CN114735927A - A method of producing synthetic quartz material for semiconductor reticle - Google Patents

Abstract

The invention relates to a method for producing a synthetic quartz material for a semiconductor mask, which comprises the following steps: (1) depositing a silicon source on the guide rod by adopting a gas-phase axial deposition method to obtain low-density SiO₂A loose body; wherein in the deposition process, the interior of the deposition cavity is controlled to be in a negative pressure environment, and the temperature is not higher than 500 ℃; (2) mixing low density SiO₂Transferring the loose body to a sintering furnace, heating to 1100-1300 ℃ in a closed environment filled with dehydroxylation airflow and oxygen, and enabling the low-density SiO to be in a state of being heated₂Dehydrating the loose body; (3) introducing fluorine-containing gas into the sintering furnace in an inert gas environment, and heating to 1400-1600 ℃ to ensure that the low-density SiO₂Vitrifying the loose body to form transparent quartz glass; low density SiO during dehydration and vitrification₂The loose body keeps not moving longitudinally, and a deposition cavity is formedThe temperature gradient between the inner longitudinal direction and the radial direction is less than or equal to 2 ℃; (4) and annealing the transparent quartz glass to obtain the synthetic quartz material. The method has high continuity of the production process and synthesizes the quartz product T_170‑193nm≥95％。

Description

A method of producing synthetic quartz material for semiconductor reticle

technical field

The invention relates to the technical field of quartz preparation, in particular to a method for producing a synthetic quartz material for a semiconductor mask.

Background technique

Quartz glass is a special glass composed of a single component of silicon dioxide, and its chemical formula is SiO ₂ . Quartz has unique optical, mechanical and thermal properties, including: high softening temperature, strong heat resistance; high purity, corrosion resistance; low thermal expansion coefficient, thermal shock resistance; good light transmittance from the ultraviolet band to the infrared band ; Strong radiation resistance; excellent electrical insulation, etc. The above properties make quartz products widely used in aerospace, laser optics, semiconductors, optical communications, metallurgy, chemical and other high-end manufacturing fields.

Traditional optical quartz glass preparation processes include electrofusion, gas refining, chemical vapor deposition (CVD), indirect synthesis and sol-gel methods. Both the electrofusion and gas smelting processes use high-purity quartz sand as the raw material, and are fused into quartz glass at a high temperature above 1800 °C. Defects such as more dots have a great influence on the physical and chemical properties of the glass.

The CVD direct synthesis process currently mainly adopts the vertical process, but it also has a significant disadvantage, that is, the hydroxyl content is too high, which leads to the reduction of the high temperature resistance of the prepared quartz glass, and the physical properties such as refractive index and thermal expansion coefficient are also affected. Meet the application needs of high-end optoelectronic technology and semiconductor fields.

The indirect synthesis method is a process technology developed in the past ten years. The light absorption coefficient of quartz prepared by this technology is very small, the hydroxyl content is controllable (1-1000ppm), the spectral transmittance T _157-4000 nm≥80%, and Because of easy doping and control of defects.

The photomask is a graphic master used in the photolithography process in microelectronics manufacturing. Its core function is: as a mold, the circuit pattern on the mask is copied to the chip or the liquid crystal panel glass through photolithography technology, so as to be batched. Production of integrated circuits or LCD panels and other products. The photomask substrate material must have flawless interior and exterior surfaces and high optical transmittance at the exposure wavelengths of the photoresist. At present, the integrated circuit industry is developing rapidly, the size of silicon wafers is expanding to 8→12→16, the integration degree is getting higher and higher, and the exposure light is also changed from visible light to near-ultraviolet light, and even far-ultraviolet light. Due to defects such as any tiny bubbles in the quartz glass substrate, the chip patterning will cause fatal errors, which will seriously affect the chip performance, which also puts forward higher requirements for the quartz glass substrate for photomasks: high ultraviolet transmittance, high optical uniformity performance, high intrinsic quality and high surface finish.

The glasses used to make photomasks include synthetic quartz, borosilicate glass and soda glass. Among them, synthetic quartz is the most chemically stable and has the advantages of high hardness, low expansion coefficient and strong light transmittance. It is produced by products requiring higher precision. The best choice, it is widely used in the manufacture of photomasks for LSI and large-scale masks for FPD. Synthetic quartz can provide a wide light projection area, low impurity content, and few physical defects, and with the development of semiconductors, it requires more and more deep UV, high uniformity of synthetic quartz. Existing synthetic quartz manufacturing cannot satisfy high-precision reticles for semiconductors.

Therefore, in order to meet the high uniformity and high transmittance of synthetic quartz for semiconductor photomasks, the following two aspects need to be solved: metal impurity content and defect control inside quartz;

1) The existence of transition metal impurities in synthetic quartz glass will cause the absorption of light through outdated, resulting in the absorption of a large amount of energy by the transition metal. Alkali metal and alkali metal ions are uniformly and disorderly distributed in the voids of the quartz, which changes the structure of silica silicon and oxygen, forms non-bridging oxygen ions, and causes absorption.

During the deposition process, the silicon tetrachloride raw material is hydrolyzed at high temperature to form silicon dioxide. The process involves high temperature reactions (reaction temperatures typically exceeding 1000°C), accompanied by the production of large amounts of hydrogen chloride. Since most of the materials inside the deposition chamber are made of metal materials, metal chloride gas is easily generated under high temperature conditions and high corrosive environments. The metal chloride gas flows with the gas flow in the deposition chamber and is deposited on the quartz material. materials causing contamination. The corrosion of the cavity during the high temperature hydrolysis reaction makes the metal impurity contamination of the quartz material inevitable, making it more difficult to reduce the metal impurity content in the quartz material.

四面体角

平均键角约109°；间四面体角α(Si-O-Si)，平均键角约144°-150°，分布范围在120°到180°；还包括键扭转角δ1和δ2等，正是因为Si-O-Si之间键角的连续变化和扭曲，导致了石英光纤材料远程无序的结构特征。在石英光纤材料的无规则网格结构中分布着(Si-O)n拓扑环状结构，有三环、四环至十环或杂环结构存在，其中以三、四、六环或七环占多数。在石英光纤材料结构中，如果出现偏离上述由Si-O-Si构成的理想的无规则网格结构时，就会形成点缺陷结构。高纯石英光纤材料中常见的点缺陷结构主要有缺氧型缺陷和富氧型缺陷。缺氧型缺陷包括E’色心、Si-Si键等；富氧型缺陷包括非桥氧缺陷(NBOHC)、过氧自由基和过氧链接。2) The main intrinsic defects in quartz materials have absorption and emission characteristics both in the material and on the surface of the material. The more common defects such as oxygen defect centers and non-bridging oxygen vacancy centers have absorption and emission characteristics, and even the same type of defects , there are also subtle differences in the properties of the material surface and the material body. It can be seen that structural defects have a great influence on the optical properties of quartz materials, and this effect may often be caused by the coexistence of multiple defects. In theory, quartz glass should be a complete Si-O network tetrahedron, each Si atom is connected with four O atoms, and each O atom is connected with two Si atoms, thus forming a three-dimensional silicon-oxygen tetrahedron . The structure has several key parameters, including the bond length d(Si-O), which averages about approx.

Tetrahedral angle

The average bond angle is about 109°; the inter-tetrahedral angle α(Si-O-Si), the average bond angle is about 144°-150°, and the distribution range is 120° to 180°; it also includes bond torsion angles δ1 and δ2, etc., positive It is because of the continuous change and twist of the bond angle between Si-O-Si, which leads to the structural characteristics of long-range disorder in the silica fiber material. There are (Si-O)n topological ring structures distributed in the random grid structure of silica fiber materials, and there are three-ring, four-ring to ten-ring or heterocyclic structures, among which three, four, six or seven rings exist. Majority. In the structure of the silica fiber material, if there is a deviation from the ideal random grid structure composed of Si-O-Si, a point defect structure will be formed. The common point defect structures in high-purity silica fiber materials mainly include oxygen-deficient defects and oxygen-rich defects. The oxygen-deficient defects include E' color centers, Si-Si bonds, etc.; the oxygen-rich defects include non-bridging oxygen defects (NBOHC), peroxy radicals and peroxy linkages.

In view of this, it is necessary to provide a method for producing photomasks for semiconductors, so as to prepare synthetic quartz products with high ultraviolet transmittance and high optical uniformity.

SUMMARY OF THE INVENTION

Therefore, the present invention provides a method for producing a synthetic quartz material for a semiconductor mask. The method has high production process continuity, and the synthetic quartz product T _{170-193 nm} ≥95%.

In order to solve the above-mentioned technical problems, the present invention provides a method for producing a synthetic quartz material for a semiconductor mask, comprising the following steps:

(1) In the deposition chamber, the silicon source is deposited on the lead rod by the vapor-phase axial deposition method to obtain a low-density _SiO2 soot; wherein, the silicon source undergoes a chemical reaction in the oxyhydrogen flame of combustion to form dioxide Silicon particles are deposited to form low-density SiO ₂ loose bodies; during the deposition process, the deposition chamber is controlled to be in a negative pressure environment, and the temperature is not higher than 500°C;

(2) Transfer the low-density SiO ₂ soot to a sintering furnace, and in a closed environment filled with dehydroxylation gas flow and oxygen, the temperature is raised to 1100-1300° C. to dehydrate the low-density SiO ₂ soot;

(3) In an inert gas environment, a fluorine-containing gas is introduced into the sintering furnace, and heated to 1400-1600 ° C, so that the low-density SiO ₂ loose body is vitrified to form transparent quartz glass; During the process, the low-density SiO ₂ loose body keeps vertical motion, and the temperature gradient between the longitudinal and radial directions in the deposition chamber is ≤ 2°C;

(4) annealing the transparent quartz glass obtained in step (3) to obtain the synthetic quartz material for producing the semiconductor mask.

Further: in step (1), the silicon source is SiCl ₄ with a purity of more than 99.9999%, the purity of the hydrogen and oxygen supplied is more than 99.999%, and the inner wall of the deposition cavity is lined with high-purity quartz.

Further: in step (1), the rotating speed of the low-density SiO ₂ soot body is controlled by the motor to be 20-50 rpm/min, and the lifting speed is 0.4-1.2 mm/min.

Further: in step (1), in the obtained low-density SiO ₂ soot body, the content of metal impurities is less than or equal to 10ppb.

Further: in step (2), the dehydroxylation gas stream includes an inert gas and a chlorine-based desiccant.

Further: in step (2), the inert gas includes helium or argon, the chlorine-based desiccant includes chlorine, and the flow rate of the oxygen is 0.5-2 L/min.

Further: in step (3), the fluorine-containing gas includes one or more of CF ₄ , C ₂ F ₆ , and C ₃ F ₈ .

Further: in step (3), 2 to 4 layers of heating elements are arranged outside the furnace wall of the sintering furnace, and 6 to 14 thermocouples are evenly and symmetrically distributed. The thermocouple monitors the temperature of different areas in the sintering furnace, and feeds it back to the PLC system, and then adjusts the heating power of different heating elements according to the feedback temperature data to ensure that the longitudinal and radial temperature gradients in the sintering furnace are ≤2°C.

Further: in step (3), in the obtained transparent quartz glass, the content of metal impurities is less than or equal to 8ppb.

Further: in step (4), the optical uniformity of the obtained quartz material reaches 1.2×10 ^-6 , the transmittance level of the outer pass rate is greater than or equal to 90.5% (5mm), and the level of the inner pass rate is greater than or equal to 99.5%.

The above-mentioned technical scheme of the present invention has the following advantages compared with the prior art:

1. Usually, the vitrification of the indirect synthetic quartz needs to use the regional sintering technology. The porous soot body is sintered and densified by the resistance furnace area, so as to become a transparent glass preform without bubbles. Since the sintering process is a regional sintering process, the soot body is During the vitrification process, the stress of the quartz glass is too large due to the longitudinal movement and the longitudinal temperature difference. The method for synthesizing quartz material provided by the present invention adopts a sintering furnace equipped with multi-layer heating elements, which can ensure that the soot body has no longitudinal position movement during the process of dehydration, doping, vitrification and annealing, thereby ensuring that the soot body is in the vitrification process. There is no influence of mechanical longitudinal motion; at the same time, the temperature feedback of multiple thermocouples and PLC control system ensure that the temperature field in the furnace is highly stable during the process of dehydration, doping, vitrification and annealing of the soot, and there is no temperature gradient caused by lifting to the glass. The influence of the stress, thereby improving the optical uniformity of synthetic quartz, the synthetic quartz glass produced by this device has a diameter of 120, and the optical uniformity reaches 1.2×10 ^-6 .

2. The production of the silica soot is mainly by the flame hydrolysis reaction of the halide feedstock (SiCl ₄ ) from the gas supply system to generate fine glass particles, which are then deposited on the growth surface to form the porous soot. During the deposition production process, due to the high deposition temperature, most of the H ₂ O and HCl produced by the reaction and the residual glass particles that have not been deposited on the surface will be discharged from the exhaust gas exhaust port located near the deposition area. However, due to the high reaction temperature, a part of H ₂ O and HCl will diffuse into the inner wall of the deposition metal chamber, causing corrosion to the chamber, and depositing on the quartz material, causing pollution to the deposited loose body. The invention realizes the high purity of the loose body by using high-purity raw materials and gases, using corrosion-resistant materials for the deposition chamber, and using deposition process protection technologies such as high-purity quartz linings. The metal impurity content of the soot body treated by the invention is significantly reduced, and the metal impurity content can be controlled to be less than or equal to 10ppb.

3. Porous porosity is generally densified by sintering in the resistance furnace area, which mainly includes two steps: 1) The densification of porous glass increases, and the transition from open pores to closed pores occurs during this process; 2) The shrinkage of closed pores disappears . After these two processes, the loose body thus becomes a bubble-free synthetic quartz glass. During the densification process of the loose body, the internal temperature field of the resistance is generally controlled above 1500°C. In the present invention, a certain concentration of fluorine-containing gas is introduced during the sintering process to generate gaseous metal halide, chlorine and metal oxides under high temperature conditions. The highest boiling point of the compound is 1500 ℃, and the halide can be removed by sintering, so as to realize the purification of synthetic quartz glass. The metal impurity content of the synthetic quartz glass treated by the invention is significantly reduced, and the metal impurity content can be controlled to be less than or equal to 8ppb.

4. The structural defects of quartz glass are the defects of the [SiO ₄ ] tetrahedral network structure itself, including oxygen-deficient defects (≡Si, ≡Si-Si≡) and peroxidative defects (≡Si-O·, ≡Si-OO ·, ≡Si-OO-Si≡). The VAD sintering atmosphere of the present invention can be an inert atmosphere and an oxidizing atmosphere. An oxidizing atmosphere can easily create an oxygen-enriched environment, resulting in oxygen-enriched defects. The invention repairs the formed E' defects and NBOHC defects through fluorine doping, and at the same time, it has low requirements on the density of the loose body, and does not need to adjust the process parameters correspondingly for the loose bodies of different densities. The pass rate level is obviously optimized, the transmittance outer pass rate level is ≥90.5% (5mm), and the inner pass rate level is ≥99.5%.

5. The process of the present invention has good repeatability, and the synthetic quartz produced is large in size and high in quality. By introducing fluorine groups in the densification stage and controlling the concentration, flow rate and gas partial pressure of the fluoride entering the sintering device, the synthetic quartz can be realized. The uniformity of the radial refractive index of the glass is ≤5ppm, and the purity of the synthetic quartz material produced is relatively high. After slicing → polishing → testing, the product is 120 caliber, and the optical uniformity reaches 1.2 × 10 ^-6 .

Description of drawings

Fig. 1 is the process flow diagram of the present invention;

2 is a schematic structural diagram of a deposition apparatus of the present invention;

Fig. 3 is the structural schematic diagram of the sintering device of the present invention;

Fig. 4 is the transmittance comparison diagram of synthetic quartz glass (A) prepared by the present invention and conventional synthetic quartz (B);

Fig. 5 is the refractive index curve diagram of synthetic quartz glass prepared by the present invention;

Among them, 1, lead rod; 2, deposition chamber; 3, high efficiency filter; 4, silicon source combustion device; 5, valve; 6, distribution system; 7, feed pipe; 8, SiCl ₄ raw material; 9, exhaust air Device; 10. Exhaust gas discharge pipe; 11. Valve; 12. Low density SiO ₂ loose body; 13. Sintering furnace; 14. Outlet of furnace core; 15. Transparent quartz glass; 16. Heating element; 17. Furnace core Air inlet at the bottom of the tube; 18. Thermocouple.

Detailed ways

The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

Referring to FIG. 1, the present invention provides a method for producing a synthetic quartz material for a semiconductor mask, including four main processes: deposition of soot, dehydration of soot, vitrification and introduction of fluorine bases, and annealing in a furnace. The deposition process (VAD) first deposits to form a low-density _SiO2 soot body 12, and then sinters; the sintering process performs dehydration, dehydroxylation, degassing and densification until vitrification is achieved; after the sintering is completed, the obtained quartz glass is annealed , so as to fully release the stress inside the quartz glass to ensure its uniformity, and finally obtain the finished quartz glass 26 after annealing, that is, a high-quality high-purity, high-uniformity, low-hydroxyl quartz glass. Each step is described in detail below.

1. Loose body deposition

Referring to FIG. 2 , the deposition of the low-density SiO ₂ soot body 12 is carried out in the deposition chamber 2 . In the deposition chamber 2 , a silicon source is deposited on the lead pin 1 by a VAD process to obtain the low-density SiO ₂ soot body 12 . Among them, the silicon source, namely the SiCl ₄ raw material 8, enters the distribution system 6 through the carrier gas, and then enters the silicon source combustion device 4 through the valve 5 and the mass flow controller. At the same time, the purified Ar, H ₂ and O ₂ enter the distribution system 6 through the metal pipeline, and then enter the silicon source combustion device 4 through the metal pipeline. The SiCl ₄ raw material 8 undergoes a chemical reaction in the burning hydrogen-oxygen flame to form silicon dioxide particles, which are deposited on the lead rod 1 in the deposition chamber 2 to obtain a low-density SiO ₂ loose body 12 . The distribution system 6 is a gas flow controller, which is used to control the size of different gas flows. In the present invention, the purity of the SiCl ₄ raw material 8 is preferably more than 99.9999%, and the hydrogen and oxygen are preferably high-purity gases with a purity of more than 99.999%, thereby helping to improve the purity of the finished quartz glass. As a protective gas, Ar acts as a physical isolation in the burner to avoid damage to the burner.

The flow rate of each of the above-mentioned raw material gases can be set by those skilled in the art as required, or the flow rate of the prior art can be adopted. The flow rate of the SiCl ₄ raw material 8 may be 80-120 g/min, preferably 80 g/min in this embodiment; the flow rates of H ₂ , O ₂ and Ar may be 110-130 L/min, 70-90 L/min and 15- 17L/min, preferably 120L/min, 80L/min, 16L/min in this embodiment.

In the present invention, in order to ensure the stability of the airflow in the deposition chamber 2 to ensure stable deposition, a high-efficiency filter 3 and an air extraction device 9 are respectively provided on the side wall of the deposition chamber 2, and the height of the air extraction device 9 is slightly lower than HEPA filter location. Through the high efficiency filter 3 and the air extraction device 9, the height of the air extraction device 9 is slightly lower than the position of the high efficiency filter 3. The deposition chamber 2 has a slight negative pressure, preferably 50-150 Pa lower than the standard atmospheric pressure, thereby ensuring stable airflow in the deposition chamber 2, not easy to introduce impurities, and effectively reducing the introduction of external impurities into the loose body. Preferably, a pressure gauge is provided at the exhaust port so that pressure can be monitored and dynamic pressure regulation can be performed. Through the dynamic control of the pressure, the airflow in the deposition chamber 2 is guaranteed to be stable, so that impurities are not easily introduced. Preferably, a temperature sensor is provided in the deposition chamber 2 to monitor and ensure that the temperature in the deposition chamber 2 is not higher than 500° C. to reduce the introduction of metal impurities.

In the present invention, a lead rod 1 to be deposited is suspended in the deposition chamber 2, and a driving device is provided on the deposition chamber 2. In this embodiment, the driving device is a motor. The motor can drive the lead rod 1 to lift and rotate, so as to improve the uniformity of soot deposition. The rotational speed of the motor is 20 to 50 rpm/min, preferably 30 rpm/min. In order to improve the uniformity of the quartz glass, the rotation speed of the motor can be appropriately increased. The lifting speed of the motor is 0.4-1.2mm/min, preferably 0.8mm/min, to ensure the diameter of the loose body. A waste gas discharge pipe 10 is arranged on the side wall of the deposition chamber 2 , and the waste gas generated in the deposition chamber 2 is discharged through the waste gas discharge pipe 10 , and a valve 11 is provided on the waste gas discharge pipe 10 .

2. Loose body dehydration

Referring to FIG. 3 , the low-density SiO ₂ soot body 12 is transferred to the sintering furnace 13 , and Cl ₂ or other chlorine-based desiccant and inert gas are introduced into the sintering furnace 13 through the inlet of the furnace core tube, and the The provided heating element 16 heats the low-density SiO ₂ soot body 12 to a high temperature of 1100-1300° C. Through physical and chemical action, the hydroxyl, moisture and other components in the low-density SiO ₂ soot body 12 are removed, and then pass through the furnace core. The nozzle outlet 14 is discharged out of the sintering furnace 13 . In the present invention, in order to ensure the stability and uniformity of the temperature field of the loose body, multiple layers (2 to 4) heating elements are set on the outer wall of the sintering furnace, and a plurality of identical heating elements are evenly and symmetrically distributed in the effective temperature field area of the furnace core tube. There are 18 (6 to 14) thermocouples of different models (the thermocouple model is B type), and they are respectively connected to the PLC system, and the heating power of different heating elements is adjusted respectively through the monitoring temperature of the thermocouple, thus ensuring the longitudinal direction of the furnace core tube. and radial temperature gradient ≤ 2 ℃. Therefore, in the dehydration and vitrification stages, the soot body does not need to move longitudinally, thereby avoiding the influence of the stress on the glass due to the temperature gradient during lifting, and improving the optical uniformity of the synthetic quartz. In order to further ensure the optical uniformity of the quartz material, a certain flow of O ₂ was introduced simultaneously during the dehydration and dehydroxylation process, and the amount of O ₂ was controlled at 0.5-2L/min, preferably 1L/min, to improve the Optical uniformity of the product.

3. Vitrification and introduction of fluorine groups

After the dehydration of the low-density SiO ₂ loose body 12 is completed, it is placed in an inert gas environment of helium or argon gas and heated to 1400-1600° C. Under this condition, the loose body is vitrified to form transparent quartz glass 23 . Obviously, in the process of dehydration and sintering of the soot body, the soot body must be placed in a closed environment to provide a corresponding atmosphere for its dehydration and complete transparency, and at the same time prevent foreign impurities from entering it. In the present invention, during the densification process of the soot body, a certain flow of fluorine-containing gas, such as CF ₄ , C ₂ F ₆ , C ₃ F ₈ , etc., is introduced, preferably CF ₄ . Under high temperature conditions, the fluorine-containing gas can be It forms gaseous metal halides with metal oxides, and the highest boiling point of the halides is 1500 ° C. The halides can be removed by sintering, thereby realizing the purification of synthetic quartz glass. The metal impurity content of the synthetic quartz glass treated in this step is significantly reduced, and the metal impurity content can be controlled to be less than or equal to 8ppb.

4. Furnace annealing

After the transparent quartz glass 15 is sintered, it is finely annealed using a precision annealing device to eliminate the residual permanent stress and at the same time meet the requirements of high uniformity. Obviously, the annealing process is divided into four stages: heating stage, holding stage, slow cooling stage and fast cooling stage.

FIG. 4 is a comparison diagram of the transmittance of synthetic quartz glass prepared by the present invention and conventional synthetic quartz, and FIG. 5 is a refractive index curve of the synthetic quartz glass prepared by the present invention.

It can be seen from the figure that the annealed quartz glass finally obtained by the present invention has an optical uniformity of 1.2 × 10 ^-6 when the product diameter is 120 mm, the transmittance of the outer pass rate level is ≥90.5% (5mm), and the inner pass rate level ≥ 99.5%.

Obviously, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation manner. For those of ordinary skill in the art, other different forms of changes or modifications can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. And the obvious changes or changes derived from this are still within the protection scope of the present invention.

Claims (9)

1. a method for producing synthetic quartz material for semiconductor mask, is characterized in that: comprise the following steps: (1) In the deposition chamber, the silicon source is deposited on the lead rod by the vapor-phase axial deposition method to obtain a low-density _SiO2 soot; wherein, the silicon source undergoes a chemical reaction in the oxyhydrogen flame of combustion to form dioxide Silicon particles are deposited to form low-density SiO ₂ loose bodies; during the deposition process, the deposition chamber is controlled to be in a negative pressure environment, and the temperature is not higher than 500°C; (2) Transfer the low-density SiO ₂ soot to a sintering furnace, and in a closed environment filled with dehydroxylation gas flow and oxygen, the temperature is raised to 1100-1300° C. to dehydrate the low-density SiO ₂ soot; (3) In an inert gas environment, a fluorine-containing gas is introduced into the sintering furnace, and heated to 1400-1600 ° C, so that the low-density SiO ₂ loose body is vitrified to form transparent quartz glass; During the process, the low-density SiO ₂ loose body keeps vertical motion, and the temperature gradient between the longitudinal and radial directions in the deposition chamber is ≤ 2°C; (4) annealing the transparent quartz glass obtained in step (3) to obtain the synthetic quartz material for producing a semiconductor mask. 2 . The method for producing a synthetic quartz material for a semiconductor mask according to claim 1 , wherein in step (1), the silicon source is SiCl ₄ with a purity of more than 99.9999%, and the introduced hydrogen The purity of oxygen and oxygen is over 99.999%, and the inner wall of the deposition chamber is lined with high-purity quartz. 3. The method for producing a synthetic quartz material for a semiconductor mask plate according to claim 1, wherein in step (1), the rotational speed of the low-density _SiO2 soot body is controlled by a motor to be 20 to 50rpm/min , the lifting speed is 0.4 ~ 1.2mm/min. 4 . The method for producing a synthetic quartz material for a semiconductor mask according to claim 2 , wherein in the step (1), in the obtained low-density SiO ₂ soot, the content of metal impurities is less than or equal to 10ppb. 5 . 5 . The method for producing a synthetic quartz material for a semiconductor mask according to claim 1 , wherein in step (2), the dehydroxylation gas stream includes an inert gas and a chlorine-based desiccant. 6 . 6. The method for producing a synthetic quartz material for a semiconductor mask according to claim 5, wherein in step (2), the inert gas comprises helium or argon, and the chlorine-based desiccant comprises Chlorine; the flow rate of the oxygen is 0.5-2L/min. 7 . The method for producing a synthetic quartz material for a semiconductor mask according to claim 1 , wherein in step (3), the fluorine-containing gas comprises CF ₄ , C ₂ F ₆ , and C ₃ F ₈ . one or more of. 8. The method for producing a synthetic quartz material for a semiconductor mask according to claim 1, wherein in step (3), 2 to 4 layers of heating elements are arranged outside the furnace wall of the sintering furnace, and There are 6 to 14 thermocouples evenly and symmetrically distributed. The thermocouples are respectively connected to the PLC system. The temperature of different areas in the sintering furnace is monitored through the thermocouples, and fed back to the PLC system, and then adjusted according to the feedback temperature data. The heating power of different heating elements ensures that the temperature gradient between the longitudinal and radial directions in the sintering furnace is less than or equal to 2 °C. 9 . The method for producing a synthetic quartz material for a semiconductor mask according to claim 1 , wherein in step (3), in the obtained transparent quartz glass, the content of metal impurities is less than or equal to 8ppb. 10 .

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