Method for producing MAS glass with high etching uniformity

Abstract

The present invention describes a method for producing MAS glass, characterized by mixing 10 to 40 mol % MgO, 5 to 30 mol % Al2O3, and 40 to 70 mol % SiO2 or precursors of these raw materials, melting the mixture, cooling the melt, crushing the mixture into particles with a diameter of less than 10 mm, preferably less than 5 mm, particularly preferably less than 2 mm, heating and melting the particles, and cooling the melt, as well as an MAS glass obtainable by this method, a component comprising MAS glass, and the use of such a component.

Description

[Technical Field]

[0001] The present invention relates to a method for producing MAS glass, to the MAS glass obtained by this method, to components comprising this MAS glass, and to the use of such components.

[0002] Plasma-assisted dry etching (also called "plasma etching" for short) is an essential technique for the fabrication of ultra-fine structures in semiconductor device, high-resolution display, and solar cell fabrication.

[0003] EP 3708547 A1 describes plasma etching in a vacuum reactor at relatively high temperatures and in a highly corrosive atmosphere. An etching gas is flowed through the vacuum reactor at low pressure. A highly reactive, etching-active plasma is generated by a radio-frequency discharge between electrodes or by an electrodeless microwave discharge.

[0004] U.S. Patent No. 7,084,084 discloses the use of halogenated gases, such as fluorine- or chlorine-containing gases, in plasma etching. Halogenated gases and their plasmas are highly reactive and are therefore used in various steps, such as as etching gases in etching or cleaning processes in the semiconductor industry. The halogenated gases and plasmas used are, for example, fluorine-containing gases such as F, HF, CF, C, F, C, F, C, F, CHF, SF, and NF; chlorine-containing gases such as Cl, HCl, BCl, and CCl; and bromine-containing gases such as Br and HBr.

[0005] Elemental fluorine, fluorine ions, and fluorine radicals not only exhibit the desired etching effect, but also react with other components exposed to the plasma, causing corrosive wear that can lead to particle generation and significant changes in the components used, which then require their replacement.

[0006] Quartz glass is often used for components that are subject to particularly high loads due to its high chemical resistance to many substances used in manufacturing processes and its relatively high temperature resistance. This is particularly true for etching chambers. However, in the case of fluorine-containing etching gases, the SiO2 in the quartz glass reacts with the reactive fluorine to form SiF4. The boiling point of SiF4 is -86°C, so this compound easily transitions to the gas phase, which is accompanied by severe corrosion and particle formation on the surface of the quartz glass.

[0007] A known approach to etch quartz by adding fluorine is doping, where the element added to the quartz glass forms a compound with the halide gas used, which has a higher sublimation temperature or a higher boiling point than the silicon halide formed in the quartz glass. The glass network formed thereby has a reduced etching rate.

[0008] Doping can involve adding oxides of Sm, Eu, Yb, Pm, Nd, Ce, Tb, Gd, Ba, Mg, Y, Tm, Dy, Ho, Er, Cd, Co, Cr, Cs, and / or Zr, which can lead to the destruction of the silica glass network.

[0009] Specifically, the SiO2 network that constitutes the quartz glass is broken and opened by the incorporation of secondary elements, often forming locally non-bridging oxygen atoms with weak bonding strength. This undesirable phenomenon is particularly unfavorable under etching conditions. Therefore, the addition of secondary elements can significantly increase the etching rate of the glass locally and reduce its durability.

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

[0011] A known doped glass mixture is composed of 20% by weight of MgO, 20% by weight of Al2O3, and 60% by weight of SiO2, and is called MAS glass. During the etching process with fluorine-containing etching gas, the glass mixture reacts with reactive fluorine to form MgF2. The boiling point of MgF2 is above 2200°C, so it hardly enters the gas phase, which minimizes the etching rate with reduced corrosion on the surface of the glass mixture. Further doping, for example with MgF2, to further reduce the etching rate is also known from the prior art (WO 2022075687).

[0012] A drawback of known MAS glass production is that material inhomogeneities often occur when melting the magnesium, aluminum, and silicon oxide components to produce the glass. These inhomogeneities can arise from insufficient mixing of the raw materials, as well as from segregation or local crystallization during the manufacturing process. These material inhomogeneities also result in locally different etching rates and thus inhomogeneous etch removal. This increases the risk of particle formation during the plasma etching process. A clear qualitative indicator of inhomogeneity is the presence of striae or cloudy glass regions. A very good quantitative method for detecting material inhomogeneities due to different etching rates is to measure the surface roughness of the glass after the etching process. The surface topology very accurately reflects the spatial distribution of the inhomogeneities and the associated inhomogeneity of the etching rate.

[0013] For plasma etching with fluorine-containing plasma, materials are required that have a low etching rate and high etching uniformity, and thus exhibit low particle emissions during the etching process. From the prior art, materials of the XO-Al2O3-SiO2 (X = alkaline earth metals, in particular Mg, Ca, and Ba) type are known that have relatively low etching rates. However, these materials often have the disadvantage that they have low etching uniformity, which may result in particle emissions during the etching process.

[0014] Therefore, it is an object of the present invention to overcome the drawbacks of the prior art. In particular, it is desirable to easily provide MAS glasses that are homogeneous and exhibit minimal crystallization and segregation upon curing. Furthermore, it is desirable for the MAS glasses to have reduced etching rates and high etching uniformity.

[0015] These problems have surprisingly been solved by a method for producing an MAS glass according to claim 1 and an MAS glass according to claim 10.

[0016] Advantageous further configurations are set forth in the dependent claims.

[0017] The MAS glass produced by the method according to the invention has the advantage that the glass is highly homogeneous, thereby preventing crystallization and separation. Furthermore, the MAS glass according to the invention has a reduced etching rate and high etching homogeneity. These advantageous properties can be reliably achieved even when the dimensions of the MAS glass or component are larger.

[0018] In the following, numerous specific details are set forth to provide a comprehensive understanding of the present subject matter, but it will be apparent to one skilled in the art that the present subject matter may be practiced or reproduced without these specific details.

[0019] Where features of different embodiments are compatible, all features of one embodiment can be combined with features of other embodiments.

[0020] The terminology used in the description of this disclosure merely serves to describe particular embodiments and should not be understood as limiting the subject matter. As used herein and in the claims, the singular forms "one," "an," and "the" should be understood to include the plural, unless the context clearly dictates otherwise. The converse is also true, i.e., the plural includes the singular. It is also self-evident that the term "and / or," as used herein, refers to and includes any possible combination of one or more of the associated listed elements. Furthermore, it is self-evident that the terms "comprise," "include," "comprise," and / or "comprises," when used in the specification and claims, specify the presence of stated features, steps, operations, elements, and / or components, but do not exclude the presence of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0021] In this specification and claims, the terms "comprises," "comprises," and / or "comprises" can also mean "consisting of," i.e., excluding the presence or addition of one or more other features, steps, operations, elements, components, and / or groups.

[0022] The present invention provides a method for producing MAS glass, comprising: a) mixing 10-40 mol% MgO, 5-30 mol% Al2O3, and 40-70 mol% SiO2 or precursors of these raw materials; b) melting the mixture from step a); c) cooling the melt from step b) and grinding it to particles with a diameter of less than 10 mm, preferably less than 5 mm, particularly preferably less than 2 mm; d) heating and melting the particles from step c); e) cooling the melt from step d); The present invention relates to a method characterized by:

[0023] By precursors of these raw materials are preferably understood the corresponding hydroxides and / or carbonates of MgO and Al2O3.

[0024] In a preferred embodiment, the method according to the invention is characterized in that steps c), d) and e) are carried out multiple times, and the melt in step c) is the melt previously produced in each step e). Multiple times means two, three, four, five, etc. By carrying out steps c), d) and e) multiple times, the homogeneity can be further improved.

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

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

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

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

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

[0030] Rapid means, for example, cooling at more than 75 K per minute, preferably more than 90 K per minute and less than 120 K per minute. Slow means, for example, cooling at less than 5 K per minute, preferably less than 2.5 K per minute and more than 0.5 K per minute.

[0031] Rapid cooling to a temperature range of 600-900°C has the advantage that the risk of crystallization is minimized, thereby further avoiding the formation of inhomogeneities. Slow cooling to room temperature then avoids the formation of stresses or cracks.

[0032] In a preferred embodiment, the method according to the invention is characterized in that the heating of the mixture in steps b) and / or d) 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 the cooling of the mixture in step e) is carried out in a steel mould coated with a mould release agent in a cooling furnace.

[0034] In a preferred embodiment, the method according to the invention is characterized in that less than 0.01 mol % of material additives comprising fluorine compounds and / or yttrium compounds are added during the production of the MAS glass.

[0035] Furthermore, the present invention relates to MAS glasses obtainable by the method described above.

[0036] In this regard, all definitions and preferred embodiments given above for the method according to the invention apply equally to the MAS glasses obtainable by the method described above.

[0037] In a preferred embodiment, the MAS glass obtained by the method according to the invention described above comprises 10 to 40 mol % MgO, 5 to 30 mol % Al2O3, and 40 to 70 mol % SiO2, is X-ray amorphous, and the surface of the glass has, after the etching process described below, an average roughness value (R a ) and has an average roughness value (R a ) determined in accordance with ISO 4287-1:1984.

[0038] In a preferred embodiment, the MAS glass obtained by the method according to the invention described above has a surface roughness (R ) of less than 100 nm, preferably less than 70 nm, particularly preferably less than 50 nm, very particularly preferably less than 35 nm, after the etching process described below. z ) and the average roughness depth (R z ) determined in accordance with ISO 4287-1:1984.

[0039] In the context of the present invention, etching uniformity refers to local variations in etching behavior. The smaller the local variations in etching behavior, the higher the etching uniformity of the MAS glass. Etching uniformity can be quantitatively determined based on normalized measurements of the surface roughness (Ra and Rz values) of the MAS glass after a defined etching process.

[0040] The etching uniformity is expressed by the surface roughness after the etching process, and is expressed as the average roughness value (R a ) and average roughness depth (R z ) can be quantitatively expressed using variables such as R a and R z A low value of R indicates high etching uniformity. a is defined as the average distance from the measurement point on the surface to the center line. zis defined as the average value of the individual roughness depths of five consecutive individual measurement sections in the roughness profile. a and R z The determination is made in accordance with ISO 4287-1:1984.

[0041] Determination of the etching uniformity of MAS glass can be achieved by the following steps (specific etching process): 1. cleaning the MAS glass, 2. masking specific glass areas with Kapton tape, and 3. the etching process.

[0042] Cleaning of MAS glass involves the following wet chemical steps: 1. Ultrasonic 100%, Tickopur R33 (5%) for 10 minutes 2. Solvent cleaning with acetone and isopropanol, and 3. Rinse with deionized water and dry This is done by:

[0043] Tickopur R33 (5%) is a general-purpose ultrasonic cleaner containing 5-15% anionic surfactants, 5-15% phosphates, less than 5% nonionic surfactants, less than 5% silicates, and complexing agents.

[0044] Masking of specific glass areas with Kapton tape is accomplished by partially covering specific areas of the substrate with plasma-stable Kapton foil.

[0045] The etching process for smoothing the surface of MAS glass according to the present invention is carried out in a Sentech Si-500 apparatus, with the following parameters adjusted in the associated execution software as follows: 1.ICP500W, 2.HF bias 200W, 3. Drossel 100% (0.25Pa), 4. CHF 330sccm, 5. Etching time (cycle, 2 minutes etching, 3 minutes cooling), 6.He backside cooling 1000Pa, 7. Heating power 0%, and 8.Al sampling.

[0046] The surface roughness of the glass was determined according to ISO 4287-1:1984. The etching depth was determined by measuring the etching profile (i.e., the cross section of the etching stage) in an optical microscope. The etching rate was determined as a function of time relative to the etching profile.

[0047] Compared to undoped silica glass, the MAS glass according to the invention exhibits an approximately 8 times lower etching rate (nm / min) with equally good etching uniformity (Ra and Rz values). The MAS glass according to the invention has better etching uniformity (Ra and Rz values) compared to known MAS glasses. These advantageous properties are surprisingly obtained by using the method according to the invention.

[0048] In a preferred embodiment, the MAS glass obtained by the method according to the invention described above is characterized in that it is X-ray amorphous.

[0049] X-ray amorphous MAS glasses are glasses that do not have extended domains of crystalline long-range order, and therefore, corresponding examination leads only to highly dispersed X-ray reflections (so-called glass hills).

[0050] X-ray amorphous in the context of the present invention means the absence of crystalline regions larger than 10 nm in the MAS glass, which can be determined, for example, by diffractometry.

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

[0052] In a preferred embodiment, the MAS glass obtained by the method according to the invention described above is characterized in that it contains less than 0.01 mol % of material additives comprising fluorine compounds and / or yttrium compounds, which has the advantage that the risk of forming local inhomogeneities during the material manufacturing process is further minimized.

[0053] The homogeneity of optical substrates is characterized by refractive index variations, which result in distortions of the transmitted wavefront and polarization transfer effects. A high degree of homogeneity or minimal variation is particularly important for applications using high-power lasers. Homogeneity variations arise from the melting process during material production. Mixing imprecision and thermodynamic imbalances result in density variations. Additionally, distortions can occur during the cooling and tempering processes. Inhomogeneities exist in the form of gross inhomogeneities (deviations in refractive index throughout the glass piece) or striae (locally limited deviations in homogeneity in the glass with lengths of 0.1 mm to 2 mm). Inclusions are foreign particles present in optical glass that can be caused, for example, by contamination during melting, incomplete melting of the substrate batch, and poorly soluble wall materials. Additionally, gas bubbles can occur due to reactions during glass melting. These bubbles are almost completely removed during the finishing steps of the glass melting process.

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

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

[0056] This has the advantage that it simplifies uniform hardening and the formation of an X-ray amorphous glass, which is difficult to crystallize.

[0057] The glass structure and the incorporation of individual cations vary depending on the MgO / Al2O3 ratio. A high proportion of Mg(II) leads to the formation of non-bridging oxygens (NBOs), which reduces the viscosity. The proportion of non-bridging oxygens then depends on the MgO / Al2O3 ratio. When this ratio is less than or equal to 1, magnesium is incorporated as a glass former, i.e., one Mg(II) ion is substituted for two [AlO4] ions. - It stabilizes tetrahedra (four-bonded aluminum). If the Mg(II) proportion is further increased, Mg(II) is incorporated as a glass transformer, which leads to the formation of NBOs and a corresponding decrease in viscosity.

[0058] The proportion of Al atoms present in quadruple coordination is determined using MQMAS-NMR (multiple quantum magic angle spinning nuclear magnetic resonance spectroscopy) measurements.

[0059] For example, NMR spectra are recorded on a Varian VNMRs 11.7T NMR spectrometer using a Varian 1.6mm T3-MAS-NMR probehead at a spinning frequency of 35kHz. 27 AI-MAS-NMR spectra were also generated at a magnetic field of 7 T (Bruker Avance III spectrometer; 4 mm triple resonance probehead; spinning frequency 10 kHz).

[0060] In a preferred embodiment, the MAS glass according to the invention, obtained by the method according to the invention described above, has a coefficient of linear expansion (CTE) of 3.0×10 -6 K -1 above (300 to 600°C), preferably 4.0 × 10 -6 K -1 More than (300 to 600°C), more preferably 4.5 × 10 -6 K -1 It is characterized by being above (300 to 600°C).

[0061] The coefficient of linear expansion (CTE) is a material property that describes the behavior of a material in terms of its change in dimensions with a change in temperature. The effect involved is thermal expansion. Because thermal expansion in many materials does not occur equally across all temperature ranges, the coefficient of thermal expansion itself is also temperature dependent and is therefore stated relative to a reference temperature or temperature range.

[0062] The determination of the coefficient of linear expansion (CTE) is carried out in accordance with ISO 7991-1998.

[0063] In a preferred embodiment, the MAS glass according to the invention, obtainable by the method according to the invention described above, has a glass transition temperature (T g ) is characterized by having.

[0064] Glass transition temperature (T g ) is the material property at which a glass exhibits the greatest change in deformability. The glass transition temperature separates the brittle energy-elastic region below, where the material exists as a glass, from the soft entropy-elastic region above.

[0065] Glass transition temperature (T g ) is determined in accordance with ISO 7884-8:1998.

[0066] A lower glass transition temperature has the advantage that the oxides utilized in making the glass can be mixed at lower temperatures and the glass produced can be deformed at lower temperatures.

[0067] In a preferred embodiment, the MAS glass according to the invention obtained by the method according to the invention described above is characterized in that it is not fire-polished.

[0068] Fire polishing is costly and can result in distortion of the component shape, so it is considered a disadvantage.

[0069] After polishing the glass member, the glass surface is often rough and matte, so flame polishing is applied to obtain a smooth surface by heating and smoothing the surface. In this preferred embodiment according to the present invention, flame polishing is not required.

[0070] In a preferred embodiment, the MAS glass according to the invention, obtainable by the method according to the invention described above, 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 the plasma etching rate of quartz glass.

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

[0072] Plasma etching depth is determined by measuring the etching profile (i.e., cross section of the etching stage) under an optical microscope. The plasma etching rate defines the etching rate obtained from etching a material using plasma. The etching rate is defined as the thickness of the material to be etched removed per unit time. The relative etching rate is obtained from the ratio of the etching rates of the materials being compared. The etching rate is determined by measuring the etching profile over a certain time range.

[0073] Furthermore, the present invention relates to a component comprising the MAS glass described above.

[0074] In this case, all definitions and preferred embodiments given above for the method according to the invention and the MAS glass according to the invention apply analogously to the components.

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

[0076] In this case, all definitions and preferred embodiments given above for the method according to the invention and the MAS glass according to the invention apply equally to the use of the components.

[0077] In the following, the invention will be explained in more detail on the basis of non-limiting examples.

[0078] It will be apparent to those skilled in the art that CaO and its precursors may be used in place of MgO and its precursors with equivalent results.

[0079] Example The glasses were produced at temperatures of approximately 1600–1700°C. 300 g of the mixtures listed in Table 1 were melted in a Pt crucible and a Pt / Rh crucible, respectively. The production conditions are summarized in Tables 1 and 2. First, the glass was melted at temperature T1 for duration t1. The cooled melt was then crushed and melted again at temperature T2 for duration t2. After the second melting step, the melt was poured into a metal mold. The melting time depended primarily on the duration required to form a transparent, bubble-free melt. Correspondingly, longer times (and higher temperatures) were required for higher-melting-point compositions. The amount of glass varied for some compositions, in part due to special geometries requiring very high crucible filling. Correspondingly, the melting process also took longer for these compositions.

[0080] It was found that glass No. 1 (Tables 1 and 2) could be melted at a temperature of 1560 °C. However, it takes a relatively long time for the laboratory melt to become bubble-free. To ensure better homogeneity and allow the glass to be poured better, a temperature of 1650 °C was chosen for production. The glass was then poured into a steel mold coated with a release agent and transferred to a cooling furnace, which was preheated to 810 °C and switched off to ensure slow cooling (1–2 K / min) to room temperature.

[0081] [Table 1]

[0082] [Table 2]

[0083] A summary of the properties determined by dilatometry (heating rate 5 K / min) can be found in Table 3. It is known that glasses with low CTE often have high glass transition temperatures. This is mostly a problem for bonding applications in the field of fuel cells, where high CTE and high glass transition temperatures are equally required. However, in MAS systems, T g It has been found that the CTE and the SiO2 content do not follow exactly the same compositional trend. 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, and therefore the maximum glass transition temperature does not occur at the highest SiO2 content. This is also due to the fact that the glass structure and the incorporation of individual cations change depending on the MgO / Al2O3 ratio. A high proportion of Mg(II) leads to the formation of non-bridging oxygens (NBOs), which reduces the viscosity. However, Mg(II) can be incorporated into the glass not only as a network transformer but also as a network former. This proportion depends on the MgO / Al2O3 ratio.

[0084] When this ratio is less than 1, magnesium is incorporated as a network former, i.e., one Mg(II) ion is connected to two [AlO4] - If the Mg(II) proportion is further increased, Mg(II) is incorporated as a network transformation product, which leads to the formation of NBOs and a corresponding decrease in viscosity.

[0085] [Table 3]

[0086] To determine the crystallization tendency, glass pieces were melted into corundum crucibles. To do so, the crucibles were filled with glass at room temperature and then transferred to a furnace preheated to 1700 ° C. After a few minutes, the furnace was cooled at 5 K / min. This cooling rate can be maintained up to about 1000 ° C. At lower temperatures, the furnace cools correspondingly more slowly. The resulting MAS glasses are transparent and X-ray amorphous.

[0087] Determination of the etching uniformity of MAS glass can be achieved by the following steps: 1. cleaning the MAS glass, 2. masking specific glass areas with Kapton tape, and 3. the etching process.

[0088] Cleaning of MAS glass is carried out by the following wet chemical steps: 1. Ultrasonic 100%, Tickopur R33 (5%) for 10 minutes 2. Solvent cleaning with acetone and isopropanol, and 3. Rinse with deionized water and dry.

[0089] Tickopur R33 (5%) is a general-purpose ultrasonic cleaner containing 5-15% anionic surfactants, 5-15% phosphates, less than 5% nonionic surfactants, less than 5% silicates, and complexing agents.

[0090] Masking of specific glass areas with Kapton tape is accomplished by partially covering specific areas of the substrate with plasma-stable Kapton foil.

[0091] The etching process for smoothing the surface of MAS glass according to the present invention is carried out in a Sentech Si-500 apparatus, with the following parameters adjusted in the associated execution software as follows: 1.ICP500W, 2.HF bias 200W, 3. Aperture 100% (0.25 Pa), 4. CHF 330sccm, 5. Etching time (cycle, 2 minutes etching, 3 minutes cooling), 6.He backside cooling 1000Pa, 7. Heating power 0%, and 8.Al sampling.

[0092] The total duration of the etching process is 40 minutes.

[0093] The surface roughness of the glass was determined according to ISO 4287-1:1984. The etching depth was determined by measuring the etching profile (i.e., cross-section of the etching stage) in an optical microscope. The etching rate was determined as a function of time with respect to the etching depth.

[0094] [Table 4]

[0095] From Table 4 it is clear that the MAS glasses according to the invention have significantly improved etch rates and comparable etch uniformity compared to the undoped quartz reference sample.

Claims

1. 1. A method for producing MAS glass, comprising: a) 10 to 40 mol% MgO, 5 to 30 mol% Al ２ O ３ and 40 to 70 mol% of SiO ２ or mixing precursors of these raw materials; b) melting the mixture from step a); c) cooling the melt from step b) and grinding it to particles with a diameter of less than 10 mm, preferably less than 5 mm, particularly preferably less than 2 mm; d) heating and melting the particles from step c); e) cooling the melt from step d); A method characterized by:

2. 2. The method according to claim 1, wherein steps c), d), and e) are carried out multiple times, and each cooled melt in step c) is a melt previously produced by step e).

3. 3. A method according to claim 1 or 2, characterized in that the mixture in steps b) and / or d) is heated to a temperature of 1200 to 2000°C, preferably to a temperature of 1500 to 1750°C.

4. 4. A method according to any one of claims 1 to 3, characterized in that the duration of step b) is between 0.1 and 10 hours, preferably between 0.1 and 7 hours.

5. 5. A method according to any one of claims 1 to 4, characterized in that the duration of step d) is between 0.1 and 10 hours, preferably between 0.1 and 7 hours.

6. 6. The process according to claim 1, wherein the mixture from step d) is cooled in step e) to a temperature below 25°C.

7. 7. The method according to claim 1, wherein the mixture from step d) is first rapidly cooled in step e) to a temperature of 600-900°C and then slowly cooled by a temperature below 25°C.

8. 8. The method according to claim 1, wherein the heating of the mixture in steps b) and / or d) is carried out in a Pt crucible and / or a Pt / Rh crucible.

9. 9. The method according to claim 1, wherein the cooling of the mixture in step e) is carried out in a steel mold coated with a mold release agent in a cooling furnace.

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

11. The MAS glass contains 10 to 40 mol % of MgO, 5 to 30 mol % of Al ２ O ３ and 40 to 70 mol% of SiO ２ and is X-ray amorphous, and the surface of said MAS glass, after the etching process specified in the present specification according to steps 1 to 3, has an average roughness value (R ａ ) and the average roughness value (R ａ 11. The MAS glass of claim 10, wherein the tensile strength (Tb) of the glass is determined according to ISO 4287-1:1984.

12. 20 to 40 mol% MgO, 5 to 30 mol% Al ２ O ３ and 40 to 70 mol% of SiO ２ , preferably 25 to 35 mol % MgO, 10 to 25 mol % Al ２ O ３ and 50 to 65 mol % of SiO ２ 12. The MAS glass of claim 10 or 11, comprising:

13. 13. The MAS glass of claim 10, wherein the MAS glass contains less than 0.01 mol % of material additives comprising fluorine compounds and / or yttrium compounds.

14. 14. The MAS glass according to claim 10, wherein more than 80%, preferably more than 90%, of the Al atoms contained therein are present in a four-fold coordination with oxygen.

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

16. 16. The MAS glass of any one of claims 10 to 15, characterized in that the MAS glass has a glass transition temperature of less than 900°C.

17. 17. The MAS glass according to claim 10, characterized in that the relative plasma etching rate of the MAS glass is more than 50%, preferably more than 70%, particularly preferably more than 85% lower than the relative plasma etching rate of quartz glass.

18. Component comprising a MAS glass according to any one of claims 10 to 17.

19. The component of claim 18, wherein the component is not fire polished.

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

21. 21. Use according to claim 20 in an etching chamber.

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