JP2004331743A - Pressure-sensitive adhesive sheet and method for using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet which is preferably used for being adhered to the large uneven hight difference-having surface of an adherend to protect the surface, when the back surface of the adherend is processed, enables the uniform grinding of the adherend in an especially extremely thin thickness, can prevent the formation of dimples, and can profitably be produced. <P>SOLUTION: This pressure-sensitive adhesive sheet comprising a substrate, an intermediate layer formed on the substrate, and a pressure-sensitive adhesive layer formed on the intermediate layer is characterized in that the intermediate layer comprises a film formed from a non-solvent type resin and having a stress relaxation rate of ≥60% at 10 seconds after torsion stress of 20% is added. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pressure-sensitive adhesive sheet, and more particularly, to a pressure-sensitive adhesive sheet which is adhered to a front surface and is preferably used to protect the front surface during processing of a rear surface of an adherend having a large unevenness formed on the front surface.
[0002]
[Prior art]
In the grinding process of the back surface of the semiconductor wafer, the surface on which the electric circuit is formed is protected by the adhesive sheet. The height difference of the circuit by the electrode element of the normal circuit was about 5 to 20 μm. A wafer having such a normal circuit formed thereon can be sufficiently protected even by using a conventional surface protection sheet, and the circuit can be sufficiently dealt with without breaking the circuit or breaking the wafer.
[0003]
However, in recent years, IC chip mounting methods have been diversified, and there is a packaging method in which an IC chip circuit surface is disposed on a lower side. In this packaging method, a convex electrode element is formed so as to protrude from the circuit surface, and the height difference is 30 μm or more, and in some cases, the height exceeds 100 μm. The convex portion formed on the surface of such a semiconductor wafer is called a bump.
[0004]
Usually, two or more bumps are formed for one chip. In many cases, the bump pitch (the distance between bumps) is several hundred μm. Depending on the pattern of the bump pitch and the arrangement of the chips, there are dense portions where the bumps are concentrated and portions where the bump pattern is sparse. In particular, since no chips are present in the outer peripheral portion of the wafer, the bumps tend to be particularly sparse. In a place where the bumps are dense and a place where the bumps are sparse, the thickness of the wafer to which the adhesive sheet is attached varies considerably. Grinding the wafer in this state has a problem that the difference in thickness is directly generated as a variation in the thickness of the wafer after grinding.
[0005]
When the back surface of the wafer on which such bumps are formed is polished while being protected by a conventional surface protection sheet, the back surface is polished deeply according to the shape of the bumps, and the back surface is pitted (dimple). Is formed, and the thickness of the wafer becomes uneven. Further, cracks may be generated from the dimple portions, and eventually the wafer may be broken.
[0006]
Such a problem also occurs in ink (bad mark) formed for marking a defective circuit after inspection of a wafer circuit.
[0007]
For semiconductor wafers with large bumps, the hardness of the base film of the surface protection sheet was softened or the pressure-sensitive adhesive sheet was thickened, but this was not sufficient, and the above problems were still solved Was not done.
[0008]
For this reason, the intermediate layer and the pressure-sensitive adhesive layer having a specific elastic modulus, the substrate, the intermediate layer, in the surface protection sheet laminated in the order of the pressure-sensitive adhesive layer, the specific elastic modulus as the intermediate layer and the pressure-sensitive adhesive layer It has been proposed to use a resin (see Patent Document 1). Patent Document 1 describes that a film having a high stress relaxation property may be used as a substrate. When such a substrate having a high stress relaxation property is used, the residual stress is rapidly reduced, so that the above-mentioned problem caused by the internal strain can be solved. In addition, since the intermediate layer and the pressure-sensitive adhesive layer have specific elastic moduli, it is expected that the surface protection function can be sufficiently achieved even in a high bump wafer having a large surface unevenness difference.
[0009]
In recent years, the spread of IC cards has progressed, and further reduction in thickness is desired. For this reason, it has become necessary to reduce the thickness of the semiconductor chip, which was conventionally about 350 μm, to 50 to 100 μm or less.
[0010]
As a method for achieving such thinning of a chip, Patent Document 2 discloses a method of manufacturing a semiconductor chip in which a groove having a predetermined depth is formed from the front surface side of a wafer and then ground from the back surface side. . Such a process is also called a “pre-dicing method”. At the time of grinding the back surface of the wafer, a surface protection sheet is adhered to the surface of the grooved wafer in order to protect the circuit on the wafer surface and to fix the wafer (chip).
[0011]
In such a pre-dicing method, when bumps are formed on the circuit surface of the semiconductor chip, another problem occurs in addition to the back surface polishing by the usual method as described above. In the pre-dicing method, the wafer is divided into chips on a surface protection sheet at the final stage of polishing. If bumps are present on the circuit surface, it is difficult to completely adhere the periphery of each chip with the surface protection sheet, so that grinding water may infiltrate through gaps between the chips and contaminate the circuit surface.
[0012]
For this reason, the surface protection sheet used in the pre-dicing method is required to further follow the surface on which the bumps are formed, as compared with the ordinary method. As a measure to cope with such a case, it has been studied to increase the thickness of the intermediate layer of the surface protection sheet as described in Patent Document 1. By increasing the thickness of the intermediate layer, there is a possibility that the unevenness on the wafer surface is absorbed by the intermediate layer and penetration of cutting water into the circuit surface can be prevented.
[0013]
It is obvious to those skilled in the art that the intermediate layer in Patent Document 1 is formed by applying and drying a solvent-type pressure-sensitive adhesive based on its composition. In order to obtain an intermediate layer having a sufficient thickness with such a solvent-type pressure-sensitive adhesive, it is necessary to apply and dry the pressure-sensitive adhesive a plurality of times, which is inferior in economical efficiency.
[0014]
[Patent Document 1]
JP-A-2000-212530
[Patent Document 2]
JP-A-5-335411
[0015]
[Problems to be solved by the invention]
The present invention has been made in view of the prior art as described above, when the back surface of the adherend having a large difference in surface irregularities, is adhered to the surface, is preferably used to protect the surface, In particular, it is an object of the present invention to provide a pressure-sensitive adhesive sheet that can be ground with a uniform thickness even when the adherend is ground to an extremely thin thickness, can prevent the generation of dimples, and can be manufactured economically.
[0016]
[Means for Solving the Problems]
The pressure-sensitive adhesive sheet according to the present invention comprises a substrate, an intermediate layer formed thereon, and a pressure-sensitive adhesive layer formed on the intermediate layer,
The intermediate layer is made of a film formed of a solventless resin and having a stress relaxation rate of 60% or more after 10 seconds from the application of 20% torsional stress.
[0017]
Such an intermediate layer is preferably a single layer.
[0018]
Further, it is preferable that the intermediate layer is formed by forming and curing a non-solvent type energy ray-curable resin. In particular, the energy ray-curable resin is preferably a non-energy ray polymerizable oligomer and an energy ray polymerizable monomer. It preferably comprises
[0019]
Further, when the pressure-sensitive adhesive layer is made of an energy-ray-curable pressure-sensitive adhesive, the thickness of the pressure-sensitive adhesive layer is preferably 10% or more of the thickness of the intermediate layer.
[0020]
The pressure-sensitive adhesive sheet of the present invention is preferably used as a surface protection sheet. Specifically, the pressure-sensitive adhesive sheet is adhered to a surface of an adherend as a surface protection sheet, and the back surface thereof is protected while protecting the surface of the adherend. It is preferably used in a process including a step of performing processing.
[0021]
In particular, the pressure-sensitive adhesive sheet of the present invention is preferably used as a circuit surface protection sheet at the time of grinding the back surface of a semiconductor wafer on which a circuit having bumps is formed on the surface. It is preferably used in a process including a step of attaching a surface protection sheet to the surface of a semiconductor wafer formed on the front surface and grinding the back surface while protecting the circuit surface of the semiconductor wafer.
[0022]
Furthermore, the pressure-sensitive adhesive sheet of the present invention is preferably used particularly in chipping of a high bump wafer by a pre-dicing method, and specifically,
Forming a groove with a cutting depth shallower than the wafer thickness from the semiconductor wafer surface on which the circuit having the bump is formed,
On the circuit forming surface, affix the pressure-sensitive adhesive sheet as a surface protection sheet,
After that, by grinding the back surface of the semiconductor wafer, the thickness of the wafer is reduced, and finally, the wafer is divided into individual chips.
It is preferably used for a method of manufacturing a semiconductor chip including a step of picking up a chip.
[0023]
According to the present invention, the back surface of the adherend having a large difference in surface irregularities is adhered to the front surface and is preferably used to protect the surface, and particularly, the adherend is ground to an extremely thin thickness. The present invention provides an adhesive sheet which can be ground with a uniform thickness, can prevent the generation of dimples, and can be manufactured economically, and a method for manufacturing a semiconductor chip using the same.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described more specifically.
[0025]
The pressure-sensitive adhesive sheet according to the present invention has a substrate, an intermediate layer, and a pressure-sensitive adhesive layer laminated in this order.
[0026]
The pressure-sensitive adhesive layer can be formed of various conventionally known pressure-sensitive pressure-sensitive adhesives. Such an adhesive is not limited at all, and for example, an adhesive such as a rubber-based, acrylic-based, silicone-based, or polyvinyl ether is used. In addition, an energy-ray-curable, heat-foamable, or water-swellable pressure-sensitive adhesive can also be used.
[0027]
As the energy ray-curable (energy beam-curable, ultraviolet ray-curable, electron beam-curable) type pressure-sensitive adhesive, it is particularly preferable to use an ultraviolet ray-curable pressure-sensitive adhesive. As the water-swellable pressure-sensitive adhesive, for example, those described in JP-B-5-77284 and JP-B-6-101455 are preferably used.
[0028]
The energy ray-curable pressure-sensitive adhesive generally comprises an acrylic pressure-sensitive adhesive and an energy ray-polymerizable compound as main components.
[0029]
As the energy ray polymerizable compound used in the energy ray-curable pressure-sensitive adhesive, for example, a three-dimensional network can be formed by light irradiation as disclosed in JP-A-60-196965 and JP-A-60-223139. Low molecular weight compounds having at least two or more photopolymerizable carbon-carbon double bonds in the molecule are widely used, specifically, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, pentaerythritol Tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate or 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol Diacrylates, such as the commercially available oligoester acrylates are used.
[0030]
Further, as the energy ray polymerizable compound, a urethane acrylate oligomer can be used in addition to the acrylate compound as described above. The urethane acrylate oligomer includes a polyol compound such as a polyester type or a polyether type, and a polyvalent isocyanate compound such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and 1,3-xylylene diisocyanate. Acrylate or methacrylate having a hydroxyl group, such as 2-hydroxyethyl acrylate or 2-hydroxy, is added to a terminal isocyanate urethane prepolymer obtained by reacting a 1,4-xylylene diisocyanate, diphenylmethane 4,4-diisocyanate, or the like. Ethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate Obtained by.
[0031]
The mixing ratio of the acrylic pressure-sensitive adhesive and the energy ray-polymerizable compound in the energy ray-curable pressure-sensitive adhesive is such that the energy ray-polymerizable compound is 50 to 200 parts by weight, preferably 50 to 200 parts by weight, per 100 parts by weight of the acrylic pressure-sensitive adhesive. It is desirable to use 150 parts by weight, particularly preferably in an amount in the range of 70 to 120 parts by weight. In this case, the resulting pressure-sensitive adhesive sheet has a large initial adhesive force, and the adhesive force is significantly reduced after irradiation with energy rays. Therefore, peeling at the interface between the wafer and the energy ray-curable pressure-sensitive adhesive layer after the backside grinding is completed is facilitated.
[0032]
Further, the energy ray-curable pressure-sensitive adhesive may be formed from an energy ray-curable copolymer having an energy ray-polymerizable group in a side chain. Such an energy ray-curable copolymer has the property of having both adhesiveness and energy ray-curability. The details of the energy ray-curable copolymer having an energy ray polymerizable group in the side chain are described in, for example, JP-A-5-32946 and JP-A-8-27239.
[0033]
By mixing the photopolymerization initiator into the energy ray-curable pressure-sensitive adhesive, the polymerization curing time by light irradiation and the amount of light irradiation can be reduced.
[0034]
Examples of such a photopolymerization initiator include photoinitiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. Specifically, 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethyl thiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β- Chloranthraquinone can be exemplified.
[0035]
The amount of the photopolymerization initiator used is preferably 0.05 to 15 parts by weight, more preferably 0.1 to 10 parts by weight, and particularly preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the total of the pressure-sensitive adhesive. Department.
[0036]
The acrylic energy ray-curable pressure-sensitive adhesive as described above has a sufficient adhesive strength to the wafer before the energy ray irradiation, and the adhesive strength is significantly reduced after the energy ray irradiation. That is, before the energy beam irradiation, the pressure-sensitive adhesive sheet and the wafer are brought into close contact with a sufficient adhesive force to enable surface protection, and after the energy beam irradiation, the wafer can be easily separated from the ground wafer.
[0037]
In the pressure-sensitive adhesive sheet of the present invention, the intermediate layer is formed from a solventless resin. By using a solventless resin, a thicker intermediate layer can be formed by a simpler operation than in the case of using a solvent resin. That is, when a thick film is obtained using a solvent-type resin, it is necessary to apply the resin repeatedly, but with a solventless resin, a coating film having a sufficient thickness can be obtained by one application, and the work efficiency is improved. An adhesive sheet can be manufactured well. Since such an intermediate layer is formed by one application, the intermediate layer has a single-layer structure, and no interface is observed in the layer. On the other hand, when a thick coating film is formed using a solvent-type resin, since application and drying of the resin will be repeated a plurality of times, an interface as a trace of overcoating is observed in the layer. .
[0038]
The resin constituting the intermediate layer has a stress relaxation rate of 60% or more, preferably 70% or more, more preferably 80% or more after 10 seconds from the application of 20% torsional stress. The higher the stress relaxation rate, the better, and the upper limit is theoretically 100%, and may be 99.9%, 99% or 95% in some cases. Many of the materials exhibiting such physical properties exhibit adhesiveness. For this reason, in the present invention, a material supplied as a solventless pressure-sensitive adhesive can be preferably used as the intermediate layer, but is not limited thereto.
[0039]
When such a resin having a high stress relaxation rate is used as the intermediate layer of the pressure-sensitive adhesive sheet, the strain stress caused by the pressure applied to the adherend due to the unevenness is quickly attenuated after the application. Accordingly, the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet closely follows and adheres to the irregularities on the surface of the adherend.
[0040]
Further, the upper surface of the intermediate layer, that is, the surface on the side where the pressure-sensitive adhesive layer is provided, in order to improve the adhesion with the pressure-sensitive adhesive, may be subjected to corona treatment or provided with another layer such as a primer layer or a barrier layer. Good.
[0041]
The material of the intermediate layer is not particularly limited as long as it is a solventless resin satisfying the above-mentioned properties, and examples thereof include forms such as an energy ray-curable resin and a hot melt adhesive. Among these, a solventless energy ray-curable resin and a hot melt pressure-sensitive adhesive are used from the viewpoint of easy adjustment of physical properties.
[0042]
When the intermediate layer is formed of a non-solvent type energy ray-curable resin, the above physical properties mean physical properties relating to a film formed by forming and curing a non-solvent type energy ray-curable resin.
[0043]
Examples of the energy ray-curable resin of the solventless pressure-sensitive adhesive include a mixture of a non-energy ray-curable polymer and an energy ray-polymerizable diluent (monomer), an energy ray-polymerizable oligomer, A blend with an energy beam polymerizable monomer, and a blend with a non-energy beam polymerizable oligomer and an energy beam polymerizable monomer are exemplified.
[0044]
Energy ray-curable solventless adhesives are generally designed to increase the number of crosslink points, and become tacky by irradiation with energy rays, but have poor stress relaxation properties. On the other hand, an energy ray-curable resin containing a non-energy ray polymerizable oligomer and an energy ray polymerizable monomer is preferable because it has relatively few crosslinking points and easily satisfies the above-mentioned properties.
[0045]
The non-energy beam polymerizable oligomer is a molecule having substantially no energy beam polymerizable double bond and having a weight average molecular weight of 1,000 to 10,000, preferably 2,000 to 9000, particularly preferably 3,000 to 8,000. The oligomer has a bonding site such as a urethane bond, a carbonate bond, an ester bond, an ether amide bond, and an ester amide bond in the molecule, and-(CH ₂ ) _n -,-(CH ₂ CH ₂ O) _n And para-substituted aromatic groups, linear biphenyl, cyclohexyl, substituted naphthyl and the like. Therefore, the non-energy ray polymerizable oligomer is composed of an oligomer obtained by polymerizing a monomer having the above-mentioned bonding unit, and is composed of, for example, a urethane oligomer, a carbonate oligomer, an ester oligomer, an amide oligomer, and the like.
[0046]
The non-energy beam polymerizable oligomer plasticizes the polymer component polymerized by the energy beam polymerizable monomer without contributing to the curing reaction, and functions to give flexibility to the cured intermediate layer. By appropriately plasticizing the cured polymer component, the intermediate layer has a high stress relaxation rate.
[0047]
The energy beam polymerizable monomer has an energy beam polymerizable double bond in the molecule, and is polymerized into a polymer component by the energy beam to form a skeleton of the intermediate layer. In particular, in the present invention, a monofunctional acrylic ester compound having a relatively bulky group is preferably used in order to easily increase the stress relaxation rate of the intermediate layer.
[0048]
Specific examples of such an energy ray polymerizable monomer include isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxy (meth) acrylate, and cyclohexyl (meth) Alicyclic compounds such as acrylates and adamantane (meth) acrylates;
Examples include aromatic compounds such as phenylhydroxypropyl acrylate, benzyl acrylate, and phenol-ethylene oxide-modified acrylate, and heterocyclic compounds such as tetrahydrofurfuryl (meth) acrylate, morpholine acrylate, N-vinylpyrrolidone, and N-vinylcaprolactam. Moreover, you may use a polyfunctional (meth) acrylate as needed.
[0049]
The energy ray polymerizable monomer is used in an amount of preferably 5 to 900 parts by weight, more preferably 10 to 500 parts by weight, and particularly preferably 30 to 200 parts by weight based on 100 parts by weight of the non-energy ray polymerizable oligomer. Can be
[0050]
By mixing a photopolymerization initiator into the energy ray polymerizable resin composition containing the non-energy ray polymerizable oligomer and the energy ray polymerizable monomer as essential components, the polymerization curing time by light irradiation and the amount of light irradiation can be reduced. can do.
[0051]
Examples of such a photopolymerization initiator include those similar to the photopolymerization initiator blended in the energy ray-curable pressure-sensitive adhesive described above.
[0052]
The amount of the photopolymerization initiator used is preferably 0.05 to 15 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the total of the non-energy ray polymerizable oligomer and the energy ray polymerizable monomer. And particularly preferably 0.5 to 5 parts by weight.
[0053]
The non-energy beam polymerizable oligomer is a component that gives flexibility to the intermediate layer without contributing to the curing reaction, and the energy beam polymerizable monomer is a component that polymerizes and hardens to give the intermediate layer an appropriate hardness. Therefore, by appropriately selecting the types of the non-energy beam polymerizable oligomer and the energy beam polymerizable monomer and the mixing ratio thereof, physical properties such as a stress relaxation rate, an elastic modulus, and a cohesive force of the intermediate layer can be adjusted.
[0054]
As a general tendency, when the crosslink density is lowered, or when a low-functional energy ray polymerizable oligomer is used, the stress relaxation rate increases.
[0055]
The energy ray-curable resin has poor adhesion (keying) of a cured film due to volume shrinkage due to curing. For this reason, an adhesion improver is blended with the energy ray-curable pressure-sensitive adhesive for the purpose of improving the adhesion to the substrate. As the adhesion improver, a relatively low molecular weight polymer or oligomer such as polyester or urethane can be used.
[0056]
Further, the intermediate layer may be formed from a hot melt pressure-sensitive adhesive satisfying the above-described physical properties. Various hot-melt adhesives such as acrylic, rubber, urethane, ester, and polyamide can be used without any particular limitation as long as the above physical properties are satisfied.
[0057]
As the hot melt adhesive, a styrene block copolymer such as a styrene / butadiene / styrene block copolymer and a styrene / isoprene / styrene block copolymer is particularly preferable. Depending on the amount of the styrene block, the stress relaxation property can be reduced without lowering the cohesive force.
[0058]
A layer having a high stress relaxation rate usually has a small cohesive force, lacks shape retention, and is likely to protrude from the end of the pressure-sensitive adhesive sheet. Since the thickness of the intermediate layer in the pressure-sensitive adhesive sheet of the present invention is set, this phenomenon is more remarkable. For this reason, it is preferable to set the intermediate layer so that the stress relaxation rate is high and the cohesive force is high. The cohesive force of the intermediate layer preferably shows a holding force in JIS Z0237 of 10,000 seconds or more, more preferably 50,000 seconds or more. As described above, since a substance having a high stress relaxation rate often shows tackiness, the intermediate layer of such a sheet can measure the holding power.
[0059]
As the substrate, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, Transparent films such as polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, and polyimide film are used. Can be These crosslinked films can also be used. Further, these laminated films may be used. Further, in addition to the above-mentioned transparent films, opaque films, fluororesin films, or the like obtained by coloring them can be used.
[0060]
The pressure-sensitive adhesive sheet according to the present invention is manufactured by providing a pressure-sensitive adhesive layer on an intermediate layer formed on the above-described substrate. When the pressure-sensitive adhesive layer is made of an energy-ray-curable pressure-sensitive adhesive, the substrate and the intermediate layer need to be transparent.
[0061]
When the pressure-sensitive adhesive sheet of the present invention is used in a manufacturing process of a semiconductor device by a pre-dicing method, a substrate is used to prevent chip cracks at the time of chipping by back surface grinding and to prevent shrinkage of a kerf width of divided chips. It is preferable to use a relatively rigid film such as a polyethylene terephthalate film or a polyethylene naphthalate film. However, if the base material is rigid, the stress relaxation rate becomes small, and it becomes difficult to absorb the unevenness of the wafer due to the physical properties of the base material layer. Therefore, the role of the intermediate layer is more important.
[0062]
In the pressure-sensitive adhesive sheet of the present invention, the thickness of the substrate is preferably from 10 to 1000 μm, more preferably from 30 to 500 μm, and particularly preferably from 50 to 300 μm.
[0063]
The thickness of the intermediate layer is preferably in the range of 50 to 500 μm, more preferably 100 to 400 μm, and particularly preferably 150 to 300 μm. Further, the thickness of the pressure-sensitive adhesive layer is usually about 5 to 100 µm, preferably about 10 to 80 µm, and particularly preferably about 20 to 60 µm, though it depends on the material.
[0064]
Therefore, the total thickness of the intermediate layer and the pressure-sensitive adhesive layer is preferably in the range of 55 to 600 μm, more preferably 110 to 480 μm, and particularly preferably 170 to 360 μm.
[0065]
When the intermediate layer is made of a solventless pressure-sensitive adhesive, the composition is similar to the material constituting the pressure-sensitive adhesive layer, so that the components may be compatible with each other and migrate between the layers. In that case, there is a possibility that necessary properties may not be obtained. Therefore, a barrier layer is provided between the intermediate layer and the pressure-sensitive adhesive layer, or the thickness of a layer containing a large amount of a component (for example, a photopolymerization initiator) which is easily transferred is increased. Can be dealt with.
[0066]
When the pressure-sensitive adhesive layer is of an energy ray-curable type, the photopolymerization initiator on the pressure-sensitive adhesive layer side easily moves to the intermediate layer. For this reason, the thickness of the pressure-sensitive adhesive layer is preferably 10% or more, more preferably 15% to 100% of the thickness of the intermediate layer.
[0067]
The total thickness of the intermediate layer and the pressure-sensitive adhesive layer is appropriately selected in consideration of the bump height of the adherend to which the pressure-sensitive adhesive sheet is adhered, the bump shape, the pitch of the bump interval, and the like. The total thickness of the layer and the pressure-sensitive adhesive layer is desirably selected so as to be 110% or more, preferably 130 to 500% of the bump height. When the total thickness of the intermediate layer and the pressure-sensitive adhesive layer is selected in this manner, the pressure-sensitive adhesive sheet follows the unevenness of the circuit surface, and the unevenness difference can be eliminated.
[0068]
In the pressure-sensitive adhesive sheet of the present invention, an intermediate layer is formed by applying a solvent-free resin for forming an intermediate layer on a base material and then curing the resin by a required means. From an economical point of view, the intermediate layer is made of a solvent-free resin using a roll coater, knife coater, roll knife coater, fountain die coater, slot die coater, reverse coater, etc. It is preferable to perform the coating in one thick coating. Subsequently, on the intermediate layer, a pressure-sensitive adhesive layer is formed by coating to an appropriate thickness by a known coating device and drying, and then, if necessary, a release sheet is laminated on the pressure-sensitive adhesive layer. can get.
[0069]
The pressure-sensitive adhesive sheet of the present invention is used for surface protection of various articles and for temporary fixing during precision processing. In particular, the pressure-sensitive adhesive sheet of the present invention is preferably used as a surface protection sheet for an article having a large surface unevenness difference.
[0070]
When used as a surface protection sheet, it is particularly preferable to apply the pressure-sensitive adhesive sheet to the surface of an adherend as a surface protection sheet, and to protect the surface of the adherend while processing the back surface thereof. Used.
[0071]
Here, as the adherend, a semiconductor wafer on which a circuit having bumps is formed on the front surface is particularly preferable, and as the back surface processing, a back surface grinding of a semiconductor wafer on which a circuit having bumps is formed on the front surface is performed. Particularly preferred. Here, the height of the bump is not particularly limited, but according to the method of the present invention, a semiconductor wafer on which a circuit having a bump having a height of 40 μm or more, further 50 to 400 μm, and particularly 70 to 300 μm is formed. Can also be processed.
[0072]
That is, the pressure-sensitive adhesive sheet of the present invention is preferably used as a circuit surface protection sheet at the time of grinding the back surface of a semiconductor wafer on which a circuit having bumps is formed on the surface. It is preferably used in a process including a step of attaching a surface protection sheet to the surface of a semiconductor wafer formed on the front surface and grinding the back surface while protecting the circuit surface of the semiconductor wafer.
[0073]
The thickness of the semiconductor wafer after the back surface grinding is not particularly limited, but is preferably about 10 to 300 μm, and particularly preferably about 25 to 200 μm.
[0074]
Furthermore, the pressure-sensitive adhesive sheet of the present invention is preferably used particularly in chipping of a high bump wafer by a pre-dicing method, and specifically,
Forming a groove with a cutting depth shallower than the wafer thickness from the semiconductor wafer surface on which the circuit having the bump is formed,
On the circuit forming surface, affix the pressure-sensitive adhesive sheet as a surface protection sheet,
After that, by grinding the back surface of the semiconductor wafer, the thickness of the wafer is reduced, and finally, the wafer is divided into individual chips.
It is preferably used for a method of manufacturing a semiconductor chip including a step of picking up a chip.
[0075]
More specifically, it is used in a method for manufacturing a semiconductor chip comprising the following steps.
[0076]
First step: A groove having a predetermined depth is formed from the wafer surface along a cutting position of the wafer which partitions a plurality of circuits.
[0077]
Second step: The pressure-sensitive adhesive sheet of the present invention is attached so as to cover the entire surface of the wafer.
[0078]
Third step: The bottom of the groove is removed, and the back surface of the wafer is ground to a predetermined thickness to be divided into individual chips. At the time of grinding, grinding is performed while supplying water (grinding water) to the grinding surface to remove grinding dust and grinding heat. At this time, by using the pressure-sensitive adhesive sheet of the present invention, high adhesion between the chip and the pressure-sensitive adhesive layer can be obtained, so that there is no infiltration of grinding water into the circuit surface and contamination of the chip can be prevented.
[0079]
Thereafter, when the pressure-sensitive adhesive layer is formed from an energy-ray-curable pressure-sensitive adhesive, the chip is picked up by a predetermined method by irradiating with energy rays to reduce the adhesive force. Further, prior to picking up the chips, the chips aligned in a wafer shape may be transferred to another adhesive sheet, and then the chips may be picked up.
[0080]
【The invention's effect】
In the pressure-sensitive adhesive sheet of the present invention, since the intermediate layer is formed from a solventless resin as described above, an intermediate layer having a sufficient thickness can be obtained by one application operation, and the production cost of the pressure-sensitive adhesive sheet can be reduced. Can be reduced. In addition, since the intermediate layer satisfies the specific physical properties, according to the present invention, during the back surface processing of the adherend having a large difference in surface irregularities, the intermediate layer is adhered to the surface and is preferably used to protect the surface, In particular, an adhesive sheet which can be ground with a uniform thickness even when the adherend is ground to an extremely thin thickness and which can prevent the occurrence of dimples is provided, and a method of manufacturing a semiconductor chip using the adhesive sheet is provided. .
[0081]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0082]
In the following Examples and Comparative Examples, “backside polishing suitability test”, “elastic modulus measurement and stress relaxation rate measurement”, “grinding water contamination”, “retention force measurement”, and “keying with substrate” are as follows. Was evaluated as follows.
(1) Backside polishing suitability test
Bad marks formed by the following dot-shaped printing were used as bumps, which were formed on a 5-inch mirror wafer. An adhesive sheet was adhered to the surface of the wafer on which the bad mark was formed, and half-cut dicing of 220 μm in a size of 10 mm × 10 mm was performed, and the chip was polished to a total thickness of 200 μm from the opposite surface to form a chip. The wafer shape, polishing conditions, and evaluation method are as follows.
・ Wafer shape
Wafer diameter: 5 inches
Wafer thickness (thickness of dot-unprinted part): 650-700 μm
Dot diameter: 500-600 μm
Dot height: 100 μm
Dot pitch: 10mm interval (printing all over)
・ Backside polishing conditions
Finish thickness: 200μm
Polishing device: DFG850, manufactured by Disco Corporation
Dicer: Disco DFD641
·Evaluation method
By observing the polished wafer back surface, if there is no crack or dent, or if there is a dent, the maximum depth of the dent is less than 2 μm is “good”, and the maximum depth of the dent is 2 μm or more. Those that occurred were determined to be "poor."
(2) Elastic modulus measurement and stress relaxation rate measurement
-Device used: RDA II manufactured by Rheometric (Torsion shearing method)
Measurement method: The dynamic viscoelasticity was measured for the intermediate layer formed by using the energy ray-curable resin after the irradiation with the energy ray, and for all the other adhesives before the irradiation with the energy ray. For the elastic modulus, the elastic modulus at 23 ° C. at a frequency of 1 Hz was measured, and for the stress relaxation rate, a numerical value was determined based on the ratio of the elastic modulus immediately after the start of the measurement to the relaxation elastic modulus 10 seconds after applying a stress having a twist amount of 20%.
(3) Grinding water contamination
The pressure-sensitive adhesive sheet was separated from the printed surface of the wafer by the method (1), and the surface was observed with a microscope. A sample in which no contamination by grinding water was observed was rated "good", and a sample in which contamination was slightly observed was rated "poor".
(4) Holding force
In Examples and Comparative Examples, a laminated sheet of a base material and an intermediate layer was prepared without providing an adhesive layer, and the intermediate layer was regarded as an adhesive layer and measured in accordance with JIS Z0237.
(5) Keying with substrate
In the example or the comparative example, a laminated sheet of the base material and the intermediate layer was prepared without providing the pressure-sensitive adhesive layer, and a cutout of 0.5 mm square was provided on the intermediate layer side at 20 × 20. A cellophane tape is stuck to the cut surface of the intermediate layer and sufficiently adhered, and then the cellophane tape is peeled off. Keying with the substrate was evaluated by the ratio of the number of intermediate layers remaining on the substrate without being peeled off from the cellophane tape.
[0083]
Embodiment 1
50 parts by weight of a urethane oligomer having a weight average molecular weight of 5000 and having no reactive group (manufactured by Arakawa Chemical Co., Ltd.), 10 parts by weight of a polyester oligomer as an adhesion improver, 40 parts by weight of phenylhydroxypropyl acrylate, and 1 part by weight as a photopolymerization initiator. And 2.0 parts by weight of -hydroxycyclohexylphenyl ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals) to give an energy ray-curable resin composition.
[0084]
The obtained resin composition was applied to a PET (50 μm) / polyethylene (25 μm) bonded product (Ajiya Aluminum Co., Ltd.) obtained by subjecting a polyethylene terephthalate (PET) side to a corona discharge treatment by a fountain die method. Coating was performed so as to have a thickness of 210 μm to form a resin composition layer. Immediately after coating, after semi-curing the resin using a high-pressure mercury lamp, the same PET film is further laminated on the resin composition layer, and then the resin composition layer is cross-linked and cured using a high-pressure mercury lamp. Thus, an intermediate layer having a thickness of 210 μm was formed.
[0085]
Acrylic pressure-sensitive adhesive (copolymer of 2-ethylhexyl acrylate and hydroxyethyl acrylate, with 80% IEM (isocyanatoethyl methacrylate) added to hydroxy groups of hydroxyethyl acrylate) on the intermediate layer of this sheet. An adhesive composition obtained by mixing 100 parts by weight, 1 part by weight of a curing agent (diisocyanate), and 3.1 parts by weight of a photopolymerization initiator (Irgacure 184, manufactured by Ciba Specialty Chemicals) is applied. After drying, a pressure-sensitive adhesive layer having a thickness of 40 μm was formed to obtain a pressure-sensitive adhesive sheet.
[0086]
The physical properties of the intermediate layer and the pressure-sensitive adhesive layer were measured as described above, and the evaluation of the back surface polishing suitability of the pressure-sensitive adhesive sheet was performed as described above. Table 1 shows the results.
[0087]
Embodiment 2
The same evaluation as in Example 1 was performed except that the polyester oligomer as the adhesion improver was not used. Table 1 shows the results.
[0088]
[Comparative Example 1]
The intermediate layer is made of a non-energy beam polymerizable oligomer and an energy beam polymerizable monomer, and is made of a solventless pressure-sensitive adhesive (a product of Dainichi Seika Kogyo Co., Ltd., PM-654F, urethane acrylate) made of an energy beam polymerizable oligomer. The same evaluation as in Example 1 was performed, except that the evaluation was changed to. Table 1 shows the results.
[0089]
[Table 1]

Claims (8)

A substrate, an intermediate layer formed thereon, and an adhesive sheet comprising an adhesive layer formed on the intermediate layer,
The pressure-sensitive adhesive sheet, wherein the intermediate layer is formed of a film formed of a solventless resin and having a stress relaxation rate of 60% or more after 10 seconds from the application of 20% torsional stress. The pressure-sensitive adhesive sheet according to claim 1, wherein the intermediate layer is a single layer. The pressure-sensitive adhesive sheet according to claim 1, wherein the intermediate layer is formed by forming and curing a solvent-free energy ray-curable resin. The pressure-sensitive adhesive sheet according to claim 3, wherein the energy ray-curable resin comprises a non-energy ray polymerizable oligomer and an energy ray polymerizable monomer. The pressure-sensitive adhesive sheet according to claim 3, wherein the pressure-sensitive adhesive layer is made of an energy ray-curable pressure-sensitive adhesive, and the thickness of the pressure-sensitive adhesive layer is 10% or more of the thickness of the intermediate layer. A step of attaching the pressure-sensitive adhesive sheet according to any one of claims 1 to 5 to a surface of an adherend as a surface protection sheet, and performing a back surface processing while protecting the surface of the adherend. How to use adhesive sheet. A pressure-sensitive adhesive sheet according to any one of claims 1 to 5, which is attached as a surface protection sheet to a surface of a semiconductor wafer on which a circuit having bumps is formed on a front surface thereof, while protecting a circuit surface of the semiconductor wafer and a back surface thereof. A method for processing a semiconductor wafer, comprising a step of performing grinding. Forming a groove with a cutting depth shallower than the wafer thickness from the surface of the semiconductor wafer on which a circuit having bumps is formed,
Affixing the pressure-sensitive adhesive sheet according to any one of claims 1 to 5 as a surface protection sheet to the circuit forming surface,
After that, by grinding the back surface of the semiconductor wafer, the thickness of the wafer is reduced, and finally, the wafer is divided into individual chips.
A method for manufacturing a semiconductor chip, comprising a step of picking up a chip.