JP2010027686A - Surface protecting sheet and method for grinding semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protecting sheet which is prevented from being pasted on a wafer even if the surface protecting sheet contacts the wafer in positioning an opening portion of the surface protecting sheet to a bump forming portion of a semiconductor wafer, and which is pasted to the wafer by a predetermined simple means after positioning. <P>SOLUTION: This surface protecting sheet, used in grinding the rear surface of the semiconductor wafer, has on one surface of a substrate sheet an opening portion having a diameter smaller than the outer diameter of the semiconductor wafer to be pasted and having no thermoplastic adhesive formed thereon, and a pasting portion including a thermoplastic adhesive layer surrounding the opening portion. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a surface protection sheet and a semiconductor wafer grinding method, and in particular, a surface protection sheet suitably used for a back grinding process of a semiconductor wafer in which bumps having high height are arranged at high density on a circuit surface, The present invention also relates to a method for grinding a semiconductor wafer on which such bumps are formed.

  With the high density mounting of semiconductor devices, spherical solder (also referred to as bumps) is used for bonding the IC chip and the substrate. In particular, when IC chips are directly joined, bumps having a diameter of about several hundreds of micrometers are often used. Such bumps are previously bonded to the circuit surface of the semiconductor wafer with high density.

  On the other hand, with the spread of IC cards, IC chips are being made thinner. For this reason, it has been required to grind the back surface of the wafer and reduce the thickness of the wafer to 50 to 100 μm or less. As the wafer that is a brittle member becomes thinner, the risk of breakage increases during processing and transportation. In addition, the circuit surface may be damaged or contaminated by cutting waste generated during back grinding. For this reason, when grinding a wafer to an extremely thin thickness or transporting an extremely thin wafer, the work is carried out by protecting the circuit surface side of the wafer with a surface protection sheet such as an adhesive sheet.

  However, when the back surface of the wafer with bumps as described above formed on the circuit surface is ground, the pressure difference due to bump bumps directly affects the back surface of the wafer, creating dimples and cracks called dimples on the back surface of the wafer. This will damage the semiconductor wafer. Further, the height of the bumps hinders the wafer and the surface protection sheet from coming into close contact with each other, and the wafer and the surface protection sheet may peel off particularly at the outer peripheral edge. As a result, water and grinding debris used during grinding may enter from the gap between the wafer and the surface protection sheet, and the wafer circuit surface may be damaged or contaminated.

  For this reason, by increasing the thickness of the pressure-sensitive adhesive layer of the surface protection sheet and further increasing the flowability of the pressure-sensitive adhesive, the pressure-sensitive adhesive layer and the wafer are brought into close contact with each other, and the pressure caused by bump bumps due to the cushioning property of the pressure-sensitive adhesive layer We deal with it by eliminating the difference. However, if the thickness of the pressure-sensitive adhesive layer is increased and the fluidity thereof is increased, the pressure-sensitive adhesive easily wraps around the base portion of the bump. For this reason, the adhesive adhered to the base portion of the bump by the peeling operation of the surface protection sheet may cause in-layer destruction, and a part thereof may remain on the circuit surface. This is a problem that may occur even when a surface protection sheet using an energy ray curable adhesive is used. If the adhesive remaining on the circuit surface is not removed by solvent cleaning or the like, it remains as a foreign substance of the device and impairs the reliability of the completed device.

In order to solve such a problem, as shown in FIG. 4 attached to this specification, Patent Document 1 discloses a surface protection sheet 30 used when grinding a back surface of a semiconductor wafer. On one side, an opening 33 in which a pressure-sensitive adhesive layer having a diameter smaller than the outer diameter of the semiconductor wafer 4 to be attached is formed, and a pressure-sensitive adhesive layer 32 (double-sided pressure-sensitive adhesive sheet or the like) formed on the outer periphery thereof is formed. A surface protection sheet provided with a portion is disclosed. This surface protection sheet 30 has a structure in which a double-sided pressure-sensitive adhesive sheet 32 punched into a ring shape is formed on one surface of a base material 31, and no adhesive is provided on the portion that contacts the bump 5. The adhesive does not adhere to the root portion of 5, so that the reliability of the device cannot be insufficient. Moreover, since the edge part of the wafer 4 can be normally closely fixed by the adhesive layer of the double-sided pressure-sensitive adhesive sheet 32, the cleaning water can be prevented from entering the circuit surface, and the contamination of the wafer can be reduced.
JP 2005-123382 A

  In the above surface protection sheet 30, the opening 33 is aligned so as to correspond to the bump forming portion of the semiconductor wafer, and then the ring-shaped adhesive layer 32 (double-sided adhesive sheet or the like) is placed on the outer periphery of the semiconductor wafer. The end portion is attached to protect the bump forming portion of the semiconductor wafer. However, the adhesive layer is pressure sensitive adhesive. For this reason, when the adhesive layer 32 comes into contact with the semiconductor wafer 4 when aligning the surface protection sheet, the surface protection sheet is placed in a state where the positions of the opening 33 and the bump forming portion of the semiconductor wafer are shifted. It may be stuck on a semiconductor wafer.

  When the positions of the opening 33 and the bump forming portion of the semiconductor wafer are shifted, the bump forming portion is laminated on the adhesive layer of the surface protection sheet. As a result, the wafer tilts and the back surface of the wafer cannot be ground to a uniform thickness. For this reason, when the positions of the opening 33 and the bump forming portion of the semiconductor wafer are shifted, it is necessary to peel off the surface protection sheet 10 from the wafer, perform alignment again, and attach the surface protection sheet. . However, since the semiconductor wafer is brittle, the wafer may be damaged during the peeling operation. Further, the surface protective sheet once attached to the semiconductor wafer and peeled is often deformed by applying a tension at the time of peeling. For this reason, it is difficult to reuse the peeled surface protection sheet.

  The present invention has been made in view of the prior art as described above, and the surface protection sheet contacts the wafer when the opening of the surface protection sheet is aligned with the bump forming portion of the semiconductor wafer. Even if the sheet is not attached to the wafer, the object is to provide a surface protection sheet that can be attached to the wafer by a predetermined simple means after alignment.

The gist of the present invention aimed at solving such problems is as follows.
(1) A surface protection sheet used when grinding a back surface of a semiconductor wafer,
One side of the base sheet has an opening in which a thermoplastic adhesive having a diameter smaller than the outer diameter of the semiconductor wafer to be attached is not formed, and an adhesive part including a thermoplastic adhesive layer surrounding the opening. Surface protection sheet.
(2) The adhesive strength according to JIS Z0237 when pressure-bonded at 23 ° C. of the thermoplastic adhesive layer to the mirror surface silicon wafer is 0.1 N / 50 mm or less, and conforms to JIS Z0237 when pressure-bonded at 140 ° C. The surface protective sheet according to (1), which has an adhesive strength of 10 N / 50 mm or more.
(3) The thermoplastic adhesive layer of the sticking part of the surface protecting sheet according to (1) or (2) above,
A semiconductor wafer having a circuit surface on which bumps are formed, and the bump forming portion of the semiconductor wafer is heat-sealed so as to correspond to the opening portion of the surface protection sheet to protect the bump forming portion of the semiconductor wafer,
A method for grinding a semiconductor wafer, comprising grinding a back surface of a wafer to which the surface protecting sheet is not attached.

  In the surface protective sheet of the present invention, a thermoplastic adhesive layer having no pressure-sensitive adhesive property is used in place of the pressure-sensitive adhesive layer, so that the openings of the surface protective sheet are formed on the bumps of the semiconductor wafer. Even when the thermoplastic adhesive layer of the surface protection sheet comes into contact with the wafer when aligning to the part, the sheet is not adhered to the wafer, and after alignment, the sheet is adhered to the wafer by thermal fusion. Can do. As a result, alignment and adhesion between the sheet and the wafer can be performed easily and precisely. In addition, according to the surface protection sheet and the semiconductor wafer grinding method of the present invention, the thermoplastic adhesive is attached to the base portion of the bump because the thermoplastic adhesive is not provided on the portion contacting the bump. Therefore, lack of device reliability cannot occur. Moreover, since the edge part of a wafer can be closely_contact | adhered and fixed by the sticking part containing a thermoplastic adhesive layer, infiltration of the washing water to a circuit surface is prevented, and the contamination of a wafer can be reduced.

Hereinafter, the present invention will be described more specifically with reference to the drawings.
FIG. 1 shows a perspective view of a surface protecting sheet 10 according to the present invention, and FIG. 2 shows a sectional view taken along line XX of FIG.

  As shown in FIGS. 1 and 2, the surface protective sheet 10 has an opening 3 in which a thermoplastic adhesive having a smaller diameter than the outer diameter of the semiconductor wafer 4 to be attached is not formed on one side of the base sheet 1. And an adhesive portion 2 including a thermoplastic adhesive layer 21 surrounding the opening.

(Substrate sheet 1)
If the base material sheet 1 used for the sheet | seat 10 for surface protection of this invention is a resin sheet, it will not specifically limit, Various resin sheets can be used. As such a resin sheet, for example, polyolefin such as low density polyethylene, linear low density polyethylene, polypropylene, polybutene, ethylene vinyl acetate copolymer, ethylene (meth) acrylic acid copolymer, ethylene (meth) acrylic acid Examples thereof include ethylene copolymers such as ester copolymers, polyesters such as polyethylene terephthalate and polyethylene naphthalate, and resin films such as polyvinyl chloride, acrylic rubber, polyamide, urethane, and polyimide. The base sheet 1 may be a single layer or a laminate. Moreover, the sheet | seat which gave the process of bridge | crosslinking etc. may be used.

  As such a base sheet 1, a sheet formed by extrusion molding of a thermoplastic resin may be used, or a sheet obtained by thinning and curing a curable resin by a predetermined means is used. Also good.

  Examples of the curable resin include a resin composition in which an energy ray-curable urethane acrylate oligomer is a main component, an acrylate monomer having a relatively bulky group is a diluent, and a photopolymerization initiator is blended as necessary. Used.

  The thickness of the base sheet 1 is preferably 30 to 1000 μm, more preferably 50 to 500 μm, and particularly preferably 100 to 300 μm.

  Further, as shown in FIG. 2, the base sheet 1 may be pre-punched to a size substantially equal to the outer diameter of the semiconductor wafer to be stuck, and the surface protection sheet 10 and the semiconductor wafer 4 are bonded together. After bonding, the base sheet 1 may be cut according to the outer diameter of the semiconductor wafer.

(Attaching part 2)
The sticking part 2 of the surface protective sheet 10 of the present invention includes a thermoplastic adhesive layer 21. The thermoplastic adhesive layer 21 is located on the uppermost part of the sticking part 2 and is used for bonding to the semiconductor wafer 4.

  The thermoplastic adhesive layer 21 is made of a thermoplastic resin having a glass transition temperature (Tg) of preferably 30 to 150 ° C, more preferably 40 to 120 ° C, and particularly preferably 60 to 90 ° C. The thermoplastic adhesive layer 21 does not have a tack at normal temperature (23 ° C.), does not adhere even when it comes into contact with a wafer or the like, and develops an adhesive force by heating. Further, the melting point of the thermoplastic adhesive is preferably 200 ° C. or less, more preferably 60 to 120 ° C.

  Further, the adhesive force of the thermoplastic adhesive to the mirror silicon wafer measured according to JIS Z0237 is 0.1 N / 50 mm or less, preferably 0.001 to 0.1 N / 50 mm when pressed at 23 ° C. More preferably, it is 0.005-0.05 N / 50mm. Moreover, it is 10 N / 50mm or more when it pressure-bonds at 140 degreeC, Preferably it is 10-100 N / 50mm, More preferably, it is 20-60 N / 50mm.

  As the thermoplastic adhesive, for example, polyethylene, polypropylene, polyester, ethylene-vinyl acetate resin, ethylene-ethyl acrylate copolymer, and ethylene-isobutyl acrylate copolymer are preferably used. Among these, ethylene-vinyl acetate resin is particularly preferably used. The ethylene-vinyl acetate resin is a solid (film-like) adhesive at room temperature, which is mainly composed of a resin obtained by copolymerizing ethylene vinyl alcohol and vinyl acetate.

  The thermoplastic adhesive layer 21 may be provided directly on the base sheet 1 by dry lamination, thermocompression bonding, melt extrusion, or the like, or may be laminated via the pressure-sensitive adhesive layer 20. The pressure-sensitive adhesive layer 20 may be a single-layer pressure-sensitive adhesive layer or a double-sided pressure-sensitive adhesive sheet.

  Further, the thermoplastic adhesive layer 21 may be formed as a single layer of the thermoplastic adhesive layer, or as shown in FIG. 2, the thermoplastic adhesive layer 21 on one side of the core film 22 and the other side. Alternatively, a single-sided thermoplastic resin-single-sided adhesive sheet provided with a single-layer adhesive layer 20 may be used. Furthermore, the aspect which provided the thermoplastic adhesive layer 21 on both surfaces of the core material film 22 may be sufficient.

  When the thermoplastic adhesive layer is formed of a single-sided thermoplastic resin-single-sided adhesive sheet, if a relatively rigid film such as a polyethylene terephthalate film is used as the core film 22, This is preferable because the dimensional stability at the time of wafer sticking becomes good.

  The preferable thickness of the sticking part 2 including the thermoplastic adhesive layer 21 is determined by the height of the bumps 5 formed on the wafer 4 to be stuck. The thickness (Tt) of the sticking part 2 is the thickness when the thermoplastic adhesive layer is used as a single layer, and when the adhesive layer 20 or the core material film 22 is used, it is the thermoplastic adhesive. The total thickness of the sticking part 2 which consists of the agent layer 21 and these other resin layers is meant. When the thickness (Tt) of the sticking part 2 and the height (Bh) of the bump are used, the difference (Bh−Tt) is preferably −5 to +50 μm, more preferably ± 0 to +40 μm. For example, when the height (Bh) of the bump 5 is 100 μm, the thickness (Tt) of the sticking part 2 is 50 to 105 μm, preferably 60 to 100 μm. With such a thickness relationship, the bumps 5 of the wafer and the base sheet 1 are in contact with each other with an appropriate pressure, and the surface protection sheet 10 is less likely to be peeled off or displaced during grinding.

(Preparation of surface protection sheet 10)
As shown in FIG. 3, the surface protection sheet 10 is a base sheet surface (opening) in which the bonding portion 2 is not formed in the circuit forming portion provided with the bumps 5 of the wafer 4 to be bonded. The outer portion of the wafer 4 where the part 3) faces and the circuit is not formed is configured such that the sticking part 2 including the thermoplastic adhesive layer 21 faces.

  A single-layer sheet of a thermoplastic adhesive layer or a multilayer resin sheet including a thermoplastic adhesive layer (hereinafter referred to as “raw material sheet”) is punched before being laminated on the base sheet 1. To form an opening 3 where a thermoplastic adhesive is not formed. Thereafter, the stamped raw material sheet is laminated on the base material sheet directly or via the pressure-sensitive adhesive layer 20 as described above. When the raw material sheet is laminated on the base material sheet via the pressure-sensitive adhesive layer 20, the raw material sheet is laminated on the release film via the pressure-sensitive adhesive layer 20, and only the raw material sheet and the pressure-sensitive adhesive layer are punched and peeled off. If the film is not completely punched, it is preferable that the release film becomes a carrier for the stamped raw material sheet, and the subsequent processing can be performed continuously by roll-to-roll. Next, the release film is peeled off, the raw material sheet is laminated on the base material sheet 1 via the pressure-sensitive adhesive layer 20, and the raw material sheet having the opening 3 (adhesion part 2) is attached. Create

  You may use as the surface protection sheet 10 of this invention by the structure of this step. When used in this configuration, the outer peripheral thermoplastic adhesive layer 21 is placed on the outer surface of the wafer while aligning the opening 3 of the surface protection sheet 10 with the position of the circuit surface of the wafer, and the like. Is attached by thermally fusing with the wafer. Then, the front surface protection sheet protruding from the wafer is cut and separated along the outer periphery of the wafer 4 and subjected to back surface grinding.

  In the production of the surface protection sheet, after forming the opening 3, the outer periphery of the raw material sheet is punched out in accordance with the diameter of the wafer to be pasted substantially concentrically with the opening 3 to form the pasting part 2. preferable. That is, it is preferable to punch out such that the ring-shaped sticking portion 2 and the pressure-sensitive adhesive layer 20 remain on the release sheet.

  The base sheet 1 may be preliminarily cut into the same shape as the outer diameter of the wafer, and then laminated with a raw material sheet (adhering portion 2) in which an opening is formed. After laminating the sticking part 2 on the large base sheet 1, the base sheet may be punched out in the same shape as the wafer outer diameter. Furthermore, you may punch the base material sheet 1 and the sticking part 2 into the same shape as a wafer outer diameter simultaneously.

  Therefore, as shown in FIGS. 1 to 3, it is preferable to cut the base material 1 and the sticking part 2 in advance according to the outer diameter of the wafer 4. By cutting the wafer in the same shape as the wafer in advance, it is not necessary to perform a step of cutting off an unnecessary portion (a portion protruding from the wafer) of the surface protection sheet with a cutter after the surface protection sheet 10 is attached to the wafer. In this way, the edge of the wafer is scratched by the cutter blade, and subsequent processing does not induce damage to the wafer.

(Backside grinding of wafer)
When grinding the back surface of the wafer, as shown in FIG. 3, the top layer of the sticking part 2 is aligned after the sticking part 2 of the surface protecting sheet 10 is accurately positioned so as not to face the bump 5 of the wafer 4. The thermoplastic adhesive layer 21 and the outer peripheral edge of the wafer 4 are thermocompression bonded to form a surface protection form for grinding the semiconductor wafer. The thermoplastic adhesive layer 21 has no tack at normal temperature. Accordingly, when the surface protection sheet 10 and the wafer 4 are aligned, even if the thermoplastic adhesive layer 21 contacts the wafer, the sheet is not attached to the wafer. For this reason, it is possible to easily correct the positional deviation between the surface protection sheet 10 and the wafer 4. Therefore, according to the present invention, it is possible to easily and precisely align and bond the sheet and the wafer.

  In addition, when the base material sheet 1 and the sticking part 2 are not cut in the same shape as the wafer in advance, after attaching the surface protection sheet 10 to the wafer, an unnecessary part of the surface protection sheet (from the wafer) Cut out the protruding part.

  The wafer used in the semiconductor wafer grinding method of the present invention may be any wafer as long as bumps are formed on the circuit surface, but the bump height is 50 μm or more, preferably The wafer having a bump position of 100 μm or more and the outermost bump located 0.7 to 30 mm inside from the outer periphery of the wafer has been difficult to apply in the conventional surface protective adhesive sheet. More preferably used.

  The wafer 4 having the above surface protection configuration is ground by a normal grinding method using a grinder 6 or the like by placing the surface protection sheet 10 side on a wafer fixing base (not shown) of a wafer grinding apparatus. Do.

  Since the adhering portion 2 is securely bonded to the outer portion of the wafer 4 so as to surround the entire circumference, the intrusion of cleaning water or the like during the grinding process does not occur and the circuit surface of the wafer is not contaminated. Further, since the apexes of the bumps are in contact with the substrate sheet with an appropriate pressure with respect to the wafer circuit surface, the surface protection sheet is less likely to be peeled off or displaced during grinding.

  Thereafter, the wafer 4 is separated from the surface protection sheet 10. As shown in the figure, the wafer 4 is fixed to the surface protection sheet 10 via a ring-shaped thermoplastic adhesive layer 21. Since the ring-shaped thermoplastic adhesive layer 21 has a narrow width and therefore a low adhesive strength, the wafer 4 can be easily peeled off.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
In addition, the evaluation method of the base material sheet used in the following Examples and Comparative Examples, a silicon wafer, and grinding water infiltration is shown below.

(Substrate sheet)
50 parts by weight of urethane acrylate oligomer having a weight average molecular weight of 5000 (manufactured by Arakawa Chemical Co., Ltd.), 25 parts by weight of isobornyl acrylate, 25 parts by weight of phenylhydroxypropyl acrylate, photopolymerization initiator (manufactured by Ciba Specialty Chemicals, 2 parts by weight of Irgacure 184) and 0.2 parts by weight of a phthalocyanine pigment were blended to obtain a photocurable resin composition for casting a base sheet.

The obtained resin composition was coated on a polyethylene terephthalate (PET) film (manufactured by Toray Industries Inc., thickness 38 μm) by a fountain die method so that the thickness was 160 μm, and the same PET film was laminated on the coating film. Thereafter, using a high-pressure mercury lamp (160 W / cm, height 10 cm), an ultraviolet irradiation treatment was performed under conditions of a light amount of 250 mJ / cm ² to crosslink and cure the coating film. Thereafter, the PET films on both sides were peeled off to obtain a substrate sheet having a thickness of 160 μm.

(Silicon wafer)
Bumps having a height of 100 μm were formed on a mirror surface of a silicon wafer having a diameter of 200 mm and a thickness of 750 μm at a pitch (distance between the centers of adjacent bumps) of 200 μm.

(Infiltration of grinding water)
After grinding the wafer, the surface of the wafer circuit was visually observed, and “Yes” was indicated when the wafer circuit surface was infiltrated with cleaning water, and “No” was indicated when there was no ingress of cleaning water.

[Example 1]
(Raw material sheet)
On one side of a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc.) having a thickness of 50 μm as a core material, an ethylene-vinyl acetate resin (manufactured by Tosoh Corporation, Ultrasen 638, thickness 35 μm, melting point 83 ° C.) as a thermoplastic adhesive. Were laminated to obtain a raw material sheet having a total thickness of 85 μm.

(Surface protection sheet)
A silicone-treated PET film having a thickness of 38 μm (PET3811S manufactured by Lintec Co., Ltd.) is coated and dried with a strong adhesive acrylic adhesive (PA-T1 manufactured by Lintec Co., Ltd.) so that the dry film thickness is 15 μm. The sheet was bonded to the PET surface. Subsequently, the obtained sheet was punched into a circle having a diameter of 190 mm, and this circular portion was removed to provide an opening. The PET film of the pressure-sensitive adhesive layer was peeled off and bonded to the base material sheet to obtain a sheet composed of a thermoplastic adhesive layer, a core material, a pressure-sensitive adhesive layer, and a base material sheet.

  The layers from the base sheet to the thermoplastic adhesive layer are punched into a circle with a diameter of 200 mm so as to be concentric with the punched raw material sheet, and a 5 mm wide ring-shaped paste is applied on the circular base sheet with a diameter of 200 mm. A surface protective sheet having a landing portion was prepared.

(Adhesive strength of thermoplastic adhesive layer)
The adhesive force of the thermoplastic adhesive layer when the prepared surface protective sheet was pressure-bonded at 23 ° C. and 140 ° C. (pressure 0.2 MPa) was measured using a universal tensile testing machine (TENSILON RTA-100 manufactured by Orientec Corp.). . The adherend was used as a mirror surface of a silicon wafer, and measurement was performed in accordance with JIS Z0237. Table 1 shows the adhesive strength at each temperature.

(Backside grinding of wafer)
The above-mentioned surface protection sheet was stacked on the bump forming surface side of the silicon wafer so that the respective outlines coincided with each other. That is, the silicon wafer is stacked via the sticking portion so that the bump forming portion of the silicon wafer corresponds to the opening of the surface protection sheet, and the temperature is measured using a heat seal machine (TP701, manufactured by Tester Sangyo Co., Ltd.). Pressure bonding was performed at 140 ° C. and a pressure of 0.2 MPa for 1 second, and the uppermost thermoplastic adhesive layer of the bonded portion was heat-bonded to the silicon wafer. Since the bump height was 100 μm, the difference between the bump height and the total thickness of the sticking part was 0 μm with respect to the total thickness of the sticking part including the acrylic adhesive layer being 100 μm.

  The surface protecting sheet side of the silicon wafer was fixed to the polishing table surface of the wafer polishing apparatus, and the silicon wafer was ground so that the finished thickness was 50 μm.

The surface protection sheet did not fall off during the grinding, and the cleaning water did not penetrate into the circuit surface side of the wafer, and the grinding could be completed without damaging the wafer. Thereafter, the surface protective sheet was peeled off. When the circuit surface was observed, no foreign matter was confirmed.
The results are shown in Table 2.

[Example 2]
A sheet for surface protection was prepared in the same manner as in Example 1 except that the thermoplastic adhesive was changed to a polyester resin (Byron 200 manufactured by Toyobo Co., Ltd., thickness 35 μm, Tg 67 ° C.), and the back surface of the wafer was ground.
The results are shown in Table 2.

[Example 3]
A sheet for surface protection was prepared in the same manner as in Example 1 except that the thermoplastic adhesive layer was changed to an ethylene-ethyl acrylate copolymer (Evaflex-EEA A702, thickness 35 μm, melting point 78 ° C., manufactured by Mitsui DuPont Chemicals). Then, the back surface of the wafer was ground.
The results are shown in Table 2.

[Example 4]
A surface protective sheet was prepared in the same manner as in Example 1 except that the thermoplastic adhesive layer was changed to polyethylene (Suntech-LD L1640 manufactured by Asahi Kasei Chemicals Corporation, thickness 35 μm, melting point 106 ° C.), and the back surface of the wafer was ground. It was.
The results are shown in Table 2.

The perspective view of the sheet for surface protection concerning the present invention. XX sectional drawing of FIG. The state which affixes the surface protection sheet of this invention on the bump surface of a wafer, and performs wafer back surface grinding is shown. The state which affixes the conventional surface protection sheet on the bump surface of a wafer and performs wafer back surface grinding is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material sheet 2 ... Adhesion part 20 ... Adhesive layer 21 ... Thermoplastic adhesive layer 22 ... Core material film 3 ... Opening part 4 ... Semiconductor wafer 5 ... Bump 6 ... Grinder 10 ... Sheet for surface protection

Claims (3)

A surface protection sheet used when grinding the back surface of a semiconductor wafer,
One side of the base sheet has an opening in which a thermoplastic adhesive having a diameter smaller than the outer diameter of the semiconductor wafer to be attached is not formed, and an adhesive part including a thermoplastic adhesive layer surrounding the opening. Surface protection sheet.   The adhesive strength according to JIS Z0237 when bonded at 23 ° C. of the thermoplastic adhesive layer to the mirror surface silicon wafer is 0.1 N / 50 mm or less, and the adhesive strength according to JIS Z0237 when bonded at 140 ° C. The sheet for surface protection according to claim 1, which is 10 N / 50 mm or more. The thermoplastic adhesive layer of the sticking part of the surface protecting sheet according to claim 1 or 2,
A semiconductor wafer having a circuit surface on which bumps are formed, and the bump forming portion of the semiconductor wafer is heat-sealed so as to correspond to the opening portion of the surface protection sheet to protect the bump forming portion of the semiconductor wafer,
A method for grinding a semiconductor wafer, comprising grinding a back surface of a wafer to which the surface protecting sheet is not attached.

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