1, and the workpiece W are integrated, and the back surface Wb of the workpiece W is exposed.

[0042] The grinding device 70 is mainly composed of a chuck table 71 and a grinding unit 72, and is configured to flatten the front and back surfaces of the workpiece W by grinding.

[0043] The holding surface 71a of the chuck table 71 constitutes a horizontal plane, and suction grooves (not shown) are formed on the surface thereof, and by generating negative pressure in the suction grooves, the film S is sucked and held on the holding surface 71a. The chuck table 71 is configured to rotate by a rotation mechanism (not shown).

[0044] The grinding unit 72 has a grinding wheel 74 in which a plurality of grinding stones 74a are arranged at intervals in an annular shape. The grinding wheel 74 is rotated at a predetermined speed by a rotation mechanism (not shown) and is fed for grinding at a predetermined speed by a grinding feed mechanism (not shown).

[0045] By grinding the grinding unit 72 by a predetermined distance, the back surface Wb of the workpiece W is flattened, and warping and undulations on the back surface Wb are eliminated. After grinding, the back surface Wb of the workpiece W and the holding surface 71a of the chuck table 71 become parallel, and the back surface Wb of the workpiece W becomes horizontal.

[0046] <Peeling step> As shown in FIGS. 8(A) and 8(B), this is a step of peeling the film S, the second protective layer H2, and the first protective layer H1 from the workpiece W.

[0047] Specifically, for example, the workpiece Wk that has completed the first grinding step is inverted, and the back surface Wb of the workpiece W is held by suction on the holding surface 71a of the chuck table 71 to expose the film S to the upper side, and the end of the film S is grasped by the clamp 76 and rolled up.

[0048] As a result, the film S, the second protective layer H2, and the first protective layer H1 are peeled off integrally from the workpiece W, and the surface Wa of the workpiece W is exposed.

[0049] During this peeling process, there is a possibility that part of the first protective layer H1 may remain on the surface Wa of the workpiece W, but since the first protective layer H1 is a water-soluble resin, this is not a problem as it will be removed by grinding in the subsequent second grinding step or by the grinding water supplied to the processing point during grinding.

[0050] <Second grinding step> As shown in Figures 9(A) and (B), this is a step in which the back surface Wb of the planarized workpiece W is held on a chuck table 71 to expose the front surface Wa of the workpiece W, and the front surface Wa of the workpiece W is ground.

[0051] Specifically, the back surface Wb of the workpiece W that has been planarized after the peeling step is sucked and held on the chuck table 71 of the grinding device. Note that the grinding device used in the first grinding step may be replaced by another grinding device.

[0052] Then, by grinding and feeding the grinding unit 72 a predetermined distance, the front surface Wa of the workpiece W is flattened, and any warping or waviness of the front surface Wa is eliminated. Furthermore, because the back surface Wb of the workpiece W has been flattened in advance by the second grinding step, after grinding, the front surface Wa of the workpiece W and the holding surface 71a of the chuck table 71 become parallel, and the front surface Wa of the workpiece W becomes horizontal.

[0053] In this manner, both the front surface Wa and the back surface Wb of the workpiece W are ground, and a workpiece W can be obtained in which warping and waviness on both surfaces are eliminated. Furthermore, because the first protective layer H1 in contact with the workpiece W (front surface Wa) is made of a water-soluble resin, even if the water-soluble resin remains on the workpiece W (front surface Wa), it can be removed with the grinding water during grinding, preventing the water-soluble resin from remaining inside the apparatus and contaminating the apparatus. [Explanation of symbols]

[0054] 1 Protective film forming device 2 tables 2a Top side 3 Liquid resin supply means 3a Supply nozzle 4 Holding means 4a Bottom side 5 Ultraviolet light irradiation means 5a light source 6 Lifting means 7 Control Device 8 Spin Coating Equipment 25 Liquid Resin 61 Lifting Platform 70 Grinding equipment 71 Chuck table 71a Holding surface 72 Grinding Unit 74 Grinding Wheel 74a Grinding wheel 76 Clamp 82 Turntable 82a Holding surface 84 supply nozzle 85 Soluble Resin H1 First protective layer H1a surface H2 second protective layer S film UV ultraviolet light W Workpiece Wa surface Wb back side Wk Work

Claims

1. A method for forming a protective layer that covers one side of a plate-shaped workpiece, comprising: a first protective layer forming step of forming a first protective layer made of a water-soluble resin on one side of the workpiece; a resin supplying step of laying a resin film on a flat table and supplying a liquid resin that hardens in response to an external stimulus onto the film; a pressing step of placing the first protective layer against the liquid resin laid on the surface of the film and pressing the liquid resin; and a second protective layer forming step of applying an external stimulus to the liquid resin to harden the liquid resin and form a second protective layer.

2. the first protective layer made of the water-soluble resin is formed by spin coating; The method for forming a protective layer according to claim 1 .

3. the thickness of the first protective layer made of the water-soluble resin is 5 μm or less; 3. The method for forming a protective layer according to claim 1 or 2.

4. Regarding the workpiece formed by the method for forming a protective layer according to claim 1 or 2, a first grinding step of holding the film on a chuck table to expose a back surface of the workpiece and grinding the back surface of the workpiece; a peeling step of peeling the film, the second protective layer, and the first protective layer from the workpiece; a second grinding step of holding the back surface of the workpiece on a chuck table to expose the front surface of the workpiece and grinding the front surface of the workpiece. A method for processing a workpiece, comprising:

5. Regarding the workpiece formed by the method for forming a protective layer according to claim 3, a first grinding step of holding the film on a chuck table to expose a back surface of the workpiece and grinding the back surface of the workpiece; a peeling step of peeling the film, the second protective layer, and the first protective layer from the workpiece; a second grinding step of holding the back surface of the workpiece on a chuck table to expose the front surface of the workpiece and grinding the front surface of the workpiece. A method for processing a workpiece, comprising:

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