Novel compounds, titanium oxide film-forming materials, and titanium oxide film-forming methods.

Abstract

When a titanium oxide film obtained by film formation at a relatively low temperature (for example, 150 °C or lower) has physical properties of a high refractive index, a Ti organic compound that is a liquid at 25 °C (1 atm) is provided. 【Solution means】(R 1 , R 2 -EDA)Ti(NR 3 R 4 )2 (EDA is N 1 , N 2 -dialkyl-ethylenediamine. R 1 , R 2 , R 3 , R4 is a hydrocarbon group.) A compound represented by.

Description

[Technical Field]

[0001] This invention relates to a method for forming a titanium oxide film (for example, a method for forming a titanium oxide film with a high refractive index (TiOx: x is 1 to 2, especially about 2) by forming the film at a relatively low temperature such as 150°C or below), a Ti organic compound (precursor) suitable for the said method, and a novel compound. [Background technology]

[0002] Titanium oxide films have a high refractive index. Therefore, titanium oxide films are used in the field of optical devices and optical components.

[0003] Patent document 1 (JP 2024-160355 A) discloses an anti-reflective coating (AR coating). The AR coating has a laminated structure of a low refractive index layer and a high refractive index layer. The AR coating is formed by ion-assisted evaporation. The low refractive index layer is made of SiO2. The refractive index of the SiO2 coating is approximately 1.43 to 1.47. The high refractive index layer is made of ZrO2, SnO2, Nb2O5, Ta2O5, TiO2, Y2O3, Al2O3, etc. The numerical value of the refractive index of the high refractive index layer is not disclosed. From the expression "high refractive index layer," we can only imagine that the refractive index of the high refractive index layer is greater than that of the SiO2 coating. Therefore, the refractive index of the high refractive index layer may be approximately 1.5. It may not be the refractive index (2.3) targeted by the present invention. There is no connection between the aforementioned patent document and the present invention.

[0004] Patent document 2 (JP 2024-96328 A) discloses optical glass with a refractive index of 1.81 to 2.15. The glass contains SiO2 and B2O3 as components. In addition to the above components, it also contains high refractive index components that increase the refractive index of the glass. The high refractive index components disclosed are TiO2, Ta2O5, WO3, Nb2O5, ZrO2, and Ln2O3. The aforementioned patent document discloses TiO2. The aforementioned patent document does not disclose the TiO2 film itself. The aforementioned patent document does not disclose the refractive index of the TiO2 film. There is no connection between the aforementioned patent document and the present invention.

[0005] Patent document 3 (JP 2023-154291) discloses an anti-reflective coating (AR coating). The AR coating is a laminate of a high refractive index layer and a low refractive index layer. The AR coating is formed by sputtering, IAD (Ion Assist Deposition), ion plating, IBS (Ion Beam Sputter), cluster deposition, CVD (Chemical Vapor Deposition), or ALD (Atomic Layer Deposition). Examples of materials for the high refractive index layer are given as TiO2, Nb2O5, ZrO2, Ta2O5, HfO2, La2Ti2O7 (LaTiO3), Si3N4, etc. The refractive index of the high refractive index layer is only stated as 1.8 or higher. There is no specific disclosure of the refractive index of the TiO2 coating. There is no connection between the aforementioned patent document and the present invention.

[0006] Patent Document 4 (Patent No. 7347203) discloses an anti-reflective film composed of at least 10 layers. The refractive index of the high refractive index layers (2nd, 4th, 6th, 8th, and 10th layers) of the anti-reflective film is 2.0 to 2.3. The high refractive index layers are a Ta2O5 layer (refractive index 2.16), a ZrO2 layer (refractive index 2.05), a layer formed from a mixture of ZrTiO4 and ZrO2 (refractive index 2.08), a LaTiO3 layer (refractive index 2.1), a layer formed from a mixture of ZrO2 and TiO2 (refractive index 2.15), a layer formed from a mixture of Ta2O5 and ZrO2 (refractive index 2.22), a layer formed from a mixture of Ta2O5 and TiO2 (refractive index 2.24), a Nb2O5 layer (refractive index 2.3), or a TiO2 layer (refractive index 2.3). The aforementioned patent document discloses film formation using a vacuum deposition method performed at a relatively high temperature (300°C). However, the aforementioned patent document does not disclose the materials used for TiO2 film formation. It is not an exaggeration to say that there is no connection between the aforementioned patent document and the present invention.

[0007] Patent document 5 (Patent No. 6976968) discloses an ophthalmic lens having an anti-reflective coating. The anti-reflective coating has five or more layers. At least one of the five or more layers is a low refractive index (refractive index of 1.6 or less) film (LI film), at least one is a high refractive index (refractive index of 2.2 or more, preferably 2.3 or more, more preferably 2.35 or more, even more preferably 2.37 or more) film (VHI film), and at least one is a film with a refractive index of 1.6 to 2.2 (HI film). Examples of materials for the HI film include ZrO2, Al2O3, Ta2O5, Pr2O3, PrTiO3, La2O3, Y2O3, etc. Examples of materials for the VHI film include Nb2O5, TiO2, etc. The anti-reflective coating is formed by vapor deposition. However, the aforementioned patent document does not disclose the material used to form the TiO2 film. It would not be an exaggeration to say that there is no connection between the aforementioned patent document and the present invention.

[0008] Patent documents 1 to 5 were patent documents in the field of optics. The performance of optical devices in these patent documents is greatly affected by the refractive index. TiO2 has a high dielectric constant. Therefore, it is used in electronic devices. The performance of electronic devices is not affected by the refractive index. Consequently, the following Non-Patent Documents 1-5 and Patent Document 6 do not mention the refractive index at all. This is only natural. For this reason, it is not an exaggeration to say that there is no connection between Non-Patent Documents 1-5 and Patent Document 6 and the present invention. I am confident that Non-Patent Documents 1-5 and Patent Document 6 do not affect the patentability of the present invention.

[0009] Non-patent document 1 [Appl.Phys.Lett.90,262901(2007)] discloses a non-volatile memory having an HfO2 / TiO2 stacked structure.

[0010] Non-patent document 2 [Arch.Metall.Mater.69(2024),2,463-466] discloses an SRC (Self-rectifying memory cell) having a stacked structure of HfO2 / TiO2.

[0011] Non-patent document 3 [Thin Solid Films, Volume 628, 30 April 2017, Pages 142-147] discloses a technique for forming TiO2 films using PEALD with TiCl4 (raw material).

[0012] Non-patent document 4 [Chem.Mater.2020,32,4,1393-1407] discloses a technique for forming TiO2 films by ALD using Ti(OiPr)4 (raw material).

[0013] Non-patent document 5 [Chem.Mater.2012,24,17,3420-3424] discloses a technique for forming TiO2 films by ALD using Ti(NMe2)2(OiPr)2 (raw material).

[0014] Patent document 6 [Korean Patent 10-2428276] is (N 1 ,N 2 The compound -di-tert-butylpropane-1,2-diamino)-bis(dimetylamino)Ti is disclosed. The document discloses techniques for depositing Hf and Zr films at high temperatures (deposition temperature). However, it does not disclose techniques for depositing Ti films. Moreover, as mentioned above, the refractive index is not specified. [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] Japanese Patent Publication No. 2024-160355 [Patent Document 2] Japanese Patent Publication No. 2024-96328 [Patent Document 3] Japanese Patent Publication No. 2023-154291 [Patent Document 4] Patent No. 7347203 [Patent Document 5] Patent No. 6976968 [Patent Document 6] Korean Patent No. 10-2428276 [Non-patent literature]

[0016] [Non-Patent Document 1] Appl.Phys.Lett.90,262901(2007) [Non-Patent Document 2] Arch.Metall.Mater.69(2024),2,463-466 [Non-Patent Document 3] Thin Solid Films,Volume628,30 April 2017,Page142-147 [Non-Patent Document 4] Chem.Mater.2020,32,4,1393-1407 [Non-Patent Document 5] Chem.Mater.2012,24,17,3420-3424 [Overview of the project] [Problems that the invention aims to solve]

[0017] The aforementioned patent and non-patent documents do not disclose the deposition of titanium oxide films at relatively low temperatures, such as below 150°C. Therefore, it is not possible to imagine what the refractive index value of a titanium oxide film deposited at low temperatures would be. In the field of thin-film deposition, deposition temperature is a crucial requirement. Typical deposition temperatures range from 250°C to 550°C. Higher deposition temperatures lead to faster deposition rates. However, higher deposition temperatures also cause decomposition of the deposition material, leading to the inclusion of impurities in the deposited film. At high deposition temperatures, for example, Ti organic compounds (deposition material) undergo dissociation at weak chemical bonding points (e.g., the bonding points between Ti and the organic group), and these organic group components are incorporated into the film during deposition. The decomposition of the deposition material allows chemical reactions to proceed continuously, without self-regulation of the reaction (deposition). Furthermore, high deposition temperatures limit the types of substrates (also called substrates or base materials; hereinafter referred to as substrates) that can be used to deposit metal-containing films. High temperatures make the substrate susceptible to thermal damage. Lower deposition temperatures minimize these disadvantages. Lower deposition temperatures offer greater flexibility in the substrate on which the film is deposited. There are few constraints on the substrate. Resin substrates and plastic substrates can be used. However, even when forming films at relatively low temperatures, it cannot be said that impurities will not be introduced. In other words, although the risk of decomposition of Ti organic compounds is low, it cannot be said that there is no risk of undecomposed Ti organic compounds being incorporated into the film. However, this risk (the risk of undecomposed Ti organic compounds being incorporated into the film) cannot be said to be absent when forming films at high temperatures. If that is the case, then a lower film formation temperature would be preferable.

[0018] For these reasons, there has been a demand for film deposition materials and technologies that can deposit high-quality (high refractive index) films at relatively low temperatures. In particular, there has been a demand for film deposition materials and technologies that can deposit titanium oxide films with a high refractive index at relatively low temperatures. There has also been a demand for the development of metal-organic compounds (liquid at room temperature) as raw materials to be used for film deposition. The problem that this invention aims to solve is to provide a titanium oxide film obtained when formed at a relatively low temperature (for example, 150°C or below) that has high refractive index properties and is a Ti organic compound (raw material) that is liquid at 25°C (at 1 atmosphere). [Means for solving the problem]

[0019] The present invention A novel compound, namely, (R 1 ,R 2 -EDA)Ti(NR 3 R 4 )2 (EDA is N 1 ,N 2 -dialkyl-ethylenediamine. R 1 ,R 2 ,R 3 ,R 4 is a hydrocarbon group.) The compound represented by is proposed.

[0020] The present invention proposes a novel compound which is the above novel compound and is liquid at 25 °C (1 atm).

[0021] The present invention proposes a novel compound which is the above novel compound and the hydrocarbon group has a carbon number of, for example, 1 to 4 hydrocarbon groups.

[0022] The present invention proposes a novel compound which is the above novel compound and the hydrocarbon group is an alkyl group.

[0023] The present invention proposes a novel compound which is the above novel compound and the alkyl group is any one selected from the group of Me, Et, Pr, Bu.

[0024] The present invention proposes a novel compound which is the above novel compound and at least one of the R 1 ,R 2 is tBu.

[0025] The present invention proposes a novel compound which is the above novel compound and the R 1 ,R 2 is tBu.

[0026] The present invention proposes a novel compound which is the above novel compound and the R 3 ,R 4 is any one selected from the group of Me, Et, Pr.

[0027] The present invention relates to the novel compound, and the R 3 ,R 4 We propose a novel compound in which Me is the dominant compound.

[0028] The present invention relates to the novel compound, and the R 1 ,R 2 tBu, the R 3 ,R 4 We propose a novel compound in which Me is the dominant compound.

[0029] The present invention A material used for forming titanium oxide films, The material is the novel compound. We propose a thin-film deposition material.

[0030] The present invention A method for forming a titanium oxide film, The novel compound is supplied into the film deposition chamber. A titanium oxide film is formed on the substrate in the aforementioned film deposition chamber. We propose a film deposition method.

[0031] The present invention proposes a film deposition method wherein the film deposition temperature is, for example, 150°C or lower.

[0032] The present invention proposes a film formation method in which a weak oxidizing agent is used for film formation.

[0033] The present invention proposes a film formation method in which H2O (oxidizing agent) is used for film formation.

[0034] The present invention proposes a film formation method in which O2 (oxidizing agent) is used for film formation.

[0035] The present invention proposes a film deposition method wherein ALD is used for the film deposition.

[0036] The present invention proposes a film deposition method wherein CVD is used for the film deposition.

[0037] The present invention proposes a film formation method wherein the amount of impurities (C,N) in the formed titanium oxide film is 1 atm% or less.

[0038] The present invention proposes a film formation method wherein the amount of impurities (C,N) in the formed titanium oxide film is less than 1 atm%.

[0039] The present invention proposes a film formation method wherein the refractive index of the formed titanium oxide film is 2.3 or higher.

[0040] The present invention proposes a film formation method wherein the refractive index of the formed titanium oxide film is 2.35 or higher. [Effects of the Invention]

[0041] According to the present invention, a high-quality titanium oxide film can be obtained even at a low film formation temperature. The refractive index of the deposited titanium oxide film was, for example, 2.3 or higher. The impurities (C,N) in the deposited titanium oxide film were 1 atm% or less. [Brief explanation of the drawing]

[0042] [Figure 1] (EDA-tBu2)Ti(NMe2)2 TG diagram [Figure 2] (iPrO)2Ti(NMe2)2 TG diagram [Figure 3] Schematic diagram of film deposition apparatus [Figure 4] GPC diagram when (EDA-tBu2)Ti(NMe2)2 is used [Figure 5] GPC diagram when (iPrO)2Ti(NMe2)2 is used [Modes for carrying out the invention]

[0043] The following detailed description provides only preferred exemplary embodiments and is not intended to limit the scope, applicability, or configuration of the invention. Rather, it provides to those skilled in the art an explanation for carrying out / enabling preferred exemplary embodiments of the invention. Various modifications can be made to the function and arrangement of the elements without departing from the spirit and scope of the invention as set forth in the appended claims.

[0044] The first invention is a novel compound. The compound is (R 1 ,R 2 -EDA)Ti(NR 3 R 4 The compound is represented by )2. The EDA is N 1 ,N 2 -dialkyl-ethylenediamine. The above R 1 ,R 2 ,R 3 ,R 4 R is a hydrocarbon group. 1 ,R 2 ,R 3 ,R 4 They can be the same or different.

[0045] The aforementioned compound (Ti organic compound) is sometimes described as a complex. Because it is suitably used in CVD and ALD, it is also sometimes described as a precursor. Regardless of the notation, it should be considered to refer to the same substance.

[0046] The structural formula of the aforementioned compound is as follows. In the above general formula, R 1 ,R 2 ga tBu de R 3 ,R 4 The structural formula of the compound containing Me is as follows: The structural formula of the compound in Patent Document 6 is as follows: JPEG2026136027000003.jpg2234 JPEG2026136027000004.jpg2073 At first glance, the above structural formula of the compound of the present invention and the above structural formula of the compound of Patent Document 6 may appear to be similar. However, Patent Document 6 contains a group (R) bonded to Ti. 1 ,R 2 - There is no disclosure of EDA. There is also no mention suggesting it. Furthermore, Patent Document 6 does not mention the refractive index. It does not mention the refractive index of the deposited film. Therefore, it is completely unknown whether a film with a high refractive index (for example, a refractive index of 2.3 or higher) can be obtained when a film is deposited using the compound described in Patent Document 6. In particular, it is completely unknown whether a film with a high refractive index (for example, a refractive index of 2.3 or higher) can be obtained when the film is deposited at a relatively low temperature (for example, 100-150°C). Furthermore, Patent Document 6 does not disclose the purity (amount of impurities) of the film. There is also no description that would suggest that the amount of impurities (C,N) in the film is 1 atm% or less. In other words, the usefulness of the novel compound of the present invention cannot be seen from the compound in Patent Document 6. In this regard, I am confident that the patentability of the compound of the present invention will not be hindered by Patent Document 6.

[0047] The compound was preferably a liquid at 25°C (1 atm). The hydrocarbon group preferably had 1 to 4 carbon atoms. The hydrocarbon group was preferably an alkyl group. The alkyl group was preferably one selected from the group consisting of a methyl group (Me), an ethyl group (Et), a propyl group (Pr), and a butyl group (Bu). The alkyl group having three or more carbon atoms may be a linear alkyl group, but preferably it was a branched alkyl group. Examples include iPr (iso-propyl group: -CH(CH3)2), iBu (iso-butyl group), sBu (sec-butyl group), and tBu (tert-butyl group: -C(CH3)3). The butyl group was preferably tBu. Preferably, the R 1,R 2 At least one of them was a branched alkyl group. More preferably, the R 1 ,R 2 However, both were alkyl groups having branched chains. More preferably, tBu. Particularly preferably, the R 1 ,R 2 However, both were tBu. Preferably, the R 3 ,R 4 was one of the groups Me, Et, and Pr. More preferably, the R 3 ,R 4 That was Me. Particularly preferred, the R 1 ,R 2 tBu, the R 3 ,R 4 That was Me.

[0048] The second aspect of the present invention is a material (compound) used for forming a titanium oxide film. The novel compound {(R 1 ,R 2 -EDA)Ti(NR 3 R 4 )2} is used.

[0049] The aforementioned compound alone cannot yield an oxide film. Therefore, an oxidizing agent is used for film formation. Preferably, the oxidizing agent is one with low oxidizing ability. For example, H2O was used. O3 is undesirable, but O2 can be used.

[0050] The compound was preferably a liquid at 25°C (1 atm). The hydrocarbon group preferably had 1 to 4 carbon atoms. The hydrocarbon group was preferably an alkyl group. The alkyl group was preferably one selected from the group consisting of a methyl group (Me), an ethyl group (Et), a propyl group (Pr), and a butyl group (Bu). The alkyl group having three or more carbon atoms may be a linear alkyl group, but preferably it was a branched alkyl group. Examples include iPr (iso-propyl group: -CH(CH3)2), iBu (iso-butyl group), sBu (sec-butyl group), and tBu (tert-butyl group: -C(CH3)3). The butyl group was preferably tBu. Preferably, the R 1 ,R 2 At least one of them was a branched alkyl group. More preferably, the R 1 ,R 2 However, both were alkyl groups having branched chains. More preferably, tBu. Particularly preferably, the R 1 ,R 2 However, both were tBu. Preferably, the R 3 ,R 4 was one of the groups Me, Et, and Pr. More preferably, the R 3 ,R 4 That was Me. Particularly preferred, the R 1 ,R 2 tBu, the R 3 ,R 4 That was Me.

[0051] The third aspect of the present invention is a method for forming a titanium oxide film. In the above method, the compound {(R 1 ,R 2 -EDA)Ti(NR 3 R 4 )2} is supplied into the deposition chamber. An oxidizing agent is supplied into the deposition chamber. A titanium oxide film is deposited on the substrate in the deposition chamber.

[0052] The compound was preferably a liquid at 25°C (1 atm). The hydrocarbon group preferably had 1 to 4 carbon atoms. The hydrocarbon group was preferably an alkyl group. The alkyl group was preferably any one selected from the group consisting of a methyl group (Me), an ethyl group (Et), a propyl group (Pr), and a butyl group (Bu). The alkyl group having 3 or more carbon atoms may be a linear alkyl group, but is preferably an alkyl group having a branched chain. For example, iPr (iso-propyl group: -CH(CH3)2), iBu (iso-butyl group), sBu (sec-butyl group), tBu (tert-butyl group: -C(CH3)3) can be mentioned. The butyl group was preferably tBu. Preferably, at least one of the R 1 , R 2 is an alkyl group having a branched chain. More preferably, the R 1 , R 2 are both alkyl groups having a branched chain. Even more preferably, it was tBu. Particularly preferably, the R 1 , R 2 are both tBu. Preferably, the R 3 , R 4 is any one selected from the group consisting of Me, Et, and Pr. More preferably, the R 3 , R 4 is Me. Particularly preferably, the R 1 , R 2 is tBu, and the R 3 , R 4 is Me.

[0053] The film-forming temperature was preferably 250°C or lower. More preferably, it was 200°C or lower. Particularly preferably, it was 150°C or lower. Preferably, it was 70°C or higher. Even more preferably, it was 80°C or higher. For example, it was 100°C or higher.

[0054] For film formation, in addition to the compound, an oxidizing agent is used. The oxidizing agent was preferably an oxidizing agent having a weak oxidizing power. The oxidizing agent was preferably H2O. Using O2 is also conceivable.

[0055] ALD is used for film deposition. CVD can also be used. The aforementioned ALD is not limited to ALD in the narrow sense, but also includes ALD in the broad sense and similar ALDs. Similarly, the aforementioned CVD is not limited to CVD in the narrow sense, but also includes CVD in the broad sense and similar CVDs. For example, this includes pulsed CVD, laser CVD, cyclic CVD (CCVD), metal-organic CVD (MOCVD), plasma-enhanced CVD (PECVD), high-density PECVD, photon-assisted CVD, plasma-photon-assisted CVD (PPECVD), thermochemical vapor deposition, low-temperature chemical vapor deposition, chemically assisted vapor deposition, hot filament chemical vapor deposition, CVD of liquid polymer precursors, deposition from supercritical fluids and low-energy CVD (LECVD), plasma-enhanced ALD (PEALD), etc. In addition, CVD and ALDs employing radiation (X-rays, electron beams, electromagnetic waves, or light) are also included.

[0056] A carrier gas (e.g., N2) is supplied to the precursor, and the precursor is transported into the film deposition chamber by bubbling.

[0057] The refractive index of the titanium oxide film obtained by the above film formation method was 2.3 or higher. In particular, it was 2.35 or higher. The impurities (C,N) in the titanium oxide film obtained by the above film formation method were 1 atm% or less. In particular, they were less than 1 atm%.

[0058] In general, in the field of metal-containing film deposition, it is preferable for the precursor to be liquid rather than solid. Liquid precursors can be transported more uniformly than solid precursors during the metal-containing film deposition process. A carrier gas is bubbled into the metal-containing film precursor under suitable process conditions. This bubbling is an effective means of increasing the contact time between the gas and the liquid. These actions aim to achieve a gas flow saturated with the vaporized precursor. Achieving a saturated carrier gas flow maximizes precursor transport and is advantageous for the operation of the metal-containing film deposition process.

[0059] According to the present invention, the problems that the present invention aims to solve have been solved. Specifically, a titanium oxide film with impurities (C,N) of 1 atm% or less (especially less than 1 atm%) in the film could be formed at a film formation temperature of 150°C or lower. A titanium oxide film with a high refractive index of 2.3 (especially 2.35) or higher could be formed.

[0060] The present invention will be described in more detail below. The following description is merely a preferred exemplary embodiment and does not limit the present invention. Various modifications are also possible, without departing from the spirit and scope of the present invention as defined in the claims.

[0061] [Example 1] [Compound 1:(EDA-tBu2)Ti(NMe2)2] The synthesis was carried out under a nitrogen atmosphere. 15.1 g of Cl2Ti(NMe2)2 and 200 ml of hexane were added to the container. The container was cooled to -50°C to -78°C. 9.34 g of nBuLi / nHexane (15 wt%) solution was slowly added dropwise to the container. 13.8 g of EDA-tBu2 was also slowly added dropwise. The container remained cooled to -50°C to -78°C. The mixture was stirred inside the container. After this, the cooling of the container was stopped. The temperature of the container gradually returned to room temperature. During this time, stirring was taking place inside the container. After stirring at room temperature, the container was heated to 75°C. Heating and stirring were carried out for 3 hours. After heating and stirring, the heating of the container was stopped. The temperature of the container gradually returned to room temperature. After stirring at room temperature, the resulting reaction mixture was filtered off. The solvent in the resulting reaction mixture solution was removed by reduced-pressure distillation. The resulting crude product was purified by distillation. A red liquid was obtained.

[0062] The compound of the aforementioned red liquid was confirmed to be (EDA-tBu2)Ti(NMe2)2 by NMR spectrometer (BRUKER AVANCEIII400).

[0063] The above compound was confirmed by a TG device (TG-DTA8122 / S manufactured by RIGAKU) to have a weight loss rate of 99.4% and a T50 (temperature at a weight loss rate of 50%) of 195.4°C (see Figure 1). It was found that the above compound has good volatility and good thermal stability. Therefore, it can be said that it is a suitable precursor for forming a Ti-containing film.

[0064] If carried out according to the synthesis method of the above compound 1, a person skilled in the art can synthesize (R 1 ,R 2 -EDA)Ti(NR 3 R 4 )2 other than the above compound 1 of the present invention.

[0065] [Compound 2: (iPrO)2Ti(NMe2)2] The synthesis was carried out under a nitrogen atmosphere. 22.4 g of Ti(NMe2)4 and 200 ml of hexane were put into a container. The container was cooled to -50°C to -78°C. 12.0 g of isopropanol was slowly dropped into the container. Stirring of the mixture was carried out in the container. After that, cooling of the container was stopped. The temperature of the container gradually returned to room temperature. During this period, stirring was carried out in the container. After stirring at room temperature, the solvent of the obtained reaction mixture was removed by distillation under reduced pressure. The obtained crude product was purified by distillation. A yellow liquid was obtained.

[0066] The compound of the above yellow liquid was confirmed to be (iPrO)2Ti(NMe2)2 by AVANCEIII400.

[0067] The above compound was confirmed by TG-DTA 8122 / S to have a weight loss rate of 99.8% and a T50 of 150.1°C (see Figure 2). It was found that the above compound has good volatility and good thermal stability. Therefore, it can be said that it is a suitable precursor for forming a Ti-containing film.

[0068] [Example 2] [Experiment 1: Formation of Ti oxide film by ALD using compound 1 and water (H2O)] Compound 1[(EDA-tBu2)Ti(NMe2)2] obtained in Example 1 was used as a precursor. A Ti oxide film was deposited on a silicon substrate using an ALD apparatus (see Figure 3). The substrate was heated to 100°C to 250°C. The precursor, placed in a stainless steel container, was heated to 70°C. 100 sccm of nitrogen gas was supplied into the container. The precursor was transported to the deposition chamber for 4 seconds. After this, nitrogen gas was supplied to the deposition chamber for 10 seconds. After this, H2O (gas) was supplied to the deposition chamber for 1 second. After this, nitrogen gas was supplied to the deposition chamber for 10 seconds. These processes were repeated 100 times. Figure 4 shows the film thickness per ALD cycle of the Ti oxide film formed by the above process. From Figure 4, it can be seen that the film thickness per ALD cycle is almost constant in the substrate temperature range of 100°C to 250°C. The region in which the film growth rate does not depend on the deposition temperature is called the ALD window. It is said that ideal ALD is performed in this ALD window region. At temperatures higher than the ALD window, the gas phase precursor decomposes, and the chemical reaction proceeds continuously. The film grows without self-control. The film thickness increases. At temperatures lower than the ALD window, for example, the film thickness may increase. This is when a precursor that arrives on the substrate or film surface forms intermolecular bonds with the next precursor that arrives, forming a thin film layer, that is, when an aggregation reaction proceeds. Since this aggregation reaction proceeds at lower temperatures, the film thickness increases at lower temperatures. Whether at low or high temperatures, if the film growth rate depends on the deposition temperature, it becomes difficult to control the film. Compound 1 has a wide ALD window region (100 to 250°C). Therefore, compound 1 is a useful film-forming material at film formation temperatures of 150°C or lower.

[0069] The refractive index of the titanium oxide film deposited in the above process was measured. According to a spectroscopic ellipsometer (HORIBA Jobin Yvon UVISEL-M200-FUV-FGMS), the refractive index of the titanium oxide film deposited at a substrate temperature of 100°C was 2.37. The refractive index of the titanium oxide film deposited at a substrate temperature of 150°C was also 2.37. The titanium oxide film formed using compound 1 had a high refractive index. The curvature of the lens surface decreases as the refractive index increases. Lenses can be made thinner as the refractive index increases. For these reasons, the titanium oxide film according to this invention, with its high refractive index, is also superior in the field of optical lenses.

[0070] The titanium oxide film formed in the aforementioned process was analyzed using an X-ray photoelectron spectroscopy (XPS: Shimadzu Corporation AXIS-Nova). The analysis revealed that the carbon (C) content was less than 1 atm% and the nitrogen (N) content was also less than 1 atm%. This confirmed that the titanium oxide film was of high quality. Compound 1 is suitable as a raw material for forming a high-quality titanium oxide film when the film formation temperature is 150°C or lower.

[0071] [Experiment 2: Formation of Ti oxide film by ALD using compound 2 and water (H2O)] Compound 2[(iPrO)2Ti(NMe2)2] obtained in Example 1 was used as a precursor. A Ti oxide film was deposited on a silicon substrate by ALD. The substrate was heated to 100°C to 300°C. The precursor, placed in a stainless steel container, was heated to 30°C. 100 sccm of nitrogen gas was supplied into the container. The precursor was transported to the deposition chamber for 5 seconds. After this, nitrogen gas was supplied to the deposition chamber for 10 seconds. After this, H2O (gas) was supplied to the deposition chamber for 5 seconds. After this, nitrogen gas was supplied to the deposition chamber for 10 seconds. These processes were repeated 100 times. Figure 5 shows the film thickness per ALD cycle of the Ti oxide film formed by the above process. It can be seen that film growth per ALD raw material supply cycle is constant in the film formation temperature range of 150°C to 250°C. However, below 150°C, there is a large change in film growth. In other words, the range between 100°C and 150°C cannot be called the ALD window region. Controlling the titanium oxide film is difficult. Compound 2 cannot be said to be a useful film formation material at film formation temperatures below 150°C.

[0072] The refractive index of the titanium oxide film deposited in the above process was measured. According to a spectroscopic ellipsometer (HORIBA Jobin Yvon UVISEL-M200-FUV-FGMS), the refractive index of the titanium oxide film deposited at a substrate temperature of 100°C was 2.18. The refractive index of the titanium oxide film deposited at a substrate temperature of 150°C was 2.29. The titanium oxide film formed using compound 2 cannot be said to have a high refractive index.

[0073] The titanium oxide film formed in the aforementioned process was analyzed using an X-ray photoelectron spectroscopy (XPS: Shimadzu Corporation AXIS-Nova). The analysis revealed that the carbon (C) content was less than 1 atm% and the nitrogen (N) content was also less than 1 atm%. This confirmed that the titanium oxide film was of high quality.

[0074] Both compound 1 [(EDA-tBu2)Ti(NMe2)2] and compound 2 [(iPrO)2Ti(NMe2)2] were liquids. From the viewpoint of volatility and thermal stability, both can be said to be useful materials for film formation. This can be understood from the fact that the amount of C and N impurities in the formed Ti oxide film is less than 1 atm%. In other words, it can be said that the difference between the group (EDA-tBu2) and the group (iPrO) does not have an effect in the process of forming a high-purity Ti oxide film. Even in the process using the common amidate Ti(NMe2)4, the difference in substituents does not have an effect, as the amount of C and N impurities is less than 1 atm%.

[0075] Table 1 shows the refractive index of the Ti oxide film formed using the above compound at a deposition temperature of 150°C or lower. Table-1 Film forming temperature 100℃ 150℃ Compound 1 2.37 2.37 Compound 2 2.18 2.29 The only difference between compound 1 [(EDA-tBu2)Ti(NMe2)2] and compound 2 [(iPrO)2Ti(NMe2)2] is the group (EDA) and the group (OR) bonded to Ti. However, no one could have predicted that this difference would cause a significant difference in the refractive index of the Ti oxide film during a film deposition process at relatively low temperatures below 150°C. This was discovered for the first time through the present invention. The refractive index of a Ti oxide film deposited at 110°C using the common amide compound Ti(NMe2)4 was 2.14. The only difference between Ti(NMe2)4 and compound 1 is the presence or absence of a group (EDA) that bonds to Ti. No one could have predicted that this difference would cause such a significant difference in the refractive index of the Ti oxide film in a relatively low-temperature film deposition process below 150°C. This was discovered for the first time through the present invention. The only difference between Ti(NMe2)4 and the compound 2[(iPrO)2Ti(NMe2)2] is the presence or absence of a group (OR) bonded to Ti. This difference did not significantly affect the refractive index of the Ti oxide film during the film deposition process at relatively low temperatures below 150°C. This suggests that the group (EDA) likely had a significant impact on the refractive index of the Ti oxide film during the film deposition process at relatively low temperatures below 150°C.

[0076] No one could have predicted that the EDA group would significantly affect the refractive index of the Ti oxide film, even in a film deposition process at relatively low temperatures below 150°C, while keeping the C and N impurity levels of the Ti oxide film below 1 atm%. This fact was discovered for the first time through this invention. The fact that [(EDA-tBu2)Ti(NMe2)2] is a high-quality film with less than 1 atm% C and N impurities in the deposited Ti oxide film when deposited in a relatively low-temperature film deposition process below 150°C, and that the deposited Ti oxide film has a very high refractive index of 2.3 or higher, indicates that it is a good choice as a material for forming Ti oxide films.

[0077] To illustrate the nature of the present invention, it will be understood that many further modifications, including details such as materials, processes, and components, described and shown herein can be made by those skilled in the art within the principles and scope of the present invention as expressed in the appended claims.

[0078] The present invention is not intended to be limited to the above-described examples and / or embodiments.

Claims

1. A method for forming a titanium oxide film, (R １ , R ２ -EDA)Ti(NR ３ R ４ ) ２ (EDA is N １ , N ２ -dialkyl-ethylenediamine. R １ , R ２ , R ３ , R ４ is a hydrocarbon group.) The compound represented by is supplied into the film formation chamber, A titanium oxide film is formed on the substrate in the aforementioned film deposition chamber. Film formation method.

2. The hydrocarbon group has 1 to 4 carbon atoms. The method for forming a film according to claim 1.

3. The hydrocarbon group is an alkyl group. The method for forming a film according to claim 2.

4. The alkyl group is selected from the group consisting of Me, Et, and tBu. The method for forming a film according to claim 3.

5. R, which is the alkyl group １ , R ２ tBu is The method for forming a film according to claim 4.

6. R, which is the alkyl group １ , R ２ R is the alkyl group, where tBu is the alkyl group. ３ , R ４ That is Me The method for forming a film according to claim 5.

7. The film deposition temperature is 150°C or lower. The method for forming a film according to claim 6.

8. A weak oxidizing agent is used for film formation. The method for forming a film according to claim 7.

9. The oxidizing agent is H ２ It is O The method for forming a film according to claim 8.

10. Oxidizing agent is O ２ That is The method for forming a film according to claim 8.

11. ALD or CVD is used for film formation. A method for forming a film according to claim 1 or claim 7.

12. The impurities (C, N) in the titanium oxide film are 1 atm% or less. The method for forming a film according to claim 1.

13. The refractive index of the titanium oxide film is 2.3 or higher. The method for forming a film according to claim 1.

14. A material used for forming titanium oxide films, The aforementioned material is (R １ , R ２ -EDA)Ti(NR ３ R ４ ) ２ (EDA is N １ ,N ２ It is a dialkyl-ethylenediamine. １ , R ２ , R ３ , R ４ ( is a hydrocarbon group.) The compound has a hydrocarbon group. Thin-film deposition materials.

15. The aforementioned material is liquid at 25°C (1 atmosphere). The film-forming material according to claim 14.

16. The hydrocarbon group has 1 to 4 carbon atoms. The film-forming material according to claim 14.

17. The hydrocarbon group is an alkyl group. The film-forming material according to claim 14.

18. The alkyl group is selected from the group consisting of Me, Et, Pr, and Bu. The film-forming material according to claim 17.

19. The aforementioned R １ , R ２ At least one of them is tBu. The film-forming material according to claim 14.

20. The aforementioned R １ , R ２ tBu is The film-forming material according to claim 14.

21. The aforementioned R ３ , R ４ This is one of the groups Me and Et. The film-forming material according to claim 14.

22. The aforementioned R ３ , R ４ That is Me The film-forming material according to claim 14.

23. The aforementioned R １ , R ２ tBu, the R ３ , R ４ That is Me The film-forming material according to claim 14.

24. (R １ , R ２ -EDA)Ti(NR ３ R ４ ) ２ (EDA is N １ ,N ２ It is a dialkyl-ethylenediamine. １ , R ２ , R ３ , R ４ It is a hydrocarbon group. New compound.

25. The novel compound is a liquid at 25°C (1 atm). A novel compound according to claim 24.

26. The hydrocarbon group has 1 to 4 carbon atoms. A novel compound according to claim 24.

27. The hydrocarbon group is an alkyl group. A novel compound according to claim 24.

28. The aforementioned R １ , R ２ , R ３ , R ４ is one of the groups Me, Et, Pr, and Bu. A novel compound according to claim 24.

29. The aforementioned R １ , R ２ At least one of them is tBu. A novel compound according to claim 24.

30. The aforementioned R １ , R ２ tBu is A novel compound according to claim 24.

31. The aforementioned R ３ , R ４ This is one of the groups Me and Et. A novel compound according to claim 24.

32. The aforementioned R ３ , R ４ That is Me A novel compound according to claim 24.

33. The aforementioned R １ , R ２ tBu, the R ３ , R ４ That is Me A novel compound according to claim 24.

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