Conductive layer selective protective film material and film formation method

Abstract

To provide a conductive layer selective protective film material that enables the formation of a film having sufficient protective film properties and high temperature resistance.SOLUTION: A conductive layer selective protective film material comprises 8-phenyl-1-octanethiol or 2-phenyl-1,3-propanedithiol.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a material for a selective protective film for a conductive layer and a method for forming the film, and more particularly to a material for a selective protective film for a conductive layer of a specific sulfur-based compound and a method for forming the material into a film. [Background technology]

[0002] Lithography is a technique used in semiconductor manufacturing to transfer circuit patterns onto a substrate using extreme ultraviolet light or an argon fluoride laser. In lithography, materials such as cobalt and copper are used as the conductive layer of the substrate, and a selective film material that selectively adsorbs to metals such as cobalt and copper is preferably used as the protective film.

[0003] Patent Document 1 discloses a film formation method that can selectively form a uniform self-assembled monolayer in a desired region.

[0004] Patent Document 2 discloses a selective film deposition method that allows a film of an organic substance to be selectively deposited on a surface region containing a metal element rather than on a surface region containing a non-metallic inorganic material on a substrate using a simple operation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-137435 [Patent Document 2] Republished WO2022 / 163825 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when metal wiring is formed using only lithography, misalignment of the film formation occurs, increasing the risk of short circuits in the wiring. Therefore, there is a need for a new material for selectively protecting conductive layers to reduce this risk. [Means for solving the problem]

[0007] The present inventors have found that the use of a specific sulfur-based compound results in a film having sufficient protective properties and high temperature resistance, and have completed the present invention. [Effects of the Invention]

[0008] The present invention provides a material for a conductive layer selective protective film that enables the formation of a film having sufficient protective film properties and high temperature resistance, and also provides a film formation method using the material. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Conductive layer selective protective film material) The conductive layer selective protective film material of the present invention includes sulfur-based compounds, specifically 8-phenyl-1-octanethiol or 2-phenyl-1,3-propanedithiol.

[0010] (Method of producing 8-phenyl-1-octanethiol) The method for producing 8-phenyl-1-octanethiol, which is a material for a conductive layer selective protective film of the present invention, includes the following steps (a) to (e): (a) reaction, (b) extraction, (c) washing, (d) drying, and (e) filtration and evaporation.

[0011] <Step (a): Reaction> To obtain 8-phenyl-1-octanethiol, 8-PhoctylBr is reacted with NaSH·nH2O.

[0012] The ratio of the amounts of 8-PhoctylBr and NaSH·nH2O charged is preferably 1:0.1 to 1:10, more preferably 1:1 to 1:4.

[0013] Examples of the solvent include ethanol and isopropanol.

[0014] The reaction temperature may be room temperature, specifically 15 to 40°C, and preferably 20 to 30°C.

[0015] The reaction time is 10 hours or more, more preferably 20 hours or more, so that the reaction can proceed sufficiently.

[0016] <Step (b): Extraction> In order to extract 8-phenyl-1-octanethiol from the resulting reaction solution, the reaction solution is placed in a separatory funnel, water is added, and an organic solvent is further added for extraction.

[0017] The organic solvent includes diethyl ether, ethyl acetate, and methyl ethyl ketone.

[0018] In order to increase the extraction rate of 8-phenyl-1-octanethiol, the extraction operation is repeated, preferably two or more times, more preferably three or more times.

[0019] <Step (c): Washing> Washing is carried out to remove impurities such as unreacted materials, and it is preferable to add an inorganic salt and a non-aqueous solvent, more preferably sodium chloride and diethyl ether.

[0020] <Step (d): Drying> To dry the resulting cleaning solution, a moisture absorbent such as magnesium sulfate or sodium sulfate is used.

[0021] <Step (e): Filtration and Distillation> The resulting dried product is filtered through pleated filter paper to remove the moisture absorbent contained therein, and the solvent is then removed using an evaporator.

[0022] By carrying out the above steps (a) to (e), 8-phenyl-1-octanethiol to be used as a material for a conductive layer selective protective film can be obtained.

[0023] (Method of producing 2-phenyl-1,3-propanedithiol) The method for producing 2-phenyl-1,3-propanedithiol, which is a material for a conductive layer selective protective film of the present invention, is synthesized in the following order of steps 1 and 2: (Step 1) Synthesis of 2-phenyl-1,3-propanediol dimethyl sulfonate, (Step 2) Synthesis of 2-phenyl-1,3-propanedithiol.

[0024] (Step 1) The synthesis of 2-phenyl-1,3-propanediol dimethyl sulfonate includes the following steps (1-a) to (1-e): (1-a) reaction, (1-b) extraction, (1-c) washing, (1-d) drying, and (1-e) filtration and evaporation.

[0025] <(1-a):Reaction> To obtain the intermediate 2-phenyl-1,3-propanediol dimethyl sulfonate, a base is added to 2-phenyl-1,3-propanediol and the mixture is cooled. After adding a mesylating agent dropwise to the solution, the mixture is heated to room temperature and reacted at room temperature. To terminate the reaction, a reaction terminator is added to the reaction mixture.

[0026] Examples of the base include triethylamine, diethylamine, and diisopropylethylamine.

[0027] An example of the mesylating agent is mesyl chloride.

[0028] The reaction terminator includes water and the like.

[0029] The reaction time is 2 hours or more, more preferably 3 hours or more, so that the reaction can proceed sufficiently.

[0030] <(1-b):Extract> To extract 2-phenyl-1,3-propanediol dimethyl sulfonate from the resulting reaction mixture, the reaction mixture is placed in a separatory funnel and extracted with an organic solvent, such as toluene or diethyl ether. To increase the extraction rate of 2-phenyl-1,3-propanediol dimethyl sulfonate, the extraction procedure is repeated, preferably two or more times, more preferably three or more times.

[0031] <(1-c): Cleaning> Washing is carried out to remove impurities such as unreacted materials, and a washing agent is used, such as a saturated aqueous sodium chloride solution, a saturated aqueous sodium sulfate solution, or a saturated aqueous potassium bromide solution.

[0032] <(1-d):Drying> To dry the resulting cleaning solution, a moisture absorbent such as magnesium sulfate or sodium sulfate is used.

[0033] <(1-e): Filtration and Distillation> The dried product is filtered through a fluted filter paper, and the solvent is removed using an evaporator to obtain 2-phenyl-1,3-propanediol dimethyl sulfonate.

[0034] By the above step 1, 2-phenyl-1,3-propanediol dimethyl sulfonate, which is an intermediate for 2-phenyl-1,3-propanedithiol used as a material for the conductive layer selective protective film, can be obtained.

[0035] (Step 2) The synthesis of 2-phenyl-1,3-propanedithiol includes the following steps (2-a) to (2-l): (2-a) reaction, (2-b) extraction, (2-c) washing, (2-d) drying, (2-e) filtration and evaporation, (2-f) purification, (2-g) reaction, (2-h) extraction, (2-i) washing, (2-j) drying, (2-k) filtration and evaporation, and (2-l) purification.

[0036] <(2-a):Reaction> 2-Phenyl-1,3-propanediol dimethyl sulfonate obtained in step (1), an organic solvent, and a thiolation agent are added to 2-phenyl-1,3-propanedithiol, and the mixture is heated to reflux in an oil bath. An aqueous solution of NaOH is added to the reaction mixture, and the mixture is further heated to reflux in an oil bath. After allowing the reaction mixture to cool, a reaction terminator is added.

[0037] Examples of the organic solvent include isopropyl alcohol and ethanol.

[0038] The thiolation agent includes, for example, thiourea.

[0039] The reaction terminator may be, for example, an HCl solution.

[0040] <(2-b):Extract> The reaction mixture is placed in a separatory funnel and extracted with an organic solvent, such as toluene or diethyl ether. The extraction is preferably repeated two or more times, more preferably three or more times.

[0041] <(2-c): Cleaning> Washing is carried out to remove impurities such as unreacted materials, and a washing agent is used, such as a saturated aqueous sodium chloride solution, a saturated aqueous sodium sulfate solution, or a saturated aqueous potassium bromide solution.

[0042] <(2-d): Drying> To dry the resulting cleaning solution, a moisture absorbent such as magnesium sulfate or sodium sulfate is used.

[0043] <(2-e): Filtration and Distillation> The resulting dried product is filtered through a pleated filter paper, and the solvent is removed using an evaporator to obtain a concentrate.

[0044] <(2-f): Purification> The concentrate is purified by column chromatography packed with silica gel to obtain a mixture of 2-phenyl-1,3-propanedithiol and 4-phenyl-1,2-dithiolane.

[0045] <(2-g):Reaction> The mixture is dissolved in a mixed solvent, cooled, and then a reducing agent is added. The temperature of the resulting reaction solution is maintained and stirred, and after the reaction is complete, a reaction quencher is added. The mixed solvent can be a THF / MeOH solution. The reducing agent can be NaBH4.

[0046] <(2-h):Extract> The reaction mixture is placed in a separatory funnel and extracted with an organic solvent, such as toluene or diethyl ether. The extraction is preferably repeated two or more times, more preferably three or more times.

[0047] <(2-i): Cleaning> Washing is carried out to remove impurities such as unreacted materials, and a washing agent is used, such as a saturated aqueous sodium chloride solution, a saturated aqueous sodium sulfate solution, or a saturated aqueous potassium bromide solution.

[0048] <(2-j):Drying> To dry the resulting cleaning solution, a moisture absorbent such as magnesium sulfate or sodium sulfate is used.

[0049] <(2-k): Filtration and distillation> The resulting dried product is filtered through a pleated filter paper, and the toluene is removed using an evaporator to obtain a concentrate.

[0050] <(2-l):Refinement> The concentrate is purified by column chromatography packed with silica gel to obtain 2-phenyl-1,3-propanedithiol.

[0051] In the above step 2, 2-phenyl-1,3-propanediol used as a material for the conductive layer selective protective film can be obtained from 2-phenyl-1,3-propanediol dimethyl sulfonate.

[0052] (Film forming method) The film formation method using the conductive layer selective protective film material of the present invention includes the following steps (A) to (C): (A) placing a substrate on a stage in a vacuum chamber and heating the stage, (B) injecting a mixed gas into the vacuum chamber to remove an oxide film on the substrate surface, and (C) lowering the stage temperature in the vacuum chamber and injecting a conductive layer selective protective film material, a sulfur-based compound consisting of 8-phenyl-1-octanethiol or 2-phenyl-1,3-propanedithiol, to be adsorbed onto the conductive layer on the substrate.

[0053] <Process (A)> The vacuum device is not particularly limited, but is preferably a vacuum device having a stage for placing a substrate. It is also desirable that the vacuum device has a load lock chamber. Examples of commercially available vacuum devices include those manufactured by Spread Co., Ltd.

[0054] The heating temperature of the stage is preferably 200 to 300°C, more preferably 250 to 270°C, from the viewpoint of the strength of the reducing power and the reduction of damage to the substrate.

[0055] The substrate is composed of a semiconductor base substrate such as a silicon wafer, and a conductive layer and an insulating layer on the top surface of the base substrate.

[0056] Examples of the conductive layer include metal wiring, metal film, wiring film, and conductive film.

[0057] Examples of metal elements used in the conductive layer include Cu, Co, Mo, Fe, W, Ru, Ni, Pt, Al, Ta, Ti, and Hf. The metal elements may be one type or multiple types. The metal elements may exist as metals or as compounds containing the metal elements. Compounds containing metal elements may be any compounds that are chemically bonded to the metal elements, such as metal oxides, metal nitrides, and alloys. Metals and metal oxides are particularly preferred. Furthermore, Cu, Co, and Ru are preferred as metal elements.

[0058] Materials used for the insulating layer include silicon compounds such as silicon oxide, silicon nitride, and silicon carbide.

[0059] The conductive layer and insulating layer on the upper surface may be a single layer or multiple layers, in which case the conductive layer is selected from the metal elements described above and the insulating layer is selected from the materials described above.

[0060] <Process (B)> The mixed gas is a mixture of a reducing gas and an inert gas from the viewpoint of controlling the reduction rate. Examples of the reducing gas include hydrogen, carbon monoxide, and ammonia. Among these, hydrogen gas is particularly preferable. Examples of the inert gas include helium, nitrogen, and argon.

[0061] The mixing ratio of the reducing gas to the inert gas is controlled by a mass flow controller and is, for example, 1:1 to 1:10, more preferably 1:2 to 1:8, and particularly preferably 1:3 to 1:5.

[0062] The pressure of the mixed gas injected into the vacuum device is preferably 1000 to 10000 Pa, more preferably 3000 to 8000 Pa, and even more preferably 6000 to 7000 Pa.

[0063] The mixed gas is injected into the vacuum device for 10 to 15 minutes.

[0064] <Process (C)> The stage temperature in the vacuum chamber is lowered to a temperature suitable for forming the conductive layer selective protective film material, preferably to 150° C. or less, more preferably to 120° C. or less.

[0065] From the viewpoint of uniform supply, the conductive layer selective protective film material is preferably mixed with an inert gas before injection.

[0066] The mixing ratio of the conductive layer selective protective film material and the inert gas is controlled by a mass flow controller and is 1:1 to 1:30, and more preferably 1:5 to 1:10.

[0067] The injection pressure into the vacuum device is preferably 100 to 1000 Pa, more preferably 200 to 800 Pa, and even more preferably 300 to 600 Pa.

[0068] The time for injecting the mixed gas into the vacuum device is preferably, for example, 5 minutes.

[0069] The metal surface may be subjected to an oxidation treatment between steps (B) and (C).

[0070] Examples that more specifically disclose embodiments of the present invention are given below, but the present invention is not limited to these examples.

[0071] [Production Example 1] (Synthesis of 8-phenyl-1-octanethiol) A 300 ml four-neck flask with nitrogen purging was charged with 13.08 g of NaSH·nHO (Fujifilm Wako Pure Chemical Industries, Ltd.) and 56.70 g of ethanol (Kanto Chemical Co., Ltd.). 14.93 g of 8-PhoctylBr (BLPpharm Co., Ltd.) was added to the charged solution and allowed to react for 20 hours with stirring at room temperature. 98.9 g of HO was added to dilute the reaction solution. The reaction solution was extracted with 98.33 g of diethyl ether using a 500 ml separatory funnel. This extraction procedure was repeated three times. The extract was washed with NaCl and diethyl ether. 3.06 g of MgSO4 (Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the washings and dried. The dried product was filtered through a fluted filter paper, and the solvent was removed using an evaporator to obtain 8-phenyl-1-octanethiol (yield 11 g, purity 96.3%).

[0072] [Production Example 2] (Synthesis of 2-phenyl-1,3-propanedithiol) Step (1): Synthesis of 2-phenyl-1,3-propanediol dimethyl sulfonate A 1-L four-neck flask was charged with nitrogen and charged with 22.02 g of 2-phenyl-1,3-propanediol (Tokyo Chemical Industry Co., Ltd.), 289.02 g of toluene (Kanto Chemical Industry Co., Ltd.), and 33.10 g of triethylamine (Fujifilm Wako Pure Chemical Industries, Ltd.). The flask was cooled to 0°C in an ice bath with stirring. While maintaining the temperature of the charged solution between 0 and 15°C, 39.01 g of mesyl chloride (Tokyo Chemical Industry Co., Ltd.) was added dropwise over 1 hour. The mixture was then warmed to room temperature and reacted at room temperature for 3 hours. After adding 220.29 g of HO as a reaction terminator, the solution was extracted with 110.29 g of toluene (Kanto Chemical Industry Co., Ltd.) using a 1-L separatory funnel. This extraction procedure was repeated three times. The extract was washed with saturated aqueous sodium chloride, then 28.51 g of MgSO4 (Fujifilm Wako Pure Chemical Industries, Ltd.) was added and the mixture was dried. The dried product was filtered through a fluted filter paper, and the solvent was removed using an evaporator to obtain 2-phenyl-1,3-propanediol dimethyl sulfonate (yield: 43.86 g, purity: 95.3%).

[0073] Step (2): Synthesis of 2-phenyl-1,3-propanedithiol A 1-L four-neck flask containing nitrogen was charged with 41.0 g of 2-phenyl-1,3-propanediol dimethylsulfonate (obtained in step (1)), 429.53 g of isopropyl alcohol (Tokyo Chemical Industry Co., Ltd.), and 25.0 g of thiourea (Fujifilm Wako Pure Chemical Industries, Ltd.). The mixture was heated to reflux for 21 hours with stirring in a 100°C oil bath. 100.94 g of 10 wt% aqueous NaOH was added to the reaction mixture, which was then heated to reflux for 10 hours with stirring in a 100°C oil bath. After completion of the reaction, the reaction mixture was allowed to cool to room temperature, and 103.33 g of 1M aqueous HCl solution was added as a reaction terminator. The solution was extracted with 96.71 g of toluene (Kanto Chemical Co., Ltd.) using a 1-L separatory funnel. This extraction procedure was repeated three times. The extract was washed with 218.64 g of saturated aqueous sodium chloride, then 51.83 g of MgSO4 (Fujifilm Wako Pure Chemical Industries, Ltd.) was added, and the mixture was dried. The dried product was filtered through a fluted filter paper, and the solvent was removed using an evaporator to obtain a concentrate. The concentrate was purified by column chromatography using silica gel to obtain a mixture of 2-phenyl-1,3-propanedithiol and 4-phenyl-1,2-dithiolane (yield: 14.70 g). The resulting mixture (14.70 g) was dissolved in 191.53 g of THF / MeOH (v / v = 1:1) in a 1 L four-neck flask purged with N2. After cooling to 0-5 °C, 3.37 g of NaBH4 (Tokyo Chemical Industry Co., Ltd.) was added. The resulting reaction solution was maintained at 0-5 °C and stirred for 2.5 h. After completion of the reaction, aqueous HCl (136.17 g, 1 M) was added as a reaction terminator. The solution was extracted with 87.90 g of toluene using a 1 L separatory funnel. This extraction procedure was repeated three times. The extract was washed with 171.94 g of saturated aqueous sodium chloride, and then 10.98 g of MgSO (Fujifilm Wako Pure Chemical Industries, Ltd.) was added and dried. The dried product was filtered through a pleated filter paper, and the toluene was removed using an evaporator to obtain a concentrate. The concentrate was purified by column chromatography packed with silica gel to obtain 2-phenyl-1,3-propanedithiol (yield 15.14 g, purity 97.2%).

[0074] (Preparation of substrate) [Example 1] A substrate with a silicon base, a Co conductive layer, and an SiO insulating layer was placed on a stage in a vacuum chamber, and the stage was heated to 270°C. A mixed gas of 100 sccm of hydrogen gas and 400 sccm of argon gas was injected into the chamber at a pressure of 7000 Pa for 10 minutes to remove the oxide film on the substrate surface. The stage temperature was then lowered to 120°C, and the compound obtained in Preparation Example 1 was injected at a carrier gas flow rate of 20 sccm together with 150 sccm of argon gas at a pressure of 400 Pa for 5 minutes, allowing it to adsorb onto the conductive layer on the substrate, thereby producing a substrate.

[0075] [Example 2] A substrate was produced in the same manner as in Example 1, except that the compound obtained in Production Example 1 was changed to the compound obtained in Production Example 2.

[0076] [Comparative Example 1] A substrate was produced in the same manner as in Example 1, except that the compound obtained in Production Example 1 was changed to commercially available 2-phenyl-2-ethanethiol (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0077] (Evaluation of film formation on substrate) Film-forming properties were evaluated for the substrates produced in Examples 1 and 2 and Comparative Example 1. The film-forming properties were evaluated based on the protective film properties and heat resistance of the substrates.

[0078] <Protective film properties> After preparing the substrate using the same procedure as in Example 1, the stage was heated to 150°C without removing the substrate from the vacuum chamber. The vacuum chamber was maintained at 30 Pa with argon gas, and a cycle of 1 second of trimethylaluminum supply, 60 seconds of argon purging, 2 seconds of water supply, and 85 seconds of argon purging was repeated 30 times. The substrate was then removed from the vacuum chamber, and the contact angle between the water droplet and the substrate surface was measured using a contact angle meter (CA-S150 manufactured by Kyowa Interface Science). The contact angle reduction rate was calculated from the measured contact angle and the contact angle of the substrate prepared in Example 1, and the protective film properties were evaluated. Protective film property (reduction rate)=[contact angle of substrate supplied with trimethylaluminum−contact angle of substrate in Example 1] / [contact angle of substrate in Example 1]×100 The above method is a method for evaluating the protective film properties on the substrate of Example 1. In Example 2 and Comparative Example 1, the substrates were replaced with corresponding ones, and the protective film properties were evaluated from the contact angles of those substrates.

[0079] <Heat resistance> After the stage of the vacuum chamber was heated to 350°C, a substrate prepared using the same procedure as in Example 1 was placed on the stage, and annealing treatment was carried out for 15 minutes while maintaining the pressure inside the vacuum chamber at 0.01 Pa or less. The contact angle retention rate was calculated from the contact angle of the substrate after the annealing treatment and the contact angle of the substrate prepared in Example 1, and heat resistance was evaluated. Heat resistance (retention rate) = [contact angle after annealing] ÷ [contact angle of substrate in Example 1] × 100 The above method is a method for evaluating the heat resistance of the substrate of Example 1. In Example 2 and Comparative Example 1, the substrates were replaced with corresponding ones, and the heat resistance was evaluated from the contact angle of those substrates.

[0080] The results of the evaluation of the film-forming properties of the substrate are shown in Table 1.

[0081] [Table 1]

Claims

1. A material for selectively protecting a conductive layer, comprising 8-phenyl-1-octanethiol.

2. A conductive layer selective protective film material comprising 2-phenyl-1,3-propanedithiol.

3. (A) placing a substrate on a stage in a vacuum device and heating the stage; (B) injecting a mixed gas into a vacuum chamber to remove an oxide film on the surface of the substrate; (C) A film forming method, comprising lowering the stage temperature in a vacuum apparatus, injecting a sulfur-based compound consisting of 8-phenyl-1-octanethiol or 2-phenyl-1,3-propanedithiol, and allowing it to be adsorbed onto a conductive layer on a substrate.

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