WO2023281860A1

WO2023281860A1 - Protective sheet for semiconductor processing and method for producing semiconductor device

Info

Publication number: WO2023281860A1
Application number: PCT/JP2022/014416
Authority: WO
Inventors: 和幸田村
Original assignee: リンテック株式会社
Priority date: 2021-07-06
Filing date: 2022-03-25
Publication date: 2023-01-12
Also published as: TW202302792A; KR20240031950A; CN117413349A; JPWO2023281860A1

Abstract

[Problem] To provide: a protective sheet for semiconductor processing, the protective sheet being suppressed in breakage of a wafer when the protective sheet for semiconductor processing is removed therefrom even in cases where the wafer after back grinding is thin, while being sufficiently suppressed in the occurrence of electrification during the processing of the wafer; and a method for producing a semiconductor device, the method using this protective sheet for semiconductor processing. [Solution] A protective sheet for semiconductor processing, the protective sheet comprising a base material, an antistatic layer and an energy ray-curable adhesive layer, wherein the peel strength at the time when the adhesive layer after energy ray curing is peeled off from a silicon wafer at a peeling rate of 600 mm/minute in such a manner that the angle between the adhesive layer and the silicon wafer is 90° is not less than 0.035 N/25 mm but less than 0.15 N/25 mm.

Description

Protective sheet for semiconductor processing and method for manufacturing semiconductor device

The present invention relates to a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device. In particular, the present invention relates to a semiconductor processing protective sheet suitably used in a method of obtaining a thin wafer by back-grinding a wafer, and a semiconductor device manufacturing method using the semiconductor processing protective sheet.

Various electronic devices are equipped with a large number of semiconductor devices on which semiconductor chips obtained by singulating semiconductor wafers on which circuits are formed are mounted. Electronic devices are rapidly becoming smaller and more multifunctional, and semiconductor chips are also required to be smaller, thinner and more dense. In order to reduce the size and height of a chip, it is common to form a circuit on the surface of a semiconductor wafer and then grind the back surface of the semiconductor wafer to adjust the thickness of the chip.

When the backside of a semiconductor wafer is ground, a protective sheet called a backgrind tape is attached to the wafer surface in order to protect the circuits on the wafer surface and hold the semiconductor wafer.

The backgrinding tape strongly adheres to the front surface of the wafer when the backside of the wafer is ground, and sufficiently protects the circuits, etc., and can be easily peeled off from the wafer when the backgrinding tape is peeled off from the wafer after backgrinding. Desired. Therefore, the pressure-sensitive adhesive layer of the backgrinding tape applied to the wafer is usually composed of an energy ray-curable pressure-sensitive adhesive. At the time of peeling, the pressure-sensitive adhesive layer is irradiated with energy rays to be cured and reduced in adhesive strength, thereby achieving both adhesion during back-grinding and releasability after back-grinding.

In addition, it is known that electrification occurs during wafer processing (for example, during dicing, backside grinding, cleaning, peeling of the backgrinding tape, etc.). When static electricity is generated, electrical discharge breakdown of the circuits on the wafer or singulated chips is likely to occur. Cut dust generated during grinding and minute foreign substances in the environment adhere to the wafer or singulated chips. problems such as becoming easier.

In Patent Document 1, a base film, an antistatic layer, and an adhesive layer are provided, the surface resistivity of the adhesive layer after ultraviolet curing is within a predetermined range, and the adhesive layer after ultraviolet curing is An antistatic pressure sensitive adhesive tape for semiconductor processing is disclosed which has a 90 degree peeling adhesive force within a predetermined range.

JP 2011-210944 A

In recent years, in order to realize high-density mounting in electronic devices, semiconductor chips are becoming smaller, lower-profile, and higher-density. Therefore, in order to make the chip smaller and thinner, it is necessary to reduce the thickness of the wafer after backside grinding.

However, if the thickness of the wafer after backgrinding is reduced, the wafer may be damaged when the backgrinding tape is removed from the wafer after backgrinding. For example, in Patent Document 1, when the thickness of the wafer after back grinding is 100 μm, the wafer is not damaged by peeling of the antistatic adhesive tape for semiconductor processing. However, when the thickness of the wafer after backside grinding is further reduced, there is a problem that the wafer is damaged due to peeling of the antistatic adhesive tape for semiconductor processing.

The present invention has been made in view of such a situation, and even if the wafer is thin after backside grinding, the damage of the wafer is suppressed when the protective sheet for semiconductor processing is peeled off, and the charging generated during wafer processing is sufficient. It is an object of the present invention to provide a protective sheet for semiconductor processing which is suppressed to , and to provide a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing.

Aspects of the present invention are as follows.
[1] having a substrate, an antistatic layer, and an energy ray-curable adhesive layer,
When the adhesive layer after energy beam curing is peeled off from the silicon wafer at a peeling speed of 600 mm/min so that the angle formed by the adhesive layer and the silicon wafer is 90°, the adhesive strength is 0.035 N/25 mm or more 0 It is a protective sheet for semiconductor processing which is less than .15 N/25 mm.

[2] The adhesive force when the adhesive layer before energy beam curing is peeled off from the silicon wafer at a peeling speed of 600 mm / min so that the angle formed by the adhesive layer and the silicon wafer is 90 °. The adhesive strength ratio when the adhesive layer after linear curing is peeled off from the silicon wafer at a peeling speed of 600 mm/min so that the angle formed by the adhesive layer and the silicon wafer is 90° is 4% or less. The protective sheet for semiconductor processing according to [1].

[3] According to [1] or [2], the surface resistivity of the pressure-sensitive adhesive layer after energy ray curing is 5.1×10 ¹² Ω/cm ² or more and 1.0×10 ¹⁵ Ω/cm ² or less. It is a protective sheet for semiconductor processing.

[4] The protective sheet for semiconductor processing is the protective sheet for semiconductor processing according to any one of [1] to [3], further comprising a buffer layer.

[5] A step of attaching the protective sheet for semiconductor processing according to any one of [1] to [4] to the surface of the wafer;
A step of grinding a wafer having a protective sheet for semiconductor processing attached to its surface from the back side;
and peeling off a protective sheet for semiconductor processing from a wafer after backside grinding.

According to the present invention, even if the wafer after backside grinding is thin, damage to the wafer is suppressed when the protective sheet for semiconductor processing is peeled off, and electrification generated during wafer processing is sufficiently suppressed. It is possible to provide a protective sheet for semiconductor processing, and to provide a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing.

FIG. 1A is a schematic cross-sectional view showing an example of the protective sheet for semiconductor processing according to this embodiment. FIG. 1B is a schematic cross-sectional view showing another example of the protective sheet for semiconductor processing according to this embodiment. FIG. 2 is a schematic cross-sectional view showing how the protective sheet for semiconductor processing according to this embodiment is attached to the circuit surface of the wafer.

Hereinafter, the present invention will be described in detail based on specific embodiments with reference to the drawings. First, major terms used in this specification will be explained.

Wafer singulation refers to dividing the wafer into individual circuits to obtain chips.

The "front surface" of the wafer refers to the surface on which circuits, electrodes, etc. are formed, and the "back surface" of the wafer refers to the surface on which circuits, etc. are not formed.

DBG (Dicing Before Grinding) refers to a method of forming grooves of a predetermined depth on the front side of a wafer, grinding the back side of the wafer, and singulating the wafer by grinding. The grooves formed on the surface side of the wafer are formed by a method such as blade dicing, laser dicing or plasma dicing.

In addition, LDBG (Laser Dicing Before Grinding) is a modification of DBG, and refers to a method in which a modified region is provided inside the wafer with a laser, and the wafer is separated into individual pieces by stress or the like during wafer backside grinding.

"Chip group" refers to a plurality of chips held on the protective sheet for semiconductor processing according to the present embodiment after singulation of the wafer. These chips collectively form a shape similar to that of the wafer.

"(Meth)acrylate" is used as a term to indicate both "acrylate" and "methacrylate", and the same applies to other similar terms.

"Energy rays" refer to ultraviolet rays, electron rays, etc., preferably ultraviolet rays.

"Weight average molecular weight" is a polystyrene conversion value measured by a gel permeation chromatography (GPC) method unless otherwise specified. Measurement by such a method can be carried out, for example, on a high-speed GPC apparatus "HLC-8120GPC" manufactured by Tosoh Corporation, using high-speed columns "TSK guard column H _XL -H", "TSK Gel GMH _XL ", and "TSK Gel G2000 H _XL ". (all manufactured by Tosoh Corporation) in this order, column temperature: 40° C., liquid feed rate: 1.0 mL/min, and a differential refractometer as a detector.

(1. Protective sheet for semiconductor processing)
As shown in FIG. 1A, the protective sheet for semiconductor processing 1 according to the present embodiment has a structure in which an antistatic layer 20 and an adhesive layer 30 are provided in this order on one main surface 10a of a substrate 10. ing. From the viewpoint of the antistatic function, the antistatic layer is preferably close to the peeling interface of the protective sheet for semiconductor processing, that is, the surface 30a of the pressure-sensitive adhesive layer. Therefore, as shown in FIG. 1A, antistatic layer 20 is preferably provided on one main surface 10a of substrate 10 rather than on the other main surface 10b of substrate 10. FIG. When the protective sheet for semiconductor processing 1 is used, the surface 30a of the pressure-sensitive adhesive layer 30 is temporarily attached to an adherend and then peeled off from the adherend.

In addition, the protective sheet for semiconductor processing may have other layers as long as the effects of the present invention can be obtained. That is, as long as the protective sheet for semiconductor processing has a substrate, an antistatic layer and an adhesive layer, for example, another layer may be formed between the substrate and the adhesive layer, Another layer may be formed between the substrate and the antistatic layer.

As another example of the protective sheet for semiconductor processing, as shown in FIG. A protection sheet for semiconductor processing having a structure in which a buffer layer 40 is provided on the main surface 10b of the semiconductor processing is exemplified.

The protective sheet for semiconductor processing shown in FIG. 1B is suitable as a protective sheet for semiconductor processing used when grinding the back surface of a wafer in a so-called dicing before grinding (DBG) method.

In the pre-dicing method, grooves of a predetermined depth are formed from the front surface of the wafer using a dicing blade, then the back surface of the wafer is ground. is the way to get In addition, as a modification of DBG, laser dicing before grinding (LDBG), which is a method in which a modified region is provided inside a wafer by a laser and the wafer is singulated by stress or the like during wafer backside grinding, may be used.

The protective sheet for semiconductor processing shown in FIG. 1A will be described below.

As shown in FIG. 2, the surface 30a of the adhesive layer is attached to the circuit surface of the wafer 100 as an adherend, that is, the surface 100a of the wafer 100, whereby the protective sheet for semiconductor processing according to the present embodiment is formed. 1 protects the front surface 100a of the wafer 100 when the rear surface 100b of the wafer 100 is ground.

Since the adhesive layer 30 of the protective sheet for semiconductor processing 1 is energy ray-curable, it is attached to the surface 100a of the wafer 100 before being cured with the energy ray during back grinding, and the surface of the wafer 100 is adhered to the surface 100a of the wafer 100 with high adhesive strength. 100a can be sufficiently protected.

After the backside grinding is finished, the protective sheet for semiconductor processing 1 is peeled off from the front surface 100a of the wafer 100 . At this time, the adhesive layer 30 of the protective sheet for semiconductor processing 1 is irradiated with energy rays to cure the adhesive layer 30 and reduce its adhesive force. By doing so, the protective sheet for semiconductor processing 1 can be easily peeled off.

However, when the protective sheet for semiconductor processing is peeled off, stress is applied to the wafer after back-grinding, so if the thickness of the wafer after back-grinding is thin, it may not be able to withstand the stress and break. The stress generated during peeling increases as the adhesive strength of the adhesive layer after energy ray curing increases. Therefore, in the protective sheet for semiconductor processing according to the present embodiment, the adhesive strength of the adhesive layer after curing with energy rays is within a predetermined range, thereby reducing damage to the wafer when the protective sheet for semiconductor processing is peeled off. there is

Here, when the amount of energy ray-polymerizable carbon-carbon double bonds in the pressure-sensitive adhesive layer before curing increases, the pressure-sensitive adhesive layer tends to be cured more easily, and the adhesive strength of the pressure-sensitive adhesive layer after curing tends to decrease. It is preferable because it is However, when the amount of energy ray-polymerizable carbon-carbon double bonds in the pressure-sensitive adhesive layer before curing increases, the number of cross-linking points in the pressure-sensitive adhesive layer after curing increases, making it difficult for electric charges to move and charging to occur easily.

Then, in addition to the electrification that occurs on the wafer during wafer processing that includes the above-described backside grinding, electrification derived from the adhesive layer also occurs, making it difficult to alleviate the electrification. As a result, a large amount of foreign matter or the like is attached to the wafer due to electrification, which may cause breakage of the wafer during back-grinding. Therefore, in this embodiment, in addition to the adhesive force of the adhesive layer after curing, the protective sheet for semiconductor processing includes an antistatic layer to alleviate static electricity and reduce the charged voltage of the wafer.

The constituent elements of the protective sheet for semiconductor processing will be described in detail below.

(2. Base material)
The substrate is not limited as long as it is made of a material that can support the wafer before the back surface of the wafer is ground and that can hold the wafer after the back surface is ground. For example, the base material includes various resin films used as base materials for back grind tapes. The substrate may be composed of a single-layer film made of one resin film, or may be composed of a multi-layer film in which a plurality of resin films are laminated.

(2.1 Physical properties of base material)
In this embodiment, the substrate preferably has high rigidity. The high rigidity of the base material makes it possible to suppress vibration and the like during back-grinding. In addition, it contributes to reduction of stress when the protective sheet for semiconductor processing is peeled off from the wafer, and damage and cracks of the wafer caused during peeling are reduced. Furthermore, workability is improved when the protective sheet for semiconductor processing is attached to the wafer. Specifically, the Young's modulus of the substrate at 23° C. is preferably 1000 MPa or more, more preferably 1800 MPa or more. Although the upper limit of Young's modulus is not particularly limited, it is about 30000 MPa. The Young's modulus of the base material can be controlled by selection of the resin composition, addition of a plasticizer, stretching conditions during production of the resin film, and the like.

In this embodiment, the thickness of the base material is preferably 15 μm or more and 110 μm or less, more preferably 20 μm or more and 105 μm or less.

(2.2 Material of base material)
The material of the substrate is preferably selected so that the Young's modulus of the substrate is within the above range. In the present embodiment, for example, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyester such as wholly aromatic polyester, polyimide, polyamide, polycarbonate, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, biaxially oriented A polypropylene etc. are mentioned. Among these, one or more selected from polyester, polyamide, polyimide, and biaxially oriented polypropylene is preferable, polyester is more preferable, and polyethylene terephthalate is further preferable.

In addition, the base material may contain plasticizers, lubricants, infrared absorbers, ultraviolet absorbers, fillers, colorants, antistatic agents, antioxidants, catalysts, etc., as long as they do not impair the effects of the present invention. Also, the substrate may be transparent or opaque, and may be colored or vapor-deposited as desired.

In addition, at least one main surface of the base material may be subjected to adhesion treatment such as corona treatment in order to improve adhesion with other layers. Also, the base material may have a primer layer on at least one of its main surfaces.

The primer layer-forming composition for forming the primer layer is not particularly limited, but examples thereof include compositions containing polyester-based resins, urethane-based resins, polyester-urethane-based resins, acrylic-based resins, and the like. The primer layer-forming composition may optionally contain a cross-linking agent, a photopolymerization initiator, an antioxidant, a softening agent (plasticizer), a filler, an antirust agent, a pigment, a dye, and the like. .

The thickness of the primer layer is preferably 0.01-10 μm, more preferably 0.03-5 μm. Since the material of the primer layer is soft, it has little effect on the Young's modulus, and the Young's modulus of the substrate is substantially the same as that of the resin film even when the primer layer is provided.

(3. Adhesive layer)
The adhesive layer is attached to the circuit surface of the semiconductor wafer, protects the circuit surface, and supports the semiconductor wafer until it is peeled off from the circuit surface. In this embodiment, the pressure-sensitive adhesive layer is energy ray-curable. The pressure-sensitive adhesive layer may be composed of one layer (single layer), or may be composed of multiple layers of two or more layers. When the pressure-sensitive adhesive layer has multiple layers, these multiple layers may be the same or different, and the combination of layers constituting these multiple layers is not particularly limited.

Although the thickness of the adhesive layer is not particularly limited, it is preferably 3 µm or more and 200 µm or less, more preferably 5 µm or more and 100 µm or less. When the thickness of the pressure-sensitive adhesive layer is within the above range, cracking of the wafer can be suppressed.

The thickness of the adhesive layer means the thickness of the entire adhesive layer. For example, the thickness of a pressure-sensitive adhesive layer composed of multiple layers means the total thickness of all layers constituting the pressure-sensitive adhesive layer.

In this embodiment, the adhesive layer has the following physical properties.

(3.1 90° peeling adhesive strength of adhesive layer after energy beam curing)
In the present embodiment, the adhesive strength when the adhesive layer after energy ray curing is peeled off from the silicon wafer so that the angle between the adhesive layer and the silicon wafer is 90° (hereinafter referred to as the adhesive after energy ray curing 90° peeling adhesive strength of the agent layer) is 0.035 N/25 mm or more and less than 0.15 N/25 mm. If the 90° peeling adhesive strength of the pressure-sensitive adhesive layer after energy ray curing is within the above range, the tape may be peeled off at an unexpected timing before the predetermined tape peeling process, resulting in process errors. is suppressed and the adhesive force is sufficiently lowered, the adhesive layer can be easily peeled off even if the wafer after back grinding is thin. Therefore, damage to the wafer can be effectively suppressed, and adhesive residue on the wafer can be reduced.

The 90° peeling adhesive strength of the adhesive layer after energy ray curing is preferably 0.14 N/25 mm or less, more preferably 0.13 N/25 mm or less.

In this embodiment, the 90° peeling adhesive strength of the pressure-sensitive adhesive layer after curing with energy rays is determined according to JIS Z 0237 after the pressure-sensitive adhesive layer is attached to a silicon wafer and the pressure-sensitive adhesive layer is cured with energy rays. , the adhesive strength when the adhesive layer after curing is peeled off from the silicon wafer at an angle of 90° at a peeling speed of 600 mm/min. Specific measurement conditions will be described later in Examples.

(3.2 90° peeling adhesive force ratio of adhesive layer before and after energy beam curing)
In this embodiment, the ratio of the 90° peeling adhesive strength of the adhesive layer before and after energy ray curing is preferably 4% or less. That is, the adhesive strength when the adhesive layer before energy beam curing is peeled off from the silicon wafer so that the angle between the adhesive layer and the silicon wafer is 90° (hereinafter referred to as the adhesive layer before energy beam curing The ratio of the 90° peeling adhesive strength of the adhesive layer after energy beam curing (hereinafter also referred to as the adhesive strength ratio) to the 90° peeling adhesive strength is preferably 4% or less.

When the adhesive force ratio is within the above range, the adhesive layer is sufficiently adhered to the surface of the wafer during back grinding to protect the circuit, and after back grinding, the adhesive layer can be peeled off even if the wafer is thin. is facilitated, and breakage of the wafer can be suppressed.

The adhesive strength ratio is more preferably 3% or less, and even more preferably 2% or less. On the other hand, although the lower limit of the adhesive force ratio is not particularly limited, it is usually about 0.3%.

The 90° peeling adhesive strength of the pressure-sensitive adhesive layer before curing with energy rays is the 90° peeling strength of the pressure-sensitive adhesive layer after curing with energy rays, except for measuring the adhesive strength of the pressure-sensitive adhesive layer before curing with energy rays. It should be the same as the measurement method. Specific measurement conditions will be described later in Examples.

(3.3 Surface resistivity)
In the present embodiment, the surface resistivity of the adhesive layer after energy ray curing is preferably 5.1×10 ¹² Ω/cm ² or more and 1.0×10 ¹⁵ Ω/cm ² or less. This surface resistivity is the surface resistivity of the surface of the adhesive layer that is attached to the adherend (the surface 30a of the adhesive layer in FIG. 1A).

The present inventors have found that the amount of carbon-carbon double bonds in the pressure-sensitive adhesive layer before curing affects not only the adhesive strength of the pressure-sensitive adhesive layer after curing, but also the chargeability of the pressure-sensitive adhesive layer. . That is, even if the protective sheet for semiconductor processing according to the present embodiment has an antistatic layer, electrification of the wafer may cause adhesion of foreign matter or the like to the wafer. Therefore, in such a case, for example, by controlling the amount of energy ray-polymerizable carbon-carbon double bonds in the pressure-sensitive adhesive layer before curing, the surface resistivity of the pressure-sensitive adhesive layer is controlled, and the above-mentioned It is preferable to be within the range.

When the surface resistivity is within the above range, static electricity can easily escape from the protective sheet for semiconductor processing, and it is possible to suppress charging of the wafer during processing of the wafer to which the protective sheet for semiconductor processing is attached. . As a result, in the process of attaching the protective sheet for semiconductor processing to the surface of the wafer, the process of grinding the back surface of the wafer, the process of peeling off the protective sheet for semiconductor processing, the process of transporting the wafer after peeling the protective sheet for semiconductor processing, etc. , it is possible to suppress adhesion of foreign matter or the like to the wafer. Therefore, breakage and cracking of the wafer due to adherence of foreign matter and the like are suppressed.

If the surface resistivity is smaller than the above range, it indicates, for example, insufficient curing of the pressure-sensitive adhesive layer. As a result, if the thickness of the wafer after grinding is thin, the wafer may be damaged when the protective sheet for semiconductor processing is peeled off. In addition, part of the adhesive layer may remain attached to the wafer (adhesive residue).

The surface resistivity is more preferably 9.5×10 ¹⁴ Ω/cm ² or less, even more preferably 9.0×10 ¹⁴ Ω/cm ² or less. On the other hand, the surface resistivity is more preferably 5.2×10 ¹² Ω/cm ² or higher, even more preferably 5.5×10 ¹² Ω/cm ² or higher.

In this embodiment, surface resistivity is measured according to JIS K 7194. That is, the measurement is performed in the same manner as the measurement method specified in JIS K 7194, but the measurement conditions may be different. Specific measurement conditions will be described later in Examples.

(3.4 Composition of adhesive layer)
The composition of the adhesive layer is not particularly limited as long as the adhesive layer before curing has adhesiveness to the extent that it can protect the circuit surface of the wafer, and the adhesive strength of the adhesive layer after curing is within the above range. . In the present embodiment, the pressure-sensitive adhesive layer contains, for example, an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, etc., as a pressure-sensitive adhesive component (adhesive resin) capable of expressing pressure-sensitive adhesiveness. It is preferably composed of a composition (composition for pressure-sensitive adhesive layer).

In addition, the composition for the adhesive layer contains an energy ray-curable adhesive from the viewpoint of easily achieving the adhesive strength and adhesive strength ratio after energy ray curing.

(3.5 Composition for adhesive layer)
As described above, since the pressure-sensitive adhesive layer is energy ray-curable, it is formed from an energy ray-curable composition (composition for pressure-sensitive adhesive layer). Below, the composition for adhesive layers is demonstrated.

The composition for the pressure-sensitive adhesive layer may have energy ray-curable properties by blending an energy ray-curable compound separately from the adhesive resin, but the adhesive resin itself has energy ray-curable properties. is preferred. When the adhesive resin itself has energy ray curability, an energy ray polymerizable group is introduced into the adhesive resin, and the energy ray polymerizable group is preferably introduced into the main chain or side chain of the adhesive resin. .

In addition, when an energy ray-curable compound is blended separately from the adhesive resin, a monomer or oligomer having an energy ray-polymerizable group is used as the energy ray-curable compound. The oligomer has a weight-average molecular weight (Mw) of less than 10,000, such as urethane (meth)acrylate.

In the present embodiment, from the viewpoint of controlling the amount of energy ray-polymerizable carbon-carbon double bonds, it is preferably 0.1 to 300 parts by mass with respect to 100 parts by mass of the adhesive resin that does not have energy ray-curable properties. , more preferably 0.5 to 200 parts by mass, more preferably 1 to 150 parts by mass.

Hereinafter, the case where the energy ray-curable adhesive resin contained in the adhesive layer composition is an energy ray-curable acrylic polymer (hereinafter also referred to as "acrylic polymer (A)"). A more detailed description will be given.

(3.5.1 Acrylic polymer (A))
The acrylic polymer (A) is an acrylic polymer into which an energy ray-polymerizable group is introduced and which has structural units derived from (meth)acrylate. The energy ray-polymerizable group is preferably introduced into the side chain of the acrylic polymer.

The acrylic polymer (A) is an acrylic copolymer (A0) having structural units derived from the alkyl (meth)acrylate (a1) and structural units derived from the functional group-containing monomer (a2), and is subjected to energy beam polymerization. It is preferably a reactant obtained by reacting a polymerizable compound (Xa) having a functional group.

As the alkyl (meth)acrylate (a1), an alkyl (meth)acrylate having an alkyl group with 1 to 18 carbon atoms is used. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate ) acrylates and the like.

Among these, the alkyl (meth)acrylate (a1) is preferably an alkyl (meth)acrylate having an alkyl group with 4 to 8 carbon atoms. Specifically, 2-ethylhexyl (meth)acrylate and n-butyl (meth)acrylate are preferred, and n-butyl (meth)acrylate is more preferred. In addition, they may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the structural unit derived from the alkyl (meth)acrylate (a1) in the acrylic copolymer (A0) is adjusted to the acrylic copolymer (A0) from the viewpoint of improving the adhesive strength of the pressure-sensitive adhesive layer to be formed. is preferably 40 to 98% by mass, more preferably 45 to 95% by mass, and still more preferably 50 to 90% by mass, relative to the total structural units (100% by mass) of.

For example, the alkyl (meth)acrylate (a1) may contain ethyl (meth)acrylate, methyl (meth)acrylate, etc. in addition to the above 2-ethylhexyl (meth)acrylate and n-butyl (meth)acrylate. good. By containing these monomers, it becomes easier to adjust the adhesive performance of the adhesive layer to a desired one.

The functional group-containing monomer (a2) is a monomer having a functional group such as a hydroxy group, a carboxyl group, an epoxy group, an amino group, a cyano group, a nitrogen atom-containing ring group, an alkoxysilyl group, or the like. As the functional group-containing monomer (a2), among those mentioned above, one or more selected from hydroxyl group-containing monomers, carboxy group-containing monomers, and epoxy group-containing monomers are preferable.

Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl ( hydroxyalkyl (meth)acrylates such as meth)acrylate and 4-hydroxybutyl (meth)acrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol.

Carboxy group-containing monomers include (meth)acrylic acid, maleic acid, fumaric acid, and itaconic acid.

Epoxy-containing monomers include epoxy group-containing (meth)acrylic acid esters and non-acrylic epoxy group-containing monomers. Examples of epoxy group-containing (meth)acrylic esters include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, (3,4-epoxycyclohexyl)methyl (meth)acrylate, 3-epoxycyclo-2- Hydroxypropyl (meth)acrylate and the like. Examples of non-acrylic epoxy group-containing monomers include glycidyl crotonate and allyl glycidyl ether.

The functional group-containing monomer (a2) may be used alone or in combination of two or more.

Among the above-mentioned functional group-containing monomers (a2), hydroxy group-containing monomers are more preferable, hydroxyalkyl (meth)acrylates are more preferable, and 2-hydroxyethyl (meth)acrylate is even more preferable.

By using a hydroxyalkyl (meth)acrylate as the component (a2), it becomes possible to relatively easily react the acrylic copolymer (A0) with the polymerizable compound (Xa).

The content of structural units derived from the functional group-containing monomer (a2) in the acrylic copolymer (A0) is preferably 1 based on the total structural units (100% by mass) of the acrylic copolymer (A0). ~35% by mass, more preferably 3 to 32% by mass, still more preferably 6 to 30% by mass.

If the content is 1% by mass or more, a certain amount of functional groups that serve as reaction points with the polymerizable compound (Xa) can be secured. Therefore, the pressure-sensitive adhesive layer can be appropriately cured by irradiation with energy rays, so that the adhesive strength after irradiation with energy rays can be reduced. Moreover, if the content is 30% by mass or less, sufficient pot life can be ensured when the solution of the adhesive layer composition is applied to form the adhesive layer.

The acrylic copolymer (A0) may be a copolymer of an alkyl (meth)acrylate (a1) and a functional group-containing monomer (a2). It may be a copolymer with a monomer (a3) other than the components (a1) and (a2).

Other monomers (a3) include, for example, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxy Examples include (meth)acrylates having a cyclic structure such as ethyl (meth)acrylate, vinyl acetate, styrene, and the like. Other monomers (a3) may be used singly or in combination of two or more.

The content of structural units derived from the other monomer (a3) in the acrylic copolymer (A0) is preferably 0 to 30% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass.

The polymerizable compound (Xa) includes an energy ray-polymerizable group and a substituent capable of reacting with a functional group in the structural unit derived from the (a2) component of the acrylic copolymer (A0) (hereinafter simply referred to as "reactive substitution (also referred to as "group").

The energy ray-polymerizable group may be any group containing an energy ray-polymerizable carbon-carbon double bond. For example, a (meth)acryloyl group, a vinyl group and the like can be mentioned, and a (meth)acryloyl group is preferred. Moreover, the polymerizable compound (Xa) is preferably a compound having 1 to 5 energy ray-polymerizable groups per molecule.

The reactive substituent in the polymerizable compound (Xa) may be appropriately changed according to the functional group of the functional group-containing monomer (a2). From the viewpoint of reactivity and the like, an isocyanate group is preferred. When the polymerizable compound (Xa) has an isocyanate group, for example, when the functional group of the functional group-containing monomer (a2) is a hydroxy group, it can easily react with the acrylic copolymer (A0). become.

Specific polymerizable compounds (Xa) include, for example, (meth)acryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acryloyl isocyanate, allyl isocyanate, glycidyl (meth)acrylate, (Meth) acrylic acid and the like. These polymerizable compounds (Xa) may be used alone or in combination of two or more.

Among these, (meth)acryloyloxyethyl Isocyanates are preferred.

From the viewpoint of controlling the amount of energy ray polymerizable carbon-carbon double bonds, the polymerizable compound (Xa) is added to the total amount of functional groups derived from the functional group-containing monomer (a2) in the acrylic copolymer (A0) (100 equivalents ), preferably 50 to 98 equivalents, more preferably 55 to 93 equivalents are reacted with the functional group.

The weight average molecular weight (Mw) of the acrylic polymer (A) is preferably 300,000 to 1,600,000, more preferably 400,000 to 1,400,000. By having such Mw, it becomes possible to impart appropriate adhesiveness to the adhesive layer.

Even if the adhesive resin has energy ray-curable properties, the composition for the adhesive layer preferably contains an energy ray-curable compound other than the adhesive resin. As such an energy ray-curable compound, a monomer or oligomer having an unsaturated group in the molecule and capable of being polymerized and cured by energy ray irradiation is preferable.

Specifically, for example, trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth) Polyvalent (meth)acrylate monomers such as acrylates and 1,6-hexanediol (meth)acrylates, oligomers such as urethane (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, and epoxy (meth)acrylates is mentioned.

Among these, urethane (meth)acrylate oligomers are preferable from the viewpoint of having a relatively high molecular weight and keeping the surface resistivity of the pressure-sensitive adhesive layer within the range described above.

From the viewpoint of controlling the energy ray-polymerizable carbon-carbon double bond content, the content of the energy ray-curable compound is preferably 0.1 to 300 mass parts with respect to 100 mass parts of the acrylic polymer (A). parts, more preferably 0.5 to 200 parts by mass, and still more preferably 1 to 150 parts by mass.

(3.5.2 Cross-linking agent)
The adhesive layer composition preferably further contains a cross-linking agent. The pressure-sensitive adhesive layer composition is crosslinked by a crosslinking agent, for example, by being heated after application. By cross-linking the acrylic polymer (A) with a cross-linking agent, the pressure-sensitive adhesive layer is appropriately formed as a coating film and easily exhibits its function as a pressure-sensitive adhesive layer.

Examples of cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, aziridine-based cross-linking agents, and chelate-based cross-linking agents. Among these, isocyanate-based cross-linking agents are preferred. You may use a crosslinking agent individually or in combination of 2 or more types.

Examples of isocyanate-based cross-linking agents include polyisocyanate compounds. Specific examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. etc. Also included are biuret and isocyanurate forms thereof, as well as adduct forms which are reactants with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane and castor oil.

Among the above, polyhydric alcohol (for example, trimethylolpropane, etc.) adducts of aromatic polyisocyanates such as tolylene diisocyanate are preferred.

The content of the cross-linking agent is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, based on 100 parts by mass of the acrylic polymer (A).

(3.5.3 Photoinitiator)
The adhesive layer composition preferably further contains a photopolymerization initiator. When the composition for the pressure-sensitive adhesive layer contains a photopolymerization initiator, it becomes easier to proceed the energy ray curing of the composition for the pressure-sensitive adhesive layer by ultraviolet light or the like.

Examples of photopolymerization initiators include acetophenone, 2,2-diethoxybenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, Michler's ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyldiphenisulfide, tetramethylthiuram monosulfide, benzyldimethylketal, dibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-ethylanthraquinone, 2,2-dimethoxy-1,2-diphenylethane- 1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl )-butanone-1,2-hydroxy-2-methyl-1-phenyl-propan-1-one, diethylthioxanthone, isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide and other low molecular weight polymerization initiators , oligomerized polymerization initiators such as oligo{2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone}.

The photopolymerization initiator may be used alone or in combination of two or more. Among the above, 2,2-dimethoxy-1,2-diphenylethan-1-one and 1-hydroxycyclohexylphenyl ketone are preferred.

The content of the photopolymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and still more preferably 0.05 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). ~5 parts by mass.

The composition for the pressure-sensitive adhesive layer may contain other additives as long as they do not impair the effects of the present invention. Other additives include, for example, tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, and the like. When these additives are contained, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.02 to 2 parts by mass, relative to 100 parts by mass of the acrylic polymer (A). part by mass.

The adhesive strength of the pressure-sensitive adhesive layer can be adjusted by, for example, the type and amount of monomers constituting the acrylic polymer (A), the amount of energy ray-polymerizable groups introduced into the acrylic polymer (A), and the like. is. Also, the surface resistivity of the pressure-sensitive adhesive layer can be adjusted to some extent. The above describes the preferred range of the amount of the energy ray-polymerizable group to be introduced into the acrylic polymer (A). , the surface resistivity tends to be high. However, the adhesive strength and surface resistivity of the adhesive layer can be adjusted by factors other than the above factors. For example, it can be appropriately adjusted by adjusting the amount of the cross-linking agent and the amount of the photopolymerization initiator mixed in the pressure-sensitive adhesive layer.

(4. Antistatic layer)
The antistatic layer is arranged between the substrate and the adhesive layer. In the antistatic layer, the antistatic component can suppress an increase in static voltage due to leakage of static charge resulting from processing of the wafer to which the protective sheet for semiconductor processing is adhered. The composition of the antistatic layer may have such an antistatic property that the peeling electrostatic voltage when peeling the pressure-sensitive adhesive layer from a wafer or the like can be reduced to a predetermined value or less. In this embodiment, it is preferable that the peeling electrification voltage is 500 V or less.

The thickness of the antistatic layer is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 60 nm or more. Also, the thickness is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less.

(4.1 Composition for antistatic layer)
In this embodiment, the antistatic layer is preferably composed of a composition containing a polymer compound (composition for antistatic layer). Examples of such a composition include a composition containing a conductive polymer compound as an antistatic component, a composition containing an antistatic component and a polymer compound, and the like. The antistatic layer composition is preferably a composition containing a conductive polymer compound.

Examples of conductive polymer compounds include polythiophene-based polymers, polypyrrole-based polymers, and polyaniline-based polymers. In this embodiment, a polythiophene-based polymer is preferred.

Polythiophene-based polymers include, for example, polythiophene, poly(3-alkylthiophene), poly(3-thiophene-β-ethanesulfonic acid), mixtures of polyalkylenedioxythiophenes and polystyrene sulfonate (PSS) (doped including) and the like. Among these, a mixture of polyalkylenedioxythiophene and polystyrene sulfonate is preferred. Examples of the polyalkylenedioxythiophene include poly(3,4-ethylenedioxythiophene) (PEDOT), polypropylenedioxythiophene, poly(ethylene/propylene)dioxythiophene, etc. Among them, poly(3,4- ethylenedioxythiophene) is preferred. That is, among the above, a mixture of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate (PSS-doped PEDOT) is particularly preferred.

Examples of polypyrrole-based polymers include polypyrrole, poly-3-methylpyrrole, and poly-3-octylpyrrole.

Examples of polyaniline-based polymers include polyaniline, polymethylaniline, and polymethoxyaniline.

A composition containing an antistatic component and a polymer compound includes a composition containing an antistatic component and a binder resin. Examples of the antistatic component include the above conductive polymer compounds, surfactants, ionic liquids, conductive inorganic compounds, and the like.

The surfactant may be at least one selected from cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. Examples include cationic surfactants containing quaternary ammonium salts. Examples of conductive inorganic compounds include various metals and conductive oxides.

Also, the binder resin is not particularly limited. Examples thereof include polyester resins, acrylic resins, polyvinyl resins, urethane resins, melamine resins, and epoxy resins. Moreover, you may use a crosslinking agent together. Examples of cross-linking agents include methylolated or alkylolated melamine compounds, urea compounds, glyoxal compounds, acrylamide compounds, epoxy compounds, isocyanate compounds, and the like.

The content of the antistatic agent in the antistatic layer composition may be appropriately determined according to the desired antistatic performance. Specifically, the content of the antistatic agent in the antistatic layer composition is preferably 0.1 to 20% by mass.

(5. Buffer layer)
As described above, in the protective sheet for semiconductor processing shown in FIG. 1B, the buffer layer is formed on the main surface opposite to the main surface of the substrate on which the pressure-sensitive adhesive layer is formed. The buffer layer will be described below.

The buffer layer is a layer that is softer than the base material, and relieves stress during grinding of the backside of the wafer to prevent cracking and chipping of the wafer. In addition, the wafer to which the protective sheet for semiconductor processing is attached is placed on the vacuum table through the protective sheet for semiconductor processing during back grinding. It is easier to hold properly on the vacuum table.

Such a buffer layer is useful when processing wafers by DBG, especially LDBG.

The thickness of the buffer layer is preferably 5-100 μm, more preferably 1-100 μm, and even more preferably 5-80 μm. By setting the thickness of the buffer layer within the above range, the buffer layer can appropriately relax the stress during back grinding.

The buffer layer may be a layer formed from a buffer layer composition containing an energy ray-polymerizable compound, a polypropylene film, an ethylene-vinyl acetate copolymer film, an ionomer resin film, an ethylene/(meth)acrylic film. Films such as acid copolymer films, ethylene/(meth)acrylate copolymer films, LDPE films, and LLDPE films may be used.

(5.1 Composition for buffer layer)
A buffer layer composition containing an energy ray-polymerizable compound can be cured by being irradiated with an energy ray.

Further, the buffer layer composition containing the energy ray-polymerizable compound is more specifically polymerizable having a urethane (meth)acrylate (b1) and an alicyclic or heterocyclic group having 6 to 20 ring-forming atoms. It preferably contains the compound (b2). In addition to the components (b1) and (b2), the buffer layer composition may contain a polymerizable compound (b3) having a functional group. The buffer layer composition may also contain a photopolymerization initiator in addition to the above components. Furthermore, the buffer layer composition may contain other additives and resin components within a range that does not impair the effects of the present invention.

Each component contained in the buffer layer composition containing the energy ray-polymerizable compound will be described in detail below.

(5.1.1 Urethane (meth)acrylate (b1))
The urethane (meth)acrylate (b1) is a compound having at least a (meth)acryloyl group and a urethane bond, and has the property of being polymerized and cured by energy ray irradiation. Urethane (meth)acrylates (b1) are oligomers or polymers.

The weight average molecular weight (Mw) of component (b1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, still more preferably 3,000 to 20,000. In addition, the number of (meth)acryloyl groups (hereinafter also referred to as "number of functional groups") in component (b1) may be monofunctional, difunctional, or trifunctional or more, but is preferably monofunctional or difunctional. .

Component (b1) can be obtained, for example, by reacting a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound and a polyvalent isocyanate compound with a (meth)acrylate having a hydroxyl group. In addition, you may use a component (b1) individually or in combination of 2 or more types.

The polyol compound used as the raw material for component (b1) is not particularly limited as long as it is a compound having two or more hydroxy groups. Any of difunctional diols, trifunctional triols, and tetrafunctional or higher polyols may be used, but bifunctional diols are preferred, and polyester type diols or polycarbonate type diols are more preferred.

Examples of polyvalent isocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; Alicyclic diisocyanates such as ,4'-diisocyanate, ω,ω'-diisocyanatedimethylcyclohexane; 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, naphthalene- aromatic diisocyanates such as 1,5-diisocyanate;

Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferred.

A urethane (meth)acrylate (b1) can be obtained by reacting a (meth)acrylate having a hydroxyl group with a terminal isocyanate urethane prepolymer obtained by reacting the above-mentioned polyol compound and a polyvalent isocyanate compound. The (meth)acrylate having a hydroxy group is not particularly limited as long as it is a compound having a hydroxy group and a (meth)acryloyl group in at least one molecule.

Specific (meth)acrylates having a hydroxy group include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth) Acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, etc. hydroxyalkyl (meth)acrylate; hydroxy group-containing (meth)acrylamide such as N-methylol (meth)acrylamide; vinyl alcohol, vinylphenol, reaction obtained by reacting diglycidyl ester of bisphenol A with (meth)acrylic acid things; and the like.

Among these, hydroxyalkyl (meth)acrylates are preferred, and 2-hydroxyethyl (meth)acrylate is more preferred.

The content of the component (b1) in the buffer layer composition is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, based on the total amount (100% by mass) of the buffer layer composition. It is preferably 25 to 55% by mass.

(5.1.2 Polymerizable Compound (b2) Having an Alicyclic or Heterocyclic Group Having 6 to 20 Ring-forming Atoms)
Component (b2) is a polymerizable compound having an alicyclic or heterocyclic group having 6 to 20 ring atoms, and more preferably a compound having at least one (meth)acryloyl group. Compounds having one (meth)acryloyl group are preferred. By using the component (b2), it is possible to improve the film formability of the obtained buffer layer composition.

Specific components (b2) include, for example, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, cyclohexyl (meth)acrylate, alicyclic group-containing (meth)acrylates such as adamantane (meth)acrylate; heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate; and the like. In addition, you may use a component (b2) individually or in combination of 2 or more types. Isobornyl (meth)acrylate is preferred among alicyclic group-containing (meth)acrylates, and tetrahydrofurfuryl (meth)acrylate is preferred among heterocyclic group-containing (meth)acrylates.

The content of the component (b2) in the buffer layer composition is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, based on the total amount (100% by mass) of the buffer layer composition. It is preferably 25 to 55% by mass.

(5.1.3 Polymerizable compound having a functional group (b3))
Component (b3) is a polymerizable compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group, or an amino group, and is preferably a compound having at least one (meth)acryloyl group. Compounds having one (meth)acryloyl group are preferred.

The component (b3) has good compatibility with the component (b1), and it becomes easy to adjust the viscosity of the buffer layer composition to an appropriate range. Moreover, even if the buffer layer is made relatively thin, the buffer performance is improved.

Examples of component (b3) include hydroxyl group-containing (meth)acrylates, epoxy group-containing compounds, amide group-containing compounds, amino group-containing (meth)acrylates, and the like. Among these, hydroxyl group-containing (meth)acrylates are preferred.

Examples of hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxy Butyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, phenylhydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl acrylate and the like. Among these, hydroxyl group-containing (meth)acrylates having an aromatic ring such as phenylhydroxypropyl (meth)acrylate are more preferable.

Note that the component (b3) may be used alone or in combination of two or more. The content of the component (b3) in the buffer layer composition is preferably 5% with respect to the total amount (100% by mass) of the buffer layer composition in order to improve the film-forming properties of the buffer layer composition. ~40% by mass, more preferably 7 to 35% by mass, still more preferably 10 to 30% by mass.

(5.1.4 Polymerizable compound (b4) other than components (b1) to (b3))
The buffer layer-forming composition may contain a polymerizable compound (b4) other than the components (b1) to (b3) as long as the effects of the present invention are not impaired.

Examples of component (b4) include alkyl (meth)acrylates having an alkyl group having 1 to 20 carbon atoms; styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam, and the like. vinyl compound of: and the like. In addition, you may use a component (b4) individually or in combination of 2 or more types.

The content of component (b4) in the buffer layer-forming composition is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, even more preferably 0 to 5% by mass, and particularly preferably 0 to 2% by mass. %.

(5.1.5 Photoinitiator)
The buffer layer composition preferably further contains a photopolymerization initiator from the viewpoint of shortening the polymerization time by energy ray irradiation and reducing the amount of energy ray irradiation when forming the buffer layer.

Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. Specifically, for example, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzylphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyrolnitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and the like.

These photopolymerization initiators can be used alone or in combination of two or more.

The content of the photopolymerization initiator in the buffer layer composition is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, with respect to 100 parts by mass of the total amount of the energy ray-polymerizable compound. parts, more preferably 0.3 to 5 parts by mass.

(5.1.6 Other Additives)
The buffer layer composition may contain other additives as long as the effects of the present invention are not impaired. Other additives include, for example, antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, and the like. When these additives are blended, the content of each additive in the buffer layer composition is preferably 0.01 to 6 parts by mass, more than It is preferably 0.1 to 3 parts by mass.

The buffer layer formed from the buffer layer composition containing the energy ray-polymerizable compound is obtained by polymerizing and curing the buffer layer composition having the above composition by energy ray irradiation. That is, the buffer layer is a hardened material of the buffer layer composition.

Therefore, the buffer layer preferably contains polymerized units derived from component (b1) and polymerized units derived from component (b2). Moreover, the buffer layer may contain polymerized units derived from the component (b3), or may contain polymerized units derived from the component (b4). The content ratio of each polymer unit in the buffer layer usually corresponds to the ratio (feed ratio) of each component constituting the composition for the buffer layer.

(6. Release sheet)
A release sheet may be attached to the surface of the protective sheet for semiconductor processing. Specifically, the release sheet is attached to the surface of the pressure-sensitive adhesive layer of the protective sheet for semiconductor processing. The release sheet is attached to the surface of the adhesive layer to protect the adhesive layer during transportation and storage. The release sheet is releasably attached to the semiconductor processing protective sheet, and is peeled off and removed from the semiconductor processing protective sheet before the semiconductor processing protective sheet is used (that is, before the wafer is attached).

As the release sheet, a release sheet having at least one surface subjected to a release treatment is used, and specific examples include a release sheet base material coated with a release agent on the surface.

As the substrate for the release sheet, a resin film is preferable, and as the resin constituting the resin film, for example, polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polypropylene resin, polyethylene resin, etc. and the like polyolefin resins. Examples of release agents include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, fluorine-based resins, and the like.

Although the thickness of the release sheet is not particularly limited, it is preferably 10 to 200 μm, more preferably 20 to 150 μm.

(7. Manufacturing method of protective sheet for semiconductor processing)
The method for producing the protective sheet for semiconductor processing according to the present embodiment is not particularly limited as long as it is a method capable of forming an antistatic layer and an adhesive layer on the main surface of the substrate, and a known method may be used. A method of manufacturing the protective sheet for semiconductor processing shown in FIG. 1A will be described below.

First, as a composition for forming an antistatic layer, for example, an antistatic layer composition containing the above-described components or a composition obtained by diluting the antistatic layer composition with a solvent or the like is prepared. Similarly, the adhesive layer composition for forming the adhesive layer may be, for example, a pressure-sensitive adhesive layer composition containing the above-described components, or a composition obtained by diluting the pressure-sensitive adhesive layer composition with a solvent or the like. prepare things. Similarly, as the buffer layer composition for forming the buffer layer, for example, a buffer layer composition containing the above-described components, or a composition obtained by diluting the buffer layer composition with a solvent or the like is prepared. .

Examples of solvents include organic solvents such as methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol and isopropanol.

First, the antistatic layer composition is applied to the release-treated surface of the first release sheet by spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating. The antistatic layer is formed on the first release sheet by coating and drying by heating by a known method such as a method. After that, the antistatic layer on the first release sheet and one surface of the substrate are attached together, and the first release sheet is removed.

Subsequently, the adhesive layer composition is applied to the release-treated surface of the second release sheet by a known method, and dried by heating to form an adhesive layer on the second release sheet. After that, the adhesive layer on the second release sheet and the antistatic layer on the substrate are laminated to form an antistatic layer and an adhesive layer in this order on one main surface of the substrate. A protective sheet for semiconductor processing can be obtained. The second release sheet may be removed when the protective sheet for semiconductor processing is used.

Also, in the case of manufacturing the protective sheet for semiconductor processing shown in FIG. 1B, the following should be done.

A buffer layer composition is applied to the release-treated surface of the third release sheet by a known method to form a coating film, and this coating film is semi-cured to form a buffer layer film on the release sheet. The buffer layer film formed on the release sheet is adhered to the other surface of the substrate, and the buffer layer film is completely cured to form a buffer layer on the substrate.

In the present embodiment, the coating film is preferably cured by irradiation with energy rays. Moreover, the curing of the coating film may be performed in one curing process, or may be performed in a plurality of times.

It is preferable to form the antistatic layer and the adhesive layer after forming the buffer layer on the substrate.

(8. Manufacturing method of semiconductor device)
The protective sheet for semiconductor processing according to the present invention is preferably used to protect the surface of a wafer by attaching it to the surface of the wafer when the back surface of the wafer is ground.

As a non-limiting example of use of the protective sheet for semiconductor processing, the method for manufacturing a semiconductor device will be described in more detail below.

Specifically, the method for manufacturing a semiconductor device includes at least steps 1 to 3 below.
Step 1: A step of attaching the protective sheet for semiconductor processing to the surface of the wafer Step 2: A step of grinding the wafer with the protective sheet for semiconductor processing attached to the surface from the back side Step 3: The wafer after back grinding The process of peeling off the protective sheet for semiconductor processing from

Each step of the method for manufacturing the semiconductor device will be described in detail below.

(Step 1)
In step 1, as shown in FIG. 2, the main surface 30a of the adhesive layer 30 of the protective sheet for semiconductor processing 1 according to the present embodiment is attached to the surface 100a of the semiconductor wafer 100 . By attaching the protective sheet for semiconductor processing to the surface of the semiconductor wafer, the surface of the semiconductor wafer is sufficiently protected.

The semiconductor wafer used in this manufacturing method may be a silicon wafer, a wafer of gallium arsenide, silicon carbide, lithium tantalate, lithium niobate, gallium nitride, indium phosphide, or the like, or a glass wafer. . In this embodiment, the semiconductor wafer is preferably a silicon wafer.

Although the thickness of the semiconductor wafer before grinding is not particularly limited, it is usually about 500 to 1000 μm. A semiconductor wafer usually has a circuit formed on its surface. Formation of circuits on the wafer surface can be performed by various methods including conventional methods such as an etching method and a lift-off method.

A semiconductor wafer to which a protective sheet for semiconductor processing is attached is placed on a chuck table and held by being sucked by the chuck table. At this time, the semiconductor wafer is sucked with its surface side arranged on the table side.

(Step 2)
After step 1, the backside of the semiconductor wafer on the chuck table is ground to obtain a wafer after backside grinding. In this embodiment, the thickness of the wafer after backside grinding is not particularly limited, but is, for example, 100 μm or less. When the thickness of the wafer after backside grinding is within the above range, the size and height of the semiconductor chip can be easily reduced.

(Step 3)
Next, the protective sheet for semiconductor processing is peeled off from the semiconductor wafer. This step is performed, for example, by the following method.

In this embodiment, since the adhesive layer of the protective sheet for semiconductor processing is formed from an energy ray-curable adhesive, the adhesive layer is cured and shrunk by irradiation with an energy ray, thereby increasing the adhesive force to the adherend. Lower. Next, a pick-up tape is attached to the rear surface side of the semiconductor wafer after the rear surface is ground, and the position and direction are adjusted so that the semiconductor wafer can be picked up. At this time, the ring frame arranged on the outer peripheral side of the wafer is also attached to the pickup tape, and the outer peripheral edge of the pickup tape is fixed to the ring frame. The wafer and the ring frame may be attached to the pickup tape at the same time, or may be attached at separate timings. Next, the protective sheet for semiconductor processing is peeled off from the semiconductor wafer held on the pickup tape.

Since the semiconductor processing protective sheet according to the present embodiment has the above-described properties, even when the thickness of the semiconductor wafer after backside grinding is thin, the semiconductor processing protective sheet can be removed from the semiconductor wafer after backside grinding. Even if the is peeled off, breakage of the semiconductor wafer can be suppressed, and electrification can be suppressed.

After that, multiple semiconductor chips on the pickup tape are picked up and fixed on a substrate or the like to manufacture a semiconductor device.

Although the pickup tape is not particularly limited, it is composed of, for example, a base material and an adhesive sheet having an adhesive layer provided on one side of the base material.

In addition, the protective sheet for semiconductor processing according to the present invention is also suitably used in a method of manufacturing a semiconductor device using a pre-dicing method. In this case, it is preferable to use the protective sheet for semiconductor processing shown in FIG. 1B as the protective sheet for semiconductor processing.

In the method of manufacturing a semiconductor device using the pre-dicing method, in addition to the above steps 1 to 3, grooves are formed from the front surface side of the semiconductor wafer, or reforming is performed inside the semiconductor wafer from the front surface or the back surface of the semiconductor wafer. A step of forming a region (step 4) is included.

When forming a modified region on a semiconductor wafer, it is preferable to perform step 1 before step 4. On the other hand, when grooves are formed on the surface of the semiconductor wafer by dicing or the like, step 1 is performed after step 4. FIG. That is, in step 1, a protective sheet for semiconductor processing is attached to the surface of the wafer having grooves formed in step 4, which will be described later.

In step 4, grooves are formed from the surface side of the semiconductor wafer. Alternatively, a modified region is formed inside the semiconductor wafer from the front surface or rear surface of the semiconductor wafer.

The grooves formed in this process are shallower than the thickness of the semiconductor wafer. The grooves can be formed by dicing using a conventionally known wafer dicing device or the like. Further, the semiconductor wafer is divided into a plurality of semiconductor chips along the grooves by back-grinding in step 3 described above.

In addition, the modified region is an embrittled portion of the semiconductor wafer, and the semiconductor wafer is thinned by grinding in the grinding process, and the modified region of the semiconductor wafer is destroyed by the application of grinding force. It is a starting point for separating into semiconductor chips. That is, in step 4, the grooves and modified regions are formed along the dividing lines along which the semiconductor wafer is divided into individual semiconductor chips in step 3 described above.

The modified region is formed by laser irradiation focused on the inside of the semiconductor wafer, and the modified region is formed inside the semiconductor wafer. The laser irradiation may be performed from the front side or the back side of the semiconductor wafer. In the mode of forming the modified region, when step 4 is performed after step 1 and laser irradiation is performed from the wafer surface, the semiconductor wafer is irradiated with the laser through the protective sheet for semiconductor processing.

In the pre-dicing method, when grooves are formed in the semiconductor wafer, the backside grinding in step 2 is performed so as to thin the semiconductor wafer to at least the bottom of the grooves. By this back-grinding, the grooves become cuts penetrating the wafer, and the semiconductor wafer is divided by the cuts into individual semiconductor chips.

On the other hand, when the modified region is formed, the ground surface (wafer back surface) may reach the modified region by grinding, but it does not have to reach the modified region strictly. That is, the semiconductor wafer may be ground from the modified region to a position close to the modified region so that the semiconductor wafer is broken into individual semiconductor chips starting from the modified region. For example, the actual singulation of the semiconductor chips may be performed by applying a pick-up tape, which will be described later, and then stretching the pick-up tape.

Also, after the backside grinding is completed, dry polishing may be performed prior to picking up the chips.

The shape of the individualized semiconductor chips may be a square or an elongated shape such as a rectangle. Although the thickness of the individualized semiconductor chips is not particularly limited, it is preferably about 5 to 100 μm, more preferably 10 to 45 μm. According to LDBG, a modified region is provided inside the wafer with a laser, and the wafer is singulated by stress or the like during wafer backside grinding. ∼45 μm becomes easy. The size of the individualized semiconductor chips is not particularly limited, but the chip size is preferably less than 600 mm ² , more preferably less than 400 mm ² , still more preferably less than 120 mm ² .

Step 3 may be performed as described above, but the protective sheet for semiconductor processing is peeled off from the individualized semiconductor wafers. Even in this case, it is possible to suppress breakage of the singulated semiconductor wafers and to suppress charging.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to the above embodiments, and may be modified in various ways within the scope of the present invention.

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

The measurement method and evaluation method in this example are as follows.

(90° peeling adhesive strength of adhesive layer before and after energy ray curing)
The protective sheets for semiconductor processing produced in Examples and Comparative Examples were cut to a width of 25 mm to obtain test pieces. The pressure-sensitive adhesive layer of the test piece was applied to a silicon mirror wafer having no circuit surface formed thereon with a roller having a mass of 2 kg. After leaving it for 1 hour, the test piece was peeled off at a peeling speed of 600 mm / min so that it was 90° to the silicon mirror wafer in accordance with JIS Z 0237, and the adhesive strength (the pressure-sensitive adhesive layer before curing with the energy beam 90° peel adhesion) was measured.

Also, the pressure-sensitive adhesive layer of another test piece was attached to the silicon mirror wafer with a roller having a mass of 2 kg. The pressure-sensitive adhesive layer of this test piece was irradiated with ultraviolet rays from the substrate side of the protective sheet for semiconductor processing under the conditions of an illuminance of 220 mW/cm ² and a light amount of 380 mJ/cm ² to cure the pressure-sensitive adhesive layer. In accordance with JIS Z 0237, the test piece was peeled off at a peeling speed of 600 mm / min so that it was 90 ° to the silicon mirror wafer, and the adhesive strength (90 ° peeling adhesive strength of the adhesive layer after energy ray curing ) was measured.

(Surface resistivity of adhesive layer after energy ray curing)
The protective sheets for semiconductor processing prepared in Examples and Comparative Examples were cut into a size of 10 cm×10 cm, and the pressure-sensitive adhesive layer of the protective sheet for semiconductor processing was irradiated with ultraviolet rays to be cured. The surface resistivity of the adhesive layer after curing was measured according to JIS K 7194 under the conditions of 23° C., 50% RH, and an applied voltage of 100 V using a surface resistivity meter R8252 manufactured by Advantest.

(Peeling electrification voltage of protective sheet for semiconductor processing)
The protective sheet for semiconductor processing prepared in Examples and Comparative Examples was attached to the surface of a silicon wafer, and a wafer mounter (product name “RAD-2700F/12”, manufactured by Lintec) was used to peel off at a rate of 600 mm / min and at a temperature of While peeling the protective sheet for semiconductor processing from the silicon wafer at 40° C., the voltage is measured at a place 10 mm away from the wafer surface and the peeling surface side of the adhesive layer using a Prostat peeling electrification meter PFM-711A. Then, the voltage value on the wafer side was taken as the peeling electrification voltage value. In this example, samples with a peeling electrification voltage of 500 V or less were judged to be good.

(Crack occurrence rate)
A silicon wafer with a diameter of 12 inches and a thickness of 775 μm is attached to a protective sheet for semiconductor processing prepared in Examples and Comparative Examples using a tape laminator for back grinding (manufactured by Lintec, device name “RAD-3510F/12”). bottom. Using a laser saw (manufactured by Disco, device name "DFL7361"), a grid-shaped modified region was formed on the wafer. Note that the grid size was 10 mm×10 mm.

Next, using a back surface grinding machine (manufactured by Disco, machine name "DGP8761"), the wafer was ground (including dry polishing) to a thickness of 30 µm, and the wafer was singulated into a plurality of chips.

After the grinding step, energy rays (ultraviolet rays) were irradiated, and a dicing tape (Adwill D-175, manufactured by Lintec Corporation) was attached to the opposite side of the protective sheet for semiconductor processing, and then the protective sheet for semiconductor processing was peeled off. After that, the individualized chips were observed with a digital microscope (product name "VHX-1000", manufactured by KEYENCE), and the chips with cracks were counted and classified according to the size of the cracks according to the following criteria. Note that the crack size (μm) is obtained by comparing the crack length (μm) along the vertical direction of the chip and the crack length (μm) along the horizontal direction of the chip, and the larger of the values. and
(standard)
Large crack: Crack size greater than 50 μm Medium crack: Crack size 20 μm or more and 50 μm or less Small crack: Crack size less than 20 μm

Also, the crack generation rate (%) was calculated based on the following formula. If the crack generation rate is 2.0% or less, the number of large cracks is 0, the number of medium cracks is 10 or less, and the number of small cracks is 20 or less, it is "good". Poor”.
Crack occurrence rate (%) = (number of cracked chips/total number of chips) x 100

(Example 1)
(1) Adhesive layer (Preparation of composition for adhesive layer)
An acrylic polymer obtained by copolymerizing 65 parts by mass of butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 15 parts by mass of 2-hydroxyethyl acrylate (2HEA) is added with all hydroxyl groups of the acrylic polymer. 2-Methacryloyloxyethyl isocyanate (MOI) was reacted so as to be added to hydroxyl groups of 80 mol % of them to obtain an energy ray-curable acrylic resin (Mw: 500,000). To 100 parts by mass of this energy ray-curable acrylic resin, 6 parts by weight of polyfunctional urethane acrylate (trade name: Shikou UT-4332, manufactured by Mitsubishi Chemical Corporation), which is an energy ray-curable compound, an isocyanate-based cross-linking agent (Tosoh Co., Ltd., trade name: Coronate L) was added to 0.375 parts by weight based on the solid content, and 1 part by weight of a photopolymerization initiator made of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide was added, and the solvent was to prepare a coating solution of the pressure-sensitive adhesive layer composition.

(Formation of adhesive layer)
Release sheet (manufactured by Lintec, trade name “SP-PET381031”, polyethylene terephthalate (PET) film subjected to silicone release treatment, thickness: 38 μm). The solution was applied and dried to prepare a release sheet with an adhesive layer having an adhesive layer with a thickness of 20 μm.

(2) Preparation of substrate with antistatic layer As a substrate, a 50 μm thick primer-attached PET film (manufactured by Toyobo Co., Ltd., product name “PET50A- 4100”) were prepared. The Young's modulus of this PET film was 2500 MPa.

A polythiophene-based conductive polymer (Denatron P-400MP, manufactured by Nagase Chemtech Co., Ltd.) is applied to the surface of the PET film opposite to the surface on which the first primer layer is provided, and dried to obtain a thickness. A 120 nm antistatic layer was formed on the PET film.

(3) Buffer layer (synthesis of urethane acrylate oligomer (UA-1))
A terminal isocyanate urethane prepolymer obtained by reacting a polyester diol and isophorone diisocyanate is reacted with 2-hydroxyethyl acrylate to obtain a bifunctional urethane acrylate oligomer (UA-1) having a weight average molecular weight (Mw) of 5000. got

(Preparation of composition for forming buffer layer)
As the energy beam polymerizable compound, 40 parts by mass of the urethane acrylate oligomer (UA-1) synthesized above, 40 parts by mass of isobornyl acrylate (IBXA), and 20 parts by mass of phenylhydroxypropyl acrylate (HPPA) are blended, Furthermore, 2.0 parts by mass of 1-hydroxycyclohexylphenyl ketone (manufactured by IGM Resins, product name "OMNIRAD184") as a photopolymerization initiator and 0.2 parts by mass of a phthalocyanine pigment are blended to form a buffer layer-forming composition. was prepared.

(Formation of buffer layer)
Release sheet (manufactured by Lintec, trade name “SP-PET381031”, polyethylene terephthalate (PET) film subjected to silicone release treatment, thickness: 38 μm). A material was applied to form a coating film. Then, the coating film was irradiated with ultraviolet rays to semi-harden the coating film, thereby forming a buffer layer forming film having a thickness of 50 μm.

The above ultraviolet irradiation is performed using a belt conveyor type ultraviolet irradiation device (product name "ECS-401GX", manufactured by Eyegraphics) and a high-pressure mercury lamp (H04-L41 manufactured by Eyegraphics: H04-L41). The measurement was performed under irradiation conditions of a height of 150 mm, a lamp output of 3 kW (converted output of 120 mW/cm), an illuminance of 120 mW/cm ² at a light wavelength of 365 nm, and a dose of 100 mJ/cm ² .

The surface of the formed buffer layer-forming film and the first primer layer of the base material with an antistatic layer are laminated together, and ultraviolet rays are again irradiated from the release sheet side on the buffer layer-forming film to remove the buffer layer-forming film. It was completely cured to form a buffer layer with a thickness of 50 μm.

The above ultraviolet irradiation uses the above-described ultraviolet irradiation device and high-pressure mercury lamp, with a lamp height of 150 mm, a lamp output of 3 kW (converted output of 120 mW/cm), an illuminance of 160 mW/cm ² at a light wavelength of 365 nm, and an irradiation amount of 500 mJ. / cm ² irradiation conditions.

(4) Preparation of protective sheet for semiconductor processing By laminating the adhesive layer of the release sheet with adhesive layer on the antistatic layer, the antistatic layer and the adhesive layer are formed on one main surface of the substrate. A protective sheet for semiconductor processing was produced, which was formed in order and had a buffer layer formed on the other main surface of the base material.

(Example 2)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that the thickness of the antistatic layer was 150 nm and the thickness of the adhesive layer was 5 μm.

(Example 3)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that the thickness of the antistatic layer was 80 nm and the thickness of the adhesive layer was 200 μm.

(Example 4)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that the following adhesive layer composition was used to form the adhesive layer.

(Preparation of composition for adhesive layer)
An acrylic polymer (Mw: 800,000) was obtained by copolymerizing 89 parts by mass of n-butyl acrylate (BA), 8 parts by mass of methyl methacrylate (MMA), and 3 parts by mass of 2-hydroxyethyl acrylate (2HEA). .

For 100 parts by mass of the acrylic polymer described above, 1 part by mass (solid content) of a tolylene diisocyanate-based cross-linking agent (manufactured by Tosoh Corporation, product name "Coronate L") as a cross-linking agent, an epoxy-based cross-linking agent (1,3- Bis(N,N-diglycidylaminomethyl)cyclohexane) 2 parts by mass (solid content) and an energy ray-curable compound (manufactured by Mitsubishi Chemical Corporation, product name “Shikou UV-3210EA”) 45 parts by mass (solid content) and a photopolymerization initiator (manufactured by IGM Resins, product name "OMNIRAD 184") 1 part by mass (solid content) were mixed and diluted with a solvent to obtain a coating liquid for a pressure-sensitive adhesive layer composition.　

(Example 5)
A protective sheet for semiconductor processing was prepared in the same manner as in Example 1, except that a pressure-sensitive adhesive layer was formed using the following pressure-sensitive adhesive layer composition, and the thickness of the antistatic layer was 25 nm and the thickness of the pressure-sensitive adhesive layer was 5 μm. got

(Preparation of composition for adhesive layer)
An acrylic polymer obtained by copolymerizing 75 parts by mass of butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 5 parts by mass of 2-hydroxyethyl acrylate (2HEA) is added with all hydroxyl groups of the acrylic polymer. 2-Methacryloyloxyethyl isocyanate (MOI) was reacted so as to be added to hydroxyl groups of 90 mol % of them to obtain an energy ray-curable acrylic resin (Mw: 500,000).

To 100 parts by mass of this energy ray-curable acrylic resin, 0.375 parts by mass of an isocyanate cross-linking agent (manufactured by Tosoh Corporation, trade name: Coronate L) based on solid content, bis(2,4,6-trimethyl 1 part by weight of a photopolymerization initiator consisting of benzoyl)phenylphosphine oxide was added, and the mixture was diluted with a solvent to prepare a coating liquid for a pressure-sensitive adhesive layer composition.

(Example 6)
Low-density polyethylene (LDPE; Sumikasen L705 manufactured by Sumitomo Chemical Co., Ltd.) was extruded using a small T-die extruder to obtain an LDPE film with a thickness of 100 μm. One side of the same LDPE film was subjected to corona treatment, and the corona-treated surface was coated with a polythiophene-based conductive polymer (Denatron P-400MP, manufactured by Nagase Chemtech Co., Ltd.) and dried to form an antistatic layer with a thickness of 120 nm. was formed on an LDPE film to obtain a substrate with an antistatic layer.

A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that the adhesive layer of the release sheet with an adhesive layer was adhered onto the antistatic layer of this base material.

(Comparative example 1)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that no antistatic layer was provided.

(Comparative example 2)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that a pressure-sensitive adhesive layer was formed using the following pressure-sensitive adhesive layer composition and the thickness of the antistatic layer was changed to 50 nm.

(Preparation of composition for adhesive layer)
An acrylic polymer obtained by copolymerizing 65 parts by mass of butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 15 parts by mass of 2-hydroxyethyl acrylate (2HEA) is added with all hydroxyl groups of the acrylic polymer. 2-Methacryloyloxyethyl isocyanate (MOI) was reacted so as to be added to hydroxyl groups of 90 mol % of them to obtain an energy ray-curable acrylic resin (Mw: 500,000).

To 100 parts by mass of this energy ray-curable acrylic resin, 20 parts by weight of polyfunctional urethane acrylate (trade name: Shikou UT-4332, manufactured by Mitsubishi Chemical Corporation), which is an energy ray-curable compound, an isocyanate-based cross-linking agent (Tosoh Co., Ltd., trade name: Coronate L) was added to 0.375 parts by weight based on the solid content, and 1 part by weight of a photopolymerization initiator made of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide was added, and the solvent was to prepare a coating solution of the pressure-sensitive adhesive layer composition.

(Comparative Example 3)
A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that the following adhesive layer composition was used to form the adhesive layer.

(Preparation of composition for adhesive layer)
An acrylic polymer obtained by copolymerizing 75 parts by mass of butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 5 parts by mass of 2-hydroxyethyl acrylate (2HEA) is added with all hydroxyl groups of the acrylic polymer. 2-Methacryloyloxyethyl isocyanate (MOI) was reacted so as to be added to hydroxyl groups of 50 mol % of them to obtain an energy ray-curable acrylic resin (Mw: 500,000).

The above measurements and evaluations were performed on the obtained samples (Examples 1 to 6 and Comparative Examples 1 to 3). The adhesive force ratio was calculated from the 90° peeling adhesive force of the adhesive layer before and after energy ray curing. Table 1 shows the results.

From Table 1, when the 90° peeling adhesive strength of the adhesive layer of the protective sheet for semiconductor processing is within the range described above and the protective sheet for semiconductor processing contains an antistatic layer, It was confirmed that the electrification voltage associated with peeling of the protective sheet was low, and the rate of occurrence of cracks due to chip shift was low.

DESCRIPTION OF SYMBOLS 1... Protection sheet for semiconductor processing 10... Base material 20... Antistatic layer 30... Adhesive layer 40... Buffer layer

Claims

having a substrate, an antistatic layer, and an energy ray-curable adhesive layer,
When the adhesive layer after energy beam curing was peeled off from the silicon wafer at a peeling speed of 600 mm/min so that the angle formed by the adhesive layer and the silicon wafer was 90°, the adhesive strength was 0.035 N/25 mm. A protective sheet for semiconductor processing which is not less than 0.15 N/25 mm.
The adhesive force when the adhesive layer before energy ray curing is peeled off from the silicon wafer at a peeling speed of 600 mm / min so that the angle formed by the adhesive layer and the silicon wafer is 90 °. The adhesive force ratio when the adhesive layer after curing is peeled off from the silicon wafer at a peeling speed of 600 mm/min so that the angle formed by the adhesive layer and the silicon wafer is 90° is 4% or less. The protective sheet for semiconductor processing according to claim 1.
3. The protective sheet for semiconductor processing according to claim 1, wherein the surface resistivity of the pressure-sensitive adhesive layer after curing with energy rays is 5.1×10 12 Ω/cm 2 or more and 1.0×10 15 Ω/cm 2 or less. .
The protective sheet for semiconductor processing according to any one of claims 1 to 3, further comprising a buffer layer.
a step of attaching the protective sheet for semiconductor processing according to any one of claims 1 to 4 to the surface of a wafer;
a step of grinding the wafer having the protective sheet for semiconductor processing attached to the surface from the back side;
and peeling off the protective sheet for semiconductor processing from the back-grinded wafer.