Wafer processing tape and wafer processing method

Abstract

The objective is to provide a wafer processing tape that is less prone to void formation in the adhesive layer during the heating process, and that can sufficiently reduce the adhesive strength when the adhesive layer is irradiated with ultraviolet light during the peeling process, and that can be used transversely in semiconductor processing, as well as a wafer processing method that enables the integration of multiple semiconductor processing processes by using this tape. [Solution] A wafer processing tape comprising a base layer and an adhesive layer disposed on at least one side of the base layer, wherein the adhesive layer contains a photopolymerization initiator with a molecular weight of 350 or more.

Description

Technical Field

[0001] The present invention relates to a tape for wafer processing and a wafer processing method.

Background Art

[0002] When processing a semiconductor wafer, an adhesive sheet is attached to protect it from damage. For example, in the back grinding process when processing a semiconductor wafer, an adhesive sheet is attached to protect the pattern surface of the semiconductor wafer. In addition, in semiconductor processing, various tapes are used in each process, such as back grinding tape, heat-resistant tape, conductive tape, dicing tape, pickup tape, etc.

[0003] As an example, for the purpose of enhancing the adhesion of a substrate to a stage in a semiconductor wafer processing step, a substrate used for an adhesive sheet for processing a semiconductor wafer having a heat shrinkage rate of 0% or more in both MD and TD after heating at 130°C for 10 minutes is known (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In semiconductor processing, different tapes are used in each process because the characteristics required for the wafer processing tape are different in each process. However, since the wafer processing tape needs to be replaced after each process, there is a problem that the number of man-hours in the semiconductor processing step increases and it becomes complicated.

[0006] The present invention has been made in view of the above problems, and aims to provide a wafer processing tape that is less likely to generate voids in the adhesive layer during the heating process, can sufficiently reduce the adhesive strength when the adhesive layer is irradiated with ultraviolet light during the peeling process, can be used transversely in semiconductor processing, and a wafer processing method that enables the integration of multiple semiconductor processing processes by using the tape. [Means for solving the problem]

[0007] In other words, the present invention is as follows: [1] A base layer and The base layer has an adhesive layer disposed on at least one side, The adhesive layer contains a photopolymerization initiator with a molecular weight of 350 or more. Tape for wafer processing. [2] The temperature at which the photopolymerization initiator loses 10% of its weight is 200-300°C. [1] Wafer processing tape as described in [1]. [3] The adhesive force N1 of the adhesive layer to the silicon wafer after heating at 250°C for 5 minutes is 0.5 to 7.0 N / 25 mm at 25°C. The wafer processing tape described in [1] or [2]. [4] After heating at 250°C for 5 minutes and then UV irradiation, the adhesive strength N2 of the adhesive layer to the silicon wafer is 0.01 to 1.0 N / 25 mm at 25°C. A wafer processing tape as described in any one of items [1] to [3]. [5] The adhesive layer further comprises an acrylic resin having a polymerizable double bond with a hydroxyl group or a carboxyl group, or a crosslinked structure derived from the acrylic resin. A wafer processing tape as described in any one of items [1] to [4]. [6] The adhesive layer further comprises an epoxy crosslinking agent or a crosslinked structure derived from the epoxy crosslinking agent. A wafer processing tape as described in any one of items [1] to [5]. [7] The aforementioned substrate layer contains a polyamide resin. A wafer processing tape as described in any one of items [1] to [6]. [8] The aforementioned substrate layer does not have a yield point. A wafer processing tape as described in any one of items [1] to [7]. [9] The ultraviolet transmittance of the substrate layer at 365 nm is 70% or more. A wafer processing tape as described in any one of items [1] to [8].

[10] A processing step comprising attaching a wafer processing tape described in any one of items [1] to [9] to a wafer and performing wafer processing, Wafer processing method. [Effects of the Invention]

[0008] According to the present invention, a wafer processing tape is available that is less prone to void formation in the adhesive layer during the heating process, and that can sufficiently reduce the adhesive strength when the adhesive layer is irradiated with ultraviolet light during the peeling process, and that can be used transversely in semiconductor processing. Furthermore, a wafer processing method is available that enables the integration of multiple semiconductor processing steps by using this tape. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing the wafer processing tape of this embodiment. [Figure 2] This is a flowchart showing the wafer processing method of this embodiment. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. However, the present invention is not limited thereto, and various modifications are possible without departing from the gist thereof. In the drawings, the same reference numerals will be assigned to the same elements, and redundant descriptions will be omitted. Also, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0011] 1. Wafer processing tape The wafer processing tape of the present embodiment has a base material layer and an adhesive layer disposed on at least one surface side of the base material layer, and the adhesive layer contains a photoinitiator having a molecular weight of 350 or more (hereinafter also referred to as "high molecular weight photoinitiator").

[0012] FIG. 1 shows a schematic cross-sectional view of the wafer processing tape of the present embodiment. As shown in FIG. 1, the wafer processing tape 10 of the present embodiment has a base material layer 11 and an adhesive layer 12, and may have other layers as needed. By the surface 12a (exposed surface) of the adhesive layer 12 adhering to the element formation surface 20a on which the semiconductor element of the wafer 20 is formed, the semiconductor element on the element formation surface 20a of the wafer 20 can be protected. In the present embodiment, in the wafer processing tape and each of its layers, the surface on the side in contact with the wafer is referred to as the front surface, and the opposite surface is referred to as the back surface.

[0013] Figure 2 shows a flowchart illustrating one embodiment of the wafer processing method of this embodiment in a schematic cross-sectional view. As shown in Figure 2, the wafer processing method may include a bonding step S1 in which the wafer processing tape 10 is bonded to the element formation surface 20a of the wafer 20; a back grinding step S2 in which the non-element formation surface 20b of the wafer 20 bonded to the wafer processing tape 10 is polished with a grinder 40; a metal layer formation step S3 in which a metal layer 21 is formed on the non-element formation surface 20b opposite to the surface to which the wafer processing tape 10 is bonded; a dicing step S4 in which the wafer 20 bonded to the wafer processing tape 10 is diced to produce a chip 30; a processing step S5 in which surface treatment is applied to the back surface of the chip 30 by etching or sputtering or reflow treatment; and a peeling step S6 in which the wafer processing tape is peeled off.

[0014] Note that Figure 2 is an example of a wafer processing method, and it is not necessary to perform all of steps S2 to S5 in the wafer processing method, nor is the order of the steps limited to those specified in Figure 2. Therefore, for example, the metal layer formation step S3 may be omitted, or the processing step S5 may be omitted, or the processing step S5 may be performed before the dicing step S4.

[0015] Incidentally, it has been found that voids can form in the adhesive layer during heating processes such as the metal layer formation process S3 and the processing process S5. These voids in the adhesive layer may reduce adhesion to the wafer, and if the thickness of the adhesive layer becomes uneven due to the voids, it may also affect the accuracy of wafer processing.

[0016] In contrast, the wafer processing tape 10 of this embodiment uses a high molecular weight photopolymerization initiator. This suppresses the volatilization of the photopolymerization initiator contained in the adhesive layer during heating processes, preventing the formation of voids. Furthermore, because the photopolymerization initiator is less likely to volatilize during heating processes, the polymerization reaction proceeds smoothly when the adhesive layer is irradiated with ultraviolet light, thus reducing the adhesive strength. As a result, in the peeling process S6, peeling can be performed without causing adhesive residue or pickup failures.

[0017] As described above, the wafer processing tape of this embodiment suppresses the generation of voids in processes requiring heating, and can sufficiently reduce the adhesive strength when the adhesive layer is irradiated with ultraviolet light in the subsequent peeling process. Therefore, there is no need to change the wafer processing tape according to each process in wafer processing, and it can be used across the wafer processing method as shown in Figure 2. The composition of each layer will be described in detail below.

[0018] 1.1. Base material layer The substrate layer 11 conforms to the irregularities of the wafer 20, protecting it from damage during the wafer processing process, and also contributes to improved adhesion by preventing gaps from forming between the adhesive layer and the element formation surface 20a.

[0019] The base layer preferably contains a resin, and the resin is not particularly limited, but examples include polyamide resins, ionomer resins, polyolefin resins, vinyl chloride resins, polyester resins, polystyrene resins, phenolic resins, and acrylic resins. These resins may be used individually or in combination of two or more. More specifically, the resins may be mixtures, copolymers, or laminates of one resin with another.

[0020] Among these, polyamide resins, ionomer resins, and polyolefin resins are preferred, with polyamide resins being more preferred. Using such resins tends to improve the wafer's conformability to irregularities, heat resistance, and ultraviolet transmittance.

[0021] The polyamide resin is not particularly limited, but examples include aliphatic polyamides such as polyamide 6 and polyamide 66; semi-aromatic polyamides such as polyamide 6T, polyamide 9T, and polyamide 10T; and fully aromatic polyamides obtained from aromatic dicarboxylic acids and aromatic diamines. Note that aliphatic polyamides may also have alicyclic groups in addition to aliphatic groups.

[0022] The ionomer resin is not particularly limited as long as it is a polymer in which metal ions are intermolecularly bonded, but examples include polyolefin-based ionomers, (meth)acrylic-based ionomers, polystyrene-based ionomers, and polyester-based ionomers. The metal ions that constitute the salt of the ionomer resin are not particularly limited, but examples include monovalent metal ions such as sodium ions and lithium ions; divalent metal ions such as zinc ions, calcium ions, and magnesium ions; and trivalent metal ions such as aluminum ions.

[0023] The polyolefin resin is not particularly limited, but examples include polyethylene, polypropylene, and copolymers thereof.

[0024] The resin content is preferably 80-100% by mass, 85-100% by mass, or 90-100% by mass, relative to the total amount of the substrate layer.

[0025] The base layer may contain additives other than resin, as needed. While not particularly limited, examples of additives include plasticizers, heat stabilizers, colorants, organic lubricants, inorganic lubricants, surfactants, processing aids, and antistatic agents. Additives may be used individually or in combination of two or more.

[0026] It is preferable that the base layer does not have a yield point. In this embodiment, "yield point" refers to the first point in the stress-strain curve where strain increases without an increase in stress. "Having no yield point" means that there is no point in the stress-strain curve where strain increases without an increase in stress. The stress-strain curve can be measured in accordance with JIS K 7161, and the yield point can be identified from the stress-strain curve measured in this manner.

[0027] Resins without a yield point are not particularly limited, but examples include polystyrene resin, acrylic resin, phenolic resin, and polyamide resin.

[0028] The ultraviolet transmittance of the substrate layer at 365 nm is preferably 70% or more, 80-99.5%, and 85-99%. A ultraviolet transmittance of 70% or more allows the adhesive layer 12 to be cured by irradiating it with ultraviolet light from the back surface 11b of the substrate layer, which tends to improve the peelability of the wafer 20 from the adhesive layer 12 during the peeling process.

[0029] The ultraviolet transmittance at 365 nm may also be measured by using a UV-Vis spectrophotometer to measure the light transmittance of the substrate in the wavelength range of 300 nm to 800 nm, and then reading the light transmittance at 365 nm from the obtained measurement results.

[0030] The thickness of the substrate layer is preferably 10 to 500 μm, 15 to 250 μm, or 25 to 100 μm. When the thickness of the substrate layer is within the above range, the ability to follow the irregularities of the wafer is further improved, and gaps such as voids are less likely to enter between the wafer processing tape and the element formation surface, which tends to improve adhesion.

[0031] 1.2. Adhesive layer The adhesive layer 12 is a layer laminated on the surface 11a side of the substrate layer 11. During the semiconductor processing process, the adhesive layer 12 adheres closely to the wafer 20, protecting the element formation surface 20a, and can be peeled off after semiconductor processing without leaving any adhesive residue.

[0032] It is preferable that the adhesive layer's adhesive strength is reduced by ultraviolet irradiation. This allows the layer to adhere closely to the wafer 20 and protect the element formation surface 20a from the bonding process S1 to the dicing process S4, and then, in the subsequent peeling process, the adhesive strength is reduced by ultraviolet irradiation, allowing the chip to be picked up without any adhesive residue.

[0033] In particular, in this embodiment, a high molecular weight photopolymerization initiator with a molecular weight of 350 or more is used, from the viewpoint of effectively reducing adhesiveness even when ultraviolet irradiation is performed after a heating process. By including a high molecular weight photopolymerization initiator, the photopolymerization initiator does not volatilize during the heating process, suppressing the generation of voids, and in the peeling process, the reaction by radicals, etc., proceeds due to ultraviolet irradiation.

[0034] Furthermore, since such a reaction effectively reduces the adhesive strength, the adhesive layer may contain a base polymer having polymerizable double bonds and crosslinkable groups, and a crosslinking agent. In addition, in the adhesive layer, the crosslinkable groups of the base polymer and the crosslinking agent may react to form a three-dimensional crosslinked structure. As a result, when irradiated with ultraviolet light, the high molecular weight photopolymerization initiator causes the three-dimensional crosslinked structure or the polymerizable double bonds of the base polymer to bond together, forming a crosslinked structure. This effectively reduces the adhesive strength of the adhesive layer.

[0035] Furthermore, when the base polymer and crosslinking agent form a three-dimensional crosslinked structure, the photopolymerization initiator becomes the main small molecule in the adhesive layer. Each component is described in detail below.

[0036] The base polymer constituting the main component of the adhesive layer is not particularly limited, but examples include (meth)acrylic acid ester copolymers. The shape of the (meth)acrylic acid ester copolymer is not particularly limited, but examples include linear, branched, or crosslinked shapes. Among these, having a crosslinked shape is preferred. By using such a base polymer, the physical properties of the adhesive layer can be adjusted. The base polymer having a crosslinked or branched shape may be formed by bonding epoxy groups, etc., of a base polymer having a linear or branched shape via a crosslinking agent described later.

[0037] The monomers constituting the (meth)acrylic acid ester copolymer are not particularly limited, but examples include alkyl (meth)acrylic acid esters having an alkyl group with 1 to 3 carbon atoms, (meth)acrylic acid esters having a glycidyl group, (meth)acrylic acid esters having a hydroxyl group, and monomers having an aromatic group. In addition, the (meth)acrylic acid ester copolymer may also contain copolymerizable vinyl monomers other than acrylic monomers.

[0038] The alkyl (meth)acrylate ester having an alkyl group with 1 to 3 carbon atoms is not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate.

[0039] The (meth)acrylic acid ester having a glycidyl group is not particularly limited, but examples include glycidyl (meth)acrylate and allyl glycidyl ether. The constituent units derived from the (meth)acrylic acid ester having a glycidyl group may be used for the purpose of introducing epoxy groups into the base polymer. The epoxy groups introduced into the base polymer react with the crosslinking agent described later, causing the base polymers to bond to each other and become three-dimensionally crosslinked.

[0040] The (meth)acrylic acid ester having a hydroxyl group is not particularly limited, but examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, pentaerythritol triacrylate, glycidol di(meth)acrylate, and dipentaerythritol pentaacrylate. The constituent units derived from the (meth)acrylic acid ester having a hydroxyl group may be used for the purpose of introducing epoxy groups into the base polymer. The hydroxyl groups introduced into the base polymer react with the crosslinking agent described later, causing the base polymers to bond to each other and become three-dimensionally crosslinked.

[0041] The monomers having aromatic groups are not particularly limited, but examples include styrene, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate.

[0042] Among these, an acrylic resin having a polymerizable double bond with a hydroxyl group or a carboxyl group is preferred as the base polymer, and the adhesive layer preferably contains a crosslinked structure derived from the acrylic resin. By including such a base polymer and a crosslinked structure derived therefrom, the adhesiveness tends to be further improved before UV irradiation, and the peelability tends to be further improved after UV irradiation.

[0043] The glass transition temperature of the base polymer is preferably -90 to -30°C, -80 to -40°C, or -70 to -50°C. Furthermore, having the glass transition temperature of the base polymer within these ranges tends to make it easier to adjust the adhesive strength.

[0044] The base polymer content is preferably 85-99% by mass, 90-98% by mass, or 92-97% by mass, relative to the total amount of the adhesive layer.

[0045] The crosslinking agent is not particularly limited as long as it has two or more functional groups that react with crosslinkable groups such as carboxyl groups and hydroxyl groups of the base polymer.

[0046] Such crosslinking agents are not particularly limited, but examples include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isocyanurate of hexamethylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, trim Isocyanate crosslinking agents such as tyrolpropane tolylene diisocyanate adduct, trimethylolpropane xylylene diisocyanate adduct, triphenylmethane triisocyanate, and methylenebis(4-phenylmethane) triisocyanate; N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, bisphenol A·epichlorohydrin type epoxy resins, and N,N'-[1,3-phenylenebis(methylene)]bis[bis(oxiran-2-yl] Epoxy crosslinking agents such as methylamine, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, etc.; tetramethylolmethane-tri-β-agile Examples include aziridine crosslinking agents such as dinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide); and melamine crosslinking agents such as hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexasubtoxymethylmelamine, hexapentyloxymethylmelamine, and hexahexyloxymethylmelamine.

[0047] Among these, epoxy crosslinking agents and isocyanate crosslinking agents are preferred, with epoxy crosslinking agents being more preferred. By using an epoxy crosslinking agent, the base polymers can be crosslinked with highly heat-resistant ester bonds. Due to the inclusion of a crosslinked structure derived from the epoxy crosslinking agent, the adhesive layer can exhibit good heat resistance even in processes exposed to high temperatures, such as the metal layer formation process S3, and voids tend to be suppressed.

[0048] The crosslinking agent content is preferably 1.0 to 6.0 parts by mass, 2.0 to 5.0 parts by mass, or 3.0 to 4.0 parts by mass per 100 parts by mass of the base polymer. When the crosslinking agent content is within the above range, voids tend to be more suppressed in the adhesive layer during the heating process.

[0049] First, examples of conventionally known photopolymerization initiators will be given. Conventionally known photopolymerization initiators are not particularly limited as long as they are initiators that generate active species such as radicals, but for example, benzophenone and its derivatives; benzoin-type photopolymerization initiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isobutyl ether, and benzyldimethyl ketal; acetophenone-type photopolymerization initiators such as diethoxyacetophenone and 4-tert-butyltrichloroacetophenone; thioxanthone and its derivatives; camphorquinone, 7 Camphorquinone-type photopolymerization initiators such as 7-dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carboxylic acid, 7,7-dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carboxy-2-bromoethyl ester, 7,7-dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carboxy-2-methyl ester, and 7,7-dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carboxylic acid chloride; 2-methyl-1-[4-(methylthio)phenyl] α-aminoalkylphenone type photopolymerization initiators such as -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1; benzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzoyl diethoxyphosphine oxide, 2,4,6-trimethylbenzoyl dimethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyl diethoxyphenylphosphine oxide, Examples include acylphosphine oxide type photopolymerization initiators such as s(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and α-hydroxyalkylphenone type photopolymerization initiators such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]propan-1-one, 1-hydroxycyclohexylphenyl ketone, and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propan-1-one.

[0050] In this embodiment, in particular, a photopolymerization initiator with a molecular weight of 350 or more is used. This suppresses the generation of voids caused by the volatilization of the photopolymerization initiator during heating processes, and also allows for a sufficient reduction in adhesive strength when the adhesive layer is irradiated with ultraviolet light during the subsequent peeling process.

[0051] Among these, acylphosphine oxide type photopolymerization initiators are preferred as photopolymerization initiators with a molecular weight of 350 or more. Using such photopolymerization initiators results in excellent polymerization properties and a tendency for tackiness to decrease when irradiated with ultraviolet light.

[0052] The 10% weight loss temperature of the high molecular weight photopolymerization initiator is preferably 200-300°C, 220-280°C, or 240-260°C. Having the 10% weight loss temperature of the high molecular weight photopolymerization initiator within this range makes it less likely for voids to form in the adhesive layer during the heating process, and also tends to reduce the adhesive strength when the adhesive layer is irradiated with ultraviolet light during the peeling process.

[0053] The 10% weight loss temperature of a high molecular weight photopolymerization initiator can be measured in accordance with JIS K 7120. Alternatively, the 10% weight loss temperature may be adjusted depending on the molecular weight of the high molecular weight photopolymerization initiator.

[0054] The molecular weight of the high molecular weight photopolymerization initiator is 350 or higher, preferably 375 to 1000, and 400 to 600. Having a molecular weight of 350 or higher in the high molecular weight photopolymerization initiator tends to reduce the likelihood of voids forming in the adhesive layer during the heating process, and also allows for a sufficient reduction in adhesive strength when the adhesive layer is irradiated with ultraviolet light during the peeling process.

[0055] The content of the photopolymerization initiator with a molecular weight of 350 or more is preferably 1.0 to 5.0 parts by mass, 1.5 to 4.0 parts by mass, or 2.0 to 3.0 parts by mass per 100 parts by mass of the base polymer. When the content of the photopolymerization initiator is within the above range, the curing reaction proceeds effectively when irradiated with ultraviolet light, and the adhesive strength tends to decrease further.

[0056] Furthermore, when the adhesive layer contains a photopolymerization initiator with a molecular weight of less than 350, the content of the photopolymerization initiator with a molecular weight of 350 or more is preferably 70% by mass or more, 80% by mass or more, and 90% by mass or more, relative to the total amount of photopolymerization initiators. In addition, there is no particular upper limit to the content of the photopolymerization initiator with a molecular weight of 350 or more, but it is 99% by mass or less. This tends to make it less likely for voids to occur in the adhesive layer during the heating process, and to sufficiently reduce the adhesive strength when the adhesive layer is irradiated with ultraviolet light during the peeling process.

[0057] The adhesive force N0 of the adhesive layer to the silicon wafer before heating is preferably 0.2 to 5.0 N / 25 mm, 0.3 to 2.5 N / 25 mm, 0.4 to 1.0 N / 25 mm, and 0.5 to 0.8 N / 25 mm at 25°C. By having the adhesive force N0 of the adhesive layer to the silicon wafer within the above range, the element formation surface of the wafer 20 can be protected more appropriately.

[0058] The adhesive force N1 of the adhesive layer to the silicon wafer after heating at 250°C for 5 minutes is preferably 0.5 to 7.0 N / 25 mm, 0.7 to 6.0 N / 25 mm, 1.0 to 5.0 N / 25 mm, and 1.1 to 4.0 N / 25 mm at 25°C. By having the adhesive force N1 of the adhesive layer to the silicon wafer within the above range, adhesion can be maintained even at high temperatures, and the element formation surface of the wafer 20 can be more appropriately protected.

[0059] After heating at 250°C for 5 minutes and then UV irradiation, the adhesive strength N2 of the adhesive layer to the silicon wafer is preferably 0.01 to 1.0 N / 25 mm, 0.03 to 0.80 N / 25 mm, 0.05 to 0.60 N / 25 mm, 0.07 to 0.40 N / 25 mm, and 0.08 to 0.20 N / 25 mm at 25°C. Because the adhesive strength N2 of the adhesive layer to the silicon wafer is within the above range, even when UV irradiation is performed after a heating process, the high molecular weight photopolymerization initiator functions and the crosslinking reaction proceeds, and the adhesive strength can be sufficiently reduced, which tends to further improve peelability.

[0060] The ratio of adhesive strength N1 to adhesive strength N0 (N1 / N0) is preferably 1.0 to 4.0, 1.2 to 3.5, 1.4 to 3.0, or 1.6 to 2.5. When the ratio (N1 / N0) is within the above range, good adhesion tends to be maintained before and after the heating process.

[0061] The ratio of adhesive strength N2 to adhesive strength N1 (N2 / N1) is preferably 0.01 to 0.30, 0.02 to 0.20, or 0.03 to 0.10. When the ratio (N2 / N1) is within the above range, the adhesive strength tends to be sufficiently reduced when the adhesive layer is irradiated with ultraviolet light during the peeling process.

[0062] The adhesive strengths N0 to N2 can be measured according to JIS Z 0237 (2009). Furthermore, the adhesive strengths N0 to N2 can be adjusted by the type and amount of high molecular weight photopolymerization initiator, base polymer, and crosslinking agent used. In addition, the adhesive strengths N0 to N2 can also be adjusted by the method of forming the adhesive layer. For example, by heat treatment at 100 to 200°C for 1 to 30 minutes, followed by aging treatment at 30 to 70°C for 1 to 7 days, the reaction between the base polymer and the crosslinking agent proceeds sufficiently, thereby adjusting the adhesive strengths N0 to N2 and their ratios.

[0063] The thickness of the adhesive layer is preferably 0.2 to 100 μm, 0.5 to 50 μm, 0.7 to 25 μm, or 1.0 to 20 μm. Having a thickness within these ranges tends to minimize interference with conformability and reduce adhesive residue.

[0064] 2. Method for manufacturing wafer processing tape The method for manufacturing the wafer processing tape of this embodiment is not particularly limited, but is not particularly limited as long as it includes a step of forming an adhesive layer 12 on the surface 11a of the base layer 11.

[0065] The method for forming the adhesive layer 12 is not particularly limited, but for example, the films may be dry-laminated together, or the composition may be coated onto the surface of the base layer 11, and the composition may be dried or photocured to form the adhesive layer 12. Alternatively, the adhesive layer 12 may be bonded to the base layer 11 via an adhesive layer different from the adhesive layer 12.

[0066] 3. Wafer Processing Method The wafer processing method of this embodiment includes a processing step of attaching the wafer processing tape to a wafer and performing wafer processing.

[0067] As shown in Figure 2, the wafer processing method may include a bonding step S1 in which the wafer processing tape 10 is bonded to the element formation surface 20a of the wafer 20; a back grinding step S2 in which the non-element formation surface 20b of the wafer 20 bonded to the wafer processing tape 10 is polished with a grinder 40; a metal layer formation step S3 in which a metal layer 21 is formed on the non-element formation surface 20b opposite to the surface to which the wafer processing tape 10 is bonded; a dicing step S4 in which the wafer 20 bonded to the wafer processing tape 10 is diced to produce a chip 30; a processing step S5 in which the back surface of the chip 30 is surface treated by etching or sputtering or reflow treatment; and a peeling step S6 in which the wafer processing tape is peeled off.

[0068] 3.1.Lamination process The bonding step S1 is a step of bonding the wafer processing tape 10 to the element formation surface 20a of the wafer 20. The surface of the wafer 20 to which the wafer processing tape 10 is bonded may be the non-element formation surface 20b.

[0069] In the bonding process, the wafer processing tape 10 may be bonded to the wafer main surface 20a after being preheated, or it may be bonded to the wafer main surface 20a and then heated. Alternatively, the wafer processing tape 10 may be bonded to the wafer main surface 20a without heating. By bonding the surface 11a of the adhesive layer 12 to the element formation surface 20a of the wafer while heated, the surface 11a of the adhesive layer 12 can be bonded in a state where it follows the element formation surface 20a of the wafer (see S2 in Figure 2). In this way, the protrusions are embedded in the wafer processing tape 10, thereby protecting the element formation surface 20a of the wafer that has the protrusions.

[0070] The heating temperature is preferably 60 to 150°C, more preferably 70 to 140°C, and even more preferably 80 to 130°C. The heating time for the wafer processing tape 10 is preferably 3 to 120 seconds, and more preferably 5 to 90 seconds. When the heating conditions are within the above range, the conformability of the wafer processing tape 10 tends to improve.

[0071] 3.2. Processing process The processing steps for processing the wafer 20 with the wafer processing tape 10 bonded to the wafer 20 are not particularly limited, and any wafer processing process can be applied as appropriate. For example, processing steps include a backgrinding step S2, a metal layer formation step S3, a dicing step S4, and a processing step S5.

[0072] Furthermore, as shown in Figure 2, a processing process that combines these steps includes a metal layer formation step S3 in which a metal layer 21 is formed after the backgrinding step S2, and a dicing step S4 in which the thinned wafer is diced by blade dicing or the like. In the following, a process in which the metal layer formation step S3 and the dicing step S4 are performed after the backgrinding step S2 will be described, but this embodiment is not limited to this.

[0073] 3.2.1. Backgrinding Process The backgrinding process S2 is a process of polishing the non-element formation surface 20b of the wafer 20 that is bonded to the wafer processing tape 10. Specifically, with the wafer processing tape 10 attached to the element formation surface 20a as a backgrinding tape from the viewpoint of protecting the element formation surface 20a, the non-element formation surface 20b of the wafer 20 is ground (backgrinded) to a desired thickness.

[0074] The specific method of back grinding is not particularly limited, and known methods can be used. For example, a method can be used in which a slurry containing abrasive particles is supplied to the back surface 20b of the wafer 20 while grinding. The thickness of the thinned wafer obtained by this process is not particularly limited as long as it is a thickness suitable for the processing purpose, but as an example, it is preferably 300 μm or less, 150 μm or less, and 50 μm or less.

[0075] In backgrinding, a load is applied in the thickness direction of the wafer 20, which can easily cause damage to protrusions and other parts, leading to a decrease in yield. In contrast, by using the wafer processing tape 10 of this embodiment, it is possible to perform processing with at least a portion of the protrusions embedded in the wafer processing tape 10, thereby avoiding damage to the protrusions and other parts.

[0076] In the wafer processing method of this embodiment, when performing backgrinding on a wafer that has been pre-formed with modified portions or grooves on its surface for fragmentation, the wafer 20 may be thinned to approximately the same depth as the modified portions or grooves when the wafer 20 is thinned from the back surface 20b of the wafer 20. This allows for simultaneous thinning by backgrinding and fragmentation.

[0077] 3.2.2. Metal layer formation process The metal layer formation step S3 is a step in which a metal layer 21 is formed on the surface 20b of the wafer 20 opposite to the surface 20a to which the wafer processing tape 10 is bonded. The method for forming the metal layer is not particularly limited, but examples include ALD (atomic layer deposition) and CVD (chemical vapor deposition). The conditions for forming the metal layer using these methods are not particularly limited, but examples include processing at 200-300°C for 3-10 minutes.

[0078] 3.2.3. Dicing Process The dicing process S4 is a process of dicing the wafer 20. The dicing method is not particularly limited, but one example is blade dicing, in which the wafer is cut into semiconductor chips 30 using a dicing blade.

[0079] 3.2.4. Processing steps In processing step S5, the back surface of the chip 30 may be surface-treated by etching, sputtering, or reflow to form any surface treatment layer 22. The processing method is not particularly limited, and any processing can be selected according to the application of the chip.

[0080] 3.3. Peeling Process The peeling step S6 is the process of peeling the wafer processing tape 10 from the wafer 20 or semiconductor chip 30. The peeling step in which the semiconductor chip 30 is taken from the wafer processing tape is also called the peeling step.

[0081] In the peeling step S6, the wafer processing tape 10 may be peeled off at room temperature, or it may be peeled off under heating. Also, in the peeling step S6, if the adhesive layer 12 contains a base polymer having polymerizable double bond groups and a photopolymerization initiator, the adhesive layer 12 may be cured by irradiation with ultraviolet light before peeling to reduce its adhesion to the wafer 20. This tends to further improve release properties and further suppress contamination by residue from the tape. Note that if the substrate is transparent, the ultraviolet irradiation may be performed from the substrate layer 11 towards the adhesive layer 12.

[0082] Furthermore, when picking up the semiconductor chip 30 from the wafer processing tape, although not particularly limited, for example, the semiconductor chip 30 may be pushed up with a push-up needle and then picked up by suction with a suction collet.

[0083] Alternatively, during pickup, an expanding device may be used to stretch the wafer processing tape 10 in the planar direction, separating each semiconductor chip 30, and then the chips may be picked up by a pickup device. [Examples]

[0084] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples. Unless otherwise specified, each physical property value was measured at room temperature. In addition, unless otherwise specified, the amount of each raw material used is given in terms of solid content. Therefore, if it is stated that 100 parts by mass of a raw material with a solid content of 40% is used, the total amount used, including the liquid content, will be 250 parts by mass.

[0085] (Example 1) A composition for an adhesive layer was prepared by mixing 100 parts by mass of an acrylic resin having polymerizable carbon double bonds, carboxyl groups, and hydroxyl groups (Vinylole ELX-6512, manufactured by Resonaq, with a glass transition temperature of -60°C), 2.5 parts by mass of an acylphosphine oxide type photopolymerization initiator (Omnirad 819, manufactured by IGM Resins BV, with a molecular weight of 418 and a 10% weight loss temperature of 254°C), and 1.7 parts by mass of an epoxy crosslinking agent (TETRAD-X, manufactured by Mitsubishi Gas Chemical Company).

[0086] A transparent polyamide film with a thickness of 50 μm (Unitika Corporation, Uniamide EX-50, 365 nm UV transmittance 85%, no yield point) was used as the base layer, and the adhesive layer composition prepared as described above was applied to one surface of the film. After heating at 150°C for 2 minutes, the film was aged at 40°C for 3 days to crosslink the carboxyl and hydroxyl groups of the acrylic resin with the epoxy groups of the epoxy crosslinking agent. This produced the wafer processing tape of Example 1. The thickness of the adhesive layer was 15 μm.

[0087] (Example 2) The wafer processing tape for Example 2 was prepared in the same manner as in Example 1, except that the amount of epoxy crosslinking agent (TETRAD-X, manufactured by Mitsubishi Gas Chemical Company) used was 3.5 parts by mass.

[0088] (Comparative Example 1) A wafer processing tape for Comparative Example 1 was prepared in the same manner as in Example 1, except that 2.5 parts by mass of Omnirad 651 (manufactured by IGM Resins BV, molecular weight 256, 10% weight loss temperature: 184°C) was used instead of Omnirad 819, and the amount of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, TETRAD-X) used was increased to 3.5 parts by mass.

[0089] (Adhesive strength) The adhesive strength was measured in accordance with JIS Z 0237. Specifically, the wafer processing tape was placed on the mirror surface of a silicon wafer, and a 2kg roller was passed over it once to bond it. After that, it was left to stand at 23°C for 30 minutes to bond the surface of the adhesive layer of the wafer processing tape to the mirror surface of the silicon wafer. Then, without heating, the wafer processing tape was peeled off at a peeling angle of 180° and a peeling speed (tensile speed) of 300 mm / min, and the adhesive strength N0 (N / 25mm) was determined.

[0090] Furthermore, after bonding the surface of the adhesive layer of the wafer processing tape to the mirror surface of a silicon wafer, the wafer was heated at 250°C for 5 minutes, and then the adhesive force N1 (N / 25mm) was measured when the wafer processing tape was peeled off at a peeling angle of 180° and a peeling speed (tensile speed) of 300 mm / min.

[0091] (Processing) A bonding process was performed in which the surface of the adhesive layer of the wafer processing tape was bonded to a silicon wafer, and then it was heated at 250°C for 5 minutes, simulating a metal layer formation process. The wafer was then diced, and 900 mJ / cm² of pressure was applied to the adhesive layer from the back side of the substrate layer of the wafer processing tape using a high-pressure mercury lamp. 2 The adhesive layer was cured by irradiating it with ultraviolet light, and the wafer processing tape was peeled off the wafer to obtain individual chips.

[0092] (Contamination of water systems due to voids) For 100 chips that underwent the above processing process, the surface after peeling from the wafer processing tape was observed using a digital microscope (Keyence VHX-900), and the number of chips contaminated by water during dicing was confirmed to have emerged from the gaps in the tape that had lifted due to voids. A: More than 95% of the wood chips showed signs of contamination from water sources. B: The percentage of chips showing contamination from water sources is between 85% and 95%. C: The percentage of chips showing contamination from water sources is between 75% and 85%. D: Less than 75% of the chips showed contamination from water sources.

[0093] (Peelability) For 100 chips that underwent the above processing process, the surface after peeling from the wafer processing tape was observed using a digital microscope (Keyence VHX-900), and the peelability was evaluated based on the rate of adhesive residue originating from the wafer processing tape. A: Over 95% of the chips showed no adhesive residue. B: The percentage of chips in which no adhesive residue was found was between 85% and 95%. C: The percentage of chips in which no adhesive residue was found was between 75% and 85%. D: Less than 75% of the chips had no adhesive residue.

[0094] [Table 1]

[0095] In Comparative Example 1, which used a photopolymerization initiator with a molecular weight of less than 350, some of the photopolymerization initiator dissipated after heating at 250°C for 5 minutes. As a result, the reaction did not proceed sufficiently with subsequent UV irradiation, and the rate of decrease in adhesive strength N2 was low.

[0096] Furthermore, wafer processing tapes were also prepared in the same manner as in Example 1, except that the acylphosphine oxide-based photopolymerization initiator Omnirad 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (number average molecular weight 418)) was replaced with α-aminoalkylphenone-based photopolymerization initiators, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (number average molecular weight: 366.5) and 2-(dimethylamino)-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (number average molecular weight: 380.5), and the α-hydroxyketone-based photopolymerization initiator, oligo(2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone) (number average molecular weight: 424.57). As a result, results equivalent to those of Example 1 were obtained.

[0097] Furthermore, a similar adhesive layer composition to that in Example 1 was prepared, applied to a transparent polyamide film, and then heated at 150°C for 60 minutes without aging to produce a wafer processing tape. As a result, it was found that the adhesive strength N0 to N2 of this wafer processing tape could be adjusted by allowing the reaction between the base polymer and the crosslinking agent to proceed sufficiently. Therefore, from the viewpoint of adjusting the adhesive strength N0 to N2, it is considered preferable to perform a predetermined aging treatment.

[0098] Furthermore, the wafer processing tapes of Examples 1 and 2 exhibited excellent chemical resistance, heat resistance, dicing properties, expandability, and pick-up properties, making them suitable for use as wafer processing tapes that can be used across the wafer in semiconductor processing. [Industrial applicability]

[0099] The present invention has industrial applicability as a wafer processing tape and processing method using the same, because it is less likely to generate voids in the adhesive layer during the heating process, and the adhesive strength can be sufficiently reduced when the adhesive layer is irradiated with ultraviolet light during the peeling process, allowing it to be used transversely in semiconductor processing. [Explanation of Symbols]

[0100] 10... Tape for wafer processing, 11... Substrate layer, 11a... Surface, 12... Adhesive layer, 12a... Surface, 12b... Back surface, 20... Wafer, 20a... Element formation surface, 20b... Non-element formation surface, 21... Metal layer, 22... Arbitrary surface treatment layer, 30... Semiconductor chip, 40... Grinder, S1... Lamination process, S2... Back grinding process, S3... Metal layer formation process, S4... Dicing process, S5... Processing process, S6... Peeling process

Claims

1. A base layer and The base layer has an adhesive layer disposed on at least one side, The adhesive layer contains a photopolymerization initiator with a molecular weight of 350 or more. Tape for wafer processing.

2. The temperature at which the photopolymerization initiator loses 10% of its weight is 200 to 300°C. The wafer processing tape according to claim 1.

3. The adhesive strength N1 of the adhesive layer to the silicon wafer after heating at 250°C for 5 minutes is 0.5 to 7.0 N / 25 mm at 25°C. The wafer processing tape according to claim 1.

4. After heating at 250°C for 5 minutes and then UV irradiation, the adhesive strength N2 of the adhesive layer to the silicon wafer is 0.01 to 1.0 N / 25 mm at 25°C. The wafer processing tape according to claim 1.

5. The adhesive layer further comprises an acrylic resin having a polymerizable double bond with a hydroxyl group or a carboxyl group, or a crosslinked structure derived from the acrylic resin. The wafer processing tape according to claim 1.

6. The adhesive layer further comprises an epoxy crosslinking agent or a crosslinked structure derived from the epoxy crosslinking agent. The wafer processing tape according to claim 1.

7. The aforementioned substrate layer contains a polyamide resin. The wafer processing tape according to claim 1.

8. The aforementioned substrate layer does not have a yield point. The wafer processing tape according to claim 1.

9. The ultraviolet transmittance of the substrate layer at 365 nm is 70% or more. The wafer processing tape according to claim 1.

10. A processing step comprising attaching a wafer processing tape according to any one of claims 1 to 9 to a wafer and performing wafer processing, Wafer processing method.

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