Membrane manufacturing method

Abstract

To provide a technology of depositing a high quality MgF2 film with high film deposition efficiency.SOLUTION: A method for depositing a film includes the steps of: supplying a Mg source to a film deposition chamber; and supplying a fluorinating agent and an oxidizing agent to the film deposition chamber so that the fluorinating agent and the oxidizing agent coexist.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to, for example, MgF2 films. [Background technology]

[0002] The refractive index of MgF2 film is small (n=1.38). MgF2 film has excellent light transmittance over a wide range (from deep ultraviolet to mid-infrared). Therefore, MgF2 is used in optical elements. For example, it is used as an anti-reflection film.

[0003] The following methods are known for forming MgF2 films. Bulk MgF2 is melted by an electron beam (or resistive heating), and the evaporated MgF2 is deposited on the substrate. The following problems have been pointed out with this film formation method: The uniformity of the MgF2 film is poor. In particular, when the area is large, the uniformity across the entire MgF2 film is poor. It is difficult to form an MgF2 film on the surface of an element with a complex structure. Splashing (boiling) is likely to occur during film formation. As a result, defects are likely to occur in the film.

[0004] A film formation method using atomic layer deposition (ALD) has been proposed. ALD can improve some of the problems associated with the melting method. The following Non-Patent Documents 1, 2, and 3 propose MgF2 film formation techniques using ALD.

[0005] The technology disclosed in Non-Patent Document 1 is as follows: The Mg source is bis(ethylcyclopentadienyl)magnesium ((EtCp)2Mg). The fluorinating agent is HF. The MgF2 film was formed by ALD. The deposition rate of the MgF2 film at this time was approximately 0.04 nm / cycle (deposition temperature: 150°C). The deposition rate was slow. Highly corrosive HF is used. Materials such as glass are susceptible to HF. Therefore, there are limitations on the substrate.

[0006] The technology disclosed in Non-Patent Document 2 is as follows (see FIG. 3). The Mg source is Mg(thd)2. The Mg(thd)2 was introduced into the film formation chamber (step 1). An inert gas (N2) was introduced into the film formation chamber, which was then evacuated (step 2). O3 was introduced into the film formation chamber (step 3). An inert gas (N2) was introduced into the film formation chamber, which was then evacuated (step 4). HfacH (Hexafluoroacetylacetone: fluorinating agent) was introduced into the film formation chamber (step 5). An inert gas (N2) was introduced into the film formation chamber, which was then evacuated (step 6). O3 was introduced into the film formation chamber (step 7). An inert gas (N2) was introduced into the film formation chamber, which was then evacuated (step 8). The steps 1 to 8 constitute one cycle. The thickness of the MgF2 film formed in this one cycle is approximately 0.038 nm. Therefore, to form an MgF2 film with a thickness of approximately 100 nm, approximately 2,700 repetitions are required. In this manufacturing method, steps 3 and 4 were essential. That is, in order to form the MgF2 film, it was necessary to first form the MgO film. In this manufacturing method, steps 7 and 8 were essential. That is, steps 7 and 8 were necessary to repeatedly deposit another monolayer MgF2 film on top of the monolayer MgF2 film. If steps 7 and 8 were skipped (step 1 was performed after step 6), MgF2 films could not be formed in the second and subsequent cycles.

[0007] The technology disclosed in Non-Patent Document 3 is as follows: The Mg source is Mg(thd)2, and the fluorinating agent is TiF4 or TaF4. The technique of Non-Patent Document 3 has a simpler film formation process than the technique of Non-Patent Document 2. However, TiF4 and TaF4 are solids with low vapor pressure, and require high-temperature heating of the raw materials, containers, and piping, making them difficult to handle. The deposition rate is approximately 0.16 nm / cycle (250°C) to 0.07 nm / cycle (400°C). The deposition efficiency is poor. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Younghee Lee, Huaxing Sun, Matthias J. Young, and Steven M. George, Chem. Mater. 2016,28,7,pp2022-2032 [Non-patent document 2] Matti Putkonen, Adriana Szeghalmi, Eckhard Pippel, and Mato Knea, J. Mater. Chem. 2011,21,pp14461-14465 [Non-patent document 3] Tero Pilvi, Timo Hatanpaa, Esa Puukilainen, Kai Arstila, Martin BischOff, Ute Kaiser, Norbert Kaiser, Markku Leskela, and Mikko Ritala, J. Mater. Chem. 2007,17,pp5077-5083 Summary of the Invention [Problem to be solved by the invention]

[0009] When MgF2 is used as an anti-reflection film, the film needs to be about 100 nm thick, for example. The techniques disclosed in Non-Patent Documents 1, 2 and 3 have too low film formation efficiency.

[0010] A first problem to be solved by the present invention is to provide a film formation technique with high film formation efficiency. The second problem to be solved by the present invention is to provide a technology that utilizes a fluorine raw material that is less corrosive and an Mg raw material that is easy to handle. [Means for solving the problem]

[0011] The present inventors have intensively pursued research to solve the above problems. The inventors investigated the reasons for the slow film formation rate in the technology described in Non-Patent Document 2. As a result, the inventors concluded that the slow film formation rate was mainly due to the following two factors. First, in the technology described in Non-Patent Document 2, the MgF2 film is formed by fluorinating the MgO film, so the MgO film must first be formed. Therefore, the MgO film formation is rate-limiting, and the MgF2 formation rate cannot be expected to exceed the MgO film formation rate. There is also the issue of conversion efficiency when converting the MgO film to an MgF2 film. Second, the technology described in Non-Patent Document 2 requires not only the introduction of a fluoride source but also two additional introductions of an oxidizing source. This doubles the number of manufacturing steps. Therefore, we attempted to combine the two steps of MgO formation and MgO to MgF2 conversion into a single process. That is, instead of applying an oxidizing agent and a fluoriding agent sequentially (with a time interval) to the Mg source, we tried applying the oxidizing agent and the fluoriding agent simultaneously. The oxidizing agent and the fluorinating agent were simultaneously supplied to the film formation chamber. As a result, the film formation efficiency was surprisingly high. Moreover, the carbon content in the resulting MgF2 film was extremely low. We succeeded in producing a low-impurity, high-quality MgF2 film.

[0012] The present invention was achieved based on the above findings.

[0013] The present invention is a method for forming a magnesium fluoride (for example, MgFx (x is 1.8 to 2.5; for convenience, x may be represented as 2 (MgF2))) film on a substrate by ALD.

[0014] A method for forming a magnesium fluoride film is proposed in which an Mg source deposited on a substrate is exposed to a fluorinating agent and an oxidizing agent substantially simultaneously to form a high-quality thin magnesium fluoride layer.

[0015] The present invention proposes a method comprising a step A in which a Mg source is supplied to a film formation chamber, and a step B in which a fluorinating agent and an oxidizing agent are simultaneously supplied to the film formation chamber so that the fluorinating agent and the oxidizing agent coexist in the film formation chamber. The present invention proposes a method for forming a magnesium fluoride film, which includes a step A in which a Mg source is supplied to a film formation chamber, and a step B in which a fluorinating agent and an oxidizing agent are simultaneously supplied to the film formation chamber so that the fluorinating agent and the oxidizing agent coexist in the film formation chamber. The present invention proposes a method for forming an MgFx (x is 1.8 to 2.5) film, which includes a step A in which a Mg source is supplied to a film formation chamber, and a step B in which a fluorinating agent and an oxidizing agent are simultaneously supplied to the film formation chamber so that the fluorinating agent and the oxidizing agent coexist in the film formation chamber.

[0016] The present invention provides The film forming method (film formation method), Preferably, steps C and D are present between step A and step B, The step C is a step of removing the Mg source supplied in the step A that has not been deposited on the substrate from the film formation chamber, The step D is a step of removing the remaining fluorinating agent and oxidizing agent that did not contribute to the conversion of the Mg source deposited on the substrate into the magnesium fluoride. Suggest a method.

[0017] The present invention provides a method for forming the film (film formation method), Preferably, the process is repeated in the order of step A → step C → step B → step D → step A → step C → step B → step D ...... Suggest a method.

[0018] The present invention proposes a method, wherein the Mg source is preferably liquid at temperatures below 80°C.

[0019] The present invention is directed to a method for producing a magnesium source, the method comprising the steps of: (R1Cp)(R2Cp)Mg (where R1 and R2 are hydrogen atoms or C n H 2n+1 (n is 0 to 5). Cp is a cyclopentadienyl group. R1 and R2 may be the same or different.

[0020] The present invention proposes a method, wherein the Mg source is preferably (EtCp)2Mg.

[0021] The present invention proposes a method in which the fluorinating agent preferably has a vapor pressure of 1 torr to 100 torr at a raw material temperature of 0 to 100°C.

[0022] The present invention proposes a method, wherein the fluorinating agent is preferably a compound with a low C content.

[0023] The present invention proposes a method wherein said fluorinating agent is preferably a fluorocarbon.

[0024] The present invention proposes a method in which the fluorinating agent is preferably a compound in which some H in a hydrocarbon (here, the hydrocarbon may have an element other than C and H (e.g., O)) is substituted with F.

[0025] The present invention proposes a method, wherein said fluorinating agent is preferably HfacH.

[0026] The present invention proposes a method, wherein said oxidizing agent preferably comprises O3.

[0027] The present invention provides a method for forming the film (film formation method), The method preferably comprises: the exposure amount of the Mg source to the substrate is 0.01 to 10 torr·sec; the exposure dose of the fluorinating agent is 0.01 to 20 torr·seconds; The exposure amount of the oxidizing agent is 0.1 to 10 torr·seconds. Suggest a method.

[0028] The present invention proposes a method for forming the film (film deposition method) in which the substrate is preferably heated to 200° C. or higher.

[0029] The present invention preferably proposes a method in which the film formation rate is 0.1 nm / cycle or more.

[0030] The present invention preferably proposes a method in which the film formation rate is 0.15 nm / cycle or more.

[0031] The present invention preferably proposes a method in which the amount of C in the film is 1 atomic % or less. [Effects of the Invention]

[0032] The process was simple. The deposition rate was high. Magnesium fluoride films were obtained efficiently. High quality magnesium fluoride films with low carbon content were obtained. High degree of freedom in raw material selection. High degree of freedom in substrate selection. [Brief explanation of the drawings]

[0033] [Figure 1] Flowchart of film formation according to the present invention [Figure 2] Schematic diagram of the film formation device [Figure 3] Conventional film formation flow chart DETAILED DESCRIPTION OF THE INVENTION

[0034] Embodiments of the present invention are described below. The present invention is a film forming method. It is a method for forming a magnesium fluoride film. The magnesium fluoride is, for example, MgFx (x is 1.8 to 2.5). MgFx is sometimes represented by MgF2. The method is as follows: A Mg source (also called Mg raw material) deposited on a substrate is exposed to a fluorinating agent (also called fluorinating source) and an oxidizing agent (also called oxidizing source) simultaneously. The simultaneous exposure may be with a slight time lag. Of course, this does not include a time lag in which the treatment with the fluorinating agent begins after the treatment with the oxidizing agent has ended.

[0035] The method may be as follows. The method includes a step (also referred to as step A) of supplying an Mg source (also referred to as Mg raw material) to a film formation chamber. For example, a carrier gas (e.g., N2) is supplied to the Mg source-containing solution. The Mg source is supplied (transported) from the solution to the film formation chamber by bubbling. The solution is preferably heated. The method includes a step (also referred to as step B) of supplying a fluorinating agent (also referred to as a fluorination source) and an oxidizing agent (also referred to as an oxidation source) to a film formation chamber. This step (step B) allows the fluorinating agent and the oxidizing agent to coexist in the film formation chamber. Step B is performed after step A. For example, a carrier gas (e.g., N2) is supplied to the fluorinating agent-containing solution. The fluorinating agent is supplied (transported) to the film formation chamber by bubbling. The solution is preferably cooled. If the step B is employed, the Mg source deposited on the substrate by the step A is exposed to the fluorinating agent and the oxidizing agent simultaneously. The fluorinating agent and the oxidizing agent may be supplied to the film formation chamber simultaneously or at different times. Even when the fluorinating agent and the oxidizing agent are supplied to the film formation chamber at different times, the fluorinating agent and the oxidizing agent coexist in the film formation chamber. Therefore, the Mg source deposited on the substrate in step A is exposed to the fluorinating agent and the oxidizing agent simultaneously. The fluorinating agent and the oxidizing agent may be sent to the film formation chamber via the same route or via different routes.

[0036] The method includes a step (also referred to as step A or step A') of supplying an Mg source to the film formation chamber and depositing the Mg source on the substrate. The method preferably includes a step (also referred to as step C) of removing the Mg source that has not been deposited on the substrate from the film formation chamber. The method preferably includes a step (also referred to as step B or step B') of supplying the fluorinating agent and the oxidizing agent to the film formation chamber after the removal step (step C). The method preferably includes step D. Step D is carried out after step B (B') and before step A (A'). Step D is a step of removing the remaining fluorinating agent and oxidizing agent that did not contribute to converting the Mg source deposited on the substrate into the MgF2.

[0037] The method is preferably repeated in the order of step A (A') → step C → step B (B') → step D → step A (A') → step C → step B (B') → step D → step A (A') → step C → step B (B') ... The number of repetitions is determined depending on the desired thickness of the MgF2 film.

[0038] In the above method, the exposure amount of the Mg source to the substrate was preferably 0.01 to 10 torr·seconds. More preferably, it was 0.05 torr·seconds or more. Even more preferably, it was 0.1 torr·seconds or more. Even more preferably, it was 5 torr·seconds or less. Even more preferably, it was 1 torr·second or less. A high Mg source exposure amount means that a large amount of the Mg source is used. If it is too high, there is a lot of waste. The processing time is also long. Productivity is reduced. A low Mg source exposure amount means that the amount of the Mg source deposited on the substrate is small. A low deposition amount of the Mg source means a slow film formation rate. Productivity is poor. From these perspectives, the above ranges were preferable. The exposure amount of the fluorinating agent to the substrate (the deposited Mg source) was preferably 0.01 to 20 torr·seconds. More preferably, it was 0.1 torr·second or more. Even more preferably, it was 0.5 torr·second or more. Even more preferably, it was 10 torr·second or less. Even more preferably, it was 5 torr·second or less. A high exposure amount of the fluorinating agent means that a large amount of the fluorinating agent is used. If it is too much, there is a lot of waste. The processing time is also long. Productivity is reduced. A low exposure amount of the fluorinating agent means that the Mg is difficult to fluorinate. High-quality MgF2 is difficult to obtain. The film formation rate is reduced. Productivity is poor. From these points of view, the above ranges were preferable. The exposure amount of the oxidizing agent to the substrate (the deposited Mg source) was preferably 0.1 to 10 torr·seconds. More preferably, it was 0.4 torr·second or more. Even more preferably, it was 5 torr·second or less. Even more preferably, it was 2 torr·second or less. A high exposure amount to the oxidizing agent means that a large amount of the oxidizing agent is used. If it is too much, there is a lot of waste. The processing time is also long. Productivity is reduced. A low exposure amount to the oxidizing agent means that it is difficult to obtain high-quality MgF2. The film formation rate is reduced. Productivity is poor. From these points of view, the above ranges were preferable. The substrate was preferably heated to 200°C or higher. More preferably, it was 250°C or higher. Even more preferably, it was 300°C or higher. Particularly preferably, it was 350°C or higher. Preferably, it was 700°C or lower. Even more preferably, it was 600°C or lower. Particularly preferably, it was 550°C or lower. If the temperature was too low, oxidation was insufficient. The film formation rate decreased. Impurities were likely to remain in the film. Film quality deteriorated. If the temperature was too high, the raw materials decomposed. Impurities were likely to remain in the film. Film quality deteriorated. From these viewpoints, the above ranges were preferable.

[0039] The Mg source is preferably liquid at 80° C. or less. Preferably, (R1Cp)(R2Cp)Mg (R1 and R2 are hydrogen atoms or C n H 2n+1 (n is 0 to 5.) Cp is a cyclopentadienyl group. R1 and R2 may be the same or different. Preferably, R1 and R2 are the same.] was a compound represented by the formula: Particularly preferred was (EtCp)2Mg.

[0040] The fluorinating agent was preferably a compound having a vapor pressure of 1 torr to 100 torr at a raw material temperature of 0 to 100°C. A compound having a C-F bond was preferred. A fluorocarbon was preferred. A hydrocarbon (here, hydrocarbon may have an element other than C and H (e.g., O)) compound in which some hydrogen atoms have been substituted with fluorine atoms was preferred. HfacH was particularly preferred. These compounds (fluorinating agents) were less corrosive than HF. There were fewer restrictions on the substrate.

[0041] The oxidizing agent was preferably O3, or it could be an O3-containing gas, or it could be plasma oxygen (plasma-treated oxygen).

[0042] The film formation rate was preferably 0.1 nm / cycle or more, and more preferably 0.15 nm / cycle or more.

[0043] The amount of C in the film was preferably 1 atomic % or less.

[0044] The method for forming the MgF2 film by ALD (atomic layer deposition) will now be described in more detail.

[0045] Fig. 1 is a flow chart showing the film formation process according to the present invention, and Fig. 2 is a schematic diagram of a film formation apparatus.

[0046] The four steps (step A → step C → step B → step D) are shown in Figure 1. The Mg source (e.g., (EtCp)2Mg) is placed in a source container 1. The source container 1 is heated (e.g., to 70°C). A carrier gas (e.g., N2) is supplied (e.g., at 50 sccm) into the source container 1. The (EtCp)2Mg is supplied from the source container 1 to the film formation chamber 2 by bubbling. Of course, a method other than bubbling may be used. A substrate (glass, silicon wafer, etc.) 3 is placed in the film formation chamber (reaction chamber) 2. The substrate 3 is heated (e.g., to 300°C or higher) by a heater 4. The (EtCp)2Mg supplied to the film formation chamber 2 is deposited on the substrate 3. The amount (exposure amount) of the substrate 3 to the (EtCp)2Mg is 0.05 to 10 torr·seconds (Step A). After the step A, an inert gas (e.g., N2) was supplied into the film formation chamber 2. Then, the film formation chamber 2 was evacuated to a vacuum. As a result, unreacted gases, by-product gases, etc. remaining in the film formation chamber 2 were exhausted (removed) from the exhaust port 5 (step C). After step C, the fluorinating agent (e.g., HfacH) and the oxidizing agent (e.g., O3) were simultaneously supplied to the film formation chamber 2. The HfacH was placed in a source container 6. The source container 6 was cooled (e.g., 0°C). A carrier gas (e.g., N2) was supplied (e.g., 100 sccm) into the source container 6. The HfacH was supplied from the source container 6 to the film formation chamber 2 by bubbling. Of course, a method other than bubbling may also be used. The O3 was supplied to the film formation chamber 2 from an ozone generator 7. Of course, the O3 may also be supplied from a cylinder containing O3 components. The (EtCp)2Mg deposited on the substrate 3 was exposed to the HfacH for 0.1 to 20 torr·seconds. The amount (exposure amount) of the (EtCp)2Mg deposited on the substrate 3 exposed to the O3 was 0.1 to 10 torr·seconds (step B). After the step B, an inert gas (e.g., N2) was supplied into the film formation chamber 2. Then, the film formation chamber 2 was evacuated to a vacuum. As a result, unreacted gases, by-product gases, etc. remaining in the film formation chamber 2 were exhausted (removed) from the exhaust port 5 (step D). "Process A → Process C → Process B → Process D" is one cycle. This cycle was repeated as needed. When two cycles are repeated twice, it is "Process A → Process C → Process B → Process D → Process A → Process C → Process B → Process D". It is repeated n times (n is a natural number) as needed.

[0047] Specific examples are given below. However, the present invention is not limited to the following examples. Various modifications and applications are also included in the present invention as long as the features of the present invention are not significantly impaired. [Example]

[0048] The substrate 3 was heated to 400° C. The "step A → step C → step B → step D" was repeated 150 times. The film formation rate was 0.323 nm / cycle. A 48.48 nm thick MgF2 film was formed on the substrate 3. The MgF2 film formed by the ALD method had excellent uniformity. The film was analyzed by XPS measurement, and the results were as follows: Mg: 27.9 atomic %, F: 68.8 atomic %, O: 2.5 atomic %, C: 0.8 atomic % (close to the detection limit of XPS). The refractive index of the film was 1.38. [Example]

[0049] The substrate 3 was heated to 300°C. The "step A → step C → step B → step D" was repeated 94 times. The film formation rate was 0.137 nm / cycle. A 12.92 nm thick MgF2 film was formed on the substrate 3. The MgF2 film formed by the ALD method had excellent uniformity. The film was analyzed by XPS measurement, and the results were as follows: Mg: 28.3 atomic %, F: 64.6 atomic %, O: 6.4 atomic %, C: 0.7 atomic % (close to the detection limit of XPS). The refractive index of the film was 1.38. [Example]

[0050] The substrate 3 was heated to 350° C. The “step A → step C → step B → step D” was repeated 150 times. The film formation rate was 0.168 nm / cycle. A 25.13 nm thick MgF2 film was formed on the substrate 3. The MgF2 film formed by the ALD method had excellent uniformity. The film was analyzed by XPS measurement, and the results were as follows: Mg: 28.8 atomic %, F: 67.1 atomic %, O: 3.6 atomic %, C: 0.5 atomic % (close to the detection limit of XPS). The refractive index of the film was 1.38. [Example]

[0051] The substrate 3 was heated to 500° C. The “step A → step C → step B → step D” was repeated 120 times. The film formation rate was 0.452 nm / cycle. A 54.28 nm thick MgF2 film was formed on the substrate 3. The MgF2 film formed by the ALD method had excellent uniformity. The film was analyzed by XPS measurement, and the results were as follows: Mg: 28.0 atomic %, F: 68.9 atomic %, O: 2.0 atomic %, C: 1.1 atomic % (close to the detection limit of XPS). The refractive index of the film was 1.38.

[0052] The substrate 3 was heated to 400°C. The technology disclosed in Non-Patent Document 2 (see Figure 3) was employed. Mg(thd)2 was introduced into the film formation chamber 2 (Step 1). Inert gas (N2) was introduced into the film formation chamber 2 and the chamber was evacuated (Step 2). O3 was introduced into the film formation chamber 2 (Step 3). Inert gas (N2) was introduced into the film formation chamber 2 and the chamber was evacuated (Step 4). HfacH was introduced into the film formation chamber 2 (Step 5). Inert gas (N2) was introduced into the film formation chamber 2 and the chamber was evacuated (Step 6). O3 was introduced into the film formation chamber 2 (Step 7). Inert gas (N2) was introduced into the film formation chamber 2 and the chamber was evacuated (Step 8). "Steps 1 to 8" were repeated 300 times. The film formation rate was 0.028 nm / cycle. An 8.52 nm MgF2 film was formed on the substrate 3. The film was analyzed by XPS measurement, and the results were as follows: Mg: 24.1 atomic %, F: 41.8 atomic %, O: 2.0 atomic %, C: 32.1 atomic % Comparative Example 2

[0053] The procedure was the same as in Example 2, except that HfacH was not introduced into the film formation chamber 2. That is, an MgO film was formed by ALD. The film formation rate was 0.190 nm / cycle. The film was analyzed by XPS measurement, and the results were as follows: Mg: 42.6 atomic %, C: 5.2 atomic %, O: 52.2 atomic % In other words, it was found that a high amount of carbon remains in the MgO film formed by ALD using O3 as the oxidizing agent. The refractive index of the film was 1.65.

[0054] The procedure was the same as in Example 1, except that O 3 was not introduced into the film-forming chamber 2. Almost no film was formed.

[0055] A comparison between the Examples and Comparative Example 1 reveals the following: The film formation rate per cycle of the present invention is more than 10 times higher than that of existing technology (mainly referring to the technology disclosed in Non-Patent Document 2). The film formation rate per unit time is more than 20 times higher. Moreover, the carbon content in the thin film is dramatically reduced. A comparison of the Example with Comparative Examples 2 and 3 reveals the following: In order to form an MgF2 film, a fluorinating agent and an oxidizing agent were necessary in addition to the Mg source. A comparison between the Example and Comparative Example 1 reveals the following: In order to efficiently form a high-quality MgF2 film, it was necessary for the Mg source deposited on the substrate to be exposed to the fluorinating agent and the oxidizing agent almost simultaneously.

Claims

1. A film formation method, comprising: The Mg source deposited on the substrate is exposed to a fluorinating agent and an oxidizing agent simultaneously. method.

2. A film formation method, comprising: The method comprises: supplying an Mg source to a film formation chamber; a step of supplying a fluorinating agent and an oxidizing agent so that the fluorinating agent and the oxidizing agent coexist in a film formation chamber; A method comprising the steps of:

3. a step of supplying an Mg source to a film formation chamber and depositing the Mg source on a substrate; a removing step of removing the Mg source that has not been deposited on the substrate from the film formation chamber; a step of supplying the fluorinating agent and the oxidizing agent to the film formation chamber after the removing step.

3. The method of claim 1 or claim 2, comprising:

4. a removing step is performed after the step of supplying the fluorinating agent and the oxidizing agent and before the step of supplying the Mg source to the film formation chamber; The removal step is a step of removing the remaining fluorinating agent and oxidizing agent that did not contribute to the conversion of the Mg source deposited on the substrate into magnesium fluoride. The method of claim 3.

5. The substrate temperature is over 200°C. The method according to any one of claims 1 to 4.

6. ALD is a film formation method. The method according to any one of claims 1 to 5.

7. The Mg source is liquid at 80°C or less The method according to any one of claims 1 to 6.

8. The Mg source is (R １ Cp) (R ２ Cp)Mg[R １ , R ２ is a hydrogen atom or C ｎ H ２ｎ+１ (n is 0 to 5). Cp is a cyclopentadienyl group. R １ and R ２ may be the same or different. The method according to any one of claims 1 to 7.

9. The Mg source is (EtCp) ２ Mg The method according to any one of claims 1 to 8.

10. The fluorinating agent has a vapor pressure of (1 to 100) x 133.32 Pa when the raw material temperature is 0 to 100°C. The method according to any one of claims 1 to 9.

11. The fluorinating agent is a compound having a C—F bond. The method according to any one of claims 1 to 10.

12. The fluorinating agent is HfacH The method according to any one of claims 1 to 11.

13. The oxidizing agent is O ３ have The method according to any one of claims 1 to 12.

14. The exposure amount of the Mg source to the substrate is (0.05 to 10) × 133.32 Pa sec; the exposure amount of the fluorinating agent is (0.1 to 20) × 133.32 Pa sec; The exposure amount of the oxidizing agent is (0.1 to 10) × 133.32 Pa·sec The method according to any one of claims 1 to 13.

15. The film formation rate is 0.1 nm / cycle or more. The method according to any one of claims 1 to 14.

16. The amount of C in the film is 1 atomic % or less The method according to any one of claims 1 to 15.

17. This is a method for forming an MgFx (x is 1.8 to 2.5) film. The method according to any one of claims 1 to 16.

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