JP7555908B2 - Protective sheet for semiconductor processing and method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device. In particular, the present invention relates to a protective sheet for semiconductor processing that is preferably used to suppress warping of a semiconductor wafer, and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing.

Various electronic devices are equipped with a large number of semiconductor devices mounted with semiconductor chips obtained by singulating semiconductor wafers on which circuits are formed. Semiconductor wafers on which circuits are formed may have circuit protection layers formed thereon, such as a passivation film to protect the circuits from the external environment and a passivation film for bump formation. Such circuit protection layers mechanically and chemically protect the circuits formed on the semiconductor wafer.

In addition, electronic devices are rapidly becoming smaller and more multifunctional, and semiconductor chips are also being required to be smaller, thinner, and more dense. To make chips smaller and thinner, it is common to form circuits on the front side of a semiconductor wafer, then grind the back side of the semiconductor wafer to adjust the thickness of the chip.

When grinding the backside of a semiconductor wafer, a protective sheet called backgrind tape is applied to the wafer surface to prevent contamination of the wafer surface during grinding and to hold the semiconductor wafer in place. Although the application of such a protective sheet improves grinding quality, the application of the protective sheet causes residual stress in the protective sheet.

Because the semiconductor wafer before back grinding has high rigidity, the residual stress in the protective sheet is counteracted. However, when the semiconductor wafer becomes thinner by back grinding, the rigidity of the semiconductor wafer decreases, causing the residual stress in the protective sheet to become apparent, and the semiconductor wafer, with its reduced rigidity, warps together with the protective sheet.

Furthermore, in semiconductor wafers on which a circuit protection layer is formed, residual stress is generated in the semiconductor wafer during the formation of the circuit protection layer, and therefore, after back grinding, the residual stress in the protection sheet and the residual stress in the semiconductor wafer tend to cause significant warping of the semiconductor wafer. When the semiconductor wafer warps, problems arise such as the semiconductor wafer becoming more susceptible to breakage and the difficulty of transporting it to the next process.

To address such problems, for example, Patent Document 1 discloses a surface protection sheet in which the substrate is endowed with high stress relaxation properties in order to suppress warping of semiconductor wafers.

International Publication No. 2016/063827

In Patent Document 1, warping of a semiconductor wafer is suppressed by imparting stress relaxation properties to the substrate and eliminating residual stress occurring in the substrate. However, the protective sheet described in Patent Document 1 cannot eliminate residual stress occurring in the semiconductor wafer itself, such as a semiconductor wafer on which a circuit protection layer is formed. As a result, there is a problem in that when residual stress occurs in the semiconductor wafer itself, warping of the semiconductor wafer cannot be suppressed.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a protective sheet for semiconductor processing that can suppress warping of a semiconductor wafer when applied to a semiconductor wafer having residual stress, and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing.

An aspect of the present invention is
[1] A protective sheet for semiconductor processing having a substrate, an intermediate layer and a pressure-sensitive adhesive layer on the substrate in this order,
the product of the tensile storage modulus of the substrate and the thickness of the substrate is 8.0×10 ⁵ N/m or less;
The protective sheet for semiconductor processing has an intermediate layer with a residual stress of 10,000 Pa or less after being held at 65° C. for 300 seconds.

[2] A protective sheet for semiconductor processing as described in [1], in which the loss tangent of the intermediate layer at 65°C is 0.6 or more.

[3] A step of attaching the protective sheet for semiconductor processing according to [1] or [2] to a semiconductor wafer in which residual stress has occurred;
and reducing the rigidity of the semiconductor wafer to which the protective sheet for semiconductor processing is attached.

According to the present invention, it is possible to provide a protective sheet for semiconductor processing that, when applied to a semiconductor wafer having residual stress, can suppress warping of the semiconductor wafer more than conventional protective sheets, and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing.

FIG. 1 is a schematic cross-sectional view showing an example of a protective sheet for semiconductor processing according to this embodiment. FIG. 2 is a schematic cross-sectional view showing a state in which the protective sheet for semiconductor processing according to this embodiment is attached to the circuit surface of a semiconductor wafer. FIG. 3A is a schematic cross-sectional view showing a semiconductor wafer after back grinding, to which a protective sheet for semiconductor processing is not attached. FIG. 3B is a schematic cross-sectional view showing a semiconductor wafer having a conventional protective sheet for semiconductor processing attached thereto after back grinding. FIG. 3C is a schematic cross-sectional view showing a semiconductor wafer after backside grinding to which the protective sheet for semiconductor processing according to this embodiment has been attached. FIG. 3D is a schematic cross-sectional view showing a semiconductor wafer after backside grinding to which the protective sheet for semiconductor processing according to this embodiment has been attached. FIG. 4 is a schematic cross-sectional view for explaining that the residual stress of the intermediate layer is low in the protective sheet for semiconductor processing according to this embodiment.

The present invention will now be described in detail with reference to specific embodiments in the following order:

(1. Protective sheet for semiconductor processing)
The semiconductor processing protective sheet 1 according to the present embodiment has a structure in which an intermediate layer 20 and an adhesive layer 30 are laminated in this order on a substrate 10, as shown in Fig. 1. The semiconductor processing protective sheet is not limited to the structure shown in Fig. 1, and may have other layers as long as the effects of the present invention can be obtained. For example, a release sheet may be formed on the main surface 30a of the adhesive layer 30 in order to protect the adhesive layer 30 until the adhesive layer 30 is attached to the adherend.

The semiconductor processing protective sheet according to this embodiment is preferably used for semiconductor wafers in which residual stress occurs before the semiconductor processing protective sheet is applied. Examples of such semiconductor wafers include semiconductor wafers on which circuit protection layers such as various passivation films are formed.

As shown in Figure 2, the semiconductor processing protective sheet 1 of this embodiment is used by attaching the main surface 30a of the adhesive layer 30 to the main surface 51a of the circuit protection layer 51 formed on the circuit surface 50a of the semiconductor wafer 50.

In semiconductor wafers having a circuit protection layer, residual stress occurs in the semiconductor wafer when the applied circuit protection layer composition is thermally cured. However, because the rigidity of the semiconductor wafer before back grinding is high, this residual stress is countered by the rigidity of the semiconductor wafer itself.

However, after grinding the semiconductor wafer, the thickness of the semiconductor wafer is reduced, and the rigidity of the semiconductor wafer is reduced. Therefore, when the semiconductor wafer is ground without a semiconductor processing protective sheet attached, a warp Wa occurs due only to the residual stress generated in the semiconductor wafer, as shown in Figure 3A.

When grinding the backside of a semiconductor wafer, in order to ensure uniformity in the grinding and to prevent contamination of the circuit surface by grinding debris, etc., a protective sheet for semiconductor processing is affixed to the circuit surface as described above to temporarily protect the circuit surface from the effects of grinding. Therefore, there are great advantages to affixing a protective sheet for semiconductor processing to the circuit surface when grinding the backside of a semiconductor wafer.

When the semiconductor processing protective sheet 1 is applied to the semiconductor wafer 50, it is applied while applying tension to the semiconductor processing protective sheet 1 (stretching the semiconductor processing protective sheet 1). As a result, residual stress RS occurs in the applied semiconductor processing protective sheet 1. The substrate is usually more rigid than the components other than the substrate and resists tension, so residual stress occurs mainly in the substrate.

In other words, after the semiconductor processing protective sheet is applied to the semiconductor wafer, in addition to the residual stress generated in the semiconductor wafer, residual stress also occurs in the substrate of the semiconductor processing protective sheet. The residual stress generated in the substrate is canceled out by the rigidity of the semiconductor wafer, just like the residual stress generated in the semiconductor wafer.

However, after grinding a semiconductor wafer to which a conventional semiconductor processing protective sheet 100 has been applied and in which residual stress has occurred, both the residual stress generated in the substrate and the residual stress generated in the semiconductor wafer become apparent, as shown in Figure 3B, and the warp Wb generated in the semiconductor wafer 50 becomes larger than the warp Wa shown in Figure 3A.

If the warpage of the semiconductor wafer 50 is large, it affects the handleability of the semiconductor wafer during transportation. Therefore, the warpage Wb shown in FIG. 3B is a composite warpage of the warpage caused by the residual stress generated in the semiconductor wafer and the warpage caused by the residual stress generated in the base material, and is therefore highly likely to affect the handleability of the semiconductor wafer. In other words, if the warpage that does not affect the handleability of the semiconductor wafer is W, then Wb>W.

Since the semiconductor processing protective sheet 1 according to this embodiment has the characteristics described below, the semiconductor wafer 50 to which the semiconductor processing protective sheet 1 is attached can enjoy the above-mentioned advantages of attaching the semiconductor processing protective sheet, and even if the thickness is reduced by grinding, the composite warpage Wc can be reduced to a level that does not affect the handleability of the semiconductor wafer, as shown in Figure 3C. In other words, if the warpage that does not affect the handleability of the semiconductor wafer is W, then Wc<W.

Preferably, by eliminating the residual stress generated in the substrate and further eliminating a portion of the residual stress generated in the semiconductor wafer, the semiconductor wafer 50 to which the protective sheet for semiconductor processing 1 is attached enjoys the above-mentioned advantages of attaching the protective sheet for semiconductor processing, while the warpage of the semiconductor wafer is reduced compared to the warpage Wa when the protective sheet for semiconductor processing is not attached, as shown in FIG. 3D. In other words, Wd<Wa. The components of the protective sheet for semiconductor processing 1 are described in detail below.

(2. Substrate)
The substrate is not limited as long as it is made of a material capable of supporting a semiconductor wafer. For example, various resin films used as substrates for backgrinding tapes are exemplified. The substrate may be made of a single-layer film made of one resin film, or may be made of a multi-layer film made of a plurality of resin films laminated together.

(2.1 Physical properties of the substrate)
In this embodiment, it is preferable that the rigidity of the substrate is equal to or less than a predetermined value. If the rigidity of the substrate is too high, the residual stress generated in the substrate cannot be fully alleviated in the intermediate layer described later, and the residual stress of the intermediate layer tends to exceed the above-mentioned range. As a result, in addition to the warp caused by the residual stress generated in the semiconductor wafer itself, the warp caused by the residual stress of the intermediate layer occurs. Therefore, problems such as the semiconductor wafer being easily damaged and the handling property of the semiconductor wafer being deteriorated during transportation occur.

In this embodiment, the rigidity of the substrate is evaluated by the product of the tensile storage modulus of the substrate and the thickness of the substrate. The product of the tensile storage modulus of the substrate and the thickness of the substrate is 8.0×10 ⁵ N/m or less. More preferably, the product of the tensile storage modulus of the substrate and the thickness of the substrate is 7.5×10 ⁵ N/m or less.

On the other hand, the product of the tensile storage modulus of the substrate and the thickness of the substrate is preferably 5.0 × 10 ³ N/m or more, and more preferably 1.2 × 10 ⁵ N/m or more. When the rigidity of the substrate is equal to or greater than a predetermined value, the residual stress of the substrate can be eliminated by the intermediate layer, while warping caused by the residual stress generated in the semiconductor wafer can be suppressed by the rigidity of the substrate.

In other words, by controlling the stress relaxation ability of the intermediate layer and the stress resistance ability exerted by the rigidity of the base material, warping of the semiconductor wafer after back grinding can be suppressed even if residual stress occurs in the semiconductor wafer.

The preferred range for the thickness of the substrate varies depending on the tensile storage modulus of the substrate, but in this embodiment, it is preferable for the thickness to be 15 μm or more and 200 μm or less, and more preferably 40 μm or more and 150 μm or less.

(2.2 Substrate material)
The material of the substrate is preferably a material in which the product of the tensile storage modulus of the substrate and the thickness of the substrate falls within the above range when the thickness of the substrate falls within the above range. In this embodiment, for example, polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, wholly aromatic polyester, polyamide, polycarbonate, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, biaxially oriented polypropylene, etc. are included. Among these, polyesters are preferred, and polyethylene terephthalate is more preferred.

(3. Middle Class)
The intermediate layer is a layer disposed between the substrate and the adhesive layer. In this embodiment, the intermediate layer is a layer having high stress relaxation properties that can take on the residual stress of the substrate and relax the residual stress within the intermediate layer. As shown in FIG. 4, the substrate 10 shrinks due to the residual stress after the semiconductor processing protective sheet 1 is attached, but most of the residual stress is relaxed in the intermediate layer, so that the warpage of the semiconductor wafer 50 is suppressed. The intermediate layer may be composed of one layer (single layer) or may be composed of two or more layers.

The thickness of the intermediate layer 20 is set arbitrarily within a range in which the effects of the present invention can be obtained. In this embodiment, the thickness of the intermediate layer 20 is preferably 50 μm or more and 500 μm or less. The thickness of the intermediate layer means the thickness of the entire intermediate layer. For example, the thickness of an intermediate layer composed of multiple layers means the total thickness of all layers that make up the intermediate layer.

In this embodiment, the intermediate layer has the following physical properties:

(3.1 Residual stress after holding at 65°C for 300 seconds)
In this embodiment, the residual stress of the intermediate layer after being held at 65° C. for 300 seconds is 10,000 Pa or less. The residual stress taken on from the substrate is rapidly relaxed in the intermediate layer and is almost stable after 300 seconds. In addition, the semiconductor processing protection sheet is usually attached to the semiconductor wafer at a temperature of about 65° C.

Therefore, by keeping the stress remaining in the intermediate layer after holding at 65°C for 300 seconds within the above range, the residual stress assumed from the applied substrate is sufficiently alleviated within the intermediate layer. Note that "residual stress in the intermediate layer after holding at 65°C for 300 seconds" refers to the residual stress in the intermediate layer measured after the temperature of the intermediate layer is maintained at 65°C for 300 seconds.

The residual stress of the intermediate layer after holding at 65°C for 300 seconds is preferably 6000 Pa or less, and more preferably 5000 Pa or less. In addition, the residual stress of the intermediate layer after holding at 65°C for 300 seconds is preferably 1 Pa or more.

In this embodiment, the residual stress of the intermediate layer after holding at 65°C for 300 seconds can be measured as follows. The material constituting the intermediate layer is prepared as a sample of a predetermined size, and the sample at a temperature of 65°C is twisted using a dynamic viscoelasticity measuring device to apply shear strain to the sample. The shear stress is measured 300 seconds after the strain is applied, and the measured shear stress is regarded as the residual stress of the intermediate layer after holding at 65°C for 300 seconds.

(3.2 Loss tangent at 65°C)
In this embodiment, the loss tangent (tan δ) of the intermediate layer at 65° C. is preferably 0.6 or more. The loss tangent is defined as "loss modulus/storage modulus" and is a value measured by the response to stress applied to an object using a dynamic viscoelasticity measuring device. When the loss tangent of the intermediate layer at 65° C. is within the above range, the residual stress taken over from the base material is consumed as heat, thereby suppressing warpage of the semiconductor wafer.

The loss tangent of the intermediate layer at 65°C is preferably 0.8 or more, and more preferably 1.0 or more. Also, the loss tangent of the intermediate layer at 65°C is preferably 3.0 or less.

The loss tangent of the intermediate layer at 65°C may be measured by a known method. For example, the intermediate layer may be used as a sample of a predetermined size, and a dynamic viscoelasticity measuring device may be used to apply strain to the sample at a predetermined frequency within a predetermined temperature range to measure the elastic modulus, from which the loss tangent may be calculated.

(3.3 Composition for intermediate layer)
The composition of the intermediate layer is not particularly limited as long as the intermediate layer has the above-mentioned physical properties. In this embodiment, the intermediate layer is preferably composed of a composition containing a resin (composition for intermediate layer). The intermediate layer composition preferably contains the following components.

(3.3.1 Urethane (meth)acrylate)
Urethane (meth)acrylate is a compound having at least a (meth)acryloyl group and a urethane bond, and has the property of being polymerized by energy ray irradiation. In this embodiment, urethane (meth)acrylate is a component used to impart flexibility to the intermediate layer and to impart the property of reducing residual stress. In this specification, "(meth)acrylate" is used as a term indicating both "acrylate" and "methacrylate", and the same applies to other similar terms.

The urethane (meth)acrylate may be monofunctional or polyfunctional. In this embodiment, polyfunctional urethane (meth)acrylate is preferred, and from the viewpoint of keeping the residual stress of the intermediate layer within the above range, bifunctional urethane (meth)acrylate is preferred.

The urethane (meth)acrylate may be an oligomer, a polymer, or a mixture thereof. In this embodiment, a urethane (meth)acrylate oligomer is preferred.

The urethane (meth)acrylate can be obtained, for example, by reacting a polyol compound with a polyisocyanate compound to obtain a terminal isocyanate urethane prepolymer, and then reacting the resulting prepolymer with a hydroxyl group-containing (meth)acrylate. The urethane (meth)acrylate may be used alone or in combination of two or more kinds.

The content of urethane (meth)acrylate in the intermediate layer composition is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. The content of urethane (meth)acrylate in the intermediate layer composition is preferably 70% by mass or less, more preferably 65% by mass or less, and even more preferably 50% by mass or less.

(3.3.2 Polymerizable monomers)
The polymerizable monomer is preferably a polymerizable compound other than the above-mentioned urethane (meth)acrylate, and is a compound that can be polymerized with other components by irradiation with energy rays. Specifically, the polymerizable monomer is preferably a compound having at least one (meth)acryloyl group.

Examples of polymerizable monomers include (meth)acrylates having an alkyl group having 1 to 30 carbon atoms; (meth)acrylates having functional groups such as hydroxyl groups, amide groups, amino groups, and epoxy groups; (meth)acrylates having an alicyclic structure; (meth)acrylates having an aromatic structure; (meth)acrylates having a heterocyclic structure; and vinyl compounds such as styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, and N-vinylcaprolactam.

Examples of (meth)acrylates having an alkyl group having 1 to 30 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, and eicosyl (meth)acrylate.

Examples of (meth)acrylates having functional groups include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, and N-methylol (meth)acrylamide. Examples of the compound include amide group-containing compounds such as acrylamide, N-methylolpropane (meth)acrylamide, N-methoxymethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide; amino group-containing (meth)acrylates such as primary amino group-containing (meth)acrylates, secondary amino group-containing (meth)acrylates, and tertiary amino group-containing (meth)acrylates; and epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

Examples of (meth)acrylates having an alicyclic structure include isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, and adamantane (meth)acrylate.

Examples of (meth)acrylates having an aromatic structure include phenylhydroxypropyl (meth)acrylate, benzyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate.

Examples of (meth)acrylates having a heterocyclic structure include tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate.

In this embodiment, the polymerizable monomer preferably includes a (meth)acrylate having an alkyl group with 1 to 30 carbon atoms and a (meth)acrylate having an alicyclic structure. From the viewpoint of keeping the residual stress of the intermediate layer within the above range, a (meth)acrylate having an alkyl group with 4 to 14 carbon atoms is preferred, and as the (meth)acrylate having an alicyclic structure, isobornyl (meth)acrylate and trimethylcyclohexyl (meth)acrylate are preferred.

When the intermediate layer composition contains a crosslinking agent, a (meth)acrylate having a functional group that can react with the crosslinking agent is not preferred. This is because the crosslinked structure formed by the crosslinking reaction may increase the residual stress in the intermediate layer. For example, an intermediate layer composition containing a polyisocyanate-based crosslinking agent and a (meth)acrylate having a hydroxyl group is not preferred.

The content of the polymerizable monomer in the intermediate layer composition is preferably 20% by mass or more, and more preferably 30% by mass or more. The content of the polymerizable monomer in the intermediate layer composition is preferably 80% by mass or less, and more preferably 70% by mass or less.

In addition, the mass ratio of the urethane (meth)acrylate to the polymerizable monomer (urethane (meth)acrylate/polymerizable monomer) in a total of 100 parts by mass of the urethane (meth)acrylate and the polymerizable monomer is preferably from 20/80 to 80/20, and more preferably from 30/70 to 70/30.

(3.3.3 Photopolymerization initiator)
When the intermediate layer composition contains the above-mentioned urethane (meth)acrylate and polymerizable monomer, the intermediate layer composition preferably contains a photopolymerization initiator. By containing the photopolymerization initiator, polymerization proceeds reliably, and an intermediate layer having the above-mentioned characteristics can be easily obtained.

Examples of photopolymerization initiators include photopolymerization initiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, and photosensitizers such as amines and quinones. Specific examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and 2,2-dimethoxy-1,2-diphenylethane-1-one. These photopolymerization initiators may be used alone or in combination of two or more.

The amount of photopolymerization initiator is preferably 0.05 parts by mass or more and 15 parts by mass or less, and more preferably 0.5 parts by mass or more and 10 parts by mass or less, per 100 parts by mass of the combined total of the urethane (meth)acrylate and the polymerizable monomer.

3.3.4 Chain Transfer Agents
The intermediate layer composition preferably contains a chain transfer agent. The chain transfer agent can cause a chain transfer reaction and adjust the progress of the curing reaction of the intermediate layer composition. By containing the chain transfer agent, it becomes possible for components with short molecular chains to remain relatively even after curing, so that the cured polymer has a structure with relatively high flexibility. As a result, the residual stress applied to the intermediate layer can be sufficiently relaxed, and it becomes easy to set the residual stress of the intermediate layer within the above range.

Examples of chain transfer agents include thiol group-containing compounds. Examples of thiol group-containing compounds include nonyl mercaptan, 1-dodecanethiol, 1,2-ethanedithiol, 1,3-propanedithiol, triazine thiol, triazine dithiol, triazine trithiol, 1,2,3-propane trithiol, tetraethylene glycol bis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetraki ... Examples of the chain transfer agent include thritol tetrakis thioglucarate, dipentaerythritol hexakis (3-mercaptopropionate), tris [(3-mercaptopropionyloxy) -ethyl] -isocyanurate, 1,4-bis (3-mercaptobutyryloxy) butane, pentaerythritol tetrakis (3-mercaptobutyrate), and 1,3,5-tris (3-mercaptobutyloxyethyl) -1,3,5-triazine-2,4,6- (1H,3H,5H) -trione. The chain transfer agent may be used alone or in combination of two or more kinds.

The amount of chain transfer agent is preferably 0.1 parts by mass or more and 10 parts by mass or less, and more preferably 0.3 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the combined total of the urethane (meth)acrylate and the polymerizable monomer.

(4. Pressure-sensitive adhesive layer)
The adhesive layer is attached to the circuit surface of the semiconductor wafer, and protects the circuit surface and supports the semiconductor wafer until it is peeled off from the circuit surface. The adhesive layer may be composed of one layer (single layer), or may be composed of two or more layers. When the adhesive layer has multiple layers, these multiple layers may be the same or different from each other, and the combination of layers constituting these multiple layers is not particularly limited.

The thickness of the adhesive layer is not particularly limited, but is preferably 1 μm or more and 50 μm or less, more preferably 2 μm or more and 30 μm or less. The thickness of the adhesive layer means the thickness of the entire adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers means the total thickness of all layers that make up the adhesive layer.

The composition of the adhesive layer is not limited as long as it has enough adhesiveness to protect the circuit surface of the semiconductor wafer. In this embodiment, the adhesive layer is preferably composed of, for example, an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, or the like.

The adhesive layer is preferably formed from an energy ray curable adhesive. By forming the adhesive layer of the semiconductor processing protective sheet from an energy ray curable adhesive, it adheres to the semiconductor wafer with high adhesive strength when attached to the semiconductor wafer, and when peeled off from the semiconductor wafer, the adhesive strength can be reduced by irradiating with energy rays. Therefore, while appropriately protecting the circuits of the semiconductor wafer, it is possible to prevent the circuits on the semiconductor wafer surface from being destroyed and the adhesive from being transferred onto the semiconductor wafer when the semiconductor processing protective sheet is peeled off.

In this embodiment, the energy ray curable adhesive is preferably composed of an adhesive composition containing an acrylic adhesive. As the acrylic adhesive, it is preferable to use an acrylic polymer.

The acrylic polymer may be any known acrylic polymer, but in this embodiment, a functional group-containing acrylic polymer is preferred. The functional group-containing acrylic polymer may be a homopolymer formed from one type of acrylic monomer, a copolymer formed from multiple types of acrylic monomers, or a copolymer formed from one or multiple types of acrylic monomers and a monomer other than the acrylic monomer.

In this embodiment, the functional group-containing acrylic polymer is preferably an acrylic copolymer obtained by copolymerizing an alkyl (meth)acrylate and a functional group-containing monomer.

Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and n-octyl (meth)acrylate.

The functional group-containing monomer is a monomer that contains a reactive functional group. The reactive functional group is a functional group that can react with other compounds such as a crosslinking agent described below. Examples of the functional group in the functional group-containing monomer include a hydroxyl group, a carboxyl group, and an epoxy group, with a hydroxyl group being preferred.

Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and non-(meth)acrylic unsaturated alcohols (unsaturated alcohols not having a (meth)acryloyl skeleton) such as vinyl alcohol and allyl alcohol.

The adhesive composition preferably further contains an energy ray-curable compound having an energy ray-curable group. The energy ray-curable compound having an energy ray-curable group is preferably a compound having one or more groups selected from an isocyanate group, an epoxy group, and a carboxy group, and more preferably a compound having an isocyanate group.

Examples of compounds having an isocyanate group include 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate; and acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate. The isocyanate group undergoes an addition reaction with the hydroxyl group of the functional group-containing acrylic polymer.

It is preferable that the pressure-sensitive adhesive composition further contains a crosslinking agent. The crosslinking agent reacts, for example, with functional groups to crosslink the resins contained in the functional group-containing acrylic polymer.

Examples of crosslinking agents include isocyanate-based crosslinking agents (crosslinking agents having an isocyanate group) such as tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and adducts of these diisocyanates; epoxy-based crosslinking agents (crosslinking agents having a glycidyl group) such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents (crosslinking agents having an aziridinyl group) such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; metal chelate-based crosslinking agents (crosslinking agents having a metal chelate structure) such as aluminum chelate; and isocyanurate-based crosslinking agents (crosslinking agents having an isocyanuric acid skeleton).

It is preferable that the crosslinking agent be an isocyanate-based crosslinking agent because it improves the cohesive strength of the adhesive and thereby improves the adhesive strength of the adhesive layer, and because it is easy to obtain.

The pressure-sensitive adhesive composition may further contain a photopolymerization initiator. When the pressure-sensitive adhesive composition contains a photopolymerization initiator, the curing reaction proceeds sufficiently even when irradiated with relatively low-energy energy rays such as ultraviolet rays.

Examples of photopolymerization initiators include photoinitiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, and photosensitizers such as amines and quinones. Specific examples include α-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, benzyl dimethyl ketal, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloroanthraquinone, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

(5. Manufacturing method of protective sheet for semiconductor processing)
The method for producing the semiconductor processing protection sheet according to this embodiment is not particularly limited as long as it is a method capable of laminating an intermediate layer and a pressure-sensitive adhesive layer on one side of a substrate, and any known method may be used.

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

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

Then, the intermediate layer composition or the like is applied onto the substrate by a known method such as spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, or gravure coating to form a coating film, and the coating film is cured to form an intermediate layer on the substrate. In this embodiment, the coating film is preferably cured by irradiation with energy rays. Examples of energy rays include ultraviolet rays and electron beams, and ultraviolet rays are preferred.

Furthermore, in this embodiment, it is preferable to irradiate the energy rays multiple times to harden the coating film. In this way, the degree of hardening of the intermediate layer can be controlled, and it becomes easier to keep the residual stress of the intermediate layer within the above range.

Specifically, it is preferable to irradiate the coating film with energy rays multiple times while blocking the film from oxygen.

Furthermore, when the energy rays are ultraviolet rays, the conditions for the first ultraviolet irradiation are that the illuminance of the ultraviolet rays is preferably 30 to 500 mW/cm ² , more preferably 50 to 340 mW/cm ² , and the amount of ultraviolet rays irradiation is preferably 100 to 2500 mJ/cm ² , more preferably 150 to 2000 mJ/cm ² .

It is preferable that the conditions for the second UV irradiation be such that the illuminance and dose are greater than those of the first irradiation.

An adhesive composition or the like is applied by a known method onto the intermediate layer thus cured, and then heated and dried to produce a protective sheet for semiconductor processing in which an intermediate layer and an adhesive layer are formed in that order on the substrate.

Alternatively, a protective sheet for semiconductor processing may be manufactured as follows. That is, an intermediate layer is formed on the release-treated surface of one release sheet by applying an intermediate layer composition or the like to the release-treated surface of the release sheet, and the coating film is cured as described above to form an intermediate layer on the release sheet.

An adhesive composition or the like is applied to the release-treated surface of the other release sheet, and heated and dried to form an adhesive layer on the release sheet. Thereafter, the intermediate layer on one of the release sheets is bonded to the substrate, and the release sheet is removed. Next, the intermediate layer may be bonded to the adhesive layer on the other release sheet to produce a semiconductor processing protective sheet in which the intermediate layer, adhesive layer, and release sheet are provided in this order on the substrate. The release sheet may be peeled off and removed as appropriate before using the semiconductor processing protective sheet.

(6. Manufacturing Method of Semiconductor Device)
A method for manufacturing a semiconductor device using the semiconductor processing protective sheet of this embodiment is not particularly limited, as long as it includes a step of attaching the semiconductor processing protective sheet of this embodiment to a semiconductor wafer in which residual stress has occurred, and a step of reducing the rigidity of the semiconductor wafer to which the semiconductor processing protective sheet is attached.

A preferred process for attaching the semiconductor processing protective sheet of this embodiment to a semiconductor wafer is, for example, attaching the semiconductor processing protective sheet of this embodiment to the surface of the semiconductor wafer on which a circuit is formed.

An example of a process for reducing the rigidity of a semiconductor wafer is a process for grinding the semiconductor wafer to reduce its thickness.

Below, as an example of a method for manufacturing a semiconductor device using the semiconductor processing protective sheet of this embodiment, a method for manufacturing a semiconductor device from a semiconductor wafer in which residual stress has occurred is described with reference to Figures 2 to 4.

First, a semiconductor wafer is prepared. Any known semiconductor wafer may be used. The thickness of the semiconductor wafer before grinding is usually about 500 to 1000 μm. The thickness of the semiconductor wafer after grinding is preferably 100 to 300 μm.

In this embodiment, the semiconductor wafer in which residual stress occurs is a semiconductor wafer in which the circuit protection layer described above is formed. The circuit protection layer is usually formed by applying a composition that constitutes the circuit protection layer and thermally curing it. During thermal curing, the composition shrinks, and a force that tries to bend the semiconductor wafer, i.e., residual stress, acts on the circuit surface side. Therefore, as shown in FIG. 2, in the semiconductor wafer after the circuit protection layer is formed, residual stress RS1 occurs in the circuit protection layer 51. Note that convex electrodes such as bumps and pillar electrodes may be formed on the circuit surface to which the semiconductor processing protection sheet of this embodiment is attached.

Next, before grinding the back surface of the semiconductor wafer, as shown in Figure 2, a semiconductor processing protective sheet 1 is attached to the circuit side surface of the semiconductor wafer 50 on which the circuit protection layer 51 is formed, i.e., the surface 51a of the circuit protection layer 51, to protect the circuit surface from adverse effects caused by grinding. At this time, the semiconductor processing protective sheet 1 is attached to the circuit surface while being pulled. Therefore, after attachment, a residual stress RS2 acting in the direction of contraction of the substrate is generated in the semiconductor processing protective sheet 1, particularly in the highly rigid substrate.

As shown in Figure 4, this residual stress RS2 causes the substrate 10 to shrink and the residual stress generated in the substrate 10 is eliminated, but the deformation of the substrate 10 generates residual stress RS2 in the intermediate layer 20 formed on the substrate. However, in this embodiment, since the intermediate layer has the above-mentioned characteristics, most of the residual stress is alleviated in the intermediate layer and becomes equal to or less than the above-mentioned value. Furthermore, when a convex electrode is formed on the circuit surface, the intermediate layer can alleviate the residual stress while sufficiently conforming to the steps on the circuit surface to protect the convex electrode.

Thereafter, the backside of the semiconductor wafer to which the semiconductor processing protective sheet 1 is attached is ground. When the semiconductor wafer becomes thinner and its rigidity decreases, warping occurs due to residual stress in the semiconductor wafer. When the rigidity of the substrate is low, as shown in FIG. 3C, it is possible to reduce the warping to a level that does not affect the handleability of the semiconductor wafer. When the rigidity of the substrate is high, as shown in FIG. 3D, it is possible to suppress even a portion of the warping caused by residual stress in the semiconductor wafer. This makes it easier to transport to the next process and prevents damage to the semiconductor wafer.

After back grinding, the semiconductor wafer is diced into individual semiconductor chips using a known method. The resulting semiconductor chips are then mounted on a substrate using a specified method to obtain a semiconductor device.

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

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

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

(Residual stress in intermediate layer)
The intermediate layer composition described below was applied to a PET-based release film (manufactured by Lintec Corporation, SP-PET382150, thickness 38 μm) by knife coating to a thickness of 400 μm to form an intermediate layer composition layer. Next, the intermediate layer composition layer thus formed was laminated with a PET-based release film (manufactured by Lintec Corporation, SP-PET381130, thickness 38 μm) to insulate the intermediate layer composition layer from oxygen. Next, ultraviolet light was irradiated using a high-pressure mercury lamp under conditions of an illuminance of 80 mW/cm ² and an exposure dose of 200 mJ/cm ² , and then ultraviolet light was irradiated using a metal halide lamp under conditions of an illuminance of 330 mW/cm ² and an exposure dose of 1260 mJ/cm ² to cure the intermediate layer composition layer, thereby obtaining an intermediate layer having a thickness of 400 μm. This intermediate layer was laminated to prepare a measurement sample having a thickness of about 0.8 mm. Residual stress measurements were performed using a rheometer MCR302 manufactured by Anton Paar. The measurement conditions were as follows: the sample was sandwiched between parallel plates from above and below, and shear stress was applied to the sample at a measurement temperature of 65°C, a gap of 1 mm, and a strain of 100%, and the sample was held for a predetermined time. The shear stress value of the intermediate layer after a relaxation time of 300 seconds was taken as the residual stress value.

(loss tangent of middle layer)
A sample for measuring loss tangent was prepared in the same manner as the sample for measuring residual stress. The loss tangent (tan δ) was measured using a rheometer MCR302 manufactured by Anton Paar. The measurement conditions were as follows. The sample was sandwiched from above and below by parallel plates, and shear stress was applied to the sample under the conditions of a measurement temperature of 0 to 100°C, a gap of 1 mm, a strain of 0.05 to 0.5%, and an angular frequency of 1 Hz, and the loss tangent (tan δ) at 65°C was calculated from these values.

(Wafer warpage evaluation)
Two sheets of LC2850 (thickness 25 μm) manufactured by Lintec Corporation were attached to a 12-inch silicon wafer as a pseudo circuit protection layer, and the wafer was heated at 180° C. for three hours and then slowly cooled to room temperature. This silicon wafer was used as a silicon wafer with a pseudo circuit protection layer formed thereon. A general-purpose backgrind tape was attached to the protection layer side of this silicon wafer with the circuit protection layer formed thereon, and the wafer was ground until the thickness reached 250 μm. After grinding, when the tape was peeled off, it was confirmed that the wafer had warped by approximately 9.0 mm.

The protective sheets for semiconductor processing prepared in the examples and comparative examples were attached to the surface of the pseudo-circuit protective layer of the silicon wafer on which the pseudo-circuit protective layer was formed at 65°C, and the surface opposite to the surface to which the protective sheet for semiconductor processing was attached was ground until the thickness was 250 μm. In other words, the thickness of the silicon wafer after grinding was 200 μm.

The silicon wafer was placed on a flat plate with the semiconductor processing protective sheet attached side (pseudo circuit protective layer side) facing up, and the maximum distance between the back surface of the silicon wafer and the flat plate was measured to evaluate the warpage of the silicon wafer. In this example, the difference from the amount of warpage (9.0 mm) after peeling off the backgrind tape was calculated, and samples with a warpage difference of 5.0 mm or less were judged to be good, and samples with a warpage of more than 5.0 mm were judged to be bad.

Example 1
A composition for an intermediate layer was obtained by blending 65 parts by mass of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.), 25 parts by mass of isobornyl acrylate, and 10 parts by mass of dodecyl acrylate, totaling 100 parts by mass, with 3.4 parts by mass of a photopolymerization initiator (Irgacure 1173, manufactured by BASF Corporation) and 1.0 part by mass of a chain transfer agent (Karenz MT PE1, manufactured by Showa Denko K.K.).

The obtained intermediate layer composition was applied by knife coating onto a PET film (manufactured by Toray Industries, Inc., thickness 75 μm) as a substrate to a thickness of 400 μm to form an intermediate layer composition layer. Next, an intermediate layer composition layer formed by a PET-based release film (manufactured by Lintec Corporation, SP-PET752150, thickness 75 μm) was laminated to insulate the intermediate layer composition layer from oxygen. Next, ultraviolet light was irradiated using a high-pressure mercury lamp under conditions of an illuminance of 80 mW/cm ² and an exposure dose of 200 mJ/cm ² , and then ultraviolet light was irradiated using a metal halide lamp under conditions of an illuminance of 330 mW/cm ² and an exposure dose of 1260 mJ/cm ² to harden the intermediate layer composition layer, thereby forming an intermediate layer having a thickness of 400 μm on the PET film as a substrate.

The tensile storage modulus of the PET film substrate was 4.0×10 ⁹ N/m ^2. Therefore, the product of the tensile storage modulus of the substrate and the thickness of the substrate (75 μm) was 3.0×10 ⁵ (N/m).

Next, 1.1 parts by mass of trimethylolpropane adduct tolylene diisocyanate (Tosoh Corporation, Coronate L) as a crosslinking agent and 2.2 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (BASF Corporation, Irgacure 651) as a photopolymerization initiator were added to 100 parts by mass of acrylic copolymer (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., composition: 2EHA/EA/MMA//HEA-MOI%=60/15/5/20//60%, Mw=800,000), and toluene was further added to adjust the solids concentration to 30%, and the mixture was stirred for 30 minutes to prepare a pressure-sensitive adhesive composition.

Next, the prepared adhesive composition solution was applied to a PET-based release film (SP-PET382150, manufactured by Lintec Corporation, thickness 38 μm) and dried to form an adhesive layer with a thickness of 10 μm, thereby producing an adhesive sheet.

The release film on the substrate having the intermediate layer obtained above was removed, and the intermediate layer was bonded to the adhesive layer of the adhesive sheet to produce a protective sheet for semiconductor processing.

Example 2
A semiconductor processing protective sheet was prepared in the same manner as in Example 1, except that a composition was used as the intermediate layer composition, which was a mixture of 65 parts by mass of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.) and 35 parts by mass of isobornyl acrylate, for a total of 100 parts by mass, with 3.4 parts by mass of a photopolymerization initiator (Irgacure 1173, manufactured by BASF Co., Ltd.) and 1.0 part by mass of a chain transfer agent (Karenz MT PE1, manufactured by Showa Denko K.K.).

Example 3
A semiconductor processing protective sheet was prepared in the same manner as in Example 1, except that a composition was used as the intermediate layer composition, which was a mixture of 65 parts by mass of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.) and 35 parts by mass of isobornyl acrylate, for a total of 100 parts by mass, with 3.4 parts by mass of a photopolymerization initiator (Irgacure 1173, manufactured by BASF Co., Ltd.) and 0.9 parts by mass of a chain transfer agent (Kalends MT PE1, manufactured by Showa Denko K.K.).

Example 4
A semiconductor processing protective sheet was prepared in the same manner as in Example 1, except that a composition was used as the intermediate layer composition, which was a mixture of 65 parts by mass of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.), 25 parts by mass of isobornyl acrylate, and 10 parts by mass of dodecyl acrylate, for a total of 100 parts by mass, and 3.4 parts by mass of a photopolymerization initiator (Irgacure 1173, manufactured by BASF Corporation).

(Examples 5 and 6)
A protective sheet for semiconductor processing was produced in the same manner as in Example 4, except that the thickness of the substrate was set to the thickness shown in Table 1.

(Example 7)
The intermediate layer composition obtained in the same manner as in Example 1 was applied by a knife method onto a PET-based release film (SP-PET382150, thickness 38 μm, manufactured by Lintec Corporation) to a thickness of 400 μm to form an intermediate layer composition layer. Next, the intermediate layer composition layer thus formed was laminated with a PET-based release film (SP-PET381130, thickness 38 μm, manufactured by Lintec Corporation) to insulate the intermediate layer composition layer from oxygen. Next, ultraviolet irradiation was performed using a high-pressure mercury lamp under conditions of an illuminance of 80 mW/cm ² and an exposure dose of 200 mJ/cm ² , and then ultraviolet irradiation was performed using a metal halide lamp under conditions of an illuminance of 330 mW/cm ² and an exposure dose of 1260 mJ/cm ² to cure the intermediate layer composition layer. Further, a PET-based release film (manufactured by Lintec Corporation, SP-PET381130, thickness 38 μm) was peeled off from the intermediate layer, and the surface of the intermediate layer was bonded to a substrate PET film (manufactured by Toray Industries, Inc., thickness 2 μm) to obtain a configuration in which an intermediate layer having a thickness of 400 μm was laminated on the PET film. The subsequent operations were performed in the same manner as in Example 1 to produce a semiconductor processing protection sheet.

(Example 8)
A protective sheet for semiconductor processing was produced in the same manner as in Example 7, except that the intermediate layer composition obtained in the same manner as in Example 4 was used.

(Comparative Example 1)
A semiconductor processing protective sheet was prepared in the same manner as in Example 1, except that a composition was used as the intermediate layer composition, which was a mixture of 65 parts by mass of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.), 25 parts by mass of isobornyl acrylate, and 10 parts by mass of dodecyl acrylate, for a total of 100 parts by mass, and 3.4 parts by mass of a photopolymerization initiator (Irgacure 1173, manufactured by BASF Corporation).

(Comparative Examples 2 and 3)
A protective sheet for semiconductor processing was produced in the same manner as in Comparative Example 1, except that the thickness of the substrate was set to the thickness shown in Table 1.

(Comparative Example 4)
A protective sheet for semiconductor processing was produced in the same manner as in Example 1, except that the thickness of the substrate was set to the thickness shown in Table 1.

The above measurements and evaluations were carried out on the obtained samples (Examples 1 to 8 and Comparative Examples 1 to 4). The results are shown in Table 1.

From Table 1, it was confirmed that when the product of the tensile storage modulus of the substrate and the thickness of the substrate is within the above-mentioned range and the residual stress of the intermediate layer after being held at 65°C for 300 seconds is within the above-mentioned range, warping of the wafer caused by residual stress can be suppressed.

Reference Signs List 1: Semiconductor processing protection sheet 10: Substrate 20: Intermediate layer 30: Adhesive layer 50: Semiconductor wafer 51: Circuit surface protection layer

Claims (2)

A semiconductor processing protection sheet having a substrate, an intermediate layer and a pressure-sensitive adhesive layer on the substrate in this order,
the intermediate layer composition for forming the intermediate layer contains urethane (meth)acrylate,
the product of the tensile storage modulus of the substrate and the thickness of the substrate is 8.0×10 ⁵ N/m or less;
The residual stress of the intermediate layer after being held at 65° C. for 300 seconds is 10,000 Pa or less,
A protective sheet for semiconductor processing, wherein the loss tangent of the intermediate layer at 65°C is 1.0 or more . A step of attaching the protective sheet for semiconductor processing according to claim 1 to a semiconductor wafer having residual stress;
and reducing the rigidity of the semiconductor wafer to which the protective sheet for semiconductor processing is attached.

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