Protective sheet for semiconductor processing and method for manufacturing semiconductor device

Abstract

To provide a protection sheet for semiconductor processing capable of suppressing exuding of a component from a sheet during storage while suppressing warpage of a semiconductor wafer when applied on the semiconductor wafer in which residual stress is generated and a method for manufacturing a semiconductor device using the same.SOLUTION: A protection sheet 1 for semiconductor processing has a base material 10, an intermediate layer 20 and an adhesive layer 30 on the base material 10 in this order. When a shear storage modulus of the intermediate layer 20 at 60°C is G' (60°C) and a shear storage modulus of the intermediate layer 20 at 80°C is G' (80°C), G' (60°C) and G' (80°C) satisfy the following formula. Residual stress RS2 of the intermediate layer 20 after holding at 65°C for 300 seconds is 10000 Pa or less.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] 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 suitably used to suppress warpage of a semiconductor wafer and suppress seepage from the sheet, and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing. [Background technology]

[0002] Various electronic devices are equipped with a large number of semiconductor devices each mounting semiconductor chips obtained by singulating a semiconductor wafer on which a circuit is formed. A circuit protection layer, such as a passivation film for protecting the circuit from the external environment or a passivation film for bump formation, may be formed on the semiconductor wafer on which the circuit is formed. Such a circuit protection layer provides mechanical and chemical protection to the circuit formed on the semiconductor wafer.

[0003] Furthermore, as electronic devices are rapidly becoming smaller and more multifunctional, there is a demand for smaller, thinner, and more dense semiconductor chips. To achieve this, a common method is to form circuits on the front surface of a semiconductor wafer, then grind the back surface of the semiconductor wafer to adjust the thickness of the chip.

[0004] During backgrinding of semiconductor wafers, a protective sheet called backgrind tape is attached to the wafer surface to prevent contamination of the wafer surface during grinding and to hold the semiconductor wafer in place. Although the attachment of such a protective sheet improves grinding quality, the attachment of the protective sheet causes residual stress in the protective sheet.

[0005] The semiconductor wafer before back grinding has high rigidity, so the residual stress is canceled out. However, when the semiconductor wafer is thinned by back grinding, the rigidity of the semiconductor wafer decreases, and the residual stress becomes apparent, causing the semiconductor wafer and the protective sheet to warp.

[0006] Furthermore, in a semiconductor wafer having a circuit protection layer formed thereon, residual stress is generated in the semiconductor wafer during the formation of the circuit protection layer, and therefore, after backside grinding, the residual stress in the protection sheet and the residual stress in the semiconductor wafer tend to cause significant warpage of the semiconductor wafer, which can cause problems such as the semiconductor wafer becoming more susceptible to breakage and making it difficult to transport to the next process.

[0007] To address this problem, for example, Patent Document 1 discloses a surface protection sheet in which high stress relaxation properties are imparted to the substrate in order to suppress warpage of semiconductor wafers. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2016 / 063827 Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Document 1, warpage of a semiconductor wafer is suppressed by imparting stress relaxation properties to a substrate and eliminating residual stress generated in the substrate. However, the protective sheet described in Patent Document 1 cannot eliminate residual stress generated 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 warpage of the semiconductor wafer cannot be suppressed when residual stress is generated in the semiconductor wafer itself.

[0010] To address this issue, the present inventors discovered that semiconductor wafer warpage can be reduced by controlling the residual stress in the highly stress relaxation layer. However, they found that simply controlling the residual stress could result in the problem of components constituting the protective sheet leaking out of the protective sheet.

[0011] Specifically, protective sheets to be applied to semiconductor wafers are typically produced as long sheets, which are wound up and stored as sheet rolls until use. In the sheet rolls, the protective sheets are stacked radially while in contact with each other. Therefore, components constituting the protective sheets may seep out depending on the storage environment, the load applied to the protective sheets, and the like. If the seeped components come into contact with the protective sheet, the protective sheet may become contaminated and unusable, and ultimately the entire sheet roll may become unusable.

[0012] The present invention has been made in view of the above circumstances, and aims 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 while suppressing the seepage of components from the sheet during storage, and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing. [Means for solving the problem]

[0013] The aspects of the present invention are as follows. [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, When the shear storage modulus of the intermediate layer at 60°C is G'(60°C) and the shear storage modulus of the intermediate layer at 80°C is G'(80°C), G'(60°C) and G'(80°C) satisfy the following formula: This is a protective sheet for semiconductor processing, in which the residual stress of the intermediate layer after being held at 65°C for 300 seconds is 10,000 Pa or less.

number

[0014] [4] A step of attaching the stored protective sheet for semiconductor processing according to any one of [1] to [3] 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. [Effects of the Invention]

[0015] 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 while suppressing the seepage of components from the sheet during storage, and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a protective sheet for semiconductor processing according to this embodiment. [Figure 2] FIG. 2 is a 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. [Figure 3A] FIG. 3A is a cross-sectional view showing a semiconductor wafer after backside grinding, to which no protective sheet for semiconductor processing has been attached. [Figure 3B] FIG. 3B is a cross-sectional view showing a semiconductor wafer with a conventional protective sheet for semiconductor processing attached thereto after backside grinding. [Figure 3C] FIG. 3C is a 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. [Figure 3D] FIG. 3D is a 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. [Figure 4] FIG. 4 is a perspective schematic diagram of an example of a sheet roll in which the protective sheet for semiconductor processing according to this embodiment is wound up. [Figure 5]FIG. 5 is a cross-sectional view illustrating that the residual stress of the intermediate layer is low in the protective sheet for semiconductor processing according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail below based on specific embodiments with reference to the accompanying drawings. First, the main terms used in this specification will be explained.

[0018] Wafer singulation refers to dividing the wafer into individual circuits to obtain chips.

[0019] The "front surface" of a wafer refers to the surface on which circuits, electrodes, etc. are formed, and the "back surface" of a wafer refers to the surface on which no circuits, etc. are formed. The electrodes may be convex electrodes such as bumps.

[0020] The term "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and similar terms.

[0021] "Energy rays" refers to ultraviolet rays, electron beams, etc., and is preferably ultraviolet rays.

[0022] Unless otherwise specified, the "weight average molecular weight" is a polystyrene equivalent value measured by gel permeation chromatography (GPC). Measurements by this method are performed, for example, using a high-speed GPC device "HLC-8120GPC" manufactured by Tosoh Corporation, with a high-speed column "TSK guard column H" XL -H", "TSK Gel GMH XL ", "TSK Gel G2000 H XL (All products of Tosoh Corporation) connected in this order are used, and the column temperature is 40°C, the liquid flow rate is 1.0 mL / min, and the detector is a differential refractometer.

[0023] The release sheet is a sheet that supports the pressure-sensitive adhesive layer or the protective film-forming film in a releasable manner. The term "sheet" is not limited to a specific thickness, and is used to include a film.

[0024] The mass ratios in the descriptions of compositions such as intermediate layer compositions are based on the active ingredients (solid content), and do not include the solvent unless otherwise specified.

[0025] (1. Protective sheet for semiconductor processing) As shown in Fig. 1, the protective sheet for semiconductor processing 1 according to this embodiment has a configuration in which an intermediate layer 20 and a pressure-sensitive adhesive layer 30 are laminated in this order on a substrate 10. The protective sheet for semiconductor processing is not limited to the configuration shown in Fig. 1 and may have other layers as long as the effects of the present invention are obtained. For example, a release sheet may be disposed on the main surface 30a of the pressure-sensitive adhesive layer 30 to protect the pressure-sensitive adhesive layer 30 until it is attached to the adherend.

[0026] The semiconductor processing protective sheet according to this embodiment is suitable for use on semiconductor wafers that have residual stress before the application of the semiconductor processing protective sheet, such as semiconductor wafers on which circuit protection layers such as various passivation films are formed.

[0027] As shown in Figure 2, the protective sheet for semiconductor processing 1 of this embodiment is used by attaching the main surface 30a of the adhesive layer 30 to the circuit protection layer 51 formed on the circuit surface 50a of the semiconductor wafer 50.

[0028] In a semiconductor wafer 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 backside grinding is high, this residual stress is canceled out by the rigidity of the semiconductor wafer itself.

[0029] However, after grinding, the thickness of the semiconductor wafer decreases, and the rigidity of the semiconductor wafer decreases. Therefore, when the semiconductor wafer is ground without a protective sheet for semiconductor processing attached, warpage Wa occurs due only to the residual stress generated in the semiconductor wafer, as shown in Figure 3A.

[0030] In backgrinding of semiconductor wafers, a protective sheet for semiconductor processing is attached to the circuit surface as described above to temporarily protect the circuit surface from the effects of grinding in order to ensure uniformity of grinding and prevent contamination of the circuit surface by grinding debris, etc. Therefore, there are great advantages to attaching a protective sheet for semiconductor processing to the circuit surface when grinding the backside of a semiconductor wafer.

[0031] When the protective sheet for semiconductor processing 1 is attached to the semiconductor wafer 50, tension is applied to the protective sheet for semiconductor processing 1 (the protective sheet for semiconductor processing 1 is stretched). As a result, residual stress RS occurs in the attached protective sheet for semiconductor processing 1. In a protective sheet for semiconductor processing, the substrate is usually more rigid than the components other than the substrate and resists tension. Therefore, residual stress occurs mainly in the substrate.

[0032] That is, after the semiconductor wafer is attached with the protective sheet for semiconductor processing, in addition to the residual stress generated in the semiconductor wafer, residual stress also occurs in the substrate of the protective sheet for semiconductor processing. 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.

[0033] However, after grinding a semiconductor wafer to which a conventional protective sheet for semiconductor processing 100 has been applied and which has generated residual stress, 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 warpage Wb generated in the semiconductor wafer 50 becomes larger than the warpage Wa shown in Figure 3A.

[0034] If the warpage of the semiconductor wafer 50 is large, it will affect 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 therefore is 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.

[0035] Since the protective sheet for semiconductor processing 1 according to this embodiment has the characteristics described below, the semiconductor wafer 50 to which the protective sheet for semiconductor processing 1 is attached can enjoy the above-mentioned advantages of attaching the protective sheet for semiconductor processing, 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である。

[0036] 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 can enjoy the above-mentioned advantages of attaching the protective sheet for semiconductor processing, while reducing the warpage of the semiconductor wafer as compared to the warpage Wa when the protective sheet for semiconductor processing is not attached, as shown in Figure 3D. <Waとなる。

[0037] Therefore, in this embodiment, in order to reduce the warpage of the semiconductor wafer, the physical properties of the intermediate layer are adjusted to a level that does not affect the handling properties of the semiconductor wafer. Details will be described later.

[0038] The protective sheet for semiconductor processing 1 is usually produced as a long sheet whose longitudinal length is very long relative to its transverse length. Since long sheets are difficult to handle during transportation or storage, the long sheet 1 is usually wound into a sheet roll 11 before use, as shown in FIG.

[0039] In a sheet roll, the semiconductor processing protective sheets are stacked in the radial direction of the sheet roll and are in contact with each other along the circumferential direction of the sheet roll. Due to the storage environment of the sheet roll, the load applied to the semiconductor processing protective sheets in the sheet roll, etc., the components contained in the semiconductor processing protective sheets may decompose or otherwise change from their predetermined state, causing them to seep out. In a sheet roll, the widthwise edges of the semiconductor processing protective sheets are exposed to the outside, so any seepage is observed at the edges of the sheet.

[0040] The present inventors have found that components of an intermediate layer whose physical properties are adjusted with an emphasis on reducing the warpage of the semiconductor wafer tend to ooze out. That is, when the physical properties of the intermediate layer are controlled with an emphasis on reducing the warpage of the semiconductor wafer, oozing may occur during storage in a sheet roll. When such oozing occurs, the semiconductor processing protective sheet located near the oozing area is contaminated, making the semiconductor processing protective sheet unusable.

[0041] Therefore, it is necessary to prevent exudation from the protective sheet for semiconductor processing while reducing the warpage of the semiconductor wafer. Since the exudation usually occurs from the intermediate layer, the physical properties of the intermediate layer are adjusted to suppress the exudation. Details will be described later.

[0042] (2. 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 with high stress relaxation properties that can take on the residual stress of the substrate and relax that residual stress within the intermediate layer. As shown in FIG. 5, after the protective sheet for semiconductor processing 1 is attached, the substrate 10 shrinks due to the residual stress, but most of that residual stress is relaxed in the intermediate layer, thereby suppressing warpage of the semiconductor wafer 50. The intermediate layer may be composed of one layer (single layer) or two or more layers.

[0043] The thickness of the intermediate layer 20 is set arbitrarily within a range that achieves the effects of the present invention. 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 refers to the thickness of the entire intermediate layer. For example, the thickness of an intermediate layer composed of multiple layers refers to the total thickness of all the layers that make up the intermediate layer.

[0044] In this embodiment, in order to reduce warpage of the semiconductor wafer and to suppress exudation of components from the protective sheet for semiconductor processing, the intermediate layer has the following physical properties.

[0045] (2.1. Slope of shear storage modulus with respect to temperature change) In this embodiment, when the shear storage modulus of the intermediate layer at 60°C is G'(60°C) and the shear storage modulus of the intermediate layer at 80°C is G'(80°C), G'(60°C) and G'(80°C) satisfy the following formula: The shear storage modulus (G') is an index of the ease of deformation (hardness) of the intermediate layer.

number

[0046] The left side of the above equation represents the rate of change in the common logarithm of the shear storage modulus (G') when the temperature changes from 60°C to 80°C. In other words, the left side of the above equation represents the slope of the shear storage modulus (G') when the temperature changes from 60°C to 80°C.

[0047] Therefore, the above equation indicates that when the temperature of the intermediate layer changes from 60°C to 80°C, the shear storage modulus (G') of the intermediate layer decreases, and it is preferable that the decrease be relatively small.

[0048] By ensuring that the slope of the shear storage modulus (G') is within the above range, the hardness of the intermediate layer falls within an appropriate range, making it possible to suppress exudation of the components of the intermediate layer.

[0049] The slope of the shear storage modulus (G') is preferably -0.02 or more, more preferably -0.015 or more, while the upper limit of the slope of the shear storage modulus (G') may be within a range that can suppress exudation of the components of the intermediate layer, for example, -0.005.

[0050] The shear storage modulus G'(65°C) of the intermediate layer at 65°C is preferably in the range of 0.01 to 0.1 Pa.

[0051] The shear storage modulus (G') can be measured by a known method. For example, the intermediate layer can be used as a sample of a predetermined size, and the sample can be strained at a predetermined frequency within a predetermined temperature range using a dynamic viscoelasticity measuring device to measure the modulus, and the shear storage modulus can be calculated from the measured modulus.

[0052] (2.2 Residual stress after holding at 65°C for 300 seconds) In this embodiment, the residual stress of the intermediate layer after holding at 65°C for 300 seconds is 10,000 Pa or less. The residual stress assumed by the substrate is rapidly relaxed within the intermediate layer and becomes almost stable after 300 seconds. Furthermore, the protective sheet for semiconductor processing is usually attached to the semiconductor wafer at a temperature of around 65°C.

[0053] Therefore, by keeping the stress remaining in the intermediate layer within the above range after 300 seconds at 65°C, the residual stress assumed by the attached substrate is sufficiently alleviated within the intermediate layer. Note that "residual stress in the intermediate layer after 300 seconds at 65°C" 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.

[0054] The residual stress of the intermediate layer after being held at 65°C for 300 seconds is preferably 6000 Pa or less, and more preferably 5000 Pa or less. Furthermore, the residual stress of the intermediate layer after being held at 65°C for 300 seconds is preferably 1 Pa or more, and more preferably 50 Pa or more.

[0055] In this embodiment, the residual stress of the intermediate layer after being held 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 is twisted at 65°C using a dynamic viscoelasticity measuring device to apply shear strain to the sample. The shear stress 300 seconds after the strain is applied is measured, and the measured shear stress is taken as the residual stress of the intermediate layer after being held at 65°C for 300 seconds.

[0056] (2.3 Loss tangent at 65℃) In this embodiment, the loss tangent (tan δ) of the intermediate layer at 65°C is preferably 0.6 or greater. The loss tangent is defined as "loss modulus / storage modulus" and is a value measured by a dynamic viscoelasticity measuring device based on the response to stress applied to an object. When the loss tangent of the intermediate layer at 65°C is within the above range, the residual stress received from the substrate is consumed as heat, thereby suppressing warpage of the semiconductor wafer.

[0057] The loss tangent of the intermediate layer at 65° C. is more preferably 0.8 or more, even more preferably 0.9 or more, and particularly preferably 1.0 or more. The loss tangent of the intermediate layer at 65° C. is preferably 3.0 or less.

[0058] The loss tangent of the intermediate layer at 65°C may be measured by a known method. For example, the intermediate layer is used as a sample of a predetermined size, and the elastic modulus is measured by applying strain to the sample at a predetermined frequency within a predetermined temperature range using a dynamic viscoelasticity measuring device, and the loss tangent at 65°C can be calculated from the measured elastic modulus.

[0059] (2.3 Composition for intermediate layer) The composition of the intermediate layer is not particularly limited as long as it has the above-mentioned physical properties, but in this embodiment, the intermediate layer is preferably composed of a composition containing a resin (intermediate layer composition). The intermediate layer composition preferably contains the components shown below.

[0060] (2.3.1 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, the urethane (meth)acrylate is a component used to impart flexibility to the intermediate layer and to impart properties of reducing residual stress.

[0061] 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.

[0062] The urethane (meth)acrylate may be an oligomer, a polymer, or a mixture thereof. In this embodiment, a urethane (meth)acrylate oligomer is preferred.

[0063] The urethane (meth)acrylate can be obtained, for example, by reacting a polyol compound with a polyvalent isocyanate compound to obtain a terminal isocyanate urethane prepolymer, and then reacting the resulting prepolymer with a (meth)acrylate having a hydroxyl group. The urethane (meth)acrylate may be used alone or in combination of two or more.

[0064] The content of the 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, and is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 50% by mass or less.

[0065] (2.3.2 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. In this embodiment, the polymerizable monomer is a compound having one reactive unsaturated double bond group.

[0066] Examples of the polymerizable monomer include (meth)acrylates having an alkyl group having 1 to 30 carbon atoms; (meth)acrylates having a functional group such as a hydroxyl group, an amide group, an amino group, or an epoxy group; (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.

[0067] 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.

[0068] Examples of the (meth)acrylate having a functional group 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 amide group-containing compounds include 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.

[0069] 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.

[0070] Examples of the (meth)acrylate having an aromatic structure include phenylhydroxypropyl (meth)acrylate, benzyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate.

[0071] Examples of the (meth)acrylate having a heterocyclic structure include tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate.

[0072] 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.

[0073] When a crosslinking agent is contained in the composition for the intermediate layer, 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, a composition for the intermediate layer containing a polyisocyanate-based crosslinking agent and a (meth)acrylate having a hydroxyl group is not preferred.

[0074] The content of the polymerizable monomer in the intermediate layer composition is preferably 20% by mass or more, more preferably 30% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less.

[0075] Furthermore, 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 20 / 80 to 80 / 20, and more preferably 30 / 70 to 70 / 30.

[0076] (2.3.3 Photoinitiators) When the intermediate layer composition contains the above-mentioned urethane (meth)acrylate and polymerizable monomer, it is preferable that the intermediate layer composition contains a photopolymerization initiator. By including the photopolymerization initiator, polymerization proceeds reliably, and an intermediate layer having the above-mentioned properties can be easily obtained.

[0077] Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, as well as 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-diphenylethan-1-one. These photopolymerization initiators may be used alone or in combination of two or more.

[0078] The amount of the photopolymerization initiator to be blended is preferably 0.05 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the total of the urethane (meth)acrylate and the polymerizable monomer.

[0079] 2.3.4 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 a chain transfer agent, components with short molecular chains can relatively remain even after curing, so that the cured polymer has a crosslinked structure with relatively high flexibility. As a result, the residual stress applied to the intermediate layer can be sufficiently alleviated, making it easy to keep the residual stress of the intermediate layer within the above range.

[0080] Examples of the chain transfer agent include thiol group-containing compounds, such as 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 tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), and tetraethylene glycol bis(3-mercaptopropionate). Examples of the chain transfer agent include erythritol tetrakisthioglucarate, 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. One or more types of chain transfer agents may be used in combination.

[0081] The amount of the chain transfer agent is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, per 100 parts by mass of the total of the urethane (meth)acrylate and the polymerizable monomer.

[0082] (2.3.5. Multifunctional acrylates) The intermediate layer composition preferably contains a polyfunctional acrylate. The polyfunctional acrylate is a compound having two or more (meth)acryloyl groups. The inclusion of the polyfunctional acrylate in the intermediate layer composition can reinforce the three-dimensional network structure (crosslinked structure) formed by polymerization of the urethane (meth)acrylate and the polymerizable monomer upon energy beam irradiation. As a result, it is possible to suppress the exudation of intermediate layer components from the semiconductor processing protective sheet.

[0083] Note that there is some overlap between the definition of a polyfunctional acrylate and that of a urethane (meth)acrylate. The overlapping portion with the urethane (meth)acrylate is included in the urethane (meth)acrylate. For example, a polyfunctional urethane (meth)acrylate contains two or more (meth)acryloyl groups, but is included in the urethane (meth)acrylate.

[0084] In this embodiment, the number of (meth)acryloyl groups in the polyfunctional acrylate is preferably 2 to 20, and more preferably 2 to 8.

[0085] Examples of polyfunctional acrylates include diethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Among these, diethylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are preferred. The polyfunctional acrylates may be used alone or in combination of two or more.

[0086] The amount of the polyfunctional acrylate to be blended is preferably 0.01 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the total of the urethane (meth)acrylate and the polymerizable monomer.

[0087] In this embodiment, when the chain transfer agent is a thiol group-containing compound, the ratio of the number of thiol groups contained in the chain transfer agent to the number of (meth)acryloyl groups contained in the polyfunctional acrylate is preferably within the range of 8: 1 to 1: 1. When the ratio of the number of thiol groups to the number of (meth)acryloyl groups is within the above range, it becomes easy to keep the residual stress after 300 seconds of the intermediate layer and the slope of the shear storage modulus (G') of the intermediate layer within the above ranges.

[0088] (3. Base material) The substrate is not limited as long as it is made of a material that can support 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 in which multiple resin films are laminated.

[0089] (3.1 Physical properties of the substrate) In this embodiment, the physical properties of the substrate are adjusted within a range that achieves the effects of the present invention. 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 intermediate layer cannot fully relieve the residual stress generated in the substrate, and the residual stress in the intermediate layer tends to exceed the above-mentioned range. As a result, in addition to the warpage caused by the residual stress generated in the semiconductor wafer itself, warpage caused by the residual stress in the intermediate layer occurs. Therefore, problems such as the semiconductor wafer becoming more susceptible to breakage and the handling of the semiconductor wafer during transportation becoming worse.

[0090] 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 The product of the tensile storage modulus of the substrate and the thickness of the substrate is preferably 7.5×10 5 It is more preferable that the resistance is N / m or less.

[0091] On the other hand, the product of the tensile storage modulus of the substrate and the thickness of the substrate is 5.0 × 10 3N / m or more is preferable, and 1.2×10 5 When the rigidity of the substrate is equal to or greater than a predetermined value, the residual stress in the substrate can be eliminated by the intermediate layer, and warpage caused by the residual stress generated in the semiconductor wafer can be suppressed by the rigidity of the substrate.

[0092] 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, it is possible to suppress warping of the semiconductor wafer after backside grinding, even if residual stress occurs in the semiconductor wafer.

[0093] The preferred thickness range of the substrate varies depending on the tensile storage modulus of the substrate, but in this embodiment, it is preferably 15 μm or more and 200 μm or less, and more preferably 40 μm or more and 150 μm or less.

[0094] (3.2 Substrate material) The material of the substrate is preferably a material such that, when the thickness of the substrate is within the above range, the product of the tensile storage modulus of the substrate and the thickness of the substrate is within the above range. In this embodiment, examples include 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. Among these, polyester is preferred, and polyethylene terephthalate is more preferred.

[0095] (4. Adhesive Layer) The adhesive layer is attached to the circuit surface of a 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, and the combination of layers constituting these multiple layers is not particularly limited.

[0096] The thickness of the pressure-sensitive 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 pressure-sensitive adhesive layer refers to the thickness of the entire pressure-sensitive adhesive layer. For example, the thickness of a pressure-sensitive adhesive layer composed of multiple layers refers to the total thickness of all layers constituting the pressure-sensitive adhesive layer.

[0097] The composition of the adhesive layer is not limited as long as it has adhesiveness sufficient 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.

[0098] Furthermore, the adhesive layer is preferably formed from an energy ray-curable adhesive. By forming the adhesive layer of the protective sheet for semiconductor processing from an energy ray-curable adhesive, the sheet adheres to the semiconductor wafer with high adhesive strength when attached to the semiconductor wafer, and the adhesive strength can be reduced by irradiating with energy rays when peeled from the semiconductor wafer. Therefore, while appropriately protecting the circuits of the semiconductor wafer, the circuit on the surface of the semiconductor wafer is prevented from being damaged and the adhesive is prevented from being transferred onto the semiconductor wafer when the protective sheet for semiconductor processing is peeled off.

[0099] In this embodiment, the energy ray-curable adhesive is preferably composed of an adhesive composition containing an acrylic adhesive, and the acrylic adhesive is preferably an acrylic polymer.

[0100] 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.

[0101] In this embodiment, the functional group-containing acrylic polymer is preferably an acrylic copolymer obtained by copolymerizing alkyl (meth)acrylate and a functional group-containing monomer.

[0102] 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.

[0103] The functional group-containing monomer is a monomer containing a reactive functional group. The reactive functional group is a functional group capable of reacting with other compounds such as a crosslinking agent, which will be described later. 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.

[0104] 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.

[0105] The pressure-sensitive 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.

[0106] 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.

[0107] The pressure-sensitive adhesive composition preferably further contains a crosslinking agent, which reacts with functional groups to crosslink resins contained in the functional group-containing acrylic polymer, for example.

[0108] 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).

[0109] The crosslinking agent is preferably an isocyanate-based crosslinking agent, from the viewpoint of improving the cohesive strength of the pressure-sensitive adhesive and thereby improving the adhesive strength of the pressure-sensitive adhesive layer, and from the viewpoint of easy availability.

[0110] 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.

[0111] Examples of the photopolymerization initiator 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, benzil dimethyl ketal, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloroanthraquinone, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0112] (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 that can laminate an intermediate layer and a pressure-sensitive adhesive layer on one side of a substrate, and any known method may be used.

[0113] First, as a composition for forming an intermediate layer, for example, a composition for intermediate layer containing the above-mentioned components, or a composition obtained by diluting the composition for intermediate layer with a solvent or the like (hereinafter, these two compositions are also referred to as an intermediate layer coating agent) is prepared. Similarly, as a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer, for example, a pressure-sensitive adhesive composition containing the above-mentioned components, or a composition obtained by diluting the pressure-sensitive adhesive composition with a solvent or the like (hereinafter, these two compositions are also referred to as a pressure-sensitive adhesive layer coating agent) is prepared.

[0114] 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.

[0115] The intermediate layer coating agent is then applied to 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.

[0116] Furthermore, in this embodiment, it is preferable to cure the coating film by irradiating it with energy rays multiple times, which makes it possible to control the degree of cure of the intermediate layer and to easily control the residual stress of the intermediate layer within the above range.

[0117] Specifically, it is preferable to irradiate the coating film with energy rays multiple times while the coating film is shielded from oxygen.

[0118] When the energy rays are ultraviolet rays, the conditions for the first ultraviolet irradiation are preferably such that the illuminance of the ultraviolet rays is 30 to 500 mW / cm 2 , more preferably 50 to 340 mW / cm 2 The irradiation dose of ultraviolet light is preferably 100 to 2500 mJ / cm 2 , more preferably 150 to 2000 mJ / cm 2 is.

[0119] The second irradiation of ultraviolet light is preferably performed under conditions in which the illuminance and dose are greater than those of the first irradiation.

[0120] A coating agent for the adhesive layer is applied to the intermediate layer thus cured and formed by a known method, 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 this order on the substrate.

[0121] Alternatively, the protective sheet for semiconductor processing may be produced as follows: An intermediate layer coating agent is applied to the release-treated surface of one release sheet, and the coating film formed is cured as described above to form an intermediate layer on the release sheet.

[0122] The adhesive layer coating agent 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.Then, the intermediate layer on one release sheet is bonded to the substrate, and the release sheet is removed.Subsequently, the intermediate layer and the adhesive layer on the other release sheet are bonded 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 can be appropriately peeled off and removed before using the semiconductor processing protective sheet.

[0123] The obtained protective sheet for semiconductor processing is cut on both sides in the width direction to fit the size of the semiconductor wafer to be attached, and while adjusting the size in the width direction, it is wound up by a winding device under a predetermined tension, to form a sheet roll. The protective sheet for semiconductor processing is stored in the sheet roll state until it is used.

[0124] (6. Manufacturing Method of Semiconductor Device) The method for manufacturing a semiconductor device using the semiconductor processing protective sheet of this embodiment is not particularly limited, as long as it includes the steps of attaching a stored semiconductor processing protective sheet of this embodiment to a semiconductor wafer in which residual stress has occurred, and reducing the rigidity of the semiconductor wafer to which the semiconductor processing protective sheet is attached.

[0125] In this embodiment, the manufactured semiconductor processing protective sheet is wound up and stored as a sheet roll for a predetermined period of time. By controlling the physical properties of the intermediate layer within the above range, the exudation of components from the stored semiconductor processing protective sheet is suppressed. Therefore, even when the semiconductor processing protective sheet is in use, exudation does not occur in the sheet roll, and the sheet roll can be used effectively.

[0126] The protective sheet for semiconductor processing unwound from the sheet roll is applied to a semiconductor wafer. As a step of applying the protective sheet for semiconductor processing to a semiconductor wafer, for example, a step of applying the protective sheet for semiconductor processing according to the present embodiment to the surface of the semiconductor wafer on which a circuit is formed is preferable.

[0127] 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.

[0128] As an example of a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing according to this embodiment, a method for manufacturing a semiconductor device from a semiconductor wafer in which residual stress occurs will be described below with reference to FIGS.

[0129] First, a sheet roll containing a wound and stored protective sheet for semiconductor processing is prepared, as shown in Figure 4. As described above, the physical properties of the intermediate layer are controlled, so the occurrence of seepage is suppressed.

[0130] Next, 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.

[0131] In this embodiment, the semiconductor wafer in which residual stress occurs is a semiconductor wafer on which the above-mentioned circuit protection layer is formed. A circuit protection layer is typically formed by applying a composition that constitutes the circuit protection layer and then thermally curing it. During thermal curing, the composition shrinks, causing a force that tends to bend the semiconductor wafer, i.e., residual stress, to act on the circuit surface. Therefore, as shown in FIG. 2, after the circuit protection layer is formed, residual stress RS1 occurs in the circuit protection layer 51 of the semiconductor wafer. Note that convex electrodes such as bumps and pillar electrodes may be formed on the circuit surface to which the semiconductor processing protection sheet according to this embodiment is attached.

[0132] Next, before the backside of the semiconductor wafer is ground, as shown in Figure 2, a protective sheet for semiconductor processing 1 unwound from a sheet roll is applied to the circuit side 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 side from the adverse effects of grinding. At this time, the protective sheet for semiconductor processing 1 is applied to the circuit side while being pulled. Therefore, after application, a residual stress RS2 acts in the direction of shrinkage of the substrate in the protective sheet for semiconductor processing 1, particularly in the highly rigid substrate.

[0133] As shown in Figure 5, this residual stress RS2 causes the substrate 10 to shrink, eliminating the residual stress generated in the substrate 10. However, 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 step on the circuit surface to protect the convex electrode.

[0134] The semiconductor wafer with the semiconductor processing protective sheet 1 attached thereto is then subjected to back grinding. As the semiconductor wafer becomes thinner and its rigidity decreases, warpage occurs due to residual stress in the semiconductor wafer. When the rigidity of the substrate is low, warpage can be reduced to a level that does not affect the handling of the semiconductor wafer, as shown in Figure 3C. When the rigidity of the substrate is high, even some of the warpage caused by residual stress in the semiconductor wafer can be suppressed, as shown in Figure 3D. This facilitates transportation to the next process and prevents damage to the semiconductor wafer.

[0135] After the backside grinding, the semiconductor wafer is divided into individual semiconductor chips by a known method. The obtained semiconductor chips are mounted on a substrate by a predetermined method to obtain a semiconductor device.

[0136] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and may be modified in various ways within the scope of the present invention. [Example]

[0137] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0138] The measurement and evaluation methods in the present examples are as follows.

[0139] (residual stress in the middle layer) As described below, the intermediate layer coating material was applied to a specified film and then cured by ultraviolet irradiation to obtain an intermediate layer approximately 400 μm thick. These intermediate layers were then laminated to prepare a measurement sample approximately 1 mm thick.

[0140] Residual stress measurements were performed using an Anton Paar MCR302 rheometer. 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, a strain of 100%, and an angular frequency of 1 Hz, and the sample was held for a specified time. The shear stress value of the intermediate layer at a relaxation time of 300 seconds was taken as the residual stress value.

[0141] (Shear storage modulus (G') of the middle layer) Samples for shear storage modulus measurements were prepared in the same manner as samples for residual stress measurements. The shear storage modulus (G') was measured using an Anton Paar MCR302 rheometer. 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 0 to 100°C, a gap of 1 mm, a strain of 0.05 to 0.5%, and an angular frequency of 1 Hz. From these values, the shear storage modulus (G') at 60°C and the shear storage modulus (G') at 80°C were calculated.

[0142] (loss tangent of the middle layer) Samples for loss tangent measurement were prepared in the same manner as samples for residual stress measurement. Loss tangent (tanδ) was measured using an Anton Paar MCR302 rheometer. 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 0 to 100°C, a gap of 1 mm, a strain of 0.05 to 0.5%, and an angular frequency of 1 Hz. The loss tangent (tanδ) at 65°C was calculated from these values.

[0143] (Wafer warpage evaluation) Two LC2850 (25 μm thick) pseudo-circuit protection layers manufactured by Lintec Corporation were attached to a 12-inch silicon wafer, which was then heated at 180°C for 3 hours and slowly cooled to room temperature. This silicon wafer was designated as a silicon wafer with a pseudo-circuit protection layer. A general-purpose backgrinding tape was attached to the protection layer side of this silicon wafer with a circuit protection layer, and the wafer was ground to a thickness of 250 μm. After grinding, the backgrinding tape was peeled off, confirming a warp of approximately 9.0 mm. Specifically, the warp (Wa) due to residual stress in the semiconductor wafer, as shown in Figure 3A, was approximately 9.0 mm.

[0144] 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 reached 250 μm. That is, the thickness of the silicon wafer after grinding was 200 μm.

[0145] The silicon wafer was placed on a flat plate with the surface to which the protective sheet for semiconductor processing (the surface of the pseudo-circuit protective layer) was attached 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 other words, this warpage 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 of the protective sheet for semiconductor processing. In this example, the difference between the composite warpage and the warpage (9.0 mm) caused only by the residual stress generated in the semiconductor wafer was calculated, and samples with a warpage difference of 5.0 mm or less were judged to be "OK," and samples with a warpage difference of more than 5.0 mm were judged to be "NG."

[0146] (Evaluation of seepage from protective sheets for semiconductor processing) The semiconductor processing protective sheets prepared in the examples and comparative examples were cut to a width of 330 mm using a cutter, and the cut semiconductor processing protective sheets were wound into rolls around a 3-inch diameter plastic core using core fixing tape to obtain semiconductor processing protective sheet rolls. The obtained semiconductor processing protective sheet rolls were stored at 40°C for 72 hours, and after storage, the presence or absence of oozing from the edges of the semiconductor processing protective sheet was evaluated. Samples that did not ooze were judged "OK," and samples that ooze were judged "NG."

[0147] Example 1 A coating agent for the intermediate layer was obtained by blending 50 parts by weight of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Inc.), 35 parts by weight of isobornyl acrylate, and 15 parts by weight of dodecyl acrylate, for a total of 100 parts by weight, with 3.4 parts by weight of a photopolymerization initiator (Irgacure 1173, manufactured by BASF), 1.0 part by weight of a chain transfer agent (Karenz MT PE1, manufactured by Showa Denko K.K.), and 0.5 parts by weight of a UV-curable resin (A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0148] The obtained intermediate layer coating agent was applied to a substrate PET film (manufactured by Toray Industries, Inc., thickness 75 μm) using a knife to form an intermediate layer composition layer with a thickness of 400 μm. Immediately after coating, the formed intermediate layer composition layer was laminated with a PET-based release film (manufactured by Lintec Corporation, SP-PET752150, thickness 75 μm) to insulate the intermediate layer composition layer from oxygen. Subsequently, a high-pressure mercury lamp was used to apply the coating agent at an illuminance of 80 mW / cm. 2 , irradiation amount 300mJ / cm 2 After ultraviolet irradiation under the conditions of 330 mW / cm using a metal halide lamp, 2 , irradiation amount 1260mJ / cm 2 The intermediate layer composition layer was cured by irradiating it with ultraviolet light under the conditions of the above, thereby forming an intermediate layer having a thickness of 400 μm on the PET film substrate.

[0149] The tensile storage modulus of the PET film substrate is 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).

[0150] Next, 1.5 parts by mass of trimethylolpropane adduct tolylene diisocyanate (Tosoh's Coronate L) as a crosslinking agent and 2.2 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (BASF's Irgacure 651) as a photopolymerization initiator were added to 100 parts by mass of acrylic copolymer (2EHA / HEA-MOI%=80 / 20 / / 80%, Mw=800,000), and toluene was further added to adjust the solids concentration to 30%, followed by stirring for 30 minutes to prepare a coating agent for the adhesive layer.

[0151] Next, the prepared adhesive layer coating agent 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.

[0152] The release film disposed on the substrate having the intermediate layer obtained above was removed, and the intermediate layer and the adhesive layer of the adhesive sheet were bonded together to prepare a protective sheet for semiconductor processing.

[0153] Example 2 A protective sheet for semiconductor processing was produced in the same manner as in Example 1, except that an intermediate layer coating agent was used that was a blend of 50 parts by weight of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.), 35 parts by weight of isobornyl acrylate, and 15 parts by weight of dodecyl acrylate, for a total of 100 parts by weight, 3.4 parts by weight of a photopolymerization initiator (Irgacure 1173, manufactured by BASF), 1.0 part by weight of a chain transfer agent (Karenz MT PE1, manufactured by Showa Denko K.K.), and 1.0 part by weight of a UV-curable resin (A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0154] Example 3 A protective sheet for semiconductor processing was produced in the same manner as in Example 1, except that an intermediate layer coating agent was used that was a blend of 50 parts by weight of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.), 35 parts by weight of isobornyl acrylate, and 15 parts by weight of dodecyl acrylate, for a total of 100 parts by weight, 3.4 parts by weight of a photopolymerization initiator (Irgacure 1173, manufactured by BASF), 1.0 part by weight of a chain transfer agent (Karenz MT PE1, manufactured by Showa Denko K.K.), and 1.5 parts by weight of a UV-curable resin (A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0155] Example 4 A protective sheet for semiconductor processing was produced in the same manner as in Example 1, except that an intermediate layer coating agent was used that was a blend of 50 parts by weight of urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.), 35 parts by weight of isobornyl acrylate, and 15 parts by weight of dodecyl acrylate, for a total of 100 parts by weight, 3.4 parts by weight of a photopolymerization initiator (Irgacure 1173, manufactured by BASF), 1.0 part by weight of a chain transfer agent (Karenz MT PE1, manufactured by Showa Denko K.K.), and 0.45 parts by weight of a UV-curable resin (A-DPH-6E, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0156] (Comparative Example 1) A protective sheet for semiconductor processing was prepared in the same manner as in Example 1, except that an intermediate layer coating agent was used that was a blend of 50 parts by weight of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.), 35 parts by weight of isobornyl acrylate, and 15 parts by weight of dodecyl acrylate, for a total of 100 parts by weight, 3.4 parts by weight of a photopolymerization initiator (Irgacure 1173, manufactured by BASF), and 1.0 part by weight of a chain transfer agent (Karenz MT PE1, manufactured by Showa Denko K.K.).

[0157] (Comparative Example 2) A protective sheet for semiconductor processing was produced in the same manner as in Example 1, except that an intermediate layer coating agent was used that was a blend of 50 parts by weight of a urethane acrylate oligomer (CN9021 NS, manufactured by Arkema Co., Ltd.), 35 parts by weight of isobornyl acrylate, and 15 parts by weight of dodecyl acrylate, for a total of 100 parts by weight, 3.4 parts by weight of a photopolymerization initiator (Irgacure 1173, manufactured by BASF), 1.0 part by weight of a chain transfer agent (Karenz MT PE1, manufactured by Showa Denko K.K.), and 3.0 parts by weight of a UV-curable resin (A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0158] The above measurements and evaluations were carried out on the obtained samples (Examples 1 to 4 and Comparative Examples 1 and 2). The results are shown in Table 1.

[0159] [Table 1]

[0160] From Table 1, it was confirmed that when the slope of the shear storage modulus (G') when changing from 60°C to 80°C is within the above-mentioned range and the residual stress of the intermediate layer after holding at 65°C for 300 seconds is within the above-mentioned range, it is possible to suppress both the warping of the wafer in which residual stress has occurred and the seepage of components from the semiconductor processing protective sheet. [Explanation of symbols]

[0161] 1...Protective sheet for semiconductor processing 10...Base material 20...Middle class 30...Adhesive layer 50...Semiconductor wafer 51...Circuit surface protection layer

Claims

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, an intermediate layer composition for forming the intermediate layer containing a urethane (meth)acrylate, a polymerizable monomer, and a polyfunctional acrylate; When the shear storage modulus of the intermediate layer at 60°C is G'(60°C) and the shear storage modulus of the intermediate layer at 80°C is G'(80°C), G'(60°C) and G'(80°C) satisfy the following formula: A protective sheet for semiconductor processing, wherein the residual stress of the intermediate layer after being held at 65°C for 300 seconds is 10,000 Pa or less. [Equation 1]

2. A protective sheet for semiconductor processing, comprising a substrate, an intermediate layer and an adhesive layer on the substrate in this order, When the shear storage modulus of the intermediate layer at 60°C is G'(60°C) and the shear storage modulus of the intermediate layer at 80°C is G'(80°C), G'(60°C) and G'(80°C) satisfy the following formula: the residual stress of the intermediate layer after being held at 65°C for 300 seconds is 1370 Pa or more and 10000 Pa or less, A semiconductor processing protection sheet used on semiconductor wafers with a circuit protection layer formed on them. [Equation 2]

3. The product of the tensile storage modulus of the substrate and the thickness of the substrate is 8.0 × 10 5 3. The protective sheet for semiconductor processing according to claim 1, wherein the hardness is 0.01 N / m or less.

4. 4. The protective sheet for semiconductor processing according to claim 1, wherein the loss tangent of the intermediate layer at 65° C. is 0.6 or more.

5. A step of applying the stored protective sheet for semiconductor processing according to any one of claims 1 to 4 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.

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