Preparation method of MAS glass with high etching uniformity

Abstract

The invention relates to a method for producing MAS glasses, characterized in that 10 mol.% to 40 mol.% of MgO, 5 mol.% to 30 mol.% of Al2O3 and 40 mol.% to 70 mol.% of SiO2 or precursors of these raw materials are mixed, the mixture is melted, the melt is cooled and comminuted into particles having a diameter of less than 10 mm, preferably less than 5 mm, particularly preferably less than 2 mm, the particles are heated and melted, and the melt is cooled. The invention also relates to a MAS glass obtainable according to this method, to a component comprising this MAS glass and to the use of this component.

Description

Technical Field

[0001] The present invention relates to a method for preparing MAS glass, MAS glass obtainable according to the method, a component comprising the MAS glass, and the use of the component. Background Art

[0002] Plasma-assisted dry etching (referred to as "plasma etching" for short) is an indispensable technology for manufacturing ultra-fine structures in semiconductor devices, high-resolution displays, and solar cells.

[0003] EP 3 708 547 A1 describes plasma etching in a vacuum reactor under relatively high temperatures and a highly corrosive atmosphere. During this process, an etching gas is introduced into the low pressure inside the vacuum reactor. By high-frequency discharge between electrodes or electrodeless microwave discharge, a plasma with high reactivity and etching activity can be generated.

[0004] US7,084,084B2 discloses the application of halogenated gases, such as fluorine-containing or chlorine-containing gases, in plasma etching. Halogenated gases and their plasmas have high reactivity and can therefore be widely used in various steps, such as being used as etching gases in the etching process or cleaning process in the semiconductor industry. The halogenated gases and plasmas used are, for example, fluorine-containing gases (such as F2, HF, CF4, C2F6, C3F8, C4F8, CHF3, SF6, and NF3), chlorine-containing gases (such as Cl2, HCl, BCl3, and CCl4), and bromine-containing gases (such as Br2 and HBr).

[0005] Elemental fluorine, fluoride ions, and free radicals not only exhibit the required etching effect but also react with other components exposed to the plasma. The resulting corrosion loss may cause the generation of particles and cause serious changes in the components used, and ultimately the component must be replaced.

[0006] Due to its high chemical resistance to many substances used in the manufacturing process and relatively high high-temperature resistance, quartz glass is often used for high-load components. This is especially true for the etching chamber. However, in the case of fluorine-containing etching gases, SiO2 in the quartz glass reacts with reactive fluorine to form SiF4. The boiling point of SiF4 is as low as -86 °C, so this compound is extremely likely to turn into a gas phase, which will cause serious corrosion on the surface of the quartz glass and the formation of particles.

[0007] As is well known, a solution to the fluorination corrosion of quartz is doping. Here, it should be achieved that the element added to the quartz glass forms a compound with the halogenated gas used, and the sublimation temperature or boiling point of this compound is higher than that of the halogenated silicon formed in the quartz glass. The resulting glass network has a reduced etching rate.

[0008] When doping, oxides of Sm, Eu, Yb, Pm, Nd, Ce, Tb, Gd, Ba, Mg, Y, Tm, Dy, Ho, Er, Cd, Co, Cr, Cs and / or Zr can be added, but these doping elements may cause damage to the network structure of fused silica glass.

[0009] Specifically, the SiO2 network that constitutes fused silica glass will break due to the incorporation of secondary elements, usually forming locally non-crosslinked oxygen with relatively weak bonding forces. This undesirable phenomenon is particularly harmful under etching conditions, as adding secondary elements will instead locally increase the glass etching rate and reduce glass durability.

[0010] To maintain glass stability after doping, Al, In, Cu, Fe, Bi, Ga and / or Ti can be additionally added as oxides.

[0011] A known doped glass mixture consists of 20 wt.% MgO, 20 wt.% Al2O3 and 60 wt.% SiO2, called MAS glass. During the etching process using a fluorine-containing etching gas, the glass mixture reacts with reactive fluorine to form MgF2. The boiling point of MgF2 is higher than 2200 °C, so this compound hardly turns into a gas phase, thus reducing surface corrosion of the glass mixture and minimizing the etching rate. The prior art also discloses further reducing the etching rate, for example, by doping MgF2 (WO2022075687A1).

[0012] A drawback in the preparation of existing MAS glass is that when melting magnesium, aluminum and silica components to prepare the glass, material inhomogeneity often occurs. This inhomogeneity may stem from insufficient mixing of raw materials and the occurrence of melt phase separation or local crystallization during the preparation process. Such material inhomogeneity will also lead to differences in local etching rates, and thus uneven etching peeling, resulting in a very high risk of particle formation during the plasma etching process. Striated or hazy glass regions are an intuitive qualitative indicator for judging inhomogeneity, while measuring the surface roughness of the glass after etching is an excellent way to quantitatively characterize the material inhomogeneity under different etching rates. The surface topology can accurately reflect the spatial distribution of inhomogeneity and its associated etching rate instability.

[0013] For fluorine-containing plasma etching, there is an urgent need for materials that have both a low etching rate and high etching uniformity and can thus reduce particle release during the etching process. Although XO-Al2O3-SiO2 type materials (X = alkaline earth metal, especially Mg, Ca and Ba) are known to have a relatively low etching rate in the prior art, such materials generally suffer from the defect of insufficient etching uniformity, which may lead to particle release during the etching process. Summary of the Invention

[0014] In view of this, the object of the present invention is to overcome the above-mentioned defects in the prior art. Specifically, the object of the present invention is to provide a MAS glass with simple preparation, which can exhibit high uniformity and can maximize the inhibition of crystallization and phase separation during the solidification process. Such MAS glass should also reduce the etching rate and improve the etching uniformity.

[0015] To achieve the above object, the present invention unexpectedly provides a method for preparing MAS glass according to claim 1 and a MAS glass according to claim 10.

[0016] Advantageous improvements are referred to the dependent claims.

[0017] The advantage of preparing MAS glass by the method according to the present invention is that the MAS glass has extremely high uniformity, thus avoiding crystallization and phase separation. In addition, the MAS glass according to the present invention can reduce the etching rate and improve the etching uniformity. Even for large-sized MAS glass or components, the above advantageous characteristics can be reliably achieved.

[0018] Many specific details will be set forth below in order to provide a thorough understanding of the subject matter of the present invention. However, those skilled in the art should understand that the subject matter of the present invention can still be practiced and reproduced even without knowing these specific details.

[0019] As long as the technical features of different embodiments are mutually compatible, all features of any one embodiment can be combined with the features of other embodiments.

[0020] The terms used in this specification are only for describing specific embodiments and are not intended to limit the subject matter of the present invention. Unless the context clearly dictates otherwise, the singular forms used in this specification and the claims are intended to cover the plural forms, and vice versa, that is, the plural forms also cover the singular forms. It should also be understood that the term "and / or" used herein covers all possible combinations of one or more of the listed related items. It should also be understood that the terms "comprising" and / or "including" used in this specification and the claims indicate the presence of the described features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or the above combinations.

[0021] In this specification and the claims, the terms "comprising" and / or "including" may also mean "consisting of", that is, excluding the presence or addition of one or more other features, steps, operations, elements, components, and / or the above combinations.

[0022] The present invention relates to a method for preparing MAS glass, characterized in that a) Mix 10 mol.% to 40 mol.% of MgO, 5 mol.% to 30 mol.% of Al2O3, and 40 mol.% to 70 mol.% of SiO2 or precursors of these raw materials; b) Melt the mixture obtained in step a); c) Cool and crush the melt obtained in step b) into particles with a diameter of less than 10 mm, preferably less than 5 mm, and particularly preferably less than 2 mm; d) Heat and melt the particles obtained in step c); and e) Cool the melt obtained in step d).

[0023] Preferably, the precursors of these raw materials refer to hydroxides and / or carbonates of the corresponding MgO and Al2O3.

[0024] In a preferred embodiment, the method according to the present invention is characterized in that steps c), d), and e) are performed multiple times, where the cooled melt in step c) is the melt prepared in the previous step e). Multiple times means 2 times, 3 times, 4 times, 5 times, etc. By repeating steps c), d), and e), the uniformity can be further improved.

[0025] In a preferred embodiment, the method according to the present invention is characterized in that the mixture obtained in step b) and / or step d) is heated to a temperature of 1200 °C to 2000 °C, preferably heated to a temperature of 1500 °C to 1750 °C, and particularly preferably heated to a temperature of 1550 °C to 1700 °C.

[0026] In a preferred embodiment, the method according to the present invention is characterized in that the duration of step b) is 0.1 hour to 10 hours, preferably 0.1 hour to 7 hours.

[0027] In a preferred embodiment, the method according to the present invention is characterized in that the duration of step d) is 0.1 hour to 10 hours, preferably 0.1 hour to 7 hours.

[0028] In a preferred embodiment, the method according to the present invention is characterized in that in step e), the mixture obtained in step d) is cooled to a temperature below 25 °C.

[0029] In a preferred embodiment, the method according to the present invention is characterized in that in step e), the mixture obtained in step d) is first rapidly cooled to a temperature of 600 °C to 900 °C, and then significantly slowly cooled to a temperature below 25 °C.

[0030] Fast, for example, means a cooling rate higher than 75 K per minute, preferably higher than 90 K per minute and lower than 120 K per minute. Slow, for example, means a cooling rate lower than 5 K per minute, preferably lower than 2.5 K per minute and higher than 0.5 K per minute.

[0031] The advantage of rapidly cooling to a temperature range of 600 °C to 900 °C is to minimize the risk of crystallization, thereby further avoiding the formation of inhomogeneities. Subsequently, slow cooling to room temperature can avoid the formation of stress or cracks.

[0032] In a preferred embodiment, the method according to the invention is characterized in that, in step b) and / or step d), the heating of the mixture is carried out in a Pt crucible and / or a Pt / Rh crucible.

[0033] In a preferred embodiment, the method according to the invention is characterized in that, in step e), the cooling of the mixture is carried out in a steel mold coated with a release agent in an annealing furnace.

[0034] In a preferred embodiment, the method according to the invention is characterized in that, during the preparation of the MAS glass, less than 0.01 mol.% of a material additive comprising fluoride and / or yttrium compound is added.

[0035] The invention also relates to a MAS glass obtainable by the above method.

[0036] All the above definitions and preferred embodiments of the method according to the invention equally apply to the MAS glass obtainable by the above method.

[0037] In a preferred embodiment, the MAS glass obtainable by the above method according to the invention is characterized in that the MAS glass contains 10 mol.% to 40 mol.% of MgO, 5 mol.% to 30 mol.% of Al2O3 and 40 mol.% to 70 mol.% of SiO2; the MAS glass is non-crystalline (röntgenamorph) as detected by X-ray; and the average roughness (R a ) of the glass surface after the following etching process is less than 50 nm, preferably less than 30 nm, particularly preferably less than 10 nm, and especially preferably less than 5 nm, wherein the average roughness (R a ) is measured according to the ISO 4287-1:1984 standard.

[0038] In a preferred embodiment, the MAS glass obtainable by the above method according to the invention is characterized in that the average roughness depth (R z ) of the glass surface after the following etching process is less than 100 nm, preferably less than 70 nm, particularly preferably less than 50 nm, and especially preferably less than 35 nm, wherein the average roughness depth (Rz Measured according to ISO 4287-1:1984 standard.

[0039] Within the scope of the present invention, etching uniformity refers to the local variation of the etching behavior. The smaller the local variation of the etching behavior, the higher the etching uniformity of the MAS glass. By standardizing the measurement of the surface roughness (R a value and R z value) of the MAS glass after a specified etching process, the etching uniformity can be quantitatively determined.

[0040] Etching uniformity is characterized by the surface unevenness after the etching process and can be quantitatively expressed by variables such as the arithmetic mean roughness (R a ) and the mean depth of roughness (R z ). The lower the R a value and the R z value, the higher the etching uniformity. R a is defined as the average distance from the surface measurement points to the midline. R z is defined as the average value of the individual roughness depths within five consecutive single measurement segments of the roughness profile curve. The roughness variables R a and R z are measured according to ISO 4287-1:1984 standard.

[0041] The determination of the etching uniformity of the MAS glass can be achieved through the following steps (specific etching process): 1. Clean the MAS glass; 2. Mask specific glass areas with Kapton tape; 3. Etching process.

[0042] The MAS glass is cleaned through the following wet chemical steps: 1. Conduct 100% ultrasonic scanning for 10 minutes with Tickopur R33 (5%); 2. Conduct solvent cleaning with acetone and isopropyl alcohol; 3. Rinse with deionized water and dry.

[0043] Tickopur R33 (5%) is a general ultrasonic cleaner containing 5% to 15% anionic surfactant, 5% to 15% phosphate, less than 5% nonionic surfactant, less than 5% silicate, and a complexing agent.

[0044] The specific method of masking specific glass areas with Kapton tape is to partially mask specific substrate areas with a plasma-stabilized Kapton film.

[0045] According to the present invention, the etching process of the smooth MAS glass surface is carried out in a Sentech Si-500 type device. The following parameters are set in the relevant execution software: 1. ICP: 500 W; 2. High-frequency bias voltage: 200 W; 3. Choke valve: 100% (0.25 Pa); 4. CHF3: 30 sccm; 5. Etching timing: cyclic mode (etching for 2 minutes, cooling for 1 minute); 6. Backside helium cooling: 1000 Pa; 7. Heating power: 0%; and 8. Sample stage: made of aluminum.

[0046] The surface roughness of the glass was measured according to the ISO 4287-1:1984 standard. The etching depth was determined by measuring the etching profile (i.e., the cross-section of the etching step) under an optical microscope. The etching rate was determined based on the function of the etching profile changing with time.

[0047] Compared with undoped fused silica glass, the MAS glass according to the present invention exhibits an etching rate (nm / min) that is approximately eight times lower while having fairly good etching uniformity (R a value and R z value). Compared with existing MAS glass, the MAS glass according to the present invention exhibits better etching uniformity (R a value and R z value). These advantageous properties can be unexpectedly obtained by using the method according to the present invention.

[0048] In a preferred embodiment, the MAS glass obtainable by the above method according to the present invention is characterized in that the MAS glass is amorphous as detected by X-ray.

[0049] The MAS glass that is amorphous as detected by X-ray is a glass without large-area long-range ordered crystalline regions, so only extremely diffuse X-ray reflections (i.e., so-called glass peaks) will appear in the corresponding inspection.

[0050] In the context of the present invention, being amorphous as detected by X-ray means that there are no crystalline regions exceeding 10 nm in the MAS glass, which can be determined, for example, using a diffractometer.

[0051] In a preferred embodiment, the MAS glass obtainable by the above method according to the present invention is characterized in that the MAS glass contains 20 mol.% to 40 mol.% of MgO, 5 mol.% to 30 mol.% of Al2O3, and 40 mol.% to 70 mol.% of SiO2, preferably 25 mol.% to 35 mol.% of MgO, 10 mol.% to 25 mol.% of Al2O3, and 50 mol.% to 65 mol.% of SiO2.

[0052] In a preferred embodiment, the MAS glass obtainable by the above method according to the invention is characterized in that the MAS glass contains less than 0.01 mol.% of a material additive comprising fluoride and / or yttrium compound. The advantage thereof is that the risk of forming local inhomogeneities during the material preparation can be further minimized.

[0053] The homogeneity of the optical substrate is characterized by the refractive index change, which will cause transmitted wavefront distortion and polarization transmission effect. High homogeneity or low refractive index change is particularly important for high-power laser applications. The melting process during the material preparation will cause homogeneity fluctuations. Mixing errors and thermodynamic imbalance will lead to density fluctuations. In addition, the cooling and annealing processes will also cause structural deformation. The inhomogeneity is manifested as overall inhomogeneity (the refractive index deviation of the whole glass) or striation defects (the local homogeneity deviation within the glass with a length of 0.1 mm to 2 mm). Inclusions are foreign substances present in the optical glass, which may be caused by melting contamination, incomplete melting of the whole batch of substrates, and residues of low-solubility wall materials, etc. In addition, gas bubbles will also be generated during the glass melting reaction. During the clarification stage of glass melting, the bubbles can be almost completely eliminated.

[0054] In a preferred embodiment, the MAS glass obtainable by the above method according to the invention is characterized in that the MAS glass contains less than 100 ppm of crystal growth promoting elements.

[0055] In a preferred embodiment, the MAS glass obtainable by the above method according to the invention is characterized in that more than 80%, preferably more than 90%, particularly preferably more than 95% of the Al atoms contained therein are tetrahedrally coordinated with oxygen.

[0056] This has the advantage of simplifying the formation of uniformly solidified and X-ray-detected amorphous glass and suppressing crystallization.

[0057] The glass structure and the incorporation of each cation will change with the MgO / Al2O3 ratio. A high proportion of Mg(II) will lead to the formation of non-bridging oxygen (NBO), thereby reducing the viscosity. The content of non-bridging oxygen depends on the MgO / Al2O3 ratio. As long as the ratio is less than 1, magnesium will be incorporated as a glass former, that is, one Mg(II) ion can stabilize two - [AlO4] tetrahedra (tetrahedrally coordinated aluminum). If the Mg(II) content is further increased, Mg(II) will be incorporated as a glass modifier, resulting in the formation of NBO and further reducing the viscosity.

[0058] The content of four - coordinated Al atoms is determined by Multiple Quantum Magic Angle Spinning Nuclear Magnetic Resonance (MQMAS - NMR) measurement technology.

[0059] For example, on a Varian VNMRs 11.7T NMR spectrometer, a Varian 1.6mm T3 - MAS - NMR probe is used to record the NMR spectrum at a spinning frequency of 35 kHz. To support the results, an 27 AI - MAS - NMR spectrum is also generated at 7T magnetic field (Bruker Avance III spectrometer; 4 - mm triple - resonance probe; spinning frequency 10 kHz).

[0060] In a preferred embodiment, the MAS glass obtainable by the above - mentioned method according to the present invention is characterized in that the coefficient of linear thermal expansion (CTE) of the MAS glass is greater than 3.0×10 -6 K -1 (in the temperature range of 300 to 600 °C), preferably greater than 4.0×10 -6 K -1 (in the temperature range of 300 to 600 °C), more preferably greater than 4.5×10 -6 K -1 (in the temperature range of 300 to 600 °C).

[0061] The coefficient of linear thermal expansion (CTE) is a material property that characterizes the dimensional change behavior of a material when the temperature changes, which results from the thermal expansion effect. The thermal expansion behavior of most materials is non - uniform in different temperature ranges. Therefore, the thermal expansion coefficient itself is temperature - dependent, so a reference temperature or temperature range is specified.

[0062] The coefficient of linear thermal expansion (CTE) is determined according to the ISO 7991 - 1998 standard.

[0063] In a preferred embodiment, the MAS glass obtainable by the above - mentioned method according to the present invention is characterized in that the glass transition temperature (T g ) of the MAS glass is lower than 900 °C, preferably lower than 850 °C, and particularly preferably lower than 800 °C.

[0064] The glass transition temperature (T g ) is a material property that characterizes a significant transition in the deformation ability of the glass. The glass transition temperature demarcates the low - temperature region of brittle energy elastic state (where the material is in a glassy state) and the high - temperature region of soft entropy elastic state.

[0065] The glass transition temperature (T g ) is determined according to the ISO 7884 - 8:1998 standard.

[0066] The advantage of lowering the glass transition temperature is that the oxides used to make the glass can be miscible at lower temperatures, and the glass produced can be formed at lower temperatures.

[0067] In a preferred embodiment, the MAS glass obtainable by the above method according to the present invention is characterized in that the MAS glass is not flame polished.

[0068] Flame polishing is costly and may cause geometric deformation of the component, so there are technical defects.

[0069] After grinding a glass component, the glass surface usually becomes rough and dull, so flame polishing needs to be applied to obtain a smooth surface by heating and leveling the surface. In this preferred embodiment of the present invention, flame polishing is not required.

[0070] In a preferred embodiment, the MAS glass obtainable by the above method according to the present invention is characterized in that the plasma etching rate of the MAS glass is more than 50%, preferably more than 70%, particularly preferably more than 85% lower than that of fused silica glass.

[0071] In a preferred embodiment, the MAS glass obtainable by the above method according to the present invention is characterized in that the plasma etching rate of the MAS glass is less than 50 nm / min, preferably less than 40 nm / min, particularly preferably less than 30 nm / min.

[0072] The plasma etching depth is determined by measuring the etching profile (i.e., the cross-section of the etching step) under an optical microscope. The plasma etching rate refers to the etching rate defined when etching a material with a plasma. The etching rate is defined as the thickness of the material etched per unit time. The relative etching rate is obtained by comparing the etching rate ratios of different materials. The etching rate is determined by measuring the etching profile over a period of time.

[0073] The present invention also relates to a component comprising the above MAS glass.

[0074] All the definitions and preferred embodiments regarding the method according to the present invention and the MAS glass according to the present invention also apply to the said component.

[0075] In a preferred embodiment, the component according to the present invention is used in semiconductor manufacturing, preferably in an etching chamber.

[0076] All the definitions and preferred embodiments regarding the method according to the present invention and the MAS glass according to the present invention also apply to the use of the component. Detailed Description of the Invention

[0077] The present invention will be described in detail below in conjunction with non-limiting examples.

[0078] Those skilled in the art should understand that using CaO and its precursors instead of MgO and its precursors can also produce similar results.

[0079] The preparation temperature of the glass is about 1600 °C to 1700 °C. As listed in Table 1, each time 300 grams of the mixture is placed into a Pt crucible and a Pt / Rh crucible for melting. The preparation conditions can be seen in detail in Table 1 and Table 2. First, the glass is melted at the melting temperature T1 for a duration t1. Subsequently, the cooled melt is ground and subjected to a secondary melting at temperature T2 for a duration t2. After the secondary melting, the melt is poured into a metal mold. The melting time mainly depends on the duration required to form a clear and bubble-free melt. Accordingly, the high melting point components require a longer time (and a higher temperature). Due to the need for a special geometry, the glass amount of certain components will also vary, and in some cases, an increased crucible filling amount is required. Accordingly, the melting process of these components also requires a longer time.

[0080] Facts have shown that Glass No. 1 (Table 1 and Table 2) can also be melted at a temperature of 1560 °C. However, the experimental melt takes a relatively longer time to reach a bubble-free state. To ensure better uniformity and that the glass can be cast better, a temperature of 1650 °C is selected for manufacturing. Then the glass is poured into a steel mold coated with a release agent and transferred to an annealing furnace. The annealing furnace is preheated to 810 °C and then closed to ensure slow cooling (1 - 2 K / min) to room temperature.

[0081] Table 1: Components of MAS Glass Table 2: Melting Temperature and Melting Duration of MAS Glass The summary of the characteristic parameters measured by a dilatometer (heating rate 5 K / min) is shown in Table 3. Research has shown that low thermal expansion coefficient (CTE) glasses generally exhibit high glass transition temperatures. This is a common problem in the field of fuel cell applications. Such applications require both a high thermal expansion coefficient and a high glass transition temperature. However, in the MAS glass system, T gHowever, the changes in CTE do not show a completely synchronous pattern with respect to SiO2 content. The higher the SiO2 content, the lower the CTE. A high MgO content increases the CTE. The glass transition temperature increases with increasing SiO2 concentration. However, this dependence is not as strong as that of the MgO / Al2O3 ratio, so the highest glass transition temperature is not observed when the SiO2 content is at its maximum. The reason lies in that the glass structure and the incorporation of various cations change with the MgO / Al2O3 ratio. A high proportion of Mg(II) leads to the formation of non-bridging oxygen (NBO), thereby reducing the viscosity. However, Mg(II) can be incorporated into the glass not only as a network modifier but also as a network former. The content of non-bridging oxygen depends on the MgO / Al2O3 ratio. As long as this ratio is less than 1, magnesium is incorporated as a network former, i.e., one Mg(II) ion can stabilize two [AlO4] tetrahedra. If the Mg(II) content is further increased, Mg(II) is incorporated as a network modifier, resulting in the formation of NBO and further reducing the viscosity. - tetrahedra. If the Mg(II) content is further increased, Mg(II) is incorporated as a network modifier, resulting in the formation of NBO and further reducing the viscosity.

[0082] Table 3: Glass transition temperature, linear thermal expansion coefficient, and softening point of MAS glasses To determine the crystallization tendency, glass fragments were placed in a corundum crucible for melting. For this purpose, the glass was loaded into the crucible at room temperature and then transferred to an annealing furnace preheated to 1700 °C. After a few minutes, the annealing furnace was cooled at a rate of 5 K / minute. This cooling rate was maintained until about 1000 °C. After the temperature dropped below 1000 °C, the annealing furnace was cooled more slowly accordingly. The resulting MAS glasses were clear and amorphous as detected by X-rays.

[0083] The determination of the etching uniformity of MAS glasses was achieved through the following steps: 1. Clean the MAS glasses; 2. Mask specific glass areas with Kapton tape; 3. The etching process.

[0084] The MAS glasses were cleaned through the following wet chemical steps: 1. Conduct 100% ultrasonic scanning for 10 minutes with Tickopur R33 (5%); 2. Conduct solvent cleaning with acetone and isopropyl alcohol; 3. Rinse with deionized water and dry.

[0085] Tickopur R33 (5%) is a general ultrasonic cleaner containing 5% to 15% anionic surfactant, 5% to 15% phosphate, less than 5% non-ionic surfactant, less than 5% silicate, and a complexing agent.

[0086] The specific way to shield a specific glass area with Kapton tape is to partially shield a specific substrate area with a plasma-stabilized Kapton film.

[0087] According to the present invention, the etching process of the smooth MAS glass surface is carried out in a Sentech Si-500 type device. The following parameters are set in the relevant execution software: 1. ICP: 500 W; 2. High-frequency bias voltage: 200 W; 3. Choke valve: 100% (0.25 Pa); 4. CHF3: 30 sccm; 5. Etching timing: (cycle mode, 2 minutes of etching, 3 minutes of cooling); 6. Backside helium cooling: 1000 Pa; 7. Heating power: 0%; and 8. Sample stage: aluminum.

[0088] The total duration of the etching process is up to 40 minutes.

[0089] The glass surface roughness is measured according to the ISO 4287-1:1984 standard. The etching depth is determined by measuring the etching profile (i.e., the cross-section of the etching step) under an optical microscope. The etching rate is determined based on the function of the etching depth varying with time.

[0090] Table 4: Etching rate, etching depth, and surface roughness of MAS glass Table 4 shows that compared with the reference sample of undoped quartz, the MAS glass according to the present invention exhibits a significantly improved etching rate and a quite high etching uniformity.

Claims

1. A method for preparing MAS glass, characterized in that, a) mixing 10 mol.% to 40 mol.% of MgO, 5 mol.% to 30 mol.% of Al2O3 and 40 mol.% to 70 mol.% of SiO2 or precursors of these raw materials; b) melting the mixture obtained in step a); c) cooling and pulverizing the melt obtained in step b) into particles with a diameter less than 10 mm, preferably less than 5 mm, particularly preferably less than 2 mm; d) heating and melting the particles obtained in step c); and e) cooling the melt obtained in step d).

2. The method according to claim 1, characterized in that, steps c), d) and e) are performed multiple times, wherein the cooled melt in step c) is the melt prepared in the previous step e).

3. The method according to any one of the preceding claims, characterized in that, in step b) and / or step d), the mixture is heated to a temperature of 1200 °C to 2000 °C, preferably heated to a temperature of 1500 °C to 1750 °C.

4. The method according to any one of the preceding claims, characterized in that, the duration of step b) is 0.1 hour to 10 hours, preferably 0.1 hour to 7 hours.

5. The method according to any one of the preceding claims, characterized in that, the duration of step d) is 0.1 hour to 10 hours, preferably 0.1 hour to 7 hours.

6. The method according to any one of the preceding claims, characterized in that, in step e), the mixture obtained in step d) is cooled to a temperature below 25 °C.

7. The method according to any one of the preceding claims, characterized in that, in step e), the mixture obtained in step d) is first rapidly cooled to a temperature of 600 °C to 900 °C, and then slowly cooled to a temperature below 25 °C.

8. The method according to any one of the preceding claims, characterized in that, in step b) and / or step d), the mixture is heated in a Pt crucible and / or a Pt / Rh crucible.

9. The method according to any one of the preceding claims, characterized in that, in step e), the mixture is cooled in a steel mold coated with a mold release agent in an annealing furnace.

10. A MAS glass obtained by the method according to any one of claims 1 to 9.

11. The MAS glass according to claim 10, comprising 10 mol.% to 40 mol.% of MgO, 5 mol.% to 30 mol.% of Al2O3 and 40 mol.% to 70 mol.% of SiO2, characterized in that, The MAS glass is amorphous as detected by X-ray, and the surface of the MAS glass has an average roughness (R a after the etching process with steps 1 to 3 specified in the specification) of less than 50 nm, preferably less than 30 nm, particularly preferably less than 10 nm, and especially preferably less than 5 nm, wherein the average roughness (R a ) is measured according to the ISO 4287-1:1984 standard.

12. The MAS glass according to any one of claims 10 or 11, comprising 20 mol.% to 40 mol.% of MgO, 5 mol.% to 30 mol.% of Al₂O₃, and 40 mol.% to 70 mol.% of SiO₂, preferably 25 mol.% to 35 mol.% of MgO, 10 mol.% to 25 mol.% of Al₂O₃, and 50 mol.% to 65 mol.% of SiO₂.

13. The MAS glass according to any one of claims 10 to 12, characterized in that the MAS glass contains less than 0.01 mol.% of a material additive comprising fluoride and / or yttrium compound.

14. The MAS glass according to any one of claims 10 to 13, characterized in that in the MAS glass, more than 80%, preferably more than 90%, of the contained Al atoms are tetrahedrally coordinated with oxygen.

15. The MAS glass according to any one of claims 10 to 14, characterized in that The linear expansion coefficient (CTE) of the MAS glass is greater than 3.0×10 -6 K -1 (300 to 600 °C).

16. The MAS glass according to any one of claims 10 to 15, characterized in that the glass transition temperature of the MAS glass is lower than 900 °C.

17. The MAS glass according to any one of claims 10 to 16, characterized in that the relative plasma etching rate of the MAS glass is lower than that of fused silica glass by more than 50%, preferably more than 70%, particularly preferably more than 85%.

18. A component comprising the MAS glass according to any one of claims 10 to 17.

19. The component according to claim 18, characterized in that the component is not flame polished.

20. Use of the component according to claim 19 in semiconductor manufacturing.

21. The use according to claim 20, for use in an etching chamber.

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