JP5546518B2 - Adhesive tape for grinding brittle wafer back surface and grinding method using the same - Google Patents

Description

  The present invention relates to an adhesive tape for processing brittle wafers used when grinding brittle wafers such as sapphire wafers, and a grinding method using the same. More specifically, the present invention relates to a brittle wafer processing pressure-sensitive adhesive tape used for protecting the wafer surface in a back grinding process of a brittle wafer such as a sapphire wafer during the manufacture of a light emitting diode.

In recent years, the demand for light-emitting diodes (hereinafter also referred to as “LEDs”) as a new light source is rapidly increasing. Since LEDs have low power consumption, long life, and small size, they can be used as an illumination source to replace incandescent lamps and fluorescent lamps. The use of equipment is expanding.
As wafers for forming LEDs, brittle wafers such as sapphire are mainly used. In the LED manufacturing process, for example, a light emitting layer such as gallium nitride (hereinafter referred to as GaN) is epitaxially grown on a sapphire wafer, and the back surface of the substrate is polished to obtain a thin film wafer. For example, a process for mounting and implementing the method is employed (see Patent Document 1).

  In a conventional semiconductor device manufacturing process using a silicon wafer or the like, a wafer processing adhesive tape for surface protection is bonded to the element forming surface side of the wafer, and a vacuum wheel is attached to the chuck table together with the tape to grindstones such as diamond wheels. Is used to grind the backside of the wafer and grind it to the desired thickness. The tape used in this method is composed of a base resin film layer and an adhesive layer, and the base resin film layer is an ethylene vinyl acetate copolymer (hereinafter also referred to as EVA) or polyethylene (hereinafter also referred to as PE). ) And other polyolefin resins, and acrylic resins are often used as pressure-sensitive adhesive layers.

  In contrast, sapphire wafers are extremely hard and brittle materials compared to silicon wafers used in general semiconductor devices, and are said to be difficult to grind. For this reason, since it takes a lot of time to reduce the thickness of a sapphire wafer having a thickness of 300 μm or more to a thickness of 100 μm or less only by grinding, a grinding method unique to a sapphire wafer has been proposed (see Patent Document 2).

Furthermore, due to the difference in thermal expansion coefficient between the sapphire substrate and the GaN formed on the substrate, the sapphire wafer for LED is very easy to warp. Furthermore, if the rigidity of sapphire decreases and the warpage becomes very large by grinding to a thin film, not only the handling property in the process is deteriorated, but also the wafer may be damaged in the worst case.
Since the wafer processing adhesive tape for silicon wafer grinding has a certain degree of flexibility, it can absorb the impact during back grinding. However, since the sapphire wafer is very hard as described above, a large stress is generated during grinding. When a sapphire wafer is ground with a conventional wafer processing adhesive tape for grinding silicon wafers, the sapphire wafer deforms following the sapphire wafer due to large deformation caused by stress, and the sapphire wafer breaks due to its brittleness. And cracks occur.

Further, the warpage amount when grinding a 4-inch diameter sapphire wafer, which is currently mainstream, using a general wafer processing adhesive tape used for backside grinding of silicon wafers, is 30 mm or more. On the other hand, the amount of warpage when a 4-inch diameter silicon wafer is cut in the same way is 1 mm or less, and even with an 8-inch diameter wafer, which is currently mainstream, the amount of warpage is 10 mm or less. Recognize.
Further, the wafer being ground is vacuum-sucked on the chuck table with the tape surface down, and the back surface of the wafer is ground. When the warp of the thin-film ground wafer is large and the adhesive force of the wafer processing adhesive tape is small, the adhesive tape is easily peeled off from the outer periphery of the wafer. Surface contamination and cracking of the sapphire wafer may occur.
For the above reasons, it is difficult to use a conventional surface protection tape for a silicon wafer as an adhesive tape for processing a brittle wafer such as a sapphire wafer. Therefore, a method of fixing and processing a sapphire wafer with wax (for example, see Non-Patent Document 1) and a method using a fixing jig (see Patent Document 3) have been proposed.

In the process of fixing the wafer surface with wax, first, a sapphire wafer is fixed to the substrate with wax, and processing such as grinding and polishing is performed. After these steps are completed, the wafer is peeled off from the substrate by subjecting the wafer to a heating step, and further washed with wax using an organic solvent, and then attached to the ring frame, followed by dicing and the like. It is carried to the process.
However, in the method of fixing the wafer to the substrate with the above-mentioned wax, the wax adhering to the wafer or the substrate has to be washed, so that the process becomes complicated. Further, when a wafer is cleaned using a solvent, defects may occur due to wax remaining on the wafer, and the solvent itself may adversely affect the environment.

  On the other hand, Patent Literature 4 describes a method for grinding a sapphire wafer having a step of attaching a protective tape to the surface of a semiconductor layer formed on a sapphire wafer substrate. However, this document does not specifically describe what kind of tape should be used and its technical means. In addition, a semiconductor wafer surface protecting pressure-sensitive adhesive tape whose tensile elastic modulus of the base film is not less than a specific value has been proposed (see, for example, Patent Documents 5 and 6). When these tapes are used for a silicon wafer or the like, since the base film has high rigidity, the warpage of the wafer after thin film grinding can be improved. However, even when the adhesive tape described in these documents is used for a sapphire wafer which is very brittle compared to a silicon wafer, it cannot be ground well, and even when it can be ground into a thin film, it often breaks during grinding.

  As a method for suppressing the warp of the sapphire wafer, a method using a fixing jig has been proposed (Patent Document 7). In this method, a sapphire wafer and a tape are fixed to an annular frame, and processing is performed while applying a tension in the radial direction during grinding. In this method, the warp can be suppressed by the correction by the annular frame and the tension, but the technical means of what kind of tape can be applied is not specifically described. For this reason, there has been a demand for a tape that can handle thin film grinding by processing using an annular frame.

JP 2007-266589 A JP 2003-245847 A JP 2007-48920 A JP 2010-46744 A JP 2010-34379 A JP 2007-221054 A Japanese Unexamined Patent Publication No. 2011-40631

Keiichi Hatakeyama, “Full Automation of Thinning for LED Substrate”, SEMICONDUCTOR International Japan Edition, 2009.11, pp. 14-18

In the present invention, in the step of grinding the back surface of a brittle wafer such as a sapphire wafer, an adhesive tape is adhered to the element circuit surface (including the light emitting layer surface) of the brittle wafer and also adhered to the annular frame and fixed. It is an object of the present invention to provide an adhesive tape that can be processed even when the brittle wafer is thinned in the step of grinding the wafer back surface by supporting, and a method for grinding the back surface of a sapphire wafer using the same.
More specifically, the present invention provides a brittle wafer processing pressure-sensitive adhesive tape and a grinding method capable of grinding without causing the brittle wafer to be thinned without cracking or cracking of the brittle wafer and peeling of the pressure-sensitive adhesive tape on the outer periphery of the brittle wafer. Is an issue.

As a result of intensive studies on the above-mentioned problems, the present inventors have determined that the adhesive strength of the pressure-sensitive adhesive tape before radiation curing in the brittle wafer backside grinding tape in which the radiation-curable pressure-sensitive adhesive layer is formed on the base resin film. And finding that the contact angle with the pure water on the surface of the pressure-sensitive adhesive layer, and further the amount of compression displacement of the pressure-sensitive adhesive tape before radiation curing is important in order to achieve the above-mentioned problems, It has been found that the above problems can be solved. The present invention has been made based on the findings.
That is, the means for solving the above-described problems of the present invention are as follows.
(1) An adhesive tape for brittle wafer backside grinding having a radiation curable adhesive layer on a base resin film, the adhesive force of the adhesive layer on the mirror surface of a silicon wafer in the adhesive tape before radiation curing Is 2.0 to 29.8 N / 25 mm, the contact angle with the pure water on the surface of the pressure-sensitive adhesive layer is 85 ° or more, and the compression displacement amount before radiation curing in the pressure-sensitive adhesive tape is 150 μm or less. An adhesive tape for grinding a back surface of a brittle wafer.
(2) In (1), the pressure-sensitive adhesive constituting the ray-curing property in the pressure-sensitive adhesive layer is a (meth) acrylic pressure-sensitive adhesive having 4 or more carbon atoms in a polymer side chain. The adhesive tape for brittle wafer grinding as described.
(3) The pressure-sensitive adhesive constituting the ray-curing property in the pressure-sensitive adhesive layer is a (meth) acrylic pressure-sensitive adhesive, and the (meth) acrylic pressure-sensitive adhesive occupies in all the base resins in the pressure-sensitive adhesive layer. The adhesive ratio for brittle wafer grinding according to (1) or (2), wherein the content of the agent is 80 to 100% by mass.
(4) The adhesive tape for brittle wafer grinding according to any one of (1) to (3), wherein the adhesive layer in the adhesive tape has a thickness of 20 to 70 μm.
(5) The adhesive tape for brittle wafer grinding according to any one of (1) to (4), wherein the thickness of the base resin film in the adhesive tape is 25 to 150 μm.
(6) The adhesive tape for brittle wafer grinding according to any one of (1) to (5), wherein the brittle wafer is sapphire, silicon carbide, gallium nitride, or gallium arsenide.
(7) Adhering a wafer backside grinding tape to an annular frame having an opening to close the opening, and affixing the surface of the element circuit formed on the brittle wafer on the wafer grinding adhesive tape A step of fixing and supporting;
Fixing the base resin film layer of the adhesive tape for wafer grinding to a chuck table, attaching the wafer, and holding the adhesive tape for wafer grinding ;
A brittle wafer grinding method comprising a step of grinding the back surface of the wafer opposite to the surface on which the wafer grinding adhesive tape is attached,
The brittle wafer grinding method, wherein the adhesive tape for backside grinding of a wafer is the brittle wafer grinding adhesive tape according to any one of (1) to (6).

According to the present invention, in the step of grinding the back surface of a brittle wafer such as a sapphire wafer, the surface of the element circuit or the light emitting layer is protected by sticking a brittle wafer processing adhesive tape to the wafer surface and the annular frame. A brittle wafer processing pressure-sensitive adhesive tape capable of grinding the back surface of a wafer to a practically sufficient thickness and suppressing warpage of the wafer even if the wafer is thinned, and a method of grinding a back surface of a brittle wafer using the same Can be provided.
In addition, the brittle wafer processing adhesive tape of the present invention can reduce the contamination of the brittle wafer surface such as sapphire even after the brittle wafer processing adhesive tape is peeled off, and does not require a separate cleaning step.

It is sectional drawing which shows one Embodiment of the adhesive tape for brittle wafer processing of this invention.

A preferred brittle wafer processing adhesive tape of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of a brittle wafer processing pressure-sensitive adhesive tape 10 of the present invention, in which a base resin film 1 and a radiation curable pressure-sensitive adhesive layer 2 are formed on the base resin film 1. Has been.
The brittle wafer processing adhesive tape 10 of the present invention is used for processing a brittle wafer such as a sapphire wafer.

The adhesive tape for brittle wafer processing of the present invention is attached to the surface of the element circuit (including the light emitting layer surface) formed on the brittle wafer. In the present invention, the brittle wafer means a wafer having a Mohs hardness of 9 or more, and examples thereof include sapphire, silicon carbide, gallium nitride, and gallium arsenide.
The adhesive tape for brittle wafer processing of the present invention can be particularly preferably used for grinding a sapphire wafer. Hereinafter, although it demonstrates with the process process of the sapphire wafer which is a typical brittle wafer, grinding of another brittle wafer can also be performed by the same method.

The adhesive force before radiation curing of the brittle wafer processing adhesive tape of the present invention is 2.0 to 29.8 N / 25 mm in adhesive force to the mirror surface of the silicon wafer. If the adhesive strength is too small, the adhesive tape is peeled off from the edge portion of the wafer due to warpage caused when the sapphire wafer is ground and thinned, and edge cracks are likely to occur in the wafer at that portion. On the other hand, when the adhesive strength of the pressure-sensitive adhesive layer before radiation curing is too large, the pressure-sensitive adhesive may adversely affect the light emitting layer and the circuit surface, or the pressure-sensitive adhesive may remain after radiation curing. The pressure-sensitive adhesive force before radiation curing of the pressure-sensitive adhesive layer is preferably 2.5 to 29.8 N / 25 mm, more preferably 2.5 to 20 N / 25 mm, and still more preferably 2.5 to 10 N / 25 mm. Here, the mirror surface of the silicon wafer refers to a surface polished by polishing that satisfies the specs on the mirror surface side in the test described in JIS H 0614, for example.
The adhesive strength of the adhesive tape for brittle wafer processing before radiation curing was measured with a tensile tester in accordance with JIS B 7721 according to JIS B 7721 with respect to the silicon mirror surface manufactured according to JIS H 0614. It can be determined by measuring the adhesive strength.
More specifically, for example, from a brittle wafer processing adhesive tape, three test pieces having a width of 25 mm and a length of 150 mm are collected, and the test piece is subjected to 3 reciprocations of a 2 kg rubber roller on a 400 μm thick silicon mirror surface. After crimping and allowing to stand for 1 hour, using a tensile tester in accordance with JIS B 7721, using a 90 ° peeling method, measuring temperature 23 ° C., measuring humidity (relative humidity) 50%, and tensile speed It is determined by measuring under the condition of 50 mm / min.

  At the time of back surface grinding, because of the hardness of the sapphire wafer, in order to grind to a desired thickness, a larger force is applied than when grinding a normal silicon wafer. For this reason, in the present invention, in order to increase the elastic modulus of the brittle wafer processing adhesive tape of the present invention, the compression displacement before radiation curing of the brittle wafer processing adhesive tape is 150 μm or less, and 120 μm or less. It is preferable. If the amount of compressive displacement of the brittle wafer processing adhesive tape is too large, the wafer processing adhesive tape is deformed by the stress during back-grinding, and the wafer is easily broken. On the other hand, irregularities are often formed on the wafer surface by element circuits, and if the amount of compressive displacement of the adhesive tape for brittle wafer processing before radiation curing is too small, it becomes difficult to follow the irregularities and the wafer cracks. Is likely to occur. Therefore, the lower limit of the amount of compressive displacement is desirably 20 μm or more.

Here, the amount of compressive displacement in the present invention is a value determined by the following method.
The base resin film layer of the adhesive tape for brittle wafer processing of the present invention, which is preferable for a sapphire wafer, and an adhesive layer are brought into contact with each other to form a test piece. Place the pressure-sensitive adhesive layer in this test piece up and place it on a parallel plate jig for compression testing provided in a tensile testing machine, and compress it at a speed of 1.0 mm / min from the indenter of the bending test (JIS K7171). Apply stress. A portion where the indenter contacts the sample before applying stress is defined as a zero point, and the amount of displacement when a 50N compressive stress is applied is taken as a measured value of the amount of compressive displacement.
That is, the amount of compressive displacement in the present invention is the displacement of the test piece when stress is applied by an indenter from a state in which five sheets of adhesive tape for processing brittle wafers of the present invention are stacked on a parallel plate jig. It shows the amount. Therefore, this compressive displacement amount is technically different from the tensile elastic modulus obtained by conducting a tensile test on the base resin film and the adhesive tape for brittle wafer processing.

Furthermore, in the adhesive tape for brittle wafer processing of the present invention, the water resistance of the adhesive layer surface is also important.
When the water resistance of the pressure-sensitive adhesive layer surface is low, cutting water permeates during wafer grinding, and the adhesive tape is easily peeled off from the edge portion of the wafer, so that edge chipping is induced. In a brittle material such as sapphire, cracks are likely to occur along the crystal direction from the location where such edge chipping occurs. Therefore, the adhesive tape for brittle wafer processing of the present invention desirably has high water resistance on the surface of the pressure-sensitive adhesive layer. In the present invention, the contact angle with pure water on the surface of the pressure-sensitive adhesive layer is 85 ° or more. Further, from the viewpoint of the material properties of the pressure-sensitive adhesive, the upper limit of the contact angle with pure water is preferably 150 ° or less. The contact angle of the pressure-sensitive adhesive layer surface with pure water is particularly preferably 85 to 120 °. The contact angle measurement environment is room temperature (25 ± 5 ° C., preferably 25 ° C.), relative humidity 50 ± 10%, preferably relative humidity 50%.
In this invention, the effect of this invention is acquired by making said adhesive force, a contact angle with pure water, and a compression displacement amount into a specific range.

  In the adhesive tape for brittle wafer processing of the present invention, the method for controlling the adhesive force of the adhesive and the amount of compressive displacement of the adhesive tape is not particularly limited. In general, as a means for increasing the adhesive strength of an adhesive, a method of reducing the degree of crosslinking by reducing the blending amount of the curing agent contained in the adhesive resin composition or lowering the molecular weight of the base resin component is applied. The However, if the adhesive force is too large, the elastic modulus of the adhesive layer becomes too low and the amount of compressive displacement of the adhesive tape increases. That is, the adhesive force and the elastic modulus are in a trade-off relationship.

  Therefore, in the brittle brittle wafer processing pressure-sensitive adhesive tape of the present invention, in order to control the adhesive strength of the pressure-sensitive adhesive within the preferred range as described above, the molecular structure itself of the polymer constituting the pressure-sensitive adhesive, that is, the polymer described later Changing the monomer (preferably various (meth) acrylic acid and its esters) for constructing the chain, specifically, the side chain length of the polymer is 4 or more in carbon number [for example, alkyl (meth) acrylate In the case where the alcohol part has 4 or more carbon atoms, and the alcohol part has a group that acts as a radiation-curable carbon-carbon double bond, the carbon number of the alcohol part is excluded.) The adhesive force and the elastic modulus are both compatible, and the water resistance of the adhesive surface is in a sufficient range. Of course, if the adhesive force, compression displacement amount, and the contact angle of the adhesive layer with pure water in the adhesive tape for brittle wafer processing can be controlled within a suitable range, the curing agent, oligomer, monomer, etc. Other additives may be used.

  The thickness of the pressure-sensitive adhesive layer of the adhesive tape for brittle wafer processing of the present invention is preferably 20 to 70 μm. An element circuit of a light emitting layer such as GaN is formed on the surface of the sapphire wafer, and there are many irregularities. For this reason, if the thickness of the pressure-sensitive adhesive layer is too thin, it becomes difficult to follow the irregularities, and grinding marks (dimples) may easily remain on the wafer crack or the back surface. On the contrary, when the thickness of the pressure-sensitive adhesive layer is too thick, the pressure-sensitive adhesive is deformed due to stress during grinding, and the wafer may be deformed and cracked.

  Moreover, it is preferable that the thickness of the base resin film of the adhesive tape for brittle wafer processing of this invention is 25-150 micrometers, and it is more preferable that it is 50-150 micrometers. When the thickness of the base resin film is too thin, particularly as an adhesive tape for sapphire wafer processing, its rigidity is insufficient, and it becomes difficult to suppress warpage of the wafer. On the other hand, when the thickness of the base resin film is too thick, the flexibility of the adhesive tape for sapphire wafer processing is lowered. Thereby, when bonding the adhesive tape for sapphire wafer processing to a wafer, or at the time of peeling from a wafer, workability | operativity may deteriorate remarkably.

  In the pressure-sensitive adhesive tape for brittle wafer processing of the present invention, the pressure-sensitive adhesive used for the radiation-curable pressure-sensitive adhesive layer can achieve the contact angle between the pressure-sensitive adhesive force and the pure water and the amount of compressive displacement. The type and configuration are not limited. The radiation curable pressure-sensitive adhesive layer may be composed of a single pressure-sensitive adhesive or may be a laminate of a plurality of types of pressure-sensitive adhesives.

In general, the pressure-sensitive adhesive is a resin composition, but the pressure-sensitive adhesive constituting the radiation-curable pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape for brittle wafer processing of the present invention includes a repeating unit of the main chain as the base resin of the resin composition. And a (meth) acryloyl partial structure [—C (═O) CH═CH ₂ or —C (═O) C (CH ₃ ) ═CH ₂ ] acting as a radiation-curable carbon-carbon double bond The main component is the polymer (a) having a group bonded thereto. Here, “having the polymer (a) as a main component” means that the content of the polymer (a) in the entire base resin is 80 to 100% by mass.
In the present invention, “(meth) acryl” includes both “acryl” and “methacryl”.

The polymer (a) may be produced in any way. For example, the polymer (a) has a functional group in the repeating unit of the main chain [functional group for reacting with a compound added in a later reaction, preferably in the side chain. As such a functional group, the group quoted by the functional group which the below-mentioned monomer (a1-2) has is preferable. ] (Preferably a (meth) acrylic copolymer) (a1), a functional group capable of reacting with the functional group (preferred functional groups include those mentioned later), and radiation-curable Examples thereof include compounds obtained by reacting with a compound (a2) having a (meth) acryloyl partial structure acting as a carbon-carbon double bond, and radiation on the side chain with respect to the repeating unit of the main chain. A (meth) acrylic copolymer (a1 ′) having a carbon-carbon double bond acting as a curable carbon-carbon double bond and a functional group, and a functional group of the copolymer (a1 ′); A polymer (a) can also be obtained by reacting with a compound (a2 ′) having a functional group capable of reacting.
The polymer (a1) having the functional group in the repeating unit of the main chain is, for example, an alkyl acrylate that does not have the functional group (the functional group that the following monomer (a1-2) has). It can be obtained by copolymerizing a monomer (a1-1) such as an ester and / or an alkyl methacrylate and the monomer (a1-2) having the functional group.

  The acrylic acid alkyl ester and / or methacrylic acid alkyl ester mentioned in the monomer (a1-1) is preferably one having 4 or more carbon atoms in the alcohol part of the ester, and one having 4 to 18 carbon atoms. More preferred are those having 4 to 12 carbon atoms. In addition, the alkyl group of such an alcohol part may have a substituent, but water resistance greatly varies when a water-soluble group such as a hydroxyl group, a carboxyl group, a sulfo group, or a group containing polyoxyalkylene is substituted. Therefore, an unsubstituted alkyl group is preferable. Examples of the alkyl group in the alcohol part include n-butyl group, isobutyl group, s-butyl group, n-pentyl group, n-hexyl group, 2-ethylhexyl group, t-octyl group, n-octyl group, n -Pentyl group, n-decyl group, n-dodecyl group, n-hexadecyl group, n-octadecyl group, cyclopentyl group, cyclohexyl group and the like.

Examples of the monomer (a1-1) include (meth) acrylic acid alkyl esters having 4 or more alkyl carbon atoms in the alcohol part of the alkyl ester, for example, n-butyl acrylate, n-pentyl acrylate, n Mention may be made of -hexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-dodecyl acrylate, n-decyl acrylate and the corresponding methacrylates.
In addition, examples of the (meth) acrylic acid alkyl ester having less than 4 alkyl carbon atoms in the alcohol portion of the alkyl ester include n-propyl acrylate, isopropyl acrylate, ethyl acrylate, methyl acrylate, and methacrylates corresponding thereto. Can do.

As the monomer (a1-1), the glass transition temperature (Tg) tends to decrease as the alkyl (meth) acrylic acid alkyl ester having a larger number of carbon atoms in the alcohol portion of the alkyl ester is used. Therefore, the polymer (a) having a desired glass transition temperature can be obtained by appropriately selecting the number of carbon atoms in the alcohol part of the alkyl ester of the monomer (a1-1).
In addition to the glass transition temperature, a low molecular compound having a carbon-carbon double bond such as vinyl acetate, styrene or acrylonitrile (a1) is used for the purpose of improving compatibility with other components and various performances as an adhesive. In addition to -1), the polymer (a) may be obtained. The blending amount of these low molecular compounds is preferably 5% by mass or less of the monomer (a1-1).

  Examples of the functional group that the monomer (a1-2) has include a carboxyl group, a hydroxyl group, an amino group, a cyclic acid anhydride group, an epoxy group, and an isocyanate group. Specific examples of the monomer (a1-2) include, for example, acrylic acid, methacrylic acid, cinnamic acid, itaconic acid, fumaric acid, phthalic acid, and 2-hydroxyalkyl acrylates (for example, 2-hydroxylethyl acrylate). 2-hydroxyl-propyl acrylate, 2-hydroxyl-1-methylpropyl acrylate, etc.), 2-hydroxyalkyl methacrylates (for example, 2-hydroxylethyl methacrylate, 2-hydroxyl-propyl methacrylate, 2-hydroxyl-1-methylpropyl) Methacrylate), glycol monoacrylates (eg, 1,3-glycol monoacrylate, 1,4-glycol monoacrylate, diethylene glycol monoacrylate, etc.), glycol monomethacrylates (eg, 1,3-glycol monomethacrylate, 1,4-glycol monomethacrylate, diethylene glycol monomethacrylate, etc.), N-methylolacrylamide, N-methylolmethacrylamide, allyl alcohol, N-alkylaminoethyl acrylates, N-alkylaminoethyl methacrylate , Acrylamides, methacrylamides, maleic anhydride, itaconic anhydride, fumaric anhydride, phthalic anhydride, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, (meth) acryloyloxyalkyl isocyanates (for example, 2-acryloyloxy) Ethyl isocyanate, 3-acryloyloxypropyl isocyanate, 4-acryloyloxybutyl isocyanate, 2-methacrylo (Luoxyethyl isocyanate, 3-methacryloyloxypropyl isocyanate, 4-methacryloyloxybutyl isocyanate, etc.), a part of the isocyanate group of the polyisocyanate compound having a hydroxyl group or a carboxyl group and a radiation-curable carbon-carbon double bond Listed are those urethaned by the body.

Functional group possessed by the polymer (a1) having a (meth) acryloyl partial structure acting as a radiation-curable carbon-carbon double bond [functional group possessed by the monomer (a1-2)] Examples of the functional group of the compound (a2) having a functional group capable of reacting with carboxylic acid include a carboxyl group, a hydroxyl group, an amino group, a cyclic acid anhydride group, an epoxy group, and an isocyanate group.
When the functional group of the compound (a2) is a carboxyl group or a cyclic acid anhydride group, examples of the functional group of the polymer (a1) include a hydroxyl group, an epoxy group, and an isocyanate group.
When the functional group of the compound (a2) is a hydroxyl group, examples of the functional group of the polymer (a1) include a cyclic acid anhydride group and an isocyanate group.
When the functional group of the compound (a2) is an amino group, examples of the functional group of the polymer (a1) include an epoxy group and an isocyanate group.
When the functional group of the compound (a2) is an epoxy group, examples of the functional group of the polymer (a1) include a carboxyl group, a cyclic acid anhydride group, and an amino group.
When the functional group of the compound (a2) is an isocyanate group, examples of the functional group of the polymer (a1) include a hydroxyl group, an amino group, a carboxyl group, and a mercapto group.
As these specific examples, among the specific examples of the monomer (a1-2), the same ones as those other than phthalic anhydride can be listed.

In the reaction of the polymer (a1) and the compound (a2), by leaving an unreacted functional group, the acid value or the hydroxyl value can be suitably set within the range described below.
The polymer (a1) can be obtained by solution polymerization of the monomer (a1-1) and the monomer (a1-2) in various solvents. As the organic solvent in the case of solution polymerization, a ketone, ester, alcohol, or aromatic solvent can be used. In general, it is preferable to use a solvent having a boiling point of 60 to 120 ° C. as a good solvent for a (meth) acrylic polymer. For example, toluene, ethyl acetate, isopropyl alcohol, benzene, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, and the like can be used. As the polymerization initiator, radical generators such as azobis compounds such as α, α′-azobisisobutylnitrile and organic peroxide compounds such as benzoyl peroxide can be used. At this time, if necessary, a catalyst and a polymerization inhibitor can be used in combination, and the polymer (a1) having a desired molecular weight can be obtained by adjusting the polymerization temperature and the polymerization time. In terms of adjusting the molecular weight, it is preferable to use a mercaptan or carbon tetrachloride solvent. The synthesis of the polymer (a1) is not limited to solution polymerization, and other methods such as bulk polymerization and suspension polymerization may be used.

The polymer (a) can be synthesized by adding the compound (a2) to the reaction solution of the polymer (a1).
10-50 mol% is preferable and, as for the ratio for which the said compound (a2) accounts in a polymer (a), 15-40 mol% is more preferable.
The polymer (a) preferably has a repeating unit obtained from (meth) acrylic acid, and the ratio of the repeating unit obtained from (meth) acrylic acid in the polymer (a) is 0.00. 1 mol%-5 mol% are preferable.

In addition to the polymer (a), the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer of the present invention may further contain a base resin having a structure different from that of the polymer (a). The base resin includes a homopolymer having (meth) acrylic acid ester as the main constituent monomer unit, and a (meth) acrylic copolymer containing (meth) acrylic acid ester as one of the constituent monomer units. Can be mentioned. Examples of the (meth) acrylic copolymer include those obtained by further copolymerizing monomers having other functional groups. Examples of the (meth) acrylic acid ester used as the constituent monomer unit include ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, and 2-hydroxyethyl. A (meth) acrylate etc. can be mentioned.
Also in these, 4 or more carbon atoms of the alcohol part of ester are preferable.

  In addition, many urethane (meth) acrylate polymers (oligomers or polymers) lower the contact angle with the pure water described above, and homopolymers having (meth) acrylic acid esters as the main constituent monomer units A (meth) acrylic copolymer containing a (meth) acrylic acid ester as one of the constituent monomer units is preferred. Moreover, as above-mentioned, 80-100 mass% is preferable, as for the content rate of the polymer (a) in all the base resins, 85-100 mass% is more preferable, 90-100 mass% is further more preferable, 95- 100% by mass is particularly preferable and 100% by mass is most preferable.

  About the resin composition which comprises such an adhesive layer, it is preferable that the glass transition temperature by DSC measurement before radiation curing is -40--10 degreeC. In addition, the glass transition temperature by DSC measurement here means the glass transition temperature measured by DSC (differential scanning calorimeter) with the temperature increase rate of 0.1 degree-C / min.

A conventional photopolymerization initiator is preferably used for the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape for brittle wafer processing of the present invention. As the photopolymerization initiator, for example, isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone, chlorothioxanthone, benzyl methyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenyl propane, etc. may be used alone or in combination. Can do. By adding at least one of these to the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, the curing reaction by radiation irradiation can be efficiently advanced.
In addition, the radiation here refers to light rays such as ultraviolet rays or ionizing radiation such as electron beams. The content of the photopolymerization initiator is not particularly limited, but is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the total base resin. .

  For the pressure-sensitive adhesive constituting the pressure-sensitive adhesive for brittle wafer processing (preferably pressure-sensitive adhesive tape for sapphire wafer processing) of the present invention, the base resin can be crosslinked by using a curing agent (crosslinking agent). preferable. Examples of the curing agent include 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, 1,3-bis (N, N-diglycidylaminomethyl) toluene, 1,3-bis (N, N -Diglycidylaminomethyl) benzene, N, N, N, N'-tetraglycidyl-m-xylenediamine and other epoxy compounds having two or more epoxy groups in the molecule, 2,4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4'-diisocyanate and other isocyanate compounds having two or more isocyanate groups in the molecule, tetramethylol-tri -Β-aziridinylpropionate, trimethylol-tri-β-aziridinyl Aziridine compounds having two or more aziridinyl groups in the molecule such as lopionate, trimethylolpropane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β- (2-methylaziridine) propionate, etc. Can be mentioned. What is necessary is just to adjust content of a hardening | curing agent according to desired adhesive force, 0.01-10 mass parts is preferable with respect to 100 mass parts of said base resin, More preferably, 0.1-5 mass Parts, particularly preferably 0.1 to 2 parts by weight.

  Furthermore, the adhesive strength of the adhesive, the compression displacement amount of the adhesive tape, and the contact angle of the adhesive layer with pure water in the adhesive tape for brittle wafer processing of the present invention can be adjusted by adding oligomers or monomers as appropriate. it can.

  The brittle wafer back surface grinding method of the present invention is a process of adhering the adhesive layer of the brittle wafer processing adhesive tape to the element circuit surface (including the light emitting layer surface) and the annular frame formed on the brittle wafer. And holding the base resin film layer of the adhesive tape adhered to the annular frame by fixing it to the chuck table, and the back surface of the brittle wafer opposite to the surface to which the adhesive tape is adhered. And grinding. By this method, the surface of the element circuit and the light emitting layer formed on the brittle wafer can be protected, and the back surface of the wafer can be ground to a practically sufficient thickness. Even if the wafer is thinned, the warpage of the wafer can be achieved. , Cracks and cracks can be suppressed.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.
<Preparation of adhesive tape for brittle wafer processing>
Example 1
1. Preparation of resin composition constituting adhesive (1) Preparation of polymer (aA) An acrylic copolymer comprising 2-ethylhexyl acrylate (69 mol%), 2-hydroxyethyl acrylate (29 mol%), and methacrylic acid (2 mol%) A polymer was prepared. Thereafter, 2-methacryloyloxyethyl isocyanate is added, and the side chain terminal OH group derived from 2-hydroxyethyl acrylate of this acrylic copolymer is reacted with the NCO group of 2-methacryloyloxyethyl isocyanate to form a main chain. In the repeating unit, a polymer (a ^A ) having a methacryloyl group acting as a radiation-curable carbon-carbon double bond as a partial structure was obtained.

The mass average molecular weight and double bond equivalent of the obtained polymer (a ^A ) were measured and calculated by the following method.
(I) weight average molecular weight polymer for (a ^A), the following conditions to measure the mass-average molecular weight by GPC (in gate looper permeation chromatography).
GPC device: HLC-8120GPC (trade name, manufactured by Tosoh Corporation)
Column: TSK gel SuperHM-H / H4000 / H3000 / H2000 (trade name, manufactured by Tosoh Corporation)
Flow rate: 0.6ml / min
Concentration: 0.3% by mass
Injection volume: 20 μl
Column temperature: 40 ° C
Developing solvent: Tetrahydrofuran (ii) double bond equivalent The carbon-carbon double bond equivalent (milliequivalent) in 1 g of the polymer (a ^A ) was calculated by the iodine value measurement method.
The weight average molecular weight of the polymer (a ^A ) was 800,000, and the double bond equivalent was 0.9 meq / g.

(2) Preparation of resin composition To 100 parts by mass of the polymer (a ^A ) obtained in (1), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator. Further, 0.5 parts by mass of a polyisocyanate compound (manufactured by Nippon Polyurethane, trade name Coronate L) was blended as a curing agent to prepare a resin composition (1A) constituting an adhesive.

2. Preparation of wafer processing pressure-sensitive adhesive tape A polyethylene terephthalate (PET) base resin film having a thickness of 100 μm was coated with the resin composition (1A) so that the thickness after drying would be 50 μm, and appropriately cured. Thus, an adhesive tape for wafer processing was obtained.

(Example 2)
1. Preparation of resin composition constituting adhesive (1) Preparation of polymer (a ^B ) Acrylic copolymer consisting of butyl acrylate (69 mol%), 2-hydroxyethyl acrylate (30 mol%), methacrylic acid (1 mol%) A coalescence was prepared. Thereafter, 2-methacryloyloxyethyl isocyanate is added, and the side chain terminal OH group derived from 2-hydroxyethyl acrylate of this acrylic copolymer is reacted with the NCO group of 2-methacryloyloxyethyl isocyanate to form a main chain. In the repeating unit, a polymer (a ^B ) having a methacryloyl group acting as a radiation-curable carbon-carbon double bond as a partial structure was obtained.
The mass average molecular weight of the polymer (a ^B ) measured and calculated by the same method as in Example 1 was 330,000, and the double bond equivalent was 1.5 meq / g.
(2) Preparation of resin composition To 100 parts by mass of the polymer (a ^B ) obtained in (1), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator. Further, 2.9 parts by mass of a polyisocyanate compound (trade name Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was blended as a curing agent to prepare a resin composition (1B) constituting the pressure-sensitive adhesive.

2. Production of Adhesive Tape for Wafer Processing An adhesive tape for wafer processing was obtained by the same method as in Example 1 except that the above resin composition (1B) was used.

(Example 3)
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive Into 100 parts by mass of the above polymer (a ^B ), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator is blended. Further, 0.2 parts by mass of a polyisocyanate compound (trade name Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was blended as a curing agent to prepare a resin composition (1C) constituting the pressure-sensitive adhesive.

2. Preparation of wafer processing pressure-sensitive adhesive tape A wafer processing pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the resin composition (1C) was used for the pressure-sensitive adhesive layer.

Example 4
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive Into 100 parts by mass of the above polymer (a ^B ), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator is blended. Further, 0.7 parts by mass of a polyisocyanate compound (trade name Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was blended as a curing agent to prepare a resin composition (1D) constituting the pressure-sensitive adhesive.

2. Preparation of wafer processing pressure-sensitive adhesive tape On a polyethylene resin terephthalate (PET) base resin film having a thickness of 25 μm, the resin composition (1D) is applied so that the thickness after drying is 20 μm and appropriately cured. Thus, an adhesive tape for wafer processing was obtained.

(Example 5)
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive The resin composition (1D) constituting the pressure-sensitive adhesive prepared in Example 4 was used.

2. Preparation of adhesive tape for wafer processing The same method as in Example 1 except that a base resin film of polyethylene terephthalate (PET) having a thickness of 50 μm was used and the resin composition (1D) was used. Thus, an adhesive tape for wafer processing was obtained.

(Example 6)
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive The resin composition (1D) constituting the pressure-sensitive adhesive prepared in Example 4 was used.

2. Preparation of wafer processing pressure-sensitive adhesive tape A wafer processing pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the resin composition (1D) was used for the pressure-sensitive adhesive layer.

(Example 7)
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive The resin composition (1D) constituting the pressure-sensitive adhesive prepared in Example 4 was used.

2. Production of Adhesive Tape for Wafer Processing The same method as in Example 1 except that a polyethylene terephthalate (PET) base resin film having a thickness of 150 μm was used and that the above resin composition (1D) was used. Thus, an adhesive tape for wafer processing was obtained.

(Example 8)
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive Into 100 parts by mass of the above polymer (a ^B ), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator is blended. Further, 1.3 parts by mass of a polyisocyanate compound (trade name Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added as a curing agent to prepare a resin composition (1E) constituting the pressure-sensitive adhesive.

2. Preparation of wafer processing pressure-sensitive adhesive tape A polyethylene terephthalate (PET) base resin film having a thickness of 100 μm was coated with the resin composition (1E) so that the thickness after drying was 20 μm, and appropriately cured. Thus, an adhesive tape for wafer processing was obtained.

Example 9
1. Preparation of resin composition constituting adhesive (1) Preparation of polymer (a ^C ) Methyl methacrylate (10 mol%), 2-ethylhexyl acrylate (69 mol%), 2-hydroxyethyl methacrylate (20 mol%), methacrylic acid An acrylic copolymer consisting of (1 mol%) was prepared. Thereafter, 2-methacryloyloxyethyl isocyanate is added to react the side chain terminal OH group derived from 2-hydroxyethyl methacrylate of this acrylic copolymer with the NCO group of 2-methacryloyloxyethyl isocyanate, In the repeating unit of the chain, a polymer (a ^C ) having a methacryloyl group acting as a radiation-curable carbon-carbon double bond as a partial structure was obtained.
The mass average molecular weight of the polymer (a ^C ) measured and calculated by the same method as in Example 1 was 200,000, and the double bond equivalent was 0.59 meq / g.
(2) Preparation of resin composition constituting pressure-sensitive adhesive To 100 parts by mass of the polymer (a ^C ) obtained in (1), Irgacure 184 ((trade name), manufactured by Ciba Geigy, Japan) is used as a photopolymerization initiator. The resin composition (1F) which comprises 2.0 mass parts and mix | blends 0.3 mass part of polyisocyanate compounds (The product made from Nippon Polyurethane company, brand name Coronate L) as a hardening | curing agent was further prepared. .

2. Preparation of wafer processing pressure-sensitive adhesive tape A polyethylene terephthalate (PET) base resin film having a thickness of 100 μm was coated with the resin composition (1F) so that the thickness after drying would be 70 μm, and appropriately cured. Thus, an adhesive tape for wafer processing was obtained.

(Example 10)
1. Using polymer prepared in Preparation Example 9 Preparation of (1) polymer of the resin composition constituting the pressure-sensitive adhesive (a ^C) (a ^C).
(2) Preparation of resin composition constituting pressure-sensitive adhesive The resin composition (1F) constituting the pressure-sensitive adhesive prepared in Example 9 was used.
2. Preparation of wafer processing pressure-sensitive adhesive tape A 150 μm-thick polyethylene terephthalate (PET) base resin film was coated with the above resin composition (1F) so that the thickness after drying was 70 μm, and appropriately cured. Thus, an adhesive tape for wafer processing was obtained.

(Comparative Example 1)
1. Using polymer prepared in Preparation Example 1 Preparation of (1) polymer of the resin composition constituting the pressure-sensitive adhesive (a ^A) (a ^A).
(2) Preparation of resin composition constituting pressure-sensitive adhesive In 100 parts by mass of the above polymer (a ^A ), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator is blended. Further, 2.2 parts by mass of a polyisocyanate compound (trade name Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added as a curing agent to prepare a resin composition (2A) constituting the pressure-sensitive adhesive.

2. Production of Adhesive Tape for Wafer Processing An adhesive tape for wafer processing was obtained in the same manner as in Example 1 except that the resin composition (2A) was used for the adhesive layer.

(Comparative Example 2)
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive The resin composition (1D) constituting the pressure-sensitive adhesive prepared in Example 4 was used.

2. Preparation of wafer processing pressure-sensitive adhesive tape A polyethylene terephthalate (PET) base resin film with a thickness of 100 μm was coated with the resin composition (1D) so that the thickness after drying would be 80 μm, and appropriately cured. Thus, an adhesive tape for wafer processing was obtained.

(Comparative Example 3)
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive The resin composition (1D) constituting the pressure-sensitive adhesive prepared in Example 4 was used.

2. Preparation of wafer processing pressure-sensitive adhesive tape A polyethylene terephthalate (PET) base resin film having a thickness of 165 μm was coated with the resin composition (1D) so that the thickness after drying would be 50 μm. Thus, an adhesive tape for wafer processing was obtained.

(Comparative Example 4)
1. Using polymer prepared in Preparation Example 2 Preparation of resin composition constituting the pressure-sensitive adhesive (1) polymer (a ^B) (a ^B).
(2) Preparation of resin composition constituting pressure-sensitive adhesive Into 100 parts by mass of the above polymer (a ^B ), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator is blended. Further, 0.1 parts by mass of a polyisocyanate compound (trade name Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was blended as a curing agent to prepare a resin composition (2B) constituting the pressure-sensitive adhesive.

2. Preparation of wafer processing pressure-sensitive adhesive tape A wafer processing pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the resin composition (2B) was used for the pressure-sensitive adhesive layer.

(Comparative Example 5)
1. Preparation of resin composition constituting adhesive (1) Preparation of polymer (b ^F ) Acrylic copolymer consisting of butyl acrylate (81 mol%), 2-hydroxyethyl acrylate (18 mol%), methacrylic acid (1 mol%) A coalescence was prepared. Thereafter, 2-methacryloyloxyethyl isocyanate is added, and the side chain terminal OH group derived from 2-hydroxyethyl acrylate of this acrylic copolymer is reacted with the NCO group of 2-methacryloyloxyethyl isocyanate to form a main chain. In the repeating unit, a polymer (b ^F ) having a methacryloyl group acting as a radiation-curable carbon-carbon double bond as a partial structure was obtained.
The mass average molecular weight of the polymer (b ^F ) measured and calculated by the same method as in Example 1 was 340,000, and the double bond equivalent was 0.9 meq / g.
(2) Preparation of resin composition To 100 parts by mass of the polymer (b ^F ) obtained in (1), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator. Further, 0.5 parts by mass of a polyisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., trade name Coronate L) was blended as a curing agent to prepare a resin composition (2C) constituting the pressure-sensitive adhesive.

2. Preparation of wafer processing pressure-sensitive adhesive tape A wafer processing pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the resin composition (2C) was used for the pressure-sensitive adhesive layer.

(Comparative Example 6)
1. Preparation of resin composition constituting adhesive (1) Preparation of polymer (b ^G ) Ethyl acrylate (45 mol%), butyl acrylate (35 mol%), 2-hydroxyethyl acrylate (19 mol%), methacrylic acid (1. An acrylic copolymer comprising 5 mol%) was prepared. Thereafter, 2-methacryloyloxyethyl isocyanate is added, and the side chain terminal OH group derived from 2-hydroxyethyl acrylate of this acrylic copolymer is reacted with the NCO group of 2-methacryloyloxyethyl isocyanate to form a main chain. In the repeating unit, a polymer (b ^G ) having a methacryloyl group acting as a radiation-curable carbon-carbon double bond as a partial structure was obtained.
The weight average molecular weight of the polymer (b ^G ) measured and calculated by the same method as in Example 1 was 660,000, and the double bond equivalent was 0.6 meq / g.
(2) Preparation of resin composition To 100 parts by mass of the polymer (b ^G ) obtained in (1), 2.0 parts by mass of Irgacure 184 ((trade name), manufactured by Ciba Geigy Japan) as a photopolymerization initiator. Further, 1.5 parts by mass of a polyisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., trade name Coronate L) was blended as a curing agent to prepare a resin composition (2D) constituting the pressure-sensitive adhesive.

2. Preparation of wafer processing pressure-sensitive adhesive tape A polyethylene terephthalate (PET) base resin film having a thickness of 100 μm was coated with the resin composition (2D) so that the thickness after drying would be 70 μm, and appropriately cured. Thus, an adhesive tape for wafer processing was obtained.

<Evaluation of adhesive tape for wafer processing>
The following evaluation was performed about the adhesive tape for brittle wafer processing of Examples 1-10 and Comparative Examples 1-6, and the performance was evaluated. The results are shown in Tables 1 and 2 below.

1. Adhesive strength Three test pieces each having a width of 25 mm and a length of 150 mm were collected from the wafer processing adhesive tapes of Examples and Comparative Examples, and the test pieces were pressure-bonded by applying a 2 kg rubber roller to a silicon mirror surface having a thickness of 400 μm three times. did. The silicon mirror surface is manufactured according to JIS H 0614. After standing for 1 hour, the adhesive strength was measured with a tensile tester in accordance with JIS B 7721.
The measurement was performed by a 90 ° peeling method under the conditions of a tensile speed of 50 mm / min, a measurement temperature of 23 ° C., and a measurement humidity (relative humidity) of 50%. Those having an adhesive strength of 2.0 to 29.8 N / 25 mm were accepted, and those having an adhesive strength of less than 2.0 N / 25 mm and those exceeding 29.8 N / 25 mm were rejected.

2. Contact angle with pure water on the surface of the pressure-sensitive adhesive layer The separators of the pressure-sensitive adhesive tapes for wafer processing in Examples and Comparative Examples were peeled off, and pure water was dropped onto the surface of the pressure-sensitive adhesive layer. The contact angle immediately after dropping was measured with a contact angle meter (manufactured by Kyowa Interface Science: CONACT-ANGLE METER MODEL: CA-S), and 85 ° or more was accepted and less than 85 ° was rejected.

3. Compression displacement amount Five wafer processing adhesive tapes of Examples and Comparative Examples were cut to a size of about 200 mm × 200 mm and laminated between the base resin film and the adhesive layer. The laminated one was cut into 25 mm × 55 mm and used as a test piece. With the adhesive layer of this test piece facing up, the test piece was placed on a parallel plate jig for compression test provided in a tensile tester, and the compression stress was applied at a speed of 1.0 mm / min from the indenter of the bending test (JIS K7171). Was applied. The portion where the indenter contacted the sample before applying the stress was taken as the zero point, and the amount of displacement when 50 N compressive stress was applied was taken as the measured value.
Those having a compression displacement of 150 μm or less were accepted and those other than that were rejected.

4). Tape peeling of wafer outer peripheral part Adhesive tapes for wafer processing of Examples and Comparative Examples were bonded to the surface of a sapphire wafer having a diameter of 4 inches, and sapphire was obtained with a back grinding apparatus (trade name: DFG8540, manufactured by DISCO Corporation). The back surface of the wafer was ground until the thickness of the wafer reached 100 μm. In addition, when it could not grind to 100 micrometers, it was set as the curvature by the finishing thickness which can be ground. The wafer outer peripheral part to which the tape after grinding was bonded was visually observed, and the case where the tape was not peeled compared to before grinding was indicated as “◯”, and the part where the tape was lifted was indicated as “X”.

5. Grindable finish thickness Adhesive tapes for wafer processing of Examples and Comparative Examples are bonded to the surface of a sapphire wafer with a diameter of 4 inches, and a sapphire wafer with a back grinding apparatus (trade name: DFG8540, manufactured by DISCO Corporation). The back side was ground. Grinding was performed by changing the grinding thickness of the backside of the wafer, and the wafer after grinding was observed. The minimum thickness without cracks or cracks was defined as the finish thickness that can be ground. 80 to 90 μm was rated as ◎, 91 to 120 μm as ◯, 121 to 164 μm as Δ, and 165 μm or more as ×.
Both the tape peeling on the outer periphery of the wafer and the finish thickness that can be ground were passed with a rank of ◎ or ◯, and those with other ranks were rejected.

  In Tables 1 and 2 below, the number of carbons in the side chain of the polymer indicates the number of carbons in the alcohol part other than having in the alcohol part a group that acts as a radiation-curable carbon-carbon double bond. In the case of having a part, the number of individual carbons is shown, and in parentheses, the average number of carbons in terms of molar conversion of these is shown.

As can be seen from Table 1 and Table 2 above, when the wafer processing pressure-sensitive adhesive tape of the present invention was used, excellent characteristics at an acceptable level were obtained in the evaluation of the warp of the sapphire wafer and the finished thickness after grinding. In particular, in Examples 1, 2, and 5 to 8 in which both the adhesive force and the contact angle are within the specified ranges and the compression displacement amount is 120 μm or less, the finish thickness that can be ground was ◎.
On the other hand, in Comparative Example 1, the adhesive force was low, and the tape was peeled off at the outer peripheral portion of the wafer, so that the edge crack was caused by the wafer edge portion floating. Further, in Comparative Examples 2 and 3, the displacement amount exceeded 150 μm, and the finished thickness capable of grinding was increased. In Comparative Example 4, the adhesive force is too high, and the adhesive tape for brittle wafer processing is irradiated with ultraviolet rays. When the adhesive tape is peeled off, the adhesive layer is cured and shrunk when cured with ultraviolet rays, and the sapphire wafer is cracked. Finish thickness was rejected. In Comparative Examples 5 and 6, since the pure water contact angle on the surface of the agent layer was low and the water resistance was insufficient, a finish thickness that could be ground was not sufficiently obtained, and the overall evaluation did not reach a pass level.

  In addition, while sticking each brittle wafer processing adhesive tape of Examples 1-10 to the annular frame which has an opening part, this opening part is block | closed, and on a 4 inch diameter sapphire wafer on the brittle wafer processing adhesive tape The surface of the element circuit formed on is adhered and fixedly supported, the base resin film layer of the adhesive tape for brittle wafer processing is fixed to the chuck table, and this sapphire wafer is adhered to the adhesive tape for brittle wafer processing. After holding, change the grinding thickness of the sapphire wafer on the back side of the sapphire wafer opposite to the surface on which the adhesive tape for brittle wafer processing is affixed with a back grinding device (trade name: DGP8760, manufactured by DISCO Corporation) And then ground. As a result, each of the brittle wafer processing adhesive tapes of Examples 1 to 10 reflected the performance evaluated above, and confirmed that the minimum thickness without cracks and cracks was 80 to 120 μm.

DESCRIPTION OF SYMBOLS 1 Base resin film 2 Radiation curable adhesive layer 10 Adhesive tape for brittle wafer processing

Claims (7)

1. An adhesive tape for brittle wafer backside grinding having a radiation curable adhesive layer on a base resin film, wherein the adhesive force of the adhesive layer on the mirror surface of the silicon wafer in the adhesive tape is 2.2. 0 to 29.8 N / 25 mm, the contact angle with pure water on the surface of the pressure-sensitive adhesive layer is 85 ° or more, and the amount of compressive displacement in the pressure-sensitive adhesive tape before radiation curing is 150 μm or less. Adhesive tape for backside grinding of brittle wafers. The brittleness according to claim 1, wherein the pressure-sensitive adhesive constituting the ray-curing property in the pressure-sensitive adhesive layer is a (meth) acrylic pressure-sensitive adhesive having 4 or more carbon atoms in a polymer side chain. Adhesive tape for wafer grinding . The pressure-sensitive adhesive constituting the ray-curing property in the pressure-sensitive adhesive layer is a (meth) acrylic pressure-sensitive adhesive, and the (meth) acrylic pressure-sensitive adhesive occupies in all the base resins in the pressure-sensitive adhesive layer The adhesive tape for brittle wafer grinding according to claim 1 or 2, wherein the ratio is 80 to 100% by mass. The adhesive tape for brittle wafer grinding according to any one of claims 1 to 3, wherein a thickness of the adhesive layer in the adhesive tape is 20 to 70 µm. The brittle wafer grinding pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein a thickness of the base resin film in the pressure-sensitive adhesive tape is 25 to 150 µm. The adhesive tape for brittle wafer grinding according to any one of claims 1 to 5, wherein the brittle wafer is sapphire, silicon carbide, gallium nitride, or gallium arsenide. A wafer backside grinding adhesive tape is attached to an annular frame having an opening to close the opening, and an element circuit surface formed on a brittle wafer is attached to the wafer grinding adhesive tape for fixed support. Process,
Fixing the base resin film layer of the adhesive tape for wafer grinding to a chuck table, attaching the wafer, and holding the adhesive tape for wafer grinding ;
A brittle wafer grinding method comprising a step of grinding the back surface of the wafer opposite to the surface on which the wafer grinding adhesive tape is attached,
The brittle wafer grinding method, wherein the adhesive tape for backside grinding of the wafer is the brittle wafer grinding adhesive tape according to any one of claims 1 to 6.

Images