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

Abstract

To provide a new technique for protecting a surface having unevenness of a work-piece, without using a soft film.SOLUTION: A method for forming a protective layer, which forms the protective layer on a surface having unevenness of a work-piece, comprises: a coating step of coating the surface of the work-piece with water-soluble resin; a resin supply step of supplying liquid resin that is cured by external stimuli onto the surface of the water-soluble resin coating the surface of the work-piece; a pressing step of pressing the liquid resin supplied to the surface of the work-piece, through a film, using a flat pressing surface, and pressing and expanding the liquid resin, between the film and the work-piece; and a curing step of curing the liquid resin pressed and expanded in the pressing step to form a protective layer constituted of the film, the cured liquid resin and the water-soluble resin on the surface of the work-piece.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for forming a protective member on the surface of a workpiece having an uneven surface. [Background technology]

[0002] It is known that device chips used in electronic devices are processed by grinding a substrate on which multiple devices are arranged from the backside to thin the substrate, and then dividing the substrate into individual devices.

[0003] Grinding of the back surface of a workpiece is performed using a grinding device, in which the front surface of the workpiece is held on a chuck table with the back surface exposed upward, and a grinding wheel moving on a circular orbit is brought into contact with the back surface of the workpiece to grind the workpiece.

[0004] At this time, patterns constituting devices and wiring are arranged on the surface side of the workpiece, and in order to protect these, a protective member consisting of a substrate layer and an adhesive layer is attached to the surface of the workpiece in advance.

[0005] In addition, bumps may be formed on the surface of the substrate, which is the workpiece, to establish electrical contact with the device, resulting in unevenness with varying heights on the surface of the substrate. In devices with unevenness with varying heights, the adhesive layer of the attached protective member alone cannot fully absorb the unevenness of the surface, and the surface held on the chuck table will not be flat.

[0006] In such cases, the workpiece (substrate) is not supported uniformly by the chuck table when grinding using a grinding device, which causes problems such as the back surface not being flat after back grinding and causing cracks or chips.

[0007] One possible solution to this problem is to use a protective material with a thick adhesive layer that can fully absorb the unevenness of the surface of the workpiece (substrate). However, in this case, when the protective material is peeled off from the substrate, residue from the adhesive layer is likely to remain on the unevenness, which could cause defects in the device chip.

[0008] In relation to the above, for example, Patent Document 1 discloses an application in which the surface (device surface) of a workpiece (substrate) is protected in advance with a soft resin film, a liquid resin that hardens in response to an external stimulus is supplied onto the surface, and then pressure is applied through another protective film to cause the liquid resin to penetrate into the irregularities of the substrate, and the liquid resin is hardened to form a protective layer.

[0009] In Patent Document 1, a soft film is adhered to the surface of the substrate so as to conform to the unevenness of the surface of the workpiece (substrate). Note that no adhesive layer is formed on the film at least in the area that is in close contact with the device formation area of ​​the substrate, and the adhesive layer does not come into contact with the device formation area of ​​the substrate. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2017-50536 Summary of the Invention [Problem to be solved by the invention]

[0011] When using a soft film as in Patent Document 1, the film needs to go through processes such as heating and stretching (expansion) in order to adhere to the surface of the substrate (device surface) while conforming to the unevenness of the surface of the workpiece (substrate).

[0012] In view of the above problems, the present invention proposes a novel technique for protecting the uneven surface of a workpiece without using a soft film. [Means for solving the problem]

[0013] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0014] According to one aspect of the present invention, there is provided a method for forming a protective layer on the surface of a workpiece having an uneven surface, the method comprising: a coating step for covering the surface of the workpiece with a water-soluble resin; a resin supplying step for supplying a liquid resin that hardens in response to an external stimulus to the surface of the water-soluble resin that has coated the surface of the workpiece; a pressing step for pressing the liquid resin supplied to the surface of the workpiece with a flat pressing surface via a film, thereby spreading the liquid resin between the film and the workpiece; and a curing step for hardening the liquid resin spread in the pressing step, thereby forming a protective layer consisting of the film, the hardened liquid resin, and the water-soluble resin on the surface of the workpiece.

[0015] According to another aspect of the present invention, the water-soluble resin is applied to the surface of the workpiece by spin coating.

[0016] According to another aspect of the present invention, the thickness of the layer formed from the water-soluble resin from the surface of the workpiece is 5 μm or less.

[0017] According to one aspect of the present invention, a method for processing a workpiece includes a grinding step for holding the film on a chuck table to expose the back surface of the workpiece formed by the protective layer forming method, and grinding the back surface of the workpiece, and a peeling step for peeling the protective layer from the workpiece.

[0018] According to one aspect of the present invention, the method further comprises, after the peeling step, a water washing step of washing the surface of the workpiece with water. [Effects of the Invention]

[0019] The present invention provides the following effects. That is, according to one aspect of the present invention, it is possible to protect the uneven surface of a workpiece without using a soft film, which makes it possible to omit steps such as heating or stretching (expanding) the film when using a soft film.

[0020] Furthermore, according to one aspect of the present invention, the uneven surface of the workpiece is coated with a water-soluble resin, so that even if the water-soluble resin remains on the surface of the workpiece after the protective layer is peeled off, it can be removed by the grinding water used during grinding. [Brief explanation of the drawings]

[0021] [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] (A) and (B) are diagrams showing the coating step. [Figure 4] 1A and 1B are diagrams showing examples of workpieces having uneven surfaces; [Figure 5] 10(A) and 10(B) are diagrams illustrating the resin supply step. [Figure 6] 10(A) and 10(B) are diagrams illustrating the pressing step. [Figure 7] (A) and (B) are diagrams showing the curing step. [Figure 8] (A) and (B) are diagrams showing the grinding step. [Figure 9] (A) and (B) are diagrams showing the peeling step. [Figure 10] (A) and (B) are diagrams showing the water washing step. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 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. In FIG. 1, a film S is placed opposite a workpiece W coated with a water-soluble resin 85 in the protective film forming apparatus 1.

[0023] 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.

[0024] The table 2 has a horizontal upper surface 2a. A suction groove communicating with a suction source (not shown) is formed in the horizontal upper surface 2a, and by generating a negative pressure on the upper surface 2a, the upper surface 2a is configured as a suction holding surface.

[0025] 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.

[0026] The holding means 4 has an upper surface plate 4J having a horizontal lower surface 4a, and an ultraviolet light irradiation means 5 for irradiating ultraviolet light through the upper surface plate 4J.

[0027] The upper surface plate 4J is disposed above the horizontal upper surface 2a of the table 2 and is made of a transparent material such as glass. The lower surface 4a of the upper surface plate 4J has suction grooves 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. The lower surface 4a of the upper surface plate 4J holds the film S by suction. As will be described in detail later, the lower surface 4a of the upper surface plate 4J also functions as a flat pressing surface for pressing the liquid resin 25 through the film S.

[0028] The ultraviolet light irradiation means 5 is configured to have a light source that emits ultraviolet light, and is configured so that the ultraviolet light can pass through the upper surface plate 4J and be irradiated below the holding means 4. As will be described in detail later, the ultraviolet light irradiated from the ultraviolet light irradiation means 5 passes through the film S and hardens the liquid resin 25.

[0029] The liquid resin supply means 3 is held on the table 2 (lower surface plate) and has a supply nozzle 3a for supplying liquid resin 25 onto the upper surface of the workpiece W coated with water-soluble resin 85. 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 or the like.

[0030] Next, a method for forming a protective layer using the protective film forming apparatus configured as above will be described. Figure 2 is a diagram showing steps constituting one embodiment of the present invention.

[0031] <Coating step> As shown in FIGS. 3(A) and 3(B), this is a step of covering the surface Wa of the workpiece W with a water-soluble resin 85.

[0032] 4, the workpiece W is a disk-shaped wafer 10 made of a semiconductor such as silicon (Si), silicon carbide (SiC), or gallium arsenide (GaAs), and has devices 14 formed in each region defined by dividing lines 12, 12 set in a grid pattern on the surface 10a of the wafer 10. Bumps 16 (also called high bumps) are formed on the devices 14 to establish electrical contact with the devices 14, and these bumps 16 form irregularities on the surface of the wafer 10. Note that the irregularities may be formed by the bumps 16 or by a pattern such as a TEG 18.

[0033] 3(A), in a spin coater 8, the workpiece W described above is placed on a holding surface 82a of a turntable 82 that rotates in a horizontal plane, exposing the uneven surface Wa. 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), which generates a negative pressure on the holding surface 82a, thereby suction-holding the workpiece W.

[0034] Then, by dropping water-soluble resin 85 from a supply nozzle 84 onto the center of the surface Wa of the rotating workpiece W, the water-soluble resin 85 spreads over the surface Wa of the workpiece W due to centrifugal force, and the surface Wa is coated with the water-soluble resin 85, as shown in Figure 3(B).

[0035] The water-soluble resin 85 may be, for example, polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP), which can be easily dissolved and removed by water.

[0036] As shown in FIG. 3B, the water-soluble resin 85 covers the surface Wa, and thus the gaps between the irregularities formed by the bumps are filled with the water-soluble resin 85. When the water-soluble resin 85 covers the surface Wa so as to completely eliminate the irregularities, a protective layer is formed by the water-soluble resin 85, and in this case the thickness of the protective layer H can be set to, for example, 5 μm or less. As will be described later, the water-soluble resin 85 is to be removed, and its purpose is to ensure removability when peeled off in a subsequent process. From the viewpoint of the amount of consumption of the protective layer as well, it is preferable to keep the consumption to 5 μm or less.

[0037] The water-soluble resin 85 may cover the surface Wa so that the irregularities are completely eliminated after coating, or may cover the surface Wa so that irregularities remain after coating.

[0038] The coating of the surface Wa of the workpiece W with the water-soluble resin 85 described above is a so-called spin coating method in which the water-soluble resin 85 is spread by centrifugal force to coat the surface Wa of the workpiece W, and the water-soluble resin 85 adheres to the surface Wa after a predetermined time has passed since coating. Note that other methods such as a casting method may also be used.

[0039] <Resin supply step> As shown in Figures 5(A) and (B), this is a step in which a liquid resin 25 that hardens in response to an external stimulus is supplied to the surface 85a of the water-soluble resin 85 that coats the surface Wa of the workpiece W in the protective film forming apparatus 1 (Figure 1).

[0040] Specifically, the workpiece W is removed from the turntable 82 (FIG. 4(B)) of the spin coater 8, and as shown in FIG. 1, the workpiece W is set on the table 2 so that the surface 85a of the water-soluble resin 85 is exposed. Then, the supply nozzle 3a is positioned above the approximate center of the workpiece W, and liquid resin 25 is dripped from the supply nozzle 3a, thereby supplying a predetermined amount of liquid resin 25 to the surface of the workpiece W covered with the water-soluble resin 85. The liquid resin 25 is, for example, an ultraviolet-curable resin, such as "ResiFlat" (registered trademark) manufactured by Disco Corporation. The liquid resin 25 is transparent to ultraviolet light after it has hardened.

[0041] <Pressing step> As shown in Figures 6(A) and (B), this is a step in which the liquid resin 25 supplied to the surface of the workpiece is pressed against a flat pressing surface (the lower surface 4a of the upper surface plate 4J) through the film S, and the liquid resin 25 is spread between the film S and the workpiece W (the surface 85a of the water-soluble resin 85).

[0042] Specifically, first, supply nozzle 3a (FIG. 1) is retracted away from a position above table 2. Then, a resin film S is laid on the horizontal lower surface 4a of upper surface plate 4J and is held by suction to prevent film S from falling. Film S is made of, for example, a film (sheet) made of a transparent PET (polyethylene terephthalate) material that transmits ultraviolet light.

[0043] The film S is, for example, circular and configured to have a diameter larger than the surface Wa of the workpiece W covered with the water-soluble resin 85. Alternatively, the film S may have substantially the same shape as the lower surface 4a of the upper surface plate 4J and cover substantially the entire area of ​​the lower surface 4a. Alternatively, the film S may be rectangular in shape instead of circular.

[0044] Then, the film S (upper surface plate 4J) is lowered by the lifting means 6 (FIG. 1). When the film S reaches the liquid resin 25, the liquid resin 25 is spread without any gaps between the film S and the surface Wa of the workpiece W coated with the water-soluble resin 85 (surface 85a of the water-soluble resin 85).

[0045] <Curing step> As shown in Figures 7(A) and (B), this is a step in which the liquid resin 25 that has been spread in the pressing step is hardened, and a protective layer H consisting of a film S, the hardened liquid resin 25, and a water-soluble resin 85 is formed on the surface Wa of the workpiece W.

[0046] Specifically, while the liquid resin 25 is pressed, ultraviolet light UV is irradiated onto the liquid resin 25 from above through the film S by the ultraviolet light irradiation means 5 (FIG. 1), thereby hardening the liquid resin 25. This hardens the liquid resin 25, and a protective layer H made up of the film S, the hardened liquid resin 25, and the water-soluble resin 85 is formed.

[0047] 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.

[0048] <Grinding step> As shown in Figures 8(A) and (B), the workpiece Wk to be ground is formed using the above-mentioned method for forming a protective layer H, and 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.

[0049] The grinding device 70 is mainly composed of a chuck table 71 and a grinding unit 72, and is configured to flatten the back surface Wb of the workpiece W by grinding.

[0050] 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).

[0051] 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).

[0052] By grinding and feeding the grinding unit 72 by a predetermined distance, the back surface Wb of the workpiece W is flattened and the workpiece W is thinned.

[0053] <Peeling step> As shown in FIGS. 9(A) and 9(B), this is a step of peeling the protective layer H from the workpiece W.

[0054] 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 another holding table 73 to expose the film S on the upper side, and the end of the film S is grasped by a clamp 76 and rolled up.

[0055] As a result, the protective layer H including the film S is peeled off from the workpiece W, and the surface Wa of the workpiece W is exposed.

[0056] During this peeling, there is a possibility that water-soluble resin 85, which is part of the protective layer H, may remain in gaps between the unevenness of the surface Wa of the workpiece W, but since it is water-soluble resin 85, it can be easily removed by washing with water.

[0057] <Water washing step> As shown in Figures 10(A) and (B), in consideration of the possibility that water-soluble resin 85, which is part of the protective layer H, may remain, a water cleaning step may be performed after the peeling step to clean the surface Wa of the workpiece W with water.

[0058] Specifically, for example, the back surface Wb of the workpiece W is suction-held on the table 77 of the water cleaning device, the table 77 is rotated to rotate the workpiece W, and water is sprayed from the water cleaning nozzle 78 toward the front surface Wa of the workpiece W, thereby removing the water-soluble resin 85 remaining on the front surface Wa.

[0059] In this way, it is possible to protect the uneven surface of the workpiece without using a soft film, which makes it possible to omit the steps of heating or stretching (expanding) the film when using a soft film.

[0060] Furthermore, since the uneven surface of the workpiece is coated with a water-soluble resin, even if the water-soluble resin remains on the workpiece W (surface Wa) after the protective layer is peeled off, it can be removed by the grinding water used during grinding. [Explanation of symbols]

[0061] 1 Protective film forming device 2 tables 2a Top side 3 Liquid resin supply means 3a Supply nozzle 4 Holding means 4J upper surface plate 4a Bottom side 5 Ultraviolet light irradiation means 6 Lifting means 7 Control Device 8 Spin Coating Equipment 10 wafers 10a surface 12 Planned division line 14 devices 16 Bump 25 Liquid Resin 61 Lifting Platform 70 Grinding equipment 71 Chuck table 71a Holding surface 72 Grinding Unit 73 Holding Table 74 Grinding Wheel 74a Grinding wheel 76 Clamp 78 Water cleaning nozzle 82 Turntable 82a Holding surface 84 supply nozzle 85 Water-soluble resin 85a surface H 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 on a surface of a workpiece having an uneven surface, the method comprising: a coating step of covering the surface of the workpiece with a water-soluble resin; a resin supplying step of supplying a liquid resin that hardens in response to an external stimulus onto the surface of the water-soluble resin that has coated the surface of the workpiece; a pressing step in which the liquid resin supplied to the surface of the workpiece is pressed with a flat pressing surface via a film, thereby spreading the liquid resin between the film and the workpiece; a curing step of curing the liquid resin spread in the pressing step to form a protective layer on the surface of the workpiece, the protective layer being made of the film, the cured liquid resin, and the water-soluble resin; A method for forming a protective layer, comprising:

2. The water-soluble resin is coated on the surface of the workpiece by spin coating. The method for forming a protective layer according to claim 1 .

3. the thickness of the layer formed of the water-soluble resin from the surface of the workpiece 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 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 protective layer from 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 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 protective layer from the workpiece; A method for processing a workpiece, comprising:

6. After the peeling step, Further comprising a water washing step of washing the surface of the workpiece with water.

5. The method for processing a workpiece according to claim 4.

7. After the peeling step, Further comprising a water washing step of washing the surface of the workpiece with water.

6. The method for processing a workpiece according to claim 5.

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