Production method and production device for a low coefficient of thermal expansion fused silica ingot

Abstract

The present invention relates to a production method and a production device for a quartz glass ingot with a low coefficient of thermal expansion, belonging to the technical field of the production of quartz glass with a low coefficient of thermal expansion. In the present invention, concentrated hydrochloric acid is used as a solvent, and SiCl4 and TiCl4 are used as solutes to prepare a mixed raw material solution; due to the potential solvation effect, silicon atoms and doped atoms are uniformly dispersed in the mixed raw material solution in an ionic state. Thereby, the problem that the existing preparation process is difficult to accurately control the titanium content and cannot maintain its consistency during the production process, resulting in fluctuations in the distribution of doped elements in the quartz block and exacerbating the instability of the properties of the quartz material, is solved. In the present invention, the fluctuation range of the doping material can be reduced by 67%; the fluctuation range of the coefficient of thermal expansion is reduced by 31%; it has a positive significance for the preparation of a quartz glass ingot with a low coefficient of thermal expansion.

Description

Technical Field

[0001] The present invention relates to a production method and a production device for a low-expansion coefficient quartz glass ingot, belonging to the technical field of low-expansion coefficient quartz glass production. Background Art

[0002] In the fields of high-precision optics, lasers, and semiconductor manufacturing, doped ultra-low-expansion quartz glass has attracted much attention due to its excellent thermal stability and low coefficient of thermal expansion. By introducing trace amounts of doping elements, such as titanium, this quartz glass fine-tunes its lattice structure, thus achieving excellent low-expansion performance and meeting the various application requirements in high-demand environments. Especially in EUV lithography machines, the importance of low-expansion quartz materials is mainly reflected in the following aspects: First, it can ensure the high-precision transfer of patterns. During the operation of an EUV lithography machine, extreme ultraviolet light needs to pass through a complex optical system and be projected onto a silicon wafer to create tiny patterns and structures. The low coefficient of thermal expansion of the low-expansion quartz material can minimize the dimensional changes between the silicon wafer and the optical components, thereby transferring patterns with high precision. Second, the excellent thermal stability of the low-expansion quartz material ensures that the optical components can maintain their performance for a long time without deformation or distortion. During the operation of an EUV lithography machine, the optical components need to withstand high-intensity extreme ultraviolet radiation and high-temperature environments. The thermal stability of the low-expansion quartz material enables the optical components to maintain their performance.

[0003] Although doped low-expansion quartz glass plays a key role in fields such as semiconductor manufacturing, the material yield of high-quality low-expansion coefficient quartz glass ingots is relatively low during its preparation process, and the performance consistency of different regions of the low-expansion coefficient quartz glass ingot is relatively poor; the reasons are as follows: 1. It is difficult for the existing process to precisely control the titanium content distribution, and the instability of the titanium content during the preparation process, especially the fluctuation of the titanium content. Even a tiny fluctuation in the titanium content will cause the CTE value of the low-expansion quartz to be unstable; 2. In the existing process method, silicon atoms and doping atoms are distributed in different raw material molecules, resulting in different reaction rates between the titanium raw material and the silicon raw material during the preparation process. Furthermore, it leads to different nucleation and growth rates of particulate matter and fluctuations in the distribution of doping elements in the quartz glass ingot. The superposition of the two finally results in a relatively low material yield of high-quality low-expansion coefficient quartz glass ingots and relatively poor performance consistency of different regions of the low-expansion coefficient quartz glass ingot; therefore, it is necessary to improve it. Summary of the Invention

[0004] The object of the present invention is to provide a method and a production device for a low-expansion coefficient fused silica ingot, which can effectively improve the material yield of high-quality fused silica ingots, and the performance of different regions of the fused silica ingot is stable. It solves the problems that in the existing process, it is difficult to accurately control the distribution of titanium content, and silicon atoms and doped atoms in the existing process are distributed in different raw material molecules, and the reactions of the two are out of sync, resulting in a relatively low material yield of high-quality low-expansion fused silica ingots and relatively poor performance consistency of low-expansion fused silica ingots in different regions.

[0005] The technical solution of the present invention is

[0006] A production device for a low-expansion coefficient fused silica ingot, which is composed of a solvent tank, a crucible, a hydrogen-oxygen burner, a solute tank A, a solute tank B and a mixing tank. It is characterized in that: the crucible is arranged in a melting furnace, and a plurality of hydrogen-oxygen burners are arranged on the melting furnace corresponding to the crucible. A solvent tank is arranged on one side of the melting furnace, and a mixing tank is arranged on one side of the solvent tank. The solvent tank is communicated with the mixing tank through a main communication pipe. The mixing tank is communicated with an evaporator through a branch communication pipe. The evaporator is respectively communicated with a plurality of hydrogen-oxygen burners above the crucible through a branch pipe. Above the communication pipe, there are a solute tank A and a solute tank B, and the solute tank A and the solute tank B are respectively communicated with the main communication pipe through a branch communication pipe.

[0007] A liquid flow pump is arranged at the end of the communication pipe in the solvent tank.

[0008] A method for producing a low-expansion coefficient fused silica ingot by using the above device includes the following steps;

[0009] 1). Start the liquid flow pump on the production device, so that the solvent in the solvent tank enters the main communication pipe under the condition of a flow rate of 10-20 L / min;

[0010] 2). While the solvent enters the main communication pipe, open the valve on the branch communication pipe, so that the silicon material (SiCl4) in the solute tank A and the doped material (TiCl4) in the solute tank B enter the communication pipe in a liquid state at a flow rate of 5-10 L / min at a ratio of 0.05:0.08 (TiCl4 / SiCl4 mass ratio), realize mixing with the solvent, and enter the mixing tank to form a mixed raw material solution;

[0011] 3). Ignite the hydrogen-oxygen burner. The mixed raw material solution in the mixing tank enters the evaporator through the branch pipe to be gasified to form a raw material gas, and the raw material gas enters the feeding pipe of the hydrogen-oxygen burner through the feeding pipe and is ejected;

[0012] 4). The raw material gas ejected from the feeding pipe of the hydrogen-oxygen burner is melted and deposited in the crucible at the focus of the hydrogen-oxygen flame to form a fused silica loose body;

[0013] 5), subject the obtained porous fused silica body to vitrification at a high temperature of 1700 - 1750 °C to obtain a finished fused silica ingot with a low coefficient of thermal expansion.

[0014] Mass flow meters are respectively provided on the connecting branch pipes where the solute tank A, the solute tank B are connected to the main connecting pipe.

[0015] The solvent is a mixed solution of concentrated hydrochloric acid (HCl) and organic acid.

[0016] The concentration of HCl in the concentrated hydrochloric acid is 36 - 38 wt%; among them, the volume ratio of the concentrated hydrochloric acid in the solvent is 30 - 50 vol%.

[0017] The organic acid is chloroacetic acid or acetic acid.

[0018] The applicant found in actual work that the proportion of hydrochloric acid in the solvent, the proportion of the solvent in the mixed raw material solution, and the different ratios of the solutes SiCl4 and TiCl4 have a direct impact on the final product. Therefore, the applicant conducted experiments with different ratios, and the specific results are as follows:

[0019] Experiment on the proportion of hydrochloric acid in the solvent (after mixing, the volume fraction of the solvent in the solution is 50 vol%)

[0020]

[0021] Conclusion: High-concentration hydrochloric acid can maintain the strong acidity of the solution and suppress the hydrolysis reaction of silicon and titanium materials. The organic acid can keep the solution homogeneous, reduce the water content in the solution, and enhance the stability of the solution. The proportion of hydrochloric acid in the solvent should be controlled at about 30 vol% - 70 vol% to ensure that both the hydrolysis reaction of silicon and titanium materials can be inhibited and the homogeneity of the solution can be maintained.

[0022] Experiment on the proportion of the solvent in the mixed raw material solution: (the solvent is 60 vol% hydrochloric acid + 40 vol% organic acid)

[0023] .

[0024] Conclusion: The higher the solvent component, the more uniform the Ti content distribution. The combination of solvent molecules with silicon and titanium atoms becomes more and more common with the increase of the solvent component, increasing the synchronism of the reaction of silicon and titanium atoms and reducing the uneven distribution of titanium elements in different-sized particles.

[0025] The beneficial effects of the present invention are as follows:

[0026] The present invention prepares a mixed raw material solution using hydrochloric acid as a solvent and silicon material (SiCl4) and doping material (TiCl4) as solutes; due to potential solvation, silicon atoms and doping atoms (such as titanium atoms) are uniformly dispersed in the mixed raw material solution in an ionic state. Among them, silicon atoms and doping atoms form stable ionic groups in the form of complex ions; in the gasification process of the mixed raw material solution in this state, the atomic groups where silicon atoms and titanium atoms are located are connected as a whole and undergo high-temperature hydrolysis under the conditions of the hydrogen-oxygen flame of the burner. Among them, silicon and titanium atoms react in situ and synchronously to form particulate matter and melt; thus, it solves the problem that the existing preparation process is difficult to accurately control the distribution of titanium content and the fluctuation of the distribution of doping elements in quartz blocks caused by the inability to maintain its consistency during the production process, which exacerbates the instability of the performance of quartz materials. In the present invention, the fluctuation range of the doping material can be reduced by 67%; the fluctuation range of the thermal expansion coefficient is reduced by 31%; it has a positive significance for the preparation of low-expansion coefficient quartz glass ingots.

[0027] Invention mechanism

[0028] In the present invention, by mixing silicon raw material and doping raw material in a solvent system, due to potential solvation, silicon atoms and doping atoms (such as titanium atoms) are uniformly dispersed in the solution in an ionic state. Among them, silicon atoms and doping atoms form stable ionic groups. Subsequently, this mixed material solution is stable and clear. This is different from the conventional understanding that silicon raw material substances (such as SiCl4) and doping raw material substances (such as TiCl4) undergo hydrolysis reactions when they encounter water (as shown in the following reaction equation).

[0029]

[0030] In the presence of a large amount of strong acid and when the volume fraction of water does not dominate the solution, according to the principle of reaction equilibrium, the forward reaction degree of this reaction is inhibited. In addition, when organic acid (such as acetic acid) dominates the volume, the organic acid and HCl undergo complex dissociation:

[0031]

[0032] When organic acid (such as acetic acid) is the main body of the solvent, HCl not only acts as a strong acid but also reduces the presence of water in the system. In this strong electrolyte environment of the solution, silicon material and doping material coexist in the same solution system without hydrolysis precipitation. In addition, due to acetic acid molecules being the main component of the solvent, the process of its combination with Si4+:

[0033]

[0034] It can also compete with the hydrolysis reaction of Si4+. However, the reaction product can be stably dispersed in the solvent, which is different from directly generating a precipitate when reacting with water. When the solution in this state is evaporated, the atomic groups where silicon atoms and titanium atoms are located are connected as a whole. In the subsequent high-temperature hydrolysis, silicon and titanium atoms react in situ and synchronously to form the same particulate matter. Thus, the problems that the existing preparation process is difficult to accurately control the titanium content distribution and cannot maintain its consistency during the production process are solved.

[0035] When producing with the raw material solution of this application, a comparison is made between the fluctuation of the content of doped elements measured on the same diameter and that of another production using chlorides as raw materials. Taking the single experimental result as an example (see Figure 2 - Comparison of the distribution of doped element content along the diameter), in the figure, the solid line represents the quartz ingot melted by feeding the solution described in the present invention, and the XRF is used to measure the titanium content at its radial distribution positions.

[0036] The dashed line represents the quartz ingot melted by feeding traditional SiCl4 and TiCl4, and the XRF is also used to measure the titanium content at the radial distribution positions.

[0037] It can be seen from Figure 2 that producing by feeding the solution described in the present invention can reduce the fluctuation of doped elements caused by position changes. The corresponding coefficient of thermal expansion CTE can also have a smoother and more uniform distribution accordingly. Therefore, producing by feeding the solution described in the present invention can reduce the fluctuation of the coefficient of thermal expansion and improve the consistency of the performance of each region of the low-expansion quartz ingot. Brief Description of the Drawings

[0038] Figure 1 is a schematic structural diagram of the production device of the present invention;

[0039] Figure 2 is a comparison diagram of the distribution of the content of doped raw materials along the diameter of the present invention.

[0040] In the figure: 1. Solvent tank, 2. Crucible, 3. Hydrogen-oxygen burner, 4. Solute tank A, 5. Solute tank B, 6. Mixing tank, 7. Furnace, 8. Evaporator, 9. Connecting main pipe, 10. Mass flowmeter. Detailed Embodiments

[0041] The production device of the low-expansion coefficient fused quartz ingot consists of a solvent tank 1, a crucible 2, a hydrogen-oxygen burner 3, a solute tank A 4, a solute tank B 5, and a mixing tank 6. The crucible 2 is arranged in a furnace 7, and a plurality of hydrogen-oxygen burners 3 are arranged at the top of the furnace corresponding to the crucible 2. A solvent tank 1 is arranged on one side of the furnace 7, and a mixing tank 6 is arranged on one side of the solvent tank 1. The solvent tank 1 is communicated with the mixing tank 6 through a main connecting pipe 9, and a liquid flow pump is arranged at the end of the main connecting pipe 9 in the solvent tank 1. The mixing tank 6 is communicated with an evaporator 8 through a connecting branch pipe, and the evaporator 8 is respectively communicated with a plurality of hydrogen-oxygen burners 3 on the furnace 7 through branch pipes. Above the main connecting pipe 9, there are a solute tank A 5 and a solute tank B 6, and the solute tank A 5 and the solute tank B 6 are respectively communicated with the main connecting pipe 9 through connecting branch pipes. Mass flow meters 10 are respectively arranged on the connecting branch pipes where the solute tank A 5 and the solute tank B 6 are communicated with the main connecting pipe 9 and on the main connecting pipe 9.

[0042] The method for producing a fused quartz ingot with a low expansion coefficient by using the above device is as follows;

[0043] Start the liquid flow pump on the production device, so that the solvent in the solvent tank 1 enters the main connecting pipe 9 under the flow rate condition of 10 - 20 L / min. The solvent is a mixture of concentrated hydrochloric acid and one or more organic acids with any ratio. Among them, the concentration of HCl in the concentrated hydrochloric acid is 36 - 38 wt%, and the volume ratio of the concentrated hydrochloric acid in the solvent is 30 - 50 vol%. The organic acid is chloroacetic acid or acetic acid.

[0044] While the solvent enters the main connecting pipe 9, open the valve on the connecting branch pipe, so that the silicon material (SiCl4) in the solute tank A 5 and the doping material in the solute tank B 6 enter the main connecting pipe 9 in a liquid state under the flow rate condition of 5 - 10 L / min, realize mixing with the solvent, and enter the mixing tank 6 to form a mixed raw material solution. Ignite the hydrogen-oxygen burner 3, and the mixed raw material solution in the mixing tank 6 is pumped into the evaporator 8 through the branch pipe to be vaporized to form a raw material gas. The raw material gas enters the feeding pipe of the hydrogen-oxygen burner 3 through the branch pipe and is ejected. The raw material gas ejected from the feeding pipe of the hydrogen-oxygen burner 3 is melted and deposited in the crucible 2 at the focus of the hydrogen-oxygen flame to form a fused quartz loose body; the obtained fused quartz loose body is vitrified under the high temperature condition of 1700 - 1750 °C to obtain a finished product of a fused quartz ingot with a low expansion coefficient.

[0045] Table of solvent composition and ratio between solutes in each embodiment of the present invention

[0046]

[0047] Detection results of product performance prepared in each embodiment of the present invention

[0048] 。

Claims

1. A production method of a quartz glass ingot with a low coefficient of thermal expansion, characterized in that: It includes the following steps; 1), Start the liquid flow pump on the low-expansion coefficient fused quartz ingot production device, so that the solvent in the solvent tank enters the connecting main pipe at a flow rate of 10 - 20 L / min; 2), While the solvent enters the connecting main pipe, open the valve on the connecting branch pipe, so that the silicon material in the solute tank A and the doping material in the solute tank B enter the connecting pipe in a liquid state at a weight ratio of 0.05:0.08 and a flow rate of 5 - 10 L / min, realize mixing with the solvent, and enter the mixing tank to form a mixed raw material solution; 3), Ignite the hydrogen-oxygen burner. The mixed raw material solution in the mixing tank enters the evaporator through the branch pipe to be gasified to form a raw material gas. The raw material gas enters the feeding pipe of the hydrogen-oxygen burner through the feeding pipe and is ejected; 4), The raw material gas ejected from the feeding pipe of the hydrogen-oxygen burner is melted and deposited in the crucible at the focus of the hydrogen-oxygen flame to form a fused quartz loose body; 5), Vitrify the obtained fused quartz loose body at a high temperature of 1700 - 1750 °C to obtain a finished product of a fused quartz ingot with a low expansion coefficient; The solvent is a mixture of concentrated hydrochloric acid and organic acid.

2. The production method of a low-expansion coefficient quartz glass ingot according to claim 1, characterized in that: The low-expansion coefficient fused quartz ingot production device described in step 1) is composed of a solvent tank (1), a crucible (2), a hydrogen-oxygen burner (3), a solute tank A (4), a solute tank B (5) and a mixing tank (6). It is characterized in that: the crucible (2) is arranged in the furnace (7), multiple hydrogen-oxygen burners (3) are arranged at the top of the furnace (7) corresponding to the crucible (2), a solvent tank (1) is arranged on one side of the furnace (7), a mixing tank (6) is arranged on one side of the solvent tank (1), the solvent tank (1) is communicated with the mixing tank (6) through a connecting main pipe (9), the mixing tank (6) is communicated with the evaporator (8) through a connecting branch pipe, the evaporator (8) is respectively communicated with multiple hydrogen-oxygen burners (3) above the crucible (2) through branch pipes, a solute tank A (4) and a solute tank B (x) are arranged above the connecting main pipe (9), and the solute tank A (4) and the solute tank B (5) are respectively communicated with the connecting main pipe (9) through connecting branch pipes.

3. The production method of a low-expansion coefficient quartz glass ingot according to claim 2, characterized in that: A liquid flow pump is arranged at the end of the connecting main pipe (9) in the solvent tank (1).

4. The production method of a low-expansion coefficient quartz glass ingot according to claim 2, characterized in that: Mass flow meters (10) are respectively arranged on the connecting branch pipes through which the solute tank A (4) and the solute tank B (5) are communicated with the connecting main pipe (9).

5. The production method of a low-expansion coefficient quartz glass ingot according to claim 1, characterized in that: The concentration of HCl in the concentrated hydrochloric acid is 36 - 38 wt%; among them, the volume ratio of the concentrated hydrochloric acid in the solvent is 30 - 50 vol%.

6. The production method of a low-expansion coefficient quartz glass ingot according to claim 1, characterized in that: The organic acid is any one or a mixed solution of organic acids with any ratio of glacial acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid.

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