Method for manufacturing high-purity molybdenum oxychloride

Abstract

A molybdenum oxychloride has a purity of 99.9995% by weight or higher. A method for producing molybdenum oxychloride involves reacting MoO3 with Cl2 in a reaction chamber to synthesize molybdenum oxychloride, cooling the synthesized molybdenum oxychloride gas, and precipitating the molybdenum oxychloride in a recovery chamber, thereby producing molybdenum oxychloride. The method is characterized by providing an impurity trap between the reaction chamber and the recovery chamber, and removing impurities in the impurity trap. The objective of this invention is to provide a high-purity molybdenum oxychloride and a method for its production.

Description

Technical Field

[0001] This invention relates to a high-purity molybdenum oxychloride and its manufacturing method, which can be preferably used as a material for vapor phase growth of thin films, a catalyst for chemical reactions, etc. Prior Technology

[0002] Traditionally, thin films such as molybdenum (Mo) or tungsten (W), which are physically and chemically stable and have low electrical resistance, are commonly used in contact plugs, wiring, or diffusion barrier layers within functional electronic devices such as semiconductor components. Furthermore, thin films of compounds such as nitrides and carbides of these metals are also frequently used in diffusion barrier layers. Molybdenum or molybdenum compound thin films are formed using chemical vapor deposition (CVD), where a molybdenum-containing compound is used as a precursor and evaporated and vaporized, thereby decomposing and reacting on the substrate surface to form a thin film.

[0003] Furthermore, with the increasing integration, density, and narrow spacing of devices in recent years, as well as the deep extension of contact plugs, there is a tendency for metal layers to be formed in high aspect ratio recesses. In order to uniformly form a metal layer in the recess with such a high aspect ratio, the following techniques are used: using atomic layer deposition (ALD) to uniformly form a thin metal layer as a seed layer in the recess, and then using the aforementioned CVD method or plating method to form a thick metal layer for contact plugs or wiring.

[0004] Regarding the precursor compounds used in forming metals or metal compounds by the aforementioned CVD or ALD methods, there are organometallic compounds, metal carbonyl compounds, metal halides, etc. Examples of such known techniques include: forming a MoS2 film using molybdenum chloride (MoCl5) (Patent Document 1); forming a Mo film using a molybdenum carbonyl compound (Mo(CO)6) (Patent Document 2); forming a Mo film using an organometallic compound of molybdenum (Patent Document 3); and forming MoS2 (Patent Document 4).

[0005] However, molybdenum chloride, specifically molybdenum pentachloride (MoCl5), is unstable and decomposes to produce toxic hydrogen chloride, making it difficult to handle. This raises concerns about storage and handling for its use in industrial processes. Furthermore, while CVD or ALD using metal carbonyl compounds as raw materials does not present the aforementioned problems, it does have the following drawbacks: besides their inherent toxicity, the vapor pressure of molybdenum-containing metal carbonyl compounds is low, making it difficult to control the flow rate and pressure of the raw material gas during CVD or ALD film formation.

[0006] Therefore, as disclosed in Patent Document 5 or Non-Patent Document 1, there are methods for CVD film formation of molybdenum or molybdenum compounds using molybdenum oxychloride (MoOCl2, MoOCl3, MoOCl4, MoO2Cl2) as a raw material precursor. Besides being a CVD raw material, molybdenum oxychloride is also known as a catalyst for chemical reactions such as organic synthesis, as disclosed in Patent Documents 6 and 7 and Non-Patent Document 2. As described in Non-Patent Document 3, molybdenum oxychloride is synthesized by directly chlorinating molybdenum oxide powder with chlorine gas. Previous technical documents Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-225808 Patent Document 2: Japanese Patent Publication No. 2008-520834 Patent Document 3: Japanese Patent Application Publication No. 2006-097101 Patent Document 4: Japanese Patent Publication No. 11-507629 Patent Document 5: Japanese Patent Application Publication No. 2000-119045 Patent Document 6: Japanese Patent Application Publication No. 2003-252845 Patent Document 7: Japanese Patent Application Publication No. 08-277263 Non-patent literature

[0008] Non-patent literature 1: KA Gesheva et al., Thin Solid Films, Vol.79, 1981, pp. 39-49 Non-patent literature 2: Rita G, de Noronha et al., Cat. Commun., Vol.12, 2011, pp. 337-340 Non-patent literature 3: Y. Monteil et al., J. Cryst. Growth, Vol. 67, 1984, pp. 595-606 Summary of the Invention

[0009] [The problem that the invention aims to solve] Molybdenum oxychloride can be synthesized, for example, by chlorinating molybdenum oxide (MoO3) powder using chlorine gas (Cl2). In this process, impurities can be separated to some extent by properly managing the synthesis temperature. However, metallic impurities such as tungsten (W) present in the raw material form chlorides or oxychlorides, and these are difficult to remove due to their high vapor pressure. In particular, the high concentration of W present in the raw material MoO3 results in a high concentration of molybdenum oxychloride remaining in the final product. The present invention aims to solve this problem by providing a high-purity molybdenum oxychloride and a method for its production. [Technical means to solve the problem]

[0010] Through dedicated research, the inventors have obtained the following insights, thereby completing this invention: by setting an impurity trap in the apparatus used to synthesize high-purity molybdenum oxychloride, chlorides such as tungsten (W) with higher vapor pressure can be effectively separated, thus producing high-purity molybdenum oxychloride. Based on the above understanding, one embodiment of the present invention is defined as follows: a molybdenum oxychloride having a purity of 99.9995% by weight or more. Furthermore, in the present invention, the molybdenum oxychloride comprises any one of MoOCl2, MoOCl3, MoOCl4, and MoO2Cl2. [Effects of the Invention]

[0011] According to the present invention, tungsten (W) and other elements that are difficult to remove in the synthesis process can be separated to obtain high-purity molybdenum oxychloride. Furthermore, by using this high-purity molybdenum oxychloride as a precursor in CVD or ALD processes, the following excellent effects are achieved: the thin film in a semiconductor device can avoid the undesirable properties caused by impurity metals. Simple Explanation of the Diagram

[0012] [Figure 1] is a schematic diagram of the apparatus used to synthesize molybdenum oxychloride. Implementation

[0013] Molybdenum oxychloride can be synthesized by chlorinating molybdenum oxide (MoO3) powder with chlorine gas. However, the raw material, molybdenum oxide powder, contains a relatively high amount of tungsten (W) or iron (Fe) as impurities. These metallic impurities react with chlorine gas during synthesis to form oxychlorides. These oxychlorides have high vapor pressures, making gas-phase separation difficult. Therefore, it has been previously impossible to remove the tungsten and other impurities originating from the raw material, resulting in synthesized molybdenum oxychloride containing approximately 10 wtppm of W, with a purity of approximately 5N (99.999% by weight) excluding W.

[0014] When molybdenum oxychloride containing this impurity is used as a precursor in CVD or ALD processes, the following problem arises: the impurity remains in the molybdenum compound after film formation, leading to a deterioration in film properties. In particular, when used as a thin film in semiconductor multilayer structures, it can reduce device performance. For the reasons stated above, the present invention aims to provide high-purity molybdenum oxychloride. The molybdenum oxychloride in the embodiments of the present invention has a purity of 99.9995% by weight (5N5) or higher. Preferably, the purity is 99.9999% by weight (6N) or higher.

[0015] In this invention, purity is determined by analyzing Ba, W, Ti, Ag, Na, K, Fe, In, Zn, Cu, Cr, and Al using ICP-MS, and then subtracting their total content (wt%) from 100wt%. Furthermore, if the analytical value of any element falls under the conditions described below, it is considered to be below the detection limit, and its content is considered to be 0 (zero). Ba: <0.1 ppm by weight, W: <0.1 ppm by weight, Ti: <0.1 ppm by weight, Ag: <0.1 ppm by weight, Na: <0.1 ppm by weight, K: <1 ppm by weight Fe: <0.1 ppm by weight, In: <0.1 ppm by weight, Zn: <0.1 ppm by weight, Cu: <0.1 ppm by weight, Cr: <0.1 ppm by weight, Al: <0.1 ppm by weight When such elements are used in wiring of electronic devices, they can cause an increase in resistivity, electromigration, and diffusion into the component, which can reduce the performance of the device. Therefore, it is preferable to exclude such elements.

[0016] In embodiments of the present invention, the W (tungsten) content of molybdenum oxychloride is preferably less than 5 ppm by weight. More preferably, it is less than 1 ppm by weight, and even more preferably, it is less than 0.1 ppm by weight. Furthermore, the Fe (iron) content is preferably less than 0.1 ppm by weight. As mentioned above, tungsten or iron is a relatively high amount of impurity in the raw material, namely molybdenum oxide. Furthermore, the vapor pressures of tungsten chloride, ferric chloride, etc., formed during synthesis are relatively high. Therefore, they easily mix into the synthesized molybdenum oxychloride, making gas-phase separation difficult. According to the present invention, these difficult-to-remove impurities can be reduced to an extremely low content.

[0017] In embodiments of the present invention, the sodium (Na) content of molybdenum oxychloride is preferably less than 0.1 ppm by weight. Sodium can react with chlorine or other impurities in the reaction gas to form various salts such as sodium chloride, thus becoming mixed in. As an alkali metal, sodium is particularly prone to degrading the performance of wiring in electronic devices; therefore, it is preferable to reduce its content to less than 0.1 ppm by weight. Similarly, regarding potassium (K), an alkali metal, it is also preferable to reduce it to less than 1 ppm by weight.

[0018] The following is a detailed description of the method for manufacturing molybdenum oxychloride according to an embodiment of the present invention.

[0019] As a raw material, prepare MoO3 (molybdenum trioxide) powder. It is preferable to use high-purity MoO3, with a purity of 3N (99.9% by weight) or higher, excluding tungsten, and more preferably 4N (99.99% by weight) or higher. From the viewpoint of easy feeding through the supply pipe, it is preferable to use raw material with a particle size (D50) of approximately 0.1 mm to 1 mm.

[0020] Figure 1 illustrates one example of a vertical synthesis apparatus 1 used to synthesize molybdenum oxychloride. Furthermore, this apparatus diagram is a schematic representation; the size, shape, connection, and arrangement of the various components are not limited thereto and can be appropriately modified. Additionally, valves or flow control devices can be installed along the gas piping path as needed. The vertical synthesis apparatus 1 mainly comprises a reaction chamber 3, an impurity trap 6, a recovery chamber 8, and a recovery device 9. The reaction chamber 3 includes a reaction vessel 2, a gas supply pipe 4, a raw material supply pipe 5, and a thermocouple 10. Furthermore, the impurity trap 6 contains a physical filter 7.

[0021] Next, the synthesis method will be explained. First, MoO3 powder is supplied to reaction vessel 2 and heated at 700-1000°C. Furthermore, as the MoO3 raw material is consumed during synthesis, resulting in a decrease in MoO3, raw materials can be added as needed through raw material supply pipe 5. Subsequently, chlorine gas is supplied to MoO3 reaction vessel 2 through gas supply pipe 4 for chlorination. At this time, Ar gas, which serves as a carrier gas, can also be introduced. By introducing chlorine gas, MoO3 reacts with Cl2, for example, in the reaction MoO3 + Cl2 → MoO2Cl2 + 0.5O2, to form MoO2Cl2. In addition, MoOCl2, MoOCl3, and MoOCl4 with different degrees of chlorination can also be formed. The generated molybdenum oxychloride is released in gaseous form.

[0022] The molybdenum oxychloride gas obtained from the above synthesis reaction reaches the recovery chamber 8 via the impurity trap 6. At this time, although impurities such as tungsten or iron vaporize and diffuse in the form of chlorides or oxychlorides, they are prevented from entering the recovery chamber 8 by the temperature-controlled impurity trap 6. This can be attributed to the reduced gas flow rate in the impurity trap 6, which traps the impurities.

[0023] Furthermore, it is preferable to install a physical filter such as a glass filter or quartz wool in the impurity trap 6. This can prevent the contamination of Na, which is a solid and can be dispersed. Additionally, impurities such as tungsten or iron recovered through the impurity trap 6 are also precipitated into the physical filter, thereby more effectively preventing discharge to the downstream (recovery chamber). The temperature in the impurity trap 6 is set with the temperature at which MoO2Cl2 is a gas as the lower limit and the temperature at which most impurities become a solid phase as the upper limit; specifically, it is preferably maintained at 150~250℃. Furthermore, by changing the diameter or length of the impurity trap 6, the recovery efficiency and impurity removal rate can be appropriately adjusted.

[0024] Subsequently, the tungsten oxychloride gas, after impurities have been removed, is cooled in the recovery chamber 8 and precipitates out as a solid phase of molybdenum oxychloride. A recovery container 9 is connected below the recovery chamber 8 to recover any precipitates that cannot be completely recovered in the recovery chamber 8 or that fall from the recovery chamber 8. Cooling can be performed naturally. This allows for the acquisition of high-purity molybdenum oxychloride according to the embodiments of the present invention. Furthermore, the recycling container may also be connected to an exhaust stack or vacuum piping, which is used to discharge unreacted chlorine or sublimable chloride and send it to a decontamination device to render them harmless; the vacuum piping is used to send it to a vacuum pump that adjusts the pressure inside the device. Example

[0025] The following is a detailed description of embodiments and comparative examples according to the present invention. The embodiments and comparative examples described below are merely specific examples for the purpose of easily understanding the technical content of the present invention, and the technical scope of the present invention is not limited to these specific examples.

[0026] (Example 1) After MoO3 raw material was filled into the reaction vessel, it was heated to 800°C. Then, chlorine gas was introduced through the gas supply pipe to synthesize MoO2Cl2. Subsequently, the vaporized MoO2Cl2 was passed through an impurity trap (maintained at 190°C) and precipitated in a recovery chamber. The solid phase of MoO2Cl2 was recovered using a recovery container. The synthesis was basically carried out using the apparatus shown in Figure 1, but in Example 1, the physical filter 7 shown in Figure 1 was not installed. The content of each element in the obtained MoO2Cl2 is shown in Table 1. As shown in Table 1, the purity of MoO2Cl2 was 99.9999% by weight, obtaining high purity. Furthermore, the W content was less than 0.1 ppm by weight, and the Fe content was less than 0.1 ppm by weight.

[0027] (Example 2) The synthesis was basically carried out using the apparatus shown in Figure 1. After filling the reaction vessel with MoO3, the mixture was heated to 800°C. Chlorine gas was then introduced through the gas supply pipe to synthesize MoO2Cl2. The vaporized MoO2Cl2 was then passed through an impurity trap (maintained at 190°C with silica wool) and precipitated in a recovery chamber. The solid phase of MoO2Cl2 was recovered using a recovery container. The elemental contents of the obtained MoO2Cl2 are shown in Table 1. As shown in Table 1, the purity of MoO2Cl2 was 99.9999% by weight, achieving high purity. Furthermore, the W content was less than 0.1 ppm by weight, and the Fe content was less than 0.1 ppm by weight.

[0028] (Example 3) The synthesis was basically carried out using the apparatus shown in Figure 1. After filling the reaction vessel with MoO3, the mixture was heated to 800°C. Chlorine gas was then introduced through the gas supply pipe to synthesize MoO2Cl2. The vaporized MoO2Cl2 was then passed through an impurity trap (maintained at 155°C with silica wool) and precipitated in a recovery chamber. The solid phase of MoO2Cl2 was recovered using a recovery container. The elemental contents of the obtained MoO2Cl2 are shown in Table 1. As shown in Table 1, the purity of MoO2Cl2 exceeded 99.9999% by weight, achieving high purity. Furthermore, the W content was less than 0.1 ppm by weight, and the Fe content was less than 0.1 ppm by weight.

[0029] (Example 4) The synthesis was basically carried out using the apparatus shown in Figure 1. After filling the reaction vessel with MoO3 raw material, it was heated to 900°C. Then, chlorine gas was introduced through the gas supply pipe to synthesize MoO2Cl2. Subsequently, the vaporized MoO2Cl2 was passed through an impurity trap (maintained at 190°C) and precipitated in a recovery chamber. The solid phase of MoO2Cl2 was recovered using a recovery container. Furthermore, in Example 4, to improve recovery efficiency, the length of the impurity trap was shortened compared to other examples. The content of each element in the obtained MoO2Cl2 is shown in Table 1. As shown in Table 1, the purity of MoO2Cl2 was 99.9996% by weight, obtaining high purity. Furthermore, the W content was 2.1 ppm by weight, and the Fe content was less than 0.1 ppm by weight.

[0030] (Example 5) The synthesis was basically carried out using the apparatus shown in Figure 1. After MoO3 feedstock was filled into the reaction vessel, it was heated to 900°C. Then, chlorine gas was introduced through the gas supply pipe to synthesize MoO2Cl2. Subsequently, the vaporized MoO2Cl2 was passed through an impurity trap (maintained at 190°C) and precipitated in a recovery chamber. The solid phase of MoO2Cl2 was recovered using a recovery container. The elemental contents of the obtained MoO2Cl2 are shown in Table 1. As shown in Table 1, the purity of MoO2Cl2 was 99.9998% by weight, obtaining a high purity. Furthermore, the W content was 0.8 ppm by weight, and the Fe content was less than 0.1 ppm by weight.

[0031] (Comparative Example 1) After MoO3 raw material was filled into the reaction vessel, it was heated to 800°C. Then, chlorine gas was introduced through the gas supply pipe to synthesize MoO2Cl2. Subsequently, the vaporized MoO2Cl2 was precipitated in the recovery section, and the solid phase of MoO2Cl2 was recovered using a recovery container. Furthermore, the synthesis was basically carried out using the apparatus shown in Figure 1, but in Comparative Example 1, the impurity trap 6 (and physical filter 7) shown in Figure 1 were not installed. The content of each element in the obtained MoO2Cl2 is shown in Table 1. As shown in Table 1, the purity was less than 99.999% by weight, the impurity content (W) was 17 ppm by weight, and the Fe content was 30 ppm by weight.

[0032] The results above are summarized and shown in Table 1. [Table 1] Synthesis temperature (°C) Impurity trap Sink temperature physics Filter Mo (wt%) purity Ba (wtppm) W (wtppm) Ti (wtppm) Ag (wtppm) Na (wtppm) K (wtppm) Fe (wtppm) In (wtppm) Zn (wtppm) Cu (wtppm) Cr (wtppm) Al (wtppm) Example 1 800 long 190 none 47.7 99.9999% 0.4 <0.1 <0.1 0.3 <0.1 <1 <0.1 0.1 <0.1 <0.1 0.2 <0.1 Example 2 800 long 190 have 47.8 99.9999% 0.4 <0.1 0.1 0.3 <0.1 <1 <0.1 <0.1 <0.1 0.1 0.1 <0.1 Example 3 800 long 155 have 48.4 >99.9999% 0.4 <0.1 0.1 0.2 <0.1 <1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Example 4 900 short 190 have 48.3 99.9996% 0.6 2.1 0.3 0.2 <0.1 <1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Example 5 900 long 190 have 47.8 99.9998% 0.6 0.8 0.4 0.2 <0.1 <1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Comparative Example 1 800 none - none 47.1 99.9913% 0.4 17 1.0 1.2 1.8 twenty two 30 0.2 0.7 4.9 0.7 6.7 [Industrial Applicability]

[0033] According to the present invention, in the synthesis of molybdenum oxychloride, impurities that were previously particularly difficult to remove can be reduced to achieve high purity. Therefore, the use of high-purity molybdenum oxychloride as a raw material or catalyst for CVD or ALD makes a significant technological contribution to the industrial / technical fields of semiconductor industry, electronic device manufacturing, functional material generation, and organic / inorganic chemical industry, which involve thin film formation or compound synthesis.

[0034] 1: Synthesis apparatus 2: Reaction vessel 3: Reaction Chamber 4: Gas supply pipe 5: Raw material supply pipeline 6: Impurity trap 7: Physical Filter 8: Recycling Room 9: Recycling Containers 10: Thermocouple

Claims

1. A method for manufacturing molybdenum oxychloride, wherein the molybdenum oxychloride has a purity of 99.9995% by weight or more and a W content of less than 1 ppm by weight, and wherein the method involves reacting MoO3 with Cl2 in a reaction chamber to synthesize molybdenum oxychloride, and cooling the gas of the synthesized molybdenum oxychloride to precipitate molybdenum oxychloride in a recovery chamber, thereby manufacturing molybdenum oxychloride; the method for manufacturing molybdenum oxychloride is characterized in that an impurity trap is provided between the reaction chamber and the recovery chamber, and impurities are removed in the impurity trap.

2. A method for manufacturing molybdenum oxychloride, wherein the molybdenum oxychloride has a purity of 99.9995% by weight or more and a W content of less than 0.1 ppm by weight, and wherein the method involves reacting MoO3 with Cl2 in a reaction chamber to synthesize molybdenum oxychloride, cooling the gaseous product of the synthesized molybdenum oxychloride, and precipitating the molybdenum oxychloride in a recovery chamber, thereby manufacturing molybdenum oxychloride; the method for manufacturing molybdenum oxychloride is characterized in that an impurity trap is provided between the reaction chamber and the recovery chamber, and impurities are removed in the impurity trap.

3. The method for manufacturing molybdenum oxychloride as claimed in claim 1 or 2, wherein a physical filter is provided in the aforementioned impurity trap.

4. The method for manufacturing molybdenum oxychloride as claimed in claim 1 or 2, wherein the temperature of the aforementioned impurity trap is maintained at 150°C to 250°C.

5. The method for manufacturing molybdenum oxychloride as claimed in claim 3, wherein the temperature of the aforementioned impurity trap is maintained at 150°C to 250°C.

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