Resin composition, surface protection method, and workpiece processing method

Abstract

To provide a new technology that can prevent processing defects caused by the uneven surface of a surface protective sheet and allows the surface protective sheet to be easily peeled off from a wafer after processing when the wafer held on a holding table is processed through the surface protective sheet.SOLUTION: A resin composition for forming a resin layer on a workpiece through a surface protection sheet includes (meth)acrylate, a chain transfer agent, and a photoinitiator.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a resin composition for forming a protective layer for protecting the surface of a workpiece, and a method for protecting a workpiece.

Background Art

[0002] Conventionally, for example, as disclosed in Patent Document 1, a surface protection sheet for protecting the surface of a wafer to be back-ground ground is known.

[0003] An adhesive layer is formed on the surface of this type of surface protection sheet, and the surface protection sheet and the wafer are integrated by an adhesive force by attaching the adhesive layer to the surface of the wafer.

[0004] However, particularly when a device is formed on the surface of the wafer, if the adhesive of the surface protection sheet remains on the device, it is difficult to remove the adhesive even in a subsequent cleaning process, and there is a risk of damaging the device. Further, particularly when a protruding electrode such as a bump is formed on the device surface, the adhesive attached to the root of the bump is difficult to remove, which may cause problems such as mounting defects.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, it is conceivable to use a surface protection sheet without an adhesive layer. However, when the height of the bumps is greater than the thickness of the surface protection sheet, the surface of the surface protection sheet attached to the wafer will not be flat, and irregularities will be formed. If the wafer is held on the holding table through the surface protection sheet in this state, the height of the upper surface (the height of the back surface) of the exposed wafer will not be uniform, and various problems may occur when processing the back surface side of the wafer.

[0007] Specifically, there are concerns that thickness variations may occur in the wafer after back grinding, height variations may occur in the modified layer formed during SD processing (Stealth Dicing (registered trademark) processing), areas that cannot be divided may occur in subsequent dicing processes, and variations may occur in the depth of the grooves formed by blades or lasers.

[0008] Here, it is conceivable to laminate a resin layer on the surface protection sheet and fill the irregularities formed by bumps or the like on the surface of the wafer to flatten the surface of the surface protection sheet and make the height of the upper surface (the height of the back surface) of the wafer uniform.

[0009] However, when peeling the surface protection sheet after processing, there is a concern that the surface protection sheet and the resin layer may separate, and only the resin layer may peel off. In this case, the surface protection sheet will remain attached to the wafer, and the entire surface protection sheet cannot be peeled off from the wafer.

[0010] Also, even when using a surface protection sheet having an adhesive layer, it is required to peel off the entire surface protection sheet from the wafer without separating the surface protection sheet and the resin layer.

[0011] In view of the above problems, the present invention provides a novel technique that prevents processing defects caused by the non-flat surface of the surface protection sheet when processing a wafer held on a holding table through the surface protection sheet, and enables easy peeling of the surface protection sheet from the wafer after processing.

Means for Solving the Problem

[0012] The problem to be solved by the present invention is as described above. Next, means for solving this problem will be described.

[0013] According to one aspect of the present invention, a resin composition for forming a resin layer on a workpiece through a surface protection sheet, (meth)acrylate, a chain transfer agent, a photoinitiator, and the resin composition contains these.

[0014] Also, according to one aspect of the present invention, the content of the chain transfer agent in the resin composition is 0.4 to 5 times that of the photoinitiator.

[0015] Also, according to one aspect of the present invention, the chain transfer agent is a thiol.

[0016] Also, according to one aspect of the present invention, a method for protecting one side surface of a workpiece using the resin composition, a surface protection sheet adhesion step of adhering the surface protection sheet to the surface of the workpiece, a protection layer formation step of supplying the resin composition onto the surface protection sheet, irradiating the resin composition with light to cure it and form a resin layer, and forming a protection layer having at least the surface protection sheet and the resin layer on the surface of the workpiece, and the surface protection method includes these steps.

[0017] Also, according to one aspect of the present invention, a processing method of a workpiece using the resin composition, a surface protection sheet adhesion step of adhering the surface protection sheet to the surface of the workpiece, A protective layer forming step of supplying the resin composition onto the surface protection sheet, irradiating the resin composition with light to cure it to form a resin layer, and forming a protective layer having at least the surface protection sheet and the resin layer on the surface of the workpiece; A thinning step of holding the protective layer side by a holding table and thinning the back side of the workpiece; A peeling step of peeling the protective layer from the surface of the workpiece; A processing method of the workpiece comprising the above steps is provided.

Effect of the Invention

[0018] In the present invention, a protective layer is formed by a surface protection sheet adhered to the surface of the workpiece and a resin layer laminated on the surface protection sheet. The resin layer is formed from a resin composition containing (meth)acrylate, a chain transfer agent, and a photopolymerization initiator. Thereby, even if irregularities are formed on the surface of the surface protection sheet, the irregularities can be absorbed by the resin layer, and the surface of the protective layer can be formed flat. Further, the surface protection sheet and the resin layer are firmly integrated and can be peeled off from the wafer as a whole without separation.

Brief Description of the Drawings

[0019]

Figure 1

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Figure 11

Embodiments for Carrying Out the Invention

[0020] Hereinafter, with reference to the accompanying drawings, this embodiment will be described. FIG. 1 shows a wafer 10 which is an example of a workpiece. The wafer 10 is a semiconductor wafer having silicon as a base material, and devices 14 such as ICs and LSIs are formed in a plurality of regions partitioned in a lattice pattern by a plurality of streets 12 on the surface 10a of the disk-shaped wafer 10.

[0021] As shown in the enlarged part of FIG. 1, a plurality of bumps 16 (electrodes) protruding from the surface 10a of the wafer 10 are formed at the peripheral portions of each device 14, and unevenness is formed on the surface 10a of the wafer 10 by these bumps 16. When a TEG (Test Element Group) is formed in the street 12, unevenness is also formed on the surface 10a of the wafer 10 by this TEG.

[0022] The workpiece to be processed according to the present invention includes various types other than the form shown in FIG. 1, and includes not only semiconductor wafers, but also optical device wafers, resin substrates, glass, ceramics, etc. as processing targets, and is not limited thereto.

[0023] For the wafer 10 having unevenness formed by bumps 16 on the surface 10a as described above, a method of forming a protective layer on the surface 10a will be described. In the following embodiments, each step of the flowchart shown in FIG. 2 is carried out in order.

[0024] <Surface protection sheet adhesion step> As shown in FIGS. 1 and 3(A)(B), this is a step of adhering a surface protection sheet 20 to the surface 10a of the wafer 10 which is the workpiece. The surface protection sheet 20 is a thin sheet-like member made of PO (polyolefin), PVC (polyvinyl chloride), PET (polyethylene terephthalate), polyvinylidene chloride (PVDC), PE (polyethylene), etc. PO is particularly preferably used because it has good followability to the unevenness of the bumps 16.

[0025] The back surface 20b of the surface protection sheet 20 is adhered to the surface 10a of the wafer 10 and is intended to be peeled off later. A paste layer that exhibits adhesive force is not formed on the back surface 20b of the surface protection sheet 20, and a material that does not cause the surface protection sheet 20 to adhere to the device 14 or the bumps 16 on the surface 10a of the wafer 10 can be used.

[0026] Note that a paste layer that exhibits adhesive force may be formed on the entire surface or a part of the back surface 20b of the surface protection sheet 20. For example, on the back surface 20b of the surface protection sheet 20, a ring-shaped paste layer may be formed along the outer peripheral edge of the wafer 10, and in the region outside the region where the device 14 is formed, the surface protection sheet 20 may be adhered to the wafer 10 via the paste layer.

[0027] In this embodiment, as shown in Fig. 3(A), the back surface 20b of the surface protection sheet 20 is placed on the surface 10a of the wafer 10, and the wafer 10 is set on the heating table 32 in the vacuum chamber 30 of the vacuum mounting device 3. Next, the inside of the vacuum chamber 30 is connected to the vacuum source 34 to evacuate it, and the wafer 10 is heated by the heating table 32 to raise the temperature of the surface 10a. As a result, as shown in Fig. 3(B), the softened surface protection sheet 20 adheres to the surface 10a of the wafer 10 while following the unevenness such as the bumps 16.

[0028] As shown in Fig. 3(B), the surface protection sheet 20 will have unevenness along the unevenness such as the bumps 16, but this unevenness will be eliminated by the resin layer 50 (Fig. 5(B)) described later.

[0029] In addition, as shown in Fig. 3(A), in addition to softening the surface protection sheet 20 by heating the wafer 10 with the heating table 32, the surface protection sheet 20 may be softened by a heater or a lamp that directly heats the surface protection sheet 20.

[0030] <Protection layer formation step> As shown in Figs. 4 and 5(A)(B), this is a step of supplying the resin composition 5 onto the surface protection sheet 20, irradiating the resin composition 5 with light to cure it to form the resin layer 50, and forming the protection layer 6 having at least the surface protection sheet 20 and the resin layer 50 on the surface 10a of the wafer 10 which is the workpiece.

[0031] Specifically, as shown in FIG. 4, first, a film 41 that transmits ultraviolet rays is disposed on the flat support surface 40a of the stage 40, and a predetermined amount of the resin composition 5 is placed on the upper surface of the film 41. As will be described later, the resin composition 5 is in a state where it can enter the unevenness formed on the surface protection sheet 20 without gaps. In addition to being a liquid with high viscosity and fluidity, a gel-like material without formability or a deformable solid (such as a sheet-like gel) can be used. Note that the resin composition 5 may be directly placed on the support surface 40a of the stage 40 without using the film 41.

[0032] The stage 40 is made of a transparent member such as glass and transmits ultraviolet rays irradiated from the light source 46a of the light irradiator 46 disposed below. The light source 46a can be constituted by an LED light (or a low-pressure mercury lamp, etc.) that irradiates ultraviolet rays with a predetermined wavelength.

[0033] The film 41 can be made of a resin that transmits ultraviolet rays. For example, it can be made of PET (polyethylene terephthalate). Further, as the film 41, a sheet-shaped one previously formed of the same resin as the resin composition 5 can also be used.

[0034] Next, the back surface 10b of the wafer 10 is held by the suction holding surface 62 of the wafer holding unit 60, and the surface protection sheet 20 is disposed on the lower side. The suction holding surface 62 communicates with the suction source 63, and the back surface 10b of the wafer 10 is suction-held by negative pressure. The surface protection sheet 20 is disposed on the lower side and faces the resin composition 5 placed on the film 41. The suction holding surface 62 of the wafer holding unit 60 is configured to be parallel to the flat support surface 40a of the stage 40.

[0035] Next, as shown in FIG. 5(A), by lowering the wafer holding unit 60, the resin composition 5 is spread by the surface protection sheet 20, and the gap between the surface protection sheet 20 and the film 41 is filled with the resin composition 5. As shown in FIG. 5(B), the resin composition 5 enters the unevenness formed on the surface protection sheet 20 without any gaps.

[0036] Next, as shown in FIG. 5(A), ultraviolet light of a predetermined wavelength is irradiated from the light source 46a to the resin composition 5 through the stage 40 and the film 41. As a result, the resin composition 5 is cured by the ultraviolet light to form a resin layer 50.

[0037] As described above, as shown in FIG. 5(B), a protective layer 6 having the surface protection sheet 20 and the resin layer 50 is formed on the surface 10a of the wafer 10 which is the workpiece. In this embodiment, the film 41 is laminated on the protective layer 6, and the lower surface 41a of the film 41 becomes flat along the support surface 40a of the stage 40. The film 41 may be regarded as a component of the protective layer 6, and the protective layer 6 may be composed of three layers: the surface protection sheet 20, the resin layer 50, and the film 41.

[0038] Note that, as shown in FIGS. 6(A) and (B), in the surface protection sheet adhesion step, the surface protection sheet 20 integrated with the annular frame 24 may be adhered to the wafer 10. In this case, the annular frame 24 and the surface protection sheet 20 are integrated by an adhesive layer 26 disposed outside the position of the wafer 10.

[0039] Then, as shown in FIGS. 7 and 8(A), in the protective layer formation step, the resin layer 50 is laminated on the surface protection sheet 20 integrated with the annular frame 24. Then, as shown in FIG. 8(B), after the resin layer 50 is laminated to form the protective layer 6, the surface protection sheet 20 is cut by a laser processing apparatus or the like to separate the annular frame 24, thereby forming a wafer 10 having the protective layer 6 as shown in FIG. 8(C). Note that the annular frame 24 may not be separated and the wafer 10 may be handled integrally.

[0040] Also, in the example described above, the wafer 10 held by the wafer holding unit 60 is lowered from above, and the resin composition 5 placed on the stage 40 is spread, and the resin layer 50 is formed between the surface protection sheet 20 and the film 41. However, the wafer 10 may be placed on the stage 40, the resin composition 5 may be placed on the surface protection sheet 20, and the film 41 may be covered over the resin composition 5 to spread the resin composition 5.

[0041] The resin composition 5 is configured to include a (meth)acrylate, a chain transfer agent, and a photopolymerization initiator. The (meth)acrylate refers to acrylate which is an acrylic acid compound or methacrylate which is a methacrylic acid compound. As the (meth)acrylate, those having a urethane bond (urethane group) and / or those not having a urethane bond can be used.

[0042] The (meth)acrylate having a urethane bond refers to a (meth)acrylate having a urethane group in the molecule. For example, light acrylates such as IAA, AT-600, UA-306H, UA-306T, UA-306I, UA-510H, UF-8001G, DAUA-167, UF-07DF (all manufactured by Kyoeisha Chemical Co., Ltd.), R-1235, R-1220, RST-201, RST-402, R-1301, R-1304, R-1214, R-1302XT, GX-8801A, R-1603, R-1150D, DOCR-102, DOCR-206 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), UX-3204, UX-4101, UXT-6100, UX-6101, UX-7101, UX-8101, UX-0937, UXF-4001-M35, UXF-4002, DPHA-40H, UX-5000, UX-5102D-M20, UX-5103D, UX-5005, UX-3204, UX-4101, UX-6101, UX-7101, UX-8101, UX-0937, UXF-4001-M35, UXF-4002, UXT-6100, DPHA-40H, UX-5000, UX-5102D-M20, UX-5103, UX-5005 (all manufactured by Nippon Kayaku Co., Ltd.) can be used.

[0043] (Meth)acrylate having no urethane bond refers to a compound having no (urethane group) in the molecule. For example, tetrahydrofurfuryl acrylate, isobornyl acrylate, 1,9-nonanediol diacrylate, etc. can be used.

[0044] As the chain transfer agent, the following can be used. 1-Butanethiol, cyclohexyl 3-mercaptopropionate, 1-decanethiol, 2,4-diphenyl-4-methyl-1-pentene, 1-dodecanethiol, dodecyl 3-mercaptopropionate, 2-ethylhexyl mercaptoacetate, ethyl mercaptoacetate, 1-hexadecanethiol, hexyl 3-mercaptopropionate, 2-mercaptoethanol, 3-mercapto-1,2-propanediol, mercaptoacetic acid, sodium 2-mercaptoethanesulfonate, 3-mercaptopropionic acid, methyl mercaptoacetate, mercaptosuccinic acid, methyl 3-mercaptopropionate, octadecyl 3-mercaptopropionate, octyl 3-mercaptopropionate, 1-octanethiol, 1-octadecanethiol, tridecyl 3-mercaptopropionate, thiophenol, etc. Among these, 1-dodecanethiol is particularly preferably used.

[0045] The photoinitiator is for initiating the photo (ultraviolet ray) polymerization of the resin composition 5, and the following can be used. 1-Hydroxycyclohexyl phenyl ketone (for example, Irgacure (registered trademark) 184 manufactured by BASF, etc.), α-hydroxyalkyl phenyl ketone (for example, Omnirad (registered trademark) 184 manufactured by IGM Resins B.V., etc.), etc. The amount of the photoinitiator is arbitrarily adjusted within the range that can maintain the curability of the resin composition 5.

[0046] The chain transfer agent is for generating a chain transfer reaction. In this example, the chain transfer agent functions to cut off the reaction between (meth)acrylates and reduces the apparent molecular weight of (meth)acrylates. To bond (meth)acrylates of small units together, the adhesive force (tack force) of the cured resin composition 5 can be improved. As a result, the resin layer 50 formed by the resin composition 5 and the surface protection sheet 20 can be firmly integrated, creating a situation where they are difficult to peel from each other.

[0047] As an example of the blending ratio of the resin composition 5, for example, it can be as follows. (Meth)acrylate is 80% by mass or more and 99.4% by mass or less The chain transfer agent is 0.5% by mass or more and 15% by mass or less The photopolymerization initiator is 0.1% by mass or more and 5% by mass or less

[0048] Regarding (meth)acrylate, for example, a (meth)acrylate having a urethane bond and a (meth)acrylate not having a urethane bond in a mass% ratio of 1:1 can be used.

[0049] Furthermore, the content of the chain transfer agent in the resin composition 5 is preferably 0.4 to 5 times that of the photopolymerization initiator. This is because if the content of the photopolymerization initiator is too large, the effect of containing the chain transfer agent (improvement of adhesive strength) will be reduced. On the other hand, if the content of the chain transfer agent is too large, many chain transfer reactions will occur and it will be difficult to cure by ultraviolet rays. This is to prevent this.

[0050] <Thinning process step> As shown in FIGS. 9(A) and (B), this is a step of holding the protective layer 6 by the holding table 70 and processing and thinning the back surface 10b side of the wafer 10.

[0051] Specifically, with the protective layer 6 of the wafer 10 on the lower side, the wafer 10 is placed on the suction holding surface 72 of the holding table 70 of the grinding device, and the back surface 10b of the wafer 10 is exposed. While rotating the grinding wheel 74 having the grinding wheel 74a and feeding the grinding wheel 74 downward for grinding, the back surface 10b of the wafer 10 is ground by the grinding wheel 74a until it reaches a predetermined thickness. At this time, the holding table 70 is also rotated, and the wafer 10 is ground while rotating.

[0052] In this thinning step, since the lower surface 41a of the film 41 is flat, the back surface 10b of the wafer 10 placed on the flat suction holding surface 72 is also flat, and the upper surface height of the wafer 10 (the height of the back surface 10b) can be made uniform. As a result, the wafer 10 can be thinned uniformly, and the thickness of the wafer 10 can be finished uniformly.

[0053] In addition to thinning by grinding using the grinding wheel 74a, it may also be thinned by polishing using a polishing pad or cutting using a cutting tool.

[0054] <Peeling step> As shown in FIGS. 10(A) and 10(B), this is a step of peeling the protective layer 6 from the surface 10a of the wafer 10.

[0055] Specifically, as shown in FIGS. 10(A) and 10(B), the wafer 10 is removed from the holding table 70 (FIG. 9(B)) of the grinding apparatus, turned over, and the back surface 10b of the wafer 10 is placed on the suction holding surface 82 of the holding table 80 of the peeling apparatus to expose the protective layer 6. The suction holding surface 82 of the holding table 80 communicates with the suction source 83, and the back surface 10b of the wafer 10 is suction-held by the negative pressure generated on the suction holding surface 82.

[0056] Next, a peeling tape 84 is attached to the protective layer 6, and the protective layer 6 is peeled from the wafer 10 by pulling the peeling tape 84 with the clamp 81 constituting the peeling apparatus.

[0057] As described above, the protective layer 6 formed on the surface 10a of the wafer 10 as shown in FIG. 11(A) is peeled off, resulting in the state shown in FIG. 11(B). At this time, since the surface 10a of the wafer 10 is covered with the surface protection sheet 20, the resin composition 5 (resin layer 50) does not remain on the surface 10a of the wafer 10, and since there is no adhesive layer on the surface protection sheet 20, the surface protection sheet 20 can be easily peeled off, preventing foreign matter from remaining on the surface 10a of the wafer 10.

[0058] As described above, in the present invention, a protective layer is formed by a surface protective sheet that is adhered to the surface of a workpiece and a resin layer laminated on the surface protective sheet. The resin layer is formed from a resin composition containing a (meth)acrylate, a chain transfer agent, and a photopolymerization initiator. As a result, even if irregularities are formed on the surface of the surface protective sheet, the resin layer can absorb the irregularities, allowing the surface of the protective layer to be formed flat. Furthermore, the surface protective sheet and the resin layer are firmly integrated, allowing them to be peeled off from the wafer as a unit without separation. [Explanation of symbols]

[0059] 5 Resin composition 6 Protective layer 10 wafers 10a surface 10b back side 12th Street 14 devices 16 Bump 20 Surface protection sheet 20b back side 24 Annular Frame 26 Glue layer 30 Vacuum Chamber 32 Heating Table 34 Vacuum source 40 stages 40a Support surface 41 Film 46 Light irradiator 46a light source 50 resin layer 60 Wafer Holding Unit 62 Suction holding surface 70 Holding Table 72 Suction holding surface 74 Grinding Wheel 74a Grinding wheel 80 Holding Table 81 Clamp 82 Suction holding surface 84 Peel Tape

Claims

1. A resin composition for forming a resin layer on a workpiece through a surface protection sheet that does not adhere to the surface of the workpiece, comprising: (meth)acrylate, a chain transfer agent, a photoinitiator, and the chain transfer agent functions to cut off the reaction between (meth)acrylates, reduce the molecular weight of (meth)acrylate, and enable integration of the resin layer formed by the resin composition and the surface protection sheet.

2. The content of the chain transfer agent in the resin composition is 0.4 to, 5 times that of the photoinitiator. The resin composition according to Claim 1, characterized in that.

3. The chain transfer agent is a thiol. The resin composition according to Claim 1 or Claim 2, characterized in that.

4. A method for protecting one side surface of a workpiece using the resin composition according to any one of Claims 1 to 3, comprising: a surface protection sheet adhesion step of adhering the surface protection sheet to the surface of the workpiece; and a protective layer formation step of supplying the resin composition onto the surface protection sheet, irradiating the resin composition with light to cure it and form a resin layer, and forming a protective layer having at least the surface protection sheet and the resin layer on the surface of the workpiece.

5. A method for processing a workpiece using the resin composition according to any one of Claims 1 to 3, comprising: a surface protection sheet adhesion step of adhering the surface protection sheet to the surface of the workpiece; a protective layer formation step of supplying the resin composition onto the surface protection sheet, irradiating the resin composition with light to cure it and form a resin layer, and forming a protective layer having at least the surface protection sheet and the resin layer on the surface of the workpiece; a thinning step of holding the protective layer side with a holding table and thinning the back side of the workpiece; and a peeling step of peeling the protective layer from the surface of the workpiece. A method for processing a workpiece comprising the above steps.

6. A protective layer of a workpiece, comprising: a surface protection sheet that does not adhere to the surface of the workpiece; and a resin layer formed on the surface of the surface protection sheet opposite to the workpiece, wherein the resin layer is formed from a resin composition containing (meth)acrylate, a chain transfer agent, a photoinitiator, and the resin layer and the surface protection sheet are integrated.

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