Method for protecting workpiece and method for machining workpiece

Abstract

To provide a method for protecting a workpiece 1, which can reliably protect the workpiece with a surface protection sheet 10, while preventing adhesion of an antistatic agent to a circuit surface, and can prevent static electricity.SOLUTION: A method for protecting a workpiece includes a step of attaching a surface protection sheet 10 to the surface of a workpiece 1, and the surface of the workpiece 1 has an inner periphery on which a plurality of circuits 2 are formed and an outer periphery surrounding the inner periphery and having no circuits, a convex pattern 4 containing an antistatic agent is formed on at least the outer periphery, and the surface protection sheet 10 is attached to the surface on which the convex pattern 4 is formed.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for protecting and machining a workpiece, and more particularly to a method for protecting the workpiece while preventing an antistatic agent from adhering to a circuit formed on the surface of the workpiece, and for suppressing static electricity generated when a member used for protecting the workpiece is peeled off. [Background technology]

[0002] As semiconductor devices become more and more integrated and miniaturized, there is a continuing demand for thinner semiconductor chips. In order to make chips smaller and thinner, it is common to thin the wafer by grinding the backside of the wafer.

[0003] During back grinding of the wafer, a surface protection sheet called backgrind tape is affixed to the wafer surface to protect the circuits and chips arranged on the wafer surface and to hold the wafer.

[0004] Patent Document 1 discloses an adhesive tape for semiconductor wafer processing that has good conformability to the surface of semiconductor wafers having steps and protrusions and can be peeled off without damaging the semiconductor wafer or leaving any adhesive residue.

[0005] Adhesive tapes for semiconductor wafer processing are peeled off from the semiconductor wafer, which is the adherend, after the completion of a predetermined processing step, and static electricity may be generated at this time. There is concern that static electricity may destroy circuits or contaminate the circuits due to the adhesion of foreign matter such as dust. In order to remove static electricity, static electricity removal devices such as ionizers have been introduced. However, the reality is that sufficient antistatic effects are not obtained. Therefore, making the adhesive tape itself antistatic has been considered, and it has also been proposed to incorporate an antistatic agent into the adhesive layer of the adhesive tape (Patent Documents 2 to 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-171896 A [Patent Document 2] JP 2013-209559 A [Patent Document 3] JP 2014-185349 A [Patent Document 4] JP 2013-036046 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the protection method using the adhesive tape for semiconductor wafer processing as in Patent Documents 1 to 4, it is unavoidable that the adhesive comes into contact with the circuit surface. In particular, when the circuit surface has steps or protrusions, in order to eliminate the height difference in the thickness direction, the adhesive layer is pressed against the circuit surface, and the steps and protrusions are sometimes embedded in the adhesive layer, and the adhesive layer is pressed against the circuit surface. When an adhesive tape for semiconductor wafer processing containing an antistatic agent is used, the antistatic agent may remain on the semiconductor wafer and adhere to the circuit surface. Since the antistatic agent is conductive, if it adheres to the circuit surface, it may cause a short circuit. For this reason, a method for protecting a workpiece that can prevent the antistatic agent from adhering to the circuit surface while reliably protecting the workpiece with a surface protection sheet and can prevent static electricity has been demanded. [Means for solving the problem]

[0008] In response to these problems, the inventors came up with the idea of ​​forming a convex pattern containing an antistatic agent on the outer periphery of a workpiece on which a circuit is formed, and then attaching a protective sheet on top of that, thereby reliably protecting the circuit surface and preventing static electricity without the antistatic agent adhering to the circuit surface, and thus completed the present invention.

[0009] The aspects of the present invention are as follows. (1) A method for protecting a workpiece, comprising a step of attaching a surface protection sheet to a surface of the workpiece, The surface of the workpiece has an inner periphery on which a plurality of circuits are formed and an outer periphery surrounding the inner periphery and having no circuits; forming a convex pattern containing an antistatic agent on at least the outer periphery; A method for protecting a workpiece, comprising attaching a surface protection sheet to the surface on which the convex pattern is formed.

[0010] (2) A method for protecting a workpiece according to (1), in which the convex pattern is also formed between the circuits on the inner circumference.

[0011] (3) The method for protecting a workpiece according to (1), wherein the convex pattern is composed of a resin composition containing an antistatic agent and a resin component.

[0012] (4) The method for protecting a workpiece according to (1), wherein the surface protection sheet does not contain an antistatic agent.

[0013] (5) Protecting the workpiece by any one of the methods described in (1) to (4), Grind the back side of the workpiece while protecting it. The surface protection sheet is peeled off, and the convex pattern is removed together with the surface protection sheet.

[0014] (6) A step of forming a groove on the surface of the workpiece before the step of forming a convex pattern on the surface of the workpiece, A method for processing a workpiece according to (5), wherein in the step of grinding the back surface of the workpiece, the workpiece is diced into a plurality of workpiece pieces starting from the grooves.

[0015] (7) A process for forming a modified region inside the workpiece before the process for grinding the back surface of the workpiece, A method for processing a workpiece according to (5), wherein in the step of grinding the back surface of the workpiece, the workpiece is diced into a plurality of workpiece pieces starting from modified regions.

[0016] (8) A resin composition used to provide a convex pattern in the method for protecting a workpiece according to any one of (1) to (4), the resin composition comprising an antistatic agent and a resin component. Effect of the Invention

[0017] According to the present invention, the circuit surface of the workpiece can be reliably protected and prevented from being charged, and the adhesion of the antistatic agent to the circuit surface can be prevented. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a plan view of the circuit surface. [Diagram 2] FIG. 2 is a plan view showing an example in which a convex pattern is formed on the outer periphery of the circuit surface. [Diagram 3] FIG. 3 is a plan view showing another example of a convex pattern formed on the circuit surface. [Figure 4] FIG. 4 is a plan view showing another example of a convex pattern formed on the circuit surface. [Diagram 5] FIG. 5 is a schematic cross-sectional view taken along line AA in FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a state in which a surface protection sheet is attached onto the convex pattern. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a state in which the back surface of a workpiece is being machined (ground) while the workpiece is being protected by the workpiece protection method of the present invention. [Figure 8] FIG. 8 is a schematic cross-sectional view showing a state in which the surface protection sheet is being peeled off after the rear surface of the workpiece has been processed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings based on specific embodiments. First, the main terms used in this specification will be explained.

[0020] The work refers to a plate-like body to which a surface protection sheet is attached and then cut into individual pieces. Examples of the work include a circular wafer (including a case having an orientation flat), a rectangular panel level package, and a strip (rectangular substrate) sealed with molded resin. Among them, a wafer having a circuit is preferable from the viewpoint of easily obtaining the effect of the present invention. The wafer may be, for example, a semiconductor wafer such as a silicon wafer, a gallium arsenide wafer, a silicon carbide wafer, a gallium nitride wafer, or an indium phosphide wafer, or an insulating wafer such as a glass wafer, a lithium tantalate wafer, or a lithium niobate wafer, or may be a reconstructed wafer made of a resin and a semiconductor used for producing a fan-out package or the like. From the viewpoint of easily obtaining the effect of the present invention, the wafer is preferably a semiconductor wafer or an insulating wafer, and more preferably a semiconductor wafer.

[0021] Singulation of a work refers to dividing the work into individual circuits to obtain individual work pieces. For example, if the work is a wafer, the individual work pieces are chips, and if the work is a panel level package or a strip (rectangular substrate) sealed with molded resin, the individual work pieces are semiconductor packages.

[0022] The "front surface" of a workpiece refers to the surface on which a circuit is formed, and the "back surface" of a workpiece refers to the surface on which no circuit or the like is formed. The circuit is not particularly limited, but the method of the present invention is particularly preferably used for logic ICs and memories, in which adhesion of an antistatic agent to the circuit surface is strongly avoided.

[0023] DBG (Dicing Before Grinding) is a method in which a groove of a specified depth is formed on the front side of a wafer, and then the wafer is ground from the back side to separate the wafer by grinding. The grooves formed on the front side of the wafer are formed by methods such as blade dicing, laser dicing, and plasma dicing.

[0024] Laser dicing before grinding (LDBG) is a modified form of DBG in which a modified region is created inside the wafer using a laser, and the wafer is diced into individual pieces using stress generated during grinding of the back surface of the wafer.

[0025] A "group of individual workpieces" refers to a plurality of individual workpieces held on a surface protection sheet after the workpiece is singulated. These individual workpieces, as a whole, form a shape similar to that of the workpiece. A "group of chips" refers to a plurality of chips held on a surface protection sheet after the wafer as the workpiece is singulated. These chips, as a whole, form a shape similar to that of the wafer.

[0026] "(Meth)acrylate" is used as the term to refer to both "acrylate" and "methacrylate," and similar terms.

[0027] The "energy rays" refer to ultraviolet rays, electron beams, etc., and are preferably ultraviolet rays.

[0028] Unless otherwise specified, the "weight average molecular weight" is a polystyrene equivalent value measured by gel permeation chromatography (GPC). Measurements by such a method are performed, for example, using a high-speed GPC device "HLC-8120GPC" manufactured by Tosoh Corporation with a high-speed column "TSK guard column H XL -H", "TSK Gel GMH XL ", "TSK Gel G2000 H XL (All of the above are manufactured by Tosoh Corporation) connected in the above order, the column temperature was 40° C., the liquid flow rate was 1.0 mL / min, and the detector was a differential refractometer.

[0029] The release sheet is a sheet that supports the pressure-sensitive adhesive layer in a releasable manner. The term "sheet" is not limited to a specific thickness, and is used to include a film.

[0030] The mass ratios in the explanations of the compositions such as the pressure sensitive adhesive and the convex pattern forming composition are based on the active ingredients (solid content), and do not include the solvent unless otherwise specified.

[0031] As an embodiment of the present invention, as one of the processing of a workpiece having a circuit or the like formed on one surface (front surface) and no circuit or the like formed on the other surface (back surface), grinding the back surface of the workpiece is exemplified. By grinding the back surface, the thickness of the workpiece can be reduced, and by using the above DBG and LDBG, the thickness of the workpiece obtained by dividing the workpiece can be reduced.

[0032] Before grinding the backside of a workpiece, a surface protection sheet is attached to the surface of the workpiece in order to protect the surface of the workpiece. By attaching the surface protection sheet to the surface of the workpiece, contamination of circuits, etc. due to intrusion of abrasives, cooling water, etc. into the workpiece surface during backside grinding, and damage to circuits, etc. due to the force applied during backside grinding can be prevented.

[0033] The workpiece protected by the method according to this embodiment has, on its surface, an inner periphery on which a plurality of circuits are formed, and an outer periphery surrounding the inner periphery and having no circuits.

[0034] In the following description, reference will be made to the drawings, in which the relative size of the circuits to the workpiece (wafer) and the circuit spacing are greatly exaggerated.

[0035] Figure 1 shows a plan view from the surface side of the workpiece. On the surface of the workpiece 1, multiple circuits 2 are formed, surrounded by cutting lines 3 shown by dashed lines. Ultimately, this workpiece will be cut along the cutting lines 3 shown by dashed lines for each circuit, and divided into multiple element pieces (chips).

[0036] The workpiece protection method according to this embodiment includes the following steps 1 and 2. Step 1: Forming a convex pattern containing an antistatic agent on the outer periphery of the workpiece surface Step 2: A process of attaching a surface protection sheet to the surface with the convex pattern.

[0037] In the following, a method for protecting a workpiece will be described assuming that the workpiece is a wafer.

[0038] (Process 1) In step 1, a convex pattern 4 is formed on the outer periphery of the wafer surface. The outer periphery is the edge of the wafer, and refers to the area where no circuits are formed. Generally, the outer periphery without circuits is an area about 10 mm from the edge of the wafer.

[0039] (Convex pattern 4) The convex pattern 4 is a pattern formed on the surface of the wafer 1 so as to protrude in the thickness direction of the wafer 1. Since such a convex pattern 4 is formed on the outer periphery of the surface of the wafer, by attaching the surface protective sheet 10 to the surface of the wafer 1, it is possible to prevent grinding debris from entering the circuit surface.

[0040] In this embodiment, it is preferable to set the height Hp of the convex pattern 4 according to the height Hc of the circuit 2 on the surface of the wafer. The height Hc of the circuit 2 refers to the height of the highest part of the circuit with respect to the flat portion between the circuits on the surface of the wafer, as shown in Fig. 5. The height Hp of the convex pattern 4 refers to the height of the highest part of the convex pattern with respect to the flat portion between the circuits on the surface of the wafer.

[0041] In this embodiment, the height Hp of the convex pattern is preferably 1 to 2000 μm.

[0042] The material constituting the raised pattern 4 may be any material that contains an antistatic agent and can stably hold the surface protection sheet 10 attached onto the raised pattern.

[0043] The antistatic agent in the present embodiment is not particularly limited, and known ones can be used. Examples of the antistatic agent include ionic liquids, low molecular weight antistatic agents, and polymeric antistatic agents, but ionic liquids are preferably used because they are easily mixed with the resin described below and have excellent antistatic properties.

[0044] The ionic liquid in this embodiment is a type of salt containing a cationic (positive ion) compound and an anionic (negative ion) compound, and refers to a salt that is in a liquid state at or below 100° C. Ionic liquids exhibit high electrical conductivity and can therefore exhibit excellent antistatic properties.

[0045] Examples of the cations constituting the ionic liquid include triethylpentylammonium, cyclohexyltrimethylammonium, methyltri-n-octylammonium, tetrabutylammonium, tetrabutylphosphonium, tributylhexadecylphosphonium, tributyl(2-methoxyethyl)phosphonium, tributylmethylammonium, tributylmethylphosphonium, triethylsulfonium, trimethylpropylammonium, 1-butyl-1-methylpiperidinium, hydroxyethylpiperazine, 2-methylpiperazine, N-ethylmorpholine, N-N-dimethylethanolamine, N-N-dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine, N-ethylethanolamine, N-ethyldiethanolamine, N-(β-aminoethyl)ethanolamine, Nn-butyldi ... amine, Nt-butyldiethanolamine, N,N-diethylisopropanolamine, 1-butyl-2,3-dimethylimidazolium, 1-butyl-3-methylimidazolium, 1,3-dimethylimidazolium, 1,2-dimethyl-3-propylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-methyl-3-n-octylimidazolium, 1-methyl-3-propylimidazolium, 1-butyl-4-methylpyridinium, 1-butyl-3-methylpyridinium, 1-butylpyridinium, 1-ethyl-3-(hydroxymethyl)pyridinium, 1-ethyl-3-methylpyridinium, 1-ethylpyridinium, 1-butyl-1-methylpyrrolidinium, 1-methyl-1-propylpyrrolidinium, and the like.

[0046] The cation is not limited in any way as long as it can form an ionic liquid, and cations other than those exemplified above can also be used.

[0047] Similarly to the above cations, the anions constituting the ionic liquid are not limited in any way, and anions other than those exemplified below can also be used.

[0048] The anion that constitutes the ionic liquid is, for example, AlCl4 - , Al2Cl7 - , BF4 - , PF6 - , F(HF)n - , CF3COO - , CH3CH2OSO3 - , CF3SO3 - (TfO), (CF3SO2)2N - (TFSI), (CF3SO2)3C - (TFSM), HN(Tf)2 - , NO3 - , (NC)2N - , CH3COO - , Br - , Cl - , I - , (CH3O)2OPO - Further examples include sulfonic acid type (sulfonate type) anions such as linear alkylbenzenesulfonic acid, dialkyl succinate sulfonic acid, α-sulfofatty acid methyl ester, α-olefinsulfonic acid, and alkanesulfonic acid; fatty acid type anions such as higher fatty acids; sulfate type anions such as alkyl sulfate ester, glycol ether sulfate ester, and alkyl ether sulfate ester; and phosphate type anions such as (mono)alkyl phosphate ester.

[0049] Examples of ionic liquids include ionic liquids containing N-ethylethanolamine and alkylbenzenesulfonic acid, ionic liquids containing N-ethylethanolamine and glycol ether sulfate, and ionic liquids containing N-ethylethanolamine and dialkylsuccinatesulfonic acid. The ionic liquid may be used alone or in combination of two or more. The ionic liquid may contain two or more cations and / or two or more anions.

[0050] Examples of ionic liquid products include AS100, AS200, AS300, and AS400 from Nippon Nyukazai Co., Ltd., and the IL-P series, IL-A series, IL-C series, IL-IM series, and IL-AP series from Koei Chemical Co., Ltd.

[0051] Furthermore, the ionic liquid may have a reactive site. Examples of ionic liquids having reactive sites include RE3000MA, JI62J01, and JI62G01 from Nippon Nyukazai Co., Ltd., the IL-MA series and IL-S series from Koei Chemical Industry Co., Ltd., and FC-4400 from 3M Japan Limited.

[0052] Examples of the polymer-type antistatic agent include copolymers having a polyether unit, such as polyether ester amide and polyether polyolefin block copolymer.

[0053] In this embodiment, from the viewpoint of facilitating the formation of a convex pattern, the convex pattern forming composition constituting the convex pattern preferably contains a resin component. The resin component is preferably an adhesive resin that adheres closely to the wafer surface. Examples of the adhesive resin include acrylic resin, silicone resin, urethane resin, epoxy resin, phenol resin, urea resin, alkyd resin, vinyl acetate resin, vinyl chloride resin, amide resin, imide resin, chloroprene rubber, nitrile rubber, styrene butadiene rubber, nylon, polycarbonate, polypropylene, and the like.

[0054] In addition, the adhesive resin is preferably curable, since it can be easily formed into a desired shape before curing, and can be easily made into a hard material after curing to a degree that can prevent abrasives, cooling water, etc. from penetrating into the circuits of the wafer during back grinding.

[0055] Examples of the curable resin include thermosetting resins and energy ray curable resins. From the viewpoint of removing the convex pattern from the wafer surface after back grinding, energy ray curable resins are preferred.

[0056] The convex pattern forming composition contains the above-mentioned antistatic agent and a resin component. The proportion of the antistatic agent in the convex pattern forming composition varies depending on the antistatic agent used, but generally, the antistatic agent is preferably used in a proportion of 1 to 30 parts by mass, more preferably 1.5 to 25 parts by mass, and particularly preferably 3 to 20 parts by mass, relative to 100 parts by mass of the total amount of the convex pattern forming composition. If the blending proportion of the antistatic agent is too low, the required antistatic properties may not be obtained, and if it is too high, the shape retention of the convex pattern may decrease.

[0057] The convex pattern forming composition may contain, in addition to the antistatic agent and the resin component, general components that are blended in adhesives. When the resin component is an energy ray curable resin, it is preferable to contain a photopolymerization initiator, and when the resin component is a thermosetting resin, it is preferable to contain a thermal polymerization initiator. In addition, it may contain an acrylic or polyester adhesive, or may contain a crosslinking agent.

[0058] The convex pattern 4 is formed on the outer periphery of the surface of the wafer as shown in FIG. 2. Also, as shown in FIG. 3 and FIG. 4, in addition to the outer periphery, the convex pattern 4 may be formed between the circuits 2 on the inner periphery of the wafer surface. The convex pattern 4 may be formed so as to cover the entire surface other than the circuits 2 as shown in FIG. 3. Also, as shown in FIG. 4, the convex pattern 4 may be formed so as to cover a part of the surface other than the circuits 2. It is preferable that the convex pattern 4 is formed continuously and without interruption. If the convex pattern 4 is formed continuously, the convex pattern can be peeled off continuously when removing the convex pattern. On the other hand, if the convex pattern is discontinuous, a part of the convex pattern may remain on the wafer surface when it is removed.

[0059] The means for forming the convex pattern 4 may be determined according to the material for forming the convex pattern 4. For example, when forming the convex pattern using a curable resin, a means for applying a liquid resin before curing can be used. Specifically, a coating device such as a die coater, curtain coater, spray coater, slit coater, or knife coater; a printing device such as a screen printer or inkjet printer; or a dropping device such as a dispenser can be used.

[0060] (Process 2) As shown in FIG. 6, after the convex pattern 4 is formed, a surface protection sheet 10 is attached to the top of the convex pattern 4. (Surface protection sheet 10) The surface protection sheet 10 may be configured to protect the circuits and the like on the wafer surface. If the surface protection sheet 10 has good adhesion to the material of the convex pattern, it may be a so-called adhesive sheet having a base material and an adhesive layer, or it may be a resin film. The resin film is a thin-layered resin molding that does not have an adhesive layer, and may be a single layer or a laminate. Such a resin film generally does not have adhesive properties, but if it is a resin film that has high affinity with the material of the convex pattern, the resin film can be attached to the convex pattern by applying an appropriate pressure and heating as necessary.

[0061] When the surface protection sheet 10 is an adhesive sheet having a substrate and an adhesive layer, the circuit 2 is reliably protected by attaching the adhesive layer to the tops of the convex patterns 4. When the surface protection sheet 10 is an adhesive sheet, an intermediate layer may be provided between the substrate and the adhesive layer. Furthermore, another layer may be formed between the intermediate layer and the adhesive layer.

[0062] Examples of the material of the substrate of the adhesive sheet include polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, fully aromatic polyester, polyamide, polycarbonate, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, biaxially oriented polypropylene, and the like. Among these, polyester is preferred, and polyethylene terephthalate is more preferred. The composition of the adhesive layer is not limited as long as it has enough adhesiveness to be attached to the top of the convex pattern. In this embodiment, the adhesive layer is preferably composed of, for example, an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, and the like. In addition, the adhesive layer is preferably formed from an energy ray curable acrylic adhesive. As the acrylic adhesive, it is preferable to use an acrylic polymer. The energy ray curable acrylic adhesive may be an acrylic adhesive composed of an acrylic polymer having energy ray curability, or may be an acrylic adhesive containing an acrylic polymer having energy ray curability and / or an acrylic polymer not having energy ray curability and an energy ray curable compound such as an oligomer having an energy ray curable group. In this embodiment, an acrylic adhesive composed of an acrylic polymer having energy ray curability is preferred. One surface of the substrate may be subjected to an adhesion treatment such as a corona treatment in order to improve adhesion with the adhesive layer.

[0063] The thickness of the adhesive layer is not particularly limited as long as it is thick enough to be adhered to the top of the convex pattern. In this embodiment, the thickness of the adhesive layer is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less. The thickness of the adhesive layer means the thickness of the entire adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers means the total thickness of all layers constituting the adhesive layer.

[0064] The antistatic property can be further improved by including an antistatic agent in the substrate or adhesive layer of the pressure-sensitive adhesive sheet. However, in the present invention, since the convex pattern includes an antistatic agent, sufficient antistatic property can be obtained even if the pressure-sensitive adhesive sheet does not include an antistatic agent. By not including an antistatic agent in the substrate or adhesive layer, adhesion of the antistatic agent to the object to be protected can be more reliably prevented.

[0065] When the surface protective sheet is a resin film, it may be made of a single layer film made of one resin film, or may be made of a multilayer film in which a plurality of resin films are laminated.

[0066] In this embodiment, the material of the resin film is the same as the material of the base material of the pressure-sensitive adhesive sheet.

[0067] The thickness of the resin film affects the rigidity of the surface protection sheet, and may be set according to the material of the resin film. In this embodiment, the thickness of the resin film is preferably 25 μm or more and 200 μm or less, more preferably 35 μm or more and 150 μm or less, and even more preferably 40 μm or more and 150 μm or less. (How to protect the work) In this embodiment, as shown in FIG. 6, a surface protection sheet 10 is attached to the top of the convex pattern 4 to protect the workpiece. The surface protection sheet 10 may be cut to the same shape as the workpiece in advance, or the surface protection sheet 10 may be cut to match the outer peripheral shape of the workpiece after the surface protection sheet 10 is attached. When the workpiece is a semiconductor wafer having a circuit, each circuit 2 is surrounded by the convex pattern 4 and is covered with the surface protection sheet 10. According to this embodiment, since it is not necessary to strongly press the surface protection sheet 10 against the circuit surface, adhesion of the antistatic agent to the circuit surface can be prevented. As shown in FIG. 6, even if the circuit surface and the surface protection sheet are in contact with each other, adhesion of the antistatic agent to the circuit surface can be reliably prevented by using a sheet that does not contain an antistatic agent as the surface protection sheet. In this state, even if the workpiece is transported, stored, or processed, the circuit will not be damaged.

[0068] (Workpiece processing method) According to this embodiment, the workpiece can be processed while being protected. In the following, an example will be described in which the workpiece is a semiconductor wafer having a circuit on its surface, and the processing is grinding of the back surface of the wafer.

[0069] In the workpiece processing method of the present invention, the wafer with the surface protection sheet attached is placed on a chuck table (not shown) with the surface protection sheet 10 side. The chuck table has, for example, a porous holding surface, and the surface protection sheet is adsorbed and fixed to the chuck table by suction from the holding surface.

[0070] As shown in Fig. 7, after the wafer is fixed to the chuck table, the back surface of the wafer is ground, for example, by a grinding wheel 5 or the like. During back grinding of the wafer, water is sprayed onto the grinding surface while grinding in order to remove heat and grinding debris generated during grinding. However, according to the method for protecting a workpiece of the present invention, the surface of the workpiece is protected by the convex pattern and the surface protection sheet, so that cleaning water and the like does not penetrate during grinding and the circuits of the wafer are not contaminated. The thickness of the wafer after back grinding is, for example, about 25 μm to 600 μm.

[0071] After grinding, the suction is released and the wafer and surface protection sheet are released from the chuck table.

[0072] (Peeling process) When peeling off the surface protection sheet 10, as shown in Fig. 8, a pick-up tape 12 is attached to the back side of the workpiece 1 after the backside grinding, and the position and direction are adjusted so that the workpiece 1 can be picked up. At this time, a ring frame 14 arranged on the outer periphery of the workpiece 1 is also attached to the pick-up tape 12, and the outer periphery of the pick-up tape 12 is fixed to the ring frame 14. The workpiece 1 and the ring frame may be attached to the pick-up tape 12 at the same time, or may be attached at different times. Next, the surface protection sheet 10 is peeled off from the workpiece 1 held on the pick-up tape 12.

[0073] In this embodiment, the surface protection sheet 10 is peeled off from the work 1 after the back grinding. At this time, the convex pattern 4 is peeled off together with the surface protection sheet 10. When an adhesive sheet is used as the surface protection sheet 10, the convex pattern 4 adheres to the adhesive sheet, so that the surface protection sheet 10 and the convex pattern 4 can be peeled off in an integrated state. In addition, when a resin film having a high affinity with the material of the convex pattern 4 is used as the surface protection sheet 10, the surface protection sheet 10 and the convex pattern 4 can be peeled off in an integrated state. For example, when the resin component of the convex pattern 4 and the resin component of the resin film are formed from the same or similar resin, the resin film and the convex pattern can be peeled off in an integrated state. When the surface protection sheet 10 is peeled off, static electricity may be generated, but in this embodiment, since an antistatic agent is blended in the convex pattern 4, even if static electricity is generated, it is removed and does not adversely affect the circuit.

[0074] (DBG or LDBG) When the workpiece processing method according to this embodiment is applied to DBG or LDBG, a step of forming a groove on the surface of the wafer (step 3A: DBG) or a step of forming a modified region inside the wafer (step 3B: LDBG) is included in addition to the above steps 1 and 2. The groove and modified region are formed so as to follow the cutting lines 3 along which the wafer is divided into individual pieces in the above-mentioned back grinding.

[0075] When grooves are formed on the surface of the wafer by dicing or the like, steps 1 and 2 are performed after step 3A. That is, in step 1, a convex pattern is formed so as to cover the grooves formed in step 3A described later. If the viscosity of the resin forming the convex pattern is too low, the resin will penetrate between the grooves and bond the chips together after division, making it impossible to pick up the chips. For this reason, when the workpiece processing method according to this embodiment is applied to DBG, it is preferable to set the viscosity of the resin material forming the convex pattern to be high.

[0076] The grooves formed in step 3A are shallower than the thickness of the wafer. The grooves can be formed by dicing using a conventionally known dicing device. The wafer is divided into a plurality of chips along the grooves by the stress applied during back grinding.

[0077] On the other hand, when forming a modified region on the wafer, steps 1 and 2 may be performed before or after step 3 B. In this embodiment, when forming a modified region on the wafer, steps 1 and 2 are preferably performed before step 3 B.

[0078] In addition, the modified region is a brittle portion of the wafer, and is the starting point for the wafer to be destroyed and diced into chips when the wafer becomes thinner due to grinding in the grinding process or when stress is applied during backside grinding.

[0079] The modified region is formed inside the wafer by irradiating the laser focused on the inside of the wafer. The laser may be irradiated from the front side or the back side of the wafer. In the embodiment in which the modified region is formed, when the step 3B is performed after the step 1 and the laser is irradiated from the front side of the wafer, the laser is irradiated to the wafer through the surface protection sheet.

[0080] In DBG, back grinding is performed to thin the wafer at least to the bottom of the groove. This back grinding turns the groove into a cut that penetrates the wafer, and the wafer is divided by the cut and singulated into individual chips, resulting in a group of chips aligned on the surface protection sheet, and a group of singulated workpieces is obtained on the surface protection sheet.

[0081] In LDBG, the grinding surface (wafer back surface) may reach the modified region by grinding, but it does not have to reach the modified region strictly. In other words, it is sufficient to grind to a position close to the modified region so that the wafer is broken and singulated into chips starting from the modified region. As a result, the workpiece is singulated into individual chips, resulting in a group of chips aligned on the surface protection sheet, and a group of workpiece singulations is obtained on the surface protection sheet. In addition, the actual singulation of the chips may be performed by applying a pick-up tape and then stretching the pick-up tape.

[0082] After the back surface grinding is completed, dry polishing may be performed prior to picking up the chips.

[0083] The shape of the individualized chips (workpiece individualized products) may be square or elongated, such as rectangular. The thickness of the individualized chips is not particularly limited, but is preferably about 5 to 100 μm, and more preferably 10 to 45 μm. LDBG makes it easy to make the thickness of the individualized chips 50 μm or less, and more preferably 10 to 45 μm. The size of the individualized chips is not particularly limited, but is preferably 600 mm or less. 2 Less than 400mm, more preferably 2 Less than 120mm, more preferably 2 is less than.

[0084] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and may be modified in various aspects within the scope of the present invention. EXAMPLES

[0085] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0086] The evaluation methods in the present examples are as follows.

[0087] (Measurement of charge amount) A convex pattern forming composition was applied to the outer periphery of a silicon wafer (thickness: 760 μm, diameter: 12 inches) using a dispenser (Musashi Engineering, Shotmaster 350DS) to a thickness of 30 μm and a width of 2 mm, and then irradiated with ultraviolet light (illuminance: 230 mW / cm 2 , irradiation amount 200mJ / cm 2 ) to produce a wafer having a convex pattern on the outer periphery. A surface protection sheet was then attached to the top of the convex pattern on the wafer using a tape laminator RAD-3510F / 12 manufactured by Lintec Corporation. In this state, the back side of the silicon wafer was ground until the thickness of the silicon wafer was 300 μm. Thereafter, ultraviolet light was irradiated (illuminance 230 mW / cm) using a wafer mounter RAD-2700F / 12 manufactured by Lintec Corporation. 2 , irradiation amount 1200mJ / cm 2 ) was carried out to cure the adhesive layer of the surface protection sheet, and the surface protection sheet was peeled off at a speed of 10 mm / s, and the convex pattern was peeled off along with the surface protection sheet. The amount of charge on the wafer during peeling was measured using a PFM-711A (Prostat Corporation). A charge of 3000 V or less was judged as good, and a charge of more than 3000 V was judged as bad.

[0088] (Measurement of surface resistivity) The energy ray curable convex pattern forming composition prepared as described below was applied to a PET-based release film to a thickness of 100 μm to form an energy ray curable resin layer. Next, a PET film was attached onto the energy ray curable resin layer thus formed. This blocked the energy ray curable resin layer from oxygen. Next, a high pressure mercury lamp was used to illuminate the resin layer with an illumination intensity of 230 mW / cm. 2 , irradiation amount 200mJ / cm 2 The energy ray curable resin layer was cured by irradiating ultraviolet rays under the conditions of 10 cm×10 cm to obtain a cured product. The laminated structure of PET release film / cured product / PET film was cut to a size of 10 cm×10 cm, the PET release film was removed, and the surface resistivity of the cured product was measured using an Advantest surface resistivity meter R8252 under the conditions of 23° C., 50% RH, and an applied voltage of 100 V in accordance with JIS K 7194.

[0089] (1. Creating a surface protection sheet) 80 parts by mass of 2-ethylhexyl acrylate (2EHA) and 20 parts by mass of 2-hydroxyethyl acrylate (HEA) were copolymerized to obtain an acrylic copolymer, to which 2-isocyanatoethyl methacrylate (MOI) was added so that the addition ratio was 80 equivalents relative to the hydroxyl group (100 equivalents) derived from HEA. To the energy ray curable acrylic copolymer (weight average molecular weight: 800,000) obtained by adding 1.5 parts by mass of trimethylolpropane adduct tolylene diisocyanate (Mitsui Chemicals, Takenate D-101E) as a crosslinking agent and 2.2 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (IGM Resin, Omnirad651) as a photopolymerization initiator, toluene was further added to adjust the solid content concentration to 30%, and the mixture was stirred for 30 minutes to prepare a pressure-sensitive adhesive composition.

[0090] Next, the prepared adhesive composition solution was applied to a PET-based release film (manufactured by Lintec Corporation, SP-PET382150, thickness 38 μm) and dried to form an adhesive layer with a thickness of 10 μm. This was then bonded to a PET film (manufactured by Toray Industries, Inc., thickness 75 μm) to produce an adhesive sheet as a surface protection sheet.

[0091] (2. Preparation of Composition for Forming Convex Pattern) An energy ray curable resin was obtained by blending 40 parts by weight of a bifunctional polyol-modified urethane acrylate (molecular weight 7300), 60 parts by weight of isobornyl acrylate, and 0.5 parts by weight of a photopolymerization initiator (Irgacure 1173, manufactured by BASF). An antistatic agent shown in Table 1 was added to the obtained energy ray curable resin in a weight ratio shown in the same table, to obtain a convex pattern forming composition.

[0092] The ionic liquid AS400 and the reactive ionic liquid RE3000MA were manufactured by Nippon Nyukazai Co., Ltd.

[0093] The charge amount and surface resistivity of the obtained convex pattern forming composition were measured. The results are shown in Table 1.

[0094] [Table 1]

[0095] According to the method for protecting a workpiece of the present invention, the antistatic agent does not adhere to the object to be protected (for example, a circuit) during protection of the workpiece, so that the object to be protected can be reliably protected and charging of the object to be protected can be prevented. [Explanation of symbols]

[0096] 1. Work 2...Circuit 3…Line to be cut 4…Convex pattern 10...Surface protection sheet 12...Pickup tape 14…Ring frame

Claims

1. A method for protecting a workpiece, comprising a step of attaching a surface protection sheet to a surface of the workpiece, The surface of the workpiece has an inner periphery on which a plurality of circuits are formed and an outer periphery surrounding the inner periphery and having no circuits; forming a convex pattern containing an antistatic agent on at least the outer periphery; A method for protecting a workpiece, comprising attaching a surface protection sheet to the surface on which the convex pattern is formed.

2. The method for protecting a workpiece according to claim 1 , wherein the convex pattern is also formed between the circuits on the inner periphery.

3. The method for protecting a workpiece according to claim 1 , wherein the convex pattern is made of a resin composition containing an antistatic agent and a resin component.

4. The method for protecting a workpiece according to claim 1 , wherein the surface protection sheet does not contain an antistatic agent.

5. Protecting a workpiece by the method according to any one of claims 1 to 4, Grind the back side of the workpiece while protecting it. The surface protection sheet is peeled off, and the convex pattern is removed together with the surface protection sheet.

6. A step of forming a groove on the surface of the workpiece before the step of forming a convex pattern on the surface of the workpiece, The method for machining a workpiece according to claim 5 , wherein in the step of grinding the rear surface of the workpiece, the workpiece is diced into a plurality of workpiece pieces starting from the grooves.

7. A process for forming a modified region inside the workpiece before the process for grinding the back surface of the workpiece, The method for machining a workpiece according to claim 5 , wherein in the step of grinding the rear surface of the workpiece, the workpiece is diced into a plurality of workpiece individual pieces starting from modified regions.

8. A resin composition used to provide a convex pattern in the method for protecting a workpiece according to any one of claims 1 to 4, the resin composition comprising an antistatic agent and a resin component.

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