Protective sheet for semiconductor processing and method for manufacturing semiconductor device

Abstract

The present application provides a kind of semiconductor processing protective sheet, even when the semiconductor wafer with concave-convex is thinned by DBG etc., it can follow the concave-convex of wafer sufficiently and can inhibit the crack of chip after grinding, and can inhibit the residue when peeling off.The semiconductor processing protective sheet is a semiconductor processing protective sheet with substrate, and has intermediate layer and adhesive layer on one major surface of substrate in turn, the intermediate layer and adhesive layer are energy ray curable, the Young's modulus of semiconductor processing protective sheet before energy ray curing at 50 DEG C is 600 MPa or more.

Description

Technical Field

[0001] This invention relates to a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device. In particular, it relates to a protective sheet for semiconductor processing suitable for methods of grinding the back side of a semiconductor wafer with uneven surfaces and using grinding stress or the like to singulate the semiconductor wafer, and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing. Background Technology

[0002] In the process of miniaturization and multifunctionality of various electronic devices, the semiconductor chips used in these devices also require miniaturization and thinning. To achieve chip thinning, the back side of the semiconductor wafer is typically ground to adjust its thickness. Furthermore, to obtain thinner chips, a process called Dicing Before Grinding (DBG) is sometimes used. This process involves creating grooves of a specified depth on the wafer's surface using a dicing tool, followed by grinding from the back side of the wafer. This grinding process then individualizes the wafer into individual chips. DBG can simultaneously perform back-side grinding and wafer individualization, thus enabling efficient manufacturing of thin chips.

[0003] In the past, when performing back-side grinding of semiconductor wafers or manufacturing chips using DBG, adhesive tape known as back-grinding tape was usually attached to the wafer surface to protect the circuitry on the wafer surface or to maintain the semiconductor wafer and semiconductor chip.

[0004] As a backing abrasive used in DBG, an adhesive tape having a substrate and an adhesive layer disposed on one side of the substrate is used. As an example of such an adhesive tape, Patent Documents 1 and 2 disclose an adhesive tape having a substrate with a high Young's modulus, and having a buffer layer disposed on one side of the substrate and an adhesive layer disposed on the other side.

[0005] In recent years, as a variation of the pre-cutting method, a method has been proposed that uses a laser to create a modified region inside the wafer and utilizes the stress from grinding the back side of the wafer to achieve wafer unitization. Hereinafter, this method is sometimes referred to as LDBG (Laser Dicing Before Grinding). In LDBG, the wafer is cut along the crystal direction starting from the modified region, thus reducing chipping compared to pre-cutting methods using a dicing blade. This results in chips with excellent bending strength and facilitates further chip thinning. Furthermore, compared to DBG, which uses a dicing blade to form trenches of a specified depth on the wafer surface, LDBG achieves superior chip yield because there is no area where the wafer is removed by the dicing blade, resulting in a very small kerf width.

[0006] On the other hand, when mounting multi-pin LSI packages for MPUs or gate arrays on printed circuit boards, the flip-chip mounting method has always been used. In this mounting method, a chip with raised electrodes (bumps) made of eutectic solder, high-temperature solder, gold, etc., formed on its connecting pads is used as a semiconductor chip. These bumps are then brought into contact with corresponding terminals on the chip mounting substrate in a so-called face-down manner, and molten and diffused bonding is performed.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2015 / 156389

[0010] Patent Document 2: Japanese Patent Application Publication No. 2015-183008 Summary of the Invention

[0011] The technical problem to be solved by the present invention

[0012] The semiconductor chip used in this mounting method is obtained by monolithically processing a semiconductor wafer with uneven surfaces, such as a semiconductor wafer with convex electrodes. When this uneven semiconductor wafer is polished by DBG, as described above, back-polishing tape is attached to the circuit surface of the semiconductor wafer to protect the circuit surface during polishing and to prevent chip movement after wafer monolithization.

[0013] However, when the back-polishing tapes described in Patent Documents 1 and 2 are attached to the circuit surface of a semiconductor wafer with uneven surfaces and polished using a die-grinding process (DBG), the back-polishing tapes described in Patent Documents 1 and 2 cannot adequately follow the unevenness of the semiconductor wafer. Problems arise such as water seeping into the circuit surface during polishing and chip displacement after wafer unitization. Furthermore, when a soft intermediate layer is incorporated into such a back-polishing tape to accommodate unevenness, although it can follow the unevenness, residue remains on the convex electrodes when the back-polishing tape is peeled off from the semiconductor wafer.

[0014] The present invention was made in view of the above circumstances, and its object is to provide a protective sheet for semiconductor processing that can fully follow the unevenness of the wafer even when thinning a semiconductor chip with unevenness by DBG or the like, suppress the generation of cracks in the chip after grinding, and suppress the generation of residual adhesive during peeling.

[0015] Technical means to solve technical problems

[0016] The present invention is as follows.

[0017] [1] A protective sheet for semiconductor processing, comprising a substrate having an intermediate layer and an adhesive layer sequentially formed on one main surface of the substrate.

[0018] The intermediate layer and adhesive layer are energy-cured.

[0019] The Young's modulus of the protective sheet for semiconductor processing before energy ray curing at 50°C is above 600 MPa.

[0020] [2] The protective sheet for semiconductor processing according to [1] has a buffer layer on another main surface of the substrate.

[0021] [3] The protective sheet for semiconductor processing according to [1] or [2], wherein the Young's modulus of the substrate is 1000 MPa or more.

[0022] [4] A protective sheet for semiconductor processing according to any one of [1] to [3], wherein the thickness of the intermediate layer is 60 μm or more and 250 μm or less.

[0023] [5] The semiconductor processing protective sheet according to any one of [1] to [4], wherein the semiconductor processing protective sheet is attached to the surface of the semiconductor wafer and used in the process of grinding the back side of a semiconductor wafer on which trenches are formed on the surface of the semiconductor wafer and then single-uniting the semiconductor wafer into a semiconductor chip by the grinding.

[0024] [6] A method for manufacturing a semiconductor device, comprising:

[0025] The process of attaching a protective sheet for semiconductor processing as described in any one of [1] to [5] to the surface of a semiconductor wafer with uneven surfaces;

[0026] The process of forming trenches from the surface side of a semiconductor wafer, or the process of forming modified regions inside a semiconductor wafer from the surface or back side of a semiconductor wafer;

[0027] A process of grinding semiconductor wafers with a protective film for semiconductor processing attached to their surface and with trenches or modified regions formed therein, starting from the back side, to single-chip out multiple wafers from the trenches or modified regions; and

[0028] The process of removing a protective film for semiconductor processing from a single semiconductor chip.

[0029] Invention Effects

[0030] According to the present invention, a protective sheet for semiconductor processing can be provided that can fully follow the unevenness of the wafer even when thinning the semiconductor wafer with unevenness by DBG or the like, suppress the generation of chip cracks after grinding, and suppress the generation of residual adhesive during peeling. Attached Figure Description

[0031] Figure 1A This is a cross-sectional schematic diagram illustrating an example of a protective sheet for semiconductor processing according to this embodiment.

[0032] Figure 1B This is a cross-sectional schematic diagram illustrating another example of the semiconductor processing protective sheet of this embodiment.

[0033] Figure 2 This is a cross-sectional schematic diagram showing the state in which the protective sheet for semiconductor processing of this embodiment is attached to the circuit surface of a semiconductor wafer.

[0034] Explanation of reference numerals in the attached figures

[0035] 1: Protective film for semiconductor processing; 10: Substrate; 20: Intermediate layer; 30: Adhesive layer; 40: Buffer layer. Detailed Implementation

[0036] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, based on specific embodiments. First, the main terms used in this specification will be explained.

[0037] Semiconductor wafer modularization refers to dividing a semiconductor wafer into individual circuits to obtain a semiconductor chip.

[0038] The "surface" of a semiconductor wafer refers to the side where circuits, electrodes, etc. are formed, while the "back side" refers to the side where circuits, etc. are not formed.

[0039] DBG (Drilling-Groove) refers to a method of wafer monolithization, in which trenches of a specified depth are formed on the surface side of the wafer, followed by grinding from the back side. The trenches formed on the surface side of the wafer can be created using methods such as blade cutting, laser cutting, or plasma cutting.

[0040] In addition, LDBG is a variation of DBG, which refers to a method of using lasers to create modified regions inside the wafer and using stress during the grinding of the back side of the wafer to achieve wafer monolithization.

[0041] A "chipset" refers to a plurality of semiconductor chips held on a protective sheet for semiconductor processing in this embodiment after the semiconductor wafer has been individually assembled. These semiconductor chips, as a whole, are shaped to have the same shape as the semiconductor wafer.

[0042] In this specification, for example, "(meth)acrylate" is used as a term to refer to "acrylate" and "methacrylate", and other similar terms are used in the same way.

[0043] "Energy rays" refer to ultraviolet rays, electron beams, etc., with ultraviolet rays being preferred.

[0044] (1. Protective film for semiconductor processing)

[0045] like Figure 1A As shown, the semiconductor processing protective sheet 1 of this embodiment has a structure in which an intermediate layer 20 and an adhesive layer 30 are sequentially stacked on a substrate 10.

[0046] The protective sheet for semiconductor processing in this embodiment is attached to a semiconductor wafer with uneven surfaces. For example, a semiconductor wafer with convex electrodes can be shown as a semiconductor wafer with uneven surfaces.

[0047] For example, such as Figure 2 As shown, the semiconductor processing protective sheet 1 of this embodiment is used such that its main surface 30a of the adhesive layer is attached to the bump forming surface 101a of a bumped semiconductor wafer, wherein bumps 102, which serve as convex electrodes, are formed on the semiconductor wafer 101. The bumps are formed in a manner that allows them to be electrically connected to the circuit formed on the semiconductor wafer, therefore the bump forming surface 101a is a circuit surface.

[0048] In this embodiment, the semiconductor wafer with bumps is monolithically processed by DBG or LDBG to form multiple semiconductor chips. That is, before or after attaching the semiconductor processing protective film, trenches are formed on the surface (circuit surface) or a modified region is formed inside the semiconductor wafer. Then, the side of the semiconductor wafer to which the semiconductor processing protective film is attached, i.e., the back side, is polished.

[0049] When bumps and depressions such as convex electrodes are formed on a semiconductor wafer, if the thickness of the semiconductor wafer is reduced through polishing, the size of the bumps and depressions increases relatively with the thickness of the semiconductor wafer. Therefore, when the bumps and depressions are not properly embedded in the semiconductor processing protective film, the following problems become more pronounced due to DBG or LDBG. That is, problems such as water immersion into the circuit surface of the semiconductor wafer during back-side polishing, and chip movement after polishing causing chips to collide with each other and thus cracks on the chips become apparent. Furthermore, when peeling off the semiconductor processing protective film after polishing, the protective film is peeled off in a state where a portion of it is attached to multiple semiconductor chips as the adhered objects (resin residue) also becomes apparent.

[0050] Therefore, in this embodiment, the physical properties of the protective sheet for semiconductor processing are controlled as follows.

[0051] (1.1 Young's modulus of a protective sheet for semiconductor processing before energy injection curing at 50°C)

[0052] In this embodiment, the Young's modulus of the protective wafer for semiconductor processing at 50°C is 600 MPa or higher. By keeping the Young's modulus within the above range, the individual chips can be sufficiently maintained even after the wafer is monolithically processed. As a result, it is possible to suppress the movement of the monolithically processed chips, which could lead to collisions between the chips and the formation of cracks on the chip.

[0053] As will be described later, since the adhesive layer and intermediate layer, which are structural elements of the semiconductor processing protective sheet of this embodiment, are energy-curable, the aforementioned Young's modulus is the Young's modulus before energy-curing. This is because chip cracks occur before the adhesive layer and intermediate layer are cured using energy rays.

[0054] The Young's modulus of the protective sheet for semiconductor processing before energy ray curing at 50°C is preferably 610 MPa or more, and more preferably 620 MPa or more.

[0055] There is no specific upper limit to the Young's modulus mentioned above, but from the perspective of the adhesion of protective sheets used in semiconductor processing, it can be, for example, 3000 MPa.

[0056] In this embodiment, the Young's modulus of the protective sheet for semiconductor processing before energy-ray curing at 50°C is determined by a tensile test. Specifically, a tensile test is performed according to JIS K 7127 (1999), and the Young's modulus is calculated from the tensile load, tensile strain, etc.

[0057] Protective films for semiconductor processing are not limited to Figure 1A The structure described herein may include other layers as long as the effects of the present invention can be achieved. That is, as long as the substrate, intermediate layer, and adhesive layer are stacked sequentially, other layers may be formed, for example, between the substrate and the intermediate layer, or between the intermediate layer and the adhesive layer. When the semiconductor processing protective sheet has other layers, it is acceptable as long as the Young's modulus of the semiconductor processing protective sheet as a whole, including the other layers, is within the above-mentioned range.

[0058] In particular, in this embodiment, such as Figure 1B As shown, it is preferable to have a buffer layer 40 on the main surface of the substrate 10 opposite to the main surface where the adhesive layer is formed. By having a buffer layer 40, the occurrence of the above-mentioned problems can be further suppressed.

[0059] Furthermore, since the buffer layer is relatively soft, there is a tendency to reduce the Young's modulus of the protective wafer used in semiconductor processing. Therefore, when the protective wafer used in semiconductor processing has a buffer layer, it is necessary to adjust the Young's modulus of the protective wafer to the range mentioned above.

[0060] The following is about Figure 1B The structural elements of the semiconductor processing protective sheet 1 shown are described in detail.

[0061] (2. Substrate)

[0062] As a substrate, there are no limitations as long as it is made of a material capable of supporting a semiconductor wafer. For example, various resin films used as substrates for back-grinding tapes can be exemplified. The substrate can be made of a single layer of resin film or a multilayer film consisting of multiple resin films stacked together.

[0063] (2.1 Physical properties of the substrate)

[0064] In this embodiment, a substrate with high rigidity is preferred. Due to the high rigidity of the substrate, it is easy to control the Young's modulus of the protective sheet for semiconductor processing within the aforementioned range. Even if the thickness of the semiconductor wafer is reduced due to grinding, the wafer can be maintained without wafer breakage. Specifically, the Young's modulus of the substrate is preferably 1000 MPa or more, more preferably 1500 MPa or more, and even more preferably 2000 MPa or more.

[0065] In this embodiment, the thickness of the substrate is preferably 15 μm or more and 200 μm or less, and more preferably 40 μm or more and 150 μm or less.

[0066] (2.2 Material of the substrate)

[0067] The preferred material for the substrate is one whose Young's modulus is within the aforementioned range. In this embodiment, examples include polyesters such as polyethylene terephthalate, polyethylene naphthalate, polyethylene terephthalate, and fully aromatic polyesters, as well as polyamides, polycarbonates, polyacetals, modified polyphenylene ethers, polyphenylene sulfides, polysulfones, polyetherketones, and biaxially stretched polypropylene. Polyesters are preferred, and polyethylene terephthalate is more preferred.

[0068] (3. Intermediate layer)

[0069] The intermediate layer is disposed between the substrate and the adhesive layer. In this embodiment, the intermediate layer is energy-curable. Therefore, before energy-curing, the intermediate layer has low viscoelasticity, allowing it to fully follow the irregularities formed on the surface of the semiconductor wafer together with the adhesive layer, embedding the irregularities into the adhesive layer and the intermediate layer. As a result, even when the semiconductor wafer is ground very thin and force is applied to convex electrodes, the adhesive layer and the intermediate layer can adequately protect the convex electrodes, etc.

[0070] On the other hand, after curing with energy rays, not only the adhesive layer but also the intermediate layer undergoes curing shrinkage. Therefore, even when peeling the protective sheet for semiconductor processing from the semiconductor wafer or the monolithized semiconductor chip, the overall elastic modulus of the protective sheet for semiconductor processing increases due to the increased elastic modulus of the intermediate layer, making it difficult for the adhesive layer to adhere to the semiconductor wafer or the monolithized semiconductor chip (which can suppress residual adhesive).

[0071] Furthermore, when a convex electrode or the like penetrates the adhesive layer, the intermediate layer embeds and protects it. The intermediate layer can consist of a single layer or multiple layers.

[0072] The thickness of the intermediate layer 20 can be set taking into account the size of the unevenness of the semiconductor wafer, such as the height of the convex electrode. In this embodiment, the thickness of the intermediate layer 20 is preferably 60 μm or more and 250 μm or less, more preferably 100 μm or more and 200 μm or less. Furthermore, the thickness of the intermediate layer refers to the total 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 layers constituting the intermediate layer.

[0073] (3.1 Composition for intermediate layer)

[0074] Since the intermediate layer is energy-curable as described above, it is preferably composed of an energy-curable composition (intermediate layer composition). In this embodiment, the intermediate layer composition preferably contains an acrylic polymer (A) with a weight-average molecular weight of 300,000 to 1,500,000 and an energy-curable acrylic polymer (B) with a weight-average molecular weight of 50,000 to 250,000. The acrylic polymer (A) can be either non-energy-curable or energy-curable, but in this embodiment, non-energy-curable is preferred.

[0075] Furthermore, unless otherwise specified, "weight-average molecular weight" in this specification refers to the converted value of polystyrene determined by gel permeation chromatography (GPC). For example, a high-speed GPC apparatus, the "HLC-8120GPC" manufactured by TOSOH, is used with a high-speed chromatographic column, "TSK gurd column H," sequentially connected to it. XL -H”, TSK GelGMH XL "TSK Gel G2000H" XL The measurements were performed using equipment (all manufactured by TOSOH) at a column temperature of 40°C and a delivery rate of 1.0 mL / min, with a differential refractive index meter as the detector.

[0076] (3.1.1 Acrylic polymers (A))

[0077] As described above, the acrylic polymer (A) can be either energy-curable or non-energy-curable. In this embodiment, the case where the acrylic polymer (A) is non-energy-curable will be described. The acrylic polymer (A) is preferably a non-energy-curable polymer having structural units derived from (meth)acrylates. Specifically, the acrylic polymer (A) is more preferably composed of an acrylic copolymer having structural units derived from alkyl (meth)acrylates (a1) and structural units derived from functionalized monomers (a2).

[0078] Alkyl methacrylates with 1 to 18 carbon atoms in the alkyl group can be used as alkyl methacrylates (a1). Specifically, examples include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, n-tridecyl methacrylate, myristyl methacrylate, palmityl(meth)acrylate, and stearate methacrylate.

[0079] The alkyl methacrylate (a1) is preferably an alkyl methacrylate with 4 to 8 carbon atoms in the alkyl group. Specifically, n-butyl methacrylate is preferred. Furthermore, the alkyl methacrylate (a1) can be used alone or in combination of two or more.

[0080] The content of structural units derived from alkyl (meth)acrylate (a1) in acrylic polymer (A) is preferably 50 to 99.5% by mass, more preferably 60 to 99% by mass, and even more preferably 80 to 95% by mass, relative to all structural units (100% by mass) of acrylic polymer (A).

[0081] If the content is 50% by mass or more, the retention performance of the adhesive sheet can be improved, and the ability to follow the surface of the substrate with large irregularities can be improved. In addition, if it is 99.5% by mass or less, it can ensure that the structural units from component (a2) are in a certain quantity.

[0082] The functional group-containing monomer (a2) is a monomer having functional groups such as hydroxyl, carboxyl, epoxy, amino, cyano, nitrogen-containing cyclogroup, or alkoxysilyl. Preferably, the functional group-containing monomer (a2) is selected from one or more of hydroxyl-containing monomers, carboxyl-containing monomers, and epoxy-containing monomers.

[0083] Examples of hydroxyl-containing monomers include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and other hydroxyalkyl methacrylates, as well as unsaturated alcohols such as vinyl alcohol and allyl alcohol.

[0084] Examples of carboxyl-containing monomers include (meth)acrylic acid, maleic acid, fumaric acid, and itaconic acid.

[0085] Examples of epoxy-containing monomers include epoxy-containing (meth)acrylates and non-acrylic epoxy-containing monomers. Examples of epoxy-containing (meth)acrylates include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, (3,4-epoxycyclohexyl)meth(meth)acrylate, and 3-epoxycyclo-2-hydroxypropyl (meth)acrylate. Examples of non-acrylic epoxy-containing monomers include glycidyl crotonate and allyl glycidyl ether.

[0086] A single functional group monomer (a2) can be used alone, or two or more can be used in combination.

[0087] Among the functionalized monomers (a2), carboxyl-containing monomers are more preferred, with (meth)acrylic acid being even more preferred, and acrylic acid being the most preferred. When a carboxyl-containing monomer is used as the functionalized monomer (a2), the cohesive force of the interlayer increases, making it easier to improve the retention properties of the interlayer.

[0088] The content of structural units derived from functional monomers (a2) in acrylic polymer (A) is preferably 0.5 to 40% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, relative to all structural units (100% by mass) of acrylic polymer (A).

[0089] If the content of structural units from component (a2) is 0.5% by mass or more, the cohesion of the intermediate layer increases, and it is also easier to achieve good compatibility with component (B). On the other hand, if the content is 40% by mass or less, it is possible to ensure that the structural units from component (a1) are in a certain quantity.

[0090] The acrylic polymer (A) can be a copolymer of (meth)acrylate (a1) and a functional monomer (a2), but it can also be a copolymer of (a1), (a2) and other monomers (a3) ​​other than these (a1) and (a2) components.

[0091] Other monomers (a3) ​​include, for example, cyclohexyl methacrylate, benzyl methacrylate, isobornyl methacrylate, dicyclopentyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenoxyethyl methacrylate, and other cyclic methacrylates, vinyl acetate, styrene, etc. Other monomers (a3) ​​can be used alone or in combination of two or more.

[0092] The content of structural units derived from other monomers (a3) ​​in acrylic polymer (A) is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to all structural units (100% by mass) of acrylic polymer (A).

[0093] The weight-average molecular weight (Mw) of the acrylic polymer (A) is preferably 300,000 to 1,500,000, more preferably 400,000 to 1,100,000, and even more preferably 450,000 to 900,000. By setting Mw below the above-mentioned upper limit, the compatibility between the acrylic polymer (A) and the acrylic polymer (B) becomes good. Furthermore, by setting Mw within the above range, the retention performance of the adhesive sheet can be easily improved.

[0094] The content of acrylic polymer (A) in the intermediate layer composition is preferably 40-95% by mass, more preferably 45-92% by mass, and even more preferably 60-90% by mass, relative to the total amount (100% by mass) of the intermediate layer composition.

[0095] Furthermore, when the intermediate layer composition is diluted with a diluent such as an organic solvent as described later, the total amount of the intermediate layer composition represents the total amount of solid components excluding the diluent. The same applies to the adhesive layer composition described later.

[0096] (3.1.2 Acrylic polymers (B))

[0097] Acrylic polymer (B) is an acrylic polymer that possesses energy-ray curable properties by introducing energy-ray polymerizable groups. The weight-average molecular weight (Mw) of acrylic polymer (B) is 50,000 to 250,000. In this embodiment, by using component (B) in the intermediate layer, the convex electrode can be fully embedded during the backside grinding of the semiconductor wafer before energy-ray curing, and by performing energy-ray curing after grinding, cohesive destruction of the intermediate layer can be prevented, making it easy to peel off well from the semiconductor chip.

[0098] The weight-average molecular weight (Mw) of the acrylic polymer (B) is preferably 60,000 to 220,000, more preferably 70,000 to 200,000, and even more preferably 85,000 to 150,000.

[0099] Acrylic polymer (B) is an acrylic polymer that incorporates energy-beta polymerizable groups and has structural units derived from (meth)acrylates. The energy-beta polymerizable groups in acrylic polymer (B) are preferably incorporated into the side chains of the acrylic polymer. The energy-beta polymerizable groups can be groups containing energy-beta polymerizable carbon-carbon double bonds, such as (meth)acryloyl, vinyl, etc., with (meth)acryloyl being preferred.

[0100] The acrylic polymer (B) is preferably a reaction product obtained by reacting a polymerizable compound (Xb) having energy-ray polymerizable groups with an acrylic copolymer (B0), wherein the acrylic copolymer (B0) has structural units derived from alkyl (meth)acrylate (b1) and structural units derived from a functionalized monomer (b2).

[0101] Alkyl methacrylates with 1 to 18 carbon atoms in the alkyl group can be used as (meth)acrylate (b1). Specific examples include compounds exemplified by component (a1). Preferably, the (meth)acrylate (b1) is an alkyl methacrylate with 4 to 8 carbon atoms in the alkyl group. Specifically, n-butyl methacrylate is preferred. Furthermore, these alkyl methacrylates can be used alone or in combination of two or more.

[0102] Of the acrylic copolymer (B0), the content of structural units derived from alkyl methacrylate (b1) in the acrylic copolymer (B0) is preferably 50–95% by mass, more preferably 60–85% by mass, and even more preferably 65–80% by mass, relative to all structural units (100% by mass) of all structural units. If this content is 50% by mass or more, the shape of the formed intermediate layer can be adequately maintained. Furthermore, if it is 95% by mass or less, it can be ensured that the structural units derived from component (b2), which are the reaction sites with the polymerizable compound (Xb), are present in a certain amount.

[0103] As a functional group-containing monomer (b2), monomers having the functional groups exemplified in the above-described functional group-containing monomers (a2) can be listed, preferably selected from one or more of hydroxyl-containing monomers, carboxyl-containing monomers, and epoxy-containing monomers. As specific compounds of these functional group-containing monomers, compounds identical to those exemplified by components (a2) can be shown.

[0104] Furthermore, as the functionalized monomer (b2), a hydroxyl-containing monomer is preferred, and more preferably, various hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate. By using hydroxyalkyl methacrylates, the polymerizable compound (Xb) can be reacted with the acrylic copolymer (B0) more readily.

[0105] Furthermore, the functional groups in the functionalized monomer (a2) used in the acrylic polymer (A) and the functionalized monomer (b2) used in the acrylic polymer (B) may be the same or different, but are preferably different. That is, for example, if the functionalized monomer (a2) is a carboxyl-containing monomer, it is preferable that the functionalized monomer (b2) is a hydroxyl-containing monomer. In this way, when the functional groups are different, the acrylic polymer (B) can be preferentially crosslinked, for example, by using a crosslinking agent described later, which makes it easier to improve the retention properties of the adhesive sheet.

[0106] The content of structural units derived from functionalized monomers (b2) in the acrylic copolymer (B0) is preferably 10–45% by mass, more preferably 15–40% by mass, and even more preferably 20–35% by mass, relative to all structural units (100% by mass) of all structural units in the acrylic copolymer (B0). If it is 10% by mass or more, it ensures a greater number of reaction sites with the polymerizable compound (Xb), facilitating the introduction of energy-ray polymerizable groups into the side chains. Furthermore, if it is 45% by mass or less, the shape of the formed intermediate layer can be adequately maintained.

[0107] Acrylic copolymers (B0) can be copolymers of alkyl (meth)acrylate (b1) and functionalized monomers (b2), but can also be copolymers of components (b1), (b2), and other monomers (b3) besides these components (b1) and (b2).

[0108] Other monomers (b3) can be listed as monomers exemplified above (a3).

[0109] The content of structural units derived from other monomers (b3) in the acrylic copolymer (B0) is preferably 0 to 30% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to all structural units (100% by mass) of all structural units of the acrylic copolymer (B0).

[0110] Polymerizable compounds (Xb) are compounds having energy-beam polymerizable groups and substituents (hereinafter sometimes simply referred to as "reactive substituents") capable of reacting with functional groups in structural units derived from component (b2) of acrylic copolymers (B0).

[0111] As described above, examples of energy-ray polymerizable groups include (meth)acryloyl and vinyl groups, with (meth)acryloyl being preferred. Furthermore, the polymerizable compound (Xb) is preferably a compound having 1 to 5 energy-ray polymerizable groups per molecule.

[0112] As a reactive substituent in the polymerizable compound (Xb), it can be appropriately modified according to the functional group possessed by the functional group-containing monomer (b2). For example, isocyanate group, carboxyl group, epoxy group, etc. can be listed. From the perspective of reactivity, isocyanate group is preferred. When the polymerizable compound (Xb) has an isocyanate group, for example, when the functional group of the functional group-containing monomer (b2) is hydroxyl, it can easily react with acrylic copolymer (B0).

[0113] Specific polymerizable compounds (Xb) include, for example, (meth)acryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acryloyl isocyanate, allyl isocyanate, (meth)acrylate glycidyl ester, (meth)acrylic acid, etc. These polymerizable compounds (Xb) can be used alone or in combination of two or more.

[0114] From the perspective of compounds having an isocyanate group suitable for use as the above-mentioned reactive substituent and having a suitable distance between the main chain and the energy-ray polymerizable group, (meth)acryloyloxyethyl isocyanate is preferred.

[0115] The polymerizable compound (Xb) preferably reacts with 40 to 98 equivalents of functional groups from the total amount (100 equivalents) of functional groups from the functional group-containing monomer (b2) in the acrylic polymer (B), more preferably with 60 to 90 equivalents of functional groups, and even more preferably with 70 to 85 equivalents of functional groups.

[0116] In the composition for the intermediate layer, the content of acrylic polymer (B) is preferably 5 to 60 parts by mass relative to 100 parts by mass of acrylic polymer (A), more preferably 10 to 35 parts by mass. By setting the content of component (B) to a relatively small amount, the intermediate layer can easily follow the contours of the semiconductor wafer.

[0117] (3.1.3 Crosslinking agent)

[0118] The intermediate layer composition preferably further contains a crosslinking agent. Examples of crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, and metal chelate crosslinking agents, among which isocyanate crosslinking agents are preferred. If an isocyanate crosslinking agent is used, for example, when component (B) has hydroxyl groups, the crosslinking agent preferentially crosslinks the acrylic polymer (B).

[0119] The intermediate layer composition is cross-linked using a cross-linking agent, for example, by heating after coating. Since the intermediate layer is cross-linked with acrylic polymers, especially low molecular weight acrylic polymers (B), it can be appropriately formed into a coating film and easily perform its function as an intermediate layer.

[0120] The content of crosslinking agent is preferably 0.1 to 10 parts by weight relative to 100 parts by weight of acrylic polymer (A), more preferably 0.5 to 7 parts by weight, and even more preferably 1 to 5 parts by weight.

[0121] Polyisocyanate compounds can be listed as crosslinking agents for isocyanates. Specific examples of polyisocyanate compounds include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and aliphatic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. Furthermore, their biuret forms, isocyanurate forms, and adducts as reaction products with low-molecular-weight compounds containing active hydrogen, such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil, can also be listed.

[0122] These isocyanate crosslinking agents can be used alone or in combination of two or more. Furthermore, polyol adducts (e.g., trimethylolpropane) of aromatic polyisocyanates such as toluene diisocyanate are preferred.

[0123] In addition, examples of epoxy crosslinking agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-phenylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trihydroxypropane diglycidyl ether, diglycidyl aniline, and diglycidylamine. These epoxy crosslinking agents can be used alone or in combination of two or more.

[0124] Examples of metal chelate crosslinking agents include acetylacetone, ethyl acetoacetate, etc.

[0125] Compounds formed by coordination of tris(2,4-pentanedione) and other polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. These metal chelate crosslinking agents can be used alone or in combination of two or more.

[0126] Examples of aziridine crosslinking agents include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane tri-β-aziridine propionate, tetramethylolmethane tri-β-aziridine propionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylene melamine, bis(isophthaloyl-1-(2-methylaziridine), tri-1-(2-methylaziridine)phosphine, trimethylolpropane tri-β-(2-methylaziridine) propionate, and hexa[1-(2-methyl)-aziridine]triphosphatriazine.

[0127] (3.1.4 Photopolymerization initiator)

[0128] The intermediate layer composition preferably further contains a photopolymerization initiator. By containing a photopolymerization initiator, the intermediate layer composition can be easily cured by energy rays such as ultraviolet light.

[0129] Examples of photopolymerization initiators include acetophenone, 2,2-diethoxybenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, michalcone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, benzyl dimethyl ketal, dibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-ethylanthraquinone, 2,2-dimethoxy-1,2-diphenylethane-1-one, and 1-hydroxycyclohexane. Low molecular weight polymerization initiators such as hexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylacetone-1,2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-butanone-1,2-hydroxy-2-methyl-1-phenyl-propane-1-one, diethylthioxanone, isopropylthioxanone, and 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, as well as oligomerized polymerization initiators such as oligomerized {2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]acetone}, are used. These photopolymerization initiators can be used alone or in combination of two or more. Furthermore, 1-hydroxycyclohexylphenyl ketone is preferred.

[0130] In order to ensure sufficient curing even when the content of acrylic polymer (B) is low, the content of photopolymerization initiator is preferably 1 to 10 parts by mass relative to 100 parts by mass of acrylic polymer (A), more preferably 2 to 8 parts by mass.

[0131] Without impairing the effects of the present invention, the intermediate layer composition may also contain other additives. Examples of other additives include antioxidants, plasticizers, fillers, rust inhibitors, pigments, dyes, and tackifiers. When these additives are present, the content of each additive is preferably 0.01 to 6 parts by weight, more preferably 0.01 to 2 parts by weight, relative to 100 parts by weight of the acrylic polymer (A).

[0132] Furthermore, the Young's modulus of protective sheets used in semiconductor processing can be adjusted, for example, when using acrylic polymers (B), by adjusting the type and amount of monomers constituting the acrylic polymer (B) and the amount of energy-polymerizable groups introduced into the acrylic polymer (B). For example, the Young's modulus tends to increase when the amount of energy-polymerizable groups is increased. It can also be appropriately adjusted by adjusting the amount of crosslinking agent incorporated in the intermediate layer and the amount of photopolymerization initiator.

[0133] (4. Adhesive layer)

[0134] An adhesive layer is attached to the circuit surface of a semiconductor wafer, protecting and supporting the semiconductor wafer until it is peeled off. In this embodiment, the adhesive layer is energy-curable. Therefore, before energy-curing, the adhesive layer, together with the intermediate layer, fully follows the irregularities formed on the surface of the semiconductor wafer, embedding the irregularities into the semiconductor processing protective sheet. As a result, even when the semiconductor wafer is ground to a very thin thickness and force is applied to the convex electrodes, the semiconductor processing protective sheet can adequately protect the convex electrodes, etc.

[0135] On the other hand, after curing with energy rays, the adhesive layer undergoes curing shrinkage. Therefore, even when the protective film for semiconductor processing is peeled off from the semiconductor wafer or the monolithized semiconductor chip, the adhesive layer is less prone to cohesive failure, thus preventing the adhesive layer from partially adhering to the semiconductor wafer or the monolithized semiconductor chip (which can suppress residual adhesive).

[0136] In addition, the adhesive layer can consist of one layer (single layer) or multiple layers (two or more layers).

[0137] There is no particular limitation on the thickness of the adhesive layer, as long as it is sufficient to support the semiconductor wafer. In this embodiment, the thickness of the adhesive layer is preferably 5 μm to 500 μm, more preferably 8 μm to 100 μm. Furthermore, the thickness of the adhesive layer refers to the overall thickness of the adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers refers to the total thickness of all layers constituting the adhesive layer.

[0138] (4.1 Composition for adhesive layer)

[0139] As described above, the adhesive layer is energy-curable, and therefore it is preferably formed from a composition (adhesive composition) that is energy-curable. In this embodiment, the adhesive layer composition is preferably a composition containing a resin.

[0140] The adhesive layer composition contains, for example, acrylic polymers, polyurethanes, rubber polymers, polyolefins, silicones, etc., as adhesive components (adhesive resins) that enable the adhesive layer to exhibit adhesiveness. Among these, acrylic polymers are preferred.

[0141] For compositions used in adhesive layers, energy-curable properties can be achieved by incorporating energy-curable compounds different from those of the adhesive resin, but it is preferable that the adhesive resin itself has energy-curable properties. When the adhesive resin itself has energy-curable properties, energy-curable polymeric groups are introduced into the adhesive resin, preferably into the main chain or side chain of the adhesive resin.

[0142] Furthermore, when incorporating an energy-curable compound different from the adhesive resin, monomers or oligomers having energy-curable groups can be used as the energy-curable compound. The oligomer is a weight-average molecular weight (Mw) less than 10,000, such as urethane (meth)acrylate. Moreover, even when the adhesive resin itself is energy-curable, an energy-curable compound can be incorporated into the adhesive layer composition in addition to the adhesive resin.

[0143] The following provides a more detailed explanation of the case where the adhesive layer contains an energy-curable adhesive resin that is an acrylic polymer (hereinafter also referred to as "acrylic polymer (C)").

[0144] (4.1.1 Acrylic polymers (C))

[0145] Acrylic polymer (C) is an acrylic polymer that incorporates energy-beta polymerizable groups and has structural units derived from (meth)acrylates. The energy-beta polymerizable groups are preferably incorporated into the side chains of the acrylic polymer.

[0146] The acrylic polymer (C) is preferably a reaction product obtained by reacting a polymerizable compound (Xc) having energy-ray polymerizable groups with an acrylic copolymer (C0), wherein the acrylic copolymer (C0) has structural units derived from alkyl (meth)acrylate (C1) and structural units derived from a functionalized monomer (C2).

[0147] As the alkyl methacrylate (c1), an alkyl methacrylate having 1 to 18 carbon atoms in the alkyl group can be used. Specific examples include alkyl methacrylates with 1 to 18 carbon atoms in the alkyl group, as exemplified by component (a1). Preferably, the alkyl methacrylate (c1) has 4 to 8 carbon atoms in the alkyl group. Specifically, 2-ethylhexyl methacrylate and n-butyl methacrylate are preferred, and n-butyl methacrylate is more preferred. Furthermore, one of these alkyl methacrylates can be used alone, or two or more can be used in combination.

[0148] From the perspective of improving the adhesion of the formed adhesive layer, the content of structural units derived from (meth)acrylate (c1) in the acrylic copolymer (C0) is preferably 50 to 99% by mass, more preferably 60 to 97% by mass, and even more preferably 70 to 96% by mass, relative to all structural units (100% by mass) of the acrylic copolymer (C0).

[0149] For example, in addition to 2-ethylhexyl (meth)acrylate and n-butyl (meth)acrylate mentioned above, alkyl (meth)acrylate (C1) may also contain ethyl (meth)acrylate and methyl (meth)acrylate. By including these monomers, the adhesive properties of the adhesive layer can be easily adjusted to the desired adhesive properties.

[0150] As a functional group-containing monomer (c2), examples can be given of monomers having the functional groups exemplified by the functional group-containing monomer (a2) described above. Specifically, it is preferably selected from one or more monomers containing hydroxyl groups, carboxyl groups, and epoxy groups. As specific compounds of these functional group-containing monomers, compounds identical to those exemplified by component (a2) can be given.

[0151] As a functional group-containing monomer (c2), among the above monomers, hydroxyl-containing monomers are more preferred, among which hydroxyalkyl esters of (meth)acrylate are more preferred, 2-hydroxyethyl esters of (meth)acrylate and 4-hydroxybutyl esters of (meth)acrylate are even more preferred, and 4-hydroxybutyl esters of (meth)acrylate are particularly preferred.

[0152] By using hydroxyalkyl methacrylate as component (C2), the polymerizable compound (XC) can be reacted with the acrylic copolymer (C0) more readily. Furthermore, when 4-hydroxybutyl methacrylate is used, the tensile strength of the interlayer increases, making it easier to prevent adhesive residue.

[0153] The content of structural units derived from functional monomers (c2) in the acrylic copolymer (C0) is preferably 1 to 40% by mass, more preferably 2 to 35% by mass, further preferably 3 to 30% by mass, and even more preferably 10 to 30% by mass, relative to all structural units (100% by mass) of the acrylic copolymer (C0).

[0154] If the content is 1% by mass or more, it ensures that the functional groups that are reaction sites with the polymerizable compound (Xc) are present in a certain amount. Therefore, the adhesive layer can be properly cured by irradiation with energy rays, thus reducing the adhesion after irradiation with energy rays. Furthermore, if the content is 40% by mass or less, a sufficient pot life can be ensured when the adhesive layer is formed by applying a solution of the composition.

[0155] Acrylic copolymers (C0) can be copolymers of alkyl (meth)acrylate (C1) and functionalized monomers (C2), but can also be copolymers of components (C1), (C2), and other monomers (C3) besides these components (C1) and (C2).

[0156] Other monomers (c3) can be listed as examples of the monomers (a3) ​​mentioned above.

[0157] The content of structural units derived from other monomers (c3) in the acrylic copolymer (C0) is preferably 0 to 30% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to all structural units (100% by mass) of all structural units of the acrylic copolymer (C0).

[0158] Similar to the polymerizable compound (Xb) described above, the polymerizable compound (Xc) is a compound having energy-beam polymerizable groups and substituents (reactive substituents) that can react with functional groups from the structural units of the (c2) component in the acrylic copolymer (C0), preferably a compound having 1 to 5 energy-beam polymerizable groups per molecule.

[0159] Specific examples of reactive substituents and energy-beam polymerizable groups are the same as those of polymerizable compound (Xb), therefore, the reactive substituent is preferably an isocyanate group, and the energy-beam polymerizable group is preferably a (meth)acryloyl group.

[0160] Furthermore, as specific polymerizable compounds (Xc), compounds identical to those exemplified by polymerizable compound (Xb) described above can be listed, with (meth)acryloyloxyethyl isocyanate being preferred. Additionally, polymerizable compounds (Xc) can be used alone or in combination of two or more.

[0161] The polymerizable compound (Xc) preferably reacts with 30 to 98 equivalents of functional groups from the total amount (100 equivalents) of functional groups from the functional group-containing monomer (C2) in the acrylic polymer (C0), more preferably with 40 to 95 equivalents of functional groups.

[0162] The weight-average molecular weight (Mw) of the acrylic polymer (C) is preferably 10,000 to 1,500,000, more preferably 250,000 to 1,000,000, and even more preferably 350,000 to 800,000. By having such a Mw, the adhesive layer can be given appropriate adhesion.

[0163] Even when the adhesive resin has energy-curable properties, it is preferable to include an energy-curable compound other than the adhesive resin in the composition for the adhesive layer. As such an energy-curable compound, monomers or oligomers having unsaturated groups in their molecules and capable of polymerization and curing by irradiation with energy rays are preferred.

[0164] Specifically, examples include trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol (meth)acrylate and other poly(meth)acrylate monomers, urethane (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, epoxy (meth)acrylates and other oligomers.

[0165] Among them, from the perspective of higher molecular weight and less reduction of the elastic modulus of adhesive layer, urethane (meth)acrylate oligomers are preferred.

[0166] (4.1.2 Crosslinking agent)

[0167] The adhesive layer composition preferably further contains a crosslinking agent. The adhesive layer composition is crosslinked, for example, by heating after coating, using the crosslinking agent. In the adhesive layer, the acrylic polymer (C) is crosslinked by the crosslinking agent, thereby enabling the proper formation of a coating film and facilitating its function as an adhesive layer.

[0168] Examples of crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, and chelate crosslinking agents, with isocyanate crosslinking agents being preferred. Crosslinking agents can be used alone or in combination of two or more. Furthermore, specific examples of isocyanate crosslinking agents include those exemplified as crosslinking agents suitable for use in intermediate layer compositions, and the preferred isocyanate crosslinking agents are also the same.

[0169] The content of crosslinking agent is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of acrylic polymer (C), more preferably 0.1 to 7 parts by mass, and even more preferably 0.3 to 4 parts by mass.

[0170] (4.1.3 Photopolymerization initiator)

[0171] The adhesive layer composition preferably further contains a photopolymerization initiator. Examples of photopolymerization initiators include the compounds described above used in the intermediate layer composition. Furthermore, the photopolymerization initiator can be used alone or in combination of two or more. Among the above-mentioned photopolymerization initiators, 2,2-dimethoxy-1,2-diphenylethane-1-one and 1-hydroxycyclohexylphenyl one are preferred.

[0172] The content of photopolymerization initiator is preferably 0.5 to 15 parts by mass relative to 100 parts by mass of acrylic polymer (C), more preferably 1 to 12 parts by mass, and even more preferably 4.5 to 10 parts by mass.

[0173] Without impairing the effects of the present invention, the adhesive layer composition may also contain other additives. Examples of other additives include tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When these additives are contained, the content of each additive is preferably 0.01 to 6 parts by weight, more preferably 0.02 to 2 parts by weight, relative to 100 parts by weight of the acrylic polymer (C).

[0174] Furthermore, the Young's modulus of protective sheets used in semiconductor processing can be adjusted, for example, when using acrylic polymers (C), by adjusting the type and amount of monomers constituting the acrylic polymer (C), and the amount of energy-emitting polymeric groups introduced into the acrylic polymer (C). For example, the Young's modulus tends to increase when the amount of energy-emitting polymeric groups is increased. It can also be appropriately adjusted by adjusting the amount of crosslinking agent incorporated into the adhesive layer, the amount of photopolymerization initiator, etc.

[0175] (5. Buffer layer)

[0176] like Figure 1B As shown, a buffer layer is formed on the main surface of the substrate opposite to the main surface where the adhesive layer is formed. The buffer layer 40 is a layer softer than the substrate, which relieves stress during the grinding of the back side of the semiconductor wafer and prevents cracks and defects from forming on the semiconductor wafer. Furthermore, during the grinding of the back side, the semiconductor wafer with the semiconductor processing protective sheet attached is placed on the vacuum table in between the semiconductor processing protective sheet, but because the buffer layer serves as a structural layer for the semiconductor processing protective sheet, it is easy to hold it properly on the vacuum table.

[0177] The thickness of the buffer layer is preferably 1–100 μm, more preferably 5–80 μm, and even more preferably 10–60 μm. By setting the thickness of the buffer layer within the above range, the buffer layer can appropriately alleviate the stress during grinding of the back side.

[0178] The buffer layer can be a layer formed by a composition of a buffer layer containing a polymerizable compound containing energy rays, or it can be a polypropylene film, an ethylene-vinyl acetate copolymer film, an ionomer resin film, an ethylene-(meth)acrylic acid copolymer film, an ethylene-(meth)acrylic acid copolymer film, an LDPE film, an LLDPE film, etc.

[0179] In addition, a substrate with a buffer layer can be obtained by laminating a buffer layer on one or both sides of the substrate.

[0180] (5.1 Composition for buffer layer)

[0181] Compositions for buffer layers containing energy-ray polymerizable compounds can be cured by irradiation with energy rays.

[0182] Furthermore, more specifically, the buffer layer composition containing an energy-emitting polymerizable compound preferably contains urethane (meth)acrylate (d1) and a polymerizable compound having an alicyclic or heterocyclic group having 6 to 20 cyclic atoms (d3). In addition to the components (d1) and (d3) mentioned above, the buffer layer composition may also contain a multifunctional polymerizable compound (d2) and / or a polymerizable compound having functional groups (d4). Furthermore, in addition to the components mentioned above, the buffer layer composition may also contain a photopolymerization initiator. Moreover, the buffer layer composition may also contain other additives or resin components within a range that does not impair the effects of the present invention.

[0183] The following is a detailed description of the components contained in the composition for a buffer layer containing an energy-ray polymerizable compound.

[0184] (5.1.1 Carbamate (meth)acrylate (d1))

[0185] urethane (meth)acrylate (d1) is a compound having at least a (meth)acryloyl group and an urethane bond, which has the property of being polymerized and cured by irradiation with energy rays. Uramel (meth)acrylate (d1) is an oligomer or polymer.

[0186] The weight-average molecular weight (Mw) of component (d1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, and even more preferably 3,000 to 20,000. Furthermore, the number of (meth)acryloyl groups in component (d1) (hereinafter also referred to as "number of functional groups") can be monofunctional, difunctional, or trifunctional or more, but monofunctional or difunctional is preferred.

[0187] Component (d1) can be obtained by reacting a hydroxyl-containing (meth)acrylate with a terminal isocyanate urethane prepolymer, which is obtained by reacting a polyol compound with a polyisocyanate compound. Furthermore, component (d1) can be used alone or in combination of two or more components.

[0188] The polyol compound used as a raw material for component (d1) is not particularly limited as long as it has two or more hydroxyl groups. It can be any of the following: difunctional diol, trifunctional triol, or polyol with more than four functionalities, but difunctional diols are preferred, and polyester-type diols or polycarbonate-type diols are more preferred.

[0189] Examples of polyisocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norbornene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, ω,ω'-diisocyanate, and dimethylcyclohexane; and aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, dimethylbiphenyl diisocyanate, tetramethylene xylene diisocyanate, and naphthalene-1,5-diisocyanate.

[0190] Among them, isophorone diisocyanate, hexamethylene diisocyanate, and xylene diisocyanate are preferred.

[0191] By reacting a hydroxyl-containing (meth)acrylate with a terminal isocyanate urethane prepolymer, urethane (meth)acrylate (d1) can be obtained, wherein the terminal isocyanate urethane prepolymer is obtained by reacting the aforementioned polyol compound with a polyisocyanate compound. There is no particular limitation on the hydroxyl-containing (meth)acrylate, as long as it is a compound having both a hydroxyl group and a (meth)acryloyl group in at least one molecule.

[0192] Specific examples of hydroxyl-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and other hydroxyalkyl (meth)acrylates; hydroxyl-containing (meth)acrylamides such as N-hydroxymethyl (meth)acrylamide; and reaction products obtained by reacting (meth)acrylate with diglycidyl esters of vinyl alcohol, vinyl phenol, or bisphenol A.

[0193] Preferably, hydroxyalkyl methacrylate is used, and more preferably, 2-hydroxyethyl methacrylate is used.

[0194] As for the conditions for reacting the terminal isocyanate urethane prepolymer and the hydroxyl-containing (meth)acrylate, it is preferable to react at 60 to 100°C for 1 to 4 hours in the presence of a solvent and catalyst added as needed.

[0195] The content of component (d1) in the buffer layer composition is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 25 to 55% by mass, relative to the total amount (100% by mass) of the buffer layer composition.

[0196] (5.1.2 Multifunctional polymeric compounds (d2))

[0197] Multifunctional polymerizable compounds are compounds containing two or more photopolymerizable unsaturated groups. These photopolymerizable unsaturated groups are functional groups containing carbon-carbon double bonds, such as (meth)acryloyl, vinyl, allyl, and vinylbenzyl. Two or more photopolymerizable unsaturated groups can also be used in combination. A three-dimensional network structure (cross-linked structure) is formed by reacting the photopolymerizable unsaturated groups in the multifunctional polymerizable compound with the (meth)acryloyl group in component (d1) or with each other in component (d2). When using multifunctional polymerizable compounds, compared to using compounds containing only one photopolymerizable unsaturated group, the cross-linked structure formed by irradiation with energy rays increases, thus the buffer layer exhibits unique viscoelasticity, easily relieving stress during back-side grinding.

[0198] Furthermore, there is overlap between the definition of component (d2) and the definitions of component (d3) or component (d4) described later, but the overlap is included in component (d2). For example, a compound having an alicyclic or heterocyclic group with 6 to 20 cyclic atoms and having two or more (meth)acryloyl groups is included in both definitions of component (d2) and component (d3), but in this invention, such a compound is considered to be included in component (d2). Similarly, a compound containing functional groups such as hydroxyl, epoxy, amide, or amino groups and having two or more (meth)acryloyl groups is included in both definitions of component (d2) and component (d4), but in this invention, such a compound is considered to be included in component (d2).

[0199] From the above perspective, the number of photopolymerizable unsaturated groups (number of functional groups) in a multifunctional polymerizable compound is preferably 2 to 10, more preferably 3 to 6.

[0200] Furthermore, the weight-average molecular weight of component (d2) is preferably 30 to 40,000, more preferably 100 to 10,000, and even more preferably 200 to 1,000.

[0201] Specific components (d2) may include, for example, 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, dipentaerythritol hexa(meth)acrylate, divinylbenzene, vinyl(meth)acrylate, divinyl adipate, N,N'-methylenebis(meth)acrylamide, etc. Dipentaerythritol hexa(meth)acrylate is preferred. Furthermore, components (d2) may be used alone or in combination of two or more.

[0202] The content of component (d2) in the buffer layer composition is preferably 2 to 40% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, relative to the total amount (100% by mass) of the composition for the buffer layer.

[0203] (5.1.3 Polymerizable compounds having alicyclic or heterocyclic groups with 6 to 20 cyclic atoms (d3))

[0204] Component (d3) is a polymeric compound having an alicyclic or heterocyclic group having 6 to 20 cyclic atoms, and preferably a compound having at least one (meth)acryloyl group, more preferably a compound having one (meth)acryloyl group. By using component (d3), the film-forming properties of the obtained buffer layer composition can be improved.

[0205] Furthermore, there is overlap between the definition of component (d3) and the definition of component (d4) described later, but the overlap is included in component (d4). For example, although a compound having at least one (meth)acryloyl group, an alicyclic or heterocyclic group having 6 to 20 cyclic atoms, and functional groups such as hydroxyl, epoxy, amide, and amino groups is included in both definitions of component (d3) and component (d4), in this invention, such a compound is considered to be included in component (d4).

[0206] Specific examples of ingredient (d3) include isobornyl methacrylate, dicyclopentenyl methacrylate, dicyclopentyl methacrylate, dicyclopentenoxy(meth)acrylate, cyclohexyl methacrylate, adamantane methacrylate, and other alicyclic (meth)acrylates; as well as heterocyclic (meth)acrylates such as tetrahydrofurfuryl methacrylate and morpholine(meth)acrylate. Furthermore, ingredient (d3) can be used alone or in combination of two or more.

[0207] Among (meth)acrylates containing alicyclic groups, isobornyl (meth)acrylate is preferred, and among (meth)acrylates containing heterocyclic groups, tetrahydrofurfuryl (meth)acrylate is preferred.

[0208] The content of component (d3) in the buffer layer composition is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 25 to 55% by mass, relative to the total amount (100% by mass) of the composition for the buffer layer.

[0209] Furthermore, the content ratio of component (d2) to component (d3) in the composition for the buffer layer [(d2) / (d3)] is preferably 0.1 to 3.0, more preferably 0.15 to 2.0, and even more preferably 0.18 to 1.0.

[0210] (5.1.4 Polymers with functional groups (d4))

[0211] Component (d4) is a polymeric compound containing functional groups such as hydroxyl, epoxy, amide, and amino groups, and is preferably a compound having at least one (meth)acryloyl group, more preferably a compound having one (meth)acryloyl group.

[0212] Component (d4) and component (d1) are well compatible, making it easy to adjust the viscosity of the composition for the buffer layer to a suitable range. Furthermore, even when the buffer layer is made relatively thin, the buffering performance is good.

[0213] Examples of components (d4) include (meth)acrylates containing hydroxyl groups, compounds containing epoxy groups, compounds containing amide groups, and (meth)acrylates containing amino groups. Among these, (meth)acrylates containing hydroxyl groups are preferred.

[0214] Examples of hydroxyl-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, phenylhydroxypropyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl acrylate. Among these, hydroxyl-containing (meth)acrylates having an aromatic ring, such as phenylhydroxypropyl (meth)acrylate, are more preferred. Furthermore, component (d4) can be used alone or in combination of two or more.

[0215] To improve the film-forming properties of the buffer layer composition, the content of component (d4) in the buffer layer composition is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass, relative to the total amount (100% by mass) of the buffer layer composition.

[0216] Furthermore, the content ratio of component (d3) to component (d4) in the composition for the buffer layer [(d3) / (d4)] is preferably 0.5 to 3.0, more preferably 1.0 to 3.0, and even more preferably 1.3 to 3.0.

[0217] (5.1.5 Polymers other than components (d1) to (d4) (d5))

[0218] Without impairing the effects of the present invention, the composition for the buffer layer may also contain other polymeric compounds (d5) besides the components (d1) to (d4) mentioned above.

[0219] Examples of components (d5) include alkyl (meth)acrylates having alkyl groups having 1 to 20 carbon atoms, styrene, hydroxyethyl vinyl ethers, hydroxybutyl vinyl ethers, N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam, and other vinyl compounds. Furthermore, components (d5) can be used alone or in combination of two or more.

[0220] The content of component (d5) in the composition for the buffer layer is preferably 0-20% by mass, more preferably 0-10% by mass, further preferably 0-5% by mass, and particularly preferably 0-2% by mass.

[0221] (5.1.6 Photopolymerization Initiator)

[0222] From the perspective of shortening the light-based polymerization time and reducing the amount of light irradiation when forming the buffer layer, the composition for the buffer layer preferably further contains a photopolymerization initiator.

[0223] Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, phosphine oxide compounds, titanocetamene compounds, thioxanthone compounds, peroxides, and photosensitizers such as amines or quinones. More specifically, examples include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzylphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. These photopolymerization initiators can be used alone or in combination of two or more.

[0224] The content of photopolymerization initiator in the composition for the buffer layer is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass, relative to the total amount of energy-ray polymerizable compound (100 parts by mass).

[0225] (5.1.7 Other additives)

[0226] Without impairing the effects of the present invention, the composition for the buffer layer may also contain other additives. Examples of other additives include antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When these additives are incorporated, the content of each additive in the composition for the buffer layer is preferably 0.01 to 6 parts by mass, more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the total amount of energy-ray polymerizable compound.

[0227] A buffer layer formed from a buffer layer composition containing an energy-ray polymerizable compound is obtained by polymerizing and curing the aforementioned buffer layer composition by irradiating it with energy rays. In other words, the buffer layer is a product formed by curing the buffer layer composition.

[0228] Therefore, the buffer layer preferably contains polymeric units from component (d1) and polymeric units from component (d3). Furthermore, the buffer layer may also contain polymeric units from component (d2) and / or from component (d4), and may also contain polymeric units from component (d5). The proportion of each polymeric unit in the buffer layer is generally consistent with the proportion (addition ratio) of each component in the composition constituting the buffer layer.

[0229] (6. Peeling tablets)

[0230] Release tabs can be attached to the surface of the protective sheet for semiconductor processing. Specifically, the release tabs are attached to the surface of the adhesive layer of the protective sheet for semiconductor processing. By attaching to the surface of the adhesive layer, the release tabs protect the adhesive layer during transportation and storage. The release tabs are attached to the protective sheet for semiconductor processing in a peelable manner and are removed from the protective sheet before use (i.e., before attaching the wafer).

[0231] A release sheet is a release sheet in which at least one side has been subjected to a release treatment. Specifically, examples include release sheets made by coating a release agent on the surface of a substrate for release sheets.

[0232] As the substrate for the release liner, a resin film is preferred. Examples of resins constituting the resin film include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, as well as polyolefin resins such as polypropylene resin and polyethylene resin. Examples of release agents include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluorinated resins.

[0233] The thickness of the release sheet is not particularly limited, but it is preferably 10 to 200 μm, more preferably 20 to 150 μm.

[0234] (7. Manufacturing method of protective film for semiconductor processing)

[0235] The method for manufacturing the semiconductor processing protective sheet of this embodiment is not particularly limited as long as it is a method that can form an intermediate layer and an adhesive layer on one main surface of the substrate and a buffer layer on the other main surface of the substrate, and a known method can be used.

[0236] First, for example, a composition for forming an intermediate layer containing the above-mentioned components is prepared, or a composition for forming an intermediate layer is prepared by diluting the composition for forming an intermediate layer with a solvent or the like, as a composition for forming an intermediate layer.

[0237] Similarly, for example, a composition for forming an adhesive layer containing the above-mentioned components, or a composition obtained by diluting the composition for forming an adhesive layer with a solvent or the like, can be prepared as an adhesive layer composition for forming an adhesive layer. Similarly, for example, a composition for forming a buffer layer containing the above-mentioned components, or a composition obtained by diluting the composition for forming a buffer layer with a solvent or the like, can be prepared as a buffer layer composition for forming a buffer layer.

[0238] Examples of organic solvents include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.

[0239] Next, using known methods such as spin coating, spray coating, bar coating, knife coating, roller coating, blade coating, mold coating, and gravure coating, the buffer layer composition is applied to the release surface of the first release sheet to form a coating film. This coating film is then semi-cured to form a buffer layer film on the release sheet. The buffer layer film formed on the release sheet is then bonded to a substrate, and the buffer layer film is allowed to fully cure, thereby forming the buffer layer.

[0240] In this embodiment, curing of the coating is preferably performed by irradiation with energy rays. Furthermore, the curing of the coating can be carried out in a single curing process or in multiple stages.

[0241] Next, the intermediate layer is coated with the composition onto the release treatment surface of the second release sheet using a known method and then heated and dried to form an intermediate layer on the second release sheet. Then, the intermediate layer on the second release sheet is bonded to the side of the substrate where the buffer layer is not formed, and the second release sheet is removed.

[0242] Next, an adhesive layer is applied to the release surface of the third release sheet using a known method and then heated and dried to form an adhesive layer on the third release sheet. Then, by bonding the adhesive layer on the third release sheet to the intermediate layer, a semiconductor processing protective sheet is obtained in which an intermediate layer and an adhesive layer are sequentially formed on one main surface of the substrate, and a buffer layer is formed on the other main surface of the substrate. The third release sheet can be removed when using the semiconductor processing protective sheet.

[0243] (8. Manufacturing methods for semiconductor devices)

[0244] The semiconductor processing protective sheet of this embodiment is preferably used when it is attached to the surface of a semiconductor wafer in a DBG and the back side of the wafer is polished. In particular, the semiconductor processing protective sheet of this embodiment is preferably used in an LDBG, which can obtain a chip assembly with a small kerf width when the semiconductor wafer is monolithically processed.

[0245] As a non-limiting example of the use of protective sheets for semiconductor processing, the manufacturing method of semiconductor devices will be further described below.

[0246] Specifically, the manufacturing method of a semiconductor device includes at least the following steps 1 to 4.

[0247] Step 1: The process of attaching the above-mentioned semiconductor processing protective sheet to the surface of a semiconductor wafer with uneven surfaces;

[0248] Step 2: A step of forming trenches from the surface side of the semiconductor wafer, or forming modified regions inside the semiconductor wafer from the surface or back side of the semiconductor wafer;

[0249] Step 3: A semiconductor wafer with a protective sheet for semiconductor processing attached to its surface and the aforementioned trenches or modified regions formed thereon is ground from the back side, and is converted into multiple chips starting from the trenches or modified regions.

[0250] Step 4: The process of peeling the semiconductor processing protective film off the monolithized semiconductor wafer (i.e., multiple semiconductor chips).

[0251] The following is a detailed description of each step in the manufacturing method of the above-mentioned semiconductor device.

[0252] (Process 1)

[0253] In step 1, the semiconductor processing protective sheet of this embodiment is attached to the surface of a semiconductor wafer with unevenness via an adhesive layer. Because the semiconductor processing protective sheet of this embodiment has the aforementioned characteristics, it can adequately follow and embed the unevenness, thereby providing protection.

[0254] This process can be performed before or after process 2, which will be described later. For example, when forming a modified region in a semiconductor wafer, process 1 is preferably performed before process 2. On the other hand, when forming trenches on the surface of a semiconductor wafer by dicing or the like, process 1 is performed after process 2. That is, a semiconductor processing protective sheet is attached to the trenched wafer surface formed by process 2, which will be described later, through process 1.

[0255] The semiconductor wafer used in this manufacturing method can be a silicon wafer, or it can be a wafer made of gallium arsenide, silicon carbide, lithium tantalate, lithium niobate, gallium nitride, indium phosphide, or a glass wafer. The thickness of the semiconductor wafer before grinding is not particularly limited, but is typically around 500–1000 μm. Furthermore, circuits are typically formed on the surface of the semiconductor wafer. Circuits can be formed on the wafer surface using various conventional methods, including etching and lift-off. In particular, in this embodiment, convex electrodes (bumps) are formed on the circuit surface of the semiconductor wafer. As a result, compared to a semiconductor wafer without convex electrodes, there are uneven surfaces on the circuit surface of the semiconductor wafer. Additionally, the height of the convex electrodes is not particularly limited, but is typically 5–200 μm.

[0256] (Process 2)

[0257] In step 2, trenches are formed from the surface side of the semiconductor wafer, or modified regions are formed from the surface or back side of the semiconductor wafer inside the semiconductor wafer.

[0258] The trenches formed in this process are shallower than the thickness of the semiconductor wafer. Conventional wafer dicing equipment can be used to form the trenches by cutting. Furthermore, the semiconductor wafer is diced into multiple semiconductor chips along the trenches in process 3, described later.

[0259] Furthermore, the modified region is the brittle portion of the semiconductor wafer, marking the starting point for the individual semiconductor chips. In this individualization process, the semiconductor wafer is thinned through grinding during the polishing process, and the force generated by the polishing is applied, thereby breaking the semiconductor wafer and ultimately individualizing it into semiconductor chips. That is, the trenches and modified regions in process 2 are formed along the dividing lines used in the subsequent process 3 to segment the semiconductor wafer and then individualize it into semiconductor chips.

[0260] A modified region is formed by focusing laser irradiation on the interior of a semiconductor wafer. The laser irradiation can be performed from either the surface or the back side of the semiconductor wafer. Alternatively, in one method of forming the modified region, when step 2 is performed after step 1 and laser irradiation is performed from the wafer surface, the laser is irradiated onto the semiconductor wafer through a protective sheet used for semiconductor processing.

[0261] A semiconductor wafer, with a protective film for semiconductor processing attached and having trenches or modified regions formed thereon, is placed on a chuck table and held thereby. At this time, the surface side of the semiconductor wafer is positioned and held against the table side.

[0262] (Process 3)

[0263] After process 1 and process 2, the back side of the semiconductor wafer on the chuck table is ground to convert the semiconductor wafer into multiple semiconductor chips.

[0264] Here, when trenches are formed on a semiconductor wafer, back-side grinding is performed to thin the semiconductor wafer to at least reach the bottom of the trenches. Through this back-side grinding, the trenches are formed into cuts that penetrate the wafer, and the semiconductor wafer is divided through these cuts into individual semiconductor chips.

[0265] On the other hand, when a modified region is formed, the grinding surface (back side of the wafer) can reach the modified region through grinding, but it can also reach it imprecisely. That is, grinding can be done close to the modified region in a way that allows the semiconductor wafer to be broken down from the modified region and thus monolithically formed into a semiconductor chip. For example, the actual monolithization of the semiconductor chip can be performed by extending the pick-up tape after attaching the pick-up tape described later.

[0266] In addition, dry polishing can be performed after the back-side grinding is completed and before the chip is picked up.

[0267] The shape of the monolithic semiconductor chip can be square or rectangular and other elongated shapes. Furthermore, the thickness of the monolithic semiconductor chip is not particularly limited, but is preferably around 5 to 100 μm, more preferably 10 to 45 μm. Based on LDBG, which uses lasers to create modified regions inside the wafer and utilizes the stress during wafer back-side grinding for wafer monolithicization, it is easy to manufacture the thickness of the monolithic semiconductor chip to be less than 50 μm, more preferably 10 to 45 μm. Furthermore, the size of the monolithic semiconductor chip is not particularly limited, but the chip size is preferably less than 600 mm. 2 More preferably less than 400mm 2 Further preferred size is less than 120mm 2 .

[0268] If the semiconductor processing protective sheet of this embodiment is used, even for such a thin and / or small semiconductor chip, cracks can be prevented from forming on the semiconductor chip when the back side is polished (step 3) and when the semiconductor processing protective sheet is peeled off (step 4).

[0269] (Step 4)

[0270] Next, a protective film for semiconductor processing is peeled off from the monolithized semiconductor wafer (i.e., multiple semiconductor chips). This process is performed, for example, by the following method.

[0271] In this embodiment, the intermediate layer and adhesive layer of the semiconductor processing protective sheet are formed by an energy-curable adhesive. Therefore, irradiation with energy rays causes the intermediate layer and adhesive layer to cure and shrink, reducing the adhesion to the substrate (the monolithized semiconductor wafer). Next, a pick-up tape is attached to the back side of the monolithized semiconductor wafer, and its position and orientation are aligned in a pick-up manner. At this time, an annular frame disposed on the outer periphery of the wafer is also attached to the pick-up tape, fixing the outer periphery of the pick-up tape to the annular frame. The wafer and the annular frame can be attached to the pick-up tape simultaneously, or they can be attached at different times. Next, the semiconductor processing protective sheet is peeled off from the plurality of semiconductor chips held on the pick-up tape.

[0272] Because of the above-mentioned characteristics, the protective sheet for semiconductor processing in this embodiment can be easily peeled off and will not adhere to uneven, especially convex, electrodes.

[0273] Then, multiple semiconductor chips located on the pick-up tape are picked up and fixed onto a substrate or the like, thereby manufacturing a semiconductor device.

[0274] In addition, there are no special limitations on the pickup tape, for example, it can be composed of an adhesive sheet having a substrate and an adhesive layer disposed on one side of the substrate.

[0275] The above describes an example of applying the semiconductor processing protective sheet of this embodiment to a method of single-chip semiconductor wafer assembly using DBG or LDBG. However, the semiconductor processing protective sheet of this embodiment is preferably applied to LDBG, which can produce a chip assembly with a smaller cut width and thinner profile when single-chip semiconductor wafer assembly.

[0276] The embodiments of the present invention have been described above, but the present invention is not limited to any of the above embodiments and can be modified in various ways within the scope of the present invention.

[0277] Example

[0278] The present invention will be described in more detail below with reference to embodiments, but the present invention is not limited to these embodiments.

[0279] The testing and evaluation methods in this embodiment are as follows.

[0280] (Young's modulus of a protective sheet for semiconductor processing before energy-ray curing at 50°C)

[0281] At 50°C, in accordance with JIS K 7127 (1999), at a test speed of 200 mm / min, a tensile test was performed on the protective sheets for semiconductor processing manufactured in the examples and comparative examples before energy ray curing, and the Young's modulus was determined.

[0282] (DBG chip crack evaluation)

[0283] After trenches are formed on the surface of a 12-inch diameter silicon wafer, a semiconductor processing protective sheet manufactured in the examples and comparative examples is attached to the wafer surface. The wafer is then monolithically processed by grinding the back side, thereby monolithically processing the wafer into chips with a thickness of 50 μm and a chip size of 5 mm square by a pre-dicing method. Then, without removing the semiconductor processing protective sheet, the corners of the monolithically processed chips are observed from the ground surface of the wafer using a digital microscope (product name "VHX-1000", manufactured by KEYENCE CORPORATION) to observe whether each chip has cracks. The crack initiation rate of 700 chips is measured and evaluated according to the following evaluation criteria.

[0284] A: Less than 1.0%, B: 1.0–2.0%, C: Greater than 2.0%

[0285] (LDBG chip crack evaluation)

[0286] Using a back-grinding tape laminator (manufactured by LINTEC Corporation, device name "RAD-3510F / 12"), the semiconductor processing protective sheet manufactured in the examples and comparative examples was attached to a silicon wafer with a diameter of 12 inches and a thickness of 775 μm. A lattice-shaped modified region was formed on the wafer using a laser saw (manufactured by DISCO Corporation, device name "DFL7361"). The lattice size was 5 mm × 5 mm.

[0287] Next, a back-side grinding device (manufactured by DISCO Corporation, device name) was used.

[0288] The “DGP8761” is ground (including dry polishing) until the thickness is 50μm, thus converting the wafer into multiple chips.

[0289] After the grinding process, the semiconductor processing protective film is irradiated with energy rays (ultraviolet light). Cutting tape (manufactured by LINTEC Corporation, Adwill D-176) is then applied to the opposite side of the mounting surface of the protective film, and the protective film is peeled off. Then, a digital microscope (product name...) is used...

[0290] The “VHX-1000” (manufactured by KEYENCE CORPORATION) was used to observe individual chips, count the chips that developed cracks, determine the crack infestation rate among 700 chips, and evaluate them according to the following evaluation criteria.

[0291] A: Less than 1.0%, B: 1.0–2.0%, C: Greater than 2.0%

[0292] (Evaluation of absorbency of convex dots)

[0293] Using a laminator (product name "RAD-3510F / 12", manufactured by LINTEC Corporation), a semiconductor processing protective sheet manufactured in the following examples and comparative examples was attached to a wafer (8-inch wafer, manufactured by WALTZ Corporation) with spherical bumps. The spherical bumps had a bump height of 80 μm, a spacing of 200 μm, and a diameter of 100 μm, and were made of Sn-3Ag-0.5Cu alloy. Furthermore, during attachment, the temperature of the lamination table and lamination rollers of the apparatus was set to 50°C.

[0294] After lamination, the diameter of the circular gaps around the bumps was measured from the substrate side using a digital optical microscope (product name "VHX-1000", manufactured by KEYENCE CORPORATION).

[0295] The smaller the diameter of the gap, the higher the bump absorption of the protective sheet used in semiconductor processing. The following criteria are used to determine the quality of bump absorption.

[0296] ○: The diameter of the pore is less than 150μm.

[0297] ×: The diameter of the pore is 150μm or more.

[0298] (Evaluation of residual adhesive on the raised part)

[0299] Using a laminator (product name "RAD-3510F / 12", manufactured by LINTEC Corporation), a semiconductor processing protective sheet manufactured in the following examples and comparative examples was attached to a wafer (8-inch wafer, manufactured by WALTZ Corporation) with spherical bumps. The spherical bumps had a bump height of 80 μm, a spacing of 200 μm, and a diameter of 100 μm, and were made of Sn-3Ag-0.5Cu alloy. Furthermore, during attachment, the temperature of the lamination table and lamination rollers of the apparatus was set to 50°C.

[0300] After lamination, UV irradiation is applied from the semiconductor processing protective film side using a UV irradiation device (product name "RAD-2000m / 12", manufactured by LINTEC Corporation) at an irradiation speed of 15 mm / s. Next, the semiconductor processing protective film is peeled off from the evaluation wafer using a wafer laminator (product name "RAD-2700F / 12", manufactured by LINTEC Corporation) at a peeling speed of 4 mm / s and a temperature condition of 40°C. Using an electron microscope (product name "VE-9800", manufactured by KEYENCECORPORATION), the portion of the adhesive layer with embedded bumps on the peeled semiconductor processing protective film is observed at a 45° viewing angle to confirm whether the adhesive layer is cracked.

[0301] The quality of residual adhesive should be judged according to the following criteria.

[0302] A: No cracks (no residual adhesive).

[0303] B: There is a crack (with residual glue).

[0304] (Example 1)

[0305] (1) Substrate

[0306] Prepare a PET film (COSMOSHINE A4300 manufactured by TOYOBO CO.,LTD., thickness: 50μm, Young's modulus at 23℃: 2550MPa) with easy-to-adhere layers on both sides as the substrate.

[0307] (2) Buffer layer

[0308] (Synthesis of carbamate acrylate oligomers)

[0309] 2-hydroxyethyl acrylate is reacted with a terminal isocyanate urethane prepolymer to obtain a urethane acrylate oligomer (UA-1) with a weight average molecular weight (Mw) of about 5000. The terminal isocyanate urethane prepolymer is obtained by reacting a polyester diol with isophorone diisocyanate.

[0310] (Preparation of the composition for the buffer layer)

[0311] A composition for a buffer layer is prepared by mixing 50 parts by weight of the above-synthesized urethane acrylate oligomer (UA-1), 40 parts by weight of isobornyl acrylate (IBXA), and 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate (HPPA), and further mixing 1.0 part by weight of 2-hydroxy-2-methyl-1-phenyl-propane-1-one (manufactured by BASF Japan Ltd, product name "IRGACURE1173") as a photopolymerization initiator.

[0312] (Manufacturing of substrate with buffer layer)

[0313] A buffer layer composition is applied to the release treatment surface of another release sheet (manufactured by LINTEC Corporation, product name "SP-PET381031") to form a coating film. The coating film is then irradiated with ultraviolet light to semi-cur it, forming a buffer layer film with a thickness of 53 μm.

[0314] In addition, using a conveyor belt-type ultraviolet irradiation device (manufactured by EYE GRAPHICS Co., Ltd., device name "US2-0801") and a high-pressure mercury lamp (manufactured by EYE GRAPHICS Co., Ltd., device name "H08-L41"), the illuminance of light with a lamp height of 230mm, an output power of 80mW / cm, and a wavelength of 365nm was 90mW / cm. 2 The radiation dose is 50 mJ / cm. 2 Under the irradiation conditions described above, ultraviolet irradiation was carried out.

[0315] Next, the surface of the formed buffer layer film is bonded to the substrate, and ultraviolet light is irradiated again from the release liner side of the buffer layer film to completely cure the buffer layer film, forming a buffer layer with a thickness of 53 μm. Additionally, using the aforementioned ultraviolet irradiation device and high-pressure mercury lamp, the illuminance of light with a lamp height of 220 mm, a converted output power of 120 mW / cm, and a wavelength of 365 nm is 160 mW / cm². 2 The radiation dose was 650 mJ / cm.2 Under the irradiation conditions described above, ultraviolet irradiation was carried out.

[0316] (3) Substrate with intermediate layer

[0317] 91 parts by mass of n-butyl acrylate (BA) and 9 parts by mass of acrylic acid (AA) were copolymerized to obtain a non-energy-curable acrylic copolymer (a) (Mw: 600,000).

[0318] Unlike acrylic copolymers (a), acrylic polymers are obtained by copolymerizing 62 parts by mass of n-butyl acrylate (BA), 10 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA), and the copolymers contain 80% of the total hydroxyl groups (100 equivalents) of the acrylic polymer.

[0319] By adding an equivalent amount of hydroxyl groups, 2-methacryloyloxyethyl isocyanate (MOI) is reacted with an acrylic polymer to obtain an energy-curable acrylic copolymer (b) (Mw: 100,000).

[0320] To 100 parts by weight of the non-energy-curable acrylic copolymer (a), 13 parts by weight of the energy-curable acrylic copolymer (b) were added, along with 2.79 parts by weight of an isocyanate crosslinking agent (manufactured by TOSOH, product name "CORONATE L") and 3.71 parts by weight of 1-hydroxycyclohexylphenyl ketone (manufactured by BASF, Irgacure 184) as a photoinitiator. The solid content was adjusted to 37% using toluene, and the mixture was stirred for 30 minutes to prepare the composition for the intermediate layer.

[0321] Next, the prepared intermediate layer solution is coated onto a PET release film (manufactured by LINTEC Corporation, SP-PET381031, 38 μm thick) and dried to form an intermediate layer with a thickness of 55 μm. This intermediate layer is then bonded to the side of the substrate with the buffer layer opposite to the side where the buffer layer is formed. The intermediate layer solution is then repeatedly coated onto the PET release film (manufactured by LINTEC Corporation, SP-PET381031, 38 μm thick) three times to form a substrate with an intermediate layer and a thickness of 165 μm.

[0322] (4)Adhesive layer

[0323] (Preparation of the composition for the adhesive layer)

[0324] 52 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA) were copolymerized to obtain an acrylic polymer. 2-Methacryloxyethyl isocyanate (MOI) was then reacted with the acrylic polymer by adding 90 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to obtain an energy-curable acrylic copolymer (c) (Mw: 500,000).

[0325] To 100 parts by mass of the energy-curable acrylic copolymer (c), 12 parts by mass of a multifunctional urethane acrylate (manufactured by Mitsubishi Chemical Corporation, Shiko UT-4332), 1.1 parts by mass of an isocyanate crosslinking agent (manufactured by TOSOH CORPORATION, product name "CORONATEL"), and 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by BASF, Irgacure TPO) as a photopolymerization initiator were added, and the mixture was diluted with methyl ethyl ketone to prepare a coating liquid of an adhesive layer composition with a solid content concentration of 34% by mass.

[0326] (Manufacturing of protective wafers for semiconductor processing)

[0327] The above-mentioned adhesive layer composition is applied to the release surface of the release sheet (manufactured by LINTEC Corporation, product name "SP-PET381031") and then heated and dried to form an adhesive layer with a thickness of 10 μm on the release sheet.

[0328] Then, an adhesive layer is laminated onto the surface of the substrate with the intermediate layer to manufacture a protective sheet for semiconductor processing. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0329] (Example 2)

[0330] Except that the buffer layer is formed using the following buffer layer composition and the thickness of the intermediate layer is 120 μm, a protective sheet for semiconductor processing is obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0331] The product is a blend of 50 parts by weight of urethane acrylate oligomer (UA-1), 40 parts by weight of isobornyl acrylate (IBXA), 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate (HPPA), and 10 parts by weight of pentaerythritol triacrylate (PETA), further blended with 2-hydroxy-2-methyl-1-phenyl-propane-1-one (manufactured by BASF Japan Ltd., product name) as a photopolymerization initiator.

[0332] 1.0 parts by weight of “IRGACURE1173” are used to prepare a composition for preparing a buffer layer.

[0333] (Example 3)

[0334] Except that the thickness of the intermediate layer is 240 μm, a protective sheet for semiconductor processing is obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0335] (Example 4)

[0336] Except for changing the substrate with a buffer layer in Example 1 to the substrate with a buffer layer described below, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0337] A low-density polyethylene film (thickness: 27.5 μm) was prepared as a buffer layer. The buffer layer was then laminated on both sides of the substrate used in Example 1 using a dry lamination method to obtain a substrate with a buffer layer consisting of LDPE / PET / LDPE laminated sequentially.

[0338] (Example 5)

[0339] Except that the substrate with the buffer layer in Example 1 was changed to the PET substrate of Example 1, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. That is, no buffer layer was formed on the substrate. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0340] (Comparative Example 1)

[0341] Except that the substrate with the buffer layer in Example 1 was changed to an EVA film substrate (FUNCRARE LEAG 120 manufactured by GUNZE LIMITED), the amount of acrylic copolymer (b) added to the intermediate layer composition was changed to 67 parts by mass, the thickness of the intermediate layer was set to 100 μm, and the following adhesive layer composition was used as the adhesive layer composition, a protective sheet for semiconductor processing was obtained by the same method as in Example 1. That is, no buffer layer was formed on the substrate. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0342] 70 parts by weight of n-butyl acrylate (BA), 15 parts by weight of isobutyl acrylate (iBA),

[0343] 5 parts by mass of methyl methacrylate (MMA) and 10 parts by mass of 4-hydroxybutyl acrylate (4HBA) were copolymerized to obtain an acrylic polymer. 2-Methacryloxyethyl isocyanate (MOI) was reacted with the acrylic polymer by adding 90 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to obtain an energy-curable acrylic copolymer (d) (Mw: 500,000).

[0344] To 100 parts by weight of the energy-ray curable acrylic copolymer (d), 1.8 parts by weight of an isocyanate crosslinking agent (manufactured by TOSOH CORPORATION, product name "CORONATE L") and 7.29 parts by weight of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, Irgacure 651) as a photopolymerization initiator were added, and the mixture was diluted with toluene to prepare a coating liquid of an adhesive composition with a solid content concentration of 25% by weight.

[0345] (Comparative Example 2)

[0346] Except for using a substrate with an intermediate layer manufactured as described below and using the following adhesive layer composition as the adhesive layer composition, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0347] Substrate with intermediate layer

[0348] The UV-curable resin composition was prepared by mixing 40 parts by weight of monofunctional urethane acrylate (solid content ratio), 45 parts by weight of isobornyl acrylate (IBXA) (solid content ratio), 15 parts by weight of hydroxypropyl acrylate (HPA) (solid content ratio), 3.5 parts by weight of pentaerythritol tetrakis(3-mercaptobutyric acid) (product name "KARENZ MT PE1", manufactured by SHOWA DENKO KK, tetrafunctional secondary thiol compound, solid content concentration 100 parts by weight), 1.8 parts by weight of UV reactive thermal crosslinking agent, and 1.0 part by weight of 2-hydroxy-2-methyl-1-phenyl-propane-1-one (product name "Darocur 1173", manufactured by BASF, solid content concentration 100 parts by weight) as a photopolymerization initiator. The mixture was then sprayed into a fountain. The coating is applied to a polyethylene terephthalate (PET) film-type release liner (manufactured by LINTEC Corporation, SP-PET381031, 38μm thick) with a cured thickness of 400μm using a die-on method. Ultraviolet light is then irradiated from the coating side to form a semi-cured layer.

[0349] In addition, a conveyor belt-type ultraviolet irradiation device (product name "ECS-401GX", manufactured by EYE GRAPHICS Co., Ltd.) was used as the ultraviolet irradiation device, and a high-pressure mercury lamp (H04-L41, manufactured by EYE GRAPHICS Co., Ltd.) was used as the ultraviolet source. Under the irradiation conditions, the illuminance of light with a wavelength of 365nm was 112mW / cm². 2 The light intensity is 177 mJ / cm² 2 Under conditions of ultraviolet irradiation (measured by “UVPF-A1” manufactured by EYEGRAPHICS Co., Ltd.).

[0350] A polyethylene terephthalate (PET) film (Lumirror 75U403, 75 μm thick, manufactured by TORAY INDUSTRIES, INC.) was laminated onto the formed semi-cured layer, and ultraviolet light was further irradiated from the PET film side (using the aforementioned ultraviolet irradiation device and ultraviolet source, with an irradiation condition of 271 mW / cm²). 2 The light intensity is 1200 mJ / cm² 2 This process allows the material to fully cure, forming a 400μm thick intermediate layer on the PET film of the substrate.

[0351] 60 parts by weight of 2-ethylhexyl acrylate (2EHA), 15 parts by weight of ethyl acrylate (EA),

[0352] 5 parts by mass of methyl methacrylate (MMA) and 20 parts by mass of 2-hydroxyethyl acrylate (2HEA) were copolymerized to obtain an acrylic polymer. 2-Methacryloxyethyl isocyanate (MOI) was then reacted with the acrylic polymer by adding 60 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to obtain an energy-curable acrylic copolymer (e) (Mw: 500,000).

[0353] To 100 parts by weight of the energy-ray curable acrylic copolymer (e), 1.2 parts by weight of an isocyanate crosslinking agent (manufactured by TOSOH CORPORATION, product name "CORONATE L") and 7.29 parts by weight of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, Irgacure 651) as a photopolymerization initiator were added, and the mixture was diluted with toluene to prepare a coating liquid of an adhesive composition with a solid content concentration of 25% by weight.

[0354] (Comparative Example 3)

[0355] Except that the composition for the intermediate layer does not contain acrylic copolymers (b), a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0356] (Comparative Example 4)

[0357] Except that the thickness of the intermediate layer is 300 μm, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and the adhesive layer are shown in Table 1.

[0358] [Table 1]

[0359]

[0360] The obtained samples (Examples 1-5 and Comparative Examples 1-4) were subjected to the above-described measurements and evaluations. The results are shown in Table 2.

[0361] [Table 2]

[0362]

[0363] As can be confirmed from Table 2, when the Young's modulus of the protective sheet for semiconductor processing is within the above range and the intermediate layer contains a UV-curable compound, even when the wafer with bumps is monolithically processed by DBG and LDBG, the bumps can be fully embedded, the crack generation rate caused by chip displacement is low, and it can have both the embedding of bumps and the peeling ability from bumps.

Claims

1. A protective sheet for semiconductor processing, comprising a substrate and having an intermediate layer and an adhesive layer sequentially formed on one main surface of the substrate. The intermediate layer and the adhesive layer are energy-cured by radiation. The Young's modulus of the protective sheet for semiconductor processing before energy ray curing at 50°C is between 600 MPa and 1800 MPa.

2. The protective sheet for semiconductor processing according to claim 1, wherein, A buffer layer is provided on another main surface of the substrate.

3. The protective sheet for semiconductor processing according to claim 1 or 2, wherein, The Young's modulus of the substrate is above 1000 MPa.

4. The protective sheet for semiconductor processing according to claim 1 or 2, wherein, The thickness of the intermediate layer is between 60 μm and 250 μm.

5. The protective sheet for semiconductor processing according to claim 1 or 2, wherein, In the process of grinding the back side of a semiconductor wafer with trenches formed on its surface and then grinding the semiconductor wafer to form individual semiconductor chips, the semiconductor processing protective sheet is attached to the surface of the semiconductor wafer for use.

6. A method for manufacturing a semiconductor device, comprising: The process of attaching a protective sheet for semiconductor processing according to any one of claims 1 to 5 to the surface of a semiconductor wafer having uneven surfaces; The process of forming trenches from the surface side of the semiconductor wafer, or the process of forming a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer; A process of grinding a semiconductor wafer with the semiconductor processing protective film attached to its surface and the trenches or modified regions formed therein, starting from the back side, to convert the wafer into multiple chips from the trenches or modified regions. and The process of peeling the protective sheet for semiconductor processing from a single semiconductor chip.

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