Base film and workpiece processing sheet

Abstract

This base material film comprises a first resin layer containing a polyester resin and a polymeric antistatic agent. The polyester resin has an alicyclic structure, and the heat of fusion thereof as measured by differential scanning calorimetry at a temperature increase rate of 20°C / min is 2 J / g or higher. The polymeric antistatic agent contains a polymeric compound and an organic salt constituted of an organic cation and an organic anion, and does not substantially contain an alkaline metal salt or an alkaline earth metal salt. The surface resistivity on at least one surface of the base material film is 1×106Ω / □ to 1×1015Ω / □. This base material film has excellent dust adhesion prevention characteristics and suppresses the generation of impurity ions while also sufficiently suppressing the occurrence of chips.

Description

[Technical Field]

[0001] The present invention relates to a base film that can be suitably used as a base film for a workpiece processing sheet used for processing workpieces such as semiconductor wafers, and to the workpiece processing sheet itself. [Background technology]

[0002] Semiconductor wafers such as silicon and gallium arsenide, as well as various packages, are manufactured in a large diameter state, cut into chips (dicing), and then peeled off (picked up) before being moved to the next process, the mounting process. During this process, the semiconductor wafer and other workpieces are attached to an adhesive sheet (hereinafter sometimes referred to as "workpiece processing sheet") which has a base film and an adhesive layer, and then processed with backgrinding, dicing, washing, drying, expanding, picking up, and mounting.

[0003] One of the dicing methods described above involves cutting the workpiece with a rotating circular blade (dicing blade). In this method, it is common practice to partially cut the workpiece processing sheet to which the workpiece is attached, along with the workpiece itself, to ensure that the workpiece is cut completely.

[0004] In this manner, when the workpiece processing sheet is cut together with the workpiece, cutting debris consisting of the adhesive layer and the materials constituting the base film may be generated from the workpiece processing sheet. In particular, such cutting debris usually occurs near the line (kerf line) through which the circular blade passed on the chip obtained by cutting or on the workpiece processing sheet.

[0005] If a large amount of cutting debris adheres to the chip while it is being sealed, the heat generated during sealing will decompose the debris, and these thermally decomposed products can damage the package or cause malfunctions in the resulting device. Since this debris is difficult to remove by washing, its generation significantly reduces the yield of the dicing process. Therefore, when dicing is performed using a rotating circular blade, it is necessary to prevent the generation of cutting debris.

[0006] Incidentally, as a base film for workpiece processing, a base film using polyester resin as one of the materials is also known (Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2006-152072 [Overview of the project] [Problems that the invention aims to solve]

[0008] The inventors have discovered that by using a base film made of a predetermined polyester resin as one of the materials for a workpiece processing sheet, the generation of cutting debris described above can be effectively suppressed. On the other hand, they have also discovered that such base films made of polyester resin are prone to dust adhesion due to static electricity. In particular, they have found that even when an antistatic agent is incorporated into the film for the purpose of preventing such dust adhesion, it tends to be difficult to obtain sufficient dust adhesion prevention.

[0009] Furthermore, with substrate films containing antistatic agents, there was a problem in that impurity ions would leach out, adversely affecting equipment used to handle wafers, chips, and workpiece processing sheets.

[0010] This invention has been made in view of the above circumstances, and aims to provide a base film that has excellent dust adhesion prevention properties and suppresses the generation of impurity ions while sufficiently suppressing the generation of cutting chips, and a workpiece processing sheet that can effectively exhibit such functions. [Means for solving the problem]

[0011] To achieve the above objective, firstly, the present invention provides a base film comprising a first resin layer containing a polyester resin and a polymeric antistatic agent, wherein the polyester resin has an alicyclic structure and a heat of fusion of 2 J / g or more as measured by differential scanning calorimetry at a heating rate of 20°C / min, and the polymeric antistatic agent contains a polymer compound and an organic salt composed of an organic cation and an organic anion, and substantially does not contain alkali metal salts or alkaline earth metal salts, and the surface resistivity of at least one side of the base film is 1 × 10⁻⁶ 6 Ω / □ or more, 1×10 15 The invention provides a base film characterized by having a density of Ω / □ or less (Invention 1).

[0012] The base film according to the above invention (Invention 1) is made of a material containing polyester resin, and the polyester resin has an alicyclic structure and exhibits the above-mentioned heat of fusion, so that even when a workpiece processing sheet equipped with the base film is used for dicing using a rotating circular blade, the generation of cutting chips can be effectively suppressed. Furthermore, since the surface resistivity of at least one side of the base film is within the above range, static charge is suppressed when using the workpiece processing sheet equipped with the base film, and the adhesion of dust can be effectively suppressed. Moreover, since the first resin layer contains the above-mentioned polymer-type antistatic agent as an antistatic agent, the generation of impurity ions can be suppressed while achieving excellent dust adhesion prevention.

[0013] In the above invention (Invention 1), it is preferable that the polymer compound is a polyether / polyolefin block polymer (Invention 2).

[0014] In the above inventions (Inventions 1 and 2), it is preferable that the organic cation is derived from an imidazolium cation and the organic anion is derived from a sulfonate anion (Invention 3).

[0015] In the above invention (Invention 3), it is preferable that the organic cation is derived from 1-ethyl-1H-imidazole and the organic anion is derived from dodecylbenzenesulfonic acid (Invention 4).

[0016] In the above inventions (Inventions 1 to 4), it is preferable that the content of the antistatic agent in the first resin layer is 1% by mass or more and 50% by mass or less (Invention 5).

[0017] In the above inventions (Inventions 1 to 5), the total amount of Li + ions, Na + ions, and K + ions in the base film measured by ion chromatography is preferably 0 ppm or more and 20 ppm or less (Invention 6).

[0018] In the above inventions (Inventions 1 to 6), it is preferable that the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin (Invention 7).

[0019] In the above inventions (Inventions 1 to 7), it is preferable that the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin (Invention ⑧).

[0020] In the above inventions (Inventions 1 to 8), it is preferable that the alicyclic structure has 6 or more and 14 or less carbon atoms forming the ring (Invention 9).

[0021] In the above inventions (Inventions 1 to 9), the polyester resin preferably contains a dimer acid obtained by dimerizing an unsaturated fatty acid as a monomer unit constituting the polyester resin, and the number of carbon atoms of the unsaturated fatty acid is preferably 10 or more and 30 or less (Invention 10).

[0022] In the above invention (Invention 10), the ratio of the dimer acid as a monomer unit constituting the polyester resin to the total dicarboxylic acid as a monomer unit constituting the polyester resin is preferably 2 mol% or more and 25 mol% or less (Invention 11).

[0023] In the above inventions (Inventions 1 to 11), the thickness of the base film is preferably 20 μm or more and 600 μm or less (Invention 12).

[0024] The present invention provides a workpiece processing sheet comprising the above-mentioned base film (Inventions 1 to 12) and an adhesive layer laminated on one side of the base film (Invention 13).

[0025] In the above invention (Invention 13), it is preferable that the workpiece processing sheet is a dicing sheet (Invention 14). [Effects of the Invention]

[0026] The base film according to the present invention makes it possible to manufacture a workpiece processing sheet that has excellent dust adhesion prevention properties and suppresses the generation of impurity ions while sufficiently suppressing the generation of cutting chips. Furthermore, the workpiece processing sheet according to the present invention can suppress the generation of cutting chips while having excellent dust adhesion prevention properties and suppressing the generation of impurity ions. [Modes for carrying out the invention]

[0027] Embodiments of the present invention will be described below. [Base film] The base film according to this embodiment comprises a first resin layer containing a polyester resin and a polymer-type antistatic agent. The polyester resin has an alicyclic structure and a heat of fusion of 2 J / g or more, as measured by differential scanning calorimetry at a heating rate of 20°C / min.

[0028] The base film according to this embodiment includes a first resin layer containing the polyester resin described above. As a result, when a workpiece processing sheet constructed using this base film is used for dicing a workpiece with a rotating circular blade, the generation of cutting chips can be effectively suppressed.

[0029] Furthermore, the polymer-type antistatic agent described above contains a polymer compound and an organic salt composed of an organic cation and an organic anion. On the other hand, this polymer-type antistatic agent substantially does not contain alkali metal salts or alkaline earth metal salts.

[0030] The base film according to this embodiment can achieve the surface resistivity described later by using the polymer-type antistatic agent described above, thereby effectively suppressing the adhesion of dust to the workpiece processing sheet. In particular, since the polymer-type antistatic agent substantially does not contain alkali metal salts and alkaline earth metal salts, the generation of impurity ions from the base film according to this embodiment is suppressed, and contamination by impurity ions in wafers, chips, equipment, etc. is suppressed.

[0031] In this specification, "substantially free of alkali metal salts and alkaline earth metal salts" means that the total content of alkali metal salts and alkaline earth metal salts in the polymeric antistatic agent is 0.0005% by mass or less, and in particular, it means 0% by mass (i.e., not contained).

[0032] Furthermore, the substrate film according to this embodiment has a surface resistivity of 1 × 10 on at least one side. 6 Ω / □ or more, 1×1015 It is Ω / □ or less. Since the base film according to this embodiment has such a surface resistivity, the work processing sheet configured using the base film is unlikely to be charged during storage or use, and it is possible to effectively suppress the adhesion of dust to the work processing sheet caused by charging.

[0033] From the viewpoint of effectively obtaining such dust adhesion prevention properties, the above surface resistivity is preferably 5.0×10 14 Ω / □ or less, and particularly preferably 2.0×10 14 Ω / □ or less. Note that the lower limit value of the above surface resistivity is not particularly limited. For example, it may be 1×10 8 Ω / □ or more, and particularly may be 1×10 7 Ω / □ or more. The details of the method for measuring the above surface resistivity are as described in the column of test examples described later.

[0034] In addition, as the reason for obtaining the cutting chip suppression effect as described above, the following is expected. However, the possibility that the above effect is obtained by the combination of the following reasons and other reasons is not excluded, and the possibility that the above effect is obtained by reasons other than the following reasons is not excluded either.

[0035] First, it is expected that when a dicing force is applied to a base material made using the polyester resin, the polyester resin is easily cut at the position of the ester bond. Furthermore, the polyester resin in this embodiment has an alicyclic structure as described above and exhibits the above heat of fusion, so that it moderately has a structure (lamellar structure) in which a part of its polymer chain is regularly folded. Therefore, when a dicing force is applied, it is expected that the above polyester resin is also easily cut at the position of the above lamellar structure. Thus, the polyester resin in this embodiment is more likely to be cut at a specific position when a dicing force is applied compared to the resin used in conventional base films.

[0036] The mechanism by which cutting chips are generated from a typical dicing sheet substrate is thought to be that the frictional heat generated during dicing softens the substrate, and then the rotating circular blade makes contact, applying a pulling force to the cut portion of the substrate, causing the cut portion to be stretched and scraped away. In particular, much of the cutting chips generated in this way have a thread-like form.

[0037] On the other hand, in the substrate of this embodiment, it is believed that cutting occurs effectively near the ester bonds and lamellar structure before it is stretched as described above, resulting in the suppression of cutting chip generation.

[0038] From the viewpoint of making it easier to achieve the aforementioned chip suppression effect, the amount of heat of fusion in the polyester resin, measured by differential scanning calorimetry at a heating rate of 20°C / min, is preferably 5 J / g or more, particularly preferably 10 J / g or more, and even more preferably 15 J / g or more. On the other hand, the upper limit of the amount of heat of fusion is not particularly limited, and may be, for example, 150 J / g or less, 100 J / g or less, particularly 70 J / g or less, even more preferably 50 J / g or less, and especially 30 J / g or less. Details of the method for measuring the amount of heat of fusion described above are as described in the Examples section below.

[0039] 1. Materials of the base film, etc. (1) Polyester resin The specific composition of the polyester resin described above is not particularly limited, as long as it has an alicyclic structure and satisfies the conditions that the polyester resin exhibits the above-mentioned heat of fusion.

[0040] From the viewpoint of obtaining a better chip suppression effect, it is preferable that the alicyclic structure of the polyester resin has 6 or more carbon atoms constituting the ring. Furthermore, it is preferable that the number of carbon atoms be 14 or less, and particularly preferable that it be 10 or less. In particular, it is preferable that the number of carbon atoms be 6. Furthermore, the alicyclic structure may be a monocyclic structure consisting of one ring, a bicyclic structure consisting of two rings, or a structure consisting of three or more rings.

[0041] Furthermore, from the viewpoint of easily satisfying the two conditions mentioned above, it is preferable that the polyester resin contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin. Also, from the same viewpoint, it is preferable that the polyester resin contains a diol having an alicyclic structure as a monomer unit constituting the polyester resin. Although only one of such dicarboxylic acids and diols may be contained in the polyester resin, from the viewpoint of more easily satisfying the above conditions, it is preferable that the polyester resin contains both such dicarboxylic acids and diols.

[0042] The structure of the dicarboxylic acid described above is not particularly limited as long as it has an alicyclic structure and two carboxyl groups. For example, the dicarboxylic acid may have a structure in which two carboxyl groups are bonded to an alicyclic structure, or it may have a structure in which an alkyl group or the like is further inserted between such an alicyclic structure and carboxyl groups. Preferred examples of such dicarboxylic acids include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, and 2,7-decahydronaphthalenedicarboxylic acid, and among these, 1,4-cyclohexanedicarboxylic acid is preferred. These dicarboxylic acids may also be derivatives of alkyl esters, etc. Such alkyl ester derivatives may be, for example, alkyl esters having 1 to 10 carbon atoms. More specific examples include dimethyl esters and diethyl esters, with dimethyl esters being particularly preferred.

[0043] In this embodiment, when the polyester resin contains a dicarboxylic acid having an alicyclic structure as a monomer unit, the proportion of the dicarboxylic acid monomer to the total monomer units constituting the polyester resin is preferably 20 mol% or more, more preferably 25 mol% or more, particularly preferably 30 mol% or more, and even more preferably 35 mol% or more. Furthermore, the proportion is preferably 60 mol% or less, more preferably 55 mol% or less, particularly preferably 50 mol% or less, and even more preferably 45 mol% or less. Being within these ranges makes the polyester resin more likely to exhibit the aforementioned heat of fusion, and as a result, the workpiece processing sheet obtained using the base film according to this embodiment is more likely to achieve a better chip suppression effect.

[0044] Furthermore, if the polyester resin in this embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting it, the proportion of the dicarboxylic acid having an alicyclic structure to the total dicarboxylic acid having a cyclic structure constituting the polyester resin is preferably 60% or more, more preferably 70% or more, particularly preferably 80% or more, and even more preferably 90% or more. By having the above proportion of 60% or more, the workpiece processing sheet obtained using the base film according to this embodiment is more likely to achieve a better chip suppression effect. The upper limit of this proportion is not particularly limited, and for example, it may be 100% or less. The above dicarboxylic acid having a cyclic structure includes not only dicarboxylic acids having an alicyclic structure but also dicarboxylic acids having an aromatic ring structure, etc.

[0045] The structure of the diol described above is not particularly limited as long as it has an alicyclic structure and two hydroxyl groups. For example, the diol may have a structure in which two hydroxyl groups are bonded to an alicyclic structure, or it may have a structure in which an alkyl group is further inserted between such an alicyclic structure and hydroxyl groups. Preferred examples of such diols include 1,2-cyclohexanediol (especially 1,2-cyclohexanedimethanol), 1,3-cyclohexanediol (especially 1,3-cyclohexanedimethanol), 1,4-cyclohexanediol (especially 1,4-cyclohexanedimethanol), and 2,2-bis-(4-hydroxycyclohexyl)-propane, and among these, 1,4-cyclohexanedimethanol is preferred.

[0046] In this embodiment, when the polyester resin contains a diol having an alicyclic structure as a monomer unit, the proportion of the diol monomer to the total monomer units constituting the polyester resin is preferably 35 mol% or more, particularly preferably 40 mol% or more, and even more preferably 45 mol% or more. Furthermore, the proportion is preferably 65 mol% or less, particularly preferably 60 mol% or less, and even more preferably 55 mol% or less. Being within these ranges makes the polyester resin more likely to exhibit the aforementioned heat of fusion, and as a result, the workpiece processing sheet obtained using the base film according to this embodiment is more likely to achieve a better chip suppression effect.

[0047] In this embodiment, the polyester resin may also contain dimer acid, obtained by dimerizing an unsaturated fatty acid, as a monomer unit constituting the polyester resin, from the viewpoint of making the substrate more likely to have the desired flexibility. Here, the number of carbon atoms in the unsaturated fatty acid is preferably 10 or more, and particularly preferably 15 or more. Furthermore, the number of carbon atoms is preferably 30 or less, and particularly preferably 25 or less. Examples of such dimer acids include a 36-carbon dicarboxylic acid obtained by dimerizing an 18-carbon unsaturated fatty acid such as oleic acid or linoleic acid, and a 44-carbon dicarboxylic acid obtained by dimerizing an 22-carbon unsaturated fatty acid such as erucic acid. When obtaining the above-mentioned dimer acid, a small amount of trimer acid, obtained by trimmerizing the above-mentioned unsaturated fatty acid, may also be produced. The polyester resin in this embodiment may contain such trimer acid along with the above-mentioned dimer acid.

[0048] In this embodiment, when the polyester resin contains the above-mentioned dimer acid as a monomer unit, the ratio of the dimer acid to the total dicarboxylic acid units constituting the polyester resin is preferably 2 mol% or more, particularly preferably 5 mol% or more, and even more preferably 10 mol% or more. Furthermore, the ratio is preferably 25 mol% or less, particularly preferably 23 mol% or less, and even more preferably 20 mol% or less. Within these ranges, the polyester resin is more likely to have the desired flexibility, and as a result, the workpiece processing sheet obtained using the base film according to this embodiment can achieve excellent expandability and pick-up properties.

[0049] The polyester resin in this embodiment may contain monomers other than the dicarboxylic acids, diols, and dimer acids mentioned above as constituent monomer units. Examples of such monomers include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 4,4'-diphenyldicarboxylic acid. It may also contain diol components other than diols having an alicyclic structure. For example, it may contain ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, decanediol; ethylene oxide adducts such as bisphenol A and bisphenol S; and trimethylolpropane.

[0050] However, in the polyester resin of this embodiment, from the viewpoint of easily achieving an excellent chip suppression effect, it is preferable that monomers having an alicyclic structure (as described above, dicarboxylic acids having an alicyclic structure and diols having a fatty structure) are present in greater quantities than monomers having an aromatic ring structure. In particular, among the monomer units constituting the polyester resin of this embodiment, the molar ratio of monomer units having an aromatic ring structure to monomer units having an alicyclic structure is preferably less than 1, more preferably 0.5 or less, more preferably 0.2 or less, more preferably 0.1 or less, more preferably 0.05 or less, more preferably 0.03 or less, more preferably 0.01 or less, especially preferably 0.005 or less, even more preferably 0.001 or less, and most preferably 0.

[0051] The method for producing the polyester resin in this embodiment is not particularly limited, and the polyester resin can be obtained by polymerizing the above-mentioned monomer components using a known catalyst.

[0052] In this embodiment, the proportion of polyester resin to the total components constituting the base material is preferably 50% or more, particularly preferably 60% or more, and even more preferably 70% or more. A proportion of 50% or more makes it easier to achieve a superior chip suppression effect in the workpiece processing sheet obtained using the base film according to this embodiment. The upper limit of the above proportion is not particularly limited; for example, it may be 100% or less.

[0053] (2) Polymer-type antistatic agent As described above, the polymeric antistatic agent in this embodiment contains a polymer compound and an organic salt composed of an organic cation and an organic anion, while substantially not containing alkali metal salts or alkaline earth metal salts. The polymeric antistatic agent in this embodiment can be used in various forms without particular limitation, as long as these conditions are met.

[0054] The above-mentioned polymer compound refers to a compound having at least two repeating units. The weight-average molecular weight of the polymer compound is preferably 300 or more, and particularly preferably 1000 or more. Furthermore, the weight-average molecular weight is preferably 100,000 or less, particularly preferably 75,000 or less, and even more preferably 50,000 or less. In this specification, the weight-average molecular weight is the value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0055] The above polymer compound is preferably a polymer containing at least one of a polyether segment and a polyolefin segment, from the viewpoint of easily exhibiting excellent antistatic properties. Although these segments may be randomly arranged in the polymer compound, they are preferably arranged in a block-like manner from the viewpoint of easily exhibiting excellent antistatic properties.

[0056] Examples of the polyether segments mentioned above include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyhexamethylene glycol, as well as polyoxyalkylenes and polyalkylene ether diols.

[0057] Examples of the polyolefin segments mentioned above include homopolymers of alphaolefins having 2 to 10 carbon atoms, or copolymers of at least one alphaolefin and at least one other copolymerizable monomer. Examples of alphaolefins include ethylene, propylene, 1-butene, 2-methylpropene, 1-pentene, 3-methyl l-butene, 1-hexene, 4-methyl l-pentene, 3-methyl l-pentene, and 1-octene.

[0058] In the polymer-type antistatic agent of this embodiment, it is particularly preferable to use a polyether / polyolefin block polymer as the polymer compound. By using this polymer compound, it is possible to effectively suppress the generation of impurity ions while exhibiting excellent antistatic properties.

[0059] The organic cations and organic anions constituting the organic salt in this embodiment are not particularly limited, as long as they are ionized organic compounds. Examples of the organic cations include those derived from at least one of the following: imidazolium cation, pyridinium cation, pyrrolidinium cation, ammonium cation, sulfonium cation, phosphonium cation, etc. Examples of the organic anions include linear alkylbenzene sulfonic acid and sulfonate anions (RSO). 3- ), carboxylate anion (RCOO - ), alkoxide or phenoxide anion (RO - ), organic imide anion (R2N - ), Methido (R3C - ) Anions, organic borates (R4B - ) Examples include those derived from at least one type of anion, etc.

[0060] In this embodiment, as the organic salt, it is particularly preferable to use an organic salt composed of an organic cation derived from an imidazolium cation and an organic anion derived from a sulfonate anion, from the viewpoint of exhibiting excellent antistatic properties while also effectively suppressing the generation of impurity ions. More preferably, an organic salt composed of an organic cation derived from 1-ethyl-1H-imidazole and an organic anion derived from dodecylbenzenesulfonic acid is used.

[0061] The alkali metal salts mentioned above refer to salts containing alkali metals such as lithium, sodium, and potassium as cationic components. The alkaline earth metal salts mentioned above refer to salts containing alkaline earth metals such as magnesium and calcium as cationic components. The polymer-type antistatic agent in this embodiment substantially does not contain these alkali metal salts and alkaline earth metal salts, but if they are included, the content is as described above.

[0062] In this embodiment, the polymeric antistatic agent preferably has a 5% weight loss temperature of 200°C or higher in an atmospheric environment, and more preferably 250°C or higher. Having a 5% weight loss temperature of 200°C or higher makes it difficult for the polymeric antistatic agent to decompose even when heated during the mixing or film formation of the base film material, thus making it easier to exhibit sufficient dust adhesion prevention properties. The upper limit of the 5% weight loss temperature is not particularly limited; for example, it may be 1000°C or lower, more preferably 900°C or lower, and even more preferably 700°C or lower.

[0063] Furthermore, the polymeric antistatic agent in this embodiment preferably has a 5% weight loss temperature of 250°C or higher under a nitrogen atmosphere, particularly preferably 270°C or higher, and even more preferably 300°C or higher. Having a 5% weight loss temperature of 250°C or higher makes it difficult for the polymeric antistatic agent to decompose even when heated during the mixing or film formation of the base film material, thus making it easier to exhibit sufficient dust adhesion prevention properties. The upper limit of the 5% weight loss temperature is not particularly limited; for example, it may be 1000°C or lower, particularly 900°C or lower, and even more preferably 700°C or lower.

[0064] Details of the methods for measuring the 5% weight loss temperature under atmospheric and nitrogen atmospheres, as described above, are as shown in the examples below.

[0065] In the base film according to this embodiment, the content of the polymer-type antistatic agent in the first resin layer is preferably 1% by mass or more, more preferably 3% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more. A polymer-type antistatic agent content of 1% by mass or more makes it easier for a workpiece processing sheet constructed using the base film according to this embodiment to achieve good dust adhesion prevention. Furthermore, the content of the antistatic agent in the first resin layer is preferably 50% by mass or less, particularly preferably 45% by mass or less, and even more preferably 40% by mass or less. A polymer-type antistatic agent content of 50% by mass or less makes it easier for a workpiece processing sheet constructed using the base film according to this embodiment to exhibit good mechanical properties, easily exhibit a sufficient chip suppression effect, and further easily suppress the generation of impurity ions.

[0066] (3) Other ingredients The first resin layer in this embodiment may contain other components besides the polyester resin and polymer-type antistatic agent described above. In particular, the material may contain components commonly used in base films for workpiece processing sheets.

[0067] Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. While there are no particular limitations on the content of these additives, it is preferable to set it within a range that allows the base film to exhibit the desired function.

[0068] (4) Composition of the base film The layer structure of the base film in this embodiment may be a single layer or multiple layers, as long as it includes a first resin layer made of the polyester resin and polymer-type antistatic agent described above. From the viewpoint of reducing manufacturing costs, the base film in this embodiment is preferably a single layer (polyester resin layer only).

[0069] On the other hand, when multiple layers are used, the first resin layer may be laminated multiple times, or the first resin layer may be laminated with other layers. In this case, it becomes possible to achieve both the chip suppression effect of the polyester resin layer and the desired effect of the other layers.

[0070] Furthermore, the surface of the base film on which the adhesive layer is laminated may be subjected to surface treatments such as primer treatment, corona treatment, or plasma treatment in order to improve adhesion with the adhesive layer.

[0071] 2. Thickness of the base film, etc. In this embodiment, the thickness of the base film is preferably 20 μm or more, particularly preferably 40 μm or more, and even more preferably 60 μm or more. Furthermore, the thickness of the base film is preferably 600 μm or less, particularly preferably 300 μm or less, and even more preferably 200 μm or less. When the thickness of the base film is 20 μm or more, the workpiece processing sheet tends to have appropriate strength, and the workpiece fixed on the workpiece processing sheet tends to be supported well. As a result, it becomes possible to effectively suppress the occurrence of chipping during dicing. Furthermore, when the thickness of the base film is 600 μm or less, the base film has better processability.

[0072] Furthermore, in the base film of this embodiment, the Li in the base film is measured by ion chromatography. + Ion, Na + Ions and K +The total amount of ions is preferably 20 ppm or less, particularly preferably 15 ppm or less, and even more preferably 10 ppm or less. In the base film of this embodiment, since the first resin layer contains the polymer-type antistatic agent described above, the total amount of ions can be suppressed to a low level of 20 ppm or less. And, because the total amount of contained ions is within this range, when using the workpiece processing sheet, contamination of wafers, chips, equipment, etc. by impurity ions is effectively suppressed. The lower limit of the total amount is not particularly limited and may be, for example, 0 ppm or more, or 0.1 ppm or more. Furthermore, the details of the ion measurement method described above are as described in the test examples below.

[0073] 3. Method for manufacturing the base film The method for manufacturing the base film in this embodiment is not particularly limited as long as the material containing the polyester resin and polymer-type antistatic agent described above is used. For example, melt extrusion methods such as the T-die method and the circular die method; calendering; and solution methods such as the dry method and the wet method can be used. Among these, from the viewpoint of efficiently manufacturing the base film, it is preferable to employ the melt extrusion method or the calendering method.

[0074] When manufacturing a single-layer base film by melt extrusion, the base material (the material containing the polyester resin mentioned above) is kneaded, and the resulting kneaded product is used to form a film either directly from the mixture or after first producing pellets, using a known extruder.

[0075] Furthermore, when manufacturing a base film consisting of multiple layers by melt extrusion, the components constituting each layer can be kneaded separately, and the multiple layers can be extruded simultaneously using a known extruder, either directly from the resulting kneaded material or after first producing pellets, to form the film.

[0076] Furthermore, if the base film has multiple layers, a first resin layer may be formed by applying a coating solution containing the aforementioned polyester resin and polymer-type antistatic agent to one side of a predetermined layer that has been formed into a film beforehand, and then drying or curing it. This makes it possible to obtain a base film comprising the predetermined layer and the first resin layer.

[0077] [Sheet for workpiece processing] The workpiece processing sheet according to this embodiment comprises the aforementioned base film and an adhesive layer laminated on one side of the base film.

[0078] 1. Configuration of the workpiece processing sheet The following describes the components of the workpiece processing sheet according to this embodiment, excluding the base film mentioned above.

[0079] (1) Adhesive layer The adhesive constituting the above adhesive layer is not particularly limited, as long as it can exert sufficient adhesive force to the adherend (especially sufficient adhesive force to the workpiece for processing the workpiece). Examples of adhesives constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, and polyvinyl ether adhesives. Among these, it is preferable to use an acrylic adhesive because it is easier to exert the desired adhesive force.

[0080] The adhesive constituting the adhesive layer in this embodiment may be an adhesive that does not have active energy ray curability, but it is preferable that it is an adhesive that has active energy ray curability (hereinafter sometimes referred to as "active energy ray curable adhesive"). Because the adhesive layer is composed of an active energy ray curable adhesive, the adhesive layer can be cured by irradiation with active energy rays, and the adhesive force of the workpiece processing sheet to the adherend can be easily reduced. In particular, irradiation with active energy rays makes it possible to easily separate the processed workpiece from the workpiece processing sheet.

[0081] The active energy ray curable adhesive constituting the adhesive layer may be mainly composed of an active energy ray curable polymer, or it may be mainly composed of a mixture of an active energy ray non-curable polymer (a polymer that does not possess active energy ray curability) and a monomer and / or oligomer having at least one active energy ray curable group.

[0082] The polymer having active energy ray curability is preferably a (meth)acrylic acid ester polymer (hereinafter sometimes referred to as "active energy ray curable polymer") in which a functional group having active energy ray curability (active energy ray curable group) is introduced into the side chain. This active energy ray curable polymer is preferably obtained by reacting an acrylic copolymer having a functional group-containing monomer unit with an unsaturated group-containing compound having a functional group that is bonded to that functional group. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the concept of "polymer" is also included in the concept of "copolymer".

[0083] The weight-average molecular weight of the above-mentioned active energy ray-curable polymer is preferably 10,000 or more, particularly preferably 150,000 or more, and even more preferably 200,000 or more. Furthermore, the weight-average molecular weight is preferably 2,500,000 or less, particularly preferably 2,000,000 or more, and even more preferably 1,500,000 or less. In this specification, the weight-average molecular weight (Mw) is the value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0084] On the other hand, when an active energy ray-curable adhesive mainly consists of a mixture of an active energy ray-non-curable polymer component and a monomer and / or oligomer having at least one active energy ray-curable group, the active energy ray-non-curable polymer component can be, for example, the acrylic copolymer before reacting with an unsaturated group-containing compound. Furthermore, as the active energy ray-curable monomer and / or oligomer, for example, an ester of a polyhydric alcohol and (meth)acrylic acid can be used.

[0085] The weight-average molecular weight of the acrylic polymer used as the active energy ray non-curable polymer component is preferably 10,000 or more, particularly preferably 150,000 or more, and even more preferably 200,000 or more. Furthermore, the weight-average molecular weight is preferably 2,500,000 or less, particularly preferably 2,000,000 or more, and even more preferably 1,500,000 or less.

[0086] Furthermore, when ultraviolet light is used as the active energy ray for curing an active energy ray-curable adhesive, it is preferable to add a photopolymerization initiator to the adhesive. In addition, active energy ray-non-curable polymer components or oligomer components, crosslinking agents, etc., may be added to the adhesive.

[0087] In this embodiment, the thickness of the adhesive layer is preferably 1 μm or more, particularly preferably 2 μm or more, and even more preferably 3 μm or more. Furthermore, the thickness of the adhesive layer is preferably 50 μm or less, particularly preferably 40 μm or less, and even more preferably 30 μm or less. A thickness of 1 μm or more in the adhesive layer makes it easier for the workpiece processing sheet according to this embodiment to exhibit the desired adhesiveness. Furthermore, a thickness of 50 μm or less in the adhesive layer makes it easier to separate the adherend from the adhesive layer after curing.

[0088] (2) Release sheet In the workpiece processing sheet according to this embodiment, a release sheet may be laminated on the side of the adhesive layer opposite to the base film (hereinafter sometimes referred to as the "adhesive side") for the purpose of protecting that side until it is attached to the adherend.

[0089] The composition of the release sheet described above is arbitrary, and examples include plastic films that have been treated with a release agent. Specific examples of such plastic films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polyolefin films such as polypropylene and polyethylene. As the release agent, silicone-based, fluorine-based, and long-chain alkyl-based agents can be used, and among these, silicone-based agents are preferred because they are inexpensive and provide stable performance.

[0090] There are no particular restrictions on the thickness of the release sheet mentioned above; for example, it may be between 20 μm and 250 μm.

[0091] (3) Others In the workpiece processing sheet according to this embodiment, the adhesive layer may be laminated on the side of the adhesive layer opposite to the base film. In this case, the workpiece processing sheet according to this embodiment can be used as a dicing / die bonding sheet. With this sheet, a workpiece can be attached to the side of the adhesive layer opposite to the adhesive layer, and by dicing the adhesive layer together with the workpiece, a chip can be obtained in which individual pieces of the adhesive layer are laminated. The chip can be easily fixed to the object on which it is mounted by these individual pieces of adhesive layer. As the material constituting the adhesive layer described above, it is preferable to use one that contains a thermoplastic resin and a low molecular weight thermosetting adhesive component, or one that contains a B-stage (semi-cured) thermosetting adhesive component.

[0092] Furthermore, in the workpiece processing sheet according to this embodiment, a protective film forming layer may be laminated on the adhesive surface of the adhesive layer. In this case, the workpiece processing sheet according to this embodiment can be used as a protective film forming and dicing sheet. With such a sheet, a workpiece is attached to the side of the protective film forming layer opposite to the adhesive layer, and the protective film forming layer is diced together with the workpiece to obtain a chip with individual pieces of the protective film forming layer laminated on it. Preferably, a workpiece with a circuit formed on one side is used, and in this case, the protective film forming layer is usually laminated on the side opposite to the side with the circuit formed. By curing the individual pieces of the protective film forming layer at a predetermined timing, a protective film with sufficient durability can be formed on the chip. Preferably, the protective film forming layer is made of an uncured curable adhesive.

[0093] 2. Method for manufacturing sheets for workpiece processing The method for manufacturing the workpiece processing sheet according to this embodiment is not particularly limited. For example, it is preferable to obtain the workpiece processing sheet by forming an adhesive layer on a release sheet, and then laminating one side of a base film onto the side of the adhesive layer opposite to the release sheet.

[0094] The adhesive layer described above can be formed by known methods. For example, a coating solution containing an adhesive composition for forming the adhesive layer, and optionally a solvent or dispersion medium, can be prepared. Then, the coating solution is applied to the release surface of the release sheet (hereinafter sometimes referred to as the "release surface"). Subsequently, the adhesive layer can be formed by drying the resulting coating film.

[0095] The coating solution described above can be applied by known methods, such as bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc. The properties of the coating solution are not particularly limited as long as it can be applied, and it may contain components for forming the adhesive layer as a solute or as a dispersed phase. The release sheet may be peeled off as a process material, or it may protect the adhesive layer until it is attached to the substrate.

[0096] If the adhesive composition for forming the adhesive layer contains the aforementioned crosslinking agent, it is preferable to promote the crosslinking reaction between the polymer components in the coating film and the crosslinking agent by changing the drying conditions (temperature, time, etc.) or by separately performing a heat treatment, thereby forming a crosslinked structure with a desired density in the adhesive layer. Furthermore, in order to allow the above-mentioned crosslinking reaction to proceed sufficiently, curing may be performed after bonding the adhesive layer and the base film, for example, by leaving it undisturbed for several days in an environment of 23°C and 50% relative humidity.

[0097] 3. How to use the workpiece processing sheet The workpiece processing sheet according to this embodiment can be used for processing workpieces such as semiconductor wafers. In this case, after attaching the adhesive surface of the workpiece processing sheet according to this embodiment to the workpiece, processing of the workpiece can be performed on the workpiece processing sheet. Depending on the processing, the workpiece processing sheet according to this embodiment can be used as a workpiece processing sheet such as a backgrind sheet, dicing sheet, expand sheet, or pickup sheet. Examples of workpieces include semiconductor wafers, semiconductor components such as semiconductor packages, and glass components such as glass plates.

[0098] The workpiece processing sheet according to this embodiment is constructed using the base film according to this embodiment, thereby achieving excellent dust adhesion prevention while also achieving a good chip suppression effect. For this reason, the workpiece processing sheet according to this embodiment is particularly suitable for use as a dicing sheet.

[0099] Furthermore, if the workpiece processing sheet according to this embodiment includes the aforementioned adhesive layer, the workpiece processing sheet can be used as a dicing and die bonding sheet. In addition, if the workpiece processing sheet according to this embodiment includes the aforementioned protective film forming layer, the workpiece processing sheet can be used as a protective film forming and dicing sheet.

[0100] Furthermore, if the adhesive layer in the workpiece processing sheet according to this embodiment is composed of the aforementioned active energy ray curable adhesive, it is also preferable to irradiate it with the following active energy rays during use. That is, when the processing of the workpiece is completed on the workpiece processing sheet and the processed workpiece is to be separated from the workpiece processing sheet, it is preferable to irradiate the adhesive layer with active energy rays before the separation. This hardens the adhesive layer, which reduces the adhesive force of the workpiece processing sheet to the processed workpiece, making it easier to separate the processed workpiece.

[0101] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Examples]

[0102] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0103] [Example 1] (1) Preparation of base film In a reactor equipped with a stirrer, distillation tube, and vacuum device, 12.90 kg of dimethyl 1,4-cyclohexanedicarboxylate (98% trans isomer ratio), 11.47 kg of 1,4-cyclohexanedimethanol, 0.3 kg of ethylene glycol, and 0.11 kg of an ethylene glycol solution containing 10% Mn acetate tetrahydrate were charged. The mixture was heated to 200°C under a nitrogen flow, and then the temperature was increased to 230°C over 1 hour. After holding the mixture for 2 hours to carry out the transesterification reaction, 10.30 kg of erucic acid-derived dimer acid (44 carbon atoms, manufactured by Croda, product name "PRIPOL1004") and 0.11 kg of an ethylene glycol solution containing 10% trimethyl phosphate were added to the system, and the esterification reaction was carried out at 230°C for 1 hour. Next, 300 ppm germanium dioxide was added as a polycondensation catalyst and stirred. The pressure was then reduced to below 133 Pa for 1 hour, during which time the internal temperature was raised from 230°C to 270°C. The polycondensation reaction was carried out under high vacuum below 133 Pa, stirring until the desired viscosity was achieved. The resulting polymer was extruded into water in strand form, cut, and formed into pellets.

[0104] The polyester resin pellets obtained in this manner were dried at 85°C for more than 4 hours. Then, 90 parts by mass of the dried pellets and 10 parts by mass of a polymeric antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Pelektron UC"), which is a polymer compound consisting of a polyether / polyolefin block polymer to which an organic salt composed of an organic cation derived from 1-ethyl-1H-imidazole and an organic anion derived from dodecylbenzenesulfonic acid is added, were kneaded in a twin-screw kneader. The resulting pellets were fed into the hopper of a single-screw extruder equipped with a T-die. Then, under conditions of cylinder temperature 220°C and die temperature 220°C, the pellets were extruded from the T-die in a molten and kneaded state and cooled with a cooling roll to obtain a sheet-like base film with a thickness of 80 μm.

[0105] The polyester resin described above contained approximately 50 mol% of 1,4-cyclohexanedimethanol, approximately 40.5 mol% of 1,4-cyclohexanedicarboxylate dimethyl, and 9.5 mol% of erucic acid-derived dimer acid as monomers constituting the resin. The ratio of the dimer acid to the total dicarboxylic acid units constituting the polyester resin was 19.1 mol%. Furthermore, the heat of fusion of the polyester resin was measured by the method described later and was found to be 20 J / g.

[0106] Furthermore, when the 5% weight loss temperature of the above polymer-type antistatic agent was measured by the method described later, it was 260°C under an atmospheric environment and 333°C under a nitrogen atmosphere.

[0107] (2) Preparation of adhesive composition 95 parts by mass of n-butyl acrylate and 5 parts by mass of acrylic acid were polymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. The weight-average molecular weight (Mw) of this acrylic polymer was measured by the method described later and was found to be 500,000.

[0108] As described above, 100 parts by mass (on a solid content basis, the same applies hereafter) of the (meth)acrylic acid ester polymer obtained, 120 parts by mass of urethane acrylate oligomer (Mw: 8,000), 5 parts by mass of isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), and 4 parts by mass of photopolymerization initiator (manufactured by IGM Resins BV, product name "Omnirad 184") were mixed to obtain an energy ray-curable adhesive composition.

[0109] (3) Formation of the adhesive layer The adhesive composition obtained in step (2) above was applied to the release surface of a release sheet (Lintec Corporation, product name "SP-PET381031"), in which one side of a 38 μm thick polyethylene terephthalate film had been released with a silicone-based release agent. The resulting coating was dried at 100°C for 1 minute. This resulted in a laminate in which a 10 μm thick adhesive layer was formed on the release surface of the release sheet.

[0110] (4) Preparation of workpiece processing sheets A workpiece processing sheet was obtained by bonding one side of the base film obtained in step (1) above with the adhesive layer side of the laminate obtained in step (3) above.

[0111] (5)Various measurement methods The heat of fusion of the aforementioned polyester resin was measured in accordance with JIS K 7121:2012 using a differential scanning calorimeter (DSC, manufactured by T.A. Instruments, product name "DSC Q2000"). Specifically, the sample was first heated from room temperature to 250°C at a heating rate of 20°C / min, held at 250°C for 10 minutes, then cooled to -60°C at a cooling rate of 20°C / min, and held at -60°C for 10 minutes. After that, it was heated again to 250°C at a heating rate of 20°C / min to obtain a DSC curve and measure the melting point.

[0112] The 5% weight loss temperature of the polymer-type antistatic agent described above was determined using a differential thermal and thermogravimetric simultaneous measurement device (Shimadzu Corporation, product name "DTG-60") in accordance with JIS K7120:1987. Specifically, using air or nitrogen as the inflow gas, thermogravimetric measurements were performed by raising the temperature from 40°C to 550°C at a gas inflow rate of 100 ml / min and a heating rate of 20°C / min. From the obtained thermogravimetric curve, the temperature at which the mass decreases by 5% compared to the mass at 100°C (5% weight loss temperature) was determined.

[0113] Furthermore, the weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight on a standard polystyrene basis, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> • Measuring device: HLC-8320, manufactured by Tosoh Corporation • GPC columns (passed through in the following order): Manufactured by Tosoh Corporation TSK Gel Super H-H TSK gel superHM-H TSK Gel Super H2000 • Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0114] [Examples 2-3] A workpiece processing sheet was obtained in the same manner as in Example 1, except that the amounts of polyester resin and antistatic agent were changed as shown in Table 1.

[0115] [Comparative Example 1] A workpiece processing sheet was obtained in the same manner as in Example 1, except that a polyether ester amide-based antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Perectron AS") was used as the antistatic agent, and the proportions of polyester resin and antistatic agent were changed as shown in Table 1.

[0116] Furthermore, the 5% weight loss temperature of the above-mentioned polyether ester amide-based antistatic agent was measured by the method described later and was found to be 340°C under an atmospheric environment and 358°C under a nitrogen atmosphere. The above-mentioned polyether ester amide-based antistatic agent is a polyether ester amide to which a metal salt has been added.

[0117] [Comparative Example 2] A workpiece processing sheet was obtained in the same manner as in Example 1, except that a polyether ester amide block polymer-based antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Perestat N1200") was used as the antistatic agent, and the amounts of polyester resin and antistatic agent were changed as shown in Table 1.

[0118] Furthermore, the above-mentioned polyether ester amide block polymer-based antistatic agent consists of a polyether ester amide block polymer and does not contain any added organic salts or metal salts.

[0119] [Test Example 1] (Measurement of surface resistivity) The surface resistivity of one side of the substrate films manufactured in the examples and comparative examples was measured. Specifically, the surface resistivity (Ω / □) of samples cut from the substrate film to a size of 100 mm x 100 mm was measured using a digital ultra-high resistance / microcurrent meter 5450 (manufactured by ADC Corporation) under the conditions of an applied voltage of 100 V and an applied time of 60 sec. The results are shown in Table 1.

[0120] [Test Example 2] (Measurement of the number of cutting chips) The release sheet was peeled off from the workpiece processing sheet manufactured in the examples and comparative examples, and the exposed adhesive layer was attached to one side of a 40 μm thick silicon wafer. Then, a dicing ring frame was attached to the peripheral edge of the exposed surface on the workpiece processing sheet (a position that does not overlap with the silicon wafer). Next, the silicon wafer was diced using a dicing saw (DISCO Corporation, product name "DFD6362") under the following conditions. • Workpiece (substrate): Silicon wafer • Workpiece size: 6 inches in diameter, 40 μm thick • Dicing blade: Manufactured by Disco Corporation, product name "27HECC", diamond blade • Blade rotation speed: 50,000 rpm • Dicing speed: 100 mm / sec • Cutting depth: Cut to a depth of 20 μm from the surface of the substrate. • Dicing size: 8mm x 8mm

[0121] After dicing, with the individual silicon wafer chips still attached to the workpiece processing sheet, the number of cutting chips generated on the kerf lines (cutting lines created by the dicing blade) was counted using a digital microscope (Keyence Corporation, product name "VHX-5000", magnification: 500x). In this count, the number of cutting chips was counted on three lines near the center in the vertical direction and three lines near the center in the horizontal direction, out of the multiple kerf lines present in both the vertical and horizontal directions. The count results are shown in Table 1.

[0122] [Test Example 3] (Evaluation of dust adhesion prevention) Samples were obtained by cutting the workpiece processing sheets manufactured in the examples and comparative examples to A4 size. Each sample was placed on a horizontal surface with the substrate side facing upwards, and then left to stand for 1 hour in an environment of 23°C and 50% relative humidity. Afterward, the amount of dust adhering to the substrate side of the samples was visually inspected. The results showed that the sample from the examples had significantly less dust than the sample from the comparative examples. Therefore, the dust adhesion prevention performance of the examples was judged to be "good," while that of the comparative examples was judged to be "poor." These results are also shown in Table 1.

[0123] [Test Example 4] (Measurement and evaluation of impurity ions) The workpiece processing sheets produced in the examples and comparative examples were cut into strips (approximately 0.5-1 cm x 3 cm), and the release sheets were peeled off to obtain measurement samples. One g of each measurement sample was immersed in deionized water in a container, the container was sealed, and boiled under pressure (2 atm) at 121°C for 24 hours. The Li contained in the obtained extract water was measured. + Ion, Na + Ions and K + The concentration of each ion was measured using ion chromatography (Yokogawa Electric Corporation, product name "High-Performance Ion Chromatograph IC500P"). The detection limit of this ion chromatography was 0.01 ppm. The results are shown in Table 1. If the concentration was below the detection limit, "ND" is indicated in Table 1. Table 1 also shows the total concentration of the three types of ions mentioned above.

[0124] Furthermore, the total concentration of the three types of ions mentioned above was evaluated against the following criteria to assess the impurity ions contained in the workpiece processing sheet. The results are shown in Table 1. Good: The total concentration of the three types of ions mentioned above was 20 ppm or less. Defect: The total concentration of the three types of ions mentioned above exceeded 20 ppm.

[0125] [Table 1]

[0126] As is clear from Table 1, the workpiece processing sheets manufactured in the examples effectively suppressed the generation of cutting chips during dicing while also effectively suppressing the adhesion of debris. Furthermore, the workpiece processing sheets manufactured in the examples had a very low concentration of impurity ions, and it was estimated that using these sheets would effectively suppress contamination of wafers, chips, equipment, etc., by impurity ions. [Industrial applicability]

[0127] The base film of the present invention can be suitably used as a base film constituting a workpiece processing sheet used for processing workpieces such as semiconductor wafers.

Claims

1. A base film comprising a first resin layer containing a polyester resin and a polymer-type antistatic agent, The polyester resin has an alicyclic structure, and its heat of fusion, measured by differential scanning calorimetry at a heating rate of 20°C / min, is 2 J / g or more. The polymer-type antistatic agent contains a polymer compound and an organic salt composed of an organic cation and an organic anion, and substantially does not contain alkali metal salts or alkaline earth metal salts. The aforementioned polymer compound is a polyether / polyolefin block polymer, The surface resistivity on at least one side of the pre-substrate film is 1 × 10 ６ Ω / □ or more, 1×10 １５ It is less than or equal to Ω / □ A base film characterized by the following features.

2. The aforementioned organic cation is derived from an imidazolium cation. The aforementioned organic anion is derived from a sulfonate anion. The base film according to feature 1.

3. The aforementioned organic cation is derived from 1-ethyl-1H-imidazole, The aforementioned organic anion is derived from dodecylbenzenesulfonic acid. The base film according to feature 2.

4. The base film according to claim 1, characterized in that the content of the antistatic agent in the first resin layer is 1% by mass or more and 50% by mass or less.

5. Li in the substrate film measured by ion chromatography ＋ Ions, Na ＋ Ions and K ＋ The base film according to claim 1, characterized in that the total amount of ions is 0 ppm or more and 20 ppm or less.

6. The base film according to claim 1, characterized in that the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin.

7. The base film according to claim 1, characterized in that the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin.

8. The substrate film according to claim 1, characterized in that the alicyclic structure has 6 or more and 14 or less carbon atoms constituting the ring.

9. The polyester resin contains dimer acid, which is obtained by dimerizing an unsaturated fatty acid, as a monomer unit constituting the polyester resin. The number of carbon atoms in the aforementioned unsaturated fatty acid is 10 or more and 30 or less. The base film according to feature 1.

10. The base film according to claim 9, characterized in that the ratio of the dimer acid as a monomer unit constituting the polyester resin to the total dicarboxylic acid as a monomer unit constituting the polyester resin is 2 mol% or more and 25 mol% or less.

11. The base film according to claim 1, characterized in that the thickness of the base film is 20 μm or more and 600 μm or less.

12. A base film according to any one of claims 1 to 11, An adhesive layer laminated on one side of the base film and A workpiece processing sheet characterized by having the following features.

13. The workpiece processing sheet according to claim 12, characterized in that the workpiece processing sheet is a dicing sheet.

Images