Glass-ceramics with specific thermal expansion behavior

Abstract

To provide a glass-ceramic improved in thermal expansion behavior, and the use thereof in a precision component.SOLUTION: An LAS glass-ceramic has an average coefficient of thermal expansion CTE at 0-50°C of at most 0±0.1×10-6 / K and a thermal hysteresis at least in the temperature range from 15°C to 35°C of less than 0.1 ppm. The LAS glass-ceramic contains following components (in units of mol% based on oxide): SiO2 of 60 to less than 70; Li2O of 7 to 9.6; MgO+ZnO of more than 0.5 to 1.5; R2O of more than 0.5, where R2O may be Na2O and / or K2O and / or Cs2O and / or Rb2O; and also contains a nucleating agent with a content of 1.5 to 6 mol%, where the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, WO3, and HfO2.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to glass-ceramics which exhibit specific thermal expansion behavior while also exhibiting good meltability, formability and ceramizability, and to the use of the glass-ceramics according to the invention in precision components, in particular precision components for lithography, in particular EUV lithography.

[0002] Background of the Invention Low thermal expansion or low CTE (Coefficient of Thermal Expansion) materials and precision components are already known from the prior art.

[0003] Known precision component materials with low thermal expansion near room temperature include ceramics, Ti-doped quartz glass, and glass ceramics. Low-thermal expansion glass ceramics are, in particular, lithium aluminum silicate glass ceramics (LAS glass ceramics), as described in, for example, U.S. Pat. Nos. 4,851,372, 5,591,682, EP 587979, 7,226,881, 7,645,714, DE 102004008824, and DE 102018111144. Another precision component material is cordierite ceramic or cordierite glass ceramics.

[0004] Such materials are often used in precision components that must meet particularly stringent requirements regarding their properties (e.g., mechanical, physical, and optical properties). They are used in particular in ground- and space-based astronomy and Earth observation, LCD lithography, microlithography and EUV lithography, metrology, spectroscopy, and measurement techniques. In this case, it is necessary for the components to exhibit particularly low thermal expansion, depending on the specific application.

[0005] Generally, the thermal expansion of materials is measured by a static method, in which the length of a specimen is measured at the beginning and end of a specific temperature range, and the average coefficient of thermal expansion (α) or CTE (Coefficient of Thermal Expansion) is calculated from the difference in these lengths. In this case, the CTE is expressed as the average value for this temperature range, for example, CTE(0;50) or α(0;50) for the temperature range 0°C to 50°C.

[0006] To meet ever-increasing demands, materials have been developed with CTEs more tailored to the application of the components they will be made from. For example, the average CTE can be optimized not only for the standard temperature interval CTE(0;50) but also for a temperature interval near the actual application temperature, e.g., the 19°C-25°C interval for certain lithography applications, i.e., CTE(19;25). In addition to determining the average CTE, the thermal expansion of the specimen can also be determined over a very small temperature interval and expressed as a CTE-T curve. In particular, such a CTE-T curve can have zero crossings at one or more temperatures, particularly at or near the intended application temperature. At the zero crossings of the CTE-T curve, the relative length change with temperature is particularly small. For some glass-ceramics, the zero crossings of such CTE-T curves can be shifted to the application temperature of the component by appropriate temperature treatment. To minimize the length change of the component when temperature changes are small, it is desirable to minimize not only the absolute value of the CTE but also the slope of the CTE-T curve near the application temperature. The optimization of the CTE or thermal expansion is usually achieved for these particular zero-expansion glass-ceramics by varying the ceramization conditions for the same composition.

[0007] One of the adverse effects in known precision components and materials, particularly in glass ceramics such as LAS glass ceramics, is "thermal hysteresis," hereafter abbreviated as "hysteresis." Hysteresis, as used herein, refers to the fact that the change in length of a specimen when heated at a constant heating rate differs from the change in length of the specimen when subsequently cooled at a constant cooling rate, even if the absolute values ​​of the cooling rate and heating rate are identical. A typical hysteresis loop is obtained by plotting the change in length against the heating or cooling temperature. The shape of the hysteresis loop also depends on the rate of temperature change. The faster the temperature change is performed, the more pronounced the hysteresis effect becomes.The hysteresis effect reveals that the thermal expansion of LAS glass-ceramics depends on temperature and time, e.g., on the rate of temperature change, and this has already been described in several specialist publications, e.g., O. Lindig and W. Pannhorst, “Thermal expansion and length stability of ZERODUR® in dependence on temperature and time”, APPLIED OPTICS, Vol. 24, No. 20, October 1985; R. Haug et al., “Length variation in ZERODUR® M in the temperature range from −60°C to +100°C”, APPLIED OPTICS, Vol. 28, No. 19, October 1989; R. Jedamzik ​​et al., “Modeling of the thermal expansion behavior of ZERODUR® at arbitrary temperature profiles”, Proc. SPIE Vol. 7739, 2010; D.B. Hall, “Dimensional stability tests over time and temperature for several low-expansion glass "Applied Optics, Vol. 35, No. 10, April 1996,"

[0008] Because the length change of glass-ceramics that exhibit thermal hysteresis lags behind or even precedes the temperature change, these materials or precision components made from them exhibit disruptive isothermal length changes, i.e., the material undergoes length changes even after a temperature change, when the temperature is already held constant (so-called "isothermal hold"), and this continues until a steady state is reached. If the material is then heated and cooled again, the same effect occurs again.

[0009] With previously known LAS glass-ceramics, it has not been possible to eliminate the effects of thermal hysteresis while maintaining other properties by changing the ceramization conditions at a constant composition.

[0010] For the properties of materials used in precision components, especially glass ceramics, the temperature range of 0°C to 50°C, especially 10°C to 35°C or 19°C to 25°C, is often important, where 22°C is generally referred to as room temperature. Glass ceramics are used, for example, in precision components for lithography, especially EUV lithography.

[0011] EUV lithography (hereinafter also referred to as EUVL) is a photolithography method that uses electromagnetic radiation, usually between 5 nm and 50 nm (soft X-rays), in particular electromagnetic radiation with a wavelength of 13.5 nm (91.82 eV). This is the so-called "extreme ultraviolet" (EUV). This range of the electromagnetic spectrum is completely absorbed by almost all materials. Therefore, in contrast to DUV lithography (Deep ultraviolet, e.g., 248 nm and / or 193 nm), optically transparent photomasks (hereinafter also referred to as reticles, reticle masks, or masks, English: "Reticles" or "Reticle Masks" or "Photomasks" or "Masks") cannot be used, and reflective multilayer stack systems on low-thermal-expansion photomask substrates (hereinafter also referred to as reticle substrates or mask substrates, English: "Reticle Mask Blank" or "Photo-Mask Blank" or "Mask Blank" or "Substrate") must be used as photomasks. However, the disadvantage of using reflective photomasks is that the maximum reflectivity of the multilayer stack in the EUV range is relatively low, typically less than 70%. Radiation that is not reflected by the photomask is absorbed by the photomask and conducted in the form of heat to the photomask substrate and, in some cases, to the photomask carrier (hereinafter also referred to as the "reticle carrier" or "reticle stage" or "mask carrier" or "mask stage", English: "Reticle Stage" or "Photomask Stage" or "Mask Stage"), which can cause its temperature to rise, especially as the exposure time increases.

[0012] However, even slight thermally induced deformation of the photomask can lead to imaging errors on the irradiated wafer and ultimately to yield loss during chip manufacturing. Therefore, to prevent such local deformation or distortion of the photomask substrate, it is necessary to use a material with low thermal expansion or low CTE (Coefficient of Thermal Expansion) for the photomask substrate.

[0013] This is all the more true as the average power of EUV radiation sources used in EUV lithography will increase in the future, for example, by higher repetition rates and / or higher single-pulse energies to improve throughput, thereby increasing the thermal load on the photomask and possibly even the photomask carrier. This will increase the importance of active cooling concepts for the photomask and / or photomask carrier, which may further accelerate temperature variations, especially in the photomask and / or photomask carrier. It must also be taken into account that the thermal load on the photomask and / or photomask carrier is not constant but varies due to various factors, particularly inconsistencies in exposure times due to, for example, loading a new photomask into the photomask carrier or downtime due to process stalls. The aforementioned thermally induced deformations can be partially compensated for by compensation mechanisms within the overall optical system of the lithography apparatus, for example, in beam shaping of the exposure. However, since this compensation is limited, it is desirable to minimize their individual contribution to (imaging) "errors." Here, not only the thermally induced deformation of the material during exposure must be taken into account, but also its thermal behavior over time (thermal hysteresis). However, materials with relatively high thermal hysteresis make such compensation more difficult, and therefore more difficult to prevent unwanted thermally induced imaging errors in the photomask.

[0014] Furthermore, other EUVL precision components that have high demands on thermal properties include, in particular, the EUVL mirrors in the optical system of the EUVL device and the wafer carrier (hereinafter also referred to as the "wafer stage") on which the (Si) wafer to be exposed is placed.

[0015] Because many applications of precision components, especially those in EUV lithography, take place in the temperature range from above 0 °C to nearly room temperature, materials with thermal hysteresis effects or isothermal length changes are disadvantageous because they can cause optical disturbances in optical components such as photomask substrates, photomask carriers, lithography mirrors, and astronomical and space-based mirrors, which can reduce the measurement accuracy of other precision components made of glass-ceramics used in metrology (e.g., precision scales, interferometer reference plates, etc.).

[0016] Several known materials, such as ceramics, Ti-doped silica glass, and some glass-ceramics, have an average coefficient of thermal expansion (CTE) of 0±0.1×10 -6 / K (corresponding to 0±0.1 ppm / K). Materials with such low average CTEs in the aforementioned temperature range are referred to as zero-expansion materials within the meaning of the present invention. However, glass-ceramics, particularly LAS glass-ceramics with such optimized average CTEs, typically exhibit thermal hysteresis in the temperature range of 15°C to 35°C. This means that, particularly when used near room temperature (i.e., 22°C), such materials experience disruptive hysteresis effects, which impair the accuracy of precision components manufactured from such materials. Therefore, glass-ceramic materials that do not exhibit significant hysteresis at room temperature have been developed (see U.S. Pat. No. 4,851,372). However, this effect is not eliminated, but merely shifted to lower temperatures. Therefore, these glass-ceramics exhibit significant hysteresis at temperatures below 15°C, which can still be disruptive. Therefore, to characterize the thermal hysteresis of a material within a given temperature range, the thermal behavior of the material at each temperature point within that temperature range is considered within the scope of the present invention. Furthermore, there are glass-ceramics that do not exhibit significant hysteresis at 22°C and 5°C, but these glass-ceramics have an average CTE(0;50) greater than 0±0.1 ppm / K and are therefore not zero-expansion glass-ceramics in the sense of the above definition.

[0017] Another requirement for glass-ceramic materials is good solubility of the glass components as well as easy melting and homogenization of the base glass melt in large-scale production plants, which - after subsequent ceramization of the glass - allows the high demands on the glass-ceramic to be met with regard to CTE uniformity, internal quality, in particular low number of inclusions (especially bubbles), low striae level and polishability.

[0018] It was therefore an object of the present invention to provide glass-ceramics with improved expansion behavior. Another object was to provide glass-ceramics that can be mass-produced and have zero expansion and reduced thermal hysteresis, particularly in the temperature range of 15°C to 35°C, and precision components manufactured from this material. Another object was to provide a material that allows for higher imaging accuracy with precision components made from this material, particularly precision components for EUV lithography.

[0019] The above problems are solved by the subject matter of the claims.The invention has various aspects.

[0020] According to one aspect of the present invention, there is provided an LAS glass ceramic having an average coefficient of thermal expansion (CTE) of at most 0±0.1×10 at 0 to 50°C. -6 / K, and has a thermal hysteresis of less than 0.1 ppm over a temperature range of at least 15 to 35°C, and contains (in mole % on an oxide basis) the following components: SiO260~<70 Li2O 7~9.6 MgO+ZnO >0.5~1.5 R2O > 0.5, where R2O may be Na2O and / or K2O and / or Cs2O and / or Rb2O, Nucleating agent: 1.5-6 mol% content, wherein the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, WO3, HfO2; The present invention provides a LAS glass-ceramic comprising:

[0021] According to a further aspect, the invention relates to the use of the glass-ceramics according to the invention as substrates for precision components, in particular for precision components for EUV lithography.

[0022] According to a further aspect, the invention relates to the use of the LAS glass ceramics according to the invention in precision parts, in particular in metrology, spectroscopy, measuring technology, lithography, astronomy or Earth observation from outer space, for example as mirrors or mirror supports for segmented or integrated astronomical telescopes, or also as lightweight or ultra-lightweight mirror substrates, for example for space-based telescopes, or as high-precision structural elements, for example for distance measurements in space, or as optics for Earth observation, as precision elements, for example standards for precision measuring technology, precision scales, reference plates in interferometers, as mechanical precision parts, for example for ring laser gyroscopes, as coil springs in the watch industry, as mirrors and prisms, for example in LCD lithography, as mask holders, wafer stages, reference plates, reference frames and grid plates, for example in microlithography and EUV (extreme UV) microlithography where reflective optics are used, and also as mirrors and / or photomask substrates or reticle mask blanks or photomask carriers in EUV microlithography.

[0023] According to another aspect, the invention relates to a precision component comprising the LAS glass ceramic according to the invention. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 shows CTE-T curves of low linear thermal expansion materials, e.g. for precision components, known from the prior art. [Figure 2] Figure 1 shows the hysteresis behavior of three glass-ceramic samples determined using the same method as used in the present invention. These figures are adapted from R. Jedamzik ​​et al., "Modeling of the thermal expansion behavior of ZERODUR® at arbitrary temperature profiles," Proc. SPIE Vol. 7739, 2010. [Figure 3]FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of known or non-inventive glass-ceramic materials that can be used to manufacture known precision components and that exhibit a thermal hysteresis of more than 0.1 ppm at least in the temperature range of 15-35° C. [Figure 4] FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of known or non-inventive glass-ceramic materials that can be used to manufacture known precision components and that exhibit a thermal hysteresis of more than 0.1 ppm at least in the temperature range of 15-35° C. [Figure 5] FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of known or non-inventive glass-ceramic materials that can be used to manufacture known precision components and that exhibit a thermal hysteresis of more than 0.1 ppm at least in the temperature range of 15-35° C. [Figure 6] FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of known or non-inventive glass-ceramic materials that can be used to manufacture known precision components and that exhibit a thermal hysteresis of more than 0.1 ppm at least in the temperature range of 15-35° C. [Figure 7] FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of known or non-inventive glass-ceramic materials that can be used to manufacture known precision components and that exhibit a thermal hysteresis of more than 0.1 ppm at least in the temperature range of 15-35° C. [Figure 8] FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of known or non-inventive glass-ceramic materials that can be used to manufacture known precision components and that exhibit a thermal hysteresis of more than 0.1 ppm at least in the temperature range of 15-35° C. [Figure 9]FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of prior art glass-ceramics that can be used to manufacture precision components and that exhibit thermal hysteresis of less than 0.1 ppm over at least the temperature range of 15-35° C. However, the steep curve transition indicates that the glass-ceramics are not zero-expansion. [Figure 10] FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of glass ceramics according to the present invention (compositions according to Examples 2 and 4 in Table 1) that can be used to manufacture precision components according to the present invention and that exhibit thermal hysteresis of less than 0.1 ppm at least in the temperature range of 15 to 35° C. [Figure 11] FIG. 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) of glass ceramics according to the present invention (compositions according to Examples 2 and 4 in Table 1) that can be used to manufacture precision components according to the present invention and that exhibit thermal hysteresis of less than 0.1 ppm at least in the temperature range of 15 to 35° C. [Figure 12] FIG. 1 shows a normalized Δl / l0-T curve (also referred to as a dl / l0 curve) of a glass ceramic according to the present invention (composition according to Example 2 in Table 1), and an auxiliary line for determining a parameter F as an index of flatness of the expansion curve in the temperature range of 0°C to 50°C. [Figure 13] FIG. 1 is a diagram showing a normalized Δl / l0-T curve of a known material that can be used to manufacture a known precision part, and an auxiliary line for determining a parameter F as an index of flatness of the expansion curve in the temperature range of -10°C to 70°C. [Figure 14] FIG. 1 is a diagram showing a normalized Δl / l0-T curve of a known material that can be used to manufacture a known precision part, and an auxiliary line for determining a parameter F as an index of flatness of the expansion curve in the temperature range of −10° C. to 80° C. [Figure 15] FIG. 1 shows a normalized Δl / l0-T curve of a known material that can be used to manufacture a known precision part, and an auxiliary line for determining a parameter F as an index of flatness of the expansion curve in the temperature range of −20° C. to 80° C. [Figure 16] FIG. 1 is a diagram showing a normalized Δl / l0-T curve of a known material that can be used to manufacture a known precision part, and an auxiliary line for determining a parameter F as an index of flatness of the expansion curve in the temperature range of -10°C to 70°C. [Figure 17] FIG. 1 shows normalized Δl / l0-T curves of known materials in the temperature range of −30° C. to +70° C. [Figure 18] FIG. 13 shows the CTE-T curve of the glass-ceramic of FIG. 12, which can be used to manufacture advantageous precision components and advantageously has a CTE "plateau." [Figure 19] FIG. 19 is a diagram showing the slope of the CTE-T curve in FIG. 18. [Figure 20] FIG. 1 shows the normalized Δl / l0-T curve of a glass-ceramic according to the invention (composition according to Example 2 of Table 1) and an auxiliary line for determining the alternative parameter f(20;40) as an index of the flatness of the expansion curve in the temperature range from 20°C to 40°C. [Figure 21] FIG. 1 shows the normalized Δl / l0-T curve of a glass-ceramic according to the invention (composition according to Example 2 of Table 1) and an auxiliary line for determining the alternative parameter f(20;70) as an index of the flatness of the expansion curve in the temperature range from 20°C to 70°C. [Figure 22] FIG. 1 shows the normalized Δl / l0-T curve of a glass-ceramic according to the invention (composition according to Example 4 of Table 1) and an auxiliary line for determining the alternative parameter f(-10;30) as an indicator of the flatness of the expansion curve in the temperature range from -10°C to 30°C.

[0025] The subject of the present invention is a LAS glass ceramic having an average coefficient of thermal expansion CTE between 0 and 50 °C of at most 0 ± 0.1 × 10 -6 / K, and has a thermal hysteresis of less than 0.1 ppm over a temperature range of at least 15°C to 35°C, and contains (in mole % on an oxide basis) the following components: SiO260~<70 Li2O 7~9.6 MgO+ZnO >0.5~1.5 R2O > 0.5, where R2O may be Na2O and / or K2O and / or Cs2O and / or Rb2O, Nucleating agent: 1.5-6 mol% content, wherein the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, WO3, HfO2; and LAS glass ceramics, including

[0026] According to the present invention, LAS glass-ceramics (hereinafter also referred to as glass-ceramics) are provided that combine several important properties, i.e., the glass-ceramics can be produced with high uniformity in large-scale production plants. Furthermore, the glass-ceramics have an average coefficient of thermal expansion (CTE) of at most 0±0.1×10 in the range of 0 to 50°C. -6 / K, i.e., zero thermal expansion. Furthermore, the glass-ceramics exhibit a thermal hysteresis of less than 0.1 ppm at least in the temperature range from 15°C to 35°C. Materials exhibiting such low hysteresis effects of less than 0.1 ppm in the aforementioned temperature range are hereinafter referred to as "hysteresis-free." As already explained above, the form of hysteresis depends on the rate of temperature change used to determine it. Therefore, within the scope of the present invention, references to hysteresis relate to a heating / cooling rate of 36 K / h, i.e., 0.6 K / min. The low thermal hysteresis in the aforementioned temperature range reduces the effort required to compensate for thermally induced deformation of precision components over time when the material is used in precision components, particularly EUV lithography components. In an advantageous embodiment, the LAS glass ceramic can be hysteresis-free at least in the temperature range of 15°C to 40°C, advantageously at least in the temperature range of 15°C to 45°C, preferably at least in the temperature range of 15°C to 50°C, or at least in the temperature range of 10°C to 35°C.

[0027] The CTE and thermal hysteresis characteristics are discussed in detail below.

[0028] According to the present invention, glass ceramics are understood to be inorganic, non-porous materials having a crystalline phase and a glassy phase, with the matrix, or continuous phase, usually being a glass phase. To produce glass ceramics, the components of the glass ceramic are first mixed, melted, refined, and poured to produce a so-called green glass. After cooling, this green glass is reheated and crystallized in a controlled manner (so-called "controlled volume crystallization"). The analytical chemical composition of the green glass is identical to that of the glass ceramic produced therefrom; ceramization changes only the internal structure of the material. Therefore, when the composition of a glass ceramic is mentioned below, the same applies to the precursor of the glass ceramic, i.e., the green glass.

[0029] The prior art has previously recognized that the use of the glass components MgO and ZnO, either in combination or individually, is necessary to achieve zero expansion, particularly in zero-expansion LAS glass ceramics, and to "flatten" the CTE-T curve of the material, i.e., to reduce the slope of the CTE-T curve over the temperature range. In unpublished DE 102022105929.4, the inventors discovered for the first time that these two components, MgO and ZnO, contribute to the development of thermal hysteresis over the temperature range. Therefore, to provide zero-expansion LAS glass ceramics that are hysteresis-free at least over the temperature range from 10°C to 35°C, it is important to limit the content of MgO and ZnO or to completely eliminate them. Thus, there has been a conflict between making LAS glass ceramics zero-expansion or hysteresis-free.

[0030] This inconsistency was resolved by the technical teaching of unpublished DE 102022105929.4 not only by largely eliminating the use of MgO and ZnO, but also by selecting the SiO2 and Li2O contents within predetermined ranges.

[0031] However, adjusting the expansion curve and thus the CTE of these zero-expansion, hysteresis-free glass-ceramics can be problematic. The expansion curves of glass-ceramics with low MgO+ZnO contents are, in part, strongly curved, particularly in the temperature range from 0°C to 50°C, and do not have the desired flatness. The inventors have surprisingly found that by selectively adding more than 0.5 mol% of alkali metal oxides (RO) selected from the group consisting of NaO and / or KO and / or CsO and / or RbO, glass-ceramics with flat expansion curves are obtained. Thus, as claimed within the scope of the present invention, the addition of more than 0.5 mol% RO allows for a higher total MgO+ZnO content, yet still results in glass-ceramics that are hysteresis-free at least in the temperature range from 15°C to 35°C, i.e., the temperature range including room temperature.

[0032] LAS glass ceramics comprise a crystalline phase exhibiting negative expansion and a glassy phase exhibiting positive expansion, which, within the scope of the present invention, advantageously comprises or consists of a high-quartz solid solution, also known as β-eucryptite. In addition to SiO2 and Al2O3, one of the main components of the solid solution is Li2O. When present, ZnO and / or MgO are also incorporated into the solid solution phase and, together with Li2O, affect the expansion behavior of the crystalline phase. In contrast to known zero-expansion glass ceramics, in which MgO and ZnO are specifically used to tailor the desired expansion behavior of the glass ceramic, within the scope of the present invention, R2O is used for this purpose, which may be Na2O and / or K2O and / or Rb2O and / or Cs2O. However, unlike MgO and ZnO, the aforementioned alkali metal oxides remain in the glassy phase and are not incorporated into the high-quartz solid solution.

[0033] In the context of the present invention, it has been found to be advantageous, in order to provide zero-expansion and hysteresis-free glass-ceramics, if the composition satisfies the condition: molar content of SiO + (5 × molar content of LiO) ≥ 105, advantageously ≥ 105.5, advantageously ≥ 106 or preferably ≥ 106.5, in particular molar content of SiO + (5 × molar content of LiO) ≥ 107 or ≥ 107.5. Alternatively or additionally, advantageous upper limits of ≤ 115.5, ≤ 114.5 or ≤ 113.5 may hold for the condition "molar content of SiO + (5 × molar content of LiO)".

[0034] In an advantageous development, the glass ceramic comprises, individually or in any combination, the following components in molar percentages: [Table 1] may include:

[0035] More preferably, the glass ceramic contains, individually or in any combination, the following components in mole %, within the above-mentioned limits for R2O, RO and the sum of TiO2 + ZrO2: [Table 2] may be included.

[0036] In one advantageous embodiment, the LAS glass ceramic comprises (in mole % on an oxide basis): [Table 3] wherein the nucleating agent is preferably TiO2 and / or ZrO2.

[0037] In a further advantageous embodiment, the LAS glass ceramic comprises (in mole % on an oxide basis): [Table 4] wherein the nucleating agent is preferably TiO2 and / or ZrO2.

[0038] The glass ceramics have a silicon dioxide (SiO2) content of at least 60 mol%, more preferably at least 60.5 mol%, also preferably at least 61 mol%, also preferably at least 61.5 mol%, and even more preferably at least 62.0 mol%. The SiO2 content is less than 70 mol%, more preferably at most 69.5 mol%, even more preferably at most 69 mol%, and even more preferably at most 68.5 mol%. A high SiO2 content makes batch melting difficult and increases the melt viscosity, which can cause melt homogenization problems in large-scale production plants. Therefore, it is desirable for the SiO2 content to be less than 70 mol%. A high melt viscosity increases the melt processing temperature (Va). Very high temperatures are required for melt clarification and homogenization, which can lead to attack of the melting unit lining due to the aggressiveness of the melt, which increases with temperature. Furthermore, even high temperatures may not be sufficient to produce a homogeneous melt, which can result in striae and inclusions in the green glass (especially bubbles and particles originating from the lining of the melting unit), which, after ceramization, do not meet the requirements regarding the uniformity of the properties of the produced glass-ceramics, for example the requirements regarding the uniformity of the thermal expansion coefficient. For this reason, an SiO2 content below the aforementioned upper limit may be preferable.

[0039] The proportion of Al2O3 is advantageously at least 10 mol%, advantageously at least 11 mol%, preferably at least 12 mol%, more preferably at least 13 mol%, also preferably at least 14 mol%, also preferably at least 14.5 mol%, and even more preferably at least 15 mol%. If the content is too low, a low-expansion solid solution is not formed, or if formed, it is formed in too small an amount. The proportion of Al2O3 is advantageously at most 22 mol%, in particular at most 21 mol%, preferably at most 20 mol%, even more preferably at most 19.0 mol%, and even more preferably at most 18.5 mol%. If the content of Al2O3 is too high, the viscosity increases and promotes uncontrollable devitrification of the material.

[0040] The glass ceramics according to the present invention may contain 0 to 6 mol% P2O5. The phosphate content of P2O5 in the glass ceramics may be advantageously at least 0.1 mol%, in particular at least 0.3 mol%, preferably at least 0.5 mol%, also preferably at least 0.6 mol%, more preferably at least 0.7 mol%, and even more preferably at least 0.8 mol%. P2O5 is substantially incorporated into the crystalline phase of the glass ceramic, favorably influencing the expansion behavior of the crystalline phase and thus the expansion behavior of the glass ceramic. Furthermore, it improves the solubility of the components and the clarification behavior of the melt. However, if P2O5 is present in an excessive amount, the CTE-T curve in the temperature range from 0°C to 50°C will no longer exhibit the advantageously flat curve. Therefore, it is advantageous to include at most 6 mol%, in particular at most 5 mol%, more preferably at most 4 mol%, and even more preferably less than 4 mol% P2O5 in the glass ceramics. According to individual embodiments, the glass ceramics may be free of P2O5.

[0041] Within the scope of the present invention, certain sums and ratios of the components SiO2, Al2O3 and / or P2O5, i.e. components that form a high-quartz solid solution, can promote the formation of glass-ceramics according to the invention.

[0042] The total proportion in mole percent of the base components SiO and AlO of the LAS glass ceramic is advantageously at least 75 mole percent, in particular at least 78 mole percent, preferably at least 79 mole percent, more preferably at least 80 mole percent, and / or in particular at most 90 mole percent, in particular at most 87 mole percent, preferably at most 86 mole percent, more preferably at most 85 mole percent. If this total is too high, the viscosity curve of the melt will shift to higher temperatures, which is disadvantageous as already explained above in connection with the component SiO. If the total is too low, too little solid solution will form.

[0043] The total proportion in molar percentage of the base components SiO, AlO and PO of the LAS glass ceramic is in particular at least 77 mol%, advantageously at least 81 mol%, advantageously at least 83 mol%, more preferably at least 84 mol% and / or in particular at most 91 mol%, advantageously at most 89 mol%, more preferably at most 87 mol%, and according to one variant at most 86 mol%.

[0044] The ratio of the molar percentages of P2O5 to SiO2 is in particular at least 0.005, advantageously at least 0.01, preferably at least 0.012 and / or in particular at most 0.1, more preferably at most 0.08, and according to one variant at most 0.07.

[0045] As an additional component, the glass ceramic contains lithium oxide (LiO) in a proportion of at least 7 mol%, advantageously at least 7.5 mol%, in particular at least 8 mol%, and particularly preferably at least 8.25 mol%. The proportion of LiO is limited to a maximum of 9.6 mol%, in particular at a maximum of 9.5 mol%, preferably at a maximum of 9.4 mol%, more preferably at a maximum of 9.35 mol%, and even more preferably at a maximum of 9.3 mol% or less. LiO is a component of the solid solution phase and has a significant influence on the thermal expansion of the glass ceramic. It is desirable not to exceed the aforementioned upper limit of 9.6 mol%, because exceeding this limit would result in a glass ceramic with a negative thermal expansion coefficient CTE(0:50) despite the total content of MgO and ZnO according to the present invention. If the LiO content is less than 7 mol%, the solid solution is not formed sufficiently, and the thermal expansion coefficient of the glass ceramic remains positive.

[0046] The glass ceramics according to the invention contain more than 0.5 mol% of alkali metal oxides R2O, where R2O can be Na2O and / or K2O and / or Cs2O and / or Rb2O. Surprisingly, an R2O content of more than 0.5 mol% contributes to the achievement of glass ceramics with a flat expansion curve profile, even at relatively high MgO+ZnO sums. The total R2O content of Na2O, K2O, Cs2O, and Rb2O can be advantageously at least 0.55 mol%, in particular at least 0.6 mol%, advantageously at least 0.65 mol%, advantageously at least 0.7 mol%, and especially at least 0.75 mol%. Some variations contain at least 0.8 mol%, advantageously at least 0.85 mol%, preferably at least 0.9 mol%, preferably at least 0.95 mol%, and preferably at least 1.0 mol% R2O. The sum of the NaO, KO, CsO, and RbO contents, R2O, can be advantageously at most 6 mol%, in particular at most 5 mol%, preferably at most 4 mol%, preferably at most 3 mol%, and preferably at most 2.5 mol%. If the sum of Na2O+K2O+Cs2O+Rb2O is too low or too high, the CTE (0:50) targeted by the present invention may not be achieved. However, too much R2O in the glass-ceramic deteriorates the chemical resistance of the material. If the sum of Na2O+K2O+Cs2O+Rb2O is too low, the expansion curve of the material will exhibit a curved region in the temperature range, and glass-ceramics with a total content of MgO+ZnO according to the present invention will not be hysteresis-free within the meaning of the present invention.

[0047] The individual components sodium oxide (NaO), potassium oxide (KO), cesium oxide (CsO), and rubidium oxide (RbO) are optionally present in the glass-ceramics within the above-mentioned limits for the total R2O, i.e., NaO-free and / or KO-free and / or CsO-free and / or RbO-free variants are possible. The proportion of NaO can be advantageously at most 3 mol%, preferably at most 2 mol%, in particular at most 1.7 mol%, preferably at most 1.5 mol%, preferably at most 1.3 mol%, and preferably at most 1.1 mol%. The proportion of K2O can be advantageously at most 3 mol%, in particular at most 2.5 mol%, preferably at most 2 mol%, preferably at most 1.8 mol%, and preferably at most 1.7 mol%. The proportion of CsO may advantageously be at most 2 mol%, in particular at most 1.5 mol%, preferably at most 1 mol%, and preferably at most 0.6 mol%. The proportion of RbO may advantageously be at most 2 mol%, in particular at most 1.5 mol%, preferably at most 1 mol%, and preferably at most 0.6 mol%. According to individual embodiments, the glass-ceramics do not contain NaO and / or KO and / or CsO and / or RbO.

[0048] Na2O and K2O may be present in the glass-ceramic, independently of one another, in a proportion of at least 0.05 mol%, advantageously at least 0.1 mol%, advantageously at least 0.15 mol%, particularly at least 0.2 mol%, particularly at least 0.25 mol%, preferably at least 0.3 mol%, preferably at least 0.35 mol%, preferably at least 0.4 mol%, more preferably at least 0.45 mol%, and more preferably at least 0.5 mol%. The aforementioned limits also apply to Cs2O and Rb2O. The components Na2O, K2O, Cs2O, and Rb2O remain substantially in the amorphous glass phase of the glass-ceramic, which can be important for ensuring the zero expansion of the ceramized material.

[0049] Glass-ceramics can contain at least one alkaline earth metal oxide selected from the group consisting of CaO, BaO, and SrO, collectively referred to as "RO." Each component of the RO group remains substantially in the amorphous glass phase of the glass-ceramic and can be important for ensuring the zero expansion of the ceramized material. If the sum of CaO, BaO, and SrO is too high, the CTE (0:50) targeted by the present invention will not be achieved. Therefore, the RO content is advantageously at most 6 mol% or at most 5.5 mol%, particularly at most 5 mol%, advantageously at most 4.5 mol%, especially at most 4 mol%, preferably at most 3.8 mol%, even more preferably at most 3.5 mol%, and preferably at most 3.2 mol%. If the glass-ceramic contains RO, an advantageous lower limit can be at least 0.1 mol%, advantageously at least 0.2 mol%, preferably at least 0.3 mol%, and preferably at least 0.4 mol%. According to particular embodiments, the glass-ceramics may be free of RO.

[0050] The proportion of CaO may be, in particular, at most 5 mol%, advantageously at most 4 mol%, advantageously at most 3.5 mol%, advantageously at most 3 mol%, even more preferably at most 2.8 mol%, and more preferably at most 2.6 mol%. The glass ceramic may advantageously contain at least 0.1 mol%, advantageously at least 0.2 mol%, especially at least 0.4 mol%, and preferably at least 0.5 mol% of CaO. The glass ceramic may advantageously contain the component BaO, which is a good glass former, in a proportion of at least 0.1 mol%, especially at least 0.2 mol%, and / or at most 4 mol%, advantageously at most 3 mol%, advantageously at most 2.5 mol%, especially at most 2 mol%, preferably at most 1.5 mol%, and also preferably at most 1.4 mol%. The glass ceramics may contain SrO in a proportion of at most 3 mol%, advantageously at most 2 mol%, in particular at most 1.5 mol%, preferably at most 1.3 mol%, preferably at most 1.1 mol%, more preferably at most 1 mol%, also preferably at most 0.9 mol% and / or in particular at least 0.1 mol%. According to individual embodiments, the glass ceramics may be free of CaO and / or BaO and / or SrO. According to an advantageous variant, the glass ceramics contain CaO.

[0051] The glass ceramics according to the invention have a total MgO + ZnO content in the range of >0.5 to 1.5 mol %. An advantageous lower limit of this total can be at least 0.55 mol %, advantageously at least 0.6 mol %, advantageously at least 0.65 mol %, advantageously at least 0.7 mol %, advantageously at least 0.75 mol %. At most, the glass ceramic contains 1.5 mol % MgO + ZnO. An advantageous upper limit can be less than 1.5 mol %, in particular at most 1.45 mol %, preferably at most 1.4 mol %, preferably at most 1.35 mol %, preferably at most 1.3 mol %, preferably at most 1.25 mol %, preferably at most 1.2 mol %, preferably at most 1.15 mol %, preferably at most 1.1 mol %, preferably at most 1.05 mol %, preferably at most 1.0 mol %, preferably at most 0.95 mol %. If the sum of MgO and ZnO is too high, the glass-ceramic will exhibit thermal hysteresis of more than 0.1 ppm in the temperature range of 15°C to 35°C.

[0052] The glass-ceramics can contain magnesium oxide (MgO) in a content of 0 to 1.1 mol%. An advantageous upper limit of MgO can be 1.1 mol%. If the MgO content is too high, the material will exhibit thermal hysteresis of 0.1 ppm or more in the temperature range. Other advantageous upper limits can be up to 1.05 mol%, up to 1.0 mol%, up to 0.95 mol%, up to 0.9 mol%, up to 0.85 mol%, or up to 0.8 mol%. The addition of MgO can help to lower the CTE and provide zero-expansion glass-ceramics, especially when the Li2O content is high. When MgO is included in the glass-ceramics, advantageous lower limits of MgO can be 0.05 mol%, 0.1 mol%, 0.15 mol%, 0.2 mol%, 0.25 mol%, or 0.3 mol%. Some variations may also contain at least 0.35 mol%, or 0.4 mol%, or 0.45 mol%, or 0.5 mol%, or more, of MgO. An advantageous variation of the glass-ceramic may be free of MgO.

[0053] The glass-ceramics can contain zinc oxide (ZnO) in a content of 0 to 1.5 mol%. An advantageous upper limit can be 1.5 mol%. If the ZnO content is too high, the material will exhibit thermal hysteresis of 0.1 ppm or more in the temperature range. Other advantageous upper limits can be up to 1.45 mol%, up to 1.4 mol%, up to 1.35 mol%, up to 1.3 mol%, up to 1.25 mol%, up to 1.2 mol%, up to 1.15 mol%, up to 1.1 mol%, up to 1.05, or up to 1.0 mol%. Some variations can also contain up to 0.95 mol%, up to 0.9 mol%, up to 0.85 mol%, or up to 0.8 mol% ZnO. If ZnO is included in the glass-ceramic, an advantageous lower limit for ZnO can be 0.05 mol%, or 0.1 mol%, or 0.15 mol%, or 0.2 mol%, or 0.25 mol%, or 0.3 mol%. Some variations can also include 0.35 mol%, or 0.4 mol%, or 0.45 mol%, or 0.5 mol%, or more than 0.5 mol% ZnO. An advantageous variation of the glass-ceramic can be ZnO-free.

[0054] The glass ceramic further comprises at least one nucleating agent selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, WO3, and HfO2. The nucleating agent may be a combination of two or more of the above components. A further advantageous nucleating agent may be HfO2. Thus, in an advantageous embodiment, the glass ceramic comprises HfO2 and at least one nucleating agent selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3. The total proportion of nucleating agents is in particular at least 1.5 mol%, preferably at least 2 mol% or more than 2 mol%, more preferably at least 2.5 mol%, and in certain variants at least 3 mol%. The upper limit can be at most 6 mol%, in particular at most 5 mol%, preferably at most 4.5 mol% or at most 4 mol%. In a particularly advantageous variant, the stated upper and lower limits apply to the sum of TiO2 and ZrO2.

[0055] The glass ceramics may contain titanium oxide (TiO) in a proportion of at least 0.1 mol%, advantageously at least 0.5 mol%, in particular at least 1.0 mol%, preferably at least 1.5 mol%, preferably at least 1.8 mol%, and / or in particular at most 5 mol%, advantageously at most 4 mol%, more preferably at most 3 mol%, even more preferably at most 2.5 mol%, preferably 2.3 mol%. TiO-free variants of the glass ceramics according to the invention are also possible.

[0056] The glass ceramics can advantageously further comprise zirconium oxide (ZrO) in a proportion of at most 3 mol%, in particular at most 2.5 mol%, more preferably at most 2 mol%, preferably at most 1.5 mol% or at most 1.2 mol%. In particular, ZrO may be present in a proportion of at least 0.1 mol%, more preferably at least 0.5 mol%, at least 0.8 mol%, or at least 1.0 mol%. ZrO-free variants of the glass ceramics according to the invention are also possible.

[0057] According to some advantageous variants of the invention, 0 to 5 mol % of Ta2O5 and / or Nb2O5 and / or SnO2 and / or MoO3 and / or WO3, individually or in total, may be included in the glass-ceramics, for example, as alternative or additional nucleation agents or to adjust optical properties, such as the refractive index. HfO2 may also serve as an alternative or additional nucleation agent. To adjust the optical properties, some advantageous variants may include, for example, Gd2O3, YO3, HfO2, Bi2O3, and / or GeO2.

[0058] Glass ceramics are As2O3, Sb2O3, SnO2, SO4 2- , F - , Cl - , Br -or mixtures thereof in a proportion of more than 0.05 mol %, or at least 0.1 mol % and / or at most 1 mol %. However, since the fining agent fluorine can reduce the transparency and / or chemical resistance of the glass-ceramic, if this component is present, it is limited in particular to at most 0.5 mol %, preferably at most 0.3 mol %, and more preferably at most 0.1 mol %. Preferably, the glass-ceramic is fluorine-free.

[0059] According to one advantageous embodiment, the glass ceramic can contain up to 0.05 mol % As2O3 as a fining agent, and according to one advantageous embodiment, can be free of As2O3. It may be advantageous for the glass ceramic to contain at least one alternative redox fining agent and / or at least one evaporative fining agent and / or at least one decomposition fining agent, in particular instead of or in addition to up to 0.05 mol % As2O3.

[0060] Alternative redox fining agents containing higher or polyvalent ions that are in temperature-dependent equilibrium with each other and can have at least two oxidation states, and which release gas, usually oxygen, at high temperatures, include, for example, Sb2O3, SnO2, MnO2, CeO2, and Fe2O3.

[0061] Evaporative fining agents that are volatile at high temperatures due to their vapor pressure include the fining halogens Cl, Br, and I.

[0062] Examples of decomposition fining agents that decompose at high temperatures to release fining gases and whose decomposition products have a sufficiently high gas pressure include salts containing oxoanions, particularly sulfate components that are quantified as SO3 in material analysis.

[0063] Combinations of the above chemical fining agents may also be advantageous. SnO2 and / or Sb2O3, each advantageously with up to 0.05 mol% As2O3; or - As2O3-free combinations, for example Sb2O3 and SnO2; Sb2O3 and Cl, Sb2O3 and SO3; or - Combinations that do not contain As2O3 and do not contain Sb2O3, for example, a combination of SnO2 and Cl, a combination of SnO2 and SO3, a combination of Cl and SO3 The glass compositions described above may optionally contain coloring oxide additives, such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, CuO, CeO2, Cr2O3, rare earth oxides, each individually or in total in a content of 0 to 3 mol %. A preferred variant does not contain any coloring oxides.

[0064] B2O3 can have a negative effect on the transparency of the glass-ceramics. Therefore, in an advantageous variant, the content of this component is limited to less than 0.2 mol %, preferably at most 0.1 mol %. A preferred variant does not contain B2O3.

[0065] According to one advantageous embodiment of the invention, the composition does not contain any other ingredients than those mentioned above.

[0066] According to an advantageous embodiment of the invention, the glass ceramic or green glass according to the invention consists in particular of at least 90 mol %, more preferably at least 95 mol %, most preferably at least 99 mol % of the above-mentioned components, or in particular of SiO2, Al2O3, Li2O, MgO, ZnO, PO5, R2O, RO and nucleating agents.

[0067] According to an advantageous development of the glass ceramic, the glass ceramic is substantially free of one or more glass components selected from the group consisting of PbO, B2O3, CrO3, F, Cd compounds.

[0068] According to the present invention, the expressions "free of X" or "free of component X" mean that the glass-ceramic is substantially free of this component X, i.e., such component is present at most as an impurity in the glass and is not added to the composition as a separate component. In the case of other glass components, higher impurity contents are possible, for each component, up to 0.1 mol %, preferably up to 0.05 mol %, advantageously up to 0.01 mol %, advantageously up to 0.005 mol %, and for some components, advantageously up to 0.003 mol %, where X represents an optional component, such as PbO.

[0069] The glass-ceramics according to the present invention have a high-quartz solid solution as the predominant crystalline phase. The predominant crystalline phase is the crystalline phase that accounts for the largest volume percentage of the crystalline phase. The high-quartz solid solution is a metastable phase whose composition and / or structure change or transform into another crystalline phase depending on the crystallization conditions. The high-quartz solid solution has very low thermal expansion, or even decreases with increasing temperature. In one advantageous embodiment, the crystalline phase does not include β-spodumene or keatite.

[0070] Advantageous embodiments of the LAS glass ceramics have a crystalline phase content of less than 75% by volume and / or preferably more than 45% by volume. The crystalline phase consists of a high-quartz solid solution, also known as β-eucryptite solid solution. The average crystallite size of the high-quartz solid solution is advantageously less than 100 nm, in particular less than 80 nm, preferably less than 70 nm. The small crystallite size makes the glass ceramic transparent and also makes it easier to polish. In a particularly advantageous variant, the average crystallite size of the high-quartz solid solution may be ≦60 nm, in particular ≦50 nm. The crystalline phases, their content, and average crystallite size are determined by X-ray diffraction analysis, as is known.

[0071] According to one embodiment of the present invention, transparent glass-ceramics are produced. Transparency allows for better evaluation of many of the properties of such glass-ceramics, particularly, of course, their internal quality. The glass-ceramics according to the present invention are transparent, i.e., have a net transmittance of at least 70% in the wavelength range from 350 to 650 nm. B2O3 and / or a high fluorine content can reduce transparency. Therefore, an advantageous variant does not contain one or both of the aforementioned components. Furthermore, the glass-ceramics produced within the scope of the present invention are non-porous and crack-free. Within the scope of the present invention, "non-porous" means a porosity of less than 1%, preferably less than 0.5%, and more preferably less than 0.1%. Cracks are gaps, i.e., discontinuities, in an otherwise continuous microstructure.

[0072] To enable the production of uniform glass-ceramics in large-scale production plants, the processing temperature Va or T4 value of the green glass on which the glass-ceramic is based is advantageously at most 1330°C, preferably at most 1320°C. Some advantageous variants can have a processing temperature of at most 1310°C or at most 1300°C or less than 1300°C. The processing temperature Va is the temperature at which the melt reaches a temperature of 10 4 This is the temperature at which the glass-ceramic has a viscosity of 1000 dPa. Homogeneity refers in particular to the uniformity of the CTE of the glass-ceramic over a large volume and the low number, preferably absence, of inclusions such as bubbles or particles. This is a quality characteristic of glass-ceramics and a prerequisite for their use in precision components, especially very large ones.

[0073] Furthermore, the T3 value of the green glass on which the glass-ceramic is based is advantageously at most 1550° C., even more preferably at most 1525° C., and even more preferably at most 1500° C. Some embodiments even have a T3 value of at most 1490° C. or at most 1450° C. Values ​​in this range allow the green glass to exhibit good meltability and homogeneity.

[0074] The processing temperature is determined by the composition of the glass ceramic. Since SiO2, a glass network former, is thought to increase the viscosity and thus the processing temperature, the maximum SiO2 content should be selected in accordance with the above-mentioned regulations. Furthermore, the alkali metal oxide content and the total content of MgO and ZnO according to the present invention reduce the viscosity of the melt, thereby lowering the processing temperature. This leads to improved uniformity of the melt, and thus to improved uniformity of the green glass body produced and the glass ceramic obtained therefrom.

[0075] CTE Furthermore, the glass ceramics according to the invention exhibit zero thermal expansion (see Table 1), i.e., the average coefficient of thermal expansion CTE in the range of 0 to 50°C is at most 0±0.1×10 -6 / K. In some advantageous variations, the average CTE in the range of 0 to 50°C is at most 0±0.05×10 -6 In certain applications, the average CTE over a wider temperature range, for example, from -30°C to +70°C, especially from -40°C to +80°C, can be up to 0±0.1×10 -6 / K, i.e., exhibiting zero expansion.

[0076] To determine the CTE-T curves of the glass ceramics and precision components according to the present invention and the comparative examples, the differential CTE (T) is first determined. The differential CTE (T) is determined as a function of temperature. The CTE is then determined according to the following equation (1): CTE(T)=(1 / l0)×(∂l / ∂T) (1)

[0077] To create a Δl / l0-T curve or expansion curve or a plot of the change in length Δl / l0 of a test piece (glass ceramic or precision part) versus temperature, the initial length l0 at initial temperature t0 is changed to the length l at temperature t. tThe temperature-dependent length change of a specimen can be measured up to 100°C. Here, in particular, a small temperature interval, such as 5°C, 3°C, or 1°C, is selected to determine the measurement points. Such measurements can be performed, for example, by dilatometry, interferometry, e.g., the Fabry-Perot method, i.e., evaluating the shift of the resonance peak of a laser beam incident on the material, or other suitable methods. Within the scope of the present invention, the dilatometry method was selected for determining the CTE on a bar-shaped specimen 100 mm long and 6 mm in diameter, with a temperature interval of 1°C. The method selected for determining the CTE has, in particular, an accuracy of at least ±0.05 ppm / K, preferably at least ±0.03 ppm / K. However, the CTE can, of course, also be determined by a method with an accuracy of at least ±0.01 ppm / K, preferably at least ±0.005 ppm / K, or, according to some embodiments, even at least ±0.003 ppm / K or at least ±0.001 ppm / K.

[0078] From the Δl / l0-T curve, the average CTE for a specific temperature interval, for example, the temperature range of 0°C to 50°C, is calculated.

[0079] The CTE-T curve is derived by deriving the Δl / l0-T curve. From the CTE-T curve, the zero crossing and the slope of the CTE-T curve within the temperature range can be determined. From the CTE-T curve, the shape and location of the advantageous CTE "plateau" formed in some variants can be determined (see below and Figure 18).

[0080] An advantageous embodiment of a precision component comprising the glass-ceramic according to the invention (especially in the form of a substrate) has a high CTE uniformity. Here, the value of the CTE uniformity (English: "total spatial variation of CTE") is understood to be the so-called peak-to-valley value, i.e. the difference between the highest and lowest CTE values ​​of samples taken from the precision component. Therefore, the CTE uniformity does not refer to the CTE of the material for the component, but rather to the spatial variation of the CTE over the area or the entire precision component. To determine the CTE uniformity, a number of samples are taken from the precision component at different positions, and the CTE value is determined for each of them in ppb / K, where 1 ppb / K = 0.001 x 10 -6 / K. The CTE uniformity, i.e., the spatial variation of the CTE, across the precision component is advantageously at most 5 ppb / K, in particular at most 4 ppb / K, and most preferably at most 3 ppb / K. Methods for determining CTE uniformity and means for achieving CTE uniformity are described in WO 2015 / 124710, the disclosure of which is incorporated herein in its entirety.

[0081] Thermal Hysteresis The glass-ceramics in the scope of the present invention are hysteresis-free, since they have a thermal hysteresis of less than 0.1 ppm at least in the temperature range of 15°C to 35°C (see Figures 10 and 11). Thus, at any temperature within the temperature range of 15°C to 35°C, the glass-ceramics exhibit an isothermal length change of less than 0.1 ppm after a 5-hour holding time at constant temperature, after being subjected to a temperature change at a heating or cooling rate of 36 K / h, i.e., 0.6 K / min.

[0082] Thus, "a thermal hysteresis of less than 0.1 ppm in at least the temperature interval from 15° C. to 35° C." means that the glass-ceramic exhibits a length change of less than 0.1 ppm in this temperature interval after heat treatment and subsequent constant temperature hold for a heating or cooling rate of 36 K / h, i.e., 0.6 K / min, and a hold time of 5 hours at -10° C. The characteristic thermal hysteresis thus describes the thermal behavior of the glass-ceramic or a component made therefrom over time.

[0083] In an advantageous embodiment, this hysteresis-free property exists in a temperature range of at least 15°C to 40°C, or at least in a temperature range of 10°C to 35°C, in particular in a temperature range of at least 15°C to 45°C, in particular in a temperature range of at least 15°C to 50°C. Particularly preferably, the temperature range over which the hysteresis-free property is exhibited is even wider, so that the material or component is also suitable for applications at temperatures up to, and advantageously even above, at least 100°C. Particularly preferably, the temperature range over which the hysteresis-free property is exhibited is even wider. Preferred application temperatures are -60 to 100°C, more preferably -40 to +80°C. A particular variant of the invention is suitable for application temperatures T, for example in the range of 5°C to 20°C. A , or T of 22°C, 40°C, 60°C, 80°C and 100°C A The present invention relates to glass ceramics and precision parts for such applications, and in particular to glass ceramics and precision parts that exhibit hysteresis-free properties even at the aforementioned temperatures.

[0084] Thermal hysteresis was determined for the glass ceramics and precision components according to the invention, as well as for comparative examples, on rod-shaped specimens (i.e., precision component specimens or glass ceramic specimens) with a length of 100 mm and a diameter of 6 mm, using a precision dilatometer capable of determining the CTE with a reproducibility of ±0.001 ppm / K and ±0.003 ppm / K (absolute value) in a temperature interval of 1°C, according to the method and apparatus configuration disclosed in DE 10 2015 113 548 A1, the disclosure of which is incorporated herein by reference in its entirety. For each specimen examined, the length change Δl / l0 was determined as a function of temperature while cooling from 50°C to -10°C at a cooling rate of 36 K / h. After an isothermal hold time of 5 hours at -10°C, the specimen was heated to 50°C at a heating rate of 36 K / h, and the length change Δl / l0 was recorded as a function of temperature. The thermal hysteresis behavior of the specimens is studied at -5°C, 0°C, 5°C, 10°C, 15°C, 19°C, 22°C, 35°C, and 40°C. These points are representative of the temperature range from -10°C to 50°C because, in these temperatures, hysteresis decreases with increasing temperature. Thus, a specimen that is hysteresis-free at 22°C or 35°C will also exhibit no hysteresis up to 50°C.

[0085] To determine the thermal hysteresis at 15°C, individual measurements of the length change were recorded at five temperatures: 13°C, 14°C, 15°C, 16°C, and 17°C, i.e., two temperature points above and below 15°C, when the sample was heated and cooled at a rate of 36 K / h from -10°C to 50°C. The average value was calculated from the difference between the measurements of the heating and cooling curves for these five measurement points, and this was reported in the table as "Hyst.@15°C" in [ppm].

[0086] To determine the thermal hysteresis at 35°C, the sample was similarly heated and cooled in the range of -10°C to 50°C at a rate of 36 K / h, and individual measurements of the length change were recorded at five temperatures: 33°C, 34°C, 35°C, 36°C, and 37°C, i.e., two temperature points above and below 35°C. The average value was calculated from the difference in the measurements of the heating and cooling curves at these five measurement points, and this was recorded in the table in ppm as "Hyst.@35°C."

[0087] The same procedure was carried out for the other temperature points mentioned above.

[0088] Figures 2 to 11 show the thermal hysteresis curves of glass-ceramics according to the invention (Figures 10 and 11) and of known glass-ceramics (Figures 2, 4 to 9) or glass-ceramics not according to the invention (Figure 3). To allow a better comparison, a range of 6 ppm was always selected on the y-axis for the representation in the figures.

[0089] 2-8 show thermal hysteresis curves for known and non-inventive materials that can be used for precision components. The cooling curves (dashed lines) and heating curves (dotted lines) are clearly separated from each other, particularly at low temperatures; that is, the curves clearly diverge. At 15°C, they are separated by more than 0.1 ppm, and in some comparative examples, by as much as about 1 ppm. Thus, these materials and precision components made therefrom exhibit significant thermal hysteresis at least in the temperature range of 15°C to 35°C.

[0090] The tested LAS glass ceramics shown in Figures 2-5 (Comparative Examples 3, 9, and 10 in Table 2) all contain MgO and ZnO, with most also containing RO. They exhibit thermal hysteresis over a wide temperature range between 15°C and 35°C. Figures 6 and 7 show the hysteresis curves of LAS glass ceramics containing ZnO but not MgO (Comparative Examples 8 and 14 in Table 2). Both materials exhibit an increase in the intensity of thermal hysteresis below 19°C. Figure 8 shows the hysteresis curve of an LAS glass ceramic containing MgO but not ZnO (Comparative Example 15 in Table 2). This material also exhibits an increase in the intensity of thermal hysteresis below 22°C. As can be seen in Figure 9, this known material (Comparative Example 1 in Table 2) does not exhibit thermal hysteresis, but the steep transition in the curve indicates that it is not a zero-expansion material. The average CTE here is -0.24 ppm / K.

[0091] The LAS glass ceramics and precision components according to the present invention have a predetermined total MgO+ZnO content of greater than 0.5 mol% to 1.5 mol%, in combination with a predetermined RO content of greater than 0.5 mol%. As can be seen from Figures 10 and 11, the heating and cooling curves overlap at least in the temperature range of 15°C to 35°C, i.e., the glass ceramics are hysteresis-free. However, these materials are not only hysteresis-free in the 15°C to 35°C range, but are also hysteresis-free in the range of at least 15°C to 40°C or 15°C to 45°C.

[0092] Further expansion properties An advantageous embodiment of the present invention has a further advantageous expansion feature.

[0093] To describe the expansion behavior of a test specimen (glass ceramic or precision component), the TCL value is often given, where TCL stands for "Total Change of Length." In the context of the present invention, the TCL value is given in the temperature range of 0°C to 50°C. This is determined from the normalized Δl / l0-T curve (also referred to as dl / l0-T curve in the figures) of each test specimen, where "normalized" means that the length change at 0°C is 0 ppm. The Δl / l0-T curve for determining the TCL is generated in the same manner as described above for the determination of the CTE in the context of the present invention.

[0094] The TCL value is the difference between the highest and lowest dl / l0 values ​​in this temperature range: TCL(0;50℃)=|dl / l0max.|+|dl / l0min.| (2) where "dl" represents the change in length at each temperature, and "l0" represents the length of the test piece at 0°C. When calculating, the absolute values ​​of the dl / l0 values ​​are adjusted.

[0095] Figures 13 to 16 show expansion curves of known materials, from which the maximum and minimum dl / l0 values, respectively, can be read to calculate the TCL value (see also below). Each expansion curve exhibits a curved progression over the temperature range 0°C to 50°C.

[0096] In contrast, within the scope of the present invention, a flat progression of the expansion curve in the temperature range 0° C. to 50° C. is an advantageous feature of glass ceramics and precision components (see FIG. 12). In some advantageous variants, depending on the field of application of the component, a flat progression of the expansion curve may also be desirable in other temperature ranges, in particular in the ranges (20;40), (20;70) and / or (−10;30).

[0097] As an expression of the degree to which the course of the thermal expansion curve deviates from a simple linear course, in an advantageous embodiment of the invention a parameter F is introduced as an index of the flatness of the expansion curve, which allows the classification of CTE curves: F = TCL(0;50℃) / |Expansion(0;50℃)| (3)

[0098] The parameter F is calculated by taking the ratio of the TCL(0;50) value (in ppm) (see above) to the difference in expansion (in ppm) between the temperature points 0°C and 50°C. The expansion curves for the TCL determination are, by definition, normalized so that the length change at 0°C is 0 ppm, so the "difference in expansion between the temperature points 0°C and 50°C" corresponds to the "expansion at 50°C" given in the table. The absolute value of the expansion at 50°C is used to calculate the parameter F.

[0099] Here, it is advantageous if, for each material or component, the parameter F is less than 1.20, preferably less than 1.15, preferably less than 1.10, preferably at most 1.05. The closer the parameter F is to 1, the flatter the progression of the expansion curve will be.

[0100] In Figure 12 it can be seen that advantageous embodiments of LAS glass ceramics exhibit a flat progression of the expansion curve (here F=1) both in the temperature range from 0°C to 50°C and in a wider temperature range, whereas Figures 13 to 17 show that known materials exhibit a much steeper and more curved progression of the expansion curve in this temperature range.

[0101] FIG. 12 illustrates the expansion curve of the advantageous glass-ceramic based on the advantageous ceramization of Composition Example 2. For display, the 1.6 ppm range was selected on the y-axis. The maximum expansion value (dl / l0max.) is at +50°C (dl / l0 is +0.96 ppm, i.e., |0.96 ppm|), and the minimum expansion value (dl / l0min.) is 0 ppm. The expansion difference between the temperature points of 0°C and 50°C, which corresponds to the absolute value of "expansion at 50°C," is 0.96 ppm. From this, the parameter F of this material is calculated as follows: F (Example 2 of Table 1) = 0.96 ppm / 0.96 ppm = 1.00.

[0102] Thus, advantageous glass ceramics and precision components of the present invention not only exhibit a very flat expansion curve, i.e., zero expansion in the temperature range of 0°C to 50°C, but also exhibit only a small variation in the change in linear expansion, and thus in the differential CTE, in this range. As can be seen, for example, in FIG. 20, advantageous embodiments of the present invention exhibit a flat expansion curve over an even wider temperature range. See, by comparison, the much steeper expansion curve of the known material for the same temperature range in FIG. 17. The expansion behavior can also be considered in selected other temperature ranges, particularly (-10; 30), (20; 40), and (20, 70), as will be discussed below.

[0103] In comparison with preferred embodiments of glass ceramics and precision components, Figures 13 to 17 show the expansion behavior of known materials and precision components made therefrom, from which the parameter F can be calculated. The expansion behavior of the materials or precision components shown in Figures 13 to 17 was measured using the same dilatometer under conditions comparable to the expansion behavior of the preferred embodiment of glass ceramics shown in Figure 12. Generally, the known materials exhibit a curved progression of the expansion curves.

[0104] Figure 13 shows the expansion curve of commercially available titanium-doped silica glass. As can be seen, the absolute value of the expansion value at +50°C (dl / l0max. is +0.73 ppm, so |0.73 ppm|) plus the absolute value of the expansion value at 14°C (dl / l0min. is -0.19 ppm, so |0.19 ppm|) gives a TCL(0;50) value of approximately 0.92 ppm. The expansion difference between the temperature points of 0°C and 50°C, which corresponds to the absolute value of "expansion at 50°C," is 0.73 ppm. From this, the parameter F of this material can be calculated as follows: F(Ti-doped SiO2) = 0.92 ppm / 0.73 ppm = 1.26

[0105] Similarly, the parameter F of the known LAS glass ceramic or the corresponding precision part (see FIG. 14) is calculated as follows: F(known LAS glass ceramic)=1.19 ppm / 0.11 ppm=10.82

[0106] Similarly, the parameter F of the known cordierite glass ceramic or the corresponding precision part (see FIG. 15) is calculated as follows: F(known cordierite glass ceramic)=2.25 ppm / 0.25 ppm=9

[0107] Similarly, the parameter F of the known sintered cordierite ceramic or the corresponding precision part (see FIG. 16) is calculated as follows: F(known sintered cordierite ceramic)=4.2 ppm / 2.71 ppm=1.55

[0108] Glass ceramics with a flat expansion curve are highly advantageous because precision components can be optimized for subsequent application temperatures and also exhibit low thermal expansion, for example, at higher and / or lower temperature loads during production. Precision components for microlithography, EUV microlithography (also referred to as "EUV lithography" or "EUVL"), and metrology are typically used in standard cleanroom conditions, particularly at room temperature of 22°C. The CTE can be adapted to the application temperature. However, such components are subjected to various process steps, such as coating with a metal layer, cleaning, structuring, and / or exposure steps, during which temperatures higher or, in some cases, lower than those present during subsequent use in the cleanroom. Therefore, advantageous glass ceramics and precision components made therefrom, which have a parameter F of less than 1.20 and thus exhibit optimized zero expansion not only at application temperatures but also, in some cases, at high and / or low temperatures during production, are highly advantageous. Properties such as being hysteresis-free and having a parameter F of less than 1.20 are particularly advantageous when precision components or glass-ceramics are used in EUV lithography, i.e., when the precision components are, for example, EUVL mirrors, EUVL mask blanks or the corresponding substrates, since in EUV lithography, mirrors and masks in particular are heated very non-uniformly in a point-wise or radial direction by the irradiation of high-energy radiation. Under these conditions of use, it is advantageous for the precision components or glass-ceramics to have a small slope of the CTE-T curve in the temperature range around the application temperature (see below).

[0109] Advantageous glass ceramics and precision components that are even better optimized for the later application temperatures of 20 or 22°C are characterized by a relative length change (dl / l0) in the temperature range from 20°C to 30°C of |0.10| ppm or less, preferably |0.09| ppm or less, particularly preferably |0.08| ppm or less, and very particularly preferably |0.07| ppm or less and / or a relative length change (dl / l0) in the temperature range from 20°C to 35°C of |0.17| ppm or less, preferably |0.15| ppm or less, particularly preferably |0.13| ppm or less, and very particularly preferably |0.11| ppm or less.

[0110] Alternatively or additionally, the glass ceramics and precision components thus optimized can be characterized by a relative length change (dl / l0) of |0.30| ppm or less, preferably |0.25| ppm or less, particularly preferably |0.20| ppm or less, and especially preferably |0.15| ppm or less in the temperature range from 20°C to 40°C. The relative length change characteristics for each temperature range can be seen, in particular, from the dl / l0 curves in Figures 12 to 17. When referring to relative length changes (dl / l0), these data naturally refer to the absolute values ​​of the respective values.

[0111] Zero-expansion, hysteresis-free materials exhibiting such advantageous expansion behavior are particularly suitable for use as substrates for EUVL mirrors, or as EUVL mirrors that are heated to different degrees in light and shadow areas during operation, for example, due to a respective exposure mask. Due to the small relative length changes described above, EUVL mirrors formed from advantageous glass-ceramics exhibit smaller local gradients (local slopes or local tilts) in the topography of the mirror surface than EUVL mirrors made from known materials. The same applies to EUVL mask blanks or EUVL masks or EUVL photomasks.

[0112] In particular, in the case of glass-ceramics that exhibit a very flat course of the expansion curve in the temperature range in question, fluctuating close to or around 0 ppm, which is an overall advantageous expansion behavior, it may be advantageous to introduce a further indicator of the flatness of the expansion curve as an alternative to or in addition to parameter F, in which case the expansion curve is considered not in the temperature range (0;50) but in another temperature interval (Ti), in particular in the temperature ranges (20;40), (20;70) and / or (-10;30). This allows the expansion behavior to be better classified with respect to the application area at a later point in time.

[0113] Alternative parameter f T.i. has units (ppm / K) and is as follows: f T.i. =TCL (T.i.) / Temperature range (Ti) width (4) where Ti represents the respective temperature interval.

[0114] TCL (T.i.) The value is the difference between the maximum and minimum dl / l0 values ​​in each temperature range (Ti), where the expansion curve is (T.i.) The determinations are also normalized by definition so that the length change at 0°C is 0 ppm. So, for example: TCL (20;40℃) =|dl / l0max.|+|dl / l0min.| (5) where "dl" represents the change in length at each temperature, and "l0" represents the length of the specimen at 0°C. If the curve fluctuates around zero in the temperature range (e.g., Figure 22), the absolute value of the dl / l0 value is used for calculation. Otherwise, the TCL (T.i.) is the interval calculated from the difference between the maximum and minimum dl / l0 values ​​in each temperature interval (Ti), which is self-evident and can be seen in the figures (e.g., Figures 20 and 21). (T.i.) can be calculated as follows: TCL (T.i.)= dl / l0max.-dl / l0min. (6)

[0115] Alternative parameter f T.i. is expressed as TCL according to equation (4). (T.i.) It is calculated by taking the ratio of the value [in ppm] (see above) to the width, given in [K], of the temperature interval (Ti) in which the expansion difference is considered. The width of this temperature interval, from 20°C to 40°C, is 20 K. On the other hand, if we consider the progression of the expansion curve in the interval Ti = (20; 70) or (-10; 30), the denominator of equation (4) is 50 K or 40 K.

[0116] In one advantageous embodiment, in the glass ceramics, the alternative parameter f (20;40) is less than 0.024 ppm / K, and / or the alternative parameter f (20;70) is less than 0.039 ppm / K and / or the alternative parameter f (-10;30) is less than 0.015 ppm / K.

[0117] Glass ceramics with a very flat expansion curve are very advantageous, since precision components can now be optimized not only for later application temperatures, but also for higher and / or lower temperature loads that may be expected, for example. T.i. is suitable for defining suitable materials according to the specifications required for a particular component application and for providing corresponding precision components, the specific precision components and their applications being described below and included herein.

[0118] According to an advantageous embodiment of the glass ceramic or a component made therefrom, the alternative parameter f (20;40)It may be advantageous if the expansion coefficient is less than 0.024 ppm / K, preferably less than 0.020 ppm / K, preferably less than 0.015 ppm / K. Hysteresis-free, zero-expansion components exhibiting such expansion behavior in the temperature range (20;40) can be particularly well used at room temperature as precision components for microlithography and EUV microlithography. An example of such an advantageous glass-ceramic is shown in FIG. 20.

[0119] According to an advantageous embodiment of the glass ceramic or a component made therefrom, the alternative parameter f (20;70) It may be advantageous if the thermal expansion coefficient is less than 0.039 ppm / K, preferably less than 0.035 ppm / K, preferably less than 0.030 ppm / K, preferably less than 0.025 ppm / K, preferably less than 0.020 ppm / K. Hysteresis-free, zero-expansion components exhibiting such expansion behavior in the temperature range (20;70) can also be particularly well suited for use as precision components for microlithography and EUV microlithography. It is particularly advantageous if the components also exhibit low thermal expansion when subjected to higher temperature loads, which may occur, for example, locally or over a large area, during the manufacture of precision components as well as during operation. Further details of the temperature loads occurring in EUVL precision components have already been given above in connection with the parameter F, and reference will be made here to this parameter F to avoid repetition. An example of such an advantageous glass-ceramic is shown in FIG. 21.

[0120] According to an advantageous embodiment of the glass ceramic or a component made therefrom, the alternative parameter f (-10;30)It may be advantageous if the expansion coefficient is less than 0.015 ppm / K, preferably less than 0.013 ppm / K, preferably less than 0.011 ppm / K. Hysteresis-free, zero-expansion components exhibiting such expansion behavior in the temperature range (-10; 30) can be particularly well used as precision components, in particular as mirror substrates for applications where temperatures below room temperature may also occur, for example in astronomy or Earth observation from outer space. Corresponding components are described below. An example of such an advantageous glass-ceramic is shown in FIG. 22.

[0121] A particularly advantageous embodiment of the glass ceramic or a component made therefrom is the alternative parameter f (T.i.) The expansion curve satisfies at least two of the above.

[0122] A particularly advantageous embodiment of the glass ceramic or a component made therefrom is characterized by the parameter F and the alternative parameter f (T.i.) The expansion curve satisfies at least one of the following:

[0123] 18 shows that an advantageous embodiment of the LAS glass ceramic and precision component has a CTE "plateau." Glass ceramics with a plateau, i.e., optimized zero expansion over a wide temperature range, offer the same advantages as already mentioned above in relation to the flat progression of the expansion curve and the parameter F.

[0124] The differential CTE has a plateau close to 0 ppm / K, i.e., a temperature range T P Advantageously, the differential CTE is less than 0±0.025 ppm / K at T P A temperature interval T having a width of at least 30 K or at least 40 K is called P In some cases, it may be advantageous for the differential CTE to be less than 0±0.015 ppm / K.

[0125] A CTE "plateau" is therefore understood to be the range extending over the section of the CTE-T curve where the differential CTE does not exceed 0±0.025 ppm / K, especially 0±0.015 ppm / K, more preferably 0±0.010 ppm / K, and even more preferably 0±0.005 ppm / K, i.e., a CTE around 0 ppb / K.

[0126] a temperature interval T having a width of at least 30 K or at least 40 K; P 18, it may be advantageous for the differential CTE to be less than 0±0.015 ppm / K, i.e., 0±15 ppb / K. In a preferred embodiment, a CTE plateau of 0±0.01 ppm / K, i.e., 0±10 ppb / K, may be formed over a temperature interval of at least 20 K, or at least 30 K, or at least 40 K, or at least 50 K. In FIG. 18, the curve even shows a CTE plateau of 0±0.005 ppm / K, i.e., 0±5 ppb / K, from −5° C. to 15° C., i.e., over a range of about 20 K.

[0127] Temperature interval T P It may be advantageous if the temperature is in the range of -10 to +100°C, particularly 0 to 80°C.

[0128] The position of the CTE plateau of glass ceramics is particularly important at the application temperature T A The preferred application temperature T A is in the range of -60°C to +100°C, more preferably -40°C to +80°C. Particular variations of the invention are applicable to application temperatures T of 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C and 100°C. A The CTE plateau, i.e., the temperature range T pThe curve range with small deviations of the differential CTE at can be in the temperature ranges of [-10; 100]; [0; 80], [0; 30°C], [10; 40°C], [20; 50°C], [30; 60°C], [40; 70°C] and / or [50; 80°C]. In further advantageous glass-ceramics or precision components, the CTE plateau can be in the temperature ranges of [-10; 30], [0; 50], [19; 25°C]; [20; 40] and / or [20; 70].

[0129] According to an advantageous embodiment of the invention, the CTE-T curve of the glass ceramic or precision component has at least one curve section with a small slope in a temperature range of at least 30 K, in particular at least 40 K, more preferably at least 50 K, and in particular a slope of at most 0±2.5 ppb / K. 2 , advantageously at most 0±2 ppb / K 2 , advantageously at most 0±1.5 ppb / K 2 , especially up to 0±1 ppb / K 2 , especially up to 0±0.8 ppb / K 2 , and according to certain variants even up to only 0±0.5 ppb / K 2 is.

[0130] The temperature range with a small slope is especially suitable for precision parts. A The preferred application temperature T A is in the range of -60°C to +100°C, more preferably -40°C to +80°C. Particular variations of the invention are applicable to application temperatures T of 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C and 100°C. A The temperature range with a small slope can be in the temperature ranges of [-10; 100], [0; 80], [0; 30°C], [10; 40°C], [20; 50°C], [30; 60°C], [40; 70°C] and / or [50; 80°C]. In further advantageous glass ceramics or precision parts, the temperature range with a small slope can be in the temperature ranges of [-10; 30], [0; 50], [19; 25°C], [20; 40] and / or [20; 70].

[0131] FIG. 19 shows the slope of the CTE-T curve in the temperature range of 0° C. to 45° C. for an advantageous glass ceramic or precision component based on the composition of Example 2 in Table 1. The slope of the CTE is 0±1 ppb / K over the entire temperature range. 2 less than 0±0.5 ppb / K over an interval of at least 20K 2 is less than.

[0132] Glass ceramics and precision components exhibiting such expansion behavior are particularly well suited for EUV lithography applications (e.g., as mirrors or substrates for mirrors or masks or mask blanks), since in this field increasingly high demands are placed on materials and precision components used in optical components with regard to extremely low thermal expansion, zero crossings of the CTE-T curve near the application temperature, and in particular a low slope of the CTE-T curve. Advantageous embodiments of the glass ceramics or precision components within the scope of the present invention exhibit a very flat CTE profile, which in addition to the zero crossings also exhibits a very low CTE slope and possibly also a very flat plateau.

[0133] The low slope feature can be present with or without the formation of a favorable CTE plateau.

[0134] By changing the ceramization temperature and / or ceramization time, the expansion curve or CTE profile can be adapted to various application temperatures. For example, by increasing or decreasing the ceramization temperature, the zero crossing of the CTE-T curve can be shifted and the expansion curve can be adjusted. Instead of increasing or decreasing the ceramization temperature, the ceramization time can also be increased or decreased as appropriate.

[0135] The preferred glass ceramics and precision components also have a good internal quality. 3A maximum of 5 inclusions per 100cm² is preferred. 3 Maximum of 3 inclusions per 100cm, most preferably 3 According to the invention, inclusions are understood to mean both bubbles and crystallites with a diameter of more than 0.3 mm.

[0136] According to one variant of the invention, the diameter or side length is at most 800 mm and the thickness is at most 100 mm, and the inclusions with a diameter greater than 0.03 mm are each 100 cm 3 A maximum of 5, in particular a maximum of 3, more preferably a maximum of 1 precision part per unit is provided.

[0137] In addition to the number of inclusions, the maximum diameter of the detected inclusions also serves as an indicator of the grade of internal quality. The maximum diameter of individual inclusions in the total volume of precision components with a diameter or side length of less than 500 mm is, in particular, at most 0.6 mm, and in application-critical volumes, e.g., near the surface, is, in particular, at most 0.4 mm. The maximum diameter of individual inclusions in glass-ceramic components with a diameter or side length of less than 500 mm to 2 m is, in particular, at most 3 mm, and in application-critical volumes, e.g., near the surface, is, in particular, at most 1 mm. This can be advantageous for achieving the surface quality required for the application.

[0138] The invention further relates to the use of the glass ceramics according to the invention in precision components. The glass ceramics can, for example, form the substrate of a precision component.

[0139] Furthermore, the invention relates to the use of the LAS glass ceramics according to the invention in precision parts, in particular in metrology, spectroscopy, measuring technology, lithography, astronomy or Earth observation from outer space, for example as mirrors or mirror supports for segmented or integrated astronomical telescopes, or also as lightweight or ultra-lightweight mirror substrates, for example for space-based telescopes, or as high-precision structural elements, for example for distance measurements in space, or for optical systems for Earth observation, as precision elements, for example standards for precision measuring technology, precision scales, reference plates in interferometers, mechanical precision parts, for example for ring laser gyroscopes, coil springs in the watch industry, as mirrors and prisms, for example in LCD lithography, and as mask holders, wafer stages, reference plates, reference frames and grid plates, for example in microlithography and EUV (extreme UV) microlithography, and also as mirrors or mirror substrates and / or photomask substrates or photomask blanks or reticle mask blanks for EUV microlithography.

[0140] The glass ceramics according to the invention can be used to manufacture precision components of various sizes.

[0141] One embodiment relates to precision parts with small dimensions, in particular with a side length (width and / or depth) in the case of polygons (rectangles) or a diameter in the case of circular surfaces of at least 50 mm, preferably at least 100 mm and / or at most 1500 mm, preferably at most 1000 mm, and / or a thickness of less than 50 mm, in particular less than 10 mm and / or at least 1 mm, more preferably at least 2 mm. Such precision parts can be used, for example, in microlithography and EUV lithography.

[0142] Another embodiment relates to precision components with very small dimensions, in particular with side lengths (width and / or depth) or diameters and / or thicknesses of a few mm (e.g., at most 20 mm, at most 10 mm, at most 5 mm, at most 2 mm or at most 1 mm) to a few tenths of a mm (e.g., at most 0.7 mm or at most 0.5 mm). Such precision elements can be, for example, spacers in interferometers or components of ultra-stable clocks in quantum technology.

[0143] However, very large precision parts can also be produced. Thus, one embodiment of the present invention relates to large-volume parts, which in the sense of the present application are understood to mean parts weighing at least 300 kg, in particular at least 400 kg, in particular at least 500 kg, in particular at least 1 t, more preferably at least 2 t, and in one variant of the invention at least 5 t, or parts which, in the case of polygons (rectangles), have a side length (width and / or depth) of at least 0.5 m, more preferably at least 1 m, and / or a thickness (height) of at least 50 mm, in particular at least 100 mm, preferably at least 200 mm, and even more preferably at least 250 mm, or parts which, in the case of circles, have a diameter of at least 0.5 m, more preferably at least 1 m, more preferably at least 1.5 m, and / or a thickness (height) of at least 50 mm, in particular at least 100 mm, preferably at least 200 mm, and even more preferably at least 250 mm.

[0144] In particular embodiments of the invention, the parts may be even larger, for example having a diameter of at least 3 m or at least 4 m or more and / or a thickness of 50 mm to 400 mm, preferably 50 mm to 300 mm. According to one variant, the invention also relates to rectangular parts, in particular parts having at least one side with a thickness of at least 1 m. 2 , especially at least 1.2 m 2 , more preferably at least 1.4 m 2 , and for some variants more preferably at least 3 m 2 Or at least 4m 2and / or a thickness of 50 mm to 400 mm, preferably 50 mm to 300 mm. Large volume parts are usually produced whose base area is significantly greater than their height. However, these can also be large volume parts with a shape approximating a cube or sphere.

[0145] The precision component may be, for example, an optical component, in particular a so-called normal incidence mirror, i.e., a mirror operating near normal incidence of radiation, or a so-called grazing incidence mirror, i.e., a mirror operating at a grazing incidence of radiation. Such mirrors comprise, in addition to a substrate, a coating that reflects the incident radiation. In particular, in the case of an X-ray mirror, the reflective coating is, for example, a multilayer system or multilayer having several layers with high reflectivity in the X-ray range at non-grazing incidence. Preferably, such a multilayer system for a normal incidence mirror comprises 40 to 200 pairs of alternating layers of one of the material pairs Mo / Si, Mo / Bi, Ru / Si, and / or MoRu / Be.

[0146] In particular, the optical element according to the invention may be an X-ray optical element, i.e. an optical element used in combination with X-rays, in particular soft X-rays or EUV radiation, in particular a reticle mask or photomask operating in reflection, in particular for EUV microlithography. Advantageously, this may be a mask blank. Even more advantageously, the precision component can be used as a mirror for EUV lithography or as a substrate for a mirror for EUV lithography.

[0147] Furthermore, the precision component according to the invention may be a component, in particular a mirror for astronomy applications, where such astronomy components can be used both on the ground and in space, and a further advantageous application area is, for example, high-precision structural elements for distance measurement in space.

[0148] The precision part according to the present invention may have a lightweight structure. The part according to the present invention may further include a lightweight structure. This means that cavities are provided in some areas of the part to reduce the weight. In particular, the weight of the part is reduced by at least 80%, more preferably at least 90%, by lightweight processing compared to the unprocessed part.

[0149] The subject of the present invention is also a precision component comprising the LAS glass ceramic according to the invention, the details of which have already been mentioned above in connection with the glass ceramic and its use in precision components, the disclosure of which is fully included in the description of the precision component.

[0150] It will be appreciated that the features of the invention mentioned above and those to be described below can be used in other combinations than those shown, without departing from the scope of the invention.

[0151] Example Tables 1 and 2 show the compositions of examples of glass ceramics according to the present invention and comparative examples, as well as their properties.

[0152] The compositions shown in Table 1 were melted by conventional manufacturing methods from commercially available raw materials such as oxides, carbonates, and nitrates. The green glasses produced according to Table 1 were first ceramized at the maximum temperatures shown for the times shown.

[0153] The production of precision components, in particular large precision components, from glass ceramics is described, for example, in WO 2015 / 124710.

[0154] Table 1 lists four examples (embodiments) of the present invention that are hysteresis-free and have zero expansion at least in the temperature range from 15°C to 35°C. Examples 1 to 4 exhibit thermal hysteresis below approximately 15°C. Furthermore, the parameter F is less than 1.20, i.e., the progression of the expansion curve in the temperature range from 0°C to 50°C is advantageously flat in all examples. Furthermore, the examples have processing temperatures of ≦1330°C, which allows the glass-ceramics to be produced with high uniformity in large-scale production plants. The processing temperatures listed in Tables 1 and 2 were determined in accordance with DIN ISO 7884-1 (2014 - Source: Schott Techn Glas-Katalog).

[0155] In Example 1, after ceramization for 2.5 days at up to 815°C, the average CTE was measured at additional temperature intervals, with the following results: CTE(20; 300°C): 0.39 ppm / K, CTE(20; 500°C): 0.68 ppm / K, CTE(20; 700°C): 0.94 ppm / K.

[0156] Table 2 shows comparative examples (denoted as Comparative Examples). Comparative Examples 1 and 2 have neither MgO nor ZnO, but the average CTE(0;50) is 0±0.1×10 -6 / K, i.e., these comparative examples are not zero-expansion. Furthermore, Comparative Examples 1 and 2 have processing temperatures above 1330°C. Because these materials are very viscous, they cannot be used to fabricate parts with high uniformity in large-scale production plants.

[0157] Comparative Examples 3 and 7 to 16 all contain MgO and / or ZnO, and most of them have zero thermal expansion. However, these comparative examples exhibit thermal hysteresis far exceeding 0.1 ppm at least in the temperature range of 15°C to 35°C. At room temperature, i.e., 22°C, all comparative examples exhibit thermal hysteresis, except for Comparative Examples 14 and 16. Furthermore, although Comparative Example 9 has zero thermal expansion, it has an undesirably steep transition in the expansion curve in the temperature range of 0°C to 50°C, as evidenced by the large value of parameter F. Comparative Example 3 contains a relatively small amount of the sum of MgO and ZnO but does not contain RO. It exhibits thermal hysteresis far exceeding 0.1 ppm at least in the temperature range of 15°C to 35°C. Furthermore, the expansion curve is strongly curved, as evidenced by the large value of parameter F.

[0158] In the tables below, if a column for composition data is blank, this means that the ingredient(s) is / are not intentionally added or included.

[0159] Table 3 shows the calculated alternative parameters f for each temperature interval for two advantageous embodiments of the present invention and one comparative example. (T.i.) , which shows that the expansion curves of the Examples in the indicated temperature ranges show a flatter progression than the Comparative Examples, respectively.

[0160] It is clear to those skilled in the art that depending on the application temperature of the glass-ceramic or precision component containing the glass-ceramic, a glass-ceramic is selected that has the desired properties, in particular with regard to thermal hysteresis and / or average CTE.

[0161] [Table 5]

[0162] [Table 6-1]

Table 6-2

Table 6-3

[0163]

Table 7

Claims

1. LAS glass ceramics having an average coefficient of thermal expansion (CTE) of 0±0.1×10 at most from 0 to 50°C －６ / K, and has a thermal hysteresis of less than 0.1 ppm over a temperature range of at least 15°C to 35°C, and contains the following components (in mole % on an oxide basis): Yes ２ 60~68.5 Li ２ O7~9.6 MgO+ZnO >0.5~1.5 R ２ O >0.5 K ２ O at least 0.05 Here, R ２ O is Na ２ O and / or K ２ O and / or Cs ２ O and / or Rb ２ O, Nucleating agent: 1.5-6 mol % content, where the nucleating agent is TiO ２ , ZrO ２ , Ta ２ O ５ , Nb ２ O ５ , SnO ２ , MoO ３ , W.O. ３ , HfO ２ and at least one component selected from the group consisting of: LAS glass ceramics, including

2. LAS glass ceramics having an average coefficient of thermal expansion (CTE) of 0±0.1×10 at most from 0 to 50°C －６ / K, and has a thermal hysteresis of less than 0.1 ppm over a temperature range of at least 15°C to 35°C, and contains the following components (in mole % on an oxide basis): Yes ２ 60~68.5 Li ２ O7~9.6 MgO+ZnO >0.5~1.5 R ２ O >0.5 P ２ O ５ At least 0.1 Here, R ２ O is Na ２ O and / or K ２ O and / or Cs ２ O and / or Rb ２ O, Nucleating agent: 1.5-6 mol % content, where the nucleating agent is TiO ２ , ZrO ２ , Ta ２ O ５ , Nb ２ O ５ , SnO ２ , MoO ３ , W.O. ３ , HfO ２ and at least one component selected from the group consisting of: LAS glass ceramics, including

3. The LAS glass ceramics is Al ２ O ３ in a content of 10 to 22 mol %, preferably 11 to 21 mol %, and / or P ２ O ５ 2. The LAS glass ceramic according to claim 1, wherein the LAS glass ceramic contains 0 to 6 mol %, preferably 0.1 to 5 mol % of

4. 3. The LAS glass ceramic according to claim 1 , wherein the total content of ZnO+MgO is at least 0.55 mol%, preferably at least 0.6 mol%, advantageously at least 0.65 mol%, at least 0.7 mol% and / or preferably less than 1.5 mol%, in particular at most 1.45 mol%, preferably at most 1.4 mol%, preferably at most 1.35 mol%, preferably at most 1.3 mol%, preferably at most 1.25 mol%, preferably at most 1.2 mol%, and / or the MgO content is at most 1.1 mol%, preferably at most 1.05 mol%, preferably at most 1.0 mol%, preferably at most 0.95 mol%, more preferably at most 0.9 mol%, and / or the ZnO content is at most 1.5 mol%, preferably at most 1.45 mol%, preferably at most 1.4 mol%, preferably at most 1.35 mol%, preferably at most 1.3 mol%, more preferably at most 1.25 mol%.

5. 3. The LAS glass ceramic according to claim 1, wherein the content of the sum of the RO components (CaO + BaO + SrO) is at least 0.1 mol%, in particular at least 0.2 mol%, advantageously at least 0.3 mol%, preferably at least 0.4 mol% and / or at most 6 mol%, in particular at most 5 mol%, advantageously at most 4.5 mol%, advantageously at most 4.0 mol%, preferably at most 3.8 mol%, preferably at most 3.5 mol%, preferably at most 3.2 mol%.

6. The R ２ Total of O (Na ２ O+K ２ O+Cs ２ O+Rb ２ 2. The LAS glass ceramic according to claim 1, wherein the content of 0 is at least 0.55 mol%, in particular at least 0.6 mol%, preferably at least 0.65 mol%, preferably at least 0.7 mol%, in particular at least 0.75 mol% and / or at most 6 mol%, preferably at most 5 mol%, preferably at most 4 mol%, preferably at most 3 mol%, preferably at most 2.5 mol%, preferably at most 2 mol%.

7. 3. The LAS glass ceramic according to claim 1, wherein the total content of nucleating agents is at least 1.5 mol%, in particular at least 2.5 mol%, preferably at least 3 mol% and / or at most 6 mol%, preferably at most 5 mol%, preferably at most 4.5 mol%, preferably at most 4 mol%.

8. The following conditions: SiO ２ Molar content of + (5 × Li ２ O) ≥ 105, preferably ≥ 105.5, preferably ≥ 106, in particular SiO ２ Molar content of + (5 × Li ２ and / or The following conditions: SiO ２ Molar content of + (5 × Li ２ O molar content)≦115.5, especially SiO ２ Molar content of + (5 × Li ２ 2. The LAS glass ceramic according to claim 1, wherein the molar content of O is ≦114.

5.

9. 3. The LAS glass ceramic according to claim 1, wherein the processing temperature Va is at most 1330°C, preferably at most 1320°C.

10. 3. The LAS glass ceramic according to claim 1, wherein the main crystalline phase is a high-quartz solid solution, wherein the average crystallite size of the high-quartz solid solution is preferably less than 100 nm, advantageously less than 80 nm, preferably less than 70 nm, and / or the crystalline phase proportion is less than 75% by volume.

11. 3. The LAS glass ceramic according to claim 1, wherein the parameter F is less than 1.20, preferably less than 1.15, preferably less than 1.10, and preferably at most 1.05, where F = TCL(0; 50 ° C) / |Expansion(0; 50 ° C)|.

12. Alternative parameter f （２０；４０） is less than 0.024 ppm / K, and / or the alternative parameter f （２０；７０） is less than 0.039 ppm / K, and / or the alternative parameter f （－１０；３０） 3. The LAS glass ceramic according to claim 1, wherein the LAS content is less than 0.015 ppm / K.

13. The LAS glass ceramic has a relative length change (dl / l) of |0.10| ppm or less, preferably |0.09| ppm or less, particularly preferably |0.08| ppm or less, and particularly preferably |0.07| ppm or less in the temperature range of 20°C to 30°C. ０ ) and / or a relative length change (dl / l) of |0.17| ppm or less, preferably |0.15| ppm or less, particularly preferably |0.13| ppm or less, and especially preferably |0.11| ppm or less in the temperature range from 20° C. to 35° C. ０ 3. The LAS glass ceramic according to claim 1, wherein the LAS glass ceramic has a crystalline structure.

14. The LAS glass ceramic has a relative length change (dl / l) of |0.30| ppm or less, preferably |0.25| ppm or less, particularly preferably |0.20| ppm or less, and particularly preferably |0.15| ppm or less in the temperature range from 20°C to 40°C. ０ 3. The LAS glass ceramic according to claim 1, wherein the LAS glass ceramic has a crystalline structure.

15. 0±2.5 ppb / K in a temperature range where the CTE-T curve has a width of at least 30 K ２ or less, preferably 0±2 ppb / K ２ or less, preferably 0±1.5 ppb / K ２ Below 0±1 ppb / K, particularly preferably ２ 3. The LAS glass ceramic according to claim 1, having the following slope:

16. 3. The LAS glass ceramic according to claim 1, wherein the LAS glass ceramic exhibits a thermal hysteresis of less than 0.1 ppm in a temperature range of at least 15°C to 40°C, advantageously in a temperature range of at least 15°C to 45°C, preferably in a temperature range of at least 15°C to 50°C.

17. 3. Use of the LAS glass ceramics according to claim 1 or 2 in precision components, in particular in metrology, spectroscopy, measuring technology, lithography, astronomy or Earth observation from outer space, for example as mirrors or mirror supports for segmented or integrated astronomical telescopes, or also as lightweight or ultra-lightweight mirror substrates, for example for space-based telescopes, or as high-precision structural elements, for example for distance measurements in space, or as optical systems for Earth observation, as precision elements, for example standards, precision scales, reference plates for precision measuring technology, for example for ring laser gyroscopes, as coil springs in the watch industry, as mirrors and prisms, for example in LCD lithography, and as mask holders, wafer stages, reference plates, reference frames and grid plates, for example in microlithography and EUV microlithography, and also as mirrors and / or photomask substrates, photomask carriers or reticle mask blanks in EUV microlithography.

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