JP2013181109A - Tacky adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tacky adhesive sheet retaining sufficient tacky adhesive power, and excellent in handleability after peeling a separator such as paper passability.SOLUTION: A tacky adhesive sheet is provided with a substrate layer and a tacky adhesive layer, where the ball number is 2 or less in the ball tack test of the tacky adhesive layer, and adhesive power to a silicon mirror wafer is 0.3 N/20 mm or greater. By using such tacky adhesive sheet, a tacky adhesive sheet satisfying both sufficient tacky adhesive power as the tacky adhesive sheet and handleability after peeling a separator such as paper passability can be obtained.

Description

  The present invention relates to an adhesive sheet.

  A semiconductor wafer is manufactured in a large diameter state, and after a pattern is formed on the front surface, the thickness of the wafer is usually reduced to about 100 to 600 μm by grinding the back surface. Thereafter, the device is further cut and separated (diced) into element pieces, and the process proceeds to a mounting process. In the process of grinding the back surface of the semiconductor wafer (back grinding process), an adhesive sheet is used to protect the pattern surface of the semiconductor wafer. The pressure-sensitive adhesive sheet used for wafer processing is required to have a pressure-sensitive adhesive force that can hold the wafer during a process such as wafer polishing or cutting and prevent wafer breakage or the like. As such a pressure-sensitive adhesive sheet, for example, a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer coated with an acrylic pressure-sensitive adhesive is provided on a base material containing a polyethylene resin has been proposed (for example, Patent Document 1).

  In the processing of semiconductor wafers, in order to improve productivity, the adhesive sheet is attached using a tape attaching device. In the tape applicator, the pressure-sensitive adhesive sheet fed from the tape supply unit is peeled off the separator, and is applied to the wafer surface by an applicator roller. Next, the adhered adhesive sheet is cut into a wafer shape with a cutter blade. Unnecessary tape after being cut into a wafer shape is taken up by the tape collecting unit, and a new tape is fed out from the tape supply unit. The pressure-sensitive adhesive sheet is introduced into a tape applicator before use. At this time, it is necessary to pass the pressure-sensitive adhesive sheet from which the separator has been peeled off through a narrow roll gap to the tape recovery section. However, an adhesive sheet having a high adhesive strength that satisfies the requirements during processing is likely to adhere to the roll and is difficult to pass. In addition, the adhesive sheet having a high adhesive force may adhere to a table or the like even when the unnecessary tape after winding is wound, and may be difficult to collect. As described above, in the adhesive sheet having a high adhesive force, the productivity of the wafer may be lowered.

  On the other hand, when the adhesive strength of the adhesive sheet is reduced, it becomes difficult to sufficiently hold the wafer in each process during wafer processing. Therefore, for example, when used as a wafer protective tape in a back grinding process, in an adhesive sheet having a low adhesive force, grinding water may enter during grinding and wafer cracking may occur. As described above, it is difficult to achieve both the adhesive strength suitable for each application as the pressure-sensitive adhesive sheet and the handleability after separation of the separator such as paper permeability.

International Publication No. 2007/116856 Pamphlet

  The present invention has been made in order to solve the above-described conventional problems, and the object of the present invention is to achieve both adhesive strength and handling properties (such as low tack) after separation of the separator such as paper permeability. To provide a sheet.

As a result of repeated studies, the present inventors have determined that two independent properties of tack and adhesive strength of the adhesive layer have a ball number of 2 or less in the ball tack test and an adhesive strength of 0.3 N / It discovered that the said subject could be solved by setting it as 20 mm or more.
The pressure-sensitive adhesive sheet of the present invention comprises a base material layer and a pressure-sensitive adhesive layer, the ball number of the pressure-sensitive adhesive layer in the ball tack test is 2 or less, and the adhesive force to the silicon mirror wafer is 0.3 N / 20 mm or more. It is.
In preferable embodiment, the said adhesive layer contains polyolefin resin.
In a preferred embodiment, the polyolefin-based resin includes an amorphous propylene- (1-butene) copolymer polymerized using a metallocene catalyst.
In a preferred embodiment, the polyolefin resin further contains a crystalline polypropylene resin.
In a preferred embodiment, the pressure-sensitive adhesive sheet of the present invention is obtained by coextrusion molding of a pressure-sensitive adhesive layer forming material and a base material layer forming material.
In a preferred embodiment, the pressure-sensitive adhesive sheet of the present invention is for semiconductor wafer processing.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the adhesive sheet which has sufficient adhesive force and was excellent in the handleability (low tack) after separator peeling, such as paper permeability. Since the pressure-sensitive adhesive sheet of the present invention is excellent in handleability after peeling of the separator, it is easy to pass paper when attaching the tape to the tape applicator. Therefore, the productivity of the semiconductor wafer can be further improved. Furthermore, since it has sufficient adhesive force as an adhesive sheet, it can be used suitably for various applications. The pressure-sensitive adhesive sheet of the present invention is particularly suitable for semiconductor wafer processing applications.

It is a schematic sectional drawing of the adhesive sheet by preferable embodiment of this invention.

A. Overall configuration diagram 1 of the adhesive sheet is a schematic sectional view of a pressure-sensitive adhesive sheet according to a preferred embodiment of the present invention. The pressure-sensitive adhesive sheet 100 includes a base material layer 10 and a pressure-sensitive adhesive layer 20 in this order.

  The pressure-sensitive adhesive sheet of the present invention may further include any appropriate other layer. Examples of the other layer include a surface layer that is provided on the side of the base material layer opposite to the pressure-sensitive adhesive layer and can impart heat resistance to the pressure-sensitive adhesive sheet.

  The pressure-sensitive adhesive sheet of the present invention has a ball number of 2 or less in the ball tack test of the pressure-sensitive adhesive layer. When the ball number in the ball tack test of the pressure-sensitive adhesive layer is 2 or less, the handleability of the pressure-sensitive adhesive sheet after separation of the separator such as paper passing properties is improved. Therefore, when performing a sticking process using a tape sticking apparatus, the paper passing at the time of tape attachment is easy, and the productivity of a semiconductor wafer can further be improved. The ball number in the ball tack test of the pressure-sensitive adhesive layer is preferably 1 or less, more preferably 0 (that is, the ball of ball number 1 falls). In this specification, the ball tack is a value measured at an inclination angle of 30 degrees by an inclined ball tack method according to JIS Z 0237.

  In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer to the silicon mirror wafer is 0.3 N / 20 mm or more. If the pressure-sensitive adhesive layer has an adhesive strength of 0.3 N / 20 mm or more, it has sufficient adhesive strength as a pressure-sensitive adhesive sheet. For example, when used for semiconductor wafer processing, the wafer is sufficiently retained. Can do. The adhesive force of the adhesive layer to the silicon mirror wafer is preferably 0.3 N / 20 mm to 3.0 N / 20 mm, more preferably 0.4 N / 20 mm to 2.5 N / 20 mm, and even more preferably 0. .4N / 20mm to 2.0N / 20mm. In addition, the said adhesive force is a method according to JIS Z 0237 (2000) using a semiconductor mirror wafer test plate (made of silicon) (bonding condition: 2 kg roller 1 reciprocation, peeling speed: 300 mm / min, peeling angle 180). The value measured in °). The pressure-sensitive adhesive sheet of the present invention can achieve both the characteristic that the ball number in the above-described ball tack test is 2 or less (that is, low tack) and sufficient pressure-sensitive adhesive force required for the pressure-sensitive adhesive sheet.

  The thickness of the pressure-sensitive adhesive sheet of the present invention is preferably 90 μm to 285 μm, more preferably 105 μm to 225 μm, and still more preferably 120 μm to 205 μm.

  The thickness of the base material layer is preferably 30 μm to 185 μm, more preferably 65 μm to 175 μm.

  The thickness of the pressure-sensitive adhesive layer is preferably 20 μm to 100 μm, more preferably 25 μm to 65 μm.

  The pressure-sensitive adhesive sheet of the present invention can be provided in a state protected by a separator. The pressure-sensitive adhesive sheet of the present invention can be rolled up in a state protected by a separator. A separator has a function as a protective material which protects an adhesive sheet until it uses for practical use. As the separator, for example, a plastic (for example, polyethylene terephthalate (PET), polyethylene, polypropylene) film coated with a release agent such as a silicon release agent, a fluorine release agent, or a long-chain alkyl acrylate release agent, paper or Nonwoven fabric etc. are mentioned.

  For example, when the pressure-sensitive adhesive sheet of the present invention is not protected by a separator, a back surface treatment may be performed on the outermost layer opposite to the pressure-sensitive adhesive layer. The back surface treatment can be performed using a release agent such as a silicon release agent or a long-chain alkyl acrylate release agent. The pressure-sensitive adhesive tape of the present invention can be easily wound into a roll by performing a back surface treatment.

B. Adhesive Layer The adhesive layer may have a ball number of 2 or less in the ball tack test and an adhesive force to the silicon mirror wafer of 0.3 N / 20 mm or more. The pressure-sensitive adhesive layer is composed of any appropriate pressure-sensitive adhesive. For example, a pressure-sensitive adhesive containing a thermoplastic resin such as a polyolefin resin, an acrylic resin, or a styrene resin can be used. The pressure-sensitive adhesive layer preferably contains a polyolefin resin. Specifically, low density polyethylene, ultra low density polyethylene, low crystalline polypropylene, amorphous propylene- (1-butene) copolymer, ionomer resin, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid Examples thereof include ethylene copolymers such as copolymers, ethylene- (meth) acrylic acid ester-maleic anhydride copolymers, ethylene-glycidyl methacrylate copolymers, and polyolefin-modified polymers. The pressure-sensitive adhesive layer more preferably contains an amorphous propylene- (1-butene) copolymer. By using such a pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet that retains sufficient adhesive force and is excellent in handleability after separation of the separator can be obtained. Furthermore, with such a pressure-sensitive adhesive layer, it is possible to produce a pressure-sensitive adhesive sheet by coextrusion molding with a base material layer, and a pressure-sensitive adhesive sheet is obtained with a small number of steps and without using an organic solvent. be able to. In this specification, “amorphous” means a property that does not have a clear melting point such as crystalline.

  The amorphous propylene- (1-butene) copolymer can be obtained by polymerizing propylene and 1-butene, preferably using a metallocene catalyst. More specifically, the amorphous propylene- (1-butene) copolymer performs, for example, a polymerization step in which propylene and 1-butene are polymerized using a metallocene catalyst, and the catalyst residue is removed after the polymerization step. It can be obtained by performing post-processing steps such as a step and a foreign matter removing step. The amorphous propylene- (1-butene) copolymer is obtained in such a form as a powder or a pellet through such steps. Examples of the metallocene catalyst include a metallocene homogeneous mixed catalyst containing a metallocene compound and an aluminoxane, a metallocene supported catalyst in which a metallocene compound is supported on a particulate carrier, and the like.

  The amorphous propylene- (1-butene) copolymer polymerized using the metallocene catalyst as described above exhibits a narrow molecular weight distribution. The molecular weight distribution (Mw / Mn) of the amorphous propylene- (1-butene) copolymer is preferably 3 or less, more preferably 2 or less, and even more preferably 1.1 to 2, particularly Preferably it is 1.2-1.9. Since the amorphous propylene- (1-butene) copolymer having a narrow molecular weight distribution has few low molecular weight components, if such an amorphous propylene- (1-butene) copolymer is used, bleeding of the low molecular weight component can be achieved. It is possible to obtain a pressure-sensitive adhesive sheet that can prevent the adherend from being contaminated by the above.

  The content ratio of the structural unit derived from propylene in the amorphous propylene- (1-butene) copolymer is preferably 80 mol% to 99 mol%, more preferably 85 mol% to 99 mol%. More preferably, it is 90 mol% to 99 mol%.

  The content ratio of the structural unit derived from 1-butene in the above-mentioned amorphous propylene- (1-butene) copolymer is preferably 1 mol% to 15 mol%, more preferably 1 mol% to 10 mol%. It is. If it is such a range, the adhesive sheet excellent in the balance of toughness and a softness | flexibility can be obtained.

  The amorphous propylene- (1-butene) copolymer may be a block copolymer or a random copolymer.

  The weight average molecular weight (Mw) of the amorphous propylene- (1-butene) copolymer is preferably 200,000 or more, more preferably 200,000 to 500,000, and still more preferably 200,000. ~ 300,000. If the weight average molecular weight (Mw) of the amorphous propylene- (1-butene) copolymer is within such a range, a general styrene-based thermoplastic resin, acrylic-based thermoplastic resin (Mw is 100,000 or less) ), A pressure-sensitive adhesive sheet that has less low molecular weight components and can prevent contamination of the adherend can be obtained. Further, during coextrusion molding, the pressure-sensitive adhesive layer can be formed without processing defects, and an appropriate pressure-sensitive adhesive force can be obtained.

  The melt flow rate of the amorphous propylene- (1-butene) copolymer at 230 ° C. and 2.16 kgf is preferably 1 g / 10 min to 50 g / 10 min, more preferably 5 g / 10 min to 30 g / 10 min. Yes, and more preferably 5 g / 10 min to 20 g / 10 min. When the melt flow rate of the amorphous propylene- (1-butene) copolymer is in such a range, a pressure-sensitive adhesive layer having a uniform thickness can be formed by coextrusion molding without processing defects. The melt flow rate can be measured by a method according to JISK7210.

  The amorphous propylene- (1-butene) copolymer may further contain other monomer-derived structural units as long as the effects of the present invention are not impaired. Examples of other monomers include α-olefins such as ethylene, 1-pentene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene, and 3-methyl-1-pentene. .

Preferably, the pressure-sensitive adhesive layer contains F ⁻ , Cl ⁻ , Br ⁻ , NO ₂ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , NH ₄ ⁺ . It does not contain substantially. This is because it is possible to prevent the adherend from being contaminated with the ions. For example, when the pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer is used for processing a semiconductor wafer, the circuit is not disconnected or short-circuited. The pressure-sensitive adhesive layer containing no ions can be obtained, for example, by subjecting the amorphous propylene- (1-butene) copolymer contained in the pressure-sensitive adhesive layer to solution polymerization using a metallocene catalyst as described above. it can. In solution polymerization using the metallocene catalyst, the amorphous propylene- (1-butene) copolymer is purified by repeating precipitation isolation (reprecipitation method) using a poor solvent different from the polymerization solvent. Therefore, a pressure-sensitive adhesive layer that does not contain the ions can be obtained. In this specification, “F ⁻ , Cl ⁻ , Br ⁻ , NO ₂ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , NH ₄ ⁺ are substantially "Not included" means that it is below the detection limit in standard ion chromatographic analysis (for example, ion chromatographic analysis using trade names "DX-320" and "DX-500" manufactured by Dionex). Say. Specifically, F ⁻ , Cl ⁻ , Br ⁻ , NO ₂ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ and K ⁺ are 0.49 μg or less, and Li ⁺ and Na ⁺ are each 1 g of the adhesive layer. Each case is 0.20 μg or less, Mg ²⁺ and Ca ²⁺ are each 0.97 μg or less, and NH ₄ ⁺ is 0.5 μg or less.

The storage elastic modulus (G ′) of the pressure-sensitive adhesive layer is preferably 0.5 × 10 ⁶ Pa to 1.0 × 10 ⁸ Pa, more preferably 0.8 × 10 ⁶ Pa to 3.0 × 10. ⁷ Pa. When the storage elastic modulus (G ′) of the pressure-sensitive adhesive layer is in such a range, a pressure-sensitive adhesive sheet that retains sufficient adhesive force and is excellent in handleability after separation of the separator can be obtained. Moreover, an adhesive sheet provided with the said adhesive layer of such storage elastic modulus (G ') can contribute to achievement of the outstanding grinding precision in the back surface grinding of a wafer, when used for semiconductor wafer processing. In addition, the storage elastic modulus (G ′) in the present invention can be measured by dynamic viscoelastic spectrum measurement.

  The pressure-sensitive adhesive layer may further contain a crystalline polypropylene resin in order to provide a pressure-sensitive adhesive sheet that retains sufficient adhesive strength and is excellent in handleability after separation of the separator. The content of the crystalline polypropylene resin can be set to any appropriate ratio depending on the desired adhesive strength and ball tack. The content of the crystalline polypropylene resin is preferably 0% by weight to 50% by weight based on the total weight of the amorphous propylene- (1-butene) copolymer and the crystalline polypropylene resin. %, More preferably 0% by weight to 40% by weight, and still more preferably 0% by weight to 30% by weight.

  The crystalline polypropylene resin may be homopolypropylene or a copolymer obtained from propylene and a monomer copolymerizable with propylene. Examples of monomers copolymerizable with propylene include α-olefins such as ethylene, 1-pentene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene, and 3-methyl-1-pentene. Etc.

  The crystalline polypropylene resin is preferably obtained by polymerization using a metallocene catalyst in the same manner as the amorphous propylene- (1-butene) copolymer. By using the crystalline polypropylene resin thus obtained, it is possible to prevent contamination of the adherend due to bleeding of low molecular weight components.

  The crystallinity of the crystalline polypropylene resin is preferably 10% or more, and more preferably 20% or more. The crystallinity is typically determined by differential scanning calorimetry (DSC) or X-ray diffraction.

  The pressure-sensitive adhesive layer may further contain other components as long as the effects of the present invention are not impaired. Examples of the other components include an antioxidant, an ultraviolet absorber, a light stabilizer, a heat resistance stabilizer, and an antistatic agent. The kind and usage-amount of another component can be suitably selected according to the objective.

C. Base material layer The base material layer is formed of any appropriate resin. Preferably, it is a thermoplastic resin that can be co-extruded, which will be described later, and examples thereof include a polyethylene resin. Specific examples of the polyethylene resin include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMA), styrene-ethylene-butylene-styrene block polymer ( SEBS), high molecular weight polyethylene (HDPE), low molecular weight polyethylene (LDPE), and linear low molecular weight polyethylene (LLDPE). The base material layer preferably contains an ethylene-vinyl acetate copolymer.

  The ethylene-vinyl acetate copolymer preferably has a weight average molecular weight (Mw) of 10,000 to 200,000, more preferably 30,000 to 190,000. When the weight average molecular weight (Mw) of the ethylene-vinyl acetate copolymer is in such a range, the substrate layer can be formed without processing defects during coextrusion molding.

  The melt flow rate at 190 ° C. and 2.16 kgf of the ethylene-vinyl acetate copolymer is preferably 2 g / 10 min to 20 g / 10 min, more preferably 5 g / 10 min to 15 g / 10 min, and even more preferably 7 g. / 10 min to 12 g / 10 min. When the melt flow rate of the ethylene-vinyl acetate copolymer is in such a range, the base material layer can be formed without co-extrusion molding without processing defects.

  The base material layer may further contain other components as long as the effects of the present invention are not impaired. As said other component, the component similar to the other component which can be contained in the adhesive layer demonstrated by the said B term can be used, for example.

D. Production method of pressure-sensitive adhesive sheet The pressure-sensitive adhesive sheet of the present invention can be produced by any appropriate method. The method for producing the pressure-sensitive adhesive sheet of the present invention preferably includes a step of co-extruding the material forming the pressure-sensitive adhesive layer and the material forming the base material layer. By coextrusion molding, a pressure-sensitive adhesive sheet having good interlayer adhesion can be produced with a small number of steps and without using an organic solvent.

  In the co-extrusion molding, as a material for forming the pressure-sensitive adhesive layer and the base material layer, a material obtained by mixing the components of the above-described layers by any appropriate method can be used.

  As a specific method of the co-extrusion molding, for example, among at least two extruders connected to a die, a material for forming an adhesive layer on one unit and a material for forming a base material layer on another unit May be supplied, melted, extruded, and taken up by a touch roll molding method to form a laminate. When the pressure-sensitive adhesive sheet has a surface layer that can further impart heat resistance, a laminate can be formed by further adding an extruder and supplying a material for forming the surface layer from the extruder. It is preferable that the portion where the forming materials are joined at the time of extrusion is closer to the die outlet (die slip). This is because it is difficult for the formation materials to merge together in the die. Accordingly, a multi-manifold die is preferably used as the die. In addition, when a merging failure occurs, an appearance defect such as merging unevenness, specifically, a wavy appearance unevenness occurs between the extruded pressure-sensitive adhesive layer and the base material layer, which is not preferable. In addition, poor merging occurs, for example, due to a large difference in fluidity (melt viscosity) in the dies of different formation materials and a large difference in shear rate of formation materials of each layer. If a die is used, the range of material selection will be broader than other types (for example, a feed block format) for different types of forming materials having a difference in fluidity. The screw type of the extruder used for melting each forming material may be uniaxial or biaxial. There may be three or more extruders. In addition, when producing an adhesive sheet having a two-layer structure (base material layer + adhesive layer) using three or more extruders, the same forming material may be supplied to two or more adjacent extruders. For example, when three extruders are used, the same forming material can be supplied to two adjacent extruders.

  The molding temperature in the coextrusion molding is preferably 160 ° C to 220 ° C, more preferably 170 ° C to 200 ° C. Within such a range, the molding stability is excellent.

Difference in shear viscosity between the material forming the pressure-sensitive adhesive layer and the material forming the base material layer at a temperature of 180 ° C. and a shear rate of 100 sec ⁻¹ (the material forming the pressure-sensitive adhesive layer−the material forming the base material layer ) Is preferably −150 Pa · s to 600 Pa · s, more preferably −100 Pa · s to 550 Pa · s, and further preferably −50 Pa · s to 500 Pa · s. If it is such a range, the fluidity | liquidity in the die | dye of the material which forms the said adhesive layer and the base material layer will be near, and generation | occurrence | production of poor merging can be prevented. The shear viscosity can be measured with a twin capillary type extension viscometer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all. In addition, a part means a weight part.

[Example 1]
As a material for forming the base material layer, an ethylene-vinyl acetate copolymer (manufactured by Mitsui DuPont, trade name “Evaflex P-1007”) was used.
As a material for forming the pressure-sensitive adhesive layer, an amorphous propylene- (1-butene) copolymer polymerized by a metallocene catalyst (manufactured by Sumitomo Chemical Co., Ltd., trade name “Tufselen H5002”: propylene-derived structural unit 90 mol% / 1 -Butene-derived structural unit 10 mol%, Mw = 230,000, Mw / Mn = 1.8).
100 parts of the material for forming the base material layer and 100 parts of the material for forming the pressure-sensitive adhesive layer were charged into each extruder and co-extruded with T-die (extruder: manufactured by GM Engineering, Trade name “GM30-28” / T die: feed block method, extrusion temperature: 180 ° C.). A molten resin co-extruded from a die and an Si-coated PET separator (trade name “Diafoil MRF”, thickness 38 μm, manufactured by Mitsubishi Chemical Corporation) passed through a touch roll molding part, a separator and an adhesive layer After being laminated so as to be in contact with each other, it was cooled to obtain an adhesive sheet of base material layer (thickness 100 μm) / adhesive layer (thickness 30 μm) / separator (thickness 38 μm). In addition, the thickness of the base material layer and the pressure-sensitive adhesive layer was controlled by the shape of the T-die outlet.

(Comparative Example 1)
At 25 ° C., 100 parts of n-butyl acrylate, 3 parts of acrylic acid, 0.1 part of 2,2′-azobisisobutyronitrile and 100 parts of ethyl acetate were charged into a 500 ml flask. Next, while stirring, nitrogen gas was introduced into the flask for about 1 hour, and the air inside was replaced with nitrogen. Next, the flask was heated, the temperature in the flask was raised to 60 ° C., and polymerization was carried out by holding for about 6 hours while appropriately adding ethyl acetate for viscosity adjustment to obtain a polymer solution.
To 100 parts of the resulting polymer solution, 2 parts of a polyisocyanate compound (manufactured by Nippon Polyurethane Industry, trade name “Coronate L”), 0.5 part of a polyfunctional epoxy compound (trade name “Tetrad C”, manufactured by Mitsubishi Gas Chemical) Was added, and the mixture was stirred until it became homogeneous while diluting with ethyl acetate to obtain an adhesive solution.
The obtained pressure-sensitive adhesive solution was applied on a Si-coated PET separator (trade name “Diafoil MRF”, thickness 38 μm, manufactured by Mitsubishi Chemical Corporation), and dried in a drying oven at 70 ° C. and 130 ° C. for 3 minutes, respectively. Thus, a pressure-sensitive adhesive layer having a thickness of 30 μm was formed. Next, the pressure-sensitive adhesive layer and a base material layer extruded to a thickness of 100 μm (Mitsui DuPont Co., Ltd., trade name “Evaflex P-1007” (ethylene-vinyl acetate copolymer resin)) are bonded together. A pressure-sensitive adhesive sheet was obtained.

(Comparative Example 2)
A pressure-sensitive adhesive sheet was obtained in the same manner as in Comparative Example 1 except that the polyfunctional epoxy compound was changed to 3.0 parts.

[Evaluation]
The following evaluation was performed about the adhesive sheet obtained in Example 1 and Comparative Examples 1-2. The results are shown in Table 1.
(1) Adhesive strength After the obtained adhesive sheet was aged at 50 ° C. for 2 days, a mirror surface (made of silicon) of a 4-inch semiconductor wafer, a method according to JIS Z 0237 (2000) (bonding condition: 2 kg roller) 1 reciprocation, peeling speed: 300 mm / min, peeling angle 180 °).
(2) Ball tack Measured by a method according to JIS Z 0237 (tilted ball tack, tilt angle 30 degrees). The ball number of the largest held ball was taken as the ball tack, and 0 when the ball with the ball number 1 dropped.
(3) Paper Passability The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were passed through a pressure-sensitive adhesive sheet pasting machine for semiconductor (trade name “DR-3000III” manufactured by Nitto Seiki Co., Ltd.). When the pressure-sensitive adhesive sheet from which the separator has been peeled can pass through without being attached to each roll, the paper passing property is good, the paper adheres to the roll, and it is necessary to peel off the attached portion in order to pass the paper, or paper passing is difficult The case was considered bad.
(4) Back grinding property The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were attached to an 8-inch mirror wafer, and back grinding was performed to a thickness of 100 μm. The case where the back grind was completed without problems was good, and the one where the grinding water entered from the outer periphery and the wafer was cracked was regarded as defective.

  The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of Example 1 had high adhesive strength, and the ball of ball number 1 also dropped in the ball tack test. Therefore, the pressure-sensitive adhesive sheet of Example 1 was able to achieve both good paper passing properties and good back grind properties.

  On the other hand, since the pressure-sensitive adhesive sheet of Comparative Example 1 has high adhesive strength, the back grind property was excellent. However, since the tack is high, it is difficult to pass the paper, and the handleability after the separation of the separator is poor. Moreover, the pressure-sensitive adhesive sheet of Comparative Example 2 had a low tack and good paper permeability. However, due to low adhesive strength, wafer cracking occurred during back grinding. Thus, in the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2, it was difficult to achieve both paper passing properties and back grind properties.

  The pressure-sensitive adhesive sheet of the present invention can be suitably used, for example, for protecting a workpiece (semiconductor wafer or the like) when manufacturing a semiconductor device.

DESCRIPTION OF SYMBOLS 10 Base material layer 20 Adhesive material layer 100 Adhesive sheet

Claims (6)

A base material layer and an adhesive layer;
The ball number in the ball tack test of the pressure-sensitive adhesive layer is 2 or less, and
An adhesive sheet having an adhesive strength to a silicon mirror wafer of 0.3 N / 20 mm or more.   The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer contains a polyolefin resin.   The pressure-sensitive adhesive sheet according to claim 2, wherein the polyolefin-based resin contains an amorphous propylene- (1-butene) copolymer polymerized using a metallocene catalyst.   The pressure-sensitive adhesive sheet according to claim 2 or 3, wherein the polyolefin resin further comprises a crystalline polypropylene resin.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, obtained by co-extrusion of a pressure-sensitive adhesive layer forming material and a base material layer forming material.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, which is used for processing a semiconductor wafer.

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