KR20240031951A - Method of manufacturing protective sheets for semiconductor processing and semiconductor devices - Google Patents

Abstract

(Problem) To provide a protective sheet for semiconductor processing in which electrification generated during wafer processing is sufficiently suppressed even when wafers are processed thinly using DBG or the like, and chip cracks are suppressed during peeling, and To provide a method of manufacturing a semiconductor device using a protective sheet for semiconductor processing.
(Solution) A protective sheet for semiconductor processing comprising a base material, an antistatic layer, and an energy ray-curable adhesive layer, wherein the surface resistivity of the adhesive layer after energy ray curing is 5.1 × 10 ¹² Ω/cm2 or more and 1.0 × 10 ¹⁵ Ω/cm2 or less. am.

Description

Method of manufacturing protective sheets for semiconductor processing and semiconductor devices

The present invention relates to a protective sheet for semiconductor processing and a method of manufacturing a semiconductor device. In particular, it relates to a protective sheet for semiconductor processing that is preferably used in a method of grinding the back side of a wafer and dividing the wafer into pieces due to the stress, etc., and a method of manufacturing a semiconductor device using the protective sheet for semiconductor processing.

As various electronic devices become smaller and more functional, the semiconductor chips mounted on them are also required to be smaller and thinner. In order to make chips thinner, it is common to grind the back side of a semiconductor wafer to adjust the thickness. Additionally, in order to obtain thinner chips, a groove of a predetermined depth is formed from the front surface of the wafer with a dicing blade, then grinding is performed from the back side of the wafer, and the grinding surface reaches the groove or the vicinity of the groove to separate the wafer into pieces. Therefore, there are cases where a method called sun dicing (DBG: Dicing Before Grinding) is used to obtain chips. In DBG, the backside grinding of the wafer and the separation of the wafer into pieces can be performed simultaneously, so thin chips can be manufactured efficiently.

Conventionally, when grinding the back side of a semiconductor wafer or manufacturing chips using DBG, an adhesive tape called a back grinding sheet is attached to the wafer surface to protect the circuitry on the wafer surface and to maintain the semiconductor wafer and semiconductor chips. It is common to do so.

As an example of a backgrinding sheet, Patent Document 1 and Patent Document 2 disclose an adhesive tape including a base material with a high Young's modulus, a buffer layer provided on one side of the base material, and an adhesive layer provided on the other side. .

In recent years, as a modification of DBG, a method has been proposed in which a modified region is provided inside the wafer with a laser and the wafer is separated into individual pieces using stress during grinding of the back side of the wafer. Hereinafter, this method may be referred to as LDBG (Laser Dicing Before Grinding). In LDBG, the wafer is cut in the crystal direction starting from the modified region, so the occurrence of chipping can be reduced compared to DBG using a dicing blade. As a result, it can contribute to further thinning of the chip. In addition, compared to DBG, which forms a groove of a predetermined depth on the wafer surface with a dicing blade, there is no area where the wafer is shaved off with a dicing blade, that is, the kerf width is extremely small, resulting in excellent chip yield. do.

International Publication No. 2015/156389 Japanese Patent Publication No. 2015-183008

It is known that electrification occurs during wafer processing (for example, dicing, back grinding, cleaning, peeling of back grinding tape, etc.). When electrification occurs, cut dust generated during grinding and microscopic foreign substances present in the environment tend to attach to the wafer or individualized chips.

For example, if cut dust or foreign matter adheres to the wafer during back grinding, the pressure during back grinding may focus on the attached foreign matter, and the wafer may be damaged starting from the foreign matter. In particular, when DBG is performed for the purpose of grinding a wafer thin, damage to the wafer is likely to occur due to a slight concentration of pressure. Therefore, it is necessary to suppress charging that occurs during wafer processing.

In addition, the back grinding tape is required to adhere strongly to the surface of the wafer when grinding the back side of the wafer to sufficiently protect the circuits, etc., and to be easily peeled off from the wafer when peeling the back grinding tape from the wafer after grinding the back side of the wafer. . Therefore, the adhesive layer of the backgrinding tape attached to the wafer is usually composed of an energy ray-curable adhesive. At the time of peeling, the adhesive layer is cured by irradiating energy rays to reduce the adhesive force, thereby achieving both adhesion during back grinding and peelability after back grinding.

However, if curing of the adhesive layer by energy ray irradiation is insufficient, the adhesive may remain on the wafer during peeling, or the individual chips may come into contact with each other due to poor peeling, resulting in chip defects or damage (hereinafter referred to as chip cracks). There are cases where this occurs. In particular, in LDBG, since the kerf width of the chip is small, chip cracks may occur even if there is a slight peeling defect.

When the backgrinding tapes described in Patent Document 1 and Patent Document 2 are used in DBG, especially LDBG, the suppression of electrification that occurs during wafer processing and the suppression of cracks in chips when the backgrinding tape is peeled are insufficient. There was a problem.

The present invention has been made in consideration of this actual situation, and even when the wafer is processed thinly by DBG or the like, the charging generated during wafer processing is sufficiently suppressed, and the occurrence of chip cracks during peeling is suppressed. The object is to provide a protective sheet and a method of manufacturing a semiconductor device using the protective sheet for semiconductor processing.

The aspects of the present invention are as follows.

[1] It has a base material, an antistatic layer, and an energy ray-curable adhesive layer,

This is a protective sheet for semiconductor processing in which the surface resistivity of the adhesive layer after energy ray curing is 5.1 × 10 ¹² Ω/cm2 or more and 1.0 × 10 ¹⁵ Ω/cm2 or less.

[2] If the surface resistivity is SR [Ω/㎠] and the thickness of ^the adhesive layer is T [㎛], SR/T ^{2 is 8.0} It is a protective sheet for semiconductor processing according to [1], which has a thickness of ㎠㎛ ² or less.

[3] When the adhesive layer after energy ray curing is peeled from the silicon wafer at a peeling speed of 600 mm/min so that the angle formed between the adhesive layer and the silicon wafer is 90°, the adhesive force is less than 0.15 N/25 mm [1] Or the protective sheet for semiconductor processing described in [2].

[4] Regarding the adhesive strength when the adhesive layer before energy ray curing is peeled from a silicon wafer at a peeling speed of 600 mm/min so that the angle between the adhesive layer and the silicon wafer is 90°, the adhesive layer after energy ray curing is peeled off from the silicon wafer. The protective sheet for semiconductor processing according to any one of [1] to [3], wherein the adhesive strength ratio when peeled at a peeling speed of 600 mm/min so that the angle formed between the adhesive layer and the silicon wafer is 90° is 4% or less.

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

[6] In the process of dividing the wafer into chips by grinding the back side of the wafer on which grooves are formed on the surface or modified regions on the inside, the method described in any of [1] to [5] is used by attaching to the surface of the wafer. This is a protective sheet for semiconductor processing.

[7] A process of attaching the protective sheet for semiconductor processing according to any one of [1] to [6] to the surface of a wafer;

A process of forming a groove from the front side of the wafer, or a process of forming a modified area inside the wafer from the front or back side of the wafer;

A process of grinding a wafer on which a protective sheet for semiconductor processing is attached to the surface and on which grooves or modified areas are formed, from the back side, and dividing the wafer into a plurality of chips using the grooves or modified areas as a starting point;

A method for manufacturing a semiconductor device including a step of peeling a protective sheet for semiconductor processing from a separated chip.

According to the present invention, even when the wafer is processed thinly by DBG or the like, the charging generated during wafer processing is sufficiently suppressed, and the occurrence of chip cracks during peeling is suppressed. To provide a protective sheet for semiconductor processing, And a method of manufacturing a semiconductor device using the protective sheet for semiconductor processing can be provided.

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

Hereinafter, the present invention will be described in detail based on specific embodiments and using drawings. First, the main terms used in this specification will be explained.

Separation of the wafer refers to dividing the wafer into individual circuits to obtain chips.

The “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 a groove of a predetermined depth on the front side of a wafer, then grinding the wafer from the back side, and breaking the wafer into pieces by grinding. The groove formed on the surface side of the wafer is formed by a method such as blade dicing, laser dicing, or plasma dicing.

Additionally, LDBG (Laser Dicing Before Grinding) is a modified example of DBG and refers to a method of providing a modified area inside the wafer with a laser and dividing the wafer into pieces using stress during grinding the back side of the wafer.

“Chip group” refers to a plurality of chips held on the protective sheet for semiconductor processing according to the present embodiment after the wafer is separated into individual pieces. These chips, as a whole, have a shape similar to that of the wafer.

“(Meth)acrylate” is used as a word representing both “acrylate” and “methacrylate”, and the same applies to other similar terms.

“Energy rays” refer to ultraviolet rays, electron beams, etc., and are preferably ultraviolet rays.

Unless otherwise specified, “weight average molecular weight” is a polystyrene conversion value measured by gel permeation chromatography (GPC) method. Measurement by this method is, for example, performed using a high-speed GPC device “HLC-8120GPC” manufactured by TOSOH CORPORATION and a high-speed column “TSK guard column H _XL -H”, “TSK Gel GMH _XL ”, and “TSK Gel G2000 H _XL ” 」(all manufactured by TOSOH CORPORATION) is connected in this order, and the detector is used as a differential refractometer under the conditions of column temperature: 40°C, liquid feeding rate: 1.0 mL/min.

(1. Protection sheet for semiconductor processing)

As shown in FIG. 1A, the protective sheet 1 for semiconductor processing according to the present embodiment has an antistatic layer 20 and an adhesive layer 30 on one main surface 10a of the substrate 10. It has an organized structure. From the viewpoint of antistatic function, it is preferable that the antistatic layer is close to the peeling interface of the protective sheet for semiconductor processing, that is, the surface 30a of the adhesive layer. Therefore, as shown in FIG. 1A, the antistatic layer 20 is preferably provided on one main surface 10a of the base material 10 rather than on the other main surface 10b of the base material 10. do. When using the protective sheet 1 for semiconductor processing, the surface 30a of the adhesive layer 30 is temporarily attached to the adherend, and is then peeled off from the adherend.

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

Another example of a protective sheet for semiconductor processing is a protective sheet for semiconductor processing in which an antistatic layer 20, an adhesive layer 30, and a buffer layer 40 are provided on one main surface 10a of the substrate 10. The antistatic layer 20 and the buffer layer 40 are disposed between the substrate 10 and the adhesive layer 30. From the viewpoint of ease of manufacturing the protective sheet for semiconductor processing, it is preferable that the antistatic layer 20, the buffer layer 40, and the adhesive layer 30 are arranged in this order on the substrate 10. Meanwhile, as described above, from the viewpoint of antistatic function, it is preferable that the buffer layer 40, antistatic layer 20, and adhesive layer 30 are arranged in this order on the substrate 10.

In addition, as shown in FIG. 1B, the antistatic layer 20 and the adhesive layer 30 are provided in this order on one main surface 10a of the base material 10, and the other main surface 10b of the base material 10. A protective sheet for semiconductor processing having a structure provided with a buffer layer 40 thereon is exemplified.

By having a buffer layer, DBG or LDBG is more preferable as a protective sheet for semiconductor processing used when grinding the back side of a wafer.

Below, the protective sheet for semiconductor processing shown in FIG. 1A is explained.

As shown in FIG. 2, the surface 30a of the adhesive layer is attached to the circuit surface of the wafer 100 as the adherend, that is, the surface 100a of the wafer 100, thereby providing protection for semiconductor processing according to the present embodiment. The sheet 1 protects the surface 100a of the wafer 100 when grinding the back surface 100b of the wafer 100.

As described above, during wafer processing including backside grinding, charging occurs in the wafer or chip group. If this charging is not alleviated, there is a risk that foreign substances, etc. may adhere to the wafer or the like due to the charging, resulting in damage to the wafer or the like. Therefore, the protective sheet for semiconductor processing according to the present embodiment includes an antistatic layer, and sets the surface resistivity of the adhesive layer to a predetermined range to lower the electrostatic voltage and alleviate static electricity.

Additionally, the present inventor discovered that the surface resistivity of the adhesive layer reflects the degree of curing of the adhesive layer after irradiation with energy rays. As the amount of energy-ray polymerizable carbon-carbon double bonds in the adhesive layer before curing increases, curing of the adhesive layer tends to proceed, and the number of cross-linking points in the adhesive layer after curing increases, making it difficult for charges to move, and the surface resistivity tends to increase. . On the other hand, as the amount of energy-ray polymerizable carbon-carbon double bonds in the pressure-sensitive adhesive layer before curing decreases, the surface resistivity tends to decrease, but since the starting point of the polymerization reaction decreases, curing of the pressure-sensitive adhesive layer tends to be insufficient. As a result, when peeling a protective sheet for semiconductor processing from a wafer, etc., peeling defects in the adhesive layer tend to occur, resulting in damage to the wafer, etc., cracks, etc.

Therefore, in this embodiment, for example, by controlling the amount of energy ray polymerizable carbon-carbon double bonds in the adhesive layer before curing, the composition of the adhesive layer is set to a composition that is sufficiently cured by energy ray irradiation, and the surface of the adhesive layer is By controlling the resistivity within a predetermined range, electrification is alleviated and damage to wafers, cracks, etc. caused by poor peeling of the adhesive layer is suppressed.

Hereinafter, the components of the protective sheet for semiconductor processing will be described in detail.

(2. Description)

The base material is not limited as long as it is made of a material that can support the wafer before grinding the back side of the wafer and can hold the wafer, etc. after grinding the back side of the wafer. For example, various resin films used as a base material for backgrinding tapes are exemplified as the base material. The base material may be comprised of a single-layer film made of one resin film, or may be comprised of a multi-layer film in which a plurality of resin films are laminated.

(2.1 Physical properties of substrate)

In this embodiment, it is preferable that the base material has high rigidity. As the rigidity of the substrate is high, vibration during back side grinding can be suppressed, and as a result, the support and holding performance of the wafer is improved, and damage and cracks of the wafer are reduced. Additionally, it contributes to reducing the stress when peeling the protective sheet for semiconductor processing from the wafer, thereby reducing damage or cracks to the wafer that occur during peeling. Additionally, workability when attaching the protective sheet for semiconductor processing to the wafer also improves. Specifically, the Young's modulus of the substrate at 23°C is preferably 1000 MPa or more, and more preferably 1800 MPa or more. The upper limit of Young's modulus is not particularly limited, but is approximately 30000 MPa. The Young's modulus of the substrate can be controlled by selection of the resin composition, addition of a plasticizer, stretching conditions during production of the resin film, etc.

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

(2.2 Base material)

As the material of the base material, it is desirable to select a material so that the Young's modulus of the base material is within the above range. In this embodiment, for example, polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and wholly aromatic polyester, polyimide, polyamide, polycarbonate, polyacetal, modified polyphenylene oxide, Examples include polyphenylene sulfide, polysulfone, polyether ketone, and biaxially stretched polypropylene. Among these, at least one selected from polyester, polyamide, polyimide, and biaxially oriented polypropylene is preferable, polyester is more preferable, and polyethylene terephthalate is still more preferable.

Additionally, the base material may contain a plasticizer, a lubricant, an infrared absorber, an ultraviolet ray absorber, a filler, a colorant, an antistatic agent, an antioxidant, a catalyst, etc., as long as the effect of the present invention is not impaired. Additionally, the substrate may be transparent or opaque, and may be colored or vapor-deposited as desired.

Additionally, at least one main surface of the substrate may be subjected to adhesion treatment, such as corona treatment, in order to improve adhesion with other layers. Additionally, the base material may have a primer layer on at least one side of the main surface.

The primer layer forming composition for forming the primer layer is not particularly limited, but examples include compositions containing polyester resin, urethane resin, polyester urethane resin, acrylic resin, etc. The composition for forming a primer layer may contain a crosslinking agent, photopolymerization initiator, antioxidant, softener (plasticizer), filler, rust preventive, pigment, dye, etc., if necessary.

The thickness of the primer layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm. Since the material of the primer layer is soft, the effect on the Young's modulus is small, and the Young's modulus of the base material is substantially the same as the Young's modulus of the resin film even when it has a primer layer.

(3. Adhesive layer)

The adhesive layer is affixed 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 adhesive layer is energy ray curable. The adhesive layer may be composed of one layer (single layer) or may be composed of two or more layers. When the pressure-sensitive adhesive layer has multiple layers, these multiple layers may be the same or different from each other, and the combination of the layers constituting these multiple layers is not particularly limited.

The thickness (T: μm) of the adhesive layer is not particularly limited, but is preferably 3 μm or more and 200 μm or less, and more preferably 5 μm or more and 100 μm or less. When the thickness of the adhesive layer is within the above range, cracking of the wafer can be suppressed.

In this embodiment, it is more preferable that the thickness T of the adhesive layer is within a range that satisfies the relationship with the surface resistivity of the adhesive layer described later.

In addition, the thickness of the adhesive layer means the thickness of the entire adhesive layer. For example, the thickness of an adhesive layer comprised of multiple layers means the total thickness of all layers constituting the adhesive layer.

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

(3.1 Surface resistivity)

In this embodiment, the surface resistivity (SR) of the adhesive layer after energy ray curing is 5.1 × 10 ¹² Ω/cm2 or more and 1.0 × 10 ¹⁵ Ω/cm2 or less. In addition, 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).

When the surface resistivity (SR: Ω/cm2) is within the above range, static electricity can easily escape from the protective sheet for semiconductor processing, and electrification of the wafer or group of chips can be suppressed during processing of the wafer to which the protective sheet for semiconductor processing is attached. You can. Therefore, in the process of attaching the protective sheet for semiconductor processing to the surface of the wafer, the process of grinding the back side of the wafer, the process of peeling off the protective sheet for semiconductor processing, and the process of transporting the wafer or chip group after peeling the protective sheet for semiconductor processing, etc., the wafer, etc. It can suppress the adhesion of foreign substances, etc. As a result, damage and cracking of the wafer, etc., caused by adhesion of foreign substances, etc., are suppressed.

In addition, when the surface resistivity is within the above range, even if the protective sheet for semiconductor processing is peeled off, movement of the separated chips is suppressed and contact between the chips is reduced, so chip cracking can be suppressed. As described above, the surface resistivity can be controlled to some extent by the amount of energy ray polymerizable carbon-carbon double bonds in the adhesive layer before curing, and as curing of the adhesive layer progresses, the surface resistivity tends to increase. Therefore, when the surface resistivity is smaller than the above range, curing of the adhesive layer is insufficient. As a result, when peeling the protective sheet for semiconductor processing, it is not peeled off from the wafer or chip properly, and a part of the adhesive layer may remain attached to the wafer or chip (remaining glue), or may cause cracks in the chip. .

The surface resistivity is preferably 9.5 × 10 ¹⁴ Ω/cm2 or less, and more preferably 9.0 × 10 ¹⁴ Ω/cm2 or less. On the other hand, the surface resistivity is preferably 5.2 × 10 ¹² Ω/cm2 or more, and more preferably 5.5 × 10 ¹² Ω/cm2 or more.

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

(3.2 Relationship between surface resistivity and thickness of adhesive layer)

In this embodiment, if the surface resistivity of the adhesive layer is SR (Ω/cm2) and the thickness of the adhesive layer is T (㎛), SR/T ² is 8.0 × 10 ⁹ Ω / cm ² or more 5.0 × 10 ¹³ It is preferable that Ω/cm2㎛ ² or less. Since the antistatic properties of the protective sheet for semiconductor processing are influenced not only by the surface resistivity but also by the thickness of the adhesive layer, when SR/T ² is within the above range, it becomes easy for static electricity to escape from the protective sheet for semiconductor processing, providing protection for semiconductor processing. When processing a wafer to which a sheet is attached, charging of the wafer or chip group can be suppressed. Furthermore, even if the protective sheet for semiconductor processing is peeled off, cracking of the chips can be suppressed because movement of the separated chips is suppressed and contact between the chips is reduced.

SR/T ² is preferably 4.5 × 10 ¹³ Ω/cm2㎛ ² or less, and more preferably 4.0 × 10 ¹³ Ω/cm2 ㎛ ² or less. ^On the other hand, ^{SR /T 2 is} preferably ^9.0

(3.3 90° peel adhesion of adhesive layer after energy ray curing)

In this embodiment, the adhesive force when the adhesive layer after energy radiation curing is peeled from the silicon wafer so that the angle formed between the adhesive layer and the silicon wafer is 90° (hereinafter also referred to as the 90° peeling adhesive force of the adhesive layer after energy radiation curing) It is preferable that this is less than 0.15N/25mm. When the 90° peel adhesive strength of the pressure-sensitive adhesive layer after energy ray curing is within the above range, the adhesive strength is sufficiently reduced, making it easy to peel the pressure-sensitive adhesive layer from the chip group after back-side grinding. Therefore, glue residue on wafers, etc. and cracks in chips can be reduced.

The 90° peel adhesive strength of the adhesive layer after energy ray curing is more preferably 0.14 N/25 mm or less, and further preferably 0.13 N/25 mm or less. On the other hand, if the 90° peel adhesive force of the adhesive layer after energy ray curing is too small, the tape may peel at an unexpected timing before the predetermined tape peeling process, resulting in a process error. Therefore, it is preferable that the 90° peel adhesive strength of the adhesive layer after energy ray curing is 0.035 N/25 mm or more.

In this embodiment, the 90° peel adhesive strength of the adhesive layer after energy ray curing is in accordance with JIS Z 0237, after attaching the adhesive layer to a silicon wafer and curing the adhesive layer with an energy ray, the peeling rate is 600 mm/min. The adhesive force is measured when the cured adhesive layer is peeled from the silicon wafer at an angle of 90° under the following conditions. Specific measurement conditions are described later in the examples.

Additionally, the peeling speed of 600 mm/min tends to be faster than the peeling speed during normal adhesive force measurement. This condition assumes the peeling speed when peeling the adhesive layer from a wafer ground by DBG, LDBG, etc. Generally, as the peeling speed increases, the adhesive strength tends to increase.

(3.4 90° peel adhesion ratio of adhesive layer before and after energy ray curing)

In this embodiment, the ratio of the 90° peel 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 from the silicon wafer so that the angle formed between the adhesive layer and the silicon wafer is 90° (hereinafter also referred to as the 90° peel adhesive strength of the adhesive layer before energy beam curing), It is preferable that the ratio of the 90° peel adhesive strength of the adhesive layer after energy ray curing (hereinafter also referred to as adhesive strength ratio) is 4% or less.

When the adhesive force ratio is within the above range, during back grinding, the adhesive layer sufficiently adsorbs to the surface of the wafer to protect the circuit, and after back grinding, peeling of the adhesive layer from the wafer, etc. becomes easy, preventing chip cracks. can be suppressed.

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

The 90° peel adhesion of the adhesive layer before energy ray curing may be measured in the same manner as the measurement method for the 90° peel adhesion of the adhesive layer after energy ray curing, except that the adhesion of the adhesive layer before energy ray curing is measured. Specific measurement conditions are described later in the examples.

(3.5 Composition of adhesive layer)

The composition of the adhesive layer is not particularly limited as long as the adhesive layer has adhesiveness sufficient to protect the circuit surface of the wafer and has the above surface resistivity. In this embodiment, the adhesive layer is composed of a composition (composition for adhesive layer) containing, as an adhesive component (adhesive resin) capable of developing adhesiveness, for example, an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, etc. It is desirable to be

Additionally, from the viewpoint of being easy to achieve the above-described adhesive strength and adhesive strength ratio after energy ray curing, the composition for the adhesive layer contains an energy ray curable adhesive.

(3.6 Composition for adhesive layer)

As described above, the pressure-sensitive adhesive layer is energy-ray curable, so it is formed from a composition (composition for pressure-sensitive adhesive layer) having energy-ray curability. Below, the composition for the adhesive layer is explained.

The composition for the adhesive layer may have energy ray curing properties by blending an energy ray curing compound separately from the adhesive resin, but it is preferable that the adhesive resin itself has energy ray curing properties. When the adhesive resin itself has energy ray curability, an energy ray polymerizable group is introduced into the adhesive resin, but it is preferable that the energy ray polymerizable group is introduced into the main chain or side chain of the adhesive resin.

Additionally, 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 is an oligomer with a weight average molecular weight (Mw) of less than 10000, and examples include urethane (meth)acrylate.

In this embodiment, from the viewpoint of controlling the amount of energy ray polymerizable carbon-carbon double bonds, the amount is preferably 0.1 to 300 parts by mass, more preferably 0.5 to 0.5 parts by mass, per 100 parts by mass of the adhesive resin without energy ray polymerization. It is 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 composition for an adhesive layer is an energy-ray-curable acrylic polymer (hereinafter also referred to as “acrylic polymer (A)”) will be described in more detail.

(3.6.1 Acrylic polymer (A))

The acrylic polymer (A) is an acrylic polymer into which an energy ray polymerizable group is introduced and also 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 a polymerizable acrylic copolymer (A0) having a structural unit derived from alkyl (meth)acrylate (a1) and a structural unit derived from a functional group-containing monomer (a2), and has an energy ray polymerizable group. It is preferable that it is a reactant obtained by reacting compound (Xa).

As alkyl (meth)acrylate (a1), alkyl (meth)acrylate whose alkyl group has 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. Rate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, mili Steel (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, etc. can be mentioned.

Among these, it is preferable that the alkyl (meth)acrylate (a1) is an alkyl (meth)acrylate in which the alkyl group has 4 to 8 carbon atoms. Specifically, 2-ethylhexyl (meth)acrylate and n-butyl (meth)acrylate are preferable, and n-butyl (meth)acrylate is more preferable. Moreover, they may be used individually or in combination of two or more types.

The content of structural units derived from alkyl (meth)acrylate (a1) in the acrylic copolymer (A0) is determined from the viewpoint of improving the adhesive strength of the formed adhesive layer, the total structural units of the acrylic copolymer (A0) ( With respect to 100 mass%), it is preferably 40 to 98 mass%, more preferably 45 to 95 mass%, and even more preferably 50 to 90 mass%.

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

The functional group-containing monomer (a2) is a monomer having a functional group such as a hydroxy group, carboxyl group, epoxy group, amino group, cyano group, nitrogen atom-containing ring group, and alkoxysilyl group. Among the above-mentioned functional group-containing monomers (a2), at least one selected from the group consisting of hydroxy group-containing monomers, carboxyl group-containing monomers, and epoxy group-containing monomers is preferable.

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

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

Examples of the epoxy-containing monomer include epoxy group-containing (meth)acrylic acid ester and non-acrylic epoxy group-containing monomer. Examples of epoxy group-containing (meth)acrylic acid esters include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, (3,4-epoxycyclohexyl)methyl (meth)acrylate, 3-epoxycyclo-2-hydroxypropyl (meth)acrylate, etc. can be mentioned. In addition, examples of non-acrylic epoxy group-containing monomers include glycidyl crotonate and allyl glycidyl ether.

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

As the functional group-containing monomer (a2), among the above, hydroxy group-containing monomers are more preferable, and among these, hydroxyalkyl (meth)acrylate is more preferable, and 2-hydroxyethyl (meth)acrylate is more preferable. do.

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

The content of the structural unit derived from the functional group-containing monomer (a2) in the acrylic copolymer (A0) is preferably 1 to 35% by mass, based on the total structural units (100% by mass) of the acrylic copolymer (A0). , more preferably 3 to 32 mass%, further preferably 6 to 30 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, since the adhesive layer can be appropriately cured by irradiation of energy rays, it becomes possible to lower the adhesive force after irradiation of energy rays. Moreover, if the content is 30% by mass or less, sufficient pot life can be ensured when applying the solution of the composition for an adhesive layer to form an adhesive layer.

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

Other monomers (a3) include, for example, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. ) Acrylate, (meth)acrylate having a cyclic structure such as dicyclopentenyloxyethyl (meth)acrylate, vinyl acetate, styrene, etc. Other monomers (a3) may be used individually or in combination of two or more types.

The content of structural units derived from other monomers (a3) in the acrylic copolymer (A0) is preferably 0 to 30% by mass, based on the total structural units (100% by mass) of the acrylic copolymer (A0). More preferably, it is 0 to 10 mass%, and even more preferably, it is 0 to 5 mass%.

The polymerizable compound (Xa) has an energy ray polymerizable group and a substituent that can react with a functional group in the structural unit derived from component (a2) of the acrylic copolymer (A0) (hereinafter also simply referred to as a “reactive substituent”). It is a compound.

The energy ray polymerizable group may be a group containing an energy ray polymerizable carbon-carbon double bond. For example, (meth)acryloyl group, vinyl group, etc. are mentioned, and (meth)acryloyl group is preferable. Furthermore, 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 depending on the functional group of the functional group-containing monomer (a2), and examples include isocyanate group, carboxyl group, and epoxy group. From the viewpoint of reactivity, etc. , an isocyanate group is preferred. If 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 becomes possible to easily react with the acrylic copolymer (A0).

Specific polymerizable compounds (Xa) include, for example, (meth)acryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acryloyl isocyanate, allyl isocyanate, and glycyrrhizate. Dil (meth)acrylate, (meth)acrylic acid, etc. can be mentioned. These polymerizable compounds (Xa) may be used individually or in combination of two or more types.

Among these, (meth)acryloyloxyethyl isocyanate is preferable from the viewpoint of having a preferable isocyanate group as the reactive substituent and being a compound with an appropriate distance between the main chain and the energy ray polymerizable group.

From the viewpoint of controlling the amount of carbon-carbon double bonds of energy ray polymerization, the polymerizable compound (Xa) is preferable among the total amount (100 equivalents) of functional groups derived from the functional group-containing monomer (a2) in the acrylic copolymer (A0). Typically, 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 1.6 million, more preferably 400,000 to 1.4 million. By having this Mw, it becomes possible to provide appropriate adhesiveness to the adhesive layer.

Even when the adhesive resin has energy ray curability, it is preferable that the composition for the adhesive layer contains an energy ray curable compound other than the adhesive resin. As such an energy ray curable compound, a monomer or oligomer that has an unsaturated group in the molecule and can be 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, Polyhydric (meth)acrylate monomers such as 4-butylene glycol di(meth)acrylate, 1,6-hexanediol (meth)acrylate, urethane (meth)acrylate, polyester (meth)acrylate, polyether Oligomers such as (meth)acrylate and epoxy (meth)acrylate can be mentioned.

Among these, urethane (meth)acrylate oligomer is preferable because it has a relatively high molecular weight and from the viewpoint of keeping the surface resistivity of the adhesive layer within the above-mentioned range.

From the viewpoint of controlling the amount of energy ray polymerizable carbon-carbon double bonds, the content of the energy ray curable compound is preferably 0.1 to 300 parts by mass, more preferably 0.5 to 0.5 parts by mass, based on 100 parts by mass of the acrylic polymer (A). It is 200 parts by mass, more preferably 1 to 150 parts by mass.

(3.6.2 Cross-linking agent)

It is more preferable that the composition for an adhesive layer contains a crosslinking agent. The composition for the adhesive layer is crosslinked by a crosslinking agent, for example, by heating after application. When the adhesive layer crosslinks the acrylic polymer (A) with a crosslinking agent, a coating film is formed appropriately, and the adhesive layer functions easily.

Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, and a chelate-based crosslinking agent. Among these, an isocyanate-based crosslinking agent is preferable. The crosslinking agent may be used individually or in combination of two or more types.

Examples of the isocyanate-based crosslinking agent 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, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, etc. and alicyclic polyisocyanates. Additionally, these biuret forms, isocyanurate forms, and adduct forms that are reactants with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil can also be mentioned.

Among the above, polyhydric alcohol (e.g., trimethylolpropane, etc.) adduct body of aromatic polyisocyanate such as tolylene diisocyanate is preferable.

The content of the crosslinking 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).

(3.6.3 Light polymerization initiator)

The composition for the adhesive layer preferably further contains a photopolymerization initiator. When the composition for an adhesive layer contains a photopolymerization initiator, it becomes easy to advance energy ray curing of the composition for an adhesive layer by ultraviolet rays 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, and benzoin. Ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl diphenyl sulfide, tetramethyl thiuram monosulfide, benzyl dimethyl ketal, dibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2 -Ethylanthraquinone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2 -Morpholinopropanone-1,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-hydroxy-2-methyl-1-phenyl-propane-1 Low molecular weight polymerization initiators such as -one, diethylthioxanthone, isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, oligo{2-hydroxy-2-methyl-1-[ and oligomerized polymerization initiators such as 4-(1-methylvinyl)phenyl]propanone}.

Moreover, the photopolymerization initiator may be used individually or in combination of two or more types. Also, among the above, 2,2-dimethoxy-1,2-diphenylethan-1-one and 1-hydroxycyclohexylphenylketone are preferable.

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 even more preferably 0.05 to 5 parts by mass, based on 100 parts by mass of the acrylic polymer (A).

The composition for an adhesive layer may contain other additives within a range that does not impair the effect of the present invention. Other additives include, for example, tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When containing these additives, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.02 to 2 parts by mass, based on 100 parts by mass of the acrylic polymer (A).

In addition, the adhesive force of the adhesive layer can be adjusted, for example, by the type and amount of monomers constituting the acrylic polymer (A), the amount of energy ray polymerizable group introduced into the acrylic polymer (A), etc. Additionally, the surface resistivity of the adhesive layer can also be adjusted to some extent by these. In the above, the preferred range of the amount of the energy ray polymerizable group introduced into the acrylic polymer (A) is described. For example, if the amount of the energy ray polymerizable group is increased, the adhesive force after curing decreases and the surface resistivity increases. There is a tendency. However, the adhesive force and surface resistivity of the adhesive layer can be adjusted also by factors other than those mentioned above. For example, it can be adjusted appropriately depending on the amount of crosslinking agent mixed in the adhesive layer, the amount of photopolymerization initiator, etc.

(4. Anti-static layer)

The antistatic layer is disposed between the base material and the adhesive layer. In the antistatic layer, the antistatic component can prevent the electrostatic voltage from increasing by leaking the electric charge resulting from processing of the wafer to which the protective sheet for semiconductor processing is attached. The composition of the antistatic layer just needs to have antistatic properties to the extent that the peeling electrification voltage when peeling the adhesive layer from a wafer or the like can be set 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, more preferably 20 nm or more, and especially preferably 60 nm or more. Moreover, the thickness is preferably 300 nm or less, more preferably 250 nm or less, and still 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 (antistatic layer composition). Examples of such compositions 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. It is preferable that the composition for antistatic layer is 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, polythiophene-based polymer is preferred.

Examples of polythiophene polymers include polythiophene, poly(3-alkylthiophene), poly(3-thiophene-β-ethanesulfonic acid), polyalkylenedioxythiophene, and polystyrene sulfonate (PSS). ) and mixtures (including doped ones). Among these, a mixture of polyalkylene dioxythiophene and polystyrene sulfonate is preferable. Examples of the polyalkylenedioxythiophene include poly(3,4-ethylenedioxythiophene) (PEDOT), polypropylenedioxythiophene, poly(ethylene/propylene)dioxythiophene, and among these, poly(3) , 4-ethylenedioxythiophene) is preferred. That is, among the above, a mixture of poly(3,4-ethylenedioxythiophene) and polystyrenesulfonate (PEDOT doped with PSS) is particularly preferable.

Examples of polypyrrole-based polymers include polypyrrole, poly3-methylpyrrole, and poly3-octylpyrrole.

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

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

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

Additionally, the binder resin is not particularly limited. Examples include polyester resin, acrylic resin, polyvinyl resin, urethane resin, melamine resin, and epoxy resin. Additionally, a cross-linking agent may be used together. Examples of the crosslinking agent include methylolated or alkylolated melamine-based compounds, urea-based compounds, glyoxal-based compounds, acrylamide-based compounds, epoxy-based compounds, and isocyanate-based compounds.

The content of the antistatic agent in the antistatic layer composition may be appropriately determined depending on 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 base material on which the adhesive layer is formed. Below, the buffer layer is explained.

The buffer layer is a soft layer compared to the base material, and relieves stress during grinding of the back side of the wafer, preventing cracks and defects from occurring in 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 backside grinding, but by having a buffer layer as a constituent layer of the protective sheet for semiconductor processing, it is easy to be properly held on the vacuum table. Lose.

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

The thickness of the buffer layer is preferably 5 to 100 μm, more preferably 1 to 100 μm, and still more preferably 5 to 80 μm. By setting the thickness of the buffer layer within the above range, the stress during grinding of the back surface of the buffer layer can be appropriately alleviated.

The buffer layer may be a layer formed of a composition for a buffer layer containing an energy ray polymerizable compound, and may be a polypropylene film, an ethylene-vinyl acetate copolymer film, an ionomer resin film, an ethylene/(meth)acrylic acid copolymer film, or an ethylene/vinyl acetate copolymer film. It may be a film such as a (meth)acrylic acid ester copolymer film, LDPE film, or LLDPE film.

(5.1 Composition for buffer layer)

The composition for a buffer layer containing an energy ray polymerizable compound can be cured by irradiation with an energy ray.

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

Hereinafter, each component contained in the composition for a buffer layer containing an energy ray polymerizable compound will be described in detail.

(5.1.1 Urethane (meth)acrylate (b1))

Urethane (meth)acrylate (b1) is a compound having at least a (meth)acryloyl group and a urethane bond, and has the property of polymerization and hardening by energy ray irradiation. Urethane (meth)acrylate (b1) is an oligomer or polymer.

The weight average molecular weight (Mw) of component (b1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, and still more preferably 3,000 to 20,000. Additionally, 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 (meth)acrylate having a hydroxy group with a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound with a polyhydric isocyanate compound. In addition, component (b1) may be used individually or in combination of two or more types.

The polyol compound serving 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 bifunctional diols, trifunctional triols, and tetrafunctional or higher-functional polyols may be used, but bifunctional diols are preferable, and polyester-type diols or polycarbonate-type diols are more preferable.

Examples of the polyvalent isocyanate compound include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; Alicyclic products such as isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, ω,ω'-diisocyanate and dimethylcyclohexane. diisocyanates; Aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, and naphthalene-1,5-diisocyanate. there is.

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

Urethane (meth)acrylate (b1) can be obtained by reacting (meth)acrylate having a hydroxy group with a terminal isocyanate urethane prepolymer obtained by reacting the polyol compound described above with 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 examples of (meth)acrylates having a hydroxy group include 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 Hydroxyalkyl (meth)acrylates such as mono (meth)acrylate and polypropylene glycol mono (meth)acrylate; Hydroxyl group-containing (meth)acrylamide such as N-methylol (meth)acrylamide; Reactants obtained by reacting vinyl alcohol, vinyl phenol, and diglycidyl ester of bisphenol A with (meth)acrylic acid; etc. can be mentioned.

Among these, hydroxyalkyl (meth)acrylate is preferable and 2-hydroxyethyl (meth)acrylate is more preferable.

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

(5.1.2 Polymerizable compound (b2) having an alicyclic or heterocyclic group having 6 to 20 ring atoms)

Component (b2) is a polymerizable compound having an alicyclic or heterocyclic group having 6 to 20 ring atoms, and is more preferably a compound having at least one (meth)acryloyl group, more preferably It is a compound having one (meth)acryloyl group. By using component (b2), the film-forming properties of the resulting composition for a buffer layer can be improved.

Specific components (b2) include, for example, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, (meth)acrylates containing alicyclic groups such as cyclohexyl (meth)acrylate and adamantane (meth)acrylate; Heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate; etc. can be mentioned. In addition, component (b2) may be used individually or in combination of two or more types. Among alicyclic group-containing (meth)acrylates, isobornyl (meth)acrylate is preferable, and among heterocyclic group-containing (meth)acrylates, tetrahydrofurfuryl (meth)acrylate is preferable.

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

(5.1.3 Polymerizable compound with functional group (b3))

Component (b3) is a polymerizable compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group, and an amino group, and is further preferably a compound having at least one (meth)acryloyl group, more preferably 1 It is a compound with two (meth)acryloyl groups.

Component (b3) has good compatibility with component (b1), making it easy to adjust the viscosity of the composition for buffer layer to an appropriate range. Additionally, even if the buffer layer is relatively thin, the buffering performance becomes good.

Examples of the component (b3) include hydroxyl group-containing (meth)acrylate, epoxy group-containing compound, amide group-containing compound, and amino group-containing (meth)acrylate. Among these, hydroxyl group-containing (meth)acrylates are preferable.

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

In addition, component (b3) may be used individually or in combination of two or more types. The content of component (b3) in the composition for buffer layer is preferably 5 to 40% by mass, more preferably 7% by mass, based on the total amount (100% by mass) of the composition for buffer layer, in order to improve the film forming property of the composition for buffer layer. to 35 mass%, more preferably 10 to 30 mass%.

(5.1.4 Polymerizable compounds (b4) other than components (b1) to (b3))

The composition for forming a buffer layer may contain other polymerizable compounds (b4) other than the above-mentioned components (b1) to (b3), as long as the effect of the present invention is not impaired.

Examples of component (b4) include alkyl (meth)acrylate having an alkyl group having 1 to 20 carbon atoms; Vinyl compounds such as styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, and N-vinylcaprolactam; and the like. In addition, component (b4) may be used individually or in combination of two or more types.

The content of component (b4) in the composition for forming a buffer layer is preferably 0 to 20 mass%, more preferably 0 to 10 mass%, further preferably 0 to 5 mass%, especially preferably 0 to 2 mass%. %am.

(5.1.5 Light polymerization initiator)

The composition for a buffer layer 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 the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specifically, for example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl. Ether, benzoin isopropyl ether, benzylphenylsulfide, tetramethylthiuram monosulfide, azobisisobutyrolnitrile, dibenzyl, diacetyl, 8-chloranthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosph. Pin oxide, etc. can be mentioned.

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

The content of the photopolymerization initiator in the composition for a buffer layer is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and still more preferably 0.3 to 5 parts by mass, based on the total amount of 100 parts by mass of the energy ray polymerizable compound. It is wealth.

(5.1.6 Other additives)

The composition for a buffer layer may contain other additives within a range that does not impair the effect of the present invention. Other additives include, for example, antistatic agents, antioxidants, softeners (plasticizers), fillers, rust preventives, pigments, dyes, etc. When blending these additives, the content of each additive in the buffer layer composition is preferably 0.01 to 6 parts by mass, more preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the total amount of the energy ray polymerizable compound.

A buffer layer formed from a composition for a buffer layer containing an energy ray polymerizable compound is obtained by polymerizing and curing a composition for a buffer layer of the above composition by irradiation with an energy ray. That is, the buffer layer is a cured product of the composition for a buffer layer.

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

(6. Release sheet)

A release sheet may be affixed to the surface of the protective sheet for semiconductor processing. Specifically, the release sheet is affixed to the surface of the 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 attached to the protective sheet for semiconductor processing in a peelable manner, and is peeled and removed from the protective sheet for semiconductor processing before the protective sheet for semiconductor processing is used (i.e., before attaching the wafer).

As the release sheet, a release sheet on which at least one side has been subjected to a release treatment is used, and specific examples thereof include those in which a release agent is applied onto the surface of the base material for the release sheet.

As the base material for the release sheet, a resin film is preferable, and examples of the resin constituting the resin film include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, and polypropylene. Polyolefin resins, such as resin and polyethylene resin, are mentioned. Examples of the release agent 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, and fluorine-based resins.

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

(7. Manufacturing method of protective sheet for semiconductor processing)

The method of manufacturing the protective sheet for semiconductor processing according to this embodiment is not particularly limited as long as it can form an antistatic layer and an adhesive layer on the main surface of the substrate, and a known method may be used. Below, a method for manufacturing the protective sheet for semiconductor processing shown in FIG. 1A will be described.

First, as a composition for forming an antistatic layer, for example, a composition for an antistatic layer containing the above-mentioned components, or a composition obtained by diluting the composition for an antistatic layer with a solvent or the like is prepared. Similarly, as a composition for an adhesive layer for forming an adhesive layer, for example, a composition for an adhesive layer containing the above-mentioned components or a composition obtained by diluting the composition for an adhesive layer with a solvent or the like is prepared.

Examples of the solvent 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 treatment surface of the first release sheet by spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc. It is applied by a known method and heated and dried to form an antistatic layer on the first release sheet. Thereafter, the antistatic layer on the first release sheet and one side of the substrate are bonded together, and the first release sheet is removed.

Next, the composition for an adhesive layer is applied to the peel-treated surface of the second release sheet by a known method, and is heated and dried to form an adhesive layer on the second release sheet. Thereafter, the adhesive layer on the second release sheet and the antistatic layer on the substrate are bonded together to obtain a protective sheet for semiconductor processing in which the antistatic layer and the adhesive layer are formed in this order on one main surface of the substrate. Additionally, the second release sheet may be removed when using the protective sheet for semiconductor processing.

In addition, when manufacturing the protective sheet for semiconductor processing shown in FIG. 1B, it may be done as follows.

First, as a buffer layer composition for forming a buffer layer, for example, a buffer layer composition containing the above-mentioned components or a composition obtained by diluting the buffer layer composition with a solvent or the like is prepared. 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 bonded to the other side of the substrate, and the buffer layer film is completely cured to form a buffer layer on the substrate.

In this embodiment, curing of the coating film is preferably performed by irradiation of energy rays. In addition, curing of the coating film may be performed in a single curing treatment or may be performed in multiple installments.

After forming the buffer layer on the substrate, an antistatic layer and an adhesive layer are formed as described above to manufacture the protective sheet for semiconductor processing shown in FIG. 1B. Additionally, a buffer layer may be formed after forming the antistatic layer and the adhesive layer on the substrate.

(8. Manufacturing method of semiconductor device)

The protective sheet for semiconductor processing according to the present invention is preferably used in DBG when it is attached to the surface of a semiconductor wafer and the back side of the wafer is ground. In particular, the protective sheet for semiconductor processing according to the present invention is preferably used in LDBG, where a group of chips with a small kerf width is obtained when the semiconductor wafer is separated into pieces.

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

The manufacturing method of a semiconductor device specifically includes at least the following steps 1 to 4.

Step 1: A step of attaching the above protective sheet for semiconductor processing to the surface of a semiconductor wafer.

Process 2: A process of forming a groove from the surface side of the semiconductor wafer, or forming a modified region inside the semiconductor wafer from the front or back side of the semiconductor wafer.

Step 3: A protective sheet for semiconductor processing is attached to the surface, and the semiconductor wafer on which the groove or modified area is formed is ground from the back side, and the groove or modified area is used as a starting point to separate the semiconductor wafer into a plurality of chips.

Process 4: Process of peeling the protective sheet for semiconductor processing from the separated semiconductor wafer (i.e., chip group)

Hereinafter, each step of the semiconductor device manufacturing method will be described in detail.

(Process 1)

In step 1, as shown in FIG. 2, the main surface 30a of the adhesive layer 30 of the protective sheet 1 for semiconductor processing according to this 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.

This step may be performed before Step 2, which will be described later, or after Step 2. For example, when forming a modified region on a semiconductor wafer, it is preferable to perform step 1 before step 2. On the other hand, when forming grooves on the surface of the semiconductor wafer by dicing or the like, Process 1 is performed after Process 2. That is, in this process 1, the protective sheet for semiconductor processing is attached to the surface of the wafer having the groove formed in process 2, which will be described later.

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

The thickness of the semiconductor wafer before grinding is not particularly limited, but is usually about 500 to 1000 μm. Additionally, a semiconductor wafer usually has a circuit formed on its surface. Circuit formation on the wafer surface can be performed by various methods, including conventionally used methods such as etching and lift-off methods.

(Process 2)

In step 2, a groove is formed from the surface side of the semiconductor wafer. Alternatively, a modified region is formed inside the semiconductor wafer from the front or back surface of the semiconductor wafer.

The groove formed in this process is a groove whose depth is 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. Additionally, the semiconductor wafer is divided into a plurality of semiconductor chips along the groove in step 3 described later.

In addition, the modified area is a nitrided portion of the semiconductor wafer, and the modified area of the semiconductor wafer becomes thinner due to grinding in the grinding process or the application of force due to grinding. This is the starting point for destruction and reorganization into semiconductor chips. That is, in step 2, the grooves and modified regions are formed to follow the dividing line when the semiconductor wafer is divided into semiconductor chips in step 3, which will be described later.

The formation of the modified region is performed by irradiation of a laser focused on the inside of the semiconductor wafer, and the modified region is formed inside the semiconductor wafer. Laser irradiation may be performed from the front side or the back side of the semiconductor wafer. In addition, in the aspect of forming the modified region, when step 2 is performed after step 1 and laser irradiation is performed from the wafer surface, the laser is irradiated to the semiconductor wafer through the protective sheet for semiconductor processing.

A semiconductor wafer with a protective sheet for semiconductor processing attached and a groove or modified region formed thereon is placed on a chuck table and held by adsorption on the chuck table. At this time, the semiconductor wafer is adsorbed with its surface side placed on the table side.

(Process 3)

After steps 1 and 2, the back side of the semiconductor wafer on the chuck table is ground, the semiconductor wafer is divided into a plurality of semiconductor chips, and a group of chips is obtained.

Here, when a groove is formed in the semiconductor wafer, back side grinding is performed to thin the semiconductor wafer at least to a position reaching the bottom of the groove. By this back-side grinding, the groove becomes a notch penetrating the wafer, and the semiconductor wafer is divided by the notch and divided into individual semiconductor chips.

On the other hand, when a modified region is formed, the ground surface (back surface of the wafer) may reach the modified region by grinding, but it does not have to strictly reach the modified region. In other words, the semiconductor wafer may be broken starting from the modified area and ground into a position close to the modified area so that it is broken into pieces into semiconductor chips. For example, the actual separation of the semiconductor chip may be performed by attaching a pickup tape, which will be described later, and then stretching the pickup tape.

Additionally, dry polishing may be performed after completion of back grinding and prior to chip pickup.

The shape of the individualized semiconductor chip may be rectangular or may be an elongated shape such as a rectangle. Additionally, the thickness of the divided semiconductor chip is not particularly limited, but is preferably about 5 to 100 μm, and more preferably 10 to 45 μm. According to LDBG, which creates a modified area inside the wafer with a laser and separates the wafer into pieces due to stress during grinding of the back side of the wafer, the thickness of the divided semiconductor chips is 50 ㎛ or less, more preferably 10 to 45 ㎛. It becomes easier to do so. Additionally, the size of the separated semiconductor chip is not particularly limited, but the chip size is preferably less than 600 mm2, more preferably less than 400 mm2, and even more preferably less than 120 mm2.

By using the protective sheet for semiconductor processing according to this embodiment, even for thin and/or small semiconductor chips, electrification is prevented during back side grinding (step 3) and when peeling off the protective sheet for semiconductor processing (step 4), and furthermore, the semiconductor chip This prevents cracks from occurring in the chip.

(Process 4)

Next, the protective sheet for semiconductor processing is peeled from the separated semiconductor wafer (i.e., plural semiconductor chips). This process is performed, for example, by the following method.

In this embodiment, since the adhesive layer of the protective sheet for semiconductor processing is formed of an energy ray-curable adhesive, the adhesive layer is cured and shrunk by irradiating an energy ray, thereby lowering the adhesive strength to the adherend (pieced semiconductor wafer). . Next, a pickup tape is attached to the back side of the separated semiconductor wafer, and the position and orientation are adjusted to enable pickup. At this time, the ring frame placed on the outer periphery side of the wafer is also bonded 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 bonded to the pickup tape at the same time or may be bonded at separate timings. Next, the protective sheet for semiconductor processing is peeled from the plurality of semiconductor chips held on the pickup tape.

Since the protective sheet for semiconductor processing according to the present embodiment has the above-mentioned characteristics, even if the peeling speed when peeling the protective sheet for semiconductor processing from the semiconductor wafer is high, charging is suppressed, and no glue residue is formed on the semiconductor wafer, etc., and chip Peeling can be performed while contact between the two is suppressed.

Thereafter, a plurality of semiconductor chips on the pickup tape are picked up and fixed on a substrate or the like to manufacture a semiconductor device.

In addition, the pick-up tape is not particularly limited, but is comprised, for example, of an adhesive sheet including a base material and an adhesive layer provided on one side of the base material.

Above, an example of using the protective sheet for semiconductor processing according to the present invention in a method of dividing a semiconductor wafer into pieces using DBG or LDBG has been described. However, the protective sheet for semiconductor processing according to the present invention can be used to separate a semiconductor wafer into pieces. In this case, it can be preferably used in LDBG where the kerf width is small and a thinner chip group is obtained. In this case, it is more preferable to use the protective sheet for semiconductor processing shown in FIG. 1B.

Although the embodiments of the present invention have been described above, the present invention is not limited in any way to the above-described embodiments, and may be modified into various aspects within the scope of the present invention.

Example

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

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

(Surface resistivity of adhesive layer after energy ray curing)

The protective sheet for semiconductor processing produced in Examples and Comparative Examples was cut into a size of 10 cm x 10 cm, and the adhesive layer of the protective sheet for semiconductor processing was irradiated with ultraviolet rays and cured. With respect to the adhesive layer after curing, the surface resistivity was measured using a surface resistivity meter R8252 manufactured by Advantest Corporation under the conditions of 23°C 50%RH and an applied voltage of 100 V in accordance with JIS K 7194.

(90° peel adhesion 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 and used as test pieces. The adhesive layer of the test piece was attached to a silicon mirror wafer without a circuit surface using a roller with a mass of 2 kg. After leaving for 1 hour, the test piece was peeled at a peeling rate of 600 mm/min at a 90° angle to the silicon mirror wafer in accordance with JIS Z 0237, and the adhesive force (90° peeled adhesive force of the adhesive layer before energy ray curing) was measured. .

Additionally, the adhesive layer of another test piece was attached to the silicon miller wafer with a roller with a mass of 2 kg. The adhesive layer of this test piece was cured by irradiating ultraviolet rays from the base surface side of the protective sheet for semiconductor processing under the conditions of an illuminance of 220 mW/cm2 and a light amount of 380 mJ/cm2, and then, in accordance with JIS Z 0237, a silicon miller wafer. The test piece was peeled at a peeling rate of 600 mm/min to become 90° with respect to the adhesive force (90° peeling adhesive force of the adhesive layer after energy ray curing) was measured.

(Peeling charge voltage of protective sheet for semiconductor processing)

The protective sheet for semiconductor processing produced in the examples and comparative examples was attached to the surface of the silicon wafer, using a wafer mounter (product name “RAD-2700F/12”, manufactured by LINTEC Corporation) at a peeling speed of 600 mm/min and a temperature of 40°C. While peeling the protective sheet for semiconductor processing from the silicon wafer under the conditions of The voltage value was taken as the peeling charge voltage value. In this example, samples with a peeling electrification voltage of 500 V or less were judged to be good.

(crack incidence rate)

The protective sheet for semiconductor processing produced in Examples and Comparative Examples was attached to a silicon wafer with a diameter of 12 inches and a thickness of 775 μm using a tape laminator for backgrinding (manufactured by LINTEC Corporation, device name “RAD-3510F/12”). . A lattice-like modified region was formed on the wafer using a laser saw (manufactured by DISCO CORPORATION, device name “DFL7361”). Additionally, the grid size was set to 10 mm × 10 mm.

Next, using a backside grinding device (manufactured by DISCO CORPORATION, device name “DGP8761”), grinding (including dry polishing) was performed until the thickness reached 30 μm, and the wafer was separated into a plurality of chips.

After the grinding process, energy ray (ultraviolet ray) irradiation was performed, and a dicing tape (Adwill D-175, manufactured by LINTEC Corporation) was attached to the opposite side of the adhesive surface of the semiconductor processing protective sheet, and then the semiconductor processing protective sheet was peeled. Afterwards, the individually divided chips were observed with a digital microscope (product name "VHX-1000", manufactured by KEYENCE CORPORATION), chips with cracks were counted, and each crack size was classified according to the following criteria. Additionally, the size of the crack (μm) was set to be larger compared to the length of the crack (μm) along the longitudinal direction of the chip and the length of the crack (μm) along the transverse direction of the chip.

(standard)

Large crack: Crack size exceeds 50㎛

Medium crack: The size of the crack is 20㎛ or more and 50㎛ or less.

Small crack: Crack size is less than 20㎛

Additionally, the crack incidence rate (%) was calculated based on the formula below. Cases where the crack occurrence rate was 2.0% or less and the number of major cracks was 0, medium cracks were 10 or less, and minor cracks were 20 or less were evaluated as “good,” and other cases were evaluated as “poor.” .

Crack incidence rate (%) = (Number of chips with cracks/Total number of chips) × 100

(Example 1)

(1) Adhesive layer

(Preparation of composition for adhesive layer)

An acrylic polymer obtained by copolymerizing 65 parts by mass of butylacrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 15 parts by mass of 2-hydroxyethyl acrylate (2HEA), containing 80 mol of the total hydroxyl groups of the acrylic polymer. 2-methacryloyloxyethyl isocyanate (MOI) was reacted to add % of hydroxyl group, and an energy ray-curable acrylic resin (Mw: 500,000) was obtained. To 100 parts by mass of this energy ray-curable acrylic resin, 6 parts by weight of polyfunctional urethane acrylate (product name: Jagwang UT-4332, manufactured by Mitsubishi Chemical Corporation), which is an energy ray-curable compound, and an isocyanate-based crosslinking agent (manufactured by TOSOH CORPORATION, brand name: CORONATE) A coating solution for the composition for an adhesive layer was prepared by adding 0.375 parts by mass of L) and 1 part by weight of a photopolymerization initiator consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and diluting with a solvent.

(Formation of adhesive layer)

A solution of the above-described pressure-sensitive adhesive composition was applied onto the release-treated side of a release sheet (manufactured by LINTEC Corporation, brand name “SP-PET381031”, polyethylene terephthalate (PET) film subjected to silicone release treatment, thickness: 38 μm), It was dried, and a release sheet with an adhesive layer having an adhesive layer with a thickness of 20 μm was produced.

(2) Production of substrate with antistatic layer

As a base material, a 50-μm-thick primer-coated PET film (manufactured by TOYOBO CO., LTD., brand name “PET50A-4100”) provided with a primer layer (first primer layer) on one side was prepared. The Young's modulus of this PET film was 2500 MPa.

A polythiophene-based conductive polymer (Denatron P-400MP, manufactured by Nagase Chemtex Corporation) is applied and dried on the side of the PET film opposite to that on which the first primer layer is provided, and an antistatic layer with a thickness of 120 nm is formed on the PET film. formed on the table.

(3) Buffer layer

(Synthesis of urethane acrylate oligomer (UA-1))

A terminal isocyanate urethane prepolymer obtained by reacting polyester diol and isophorone diisocyanate was reacted with 2-hydroxyethyl acrylate to produce a bifunctional urethane acrylate-based oligomer (UA-1) with a weight average molecular weight (Mw) of 5000. ) was obtained.

(Preparation of composition for forming buffer layer)

As an energy ray polymerizable compound, 40 parts by mass of the urethane acrylate-based oligomer (UA-1) synthesized above, 40 parts by mass of isobornyl acrylate (IBXA), and 20 parts by mass of phenylhydroxypropyl acrylate (HPPA) 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 were further mixed to prepare a composition for forming a buffer layer.

(Formation of buffer layer)

The above composition for forming a buffer layer is applied onto the peeled side of a release sheet (manufactured by LINTEC Corporation, brand name “SP-PET381031”, polyethylene terephthalate (PET) film subjected to silicone release treatment, thickness: 38 μm). A membrane was formed. Then, the coating film was irradiated with ultraviolet rays to semi-cure the coating film, thereby forming a buffer layer forming film with a thickness of 50 μm.

In addition, the above ultraviolet irradiation is performed using a belt conveyor type ultraviolet irradiation device (product name "ECS-401GX", manufactured by EYE GRAPHICS CO., LTD.) and a high-pressure mercury lamp (H04-L41 manufactured by EYE GRAPHICS CO., LTD.: H04- L41) was used under the irradiation conditions of lamp height of 150 mm, lamp output of 3 kW (equivalent output of 120 mW/cm), illuminance of 120 mW/cm2 with light wavelength of 365 nm, and irradiation amount of 100 mJ/cm2.

The surface of the formed buffer layer forming film and the first primer layer of the base material with the antistatic layer are bonded together, and ultraviolet rays are irradiated again from the side of the release sheet on the buffer layer forming film to completely cure the buffer layer forming film, forming a buffer layer with a thickness of 50 μm. did.

In addition, the above ultraviolet irradiation uses the above-mentioned ultraviolet irradiation device and a high-pressure mercury lamp, with a lamp height of 150 mm, a lamp output of 3 kW (equivalent output of 120 mW/cm), an illuminance of 160 mW/cm2 with a light wavelength of 365 nm, and an irradiation amount of 500 mJ. It was conducted under irradiation conditions of ／㎠.

(4) Production of protective sheets for semiconductor processing

By bonding the adhesive layer of a release sheet with an adhesive layer onto the antistatic layer, an antistatic layer and an adhesive layer are formed in this order on one main surface of the base material, and a buffer layer is formed on the other main surface of the base material. Protection for semiconductor processing Made a sheet.

(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 antistatic layer thickness was 80 nm and the adhesive layer thickness was 200 μm.

(Example 4)

A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that the adhesive layer was formed using the following composition for the adhesive layer.

(Preparation of composition for adhesive layer)

89 parts by mass of n-butylacrylate (BA), 8 parts by mass of methyl methacrylate (MMA), and 3 parts by mass of 2-hydroxyethyl acrylate (2HEA) were copolymerized to obtain an acrylic polymer (Mw: 800,000).

For 100 parts by mass of the above-mentioned acrylic polymer, 1 part by mass (solid content) of a tolylene diisocyanate-based crosslinking agent (manufactured by TOSOH CORPORATION, product name “CORONATE L”) as a crosslinking agent, and an epoxy-based crosslinking agent (1,3-bis(N,N-di) 2 parts by mass (solid content) of glycidylaminomethyl) cyclohexane, 45 parts by mass (solid content) of an energy ray curable compound (manufactured by Mitsubishi Chemical Corporation, product name “Jakwang UV-3210EA”), and a photopolymerization initiator (manufactured by IGM Resins, Inc.) Product name "OMNIRAD184") 1 mass part (solid content) was mixed and diluted with a solvent to obtain a coating liquid of the composition for an adhesive layer.

(Example 5)

A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that an adhesive layer was formed to a thickness of 5 μm using the following composition for an adhesive layer, and the thickness of the antistatic layer was changed to 25 nm.

(Preparation of composition for adhesive layer)

An acrylic polymer obtained by copolymerizing 75 parts by mass of butylacrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 5 parts by mass of 2-hydroxyethyl acrylate (2HEA), containing 90 mol of the total hydroxyl groups of the acrylic polymer. 2-methacryloyloxyethyl isocyanate (MOI) was reacted to add % of hydroxyl group, and an energy ray-curable acrylic resin (Mw: 500,000) was obtained.

To 100 parts by mass of this energy-ray curable acrylic resin, 0.375 parts by mass based on solid content of an isocyanate-based crosslinking agent (manufactured by TOSOH CORPORATION, brand name: CORONATE L) is composed of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. A coating liquid for the composition for an adhesive layer was prepared by adding 1 part by weight of a photopolymerization initiator and diluting it with a solvent.

(Example 6)

Low-density polyethylene (LDPE; manufactured by Sumitomo Chemical Company, Limited, Sumikasen L705) was extruded using a small T-die extruder to obtain an LDPE film with a thickness of 100 μm. Corona treatment was performed on one side of the same LDPE film, and a polythiophene-based conductive polymer (Denatron P-400MP, manufactured by Nagase Chemtex Corporation) was applied and dried on the corona-treated side to form an antistatic layer with a thickness of 120 nm. was formed on an LDPE film, and a base material with an antistatic layer was obtained.

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 bonded 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 the antistatic layer was not provided.

(Comparative Example 2)

An adhesive layer was formed using the following composition for an adhesive layer, and 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 50 nm.

(Preparation of composition for adhesive layer)

An acrylic polymer obtained by copolymerizing 65 parts by mass of butylacrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 15 parts by mass of 2-hydroxyethyl acrylate (2HEA), containing 90 mol of the total hydroxyl groups of the acrylic polymer. 2-methacryloyloxyethyl isocyanate (MOI) was reacted to add % of hydroxyl group, and an energy ray-curable acrylic resin (Mw: 500,000) was obtained.

To 100 parts by mass of this energy ray curable acrylic resin, 20 parts by weight of polyfunctional urethane acrylate (product name: Jagwang UT-4332, manufactured by Mitsubishi Chemical Corporation), which is an energy ray curable compound, isocyanate-based crosslinking agent (manufactured by TOSOH CORPORATION, brand name: CORONATE) A coating solution for the composition for an adhesive layer was prepared by adding 0.375 parts by mass of L) and 1 part by weight of a photopolymerization initiator consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and diluting with a solvent.

(Comparative Example 3)

A protective sheet for semiconductor processing was obtained in the same manner as in Example 1, except that the adhesive layer was formed using the following composition for the adhesive layer.

(Preparation of composition for adhesive layer)

An acrylic polymer obtained by copolymerizing 75 parts by mass of butylacrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 5 parts by mass of 2-hydroxyethyl acrylate (2HEA), containing 50 mol of the total hydroxyl groups of the acrylic polymer. 2-methacryloyloxyethyl isocyanate (MOI) was reacted to add % of hydroxyl group, and an energy ray-curable acrylic resin (Mw: 500,000) was obtained.

To 100 parts by mass of this energy-ray curable acrylic resin, 0.375 parts by mass based on solid content of an isocyanate-based crosslinking agent (manufactured by TOSOH CORPORATION, brand name: CORONATE L) is composed of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. A coating liquid for the composition for an adhesive layer was prepared by adding 1 part by weight of a photopolymerization initiator and diluting it with a solvent.

[Table 1]

The above measurements and evaluations were performed on the obtained samples (Examples 1 to 6 and Comparative Examples 1 to 3). SR/T ² was calculated from the surface resistivity and thickness of the adhesive layer. In addition, the adhesive force ratio was calculated from the 90° peel adhesive force of the adhesive layer before and after energy ray curing. The results are shown in Table 1.

In Table 1, when the surface resistivity of the adhesive layer of the protective sheet for semiconductor processing is within the above-mentioned range and the protective sheet for semiconductor processing includes an antistatic layer, the electrostatic voltage accompanying peeling of the protective sheet for semiconductor processing is low, Additionally, it was confirmed that the crack incidence rate due to chip shift was low.

1: Protection sheet for semiconductor processing
10: Description
20: Antistatic layer
30: Adhesive layer
40: buffer layer

Claims (7)

It has a base material, an antistatic layer, and an energy ray curable adhesive layer,
A protective sheet for semiconductor processing, wherein the surface resistivity of the adhesive layer after energy ray curing is 5.1 × 10 ¹² Ω/cm2 or more and 1.0 × 10 ¹⁵ Ω/cm2 or less. According to paragraph 1,
If the surface resistivity is SR [Ω/cm2] and the thickness of the adhesive layer is T [㎛], SR/T ² is 8.0 × 10 ⁹ [Ω / cm ² ] or more 5.0 × 10 ¹³ [Ω / cm ㎛ ² ] or less, protective sheet for semiconductor processing. According to claim 1 or 2,
A protective sheet for semiconductor processing, wherein the adhesive force when the adhesive layer after energy ray curing is peeled from the silicon wafer at a peeling speed of 600 mm/min so that the angle formed between the adhesive layer and the silicon wafer is 90° is less than 0.15 N/25 mm. According to any one of claims 1 to 3,
Regarding the adhesive strength when the adhesive layer before energy ray curing is peeled from the silicon wafer at a peeling speed of 600 mm/min so that the angle formed between the adhesive layer and the silicon wafer is 90°, the adhesive layer after energy ray curing is peeled from the silicon wafer. A protective sheet for semiconductor processing, wherein the adhesive strength ratio when peeled at a peeling speed of 600 mm/min so that the angle formed between the adhesive layer and the silicon wafer is 90° is 4% or less. According to any one of claims 1 to 4,
The protective sheet for semiconductor processing further includes a buffer layer. According to any one of claims 1 to 5,
A protective sheet for semiconductor processing that is used by being attached to the surface of a wafer in a process of dividing a wafer into chips by grinding the back side of the wafer on which grooves are formed on the surface or modified regions on the inside. A step of attaching the protective sheet for semiconductor processing according to any one of claims 1 to 6 to the surface of a wafer;
A process of forming a groove from the front side of the wafer, or a process of forming a modified region inside the wafer from the front or back side of the wafer;
A process of grinding a wafer on which the protective sheet for semiconductor processing is attached to a surface and having the groove or the modified region formed thereon from the back side, and dividing the wafer into a plurality of chips using the groove or the modified region as a starting point;
A method of manufacturing a semiconductor device, comprising a step of peeling the protective sheet for semiconductor processing from the separated chip.