TW202323052A - Base material film and workpiece processing sheet - Google Patents

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 DEG 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*106[Omega]/□ to 1*1015[Omega]/□. 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

Substrate film and sheet for workpiece processing

The present invention relates to a substrate film that can be suitably used as a substrate film for processing workpieces such as semiconductor wafers, and the workpiece processing sheet.

Semiconductor wafers made of silicon, gallium arsenide, etc., and various packages are manufactured in a large-diameter state, cut (cut) into wafers, peeled (picked), and then transferred to the next step, which is the mounting (mount) step. At this time, the workpiece such as a semiconductor wafer is attached to an adhesive sheet (hereinafter sometimes referred to as a "workpiece processing sheet") provided with a base film and an adhesive layer, and the backside grinding, dicing, cleaning, Processing such as drying, swelling, picking, mounting, etc.

As one of the cutting methods described above, there is a method of cutting a workpiece using a rotating circular blade (cutting blade). In this method, usually, the workpiece is partially cut together with the workpiece processing sheet attached thereto, thereby surely cutting the workpiece.

In this way, when the workpiece is cut together with the workpiece processing sheet, chips formed of the materials constituting the adhesive layer and the base film may be generated from the workpiece processing sheet. In particular, such swarf is usually generated near a line (kerf line) through which a circular blade passes in a wafer obtained by dicing or a sheet for workpiece processing.

If the wafer is sealed with a large amount of swarf attached to the wafer, the swarf attached to the wafer will be thermally decomposed by the sealing, and this thermally decomposed product will destroy the package or cause malfunction in the resulting device. Since it is difficult to remove such chips by washing, the generation of chips can significantly reduce the productivity of the cutting step. Therefore, in the case of cutting with a rotating circular blade, it is necessary to prevent generation of chips.

Incidentally, as a base film of a workpiece processing sheet, a base film using a polyester resin as one of the materials is known (Patent Document 1). [Prior Art Literature] [Patent Document]

Patent Document 1: JP-A-2006-152072.

[Problem to be solved by the invention]

The inventors of the present invention have found that by using a base film as a sheet for workpiece processing and using a base film made of a predetermined polyester resin as one of the materials, the generation of the above-mentioned swarf can be effectively suppressed. On the other hand, the inventors of the present invention found that such a base film made of a polyester resin tends to attract dust due to electrification. In particular, it has also been found that even if an antistatic agent is blended into the film to prevent such dust adhesion, it tends to be difficult to obtain sufficient dust adhesion prevention properties.

In addition, there is a problem that impurity ions are eluted from a base film prepared with an antistatic agent, which adversely affects devices used for processing wafers, wafers, and workpiece processing sheets.

The present invention has been made in view of such actual conditions, and provides a substrate film capable of sufficiently suppressing the generation of chips, having excellent dust adhesion prevention properties, and suppressing the generation of impurity ions, and workpiece processing that can perform such functions well Use the tablet as a purpose. [means used to solve problems]

In order to achieve the above object, first, the present invention provides (Invention 1) a base film, which is a base film with a first resin layer containing a polyester resin and a polymer antistatic agent, characterized in that the aforementioned polyester The ester resin has an alicyclic structure, and the heat of fusion measured by differential scanning calorimetry at a heating rate of 20°C/min is 2J/g or more. The above-mentioned polymer antistatic agent contains a polymer compound and an organic cation An organic salt composed of an organic anion, substantially free of alkali metal salts and alkaline earth metal salts, the surface resistivity of at least one side of the substrate film is 1×10 ⁶ Ω/□ or more and 1×10 ¹⁵ Ω /□ below.

The base film of the above-mentioned invention (Invention 1) is formed of a material containing a polyester resin, and the polyester resin has a resinous structure and exhibits the above-mentioned heat of dissolution. In the case of a workpiece processing sheet made of a material film, the generation of chips can be well suppressed. In addition, when the surface resistivity of at least one side of the base film is in the above-mentioned range, electrification is suppressed when using a workpiece processing sheet including the base film, and dust adhesion can be favorably suppressed. Furthermore, when the first resin layer contains the above-mentioned polymer antistatic agent as an antistatic agent, it is possible to suppress generation of impurity ions while achieving excellent dust adhesion prevention properties.

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

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).

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).

In the above inventions (Inventions 1 to 4), the content of the antistatic agent in the first resin layer is preferably not less than 1% by mass and not more than 50% by mass (Invention 5).

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

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

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

In the above inventions (Inventions 1 to 8), the number of carbon atoms constituting the ring with the aforementioned alicyclic structure is preferably 6 to 14 (Invention 9).

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

In the above invention (Invention 10), the ratio of the dimer acid as a monomer unit constituting the polyester resin to all dicarboxylic acids constituting the monomer units constituting the polyester resin is 2 mol % or more And preferably below 25 mol% (invention 11).

In the above inventions (Inventions 1 to 11), it is preferable that the thickness of the base film is not less than 20 μm and not more than 600 μm (Invention 12).

A sheet for processing is provided, comprising: the above-mentioned base film (Inventions 1 to 12) and an adhesive layer laminated on one side of the base film (Invention 13).

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

According to the base film of the present invention, it is possible to manufacture a sheet for workpiece processing which has excellent dust prevention properties and suppresses the generation of impurity ions while sufficiently suppressing the generation of chips. In addition, the workpiece processing sheet of the present invention can sufficiently suppress the generation of chips, has excellent dust adhesion prevention properties, and suppresses the generation of impurity ions.

[Mode for Carrying Out the Invention]

Embodiments of the present invention will be described below. [Substrate film] The base film of this embodiment is equipped with the 1st resin layer containing a polyester resin and a polymer type antistatic agent. Then, the polyester resin has an alicyclic structure, and the heat of fusion measured by differential scanning calorimetry (DSC) at a heating rate of 20° C./min is 2 J/g or more.

The base film of the present embodiment is equipped with the first resin layer containing the above-mentioned polyester resin, and the workpiece processing sheet composed of this base film can be favorably cut when a rotating circular blade is used to cut the workpiece. Suppresses chip generation.

In addition, the above-mentioned polymer antistatic agent contains a polymer compound and an organic salt composed of an organic cation and an organic anion. On the other hand, the polymer antistatic agent does not substantially contain alkali metal salts and alkaline earth metal salts.

The base film of this embodiment can realize the surface resistivity mentioned later by using the above-mentioned polymer type antistatic agent as an antistatic agent, and can suppress adhesion of dust to the sheet|seat for workpiece|work processing favorably by this. In particular, this polymer type antistatic agent suppresses impurity ions generated from the substrate film of this embodiment by substantially not containing alkali metal salts and alkaline earth metal salts, and suppresses the generation of impurity ions in wafers, wafers, and devices. Contamination caused by impurity ions, etc.

In this specification, "substantially not containing alkali metal salts and alkaline earth metal salts" means that the total content of alkali metal salts and alkaline earth metal salts in the polymer antistatic agent is 0.0005% by mass or less, especially 0% by mass ( That is, does not contain).

In addition, the surface resistivity of at least one surface of the base film of the present embodiment is not less than 1×10 ⁶ Ω/□ and not more than 1×10 ¹⁵ Ω/□. Since the base film of this embodiment has such a surface resistivity, the sheet for processing a workpiece made of this base film is less likely to be charged during storage or use, and can well suppress dust from adhering to workpiece processing caused by electrification. Use tablets.

From the viewpoint of effectively obtaining such dust adhesion prevention properties, the above-mentioned surface resistivity is preferably not more than 5.0×10 ¹⁴ Ω/□, particularly preferably not more than 2.0×10 ¹⁴ Ω/□. In addition, the lower limit of the surface resistivity is not particularly limited, and may be, for example, 1×10 ⁸ Ω/□ or more, particularly 1×10 ⁷ Ω/□ or more. In addition, the detail of the measuring method of the said surface resistivity is as described in the column of the test example mentioned later.

In addition, the reason why the chip suppression effect is obtained as described above is expected as follows. However, the possibility of obtaining the above-mentioned effects by combining the following reasons with other reasons is not excluded, and the possibility of obtaining the above-mentioned effects by reasons other than the following reasons is not excluded.

First, when a cutting force is applied to a base material produced using this polyester resin, it is expected that the polyester resin will be easily cut at the position of the ester bond. Furthermore, since the polyester resin of this embodiment has the above-mentioned alicyclic structure and exhibits heat of fusion, a part of its polymer chain has a moderately regular folded structure (lamellar structure). Therefore, when a cutting force is applied, the above-mentioned polyester resin is expected to be easily cut even at the position of the layered structure. Thus, the polyester resin of the present embodiment is more easily cut at a specific position when a cutting force is applied, compared with resins used for conventional base films.

Here, as a mechanism for generating chips from the base material of a general dicing sheet, it is considered that the base material is softened by the frictional heat generated at the time of dicing, and the base material is stretched by contacting the rotating circular blade. The force of the cut part makes the cut part of the base material stretched and scraped off at the same time. In particular, most of the chips produced in this way have a filamentous morphology.

On the other hand, in the base material of this embodiment, as described above, before being stretched, it is considered that generation of chipping is suppressed as a result of efficient cutting in the vicinity of the ester bond and the layered structure.

From the point of view of realizing the above-mentioned chip suppression effect more easily, the heat of fusion of the above-mentioned polyester resin measured by differential scanning calorimetry at a heating rate of 20°C/min is preferably 5 J/g or more, preferably 10 J/g or more It is particularly preferred, and more preferably 15 J/g or more. On the other hand, the upper limit of the heat of fusion is not particularly limited, for example, it may be 150 J/g or less, or 100 J/g or less, especially 70 J/g or less, further 50 J/g or less, especially 30 J/g or less . In addition, the detail of the measuring method of the heat of fusion mentioned above is as described in the column of the Example mentioned later.

1. The material of the substrate film, etc. (1) Polyester resin The specific composition of the above-mentioned polyester resin is not particularly limited as long as it has an alicyclic structure and satisfies the above-mentioned condition that the polyester resin exhibits the above-mentioned heat of fusion.

From the viewpoint of easily obtaining the effect of suppressing chipping, the alicyclic structure of the polyester resin preferably has 6 or more carbon atoms constituting the ring. In addition, the number of carbon atoms is preferably 14 or less, particularly preferably 10 or less. In particular, the above-mentioned number of carbon atoms is preferably 6. In addition, the alicyclic structure may be a monocyclic structure formed of one ring, a bicyclic structure formed of two rings, or a structure formed of three or more rings.

In addition, from the viewpoint of easily satisfying the above-mentioned two conditions, it is preferable that the above-mentioned polyester resin contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin. Furthermore, from the same viewpoint, it is preferable that the above-mentioned polyester resin contains a diol having an alicyclic structure as a monomer unit constituting the polyester resin. Although the polyester resin may contain only one of such a dicarboxylic acid and a diol, it is preferable that the polyester resin contains both of such a dicarboxylic acid and a diol from the viewpoint of satisfying the above-mentioned conditions more easily.

The structure of the dicarboxylic acid is not particularly limited as long as it has an alicyclic structure and two carboxyl groups. For example, a dicarboxylic acid may have a structure in which two carboxyl groups are bonded to an alicyclic structure, or may have a structure in which an alkyl group or the like is further inserted between such an alicyclic structure and the carboxyl group. Preferable examples of such dicarboxylic acids include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4- Decalin dicarboxylic acid, 1,5-decalin dicarboxylic acid, 2,6-decalin dicarboxylic acid, 2,7-decalin dicarboxylic acid, etc., among them, use 1,4-ring Hexanedicarboxylic acid is preferred. These dicarboxylic acids may be derivatives of alkyl esters and the like. Such an alkyl ester derivative may be, for example, an alkyl ester having 1 to 10 carbon atoms. More specific examples include dimethyl esters, diethyl esters, and the like, and dimethyl esters are particularly preferred.

In the case where the polyester resin of the present embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting it, the ratio of the dicarboxylic acid monomer to all the monomer units constituting the polyester resin is 20 molar. It is preferably at least mol%, more preferably at least 25 mol%, particularly preferably at least 30 mol%, and still more preferably at least 35 mol%. In addition, the ratio is preferably not more than 60 mol%, more preferably not more than 55 mol%, particularly preferably not more than 50 mol%, and more preferably not more than 45 mol%. Within these ranges, the polyester resin tends to exhibit the aforementioned heat of fusion, and as a result, the sheet for workpiece processing obtained by using the base film of the present embodiment tends to achieve a more excellent swarf suppression effect.

In addition, when the polyester resin of the present embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting it, the dicarboxylic acid having an alicyclic structure is relatively weak compared to the dicarboxylic acid having a ring structure constituting the polyester resin. The ratio of the whole carboxylic acid is preferably at least 60%, more preferably at least 70%, particularly preferably at least 80%, and still more preferably at least 90%. When the said ratio is 60% or more, the sheet|seat for workpiece|work processing obtained using the base film of this embodiment can realize|achieve more excellent chip suppression effect easily. In addition, the upper limit value of this ratio is not specifically limited, For example, it may be 100% or less. Moreover, the dicarboxylic acid which has the said ring structure includes the dicarboxylic acid which has an aromatic ring structure, etc. besides the dicarboxylic acid which has an alicyclic structure.

The structure of the diol is not particularly limited as long as it has an alicyclic structure and two hydroxyl groups. For example, diol may have a structure in which two hydroxyl groups are bonded to an alicyclic structure, or may have a structure in which an alkyl group is further inserted between such an alicyclic structure and a hydroxyl group. Preferable 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), 2,2-bis-(4-hydroxycyclohexyl)-propane, etc., wherein, Preferably, 1,4-cyclohexanedimethanol is used.

In the case where the polyester resin in this embodiment contains a diol having an alicyclic structure as a monomer unit constituting it, the ratio of the diol monomer to all the monomer units constituting the polyester resin is 35 mol. More than mol% is preferable, more than 40 mol% is particularly preferable, and 45 mol% or more is still more preferable. In addition, the ratio is preferably not more than 65 mol%, particularly preferably not more than 60 mol%, and more preferably not more than 55 mol%. Within these ranges, the polyester resin tends to exhibit the aforementioned heat of fusion, and as a result, the sheet for workpiece processing obtained using the base film of the present embodiment tends to achieve a more excellent swarf suppression effect.

The polyester resin in this embodiment preferably contains a dimer acid obtained by dimerizing unsaturated fatty acid as a monomer unit constituting the polyester resin from the viewpoint that the base material is likely to have desired flexibility. Here, the number of carbon atoms of the unsaturated fatty acid is preferably 10 or more, particularly preferably 15 or more. In addition, the above-mentioned number of carbon atoms is preferably 30 or less, particularly preferably 25 or less. Examples of such dimer acids include dicarboxylic acids with 36 carbon atoms obtained by dimerizing unsaturated fatty acids with 18 carbon atoms such as oleic acid and linoleic acid, and dicarboxylic acids with 22 carbon atoms such as erucic acid. Dicarboxylic acids with 44 carbon atoms obtained by dimerization of unsaturated fatty acids. In addition, when the above-mentioned dimer acid is obtained, a small amount of trimer acid obtained by trimerizing the above-mentioned unsaturated fatty acid may be generated. The polyester resin in this embodiment may contain such a trimer acid together with the above-mentioned dimer acid.

When the polyester resin of this embodiment contains the dimer acid as a monomer unit constituting it, the ratio of the dimer acid to all the dicarboxylic acid units constituting the polyester resin is preferably 2 mol % or more. , more than 5 mol% is particularly preferred, and 10 mol% or more is further preferred. In addition, this ratio is preferably not more than 25 mol%, particularly preferably not more than 23 mol%, and still more preferably not more than 20 mol%. In these ranges, the polyester resin tends to have desired flexibility, and as a result, the sheet for workpiece processing obtained by using the base film of the present embodiment can also achieve excellent expandability, pick-up properties, and the like.

The polyester resin in this embodiment may contain monomers other than the above-mentioned dicarboxylic acid, diol, and dimer acid as monomer units constituting it. 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, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, and the like. In addition, diol components other than diols having an alicyclic structure may be contained. For example, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, and decanediol; ethylene oxide adducts such as bisphenol A and bisphenol S; trimethylolpropane, and the like may be contained.

However, in the polyester resin of the present embodiment, from the viewpoint of easily achieving an excellent chip suppression effect, monomers having an alicyclic structure (the aforementioned dicarboxylic acids having an alicyclic structure, dicarboxylic acids having an aliphatic structure, etc.) Alcohols), it is better to contain more monomers with aromatic ring structures. In particular, among the monomer units constituting the polyester resin of the present embodiment, the molar ratio of monomer units having an aromatic ring structure to monomer units having an alicyclic structure is preferably less than 1, preferably 0.5 Below is better, below 0.2 is more preferable, below 0.1 is more preferable, below 0.05 is more preferable, below 0.03 is more preferable, below 0.01 is more preferable, below 0.005 is especially good, below 0.001 is the best Good, 0 is the best.

The method for producing the polyester resin of the present embodiment is not particularly limited, and the polyester resin can be obtained by polymerizing the aforementioned monomer components using a known catalyst.

The proportion of the polyester resin is preferably 50% or more, particularly preferably 60% or more, and still more preferably 70% or more, based on all the components constituting the base material of the present embodiment. When the said ratio is 50 % or more, the sheet|seat for workpiece|work processing obtained using the base film of this embodiment becomes easy to realize a more excellent chip suppression effect. In addition, the upper limit of the ratio is not particularly limited, and may be, for example, 100% or less.

(2) Polymer antistatic agent The polymer type antistatic agent in this embodiment contains a polymer compound and an organic salt composed of organic cations and organic anions as described above, but does not substantially contain alkali metal salts and alkaline earth metal salts. As the polymer antistatic agent in this embodiment, as long as these conditions are satisfied, various polymer antistatic agents can be used without particular limitation.

The aforementioned polymer compound refers to a compound having at least two or more repeating units. The weight average molecular weight of the high molecular compound is preferably 300 or more, particularly preferably 1000 or more. In addition, the weight average molecular weight is preferably at most 100,000, particularly preferably at most 75,000, and still more preferably at most 50,000. In addition, the weight average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC method).

From the viewpoint of easily exhibiting excellent antistatic properties, the polymer compound is preferably a polymer containing at least one of a polyether segment and a polyolefin segment. Although these segments may be randomly arranged in the polymer compound, they are preferably arranged in blocks from the viewpoint of easily exhibiting excellent antistatic properties.

Examples of the above-mentioned polyether segment include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyhexamethylene glycol; polyoxyalkylenes, polyalkylene glycols, and the like; Ether glycol, etc.

In addition, as an example of the above-mentioned polyolefin segment, it is a homopolymer of an alpha olefin having 2 to 10 carbon atoms or a copolymer of at least one alpha olefin and at least one other copolymerizable monomer. Examples of α-olefins include ethylene, propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1 -pentene, 3-methyl-1-pentene, 1-octene, etc.

In the high-molecular antistatic agent of this embodiment, it is particularly preferable to use a polyether/polyolefin block polymer as the above-mentioned high-molecular compound. By using this polymer compound, it is possible to satisfactorily suppress generation of impurity ions while exhibiting excellent antistatic properties.

The organic cation and the organic anion constituting the organic salt in the present embodiment are not particularly limited as long as the organic compound is ionized. Examples of such organic cations include those derived from at least one of imidazolium cations, pyridinium cations, pyrrolidinium cations, ammonium cations, permalium cations, phosphonium cations, and the like. In addition, as examples of the above-mentioned organic anions, linear alkylbenzenesulfonic acid, sulfonate anion (RSO ^3- ), carboxylate anion (RCOO ^- ), alkoxide or phenoxide anion (RO ^- ), organic acyl At least one of amine anion (R ₂ N ^- ), methide (R ₃ C ^- ) anion, organic borate (R ₄ B ^- ) anion, and the like.

As the organic salt in this embodiment, from the viewpoint of exhibiting excellent antistatic properties and suppressing the generation of impurity ions well, in particular, an organic cation derived from an imidazolium cation and an organic cation derived from a sulfonium cation are used. An organic salt formed from an organic anion of an acid radical anion is preferred, and it is more preferable to use an organic salt derived from an organic cation derived from 1-ethyl-1H-imidazole and an organic anion derived from dodecylbenzenesulfonic acid. good.

In addition, the above-mentioned alkali metal salt refers to a salt having an alkali metal such as lithium, sodium, potassium, or the like as a cation component. In addition, the said alkaline-earth metal salt refers to the salt which has alkaline-earth metals, such as magnesium and calcium, as a cationic component. The polymer antistatic agent of the present embodiment does not substantially contain these alkali metal salts and alkaline earth metal salts, but the content in the case of containing them is as described above.

The temperature at which the weight of the polymer antistatic agent of this embodiment reduces by 5% in the air environment is preferably 200° C. or higher, particularly preferably 250° C. or higher. When the above-mentioned 5% weight reduction temperature is 200°C or higher, even if the material of the base film is heated during kneading and film formation, the polymer antistatic agent is difficult to decompose and can easily exhibit sufficient dust adhesion prevention properties. In addition, the upper limit of the above-mentioned 5% weight loss temperature is not particularly limited, for example, it may be 1000°C or lower, particularly 900°C or lower, and further may be 700°C or lower.

In addition, the 5% weight loss temperature of the polymer antistatic agent of this embodiment is preferably 250° C. or higher, particularly preferably 270° C. or higher, and more preferably 300° C. or higher under a nitrogen atmosphere. Since the above-mentioned 5% weight reduction temperature is 250° C. or higher, even if the material of the base film is heated during kneading and film formation, the polymer antistatic agent is difficult to decompose and can easily exhibit sufficient dust adhesion prevention properties. In addition, the upper limit of the above-mentioned 5% weight loss temperature is not particularly limited, for example, it may be 1000°C or lower, particularly 900°C or lower, and further may be 700°C or lower.

The details of the method for measuring the temperature at which the weight decreases by 5% in the air environment and the nitrogen atmosphere mentioned above are as described in Examples described later.

In the base film of the present embodiment, the content of the polymer antistatic agent in the first resin layer is preferably at least 1% by mass, more preferably at least 3% by mass, particularly preferably at least 5% by mass, and preferably at least 10% by mass. It is more preferable that it is more than mass %. When the content of the polymer antistatic agent is 1% by mass or more, the workpiece processing sheet composed of the base film of the present embodiment can easily achieve good dustproof adhesion prevention properties. In addition, the content of the antistatic agent in the first resin layer is preferably at most 50% by mass, particularly preferably at most 45% by mass, and still more preferably at most 40% by mass. When the content of the polymer antistatic agent is 50% by mass or less, the workpiece processing sheet composed of the base film of this embodiment is easy to exhibit good mechanical properties, and at the same time, it is easy to exhibit a sufficient chip suppression effect, and it is easy to Effectively suppress the generation of impurity ions.

(3) Other ingredients The first resin layer of the present embodiment may contain other components than the above-mentioned polyester resin and polymer antistatic agent. In particular, this material may contain a component used in a base film of a sheet for general workpiece processing.

Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. The content of these additives is not particularly limited, but is preferably within a range in which the base film exhibits desired functions.

(4) Composition of base film The layer configuration of the base film of this embodiment may be a single layer or a plurality of layers as long as it includes a first resin layer formed of a material containing the aforementioned polyester resin and a polymer antistatic agent. From the viewpoint of reducing production costs, the base film of the present embodiment is preferably a single layer (only polyester resin layer).

On the other hand, in the case of multiple layers, a plurality of first resin layers may be laminated, or the first resin layer and other layers may be laminated. In this case, the chip-suppressing effect of the polyester resin layer and the desired effect of the other layers can be simultaneously achieved.

In addition, in order to improve the adhesiveness with this adhesive layer, you may give surface treatment, such as primer treatment, corona treatment, and plasma treatment, to the surface of the base film which laminated|stacked the adhesive layer.

2. Thickness of substrate film, etc. The thickness of the base film of the present embodiment is preferably at least 20 μm, particularly preferably at least 40 μm, and still more preferably at least 60 μm. In addition, the thickness of the base film is preferably at most 600 μm, particularly preferably at most 300 μm, and still more preferably at most 200 μm. When the thickness of the base film is 20 μm or more, the workpiece processing sheet can easily have appropriate strength, and can easily support the workpiece fixed on the workpiece processing sheet. As a result, it is possible to effectively suppress generation of chips and the like during cutting. In addition, when the thickness of the base film is 600 μm or less, the base film has better processability.

In addition, in the substrate film of the present embodiment, the total amount of Li ⁺ ions, Na ⁺ ions and K ⁺ ions in the substrate film measured by ion chromatography is preferably 20 ppm or less, particularly preferably 15 ppm or less, It is more preferably 10 ppm or less. In the base material film of this embodiment, since the 1st resin layer contains the said polymer type antistatic agent, the total amount of the said ion can be suppressed to a low level of 20 ppm or less. Then, when the total amount of ions contained is within this range, contamination of wafers, wafers, devices, etc. by impurity ions can be effectively and easily suppressed when using a workpiece processing sheet. Moreover, the lower limit of the said total amount is not specifically limited, For example, it may be 0 ppm or more, and may be 0.1 ppm or more. In addition, the details of the measuring method of the said ion are as described in the test example mentioned later.

3. Manufacturing method of substrate film The manufacturing method of the base film in this embodiment is not particularly limited as long as it uses the aforementioned polyester resin and polymer type antistatic agent. For example, melt extrusion such as T die method and circular die method can be used out method; calendering method; solution method such as dry method, wet method, etc. Among them, it is preferable to use a melt extrusion method or a calendering method from the viewpoint of efficiently producing the base material.

When producing a substrate film formed of a single layer by a melt extrusion method, the substrate (material containing the aforementioned polyester resin) is kneaded, and the resulting kneaded product can be directly or after being pelletized, Films were extruded using known mechanisms.

In addition, in the case of producing a base film composed of multiple layers by a melt extrusion method, the components constituting each layer may be kneaded separately, and the obtained kneaded product may be directly or pelletized using a known The extruder extrudes multiple layers at the same time to form a film.

In addition, when the base film has multiple layers, it is possible to apply the above-mentioned coating liquid containing a polyester resin and a polymer antistatic agent to one side of a predetermined layer formed in a pre-film shape. drying or curing to form the first resin layer. Thereby, the base film provided with the predetermined layer and a 1st resin layer can be obtained.

[Work piece processing sheet] The workpiece processing sheet according to this embodiment includes the aforementioned base film and an adhesive layer laminated on one side of the base film.

1. Composition of sheet for workpiece processing Hereinafter, among members constituting the sheet for workpiece processing according to the present embodiment, configurations other than the aforementioned base film will be described.

(1) Adhesive layer The adhesive constituting the adhesive layer is not particularly limited as long as it can exert sufficient adhesive force to the adherend (in particular, sufficient adhesive force to the workpiece for processing the workpiece). Examples of the adhesive constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, and polyvinyl ether adhesives. agent etc. Among them, it is preferable to use an acrylic adhesive from the viewpoint of easily exhibiting a desired adhesive force.

The adhesive constituting the adhesive layer in this embodiment may be an adhesive that does not have active energy ray curability, but an adhesive that has active energy ray curability (hereinafter sometimes referred to as "active energy ray curable adhesive") may be used. Adhesive") is preferred. Since the adhesive layer is composed of an active energy ray-curable adhesive, the adhesive layer is cured by irradiation of active energy rays, thereby easily reducing the adhesive force of the sheet for workpiece processing to an adherend. In particular, the processed workpiece can be easily separated from the workpiece processing sheet by irradiating active energy rays.

The active energy ray-curable adhesive constituting the adhesive layer may be an active energy ray-curable polymer as the main component, or an active energy ray non-curable polymer (a polymer that does not have active energy ray-curability). substance) and a mixture of monomers and/or oligomers having at least one active energy ray hardening group as the main component.

Active energy ray-curable polymers, (meth)acrylate polymers with active energy ray-curable functional groups (active energy ray-curable groups) introduced into side chains (hereinafter sometimes referred to as "active energy ray-curable permanent polymer") is preferred. The 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 bonded to the functional group. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Further, "polymer" should also include the concept of "copolymer".

The weight average molecular weight of the active energy ray-curable polymer is preferably at least 10,000, particularly preferably at least 150,000, and still more preferably at least 200,000. In addition, the weight average molecular weight is preferably at most 2.5 million, particularly preferably at least 2 million, and still more preferably at most 1.5 million. In addition, the weight average molecular weight (Mw) in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC method).

On the other hand, when the active energy ray-curable adhesive is 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 as a main component, as As the active energy ray non-curable polymer component, for example, the above-mentioned acrylic copolymer before reacting with the unsaturated group-containing compound can be used. In addition, 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.

The weight average molecular weight of the acrylic polymer as the active energy ray non-curing polymer component is preferably at least 10,000, particularly preferably at least 150,000, and still more preferably at least 200,000. In addition, the weight average molecular weight is preferably at most 2.5 million, particularly preferably at least 2 million, and still more preferably at most 1.5 million.

In addition, when ultraviolet rays are used as the active energy rays for curing the active energy ray-curable adhesive, it is preferable to add a photopolymerization initiator to the adhesive. In addition, an active energy ray non-curable polymer component or oligomer component, a crosslinking agent, and the like may be added to the adhesive.

The thickness of the adhesive layer in this embodiment is preferably at least 1 μm, particularly preferably at least 2 μm, and still more preferably at least 3 μm. In addition, the thickness of the adhesive layer is preferably not more than 50 μm, particularly preferably not more than 40 μm, and more preferably not more than 30 μm. When the thickness of the adhesive layer is 1 μm or more, the workpiece processing sheet according to the present embodiment can easily exhibit desired adhesiveness. In addition, when the thickness of the adhesive layer is 50 μm or less, when the adherend is separated from the cured adhesive layer, it can be easily separated.

(2) Peeling sheet In the sheet for workpiece processing of this embodiment, the surface of the adhesive layer opposite to the base film (hereinafter sometimes referred to as "adhesive surface") is attached to the adherend for the purpose of protecting the surface. A release sheet can be laminated on this surface.

The structure of the above-mentioned release sheet is arbitrary, and a release treatment of a plastic film using a release agent or the like can be exemplified. Specific examples of this plastic film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polypropylene, polyethylene and other polyolefin films. As the above-mentioned release agent, silicone-based, fluorine-based, long-chain alkyl-based, etc. can be used, and among these, the silicone-based one that is inexpensive and provides stable performance is preferable.

The thickness of the release sheet is not particularly limited, and may be, for example, 20 μm or more and 250 μm or less.

(3) Other In the workpiece processing sheet of this embodiment, the adhesive layer may be laminated on the surface of the adhesive layer opposite to the base film. In this case, the workpiece processing sheet of this embodiment can be used as a dicing/die bonding sheet. In this wafer, a workpiece is attached to the surface of the adhesive layer opposite to the adhesive layer, and by cutting the workpiece and the adhesive layer together, a wafer on which individualized adhesive layers are laminated can be obtained. . With the individualized adhesive layer, the chip can be easily fixed to the object on which the chip is installed. As the material constituting the adhesive layer, those containing thermoplastic resin and low molecular weight thermosetting adhesive components, those containing B-stage (semi-cured) thermosetting adhesive components, etc. are preferably used.

In addition, in the workpiece processing sheet of 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 of this embodiment can be used as a protective film forming and dicing sheet. In such a sheet, a workpiece is attached to the surface of the protective film forming layer opposite to the adhesive layer, and the protective film forming layer and the workpiece are cut together to obtain a wafer on which individualized protective film forming layers are laminated. . As this workpiece, it is preferable to use one on which a circuit is formed on one side, and in this case, usually, a protective film forming layer is laminated on the surface opposite to the surface on which the circuit is formed. By hardening the individualized protective film forming layer for a predetermined time, a protective film having sufficient durability can be formed on the wafer. The protective film forming layer is preferably formed of an uncured curable adhesive.

2. Manufacturing method of sheet for workpiece processing The manufacturing method of the workpiece processing sheet of this embodiment is not particularly limited. For example, after forming an adhesive layer on a release sheet, it is preferable to laminate one side of the base film on the surface of the adhesive layer opposite to the release sheet to obtain a sheet for workpiece processing.

Formation of the said adhesive layer can be performed by a well-known method. For example, a coating liquid containing an adhesive composition for forming an adhesive layer and, if desired, a solvent or a dispersion medium is prepared. Then, the above-mentioned coating liquid is applied to the releasable surface of the release sheet (hereinafter, sometimes referred to as "release surface"). Next, an adhesive layer can be formed by drying the obtained coating film.

Coating of the above-mentioned coating liquid can be carried out by known methods, for example, bar coating method, blade coating method, roll coating method, air knife coating method, die coating method, gravure coating method, etc. Wait to proceed. In addition, the properties of the coating liquid are not particularly limited as long as it can be applied, and components for forming the adhesive layer may be contained as solutes or may be contained as dispersion media. In addition, the peeling sheet can be peeled off as a construction material, and can also protect the adhesive layer until it is attached to an adherend.

In the case where the adhesive composition used to form the adhesive layer contains the aforementioned crosslinking agent, the polymer component in the coating film can be made It is preferable to perform a crosslinking reaction with a crosslinking agent to form a crosslinked structure having a desired density in the adhesive layer. Furthermore, in order to fully proceed the above crosslinking reaction, after laminating the adhesive layer and the base film, for example, it can be aged at 23°C and 50% relative humidity for several days.

3. How to use the sheet for work processing The workpiece processing sheet of this embodiment can be used for processing workpieces such as semiconductor wafers. In this case, after affixing the adhesive surface of the workpiece processing sheet of this embodiment to a workpiece, the workpiece can be processed on the workpiece processing sheet. According to this processing, the workpiece processing sheet of this embodiment can be used as a workpiece processing sheet such as a back grinding sheet, a dicing sheet, an expansion sheet, and a pick-up sheet. Here, examples of the workpiece include semiconductor components such as semiconductor wafers and semiconductor packages, glass members such as glass plates, and the like.

The sheet for workpiece processing of the present embodiment is constituted by using the base film of the present embodiment, and can realize excellent dust adhesion prevention properties while achieving a good swarf suppression effect. Therefore, the workpiece processing sheet of this embodiment is particularly suitable for use as a dicing sheet.

Moreover, when the sheet|seat for workpiece processing of this embodiment is provided with the said adhesive agent layer, this sheet|seat for workpiece processing can be used as a dicing|die bonding sheet. Furthermore, when the sheet|seat for workpiece|work processing of this embodiment is equipped with the said protective film formation layer, this sheet|seat for workpiece|work processing can be used as a sheet|seat for protective film formation and dicing.

In addition, when the adhesive layer in the workpiece processing sheet according to this embodiment is composed of the aforementioned active energy ray-curable adhesive, it is preferable to irradiate the following active energy rays at the time of use. That is, when the workpiece is processed on the workpiece processing sheet and the processed workpiece is separated from the workpiece processing sheet, it is preferable to irradiate the adhesive layer with active energy rays before the separation. As a result, the adhesive layer is hardened, the adhesive force of the workpiece processing sheet to the processed workpiece is reduced favorably, and the processed workpiece is easily separated.

The embodiments described above are for facilitating understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiment includes all design changes, equivalents, and the like within the technical scope of the present invention. [Example]

Hereinafter, although an Example etc. demonstrate this invention more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1] (1) Production of substrate film In a reactor equipped with a stirrer, a distillation tube and a decompression device, 12.90 kg of dimethyl 1,4-cyclohexanedicarboxylate (trans isomer ratio 98%), 11.47 kg of 1, 4-Cyclohexanedimethanol, 0.3 kg of ethylene glycol, and 0.11 kg of an ethylene glycol solution containing 10% manganese acetate tetrahydrate were heated to 200° C. under a nitrogen stream, and then heated to 230° C. over 1 hour. Keep it as it is for 2 hours, after the transesterification reaction, 10.30 kg of dimer acid derived from erucic acid (44 carbon atoms, manufactured by Croda, product name "PRIPOL 1004"), 0.11 kg of trimethyl phosphate containing 10% The ethylene glycol solution of the ester was put into the system, and then the esterification reaction was carried out at 230° C. for 1 hour. Next, after adding 300 ppm of germanium dioxide as a polycondensation catalyst and stirring, the pressure is reduced to below 133Pa in 1 hour, and the internal temperature is raised from 230°C to 270°C during this time, and stirred to a predetermined value under high vacuum below 133Pa. viscosity, the polycondensation reaction is carried out. The obtained polymer was extruded into strands in water and cut out to obtain pellets.

The pellets of the polyester resin thus obtained were dried at 85° C. for 4 hours or more. Thereafter, 90 parts by mass of the dried granules were added with an organic cation derived from 1-ethyl-1H-imidazole and a polyether/polyolefin block polymer as an antistatic agent and a polymer compound. 10 parts by mass of a polymer antistatic agent (manufactured by Sanyo Chemical Industry Co., Ltd., product name "Plectron UC") formed from an organic salt of an organic anion of dodecylbenzenesulfonic acid, in a biaxial kneader mixing. The granules thus obtained were put into the hopper of a single-screw extruder equipped with a T-die. Then, under the conditions of the cylinder temperature of 220°C and the mold temperature of 220°C, the above-mentioned pellets were extruded from the T-die in the state of melting and kneading, and cooled with a cooling roll to obtain a sheet-shaped pellet with a thickness of 80 μm. Substrate film.

In addition, the above-mentioned polyester resin contains about 50 mol % of 1,4-cyclohexanedimethanol, about 40.5 mol % of 1,4-cyclohexanedicarboxylic acid dimethyl, as monomers constituting the resin. ester, and 9.5 mol% dimers from erucic acid. Moreover, the ratio of the said dimer acid with respect to the whole dicarboxylic acid unit which comprises the said polyester resin was 19.1 mol%. Furthermore, when the heat of fusion of the said polyester resin was measured by the method mentioned later, it was 20 J/g.

In addition, when the 5% weight loss temperature of the above-mentioned polymer type antistatic agent was measured by the method mentioned later, it was 260 degreeC in air atmosphere, and it was 333 degreeC in nitrogen atmosphere.

(2) Preparation of adhesive composition A (meth)acrylate polymer was obtained by polymerizing 95 parts by mass of n-butyl acrylate and 5 parts by mass of acrylic acid by the solution polymerization method. The weight average molecular weight (Mw) of this acrylic polymer was measured by the method mentioned later, and it was 500,000.

100 parts by mass of the (meth)acrylate polymer obtained above (in terms of solid content, the same applies hereinafter), 120 parts by mass of urethane acrylate oligomer (Mw: 8,000), and an isocyanate-based crosslinking agent ( Tosoh Co., Ltd., product name "Coronate L") 5 parts by mass, and photopolymerization initiator (IGM Resins B.V. company, product name "Omnirad 184") 4 parts by mass were mixed to obtain an energy ray-curable adhesive composition .

(3) Formation of adhesive layer Apply the adhesive composition obtained in the above step (2) to the release-treated surface of a release sheet (manufactured by Lintec Co., Ltd., product name "SP-PET381031"), which is a polyparaphenylene sheet with a thickness of 38 μm. One side of the ethylene glycol diformate film was peeled with a silicone-based release agent, and the obtained coating film was dried at 100° C. for 1 minute. Thus, a laminate in which an adhesive layer with a thickness of 10 μm was formed on the release surface of the release sheet was obtained.

(4) Production of sheets for workpiece processing A sheet for workpiece processing was obtained by bonding one side of the base film obtained in the above step (1) to the surface on the side of the adhesive layer in the laminate obtained in the above step (3).

(5) Various measurement methods The heat of fusion of the 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, first, heat from room temperature to 250°C at a heating rate of 20°C/min, hold at 250°C for 10 minutes, decrease to -60°C at a cooling rate of 20°C/min, and hold at -60°C for 10 minutes. Thereafter, it was heated again to 250° C. at a temperature increase rate of 20° C./min to obtain a DSC curve and measure the melting point.

The temperature at which the weight of the polymeric antistatic agent decreases by 5% was measured in accordance with JIS K7120:1987 using a differential thermal/thermogravimetric simultaneous measuring device (manufactured by Shimadzu Corporation, product name "DTG-60"). Specifically, the thermogravimetric measurement was performed by using the air or nitrogen as the inflow gas, raising the temperature from 40° C. to 550° C. at a gas inflow rate of 100 ml/min and a temperature increase rate of 20° C./min. The temperature at which the mass decreases by 5% relative to the mass at 100° C. (the temperature at which the weight decreases by 5%) was determined from the obtained thermogravimetric curve.

In addition, the said weight average molecular weight (Mw) is the standard polystyrene conversion weight average molecular weight measured (GPC measurement) under the following conditions using gel permeation chromatography (GPC). ＜Measurement conditions＞ ． Measuring device: Tosoh Co., Ltd., HLC-8320 ． GPC Columns (passed in the following order): Tosoh Joint Stock Company TSK gel superH-H TSK gel superHM-H TSK gel superH2000 ． Determination solvent: tetrahydrofuran ． Measuring temperature: 40°C

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

[Comparative example 1] As the antistatic agent, a polyether ester amide antistatic agent (manufactured by Sanyo Chemical Industry Co., Ltd., product name "Plectron AS") was used, and the blending amount of the polyester resin and the antistatic agent was changed as shown in Table 1. , A sheet for workpiece processing was obtained in the same manner as in Example 1.

In addition, the 5% weight loss temperature of the above-mentioned polyetheresteramide antistatic agent was measured by the method mentioned later, and it was 340 degreeC in air environment, and it was 358 degreeC in nitrogen atmosphere. In addition, the above-mentioned polyetheresteramide-based antistatic agent is one in which a metal salt is added to polyetheresteramide.

[Comparative example 2] As an antistatic agent, a polyetheresteramide block polymer antistatic agent (manufactured by Sanyo Chemical Industry Co., Ltd., product name "Pelestat N1200") was used, and the composition of the polyester resin and the antistatic agent was changed as shown in Table 1. Except for the compounding amount, a sheet for workpiece processing was obtained in the same manner as in Example 1.

In addition, the above-mentioned polyether ester amide block polymer antistatic agent is formed of polyether ester amide block polymer without adding organic salts, metal salts and the like.

[Test Example 1] (Measurement of Surface Resistivity) The surface resistivity of one side of the base film manufactured in the Example and the comparative example was measured. Specifically, the surface of a sample obtained by cutting the base film to a size of 100 mm x 100 mm was measured using a digital ultra-high resistance/micro ammeter 5450 (manufactured by ADC Co., Ltd.) under the conditions of an applied voltage of 100 V and an applied time of 60 seconds. Resistivity (Ω/□). The results are shown in Table 1.

[Test Example 2] (Measurement of the number of chips) The peeling sheet was peeled off from the workpiece processing sheet manufactured in Examples and Comparative Examples, and the exposed surface of the exposed adhesive layer was attached to one side of a silicon wafer with a thickness of 40 μm, and then the dicing ring frame was attached to the workpiece processing sheet. The peripheral portion of the above-mentioned exposed surface (the position that does not overlap with the silicon wafer). Next, this silicon wafer was diced using a dicing saw (manufactured by Disco Co., Ltd., product name "DFD6362") under the following conditions. ． Workpiece (adhered object): silicon wafer ． Workpiece size: 6 inches in diameter, 40 μm in thickness ． Cutting blade: Made by Disco Co., Ltd., product name "27HECC", diamond blade ． Blade rotation speed: 50,000 rpm ． Cutting speed: 100mm/sec ． Cutting depth: cut from the surface of the substrate to a depth of 20 μm ． Cutting size: 8 mm x 8 mm

After dicing, with the individualized silicon wafer attached to the workpiece processing sheet, use a digital microscope (manufactured by Keyence Co., Ltd., product name "VHX-5000", magnification: 500 times) to calculate the incision line The amount of swarf produced on (the cutting line created by the cutting blade). At this time, the numbers of chips existing in three rows near the center in the vertical direction and three rows near the center in the horizontal direction among the plurality of incision lines in the vertical direction and the horizontal direction are calculated. The calculated results are shown in Table 1.

[Test Example 3] (Evaluation of Dust Adhesion Prevention Property) Samples were obtained by cutting the workpiece processing sheets produced in Examples and Comparative Examples into A4 size. This sample was placed on a horizontal stand so as to be above the substrate-side surface, and then left to stand in an environment with a temperature of 23° C. and a relative humidity of 50% for 1 hour. Thereafter, the amount of dust adhering to the substrate-side surface of the above sample was confirmed visually. As a result, the amount of dust in the sample of the example was remarkably smaller than that of the sample of the comparative example. Therefore, the dust adhesion prevention property of the Example was judged as "good", and the comparative example was judged as "poor". These results are also shown in Table 1.

[Test Example 4] (Measurement and Evaluation of Impurity Ions) The workpiece processing sheets produced in Examples and Comparative Examples were cut into strips (about 0.5 to 1 cm × 3 cm), and the peeling sheets were peeled off and removed to obtain sample. 1 g of this measurement sample was immersed in deionized water in a container, and the container was sealed and boiled at 121° C. for 24 hours under increased pressure (2 atm). By ion chromatography, using an ion chromatograph (manufactured by Yokogawa Electric Co., Ltd., product name "High Performance Ion Chromatoanalyzer IC500P"), each of Li ⁺ ions, Na ⁺ ions, and K ⁺ ions contained in the obtained extracted water was measured. concentration. In addition, the limit of detection using this ion chromatograph is 0.01 ppm. The results are shown in Table 1. In addition, when the detection limit was not reached, it described as "ND" in Table 1. In addition, Table 1 also shows the total amount of the concentrations of the above-mentioned three kinds of ions.

Furthermore, the total amount of the concentration of the above three kinds of ions was referred to the following criteria to evaluate the impurity ions contained in the workpiece processing sheet. The results are shown in Table 1. Good: The total of the concentrations of the above three ions is 20 ppm or less. Bad: The total of the concentrations of the above three ions exceeds 20 ppm.

[Table 1]

As is apparent from Table 1, the workpiece machining sheets produced in Examples effectively suppressed the generation of chips during cutting and also favorably suppressed the adhesion of dust. Furthermore, the workpiece processing wafers produced in Examples contain very low concentrations of impurity ions, and when these are used, it is presumed that contamination of wafers, wafers, devices, etc. by impurity ions can be well suppressed.

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

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Claims (14)

A base film, which is a base film with a first resin layer containing a polyester resin and a polymer antistatic agent, wherein the polyester resin has an alicyclic structure, and is obtained by differential scanning calorimetry The heat of fusion measured at a heating rate of 20°C/min is 2 J/g or more, and the above-mentioned polymer antistatic agent contains a polymer compound and an organic salt composed of an organic cation and an organic anion, and substantially does not contain a base In the metal salt and the alkaline earth metal salt, the surface resistivity of at least one side of the base film is not less than 1×10 ⁶ Ω/□ and not more than 1×10 ¹⁵ Ω/□. The substrate film according to claim 1, wherein the aforementioned polymer compound is a polyether/polyolefin block polymer. The substrate film according to claim 1, wherein, The aforementioned organic cations are derived from imidazolium cations, The aforementioned organic anions are derived from sulfonate anions. The substrate film according to claim 3, wherein, The aforementioned organic cations are derived from 1-ethyl-1H-imidazole, The aforementioned organic anions are derived from dodecylbenzenesulfonic acid. The base film according to claim 1, wherein the content of the antistatic agent in the first resin layer is not less than 1% by mass and not more than 50% by mass. The substrate film according to claim 1, wherein the total amount of Li ⁺ ions, Na ⁺ ions and K ⁺ ions in the substrate film measured by ion chromatography is not less than 0 ppm and not more than 20 ppm. The base film according to claim 1, wherein the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin. The base film according to claim 1, wherein the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin. The substrate film according to claim 1, wherein the number of carbon atoms constituting the ring of the alicyclic structure is not less than 6 and not more than 14. The base film according to claim 1, wherein, The aforementioned polyester resin contains dimer acid obtained by dimerizing unsaturated fatty acid as a monomer unit constituting the polyester resin, The number of carbon atoms of the unsaturated fatty acid is 10 or more and 30 or less. The base film according to claim 10, wherein the ratio of the dimer acid as a monomer unit constituting the polyester resin to all dicarboxylic acids constituting the monomer units constituting the polyester resin is 2 mole More than ear% and less than 25 mole%. The base film according to claim 1, wherein the thickness of the base film is not less than 20 μm and not more than 600 μm. A sheet for workpiece processing, characterized in that it has: The substrate film as described in any one of claims 1 to 12; The adhesive layer laminated on one surface side of the said base film. The workpiece processing sheet according to claim 13, wherein the workpiece processing sheet is a cutting sheet.