KR20080097260A - Method for controlling oh content in a quartz glass - Google Patents

Abstract

A method for controlling OH content in a quartz glass is provided to improve a heat resistance of quartz glass used for dust-proof glass for projection typed display unit or a high temperature poly silicon-TFT substrate and an opposing board by heat-treating silica in the halogen gas mood at the quartz glass manufacturing process and controlling the OH group. An OH group within quartz glass is removed at a condition of over a halogen use gas Cl2 having a gas density of 200cc/min or more, a thermal annealing temperature of 950°C or high and a thermal processing annealing time of 10 hours or more. A remained halogen is removed at a condition of H2 as a halogen removal gas having a gas density of 200cc/min or more, a thermal annealing temperature of 950°C or high and a thermal processing annealing time of 10 hours or more. The OH group within quartz glass is heat-treated so that a virtual temperature is 1050°C or less. Uniform contents of the OH and the halogen are maintained.

Description

Method for controlling OH content in quartz glass {Method for controlling OH content in a quartz glass}

Figure 1 shows the viscosity change according to the OH content for the case where the viscosity measurement temperature is 1100, 1200, 1300 ℃, respectively.

Figure 2 shows the results of measuring the coefficient of thermal expansion of the sample of OH content of 18, 87, 174ppm, respectively.

3 is a flowchart illustrating a process of manufacturing a dustproof glass or a high temperature polysilicon TFT substrate and a counter substrate for a projection display device.

Figure 4 shows the measuring point for the OH concentration distribution control on the quartz glass.

5 is a graph showing UV transmittance when halogen component remains on quartz glass.

Figure 6 is a graph showing the UV transmittance after removing the halogen component on the quartz glass.

7 is a graph measuring the effect of the halogen gas type on the OH content (halogen gas concentration: 300cc / min, heat treatment temperature: 1000 ℃, heat treatment time 20hr).

8 is a graph measuring the effect of the halogen gas concentration on the OH content (halogen gas: Cl ₂ , heat treatment temperature: 1000 ° C., heat treatment time 20 hr).

9 is a graph measuring the effect of the halogen gas heat treatment temperature on the OH content (halogen gas: Cl ₂ , concentration: 300 cc / min, heat treatment time: 20 hr).

10 is a graph measuring the effect of the halogen gas heat treatment time on the OH content (halogen gas: Cl ₂ , concentration: 300 cc / min, heat treatment temperature: 1000 ° C).

11 is a graph measuring the OH content according to the type of halogen removal gas (halogen removal gas concentration: 300cc / min, heat treatment temperature: 1000 ℃, heat treatment time 20hr).

12 is a graph measuring the change in OH content according to the change in the concentration of halogen removal gas (halogen removal gas: H ₂ , heat treatment temperature: 1000 ℃, heat treatment time 20hr).

Figure 13 is a graph measuring the change in OH content according to the change in the heat treatment temperature of halogen removal gas (halogen removal gas: H ₂ , concentration: 300cc / min, heat treatment time: 20hr).

14 is a graph measuring the change in OH content according to the change in the heat treatment time of halogen removal gas (halogen removal gas: H ₂ , concentration: 300cc / min, heat treatment temperature: 1000 ℃).

15 is a graph showing the change in OH content before and after the halogen component removal heat treatment.

Fig. 16 is a graph showing the OH concentration distribution before and after the slow cooling heat treatment.

17 is a graph showing the distribution of halogen content before and after the slow cooling heat treatment.

The present invention relates to a method for manufacturing high heat resistant quartz glass, and more particularly, to heat-proof silica in a halogen gas atmosphere during quartz glass manufacturing process to improve heat resistance of dustproof glass or high temperature polysilicon TFT substrate and counter substrate used in projection display device. It relates to a method for controlling the OH group.

High-purity quartz glass is made of SiO ₂ only and has high chemical stability because it is a high-purity glass with very low content of other metal impurities. It has excellent light transmittance, especially in the ultraviolet region. It is applied to display industry parts including photomask substrate for substrate and wafer for high temperature poly-Si TFT-LCD which is a core part of projection display, and is used for precision optical materials (UV grade lens, prism, mirror, filter, etc.), It is also used as a variety of equipment related to semiconductor / LCD manufacturing (baths, chambers, boats), and is also widely used in high-tech industries such as the display industry and the semiconductor industry.

In addition, quartz glass having excellent transmittance in the ultraviolet region is synthetic silica glass that strictly controls the purity of metal impurities in the manufacturing method, and synthetic quartz glass is an OH group (hydroxyl group) inside the quartz glass due to the nature of the manufacturing method. It contains a lot of). Since OH existing inside the glass breaks the [SiO ₄ ] tetrahedron network structure, it causes a decrease in heat resistance, which is one of the excellent properties of quartz glass.

The level of quartz glass industry used in display industry and semiconductor industry in Korea is processed low-purity quartz glass which is used as transportation tool, container and vacuum chamber in semiconductor manufacturing process. High purity quartz glass, such as quartz glass substrates for photomasks and quartz glass for precision optics, is imported and used as a finished product.

Considering the manufacturing status of quartz glass in Japan and the United States, which are leading technologies in the manufacturing of synthetic quartz glass, quartz glass was originally manufactured by melting quartz at a high temperature of 2000 ° C or higher. However, as the industry develops, its use and requirements are diversified. As they become more stringent, several manufacturing methods have been developed. The two types of quartz glass can be broadly classified into molten quartz glass manufactured by melting powder of natural crystal and synthetic quartz glass manufactured by chemical synthesis. Accordingly, there are an electric melting method, a plasma melting method, an oxyhydrogen salt melting method, and a method of manufacturing synthetic quartz glass includes a direct method, a chemical vapor deposition method, a sol-gel method, and the like.

Since the electrofusion method is a method of melting the crystal powder with electricity, almost no moisture is contained in the quartz glass. The plasma melting method uses a plasma torch instead of an oxyhydrogen burner. Like the electrofusion method, it contains almost no OH group. Oxyhydrogen flame melting method is a method using a flame using a reaction of oxygen and hydrogen. When oxygen and hydrogen react, water is generated. At this time, a large amount of energy is generated to become a high temperature. This heat is used to melt the crystal powder. Because of the reaction between oxygen and hydrogen, quartz crystals are melted and a large amount of moisture is generated, which causes many defects in quartz glass. As a characteristic of molten quartz glass, it is heat resistant, but there are relatively many disadvantages of metal impurities.

There are many methods for producing synthetic quartz glass, but most of them are synthesized by reacting (hydrolysis) silicon tetrachloride (SiCl ₄ ) with water molecules produced by the reaction of oxygen and hydrogen in a burner that burns oxygen and hydrogen. At this time, since the compound with few impurities is used as a starting material, very high purity quartz glass is made. Molten quartz glass contains a metallic impurity in the crystal powder as a raw material and thus has a limited purity. Therefore, when high purity is required, chemically synthesized quartz glass is used. Direct synthetic quartz glass is made by hydrolyzing silicon tetrachloride in a hot oxyhydrogen flame. Since quartz glass synthesized by the direct method is synthesized in an oxyhydrogen flame, OH remains. The amount of OH is about 10 times higher than that of molten quartz glass melted in an oxyhydrogen flame. In addition, since silicon tetrachloride (SiCl ₄ ) is used as a raw material, Cl is contained and is more easily deformed than molten quartz glass at a high temperature.

Chemical Vapor Deposition Synthetic quartz glass is prepared by heat treatment after preparing agglomerates made of fine particles of silica. VAD (Vapor-phase Axial Deposition) method, one of the typical manufacturing methods, was devised and put into practice in Japan. First, porous silica agglomerates were synthesized at a temperature of about 1100 ° C. lower than the direct method, and then sintered to about 1500 ° C. It is a method of making transparent quartz glass. This quartz glass is characterized by a very small amount of metal impurities compared to molten quartz glass.

The plasma method is a method for producing quartz glass containing no OH. This is also a direct method of synthesizing quartz glass, but instead of oxyhydrogen flames, silicon tetrachloride and oxygen are reacted using induction plasma such as argon (Ar) or oxygen (O ₂ ). This quartz glass has a disadvantage of being weak in radiation or ultraviolet rays due to residual oxygen or chlorine. The sol-gel method is a method of synthesizing a porous body in a solution, drying it, and heating and vitrifying. Research has been carried out in the hopes of several researchers because the glass can be manufactured with high efficiency (yield) by drying the solution to form a rough form and heat treatment.

Projection-type display devices include liquid crystal projectors and projection TVs, which are rapidly increasing in demand, and are expected to continue to grow in the future. Quartz glass for projection display is applied to dustproof glass, high temperature poly-Si TFT-LCD substrate, color filter substrate, etc., and the quality level is higher in order of dustproof glass, color filter substrate, TFT-LCD substrate. However, even in Korea, even the lowest quality dust-proof glass relies on imports, and if it cannot be localized, technology dependency is concerned.

Dust Proof Glass is located on the front and back of the high-temperature poly-Si TFT-LCD substrate and the color filter substrate to prevent deterioration of image quality caused by dust or foreign matter adhering to the substrate surface. In addition, it has a function of preventing mechanical damage to the substrate glass.

In addition, since the projection display device uses a halogen lamp as a light source, high heat is generated. Therefore, when the heat resistance of the quartz glass is different, the adhesion decreases due to the difference in the thermal expansion coefficient of the substrate / dustproof glass, leading to deterioration of image quality. do. Therefore, it is necessary to develop dust-proof glass at the same level as the coefficient of thermal expansion of the quartz glass for substrate. To this end, it is necessary to control the concentration of OH groups in the quartz glass that have the greatest influence on the coefficient of thermal expansion, thereby improving heat resistance. .

Since the research and development of quartz glass in Japanese manufacturing companies that dominate the world market is not disclosed at all except patents, the trend of heat resistance enhancement technology was investigated in the JPO data. Shown in

Table 1 summarizes the patent literature related to the heat resistance improvement of Sumitomo metal.

Application number Applicant Contents JP2002-160936 住友 金屬 Heat treatment at high temperature with oxygen gas reduced to 100 Pa to reduce OH concentration to 80 ppm JP2002-053338 住友 金屬 It is reduced to 12ppm by heat treatment at high temperature with He gas reduced to 20Pa. JP2002-087833 住友 金屬 Reduced to 18ppm by heat treatment at high temperature under ultra low pressure of 2 * 10E4 Pa JP1999-228160 住友 金屬 Reduced to 50ppm by heat treatment at high temperature under reduced pressure of 1-3Pa

Table 2 summarizes the contents of patent documents related to improving heat resistance of Asahi Glass.

Application number Applicant Contents JP2002-316123 Asahi Glass Heat treatment at 1200 ℃ with oxygen gas reduced to 0.1 atm to reduce OH concentration to 18 ppm JP2002-318049 Asahi Glass He gas reduced to 0.1 atm, and reduced to 9.4 ppm by heat treatment at 1250 ° C. JP2001-180962 Asahi Glass Heat treatment at high temperature in ultra low pressure at 0.1 Torr and drop to 7.8 ppm JP2000-239031 Asahi Glass Heat reduced at 4.2ppm after depressurizing to 1Torr

As can be seen from the table, a Japanese manufacturer is investigating that the concentration of OH is reduced by heat treatment under reduced pressure, and recently, a patent for heat treatment in a SiF ₄ gas atmosphere is also disclosed. However, the heat treatment in the SiF ₄ gas atmosphere is for the purpose of presenting fluorine (F) in the quartz glass in addition to the purpose of lowering the OH, and the fluorine-containing quartz glass is a product for use in optical fibers. In addition, fluorine serves to break the network structure in the quartz glass to lower the heat resistance. The present applicant has also obtained a domestic patent for a technology for removing OH from quartz glass by rapid heat treatment under reduced pressure, and is currently under international patent application (PCT). However, the removal of OH under reduced pressure requires a relatively long time, so the industrial utility is inferior, and thus, more efficient technology development is required.

Since the halogen gas may be present in the quartz glass like the fluorine-containing quartz glass, the method using the halogen gas further requires a step of removing the halogen, resulting in an increase in the concentration of OH. However, since the distribution of concentrations is important, as well as the decrease in OH concentration, the OH concentration and distribution can be controlled by appropriately adjusting the OH removal process and the OH production process.

Therefore, it is an object of the present invention to provide a method for producing high heat-resistant quartz glass with excellent productivity while lowering production cost through process optimization.

In order to achieve the above object, the present inventors performed a halogen gas atmosphere heat treatment experiment for removing OH in silica using a strong OH adsorption force of halogen gas. Experimental variables for OH removal and concentration distribution control test by halogen gas atmosphere heat treatment were set as halogen gas type, halogen gas concentration, heat treatment temperature and heat treatment time. Halogen gas type was Cl ₂ , HCl, Cl ₂ / HCl mixed gas, halogen gas concentration of 35 ~ 1000cc / min, heat treatment temperature was 800 ~ 1100 ℃, heat treatment time was 1 ~ 40hr.

The halogen component remaining in the silica after the heat treatment of the halogen gas atmosphere adversely affects the optical properties of the glass, so it must be removed again so that the halogen component remains. Experimental variables for the halogen removal test were set by the type of gas used, concentration of gas used, heat treatment temperature, heat treatment time, and the like. The type of halogen removal gas was H ₂ , O ₂ , the gas concentration was 35 to 1000 cc / min, the heat treatment temperature was 800 to 1100 ° C., and the heat treatment time was 1 to 40 hours.

The present invention removes OH groups in the quartz glass with a halogen using gas Cl ₂ , a gas concentration of 200 cc / min or more, a heat treatment temperature of 950 ° C. or more, and a heat treatment time of 10 hours or more;

Residual halogen is removed as H ₂ , a gas concentration of 200 cc / min or more, a heat treatment temperature of 950 ° C. or more and a heat treatment time of 10 hours or more as the halogen removing gas;

Slow cooling to a virtual temperature of 1050 ° C. or lower;

A method of controlling the OH content in a quartz glass characterized by having a uniform OH and halogen content.

In addition, the present invention is characterized in that the gas concentration at the time of OH removal is 200 ~ 1000cc / min.

In addition, the present invention is characterized in that the heat treatment temperature at the time of OH removal is 950 ~ 1,100 ℃.

In addition, the present invention is characterized in that the heat treatment time during OH removal is 10 to 40 hours.

In addition, the present invention is characterized in that the gas concentration at the time of halogen removal is 200 ~ 1000cc / min.

In addition, the present invention is characterized in that the heat treatment temperature at the time of halogen removal is 950 ~ 1,100 ℃.

In addition, the present invention is characterized in that the heat treatment time during halogen removal is 10 to 40 hours.

In addition, the present invention is characterized in that the slow cooling heat treatment to the virtual temperature 950 ~ 1050 ℃ after the halogen removal heat treatment.

The condition range is the most suitable range for lowering the OH concentration of the quartz glass.

The method of removing the OH group of the quartz glass using a halogen gas can be represented by the following chemical reaction formula.

-Si-OH + HO-Si- + M 2 → -Si-OM + M-Si + H 2 O (g)

Experimental variables for the halogen gas atmosphere heat treatment test for removing OH in the quartz glass were set by halogen gas type, gas concentration, heat treatment temperature, heat treatment time, and the like.

In addition, in order to remove the halogen gas, a halogen gas removal heat treatment was performed using a non-halogen gas, and as the experimental variables, gas type, gas concentration, heat treatment temperature, and heat treatment time were set.

Thereafter, a slow cooling treatment was performed to uniformly distribute the OH group and the halogen gas, and the experimental variable was assumed to be a virtual temperature.

In order to measure the concentration of OH in the quartz glass, the transmittance was measured at 2600 nm and 2730 nm using FT-IR, and the following formula was obtained.

OH content [ppm] = 910 × (1 / t) log ₁₀ (Ta / Tb)

Where t is the thickness of the sample (mm), Ta is the transmittance (%) at 2600 nm wavelength, and Tb is the transmittance (%) at 2730 nm wavelength. In addition, the constant 910 is calculated by the following equation. MW is 17g at the molecular weight of (OH) ^- , E is 85liters / mol.cm at the extinction coefficient of (OH) ^- , and ρ is 2.21g / cm ^{3 at} the density of SiO ₂ .

910 = (MW × 10 ⁴ ) / (E × ρ)

* Viscosity evaluation

Unlike ordinary glass, quartz glass has high melting point and high temperature viscosity, making it difficult to measure viscosity at high temperature. Viscosity measurement methods include beam bending method, cantilever beam bending method, torsion method, and falling ball method. The beam bending method and the cantilever beam method can measure the viscosity of 10 ⁹ ~ 10 ¹⁶ Pa.s at 1100 ~ 1500 ℃, and the Torsion method can measure the viscosity of 10 ⁵ ~ 10 ⁸ Pa · s at 1500 ~ 2200 ℃. , Falling ball method can measure the viscosity of more than 10 ⁴ Pa · s above 2300 ℃. Only the beam bending method and the cantilever beam bending method are available for measuring the viscosity to check the heat resistance of quartz glass used at high temperature. Among them, in the present invention, the viscosity of the quartz glass was measured using a cantilever beam bending method which can be easily measured.

The viscosity (η) of the quartz glass can be obtained by the following equation by measuring the deformed length while keeping the measurement at a desired temperature for a certain time.

η = (ρ g L ⁴ Δt) / (2 a ² h)

Where ρ is the glass density, g is the acceleration of the specimen, L is the length of the specimen, Δt is the holding time at the measurement temperature, a is the thickness of the specimen, and h is the deformation of the specimen.

The test for the measurement of the viscosity of the quartz glass was carried out by fixing the holding time to 10 hours at a temperature of 1100 ~ 1300 ℃ using a high-temperature reactor capable of controlling the atmosphere, samples with different OH content produced under each heat treatment condition Was used for the experiment. Figure 1 shows the viscosity change according to the OH content for the case where the viscosity measurement temperature is 1100, 1200, 1300 ℃, respectively.

The viscosity of the quartz glass decreases with increasing OH content. The low viscosity when the OH concentration is high is considered to be because the network structure of the glass is cut at various places by the OH group, and impurities other than OH may affect the viscosity, but in the present invention, a sample having a constant purity is used. The influence of purity was excluded on the assumption that the system was used. In the present invention, by adjusting the parameters of the various experimental conditions, it was possible to produce a quartz glass having an OH content in the range of 20 ~ 200ppm, it was also possible to calculate the viscosity range of the quartz glass according to each OH content.

* Coefficient of thermal expansion

The coefficient of thermal expansion of the quartz glass was measured using a TDA (Thermal Dilatometric Analyzer). The specimen for measuring the coefficient of thermal expansion was produced in the form of a rod 5 mm in diameter x 50 mm in length. The measurement temperature was in the range of room temperature to 500 ° C., and the temperature increase rate was 5 ° C./min. In order to investigate the relationship between the coefficient of thermal expansion and the OH content, specimens of OH content of 18, 87 and 174ppm were selected among the samples obtained above.

Figure 2 shows the results of measuring the coefficient of thermal expansion of the sample of OH content of 18, 87, 174ppm, respectively. In the temperature range up to 500 ℃, when the OH content is 18ppm, the average coefficient of thermal expansion is 0.42x10 ^-6 / K, and when the OH content is 87ppm, the mean coefficient of thermal expansion is 0.45x10 ^-6 / K and 174ppm The mean coefficient of thermal expansion was 0.55x10 ^-6 / K. As the OH content increases, the coefficient of thermal expansion increases.

Anti Dust Glass (ADG) for a projection display is manufactured by the process as shown in FIG. 3. Silica glass ingots are made by vitrification heat treatment after preparing the silica dried body. The quartz glass ingot is cut into a wafer using a wire saw and wrapped to form a quartz glass wafer. A quartz glass abrasive wafer prepared by polishing a wafer is manufactured using a dice saw to produce an antidust glass (mixed with "ADG" in the description and drawings of the invention). On the other hand, in the case of a high temperature polysilicon TFT substrate or a counter substrate, after manufacturing a silica dry body, a quartz glass ingot is made by vitrification heat treatment, and a quartz glass wafer is made by cutting and lapping using a wire saw. It is produced by polishing a wafer.

Since the dust-proof glass is cut from a single wafer and dozens are manufactured, it is also important to control the OH concentration distribution in the wafer form. If the OH content in the wafer has a large deviation depending on the position, a problem occurs because it brings about a deviation of the dustproof glass heat resistance.

Nine points were measured and analyzed as shown in FIG. 4 for OH content distribution analysis. A halogen gas atmosphere for the heat treatment test for OH removing halogen gas Cl _2, halogen gas concentration of 300cc / min, the heat treatment temperature 1000 ℃, the heat treatment time performed in the 20hr conditions, the halogen component relieving the halogen removing gas H _2, halogen remove gas concentration As a result of measuring the OH content at the measurement point of FIG. 4 with respect to a sample carried out at 300 cc / min, a heat treatment temperature of 1000 ° C., and a heat treatment time of 20 hr, a result as in FIG. 16 was obtained. The average value was 87ppm, the maximum value was 99ppm, the minimum value was 75ppm, and the range value was 24ppm.

Slow cooling is required to reduce the variation in OH concentration distribution after OH removal by halogen gas atmosphere heat treatment. It is possible to control the fictive temperature by the slow cooling heat treatment, thereby controlling the OH concentration distribution.

The hypothetical temperature is defined as the temperature of the glass in equilibrium when it is allowed to reach a certain temperature rapidly in a certain state [Ref. A. Q. Tool, J. Am. Ceram. Soc., 29 (1946) 240]. When the glass is heat treated at a constant temperature for a sufficient time, the virtual temperature of the glass approaches that temperature. The virtual temperature of the heat-treated and quenched glass at a constant temperature for a long enough time to reach the quasi-equilibrium state is that temperature. If it is cooled without quenching, the virtual temperature of the glass changes according to the cooling rate. Virtual temperature can be an excellent tool in evaluating slow cooling processes to remove residual stress and produce homogeneous glass. In general glass, the virtual temperature can be measured by DSC (Differential Scanning Calorimetry). In the case of quartz glass, the virtual temperature cannot be measured by DSC because there is very little specific heat change before and after the glass transition temperature. The virtual temperature of quartz glass was measured by IR spectroscopic method (Anand Agrwal, Kenneth M. Davis, Minoru Tomozawa, Journal of Non-Crystalline Solids 185 (1995) 191-198).

The inventors conducted a halogen gas atmosphere heat treatment experiment to remove OH groups in the quartz glass. Experiments were performed to find the optimum conditions by varying the gas used, heat treatment temperature, and heat treatment time. In addition, heat treatment experiments were conducted to remove halogen gas. When the halogen component in the quartz glass remains, it can be seen that the transmittance decreases in the vicinity of the 250 nm wavelength as shown in FIG. The higher the halogen content, the lower the transmittance. Figure 6 shows the transmittance when the halogen component remaining in the quartz glass is removed. Unlike Figure 5, removing the halogen component can be seen that the UV transmittance is normally improved. When the halogen component remains in the quartz glass, the UV transmittance is lowered, and thus the optical property is deteriorated. Therefore, the removal of the halogen component is essential.

Hereinafter, the configuration of the present invention will be described in detail through specific embodiments. However, it is apparent to those skilled in the art that the scope of the present invention is not limited only to the description of the following examples.

< Example  1: halogen gas change>

During the OH removal experiment by halogen gas atmosphere heat treatment, the experiment was performed by changing the halogen gas type to examine the effect of the halogen gas type on the OH content. As the halogen gas, Cl ₂ , HCl, Cl ₂ / HCl mixed gas was used. The ratio of Cl ₂ / HCl mixed gas was 1: 1 (v / v). Other conditions (gas concentration: 300 cc / min, heat processing temperature: 1000 degreeC, heat processing time: 20hr) were made constant. The experimental results are shown in FIG. 7.

The average OH content was 18 ppm when Cl ₂ was used as the halogen gas, the average OH content was 140 ppm when HCl was used, and the average OH content was 83 ppm when the mixed gas of Cl ₂ and HCl was used. The use of Cl ₂ as halogen gas is more effective than HCl. Since the binding energy of Cl ₂ is 239KJ and the binding energy of HCl is 428KJ, Cl ₂ with low binding energy is considered to be effective in lowering the OH content because the reaction with OH is more active.

< Example  2: halogen gas concentration change>

In order to examine the effect of the halogen gas concentration on the OH content, the experiment was performed by adjusting the gas flow rate to 35cc / min, 100cc / min, 300cc / min, 1000cc / min. Other conditions (halogen gas: Cl _2, the heat treatment temperature: 1000 ℃, heat treatment time: 20hr) was constant. The experimental results are shown in FIG. 8.

The average OH content is 53 ppm when the halogen gas concentration is 35 cc / min, the average OH content is 33 ppm when the concentration is 100 cc / min, and the average OH content is 18 ppm and 1000 cc / min when the concentration is 300 cc / min. In this case, the average OH content was 16 ppm. The higher the halogen gas concentration, the lower the OH content, but no more than 300cc / min.

< Example  3: heat treatment temperature change>

In order to examine the effect of the halogen gas heat treatment temperature on the OH content, the heat treatment temperatures were tested at 800 ° C., 900 ° C., 1000 ° C., and 1100 ° C., respectively, and other conditions (halogen gas: Cl ₂ , halogen gas concentration: 300 cc / min, Heat treatment time: 20hr) was made constant. The experimental results are shown in FIG. 9.

When the heat treatment temperature of the halogen gas atmosphere was 800 ° C, the average OH content was 98ppm, 51ppm at 900 ° C, 18ppm at 1000 ° C, and 16ppm at 1100 ° C. The higher the heat treatment temperature of the halogen gas atmosphere, the lower the OH content, but it was found to be nearly constant above 1000 ° C.

< Example  4: heat treatment time change>

In order to examine the effect of the heat treatment time of halogen gas on the OH content, the heat treatment time was tested at 1hr, 5hr, 20hr, and 40hr, respectively, and other conditions (halogen gas: Cl ₂ , halogen gas concentration: 300cc / min, heat treatment temperature: 1000 ° C) was made constant. The experimental results are shown in FIG. 10.

When the heat treatment time of the halogen gas atmosphere was 1hr, the average OH content was 56ppm, when the 5hr heat treatment was performed, the OH content was 35ppm, the 20hr was 18ppm, and the 40hr was 16ppm. The longer the heat treatment time of the halogen gas atmosphere, the lower the OH content was.

In the OH removal experiment by the halogen gas atmosphere heat treatment, the optimum conditions found by changing the halogen gas type, halogen gas concentration, heat treatment temperature, heat treatment time, etc. were found to be Cl ₂ for halogen gas, 300cc / min for halogen gas flow rate, and 1000 degreeC and heat processing time were 20 hours. At this time, the OH content was 18 ppm.

After the heat treatment of the halogen gas atmosphere for removing OH in the quartz glass, an experiment was performed to remove the halogen component remaining in the quartz glass. Halogen gas atmosphere heat treatment for removing OH in the quartz glass, the halogen component remains in the quartz glass. Cl ₂ Halogen content was 87ppm in case of atmospheric heat treatment (300cc / min in halogen gas flow rate, 1000 ℃ in heat treatment temperature, 20hr heat treatment time), and in case of HCl atmosphere heat treatment (300cc / min in halogen gas flow rate, heat treatment temperature was At 1000 ° C., the heat treatment time was 20 hours, and the halogen content was 4 ppm. When the HCl atmosphere heat treatment is not a problem because the halogen content is not high, but when the Cl ₂ atmosphere heat treatment, the halogen content is high, the halogen component removal process is required.

Halogen Gas Atmosphere for OH Removal in Quartz Glass After the heat treatment, the experiment is performed to find the optimum conditions by changing the type of gas used, concentration of gas, heat treatment temperature, heat treatment time, etc. to remove the halogen component remaining in the quartz glass. It was.

< Example  5: selection of halogen-free gas>

During the halogen-removing experiments remaining after the heat treatment of the halogen gas atmosphere, experiments were performed by changing the halogen-removing gas type to examine the effect of the halogen-removing gas on the halogen content. Halogen gas atmosphere heat treatment conditions were halogen gas Cl ₂ , halogen gas flow rate 300cc / min, heat treatment temperature is 1000 ℃, heat treatment time was 20hr. As the halogen removing gas, H ₂ and O ₂ were used. Other conditions (halogen removal gas concentration: 300 cc / min, heat processing temperature: 1000 degreeC, heat processing time: 20hr) were made constant. The experimental results are shown in FIG. 11.

The average halogen content before the halogen removal treatment was 87 ppm, 1 ppm when H ₂ was used as the halogen removal gas, and 11 ppm when O ₂ was used. It has been found that the use of H ₂ as the halogen elimination gas is more effective than O ₂ .

< Example  6: Halogen elimination gas  Concentration change>

In order to examine the effect of the halogen elimination gas concentration on the halogen content, the experiment was performed by changing the halogen eliminating gas concentration. Halogen gas atmosphere heat treatment conditions were halogen gas Cl ₂ , halogen gas flow rate 300cc / min, heat treatment temperature is 1000 ℃, heat treatment time was 20hr. Halogen removal gas concentration was made into 35 cc / min, 100 cc / min, 300 cc / min, and 1000 cc / min, respectively. Other conditions (removing halogen gas: H _2, the heat treatment temperature: 1000 ℃, heat treatment time: 20hr) was constant. The experimental results are shown in FIG. 12.

The average halogen content before the halogen removal treatment was 87 ppm, the average halogen content was 10 ppm when the halogen removal gas concentration was 35 cc / min, 5 ppm at 100 cc / min, 1 ppm at 300 cc / min, and average at 1000 cc / min. Halogen content was 1 ppm. The halogen content decreased as the concentration of halogen elimination gas increased, but there was almost no change above 300 cc / min.

< Example  7: Halogen Removal  Heat Treatment Temperature Variation>

During the halogen-removing experiments after the halogen gas atmosphere heat treatment, the effect of the halogen-removing gas heat treatment temperature on the halogen content was examined by changing the halogen-removing heat treatment temperature. Halogen gas atmosphere heat treatment conditions were halogen gas Cl ₂ , halogen gas flow rate 300cc / min, heat treatment temperature is 1000 ℃, heat treatment time was 20hr. The halogen removal heat treatment temperature was 800 degreeC, 900 degreeC, 1000 degreeC, and 1100 degreeC. Other conditions (removing halogen gas: H _2, halogen remove gas concentration: 300cc / min, heat treatment time: 20hr) was constant. The experimental results are shown in FIG. 13.

The average halogen content before the halogen removal treatment was 87ppm, the average halogen content was 23ppm when the halogen removal heat treatment temperature was 800 ℃, 11ppm for 900 ℃, 1ppm for 1000 ℃, 1ppm for 1100 ℃. The halogen content decreased with increasing halogen removal heat treatment temperature, but hardly changed above 1000 ° C.

< Example  8: Halogen Removal Heat Treatment Time Variation>

In order to examine the effect of halogen removal heat treatment time on halogen content, experiments were carried out with varying heat treatment time. Halogen gas atmosphere heat treatment conditions were halogen gas Cl ₂ , halogen gas flow rate 300cc / min, heat treatment temperature is 1000 ℃, heat treatment time was 20hr. Halogen removal heat processing time was made into 1 hr, 5 hr, 20 hr, and 40 hr. Other conditions (removing halogen gas: H _2, halogen remove gas concentration: 300cc / min, the heat treatment temperature: 1000 ℃) was constant. The experimental results are shown in FIG. 14.

The average halogen content before the halogen removal treatment was 87ppm, the average halogen content was 13ppm when the heat treatment time was 1hr, 8ppm at 5hr treatment, 1ppm at 20hr treatment, 1ppm at 40hr treatment. As the heat treatment time was increased, the halogen content decreased, but there was almost no change above 20hr.

< Example  9: OH  Content Distribution Measurement>

When the halogen gas atmosphere heat treatment is performed to remove OH in the quartz glass, the OH content is lowered, but the OH content is changed during the halogen removal process. When Cl ₂ was used as the halogen gas (halogen gas concentration: 300 cc / min, heat treatment temperature: 1000 ° C., heat treatment time: 20 hr), the OH content was 18 ppm, and when the halogen component was removed by heat treatment in an H ₂ atmosphere (halogen) Removal gas concentration: 300 cc / min, heat treatment temperature: 1000 ℃, heat treatment time: 20hr) OH content was 78ppm. In addition, OH is removed by using Cl ₂ as halogen gas (halogen gas concentration: 300cc / min, heat treatment temperature: 1000 ° C., heat treatment time: 20hr), and then heat-treated in O ₂ atmosphere to remove halogen component (halogen removal). Gas concentration: 300 cc / min, heat treatment temperature: 1000 ° C., heat treatment time: 20 hr) and the OH content was 20 ppm. The OH content change before and after the halogen removal heat treatment is shown in FIG. 15.

In the case of halogen-free removal heat treatment in H ₂ atmosphere, O ₂ and H ₂ in silica are recombined to increase the OH content. However, there was almost no change in OH content in the case of halogen-free removal heat treatment in O ₂ atmosphere, but the halogen content remained 11ppm, which is not suitable for halogen-free removal.

When used as anti-vibration glass for projection display, it is divided into dozens of anti-vibration glass in one wafer, so OH content distribution is important even when OH in quartz glass is removed with halogen gas atmosphere. OH content distribution analysis was analyzed by measuring nine points as shown in FIG.

Halogen gas atmosphere heat treatment for OH removal is carried out under the condition of halogen gas Cl ₂ , halogen gas concentration 300cc / min, heat treatment temperature 1000 ℃, heat treatment time 20hr, and halogen-free removal heat treatment of halogen component gas H ₂ , 300cc / min, heat treatment As a result of measuring the OH content at the measurement point of FIG. 4 with respect to a sample performed under the condition of 1000 ° C. and a heat treatment time of 20 hr, a result as shown in FIG. 16 was obtained. The average value was 87 ppm, the maximum value was 99 ppm, the minimum value was 75 ppm, and the range value was 24 ppm.

< Example  10: Slow cooling  By heat treatment OH  And halogen concentration distribution control>

Slow heat treatment is required to reduce the variation in OH concentration distribution generated when the heat treatment is performed to remove the halogen after the halogen gas atmosphere heat treatment to remove the OH. It is possible to control the virtual temperature by the slow cooling heat treatment, thereby controlling the OH concentration distribution.

Figure 16 shows the OH concentration distribution change before and after the slow cooling heat treatment for the heat-treated sample to remove the halogen component after the heat treatment of the halogen gas atmosphere. Changes in OH concentration distribution after slow cooling were performed so that the virtual temperatures were 1100 ° C and 1000 ° C, respectively. In case of the slow cooling heat treatment to the virtual temperature of 1100 ℃, the average value of OH concentration was 87ppm, the maximum value was 95ppm, the minimum value was 79ppm, and the range value was 16ppm. The average value of the concentration was 87 ppm, the maximum value was 91 ppm, the minimum value was 83 ppm, and the range value was 8 ppm.

Halogen gas Cl ₂ , halogen gas concentration 300cc / min, heat treatment temperature 1000 ℃, heat treatment time 20hrs, after halogen gas atmosphere heat treatment for OH removal, halogen remove gas H ₂ , halogen remove gas concentration 300cc / min, heat treatment temperature In the case where the halogen component removal heat treatment was performed at 1000 ° C. and a heat treatment time of 20 hr, and the slow cooling was performed at a virtual temperature of 1000 ° C., the OH concentration distribution of the quartz glass wafer was 87 ± 4 ppm, showing a very uniform value.

When quartz glass is used as anti-vibration glass for projection displays, it is divided into dozens of ADGs on one wafer. Halogen content is also important when OH is removed from the quartz glass and halogen is removed by halogen gas atmosphere. Halogen content distribution analysis was analyzed by measuring the nine points as shown in FIG.

As a result of measuring the content of the halogen component, a result as shown in FIG. 17 was obtained. The average value was 1 ppm, the maximum value was 4 ppm, the minimum value was 0 ppm, and the range value was 4 ppm.

Annealing heat treatment is required to reduce the variation in the halogen concentration concentration that occurs when the heat treatment is performed after the halogen gas atmosphere heat treatment to remove OH. By controlling the slow cooling, the virtual temperature can be controlled, and accordingly, the halogen component concentration distribution can be controlled.

FIG. 17 illustrates changes in the concentration distribution of halogen components before and after slow cooling for a heat-treated sample for halogen component removal after halogen gas atmosphere heat treatment. The average value of halogen concentration was 1ppm, the maximum value was 3ppm, the minimum value was 0ppm, and the range value was 3ppm when the slow cooling heat treatment was performed so that the virtual temperature was 1100 ° C. The average value of was 1 ppm, the maximum value was 2 ppm, the minimum value was 0 ppm, and the range value was 2 ppm.

Halogen gas Cl ₂ , Halogen gas concentration 300cc / min, Heat treatment temperature 1000 ℃, Heat treatment time 20hrs Halogen gas atmosphere for OH removal after heat treatment, Halogen elimination gas H ₂ , Halogen elimination gas concentration 300cc / min, Heat treatment temperature Halogen content removal heat treatment was performed under conditions of 1000 ℃ and heat treatment time 20hr, and the slow concentration heat treatment was performed at a virtual temperature of 1000 ℃, and the halogen component concentration distribution of the quartz glass wafer was 1 ± 1 ppm, showing a very uniform value.

Dust Proof Glass is located on the front and back of the high-temperature poly-Si TFT-LCD substrate and the color filter substrate to prevent deterioration of image quality caused by dust or foreign matter adhering to the substrate surface. It also functions to prevent mechanical damage of the substrate glass. In addition, since the projection display device uses a halogen lamp as a light source, high heat is generated. Therefore, when the heat resistance of the quartz glass is different, the adhesion decreases due to the difference in the thermal expansion coefficient of the substrate / dustproof glass, leading to deterioration of image quality. do. Accordingly, the present invention prevents deterioration of image quality by providing a dustproof glass at a level similar to the thermal expansion coefficient of the quartz glass for a substrate.

In addition, the method of the present invention can be applied to dust-proof glass, optical engine components, photomask substrates, stepper lenses, and the like of liquid crystal projector optical engines, which are rapidly increasing in demand.

In addition, the method of the present invention can be utilized as a base technology for manufacturing substrate glass for high temperature poly-Si TFT-LCD, and can be applied to other technologies for manufacturing quartz glass for display, semiconductor, and precision optics.

Claims (8)

Removing OH groups in the quartz glass with a halogen using gas Cl ₂ , a gas concentration of 200 cc / min or more, a heat treatment temperature of 950 ° C. or more, and a heat treatment time of 10 hours or more; Residual halogen is removed as H ₂ , a gas concentration of 200 cc / min or more, a heat treatment temperature of 950 ° C. or more, and a heat treatment time of 10 hours or more as a halogen removing gas; Slow cooling to a virtual temperature of 1050 ° C. or lower; A method for controlling the OH content in quartz glass, characterized by having a uniform OH and halogen content. The method of claim 1, Gas concentration during OH removal is a method for controlling the OH content in the quartz glass, characterized in that 200 ~ 1000cc / min. The method of claim 1, The method of controlling the OH content in the quartz glass, characterized in that the heat treatment temperature at the time of OH removal is 950 ~ 1,100 ℃. The method of claim 1, Heat treatment time at the time of OH removal is a method for controlling the OH content in the quartz glass, characterized in that 10 to 40 hours. The method of claim 1, The method of controlling the OH content in the quartz glass, characterized in that the gas concentration at the time of halogen removal is 200 ~ 1000cc / min. The method of claim 1, The heat treatment temperature at the time of halogen removal is 950 ~ 1,100 ℃ quartz glass manufacturing method for controlling the OH content in the quartz glass, characterized in that. The method of claim 1, Heat treatment time when removing the halogen is a quartz glass manufacturing method for controlling the OH content in the quartz glass, characterized in that 10 to 40 hours. The method of claim 1, Method of controlling the OH content in the quartz glass, characterized in that the slow cooling heat treatment to a virtual temperature 950 ~ 1050 ℃ after halogen removal heat treatment.

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