WO2022102636A1

WO2022102636A1 - Organic tin compound, method for producing same, liquid composition for forming euv resist film using same, and method for forming euv resist film

Info

Publication number: WO2022102636A1
Application number: PCT/JP2021/041260
Authority: WO
Inventors: 大貴古山; 常俊本田; 広隆平野; 一郎塩野; 真也白石
Original assignee: 三菱マテリアル株式会社; 三菱マテリアル電子化成株式会社
Priority date: 2020-11-12
Filing date: 2021-11-10
Publication date: 2022-05-19
Also published as: JPWO2022102636A1; TW202233640A

Abstract

This organic tin compound has an α-ray emission amount of at most 0.01 cph/cm2. This organic tin compound is represented by formula (1) in which R1 is a hydrocarbon group having 1-10 carbon atoms. This liquid composition for forming an EUV resist film is obtained by using said organic tin compound. When the liquid composition for forming an EUV resist film is 100 mass%, the tin content is preferably 0.05 mass% to 24 mass%. This method for forming an EUV resist film involves using said liquid composition for forming an EUV resist film, wherein an α-ray emission amount is at most 0.01 cph/cm2.

Description

An organic tin compound, a method for producing the same, a liquid composition for forming an EUV resist film using the organic tin compound, and a method for forming an EUV resist film.

The present invention relates to an organotin compound having a low α-ray emission amount and a method for producing the same. Further, the present invention relates to a liquid composition for forming an EUV resist film having a low α-ray emission amount using this organotin compound, and a method for forming an EUV resist film having a low α-ray emission amount. This application claims priority based on Japanese Patent Application No. 2020-188967 filed in Japan on November 12, 2020, and the contents thereof are incorporated herein by reference.

The resist film patterning technique in the semiconductor process has undergone a transition, and a lithography technique using KrF or ArF as a light source has been established, and semiconductor devices are still mass-produced using this technique. .. On the other hand, for example, according to the International Technology Roadmap for Semiconductor (ITRS), when the harp pitch falls below 40 nm, the conventional lithography technology cannot cope with it, and a new technology is required. One of them is EUV (Extreme Ultra Violet) lithography technology.

In the mass production of semiconductor devices using EUV lithography technology, many problems such as film surface roughness and film defects have been raised regarding resist films that form fine structures, and they are light sources for exposure equipment, mask materials, and resist materials. Development of improved techniques such as a liquid composition for forming a resist film has been widely made. Among them, the development of a resist film forming liquid composition corresponding to the next-generation EUV lithography technology capable of mass-producing high-quality resist films is in progress. At the stage of mass production in the EUV lithography technology, a chemically amplified resist (CAR), which is also the mainstream in the conventional lithography technology, has been used, but in the EUV lithography, it is compared with the conventional ArF lithography and the like. Therefore, there is a need to switch to a material system capable of high sensitivity, resolving power, and reduction of the roughness of the resist film surface due to differences in the principle of the light source and insufficient output of the exposure light source.

Therefore, in the latest resist material, a resist film-forming liquid composition, a method of introducing a structure that increases the light sensitivity by mainly applying CAR, or a metal species having a high EUV light absorption coefficient is introduced. A method or a method using a non-chemically amplified resist (Non-CAR) having a different mechanism has been proposed and is being developed. For EUV lithography technology, the challenges in developing next-generation resist materials are that the output of EUV light that finally reaches the mask is small, and that the photosensitive mechanism changes due to changes in light rays, so EUV It was necessary to form a resist film with high sensitivity to light. Therefore, development is being continued to improve sensitivity, and for example, a method of introducing Sn (tin) as a metal species having a high EUV light absorption coefficient into a resist film has been proposed (for example, Patent Document 1 (for example, Patent Document 1). See claim 1, abstract).). This method is an example of non-CAR.

Patent Document 1 describes an organic solvent and the formula R _z SnO _{(2- (z / 2)-(x / 2))} (OH) _x (where 0 <z ≦ 2 and 0 <(z + x) ≦ 4). With the first organic metal composition, represented by the formula R'nSnX _4-n (where n = 1 or 2), or a mixture thereof; the formula _MX'v (here, here). M is a metal selected from Groups 2-16 of the Periodic Table of the Elements, v = 2-6, and X'is a ligand having a hydrolyzable MX bond or them. A coating solution containing a hydrolyzable metal compound represented by (is a combination of) is disclosed.

This Patent Document 1 describes an organometallic precursor for creating a high resolution lithography pattern forming coating based on metal oxide hydroxyd chemistry, and the precursor composition thereof is generally under mild conditions. Containing ligands that can be easily hydrolyzed by water vapor or other OH source compositions, the organometallic precursors can generally be effective in forming high resolution patterns at relatively low radiation doses. It is described that it contains a radiation sensitive organoligand to tin, which can result in a coating that is particularly useful in EUV patterning.

Special Table 2019-500490

However, even when Sn (tin) shown in Patent Document 1 is introduced as a metal species having a high EUV light absorption coefficient in the resist film, when the above-mentioned half pitch is less than 40 nm, CAR or non- Even if CAR is used, pattern defects may occur. Generally, the causes of pattern defects when a resist film forming liquid composition, which is a resist material, is used include acid generation variation in the resist material, mask defects, presence of particles, resist pattern collapse, and line edge roughness (LER). , Random defects (stochastic defects, stochastic), and unexpected defects. Among these defects, in order to improve the mass productivity of high-quality resist films, it is particularly necessary to reduce random defects, and next-generation resists, including the elucidation of the mechanism of random defects, Development is in progress.

Assuming that the random defects of the resist pattern are caused by metal impurities, there is an example aiming at high purity of the resist film forming liquid composition, but in this example, the detection of metal impurities is a trace amount of the composition such as ICP-MS. The analysis is performed by the analysis method, and this analysis shows that it is less than the detection of metal impurities. In addition, even if metal impurities are contained in the order of ppb that cannot be detected by trace analysis, if metal impurities that can emit radiation due to radioactive decay are contained, radiation such as α-rays, β-rays, and γ-rays is emitted. There is a risk of

An object of the present invention is to provide an organotin compound having a low α-ray emission amount and a method for producing the same. Another object of the present invention is to provide a liquid composition for forming an EUV resist film using this organotin compound, which reduces pattern defects during pattern defects on a resist film by EUV lithography and has a low amount of α-ray emission. be. Yet another invention of the present invention is to provide a method for forming an EUV resist film having a low α-ray emission amount using this liquid composition.

As a result of diligently investigating the cause of the random defects, the present inventors have found that when tin (Sn) having a high absorption coefficient of EUV light is used as the resist material for the purpose of increasing the sensitivity of the resist material, Sn is used. Contains a small amount of Pb as an impurity, and α-rays emitted from ²¹⁰ Po generated from ²¹⁰ Pb, which is an isotope of this Pb, cause an unintended structural change in the resist film containing Sn, resulting in random defects. It was found that the present invention was reached.

The first aspect of the present invention is an organotin compound having an α-ray emission amount of 0.01 cph / cm ² or less.

The second aspect of the present invention is an invention based on the first aspect, which is an organotin compound represented by any of the following formulas (1) to (9).

In the above formula (1), R ¹ is a hydrocarbon group having 1 to 10 carbon atoms. In the above formula (2), R ² is a hydrocarbon group having 1 to 10 carbon atoms, a is 1 or 2, and b to d are integers having the same or different carbon atoms from 1 to 28, respectively. 0 ≦ n ≦ 4. In the above formula (3), R ² is a hydrocarbon group having 1 to 10 carbon atoms, p to s are integers having the same or different carbon atoms from 1 to 28, and t is 1 or more and 4 or less. .. Y has an anion species as a counterion. In the above formula (4), R ³ is a hydrocarbon group having 1 to 10 carbon atoms. In the above formula (5), R ⁴ is a hydrocarbon group having 1 to 10 carbon atoms. In the above formula (6), R ⁵ is a hydrocarbon group having 1 to 10 carbon atoms, and R ⁶ is a hydrocarbon group having 1 to 5 carbon atoms. In the above formula (7), R ⁷ is a hydrocarbon group having 1 to 10 carbon atoms. In the above formula (8), R ⁸ is a hydrocarbon group having 1 to 10 carbon atoms. In the above formula (9), R ⁹ is a hydrocarbon group having 1 to 10 carbon atoms.

The third aspect of the present invention is the EUV resist film forming liquid composition using the organic tin compound of the first aspect or the second aspect, and the EUV resist film forming liquid composition is 100% by mass. The EUV resist film-forming liquid composition has a tin content of 0.05% by mass or more and 24% by mass or less.

A fourth aspect of the present invention is a method for forming an EUV resist film having an α-ray emission amount of 0.01 cph / cm ² or less by using the EUV resist film forming liquid composition of the third aspect.

The fifth aspect of the present invention is (a) a step of synthesizing tin tetrachloride from metallic tin having an α-ray emission amount of 0.01 cf / cm ² or less, and (b) a monoalkyl tin oxide from the tin tetrachloride. Alternatively, it is a method for producing an organic tin compound including a step of synthesizing an alkyl tin trialkoxide, and in all the steps from the step (a) to the step (c), distillation for removing impurities from the composite is performed a plurality of times. The α-rays of the organic tin compound are controlled by α-ray control to shield the α-rays from the equipment and environment used in all the steps from the step (a) to the step (c). It is a method for producing an organic tin compound, characterized in that the amount released is 0.01 cph / cm ² or less.

The sixth aspect of the present invention is the invention based on the fifth aspect, in which multiple distillations measure the amount of α-ray emission of the compound or impurity fraction produced in each step, and the α-ray emission is achieved. This is a method for producing an organic tin compound, which is carried out until the amount becomes 0.01 cph / cm ² or less.

Since the organotin compound according to the first aspect of the present invention has an α-ray emission amount of 0.01 cph / cm ² or less, this organotin compound is used as a raw material for a liquid composition for forming an EUV resist film to form an EUV resist film. When a pattern is formed on the surface, a resist film with reduced random defects can be formed due to the small amount of α-ray emission.

Since the organic tin compound according to the second aspect of the present invention has a hydrocarbon group represented by any of the above-mentioned formulas (1) to (9) bonded to it, the amount of α-ray emission is 0.01 cph / cm. When an organic tin compound of ² or less is used as a raw material for a liquid composition for forming an EUV resist film and the coating film of this liquid composition is irradiated with EUV light, Sn-X (X = C, O, in the structural formula) is used. The OH) bond absorbs the irradiated EUV light with high efficiency and causes a structural change, and the solubility selectivity in the developing solution is greatly enhanced after the irradiation of the EUV light. In addition to this excellent effect, when this change occurs, a pattern is formed on the EUV resist film, and the amount of α rays emitted from the EUV resist film forming liquid composition is small, resulting in random defects. It is possible to form a resist film with reduced swelling.

Since the EUV resist film-forming liquid composition of the third aspect of the present invention uses the organic tin compound of the first aspect or the second aspect, when the EUV resist film-forming liquid composition is stored. It has the feature that the generation of reactive foreign substances due to the emission of α-rays is small. Further, since the tin content in the liquid composition is 0.05% by mass or more and 24% by mass or less, when the resist film made of this organotin compound is irradiated with EUV light, EUV light is absorbed with high efficiency. can do. In addition to this excellent effect, it is possible to form a resist film with reduced random defects when a pattern is formed on the EUV resist film due to a small amount of α-ray emission.

In the method for forming the EUV resist film according to the fourth aspect of the present invention, the formed EUV resist film uses the liquid composition for forming the EUV resist film according to the third aspect, so that the formed EUV resist film is α. It is possible to effectively utilize the irradiated EUV light without being affected by the line, and it is possible to achieve both high sensitivity and low defects.

In the method for producing an organic tin compound according to the fifth aspect of the present invention, tin tetrachloride is synthesized from metallic tin having an α-ray emission amount of 0.01 cf / cm ² or less, and monoalkyl tin oxide or alkyl is synthesized from tin tetrachloride. When synthesizing tin trialkoxide to produce an organic tin compound, distilling to remove impurities from the compound is performed multiple times in all steps, and α-rays are emitted to the equipment and environment used in all steps. By controlling the α-rays for shielding, the amount of α-ray emission of the organic tin compound can be reduced to 0.01 cf / cm ² or less, and the organic tin compound having this low amount of α-ray emission can be used to form an EUV resist film. When a pattern is formed on an EUV resist film by using it as a raw material for a liquid composition, a resist film having reduced random defects can be formed due to a small amount of α-ray emission.

In the method for producing an organic tin compound according to the sixth aspect of the present invention, the amount of α-ray emission of a compound or impurity distillate produced in each step by multiple distillations is measured, and the amount of α-ray emission is 0.01 cph. Since it is carried out until it becomes / cm ² or less, the α-ray emission amount of the final organic tin compound can be 0.01 cph / cm ² or less.

It is a flow chart which forms the EUV resist film using the liquid composition for forming an EUV resist film of this invention. It is a manufacturing flow diagram from the metal tin of this invention to obtaining the tin tetrachloride which emits a low α ray. It is a production flow diagram from the low α ray emission amount tin tetrachloride of this invention to the obtaining of the monoalkyl tin oxide of a low α ray emission amount. It is a flow chart from the metallic tin purified so as to emit a low α ray in an Example and a comparative example to the defect evaluation by a CD-SEM. It is a production flow diagram from the low α ray emission amount tin tetrachloride of this invention to the obtaining of the alkyl tin trialkoxide of a low α ray emission amount.

Next, a mode for carrying out the present invention will be described.

As shown in FIG. 1, the patterned (drawn) resist film of the present embodiment is made from metallic tin (Sn) as a starting material. Specifically, an organotin compound is first produced using metallic tin (Sn) having a low α-ray emission amount, and a liquid composition for forming an EUV resist film is produced from this organotin compound. The liquid composition is then coated on the substrate and the coating film is baked. Next, the baked resist film is exposed to EUV and subjected to development and post-treatment to obtain a patterned resist film.

[Low α-ray emission amount of metallic tin (Sn)]
The low α-ray emission amount of metallic tin (Sn) of the present embodiment is selected from those having an α-ray emission amount in the range of 0.01 cf / cm ² or less, preferably those having an α-ray emission amount of less than 0.0005 cf / cm ² . To. Examples of the metallic tin having a low α-ray emission amount include metallic tin produced by the method shown in Japanese Patent No. 6512354. In the present specification, the “α-ray emission amount” refers to a value measured for 96 hours with a gas flow type α-ray measuring device (MODEL-1950, lower limit of measurement: 0.0005 cph / cm ² ) manufactured by Alpha Science. The measurement was performed so that the temperature was within the range of 20 ° C to 30 ° C.

[Organic tin compounds with low alpha ray emission]
The organotin compound produced from the metallic tin having a low α-ray emission amount of the present embodiment is represented by any of the following formulas (1) to (9).

In formula (1), R ¹ is a hydrocarbon group having 1 to 10 carbon atoms. Specific examples of the organic tin compound represented by the formula (1) are the monobutyltin oxide (carbon number of R ¹ = 4) represented by the above formula (1-1) and the formula (1-2). Monoisopropyl tin oxide, monooctyl tin oxide represented by formula (1-3), mono-tert-butyl tin oxide represented by formula (1-4), monopropyl tin oxide represented by formula (1-5), Monopentyl tin oxide represented by formula (1-6), monohexyl tin oxide represented by formula (1-7), monoheptyl tin oxide represented by formula (1-8), mono represented by formula (1-9). Examples thereof include -sec-butyl tin oxide, monophenyl tin oxide represented by the formula (1-10), monononyl tin oxide represented by the formula (1-11), and monodecyl tin oxide represented by the formula (1-12). ..

In the organic tin compound represented by the following formula (2), R ² is a hydrocarbon group having 1 to 10 carbon atoms, a is 1 or 2, and b to d are the same or different carbon atoms 1 respectively. It is an integer of ~ 28, and 0 ≦ n ≦ 4. Specific examples of this multimeric organic tin compound include [(BuSn) ₁₂ O ₁₄ (OH) ₆ ] ²⁺ , [(PhSn) ₁₂ O ₁₄ (OH) ₆ ] ²⁺ , [(tert-BuSn) ₁₂ ). O ₁₄ (OH) ₆ ] ²⁺ , [(iso-PrSn) ₁₂ O ₁₄ (OH) ₆ ] ²⁺ , [(tert-AmSn) ₁₂ O ₁₄ (OH) ₆ ] ²⁺ , [(BuSn) ₆ O ₇ (OH) ₃ ] ⁺ , [(sec-BuSn) ₁₂ O ₁₄ (OH) ₆ ] ²⁺ , [(BuSn) ₁₈ O ₂₁ OH) ₉ ] ³⁺ , [(PhBuSn) ₂₄ O ₂₈ (OH) ₁₂ ] ⁴⁺ etc. can be mentioned. Here, Bu represents a butyl group, Ph represents a phenyl group, tert-Bu represents a tertiary butyl group, iso-Pr represents an isopropyl group, and tert-Am represents a tertiary rearyl group. When the organic tin compound represented by the formula (2) is used as a raw material for the liquid composition for forming an EUV resist film and a pattern is formed on the EUV resist film, a three-dimensional structure of tin is easily formed in the resist film. In addition, the small amount of α-ray emission makes it possible to form a resist film with reduced random defects.

In the organic tin compound represented by the following formula (3), R ² is a hydrocarbon group having 1 to 10 carbon atoms, p to s are integers having the same or different carbon atoms from 1 to 28, and t. Is 1 or more and 4 or less. Y has an anion species as a counterion. This anionic species is due to an acid used in synthesizing an organic tin compound, and examples of the acid include p-toluenesulfonic acid, phenylacetic acid, oxalic acid, malonic acid, and benzoic acid. Specific examples of this multimeric organic tin compound include [(BuSn) ₁₂ O ₁₄ (OH) ₆ ] (SO ₃ C ₆ H ₄ CH ₃ ) ₂ , [(sec-BuSn) ₁₂ O ₁₄ (OH) ₆ ] (SO ₃ C ₆ H ₄ CH ₃ ) ₂ , [(iso-PrSn) ₁₂ O ₁₄ (OH) ₆ ] (SO ₃ C ₆ H ₄ CH ₃ ) ₂ , [(tert-BuSn) ₁₂ O ₁₄ (OH) ) ₆ ] (C ₆ H ₅ CH ₂ COO) ₂ , [(sec-BuSn) ₁₂ O ₁₄ (OH) ₆ ] (OCOCOO), [(iso-PrSn) ₁₂ O ₁₄ (OH) ₆ ] (OCOCH ₂ COO) ), [(BuSn) ₁₂ O ₁₄ (OH) ₆ ] (HCOO) ₂ , [(BuSn) ₁₂ O ₁₄ (OH) ₆ ] (C ₆ H ₅ COO) ₂ , [(PhSn) ₁₂ O ₁₄ (OH) ₆ ] Cl ₂ , [(BuSn) ₆ O ₇ (OH) ₃ ] (SO ₃ C ₆ H ₄ CH ₃ ), [(BuSn) ₁₈ O ₂₁ (OH) ₉ ] (HCOO) ₃ , [(PhSn) ₂₄ O ₂₈ (OH) ₁₂ ] Cl ₄ can be mentioned. The organotin compound represented by the formula (3) can be selected by the functional group Y, and the sensitivity to EUV light can be adjusted by the selected functional group Y. In addition to this effect, when this organic tin compound is used as a raw material for a liquid composition for forming a resist film to form a pattern on an EUV resist film, a resist with a small amount of α-ray emission reduces random defects. A film can be formed.

In the organotin compound represented by the following formula (4), R ³ is a hydrocarbon group having 1 to 10 carbon atoms. Specific examples of this organotin compound include dibutyl tin oxide (carbon number of R ³ = 4) represented by the following formula (4-1). Since this organotin compound has two carbon chains added to the tin atom, it has a three-dimensional structure when the organotin compound is used as a raw material for a liquid composition for forming an EUV resist film to form an EUV resist film. Changes occur in the body. The sensitivity of the EUV resist film can be adjusted by utilizing the cleavage of the bond between Sn and C in a state where the amount of α-ray emission is small. In addition to this effect, a resist film with reduced random defects can be formed by reducing the amount of α-ray emission. In addition to the dibutyl tin oxide represented by the formula (4-1), the organic tin compounds of the formulas (4-2) to (4-8) are exemplified. Here, Bu is a butyl group, Et is an ethyl group, Me is a methyl group, Pr is a propyl group, Hex is a hexyl group, iso-Pr is an isopropyl group, tert-Bu is a tertiary butyl group, and sec-Bu is a secondary butyl. Represents each group.

In the organotin compound represented by the following formula (5), R ⁴ is a hydrocarbon group having 1 to 10 carbon atoms. Specific examples of this organotin compound include dibutyltin dichloride (carbon number of R ⁴ = 4) represented by the following formula (5-1). Similar to the organic tin compound represented by the above formula (4), this organic tin compound has two carbon chains added to the tin atom, so that the organic tin compound can be used as a liquid composition for forming an EUV resist film. When used as a raw material to form an EUV resist film, the three-dimensional structure changes. The sensitivity of the EUV resist film can be adjusted by utilizing the cleavage of the bond between Sn and C in a state where the amount of α-ray emission is small. In addition to this effect, a resist film with reduced random defects can be formed by reducing the amount of α-ray emission. In addition to the dibutyl tin dichloride represented by the formula (5-1), the organotin compounds of the formulas (5-2) to (5-8) are exemplified. Here, Bu is a butyl group, Et is an ethyl group, Me is a methyl group, Pr is a propyl group, Hex is a hexyl group, iso-Pr is an isopropyl group, tert-Bu is a tertiary butyl group, and sec-Bu is a secondary butyl. Represents each group.

In the organic tin compound represented by the following formula (6), R ⁵ is a hydrocarbon group having 1 to 10 carbon atoms, and R ⁶ is a hydrocarbon group having 1 to 5 carbon atoms. Specific examples of this organotin compound include monobutyltin triisopropoxide represented by the following formula (6-1) (carbon number of R ⁵ = 4, carbon number of R ⁶ = 3). This organic tin compound has an alkoxide structure, and when it is used as a raw material for a liquid composition for forming an EUV resist film and the liquid composition is applied and baked, the hydrolysis reaction easily proceeds. A tin-containing resist film having high sensitivity to EUV light can be formed, and a resist film having reduced random defects can be formed by reducing the amount of α-ray emission. In addition to the monobutyltin triisopropoxide represented by the formula (6-1), the organotin compounds of the formulas (6-2) to (6-22) are exemplified. Here, iso-Pr is an isopropyl group, Et is an ethyl group, Pr is a propyl group, Me is a methyl group, Bu is a butyl group, iso-Bu is an isobutyl group, sec-Bu is a secondary butyl group, and tert-Bu is a Tasha. Libutyl group, iso-Pentyl is isopentyl group, sec-Pentyl is secondary pentyl group, tert-Pentyl is Tashalipentyl group, 2-hexyl is 2-hexyl group, 1-heptyl is 1-heptyl group, 1-octyl is Represents each 1-octyl group.

In the organotin compound represented by the following formula (7), R ⁷ is a hydrocarbon group having 1 to 10 carbon atoms. Specific examples of this organotin compound include tetrabutyltin (R ⁷ having 4 carbon atoms) represented by the following formula (7-1). This organotin compound is an intermediate compound produced during the synthesis of the monobutyltin oxide represented by the above formula (1-1). In addition to the tetrabutyltin represented by the formula (7-1), the organic tin compounds of the formulas (7-2) to (7-8) are exemplified.

In the organotin compound represented by the following formula (8), R ⁸ is a hydrocarbon group having 1 to 10 carbon atoms. Specific examples of this organotin compound include monobutyltin trichloride (carbon number of R ⁸ = 4) represented by the following formula (8-1). This organotin compound is an intermediate compound produced during the synthesis of the monobutyltin oxide represented by the above formula (1-1). In addition to the monobutyltin trichloride represented by the formula (8-1), the organotin compounds of the formulas (8-2) to (8-11) are exemplified.

In the organotin compound represented by the following formula (9), R ⁹ is a hydrocarbon group having 1 to 10 carbon atoms. Specific examples of this organotin compound include monobutyltin triamide (carbon number of R ⁹ = 4) represented by the following formula (9-1). In addition to the monobutyltin triamide represented by the formula (9-1), the organotin compounds of the formulas (9-2) to (9-10) are exemplified.

[Manufacturing method of organotin compounds]
The organotin compound of the present embodiment produces tin chloride from metallic tin and is made from this tin chloride. As the metallic tin, it is preferable to use metallic tin having an α-ray emission amount of 0.01 cph / cm ² or less. By using such metallic tin, the number of distillations for removing impurities from the synthetic material described later can be reduced. The metallic tin at this time is preferably in the form of granules, foils, or powders in order to enhance the reactivity. As a method for producing tin chloride from metallic tin and a method for producing an organic tin compound from this tin chloride, a known method is adopted. However, in the present embodiment, in all of these manufacturing processes, distillation for removing impurities from the synthetic substance is performed a plurality of times, and α rays are used to shield α rays from the equipment and environment used in all the processes. It is essential that management be done.

Here, the fact that distillation for removing impurities from a compound is performed a plurality of times in all manufacturing processes means that the amount of α-ray emission of the compound or impurity distillate generated in each step is measured, and the amount of α-ray emission is calculated. It means repeating distillation multiple times until it becomes 0.01 cph / cm ² or less. Distillation is preferably performed at a temperature slightly lower than 130 ° C., which is the temperature at which Po, which is an α-ray source, sublimates. In addition, the fact that α-ray control is performed on the equipment in all manufacturing processes means that the equipment to be used is pickled and then alkaline-cleaned before each process.
For example, an aqueous solution of sulfuric acid or an aqueous solution of hydrochloric acid having a concentration of 15% by mass to 30% by mass at a temperature of 45 ° C. to 55 ° C. is supplied to an instrument placed in a washing tank for 60 to 80 minutes for acid cleaning, and then ion-exchanged water is applied at room temperature. Then, the washed equipment is supplied with an aqueous solution of ammonium carbonate, an aqueous solution of ammonium bicarbonate, water of ammonia, etc. at a concentration of 35% by mass to 41% by mass at a temperature of 30 ° C. to 40 ° C. for 40 to 50 minutes for alkaline cleaning. do. After that, it was washed with ion-exchanged water at room temperature, washed with a washing liquid containing a surfactant at room temperature, washed again with ion-exchanged water at room temperature, and then air passed through a HEPA filter was supplied. Dry the washed equipment.
The environment used is a highly clean environment. For example, a clean room or an environment of a cleanliness class of Class 6 or higher based on the international standard ISO 14644-1: 2015 can be mentioned. In consideration of the safety of the substances produced, the substances unstable in the air should be handled by substituting with an inert gas or in a glove box in which the amount of water is controlled. The environment in which it is used should be an environment that shields α rays that may be mixed into the equipment and facilities used in all manufacturing processes.

As an example of a method for producing tin chloride from metallic tin and a method for producing an organic tin compound from this tin chloride, production of monobutyltin oxide (number of carbon atoms of R ¹ = 4) represented by the above formula (1-1). The method will be described with reference to FIGS. 2, 3 and the following equations (10) to (12).

First, granular, foil-like or powder-like metallic tin (Sn) is prepared by using the above-mentioned acid-cleaning and then alkali-cleaning instruments. As the metallic tin, it is preferable to use a metallic tin having a low α-ray emission amount of 0.01 cph / cm ² or less. This metallic tin is reacted with chlorine (Cl ₂ ) gas to synthesize tin tetrachloride (SnCl ₄ ) as shown in FIG. 2 and the formula (10). During this synthesis, for the purpose of removing radioactive elements such as Pb, U, Th, and Po that can be α-ray sources or their parent nuclides, until the amount of α-ray emission of tin tetrachloride is 0.01 cph / cm ² or less. Distillation is repeated multiple times. The number of distillations is determined by the α-ray measurement value.

FIG. 2 shows a production flow chart from metal tin having a low α-ray emission amount to obtaining tin tetrachloride having a low α-ray emission amount. Specifically, as shown in FIG. 2 and the formula (10), tin tetrachloride having a low α-ray emission amount is reacted with chlorine gas to distill tin tetrachloride in one distillation. Then, the distilled tin tetrachloride is distilled and purified to obtain purified tin tetrachloride. The amount of α rays emitted from this purified tin tetrachloride is measured.
To measure the amount of α-ray emission, tin tetrachloride is dissolved in a methanol solution and sprayed in the air onto a clean glass substrate surface heated to 700 ° C. using a glass atomizer. At that time, it is possible to use a method of forming a tin oxide thin film as an electrode material. That is, a tin oxide (IV) film is formed in an environment where the generated hydrogen chloride gas can be sucked, a spray temperature of 20 ° C. to 25 ° C., and a humidity of 48% to 53%, and the α of this tin oxide film is formed. Measure the amount of ray emitted. If the amount of α-ray emission exceeds 0.01 cph / cm ² , distillation and measurement of the amount of α-ray emission are repeated. In this way, tin tetrachloride with a low α-ray emission amount can be obtained.

FIG. 3 shows a production flow chart from tin tetrachloride having a low α-ray emission amount to obtaining a monoalkyl tin oxide having a low α-ray emission amount. Here, the process until monobutyltin oxide is obtained as monoalkyltin oxide will be described. First, in order to add a carbon chain to a tin atom, purified tin tetrachloride (SnCl ₄ ) is reacted with an organic magnesium halide of a Grignard reagent to obtain tetraalkyl tin as shown in the formula (11). Synthesize tetrabutyltin. Here, butylmagnesium chloride is used as the organic magnesium halide.

The synthesized tetrabutyl tin is reacted with tin tetrachloride (SnCl ₄ ) synthesized by the formula (10) to synthesize a monobutyl tin trichloride, which is a monoalkyl tin trichloride, as shown in FIG. 3 and the formula (12). do. In this synthesis, tributyltin chloride is produced as a by-product.

The reaction mixture represented by the formula (12) is concentrated and precision distillation is repeated a plurality of times to obtain monobutyltin trichloride. This monobutyltin trichloride is dissolved in an organic solvent, an alkaline aqueous solution is added dropwise to this solution and stirred to obtain a precipitate, which is then solid-liquid separated and monobutyltin trichloride as shown in FIG. 3 and formula (13). Obtain monobutyltin oxide from. For the above-mentioned purposes, precision distillation is repeated a plurality of times until the α-ray emission amount becomes 0.01 cph / cm ² or less to obtain a monobutyltin oxide having a low α-ray emission amount.

An example of using butylmagnesium chloride for synthesizing the monobutyltin oxide represented by the formula (1-1) synthesized by the formula (13) has been described. Next, the following other than the butylmagnesium chloride are described below. The organic magnesium halides are shown in the formulas (14) to (21). Using these organomagnesium halides, the amount of α-ray emission represented by the above-mentioned formulas (1-2) to (1-9) is 0.01 cph / cm ² or less in the same manner as in the above-mentioned method. Organic tin compounds are synthesized.

The formula (14) is isopropylmagnesium chloride, from which the monoisopropyltin oxide represented by the above formula (1-2) is produced.
The formula (15) is octylmagnesium bromide, and the monooctyltin oxide represented by the above-mentioned formula (1-3) is produced from the octylmagnesium bromide.
The formula (16) is tertiary butyl magnesium chloride, and the mono-tert-butyl tin oxide represented by the above formula (1-4) is produced from the tertiary butyl magnesium chloride.
Formula (17) is propylmagnesium bromide, and from this propylmagnesium bromide, the monopropyl tin oxide represented by the above-mentioned formula (1-5) is produced.
The formula (18) is pentylmagnesium bromide, and the monopentyltin oxide represented by the above-mentioned formula (1-6) is produced from the pentylmagnesium bromide.
Formula (19) is hexyl magnesium bromide, from which hexyl magnesium bromide produces the monohexyl tin oxide represented by formula (1-7) above.
Formula (20) is magnesium bromide, and from this magnesium bromide, monoheptyl tin oxide represented by the above formula (1-8) is produced.
Formula (21) is bromide secondalibutylmagnesium, and the mono-sec-butyltin oxide represented by the above-mentioned formula (1-9) is produced from this bromide secondalibutylmagnesium.

[Method for producing a liquid composition for forming an EUV resist film]
In the liquid composition for forming an EUV resist film of the present embodiment, the above organic tin compound is added and mixed with an organic solvent in a closed space where α-ray control is performed with respect to the instrument and the environment, and the mixture is centrifuged or a syringe filter. By removing the insoluble solid, the α-ray emission amount is 0.01 cph / cm ² or less. A liquid composition for forming an EUV resist film having a predetermined viscosity can be obtained depending on the mixing ratio of the organic tin compound and the organic solvent. When the EUV resist film forming liquid composition is 100% by mass, the tin content is 0.05% by mass or more and 24% by mass or less. The tin content is preferably 0.5% by mass to 9% by mass. If it is less than 0.05% by mass, it becomes difficult to efficiently absorb EUV light irradiated to the resist film made of this organic tin compound. Further, if it exceeds 24% by mass, the EUV resist film forming liquid composition becomes unstable from the viewpoint of the solubility of the tin compound, and the metal residue after etching becomes a problem. Here, the tin content is a content using a value converted as the tin content contained in the organic tin compound.

The organic solvent used in the liquid composition for forming an EUV resist film is xylene, an aromatic compound such as toluene, ethers such as methylphenyl ether or methanol, 2-methoxy-1-methylethyl acetate, and the like. Examples thereof include esters such as ethyl acetate, ethyl lactate and n-butyl acetate, alcohols such as 4-methyl-2-propanol, 1-butanol, methanol, isopropyl alcohol, 1-propanol and butanol, and ketones such as methyl ethyl ketone.

[Method from coating to developing of EUV resist film forming liquid composition]
The EUV resist film obtained by the above method by a method such as spin coating on a cleaned substrate after applying a photosensitive substance in a state where α-ray control is performed for the equipment and the environment. The forming liquid composition is coated. A resist film is formed by holding and baking this coating film at a temperature of 120 ° C. to 210 ° C. for 3 to 10 minutes. The coating amount of the liquid composition at the time of coating is adjusted so that the film thickness after baking is 5 nm to 90 nm. The formed resist film is exposed to EUV and subjected to post-treatment such as development to produce a resist film having a patterned α-ray emission amount of 0.01 cph / cm ² or less.

In the above embodiment, the resist film is formed by using the liquid composition for forming an EUV resist film using the organic tin compound of the present invention, but in addition to this, the organic tin compound of the present invention (for example, A resist film can also be formed by a chemical vapor deposition (CVD) method or an atomic layer deposition (ALD) method using the monoalkyl tin trichloride represented by the above formula (8).

Next, examples of the present invention will be described in detail together with comparative examples. First, the organotin compounds represented by the above-mentioned formulas (1-1) to (1-9), which are organotin compounds, are the examples and comparative examples of the organotin oxide compounds, and the organotin compounds obtained in the examples and the comparative examples. The results of the amount of α-ray emission will be described, and then the liquid composition for forming an EUV resist film using the organotin trialkoxide compounds represented by the formulas (1-1) to (1-9) and (9) will be described. The results after film formation of the test example and the comparative test example and the EUV resist film forming liquid composition obtained in these test examples and the comparative test example will be described.

FIG. 4 shows a flow chart from metallic tin purified to emit low α rays in Examples and Comparative Examples to defect evaluation by CD-SEM (Critical Dimensions-SEM).

[Examples / Comparative Examples of Monobutyltin Oxide (Organic Tin Oxide Compound) of Formula (1-1)]
<Example 1-1>
Tin tetrachloride was synthesized from metallic tin.
First, a three-necked glass flask with a volume of 500 mL and another flask with α-ray control were prepared. Specifically, the three-necked flask to be used and another flask were pickled and then alkaline-washed. Sulfuric acid first prepared to a concentration of 15% by mass was raised to 45 ° C., and this sulfuric acid was circulated for 60 minutes in the part where the product of the three-necked flask to be used and the product of another flask came into contact, and this contact part was circulated. Washed. Subsequently, the ammonium carbonate solution prepared to a concentration of 38% by mass was circulated at room temperature for 40 minutes, and the contact portion was washed. Then, after cleaning with ion-exchanged water, the cleaning treatment was performed with a cleaning liquid containing a surfactant, the mixture was replaced with ion-exchanged water again, and then the drying treatment was performed with a dryer.

The above three α-ray controlled ports were used as a chlorine gas supply port, a nitrogen gas supply port, and a connection port for connecting to another flask. 15 g of granular metallic tin as a starting material was placed in the three-necked flask. This metallic tin was less than 0.0005 cf / cm ² . After purging the inside of the flask with nitrogen gas, 0.3 mol of chlorine gas was flowed in to react metallic tin with chlorine gas. White smoke was generated and the reaction was sufficient, and tin chloride was synthesized from metallic tin.
The three-necked flask was heated to around 120 ° C., which is close to the boiling point of tin tetrachloride. As a result, only gaseous tin tetrachloride is obtained, and by flowing nitrogen gas from the nitrogen gas supply port, gaseous tin tetrachloride flows into another flask maintained at a temperature of 10 ° C. from the flask connection port. rice field. The gaseous tin tetrachloride was cooled by another flask to obtain 23.5 g of colorless to yellowish brown liquid tin tetrachloride (SnCl ₄ ). Liquid tin tetrachloride was distilled until the amount of α-ray emission was 0.01 cph / cm ² or less. The number of distillations was two, and the distillation was performed at a temperature of 128 ° C., which is lower than the sublimation temperature of Po at 130 ° C. This reaction is represented by the above formula (10).

Next, tetrabutyltin was synthesized from the tin tetrachloride.
In a 2 L volumetric flask consisting of a stirrer, a reflux condenser and an isobaric dropping funnel, which is α-ray controlled, a tetrahydrofuran solution of butylmagnesium chloride, which is a Grignard reagent, is placed in a two-necked flask, and 2.8 of butylmagnesium chloride. I put it in a mole. 250 mL of toluene was added thereto, and the mixture was heated to 110 ° C. to distill off the solvent in the Grignard reagent. 0.65 mol of liquid tin tetrachloride having a low α-ray emission amount obtained by the above synthesis was added dropwise thereto, and the mixture was heated under reflux at a temperature of 110 ° C. for 2 hours. After the steam temperature reached 110 ° C., heating was terminated and the mixture was cooled. The obtained mixture was filtered, toluene was distilled off from the filtrate, and then precision distillation was further carried out at a temperature of 114 ° C. for 1 hour. After removing the by-products, the residue was separated, and the composition of the separated organic tin compound was analyzed by GC-MS (Gas Chromatography Mass Spectrometry). As a result, it was confirmed that most of the components were tetrabutyltin. The yield of tetrabutyltin in this synthesis was 93.2%, and the purity determined from GC-MS (hereinafter referred to as GC purity) was 99.6%. By this synthesis, 210.4 g of liquid tetrabutyltin was obtained. The number of distillations was two. This reaction is represented by the above formula (11).

Next, monobutyltin trichloride was synthesized from the above tetrabutyltin.
130 g of tin tetrachloride and 200 mL of benzene, which were initially obtained in a low α-ray emission amount, were placed in a 1 L volume four-necked flask consisting of an α-ray controlled stirrer, thermometer, cooler and dropping funnel. I put in. While stirring these, 86.1 g of tetrahydrofuran (hereinafter referred to as THF) was added dropwise at room temperature using a dropping funnel. Immediately after the reaction of tin tetrachloride with THF began, the reaction product was cooled to remove the heat of reaction. After the addition of THF was completed, the reaction product was heated and the reaction was carried out under reflux for 30 minutes. Subsequently, 173.6 g of tetrabutyltin obtained in the above synthesis was added dropwise over 30 minutes while refluxing at a temperature of 82 ° C., and then the reaction was carried out for 1 hour. As a result of composition analysis of the reaction product of the obtained brown transparent solution by GC-MS, monobutyltin trichloride and tributyltin chloride were confirmed. The production ratio of monobutyltin trichloride and tributyltin chloride was about 1: 1 in terms of substance amount conversion ratio. After concentrating this reaction product and distilling off benzene and THF, precision distillation was carried out under reduced pressure until the amount of α-ray emission was 0.01 cf / cm ² or less, and the boiling point was 92 ° C. to 94 ° C./10 mmHg. As a distillate, 138 g of monobutyltin trichloride was obtained. The yield of monobutyltin trichloride in this synthesis was 97.8%, the GC purity was 99.4%, and the number of distillations was two. This reaction is represented by the above formula (12).

Further, monobutyltin oxide was produced from the above monobutyltin trichloride.
20 g of monobutyltin trichloride obtained in the above synthesis is dissolved in 900 mL of ethanol, and while cooling and stirring the solution so that the temperature is 40 ° C. or lower, 12 g of ammonia water having a concentration of 28% by mass is added to this solution for 40 minutes. And dropped. After further stirring for 30 minutes, the temperature was raised to 55 ° C., and the mixture was stirred at this temperature for 4 hours. The resulting precipitate was suction filtered, washed with ion-exchanged water and centrifuged. The white solid obtained after centrifugation was dried under reduced pressure at 80 ° C. for 18 hours to obtain 8.8 g of monobutyltin oxide. The production of this monobutyltin oxide is represented by the above formula (13).

<Example 1-2>
As a starting material, granular metallic tin having an α-ray emission amount of 0.002 cf / cm ² was used. Except for this, monobutyltin oxide was produced in the same manner as in Example 1-1.

<Example 1-3>
As a starting material, granular metallic tin having an α-ray emission amount of 0.01 cph / cm ² was used. Except for this, monobutyltin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 1-1>
As a starting material, a commercially available product of granular metallic tin having an α-ray emission amount of 0.5 cph / cm ² was used. Except for this, monobutyltin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 1-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. However, unlike Example 1-1, the total number of distillations was 2 without performing α-ray control for the equipment and environment used. Except for this, monobutyltin oxide was produced in the same manner as in Example 1-1.

[Examples / Comparative Examples of Monoisopropyl Tin Oxide (Organic Tin Oxide Compound) of Formula (1-2)]
<Example 2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, isopropylmagnesium chloride was used instead of the butylmagnesium chloride used in Example 1-1. The total number of distillations was four. Except for this, monoisopropyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 2-1>
As a starting material, granular metallic tin having an α-ray emission amount of 0.5 cf / cm ² , which is the same commercially available product as in Comparative Example 1-1, was used. Further, instead of the butyl magnesium chloride used in Example 1-1, the same isopropyl magnesium chloride as in Example 2 was used. Except for this, monoisopropyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 2-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butyl magnesium chloride used in Example 1-1, the same isopropyl magnesium chloride as in Example 2 was used. However, unlike Example 1-1, the total number of distillations was 2 without performing α-ray control for the equipment and environment used. Except for this, monoisopropyl tin oxide was produced in the same manner as in Example 1-1.

[Examples / Comparative Examples of Monooctyl Tin Oxide (Organic Tin Oxide Compound) of Formula (1-3)]
<Example 3>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, octylmagnesium bromide was used. The total number of distillations was four. Except for this, monooctyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 3-1>
As a starting material, granular metallic tin having an α-ray emission amount of 0.5 cf / cm ² , which is the same commercially available product as in Comparative Example 1-1, was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same octylmagnesium bromide as in Example 3 was used. Except for this, monooctyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 3-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same octylmagnesium bromide as in Example 3 was used. However, unlike Example 1-1, the total number of distillations was 2 without performing α-ray control for the equipment and environment used. Other than that, monoioctyl tin oxide was produced in the same manner as in Example 1-1.

[Examples / Comparative Examples of Mono-tert-Butyl Tin Oxide (Organic Tin Oxide Compound) of Formula (1-4)]
<Example 4>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, tertiary butylmagnesium chloride was used. The total number of distillations was four. Except for this, mono-tert-butyltin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 4-1>
As a starting material, granular metallic tin having an α-ray emission amount of 0.5 cf / cm ² , which is the same commercially available product as in Comparative Example 1-1, was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same tertiary butylmagnesium chloride as in Example 4 was used. Except for this, mono-tert-butyltin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 4-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same tertiary butylmagnesium chloride as in Example 4 was used. However, unlike Example 1-1, the total number of distillations was 2 without performing α-ray control for the equipment and environment used. Except for this, mono-tert-butyltin oxide was produced in the same manner as in Example 1-1.

[Examples / Comparative Examples of Monopropyl Tin Oxide (Organic Tin Oxide Compound) of Formula (1-5)]
<Example 5>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, propylmagnesium bromide was used. The total number of distillations was 5. Except for this, monopropyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 5-1>
As a starting material, granular metallic tin having an α-ray emission amount of 0.5 cf / cm ² , which is the same commercially available product as in Comparative Example 1-1, was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same propylmagnesium bromide as in Example 5 was used. Except for this, monopropyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 5-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same propylmagnesium bromide as in Example 5 was used. However, unlike Example 1-1, the total number of distillations was 3 without performing α-ray control for the equipment and environment used. Except for this, monopropyl tin oxide was produced in the same manner as in Example 1-1.

[Examples / Comparative Examples of Monopentyl Tin Oxide (Organic Tin Oxide Compound) of Formula (1-6)]
<Example 6>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, pentylmagnesium bromide was used. The total number of distillations was four. Except for this, monopentyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 6-1>
As a starting material, granular metallic tin having an α-ray emission amount of 0.5 cf / cm ² , which is the same commercially available product as in Comparative Example 1-1, was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same pentyl magnesium bromide as in Example 6 was used. Except for this, monopentyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 6-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same pentyl magnesium bromide as in Example 6 was used. However, unlike Example 1-1, the total number of distillations was 3 without performing α-ray control for the equipment and environment used. Except for this, monopentyl tin oxide was produced in the same manner as in Example 1-1.

[Examples / Comparative Examples of Monohexyl Tin Oxide (Organic Tin Oxide Compound) of Formula (1-7)]
<Example 7>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, hexylmagnesium bromide was used. The total number of distillations was four. Except for this, monohexyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 7-1>
As a starting material, granular metallic tin having an α-ray emission amount of 0.5 cf / cm ² , which is the same commercially available product as in Comparative Example 1-1, was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same hexylmagnesium bromide as in Example 7 was used. Except for this, monohexyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 7-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same hexylmagnesium bromide as in Example 7 was used. However, unlike Example 1-1, the total number of distillations was 3 without performing α-ray control for the equipment and environment used. Except for this, monohexyl tin oxide was produced in the same manner as in Example 1-1.

[Examples / Comparative Examples of Monoheptyl Tin Oxide (Organic Tin Oxide Compound) of Formula (1-8)]
<Example 8>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, heptylmagnesium bromide was used. The total number of distillations was 5. Except for this, monoheptyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 8-1>
As a starting material, granular metallic tin having an α-ray emission amount of 0.5 cf / cm ² , which is the same commercially available product as in Comparative Example 1-1, was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same heptylmagnesium bromide as in Example 8 was used. Except for this, monoheptyl tin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 8-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same heptylmagnesium bromide as in Example 8 was used. However, unlike Example 1-1, the total number of distillations was 3 without performing α-ray control for the equipment and environment used. Except for this, monoheptyl tin oxide was produced in the same manner as in Example 1-1.

[Examples / Comparative Examples of Mono-sec-Butyl Tin Oxide (Organic Tin Oxide Compound) of Formula (1-9)]
<Example 9>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the bromide secondalibutylmagnesium was used. The total number of distillations was four. Except for this, mono-sec-butyltin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 9-1>
As a starting material, granular metallic tin having an α-ray emission amount of 0.5 cf / cm ² , which is the same commercially available product as in Comparative Example 1-1, was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same second bromide butylmagnesium as in Example 9 was used. Except for this, mono-sec-butyltin oxide was produced in the same manner as in Example 1-1.

<Comparative Example 9-2>
As a starting material, granular metallic tin having the same α-ray emission amount of less than 0.0005 cf / cm ² as in Example 1-1 was used. Further, instead of the butylmagnesium chloride used in Example 1-1, the same second bromide butylmagnesium as in Example 9 was used. However, unlike Example 1-1, the total number of distillations was 3 without performing α-ray control for the equipment and environment used. Except for this, mono-sec-butyltin oxide was produced in the same manner as in Example 1-1.

The α-ray emission amount of 29 kinds of organic tin oxide compounds obtained in Examples 1-1 to 1-3, Examples 2 to 9 and Comparative Examples 1-1 to 9-2 was measured. The results are shown in Table 1 below. Table 1 shows the types of organotin compounds, the amount of α-ray emission of metallic tin as a starting material, the implementation or non-implementation of α-ray control during production, the number of distillations during production, and the α of organotin oxide compounds. The amount of ray emitted is described. The number of distillations at the time of manufacture is the cumulative number of times.

As is clear from Table 1, Comparative Example 1-1, Comparative Example 2-1 and Comparative Example 3-1, Comparative Example 4-1 and Comparative Example 5-1, Comparative Example 6-1 and Comparative Example 7-1, In Comparative Example 8-1 and Comparative Example 9-1, since monoalkyltin oxide was produced from metallic tin as a starting material having an α-ray emission amount of 0.5 cf / cm ² , α-ray control was performed at the time of production. Nevertheless, the amount of α-ray emission of the final target substance, monoalkyltin oxide, was in the range of 0.013 cf / cm ² to 0.024 cf / cm ² , which was high.
In addition, Comparative Example 1-2, Comparative Example 2-2, Comparative Example 3-2, Comparative Example 4-2, Comparative Example 5-2, Comparative Example 6-2, Comparative Example 7-2, Comparative Example 8-2 and In Comparative Example 9-2, since α-ray control was not performed at the time of production, even though monoalkyl tin oxide was produced from metallic tin as a starting material having an α-ray emission amount of less than 0.0005 cf / cm ² . The amount of α-ray emission of the final target substance, monoalkyltin oxide, was in the range of 0.011 cf / cm ² to 0.017 cf / cm ² , which was high.

On the other hand, in Examples 1-1 to 9, monoalkyltin oxide is produced from metallic tin as a starting material having an α-ray emission amount of less than 0.01 cf / cm ² , and α-ray control is performed at the time of production. The amount of α-ray emission of monoalkyltin oxide, which is the final target substance, was in the range of 0.0020 cf / cm ² or less, which was low.

[Example of Production of Liquid Composition for Forming EUV Resist Film from Organic Tin Oxide Compounds of Formulas (1-1) to (1-9)]
<Test Example 1 to Test Example 9, Comparative Test Example 1-1 to Comparative Test Example 9-2>
Using the 27 kinds of organotin oxide compounds obtained in Examples 1-1, Examples 2 to 9 and Comparative Examples 1-1 to 9-2, Test Examples 1 to 9 and Comparative Test Examples. Twenty-seven kinds of EUV resist film forming liquid compositions of 1-1 to Comparative Test Example 9-2 were produced.
Specifically, in an airtight space where α-ray control is applied to the equipment and the environment, 27 kinds of organic tin compounds are converted from the molecular weight and weighed 0.002 mol each, and each organic tin compound is 29. It was added to 0.8 mL of methyl ethyl ketone and stirred for 24 hours to mix to dissolve the organic tin compound. Next, the obtained mixture was centrifuged at 3000 rpm for 30 minutes to produce 27 kinds of EUV resist film forming liquid compositions of Test Examples 1 to 9 and Comparative Test Examples 1-1 to 9-2. .. Table 2 below shows the types of the organic tin oxide compound used in the above example, the amount of α rays emitted thereof, and the content ratio of tin in the liquid composition.

[Example of Production of Cluster-Type Tin Compound from Monobutyltin Oxide (Organic Tin Oxide Compound) of Formula (1-1)]
<Test Example 10-1 to Test Example 10-2, Comparative Test Example 10-1 to Comparative Test Example 11-2>
From the three types of monobutyltin oxides obtained in Examples 1-1 and Comparative Examples 1-1 and 1-2 described above, Test Examples 10-1 to 10 have different tin content ratios in the liquid composition. -2, An EUV resist film-forming liquid composition containing 6 types of cluster-type or cage-type tin compounds of Comparative Test Examples 10-1 to 11-2 was produced. Specifically, 25 g of each of the above three types of monobutyltin oxides was weighed. This monobutyltin oxide and 5.8 g of p-toluenesulfonic acid as an acid were placed in a round bottom flask having a volume of 500 mL to which a Dean-Stark apparatus was connected and mixed. After reacting the mixture under reflux with toluene for 48 hours, the unreacted product was removed using a filter with a filtration accuracy of 10 μm to 16 μm. Then, 2-propanol was used as a solvent to dissolve the tetrabutylammonium hydroxide, and the solution was crystallized at a temperature of −15 ° C. Finally, THF was added to the crystallized product and the solvent was removed under reduced pressure to produce a compound consisting of three types of monobutyltin oxides.

These compounds were subjected to dynamic light scattering (DLS) analysis of the precursor solution using a nanoparticle analyzer (nanoPartica SZ-100V2 manufactured by HORIBA). As a result, the above compounds were consistent with the monomodal distribution of particles with an average diameter of about 2 nm, and the diameter reported for the 12-mer butyltin hydrooxide oxide polyatomic cation (Eychenne-Baron et al., Organometallics, It was confirmed that the structure ([(BuSn) ₁₂ O ₁₄ (OH) ₆ ] (p-CH ₃ C ₆ H ₄ SO ₃ ) ₂ ) was almost the same as that of 19,1940-1949 (2000)). That is, it was confirmed that a 12-mer cluster-type or cage-type tin compound was synthesized.

A liquid composition for forming an EUV resist film was prepared using this synthesized 12-mer cluster-type or cage-type tin compound. Specifically, the above-mentioned cluster type or cage type tin compound is weighed so that the tin content ratio is contained in the range of 0.05% by mass or more and 24% by mass or less in this liquid composition, and the tin compound is subjected to 29. Tests with different tin content in liquid compositions by dissolving in 8 mL of methyl ethyl ketone, stirring in a closed space for 24 hours, and removing insoluble solids with a 0.45 μm filtration precision syringe filter. Six kinds of EUV resist film forming liquid compositions of Example 10-1 to Test Example 10-2 and Comparative Test Example 10-1 to Comparative Test Example 11-1 were produced. The types of the organic tin oxide compound used in the above example, the amount of α rays emitted thereof, and the content ratio of tin in the liquid composition are shown in Table 3 below.

[Production example of t-butyl tin tributoxide from tin tetrachloride and lithium dimethylamide]
FIG. 5 shows a production flow chart from tin tetrachloride having a low α-ray emission amount to obtaining an alkyl tin trialkoxide having a low α-ray emission amount.
<Example 10-1>
The organic tin trialkoxide compound t-butyl tin tributoxide was synthesized from tin tetrachloride and lithium dimethylamide. In this Example 10, tin tetrachloride (SnCl ₄ ) having an α-ray emission amount of less than 0.0005 cf / cm ² was used in order to obtain t-butyl tin tributoxide.

Specifically, first, in a glove box filled with an argon atmosphere, lithium dimethylamide (manufactured by Sigma-Aldrich) and low α-ray treatment were performed, and the amount of α-ray emission was less than 0.0005 cph / cm ² . Tetrakis tin dimethylamide was synthesized using a certain tin tetrachloride (SnCl ₄ ). This reaction is represented by the following formula (22). Detailed synthesis methods are described, for example, in Journal of the Chemical Society, 1965, p. 1944.

Then, using the synthesized tetrakis tin dimethylamide, the t-butyl tin trimethyl amide represented by the above formula (9-2) required for the synthesis of t-butyl tin tributoxide was synthesized. This reaction is represented by the following formula (23).
Due to the high reactivity of the starting material, the reaction was carried out in a glove box filled with an argon atmosphere. The synthesized tetrakis tin dimethylamide is purified using t-butylmagnesium chloride (see formula (16)), which is a Grignard reagent in THF, and then distilled to obtain the desired t-butyltin trimethyl. Amides were selectively collected. In the case of t-butyltin trimethylamide in this example, the distillation operation was carried out by holding at 60 ° C. under a pressure of 0.5 mmHg, and the first fraction was not separated and only the intermediate fraction was separated. I took it. The yield was 58%.

Next, t-butyl tin tributoxide was synthesized by substituting the purified t-butyl tin trimethylamide with an alcohol. This reaction is represented by the following formula (24).
The dehydrated 1-butanol was slowly added to the purified t-butyltin trimethylamide in a glove box in which the atmosphere was made inert with argon, and the substitution reaction was carried out in an ice bath at −5 ° C. During the reaction, the valve was opened to relieve the pressure of the gas generated from the alcohol. After completion of the reaction, the temperature was returned to room temperature to volatilize the solvent, and then the produced t-butyl tin tributoxide was maintained at 90 ° C. under a pressure of 0.5 mmHg and recovered by distillation. Distillation is repeated multiple times until the α-ray emission of t-butyltin tributoxide is 0.01 cph / cm ² or less.
FIG. 5 is a production flow chart showing the process of obtaining an alkyl tin trialkoxide having a low α-ray emission amount from tin tetrachloride having a low α-ray emission amount. Specifically, as shown in FIG. 5, the first production flow diagram is shown. Distillate-purified t-butyltin tributoxide was applied to a clean Si wafer surface in the air, fired, and then hydrolyzed, and the amount of α-ray emission of this hydrolyzate was measured. When the amount of α-ray emission exceeded 0.01 cph / cm ² , distillation was repeated.
In Example 10-1, α-ray control was performed until the final target substance was synthesized, in order to prevent contamination with an α-ray source and to prevent an increase in the amount of α-ray emission. In the reaction pathways of the formula (22), the formula (23) and the formula (24), the total number of distillations was 5 times each.

<Example 10-2>
As a starting material for synthesizing t-butyltin trimethylamide, tin tetrachloride (SnCl ₄ ) having an α-ray emission amount of 0.002 cf / cm ² was used. Other than that, t-butyl tin tributoxide was obtained in the same manner as in Example 10-1.

<Comparative Example 10-1>
As a starting material for synthesizing t-butyltin trimethylamide, tin tetrachloride (SnCl ₄ ) having an α-ray emission amount of 0.5 cf / cm ² was used. Other than that, t-butyl tin tributoxide was obtained in the same manner as in Example 10-1.

<Comparative Example 10-2>
As a starting material for synthesizing t-butyltin trimethylamide, tin tetrachloride (SnCl ₄ ) having an α-ray emission amount of 0.0005 cf / cm ² was used. However, unlike Example 10-1, α-ray control was not performed to prevent contamination of the α-ray source and to prevent an increase in the amount of α-ray emission. The total number of distillations was three. Other than that, t-butyl tin tributoxide was obtained in the same manner as in Example 10-1.

The α-ray emission amounts of the four types of t-butyl tin tributoxide obtained in Example 10-1, Example 10-2, Comparative Example 10-1 and Comparative Example 10-2 were measured. The results are shown in Table 4 below. Table 4 shows the types of organotin compounds, the amount of α-ray emission of tin (SnCl ₄ ) as a starting material, the implementation or non-implementation of α-ray control during production, the number of distillations during production, and t. -The amount of α-ray emission of butyltin tributoxide is described.

As is clear from Table 4, in Comparative Example 10-1, since t-butyl tin tributoxide was produced from the starting material tin tetrachloride having an α-ray emission amount of 0.5 cf / cm ² , α-ray control was performed during production. However, the amount of α-ray emission of t-butyltin tributoxide, which is the final target substance, was 0.012 cf / cm ² , which was high.
Further, in Comparative Example 10-2, since α-ray control was not performed at the time of production, monoalkyltin oxide was produced from tin tetrachloride as a starting material having an α-ray emission amount of less than 0.0005 cf / cm ² . Regardless, the α-ray emission amount of t-butyltin tributoxide, which is the final target substance, was 0.011 cf / cm ² , which was high.

On the other hand, in Examples 10-1 and 10-2, tin tetrachloride to t-butyl as a starting material having α-ray emission amounts of less than 0.0005 cf / cm ² and 0.002 cf / cm ² , respectively. Since tin tributoxide was produced and α-ray control was performed at the time of production, the α-ray emission amount of t-butyl tin tributoxide, which is the final target substance, was in the range of 0.002 cf / cm ² or less, which was low. ..

[Example of Production of Liquid Composition for Forming EUV Resist Film from Organic Tin Trialkoxide Compound of Formula (9)]
From the four types of t-butyl tin tributoxide obtained in Example 10-1, Example 10-2, Comparative Example 10-1 and Comparative Example 10-2, Test Example 11-1, Test Example 11-2, Four kinds of EUV resist film forming liquid compositions of Comparative Test Example 12-1 and Comparative Test Example 12-2 were produced. Specifically, four types of t-butyl tin tributoxide are weighed so that the tin content of the liquid composition is 0.05 mol / L, and this tin compound is dissolved in 29.8 mL of methyl ethyl ketone. , Test Example 11-1 to Test Example 11-2, Comparative Test Example 12-1, and Comparative Test Example by stirring for 24 hours in a closed space and removing the insoluble solid with a 0.45 μm syringe filter. Four kinds of EUV resist film forming liquid compositions of 12-2 were produced. The types of the organic tin compound used in the above example, the amount of α rays emitted thereof, and the content ratio of tin in the liquid composition are shown in Table 5 below.

[Coating and developing of the EUV resist film forming liquid composition of Test Examples / Comparative Test Examples]
A coating film was formed from the EUV resist film forming liquid composition of the above-mentioned test example and the comparative test example. Specifically, a cleaning solution containing ammonium hydroxide and hydrogen peroxide solution (NH ₄ OH: H ₂ O ₂ : H ₂ by mass ratio) of a Si wafer having a diameter of about 100 mm (4 inches) washed with hydrofluoric acid is contained. It was immersed in O = 1: 1: 12.5) for 10 minutes. Next, in order to improve the adhesion of the EUV resist film forming liquid composition and the resist film formed thereby to the surface of the Si wafer, the Si wafer was placed at a temperature of 120 ° C. for 40 minutes with hexamethyldisilazane (HMDS). After exposure to steam, baking and hydrophobization for dehydration were performed. The EUV resist film forming liquid composition obtained in the above-mentioned test example and the comparative test example was spin-coated on the Si wafer thus pretreated using a spin coater (MS-B100 manufactured by Mikasa). A coating film was formed. The coating film was held at a temperature of 150 ° C. for 5 minutes for baking. The coating amount of the liquid composition at the time of coating was adjusted so that the film thickness after baking was 20 nm. After allowing the baked Si wafer to stand for 120 minutes, a positive simulated resist film was formed using 2.38% by mass of tetramethylammonium hydroxide (TMAH) as a developing solution, and the simulated resist film was subjected to development treatment. Was done.

[Evaluation of simulated resist film]
The line pattern formed by using a high-resolution CD-SEM (manufactured by Hitachi High-Technology Co., Ltd., CS4800) on the developed simulated resist film was evaluated. For a Si wafer having a diameter of about 100 mm, the portion 3 mm from the outer peripheral portion was excluded from the observation area as an edge portion, and the entire wafer surface was scanned. From the captured image, defects of 5 nm or more were recognized as defects, the number of defects was counted, and the number of defects per area (pieces / cm ² ) was calculated. The case where no defect was detected was 0 / cm ² , and the case was judged as “possible”, and the case where the number of defects was 1 / cm ² or more was judged as “impossible”. The number of these defects (pieces / cm ² ) and the determination results are shown in Tables 2, 3 and 5 above.

As is clear from Table 2, Comparative Test Example 1-1, Comparative Test Example 2-1, Comparative Test Example 3-1, Comparative Test Example 4-1 and Comparative Test Example 5-1, Comparative Test Example 6-1 and In Comparative Test Example 7-1, Comparative Test Example 8-1 and Comparative Test Example 9-1, the amount of α-ray emission of the monoalkyl tin oxide used was in the range of 0.013 cf / cm ² to 0.024 cf / cm ² . Since it was higher than 0.01 cph / cm ² , the number of defects of 5 nm or more in the simulated resist film was 1 to 3, and the judgment was "impossible" in all the comparative test examples.
In addition, Comparative Test Example 1-2, Comparative Test Example 2-2, Comparative Test Example 3-2, Comparative Test Example 4-2, Comparative Test Example 5-2, Comparative Test Example 6-2, Comparative Test Example 7-2. In Comparative Test Example 8-2 and Comparative Test Example 9-2, the α-ray emission amount of the monoalkyl tin oxide used was in the range of 0.011 cf / cm ² to 0.017 cf / cm ² , and 0.01 cf / cm. Since it was higher than cm ² , the number of defects of 5 nm or more in the simulated resist film was 1 to 2, and the judgment was "impossible" in all the comparative test examples.
On the other hand, in Test Examples 1 to 9, the α-ray emission amount of the monoalkyl tin oxide used was in the range of 0.0020 cf / cm ² or less, which was lower than 0.01 cf / cm ² , and therefore the simulated resist. The number of defects of 5 nm or more in the film was 0, and the judgment was "OK" in all the test examples.

Further, as is clear from Table 3, in Comparative Test Example 10-1, the α-ray emission amount of the monobutyltin oxide used was 0.013 cf / cm ² , and the tin in the EUV resist film forming liquid composition was The content ratio of was 0.07% by mass. Since the amount of α-ray emission of monobutyltin oxide exceeds 0.01 cph / cm ² , the number of defects of 5 nm or more in the simulated resist film is 1, and the judgment is “impossible”.
Further, in Comparative Test Example 10-3, the α-ray emission amount of the monobutyltin oxide used was 0.011 cf / cm ² , and the content ratio of tin in the EUV resist film forming liquid composition was 25.1 mass by mass. %Met. Since the α-ray emission amount of monobutyltin oxide exceeded 0.01 cph / cm ² and the tin content in the EUV resist film forming liquid composition exceeded 24% by mass, the number of defects of 5 nm or more in the simulated resist film There were more than 3 in Comparative Test Example 10-1, and the judgment was "impossible".

Further, in Comparative Test Example 10-2, the α-ray emission amount of the monobutyltin oxide used was 0.011 cf / cm ² , and the content ratio of tin in the EUV resist film forming liquid composition was 7.98 mass. %Met. Since the amount of α-ray emission of monobutyltin oxide exceeded 0.01 cph / cm ² , the number of defects of 5 nm or more in the simulated resist film was 2, and the judgment was “impossible”.
Further, in Comparative Test Example 11-1, the α-ray emission amount of the monobutyltin oxide used was 0.012 cf / cm ² , and the content ratio of tin in the EUV resist film forming liquid composition was 8.12 mass. %Met. Since the amount of α-ray emission of monobutyltin oxide exceeded 0.01 cph / cm ² , the number of defects of 5 nm or more in the simulated resist film was 2, and the judgment was “impossible”.

On the other hand, in Test Example 10-1 and Test Example 10-2, the α-ray emission amount of the monoalkyl tin oxide used was both in the range of less than 0.0005 cf / cm ² , and the EUV resist film forming liquid was used. The tin content in the composition was 0.05% by mass and 23.1% by mass, respectively. Since the α-ray emission amount of monobutyltin oxide was 0.01 cph / cm ² or less and the tin content in the EUV resist film forming liquid composition was 24% by mass or less, defects of 5 nm or more in the simulated resist film The number was 0, and the judgment was "OK" in all the test examples.

Further, as is clear from Table 5, in Comparative Test Example 12-1 and Comparative Test Example 12-2, the α-ray emission amount of t-butyltin tributoxide used was 0.012 cf / cm ² and 0.011 cf /. At cm ² , the content of tin in the EUV resist film forming liquid composition was 0.6% by mass and 0.9% by mass. Since the amount of α-ray emission of t-butyltin tributoxide exceeded 0.01 cph / cm ² , the number of defects of 5 nm or more in the simulated resist film was 2 and 1, respectively, and the judgment was made in all comparative test examples. It was "impossible".
On the other hand, in Test Example 11-1 and Test Example 11-2, the α-ray emission amount of t-butyltin tributoxide used was less than 0.0005 cf / cm ² and 0.002 cf / cm ² , respectively. , The content ratio of tin in the EUV resist film forming liquid composition was 0.5% by mass and 0.8% by mass. Since the α-ray emission amount of t-butyl tin tributoxide was 0.01 cf / cm ² or less and the tin content in the EUV resist film forming liquid composition was 24% by mass or less, 5 nm in the simulated resist film. The above number of defects was 0, and the judgment was "OK" in all the test examples.

The organotin compound and the liquid composition for forming an EUV resist film of the present invention are used in the field of forming an EUV resist film.

Claims

An organotin compound having an α-ray emission amount of 0.01 cph / cm 2 or less.
The organic tin compound according to claim 1, which is represented by any of the following formulas (1) to (9).

In the above formula (1), R 1 is a hydrocarbon group having 1 to 10 carbon atoms.
In the above formula (2), R 2 is a hydrocarbon group having 1 to 10 carbon atoms, a is 1 or 2, and b to d are integers having the same or different carbon atoms from 1 to 28, respectively. 0 ≦ n ≦ 4.
In the above formula (3), R 2 is a hydrocarbon group having 1 to 10 carbon atoms, p to s are integers having the same or different carbon atoms from 1 to 28, and t is 1 or more and 4 or less. .. Y has an anion species as a counterion.
In the above formula (4), R 3 is a hydrocarbon group having 1 to 10 carbon atoms.
In the above formula (5), R 4 is a hydrocarbon group having 1 to 10 carbon atoms.
In the above formula (6), R 5 is a hydrocarbon group having 1 to 10 carbon atoms, and R 6 is a hydrocarbon group having 1 to 5 carbon atoms.
In the above formula (7), R 7 is a hydrocarbon group having 1 to 10 carbon atoms.
In the above formula (8), R 8 is a hydrocarbon group having 1 to 10 carbon atoms.
In the above formula (9), R 9 is a hydrocarbon group having 1 to 10 carbon atoms.
The EUV resist film forming liquid composition using the organic tin compound according to claim 1 or 2, when the EUV resist film forming liquid composition is 100% by mass, the tin content ratio is 0.05% by mass. A liquid composition for forming an EUV resist film in an amount of% or more and 24% by mass or less.
A method for forming an EUV resist film having an α-ray emission amount of 0.01 cph / cm 2 or less by using the liquid composition for forming an EUV resist film according to claim 3.
(a) A step of synthesizing tin tetrachloride from metallic tin having an α-ray emission amount of 0.01 cph / cm 2 or less,
(b) A method for producing an organic tin compound, which comprises a step of synthesizing a monoalkyl tin oxide or an alkyl tin trialkoxide from the tin tetrachloride.
Distillation for removing impurities from the compound is performed a plurality of times in all the steps from the step (a) to the step (b), and the equipment used in all the steps from the step (a) to the step (b). The production of an organic tin compound, which is characterized by reducing the amount of α-ray emission of the organic tin compound to 0.01 cf / cm 2 or less by performing α-ray control for shielding α-rays from the environment. Method.
The organic according to claim 5, wherein the multiple distillations are carried out by measuring the amount of α-ray emission of the compound or impurity distillate produced in each step and until the amount of α-ray emission becomes 0.01 cf / cm 2 or less. Method for producing a tin compound.