Precision component with highly homogeneous cte

Abstract

The invention relates to precision components having highly homogeneous thermal expansion properties, a method to produce such precision components and the use thereof.

Description

[0001] Applicant: SCHOTT AG February 17, 2026 Our File: P06322 WO

[0002] Official File No:

[0003] - 1 -

[0004] Precision Component with highly homogeneous CTE The invention relates to precision components having highly spatial homogeneous thermal expansion properties, a method to produce such precision components and the use thereof.

[0005] Technical Background

[0006] EUV Lithography

[0007] Extreme UV lithography (also called EUVL hereinafter) is a photolithography process utilizing electromagnetic radiation between typically 5 nm and 50 nm (soft x-ray radiation), more particularly electromagnetic radiation having a wavelength of 13.5 nm (91.82 eV). This is the so-called extreme ultraviolet radiation (EUV). This region of the electromagnetic spectrum is absorbed completely by virtually all materials. In contrast to DUV lithography (deep ultraviolet, for example at wavelengths of 248 nm or 193 nm), it is therefore not possible to use optically transparent photomasks. Instead, reflective multilayer stack systems have to be used on a photomask substrate of low thermal expansion (also called reticle substrate or mask substrate or reticle mask blank or photomask blank or mask blank or substrate hereinafter) as photomasks (also called reticles, reticle masks, photomasks or masks hereinafter). A disadvantage when using reflective photomasks, however, is the comparatively poor maximum reflectivity of the multilayer stack in the EUV radiation range, of typically less than 70%. Any radiation not reflected by the photomask is absorbed by the photomask and conducted in the form of heat into the photomask substrate and, where relevant, into the photomask carrier (also called reticle carrier or mask carrier or reticle stage or photomask stage or mask stage hereinafter), possibly raising the temperature thereof, especially with increasing irradiation time.

[0008] Even slight thermally induced deformations in the photomask, however, can lead to imaging errors on the illuminated wafer and hence to yield losses during chip production. To prevent the described local deformations or distortions in the photomask substrate, therefore, it is necessary to use materials of low thermal expansion or of low CTE (coefficient of thermal expansion) for photomask substrates.

[0009] This is all the more important because the average power of the EUV beam sources used in EUV lithography will increase in future in order to boost the throughput, via higher repetition rates and / or higher individual pulse energies, for example, with a consequent increase in the thermal load on the photomask and also, where relevant, on the photomask carrier. As a result, active cooling concepts for the photomask and for the photomask carrier will gain in importance, possibly leading to further temperature changes particularly in the photomask and theFebruary 17, 2026

[0010] - 2 -photomask carrier. In this context, it must also be borne in mind that the thermal load on the photomask and / or photomask carrier is not constant but may instead fluctuate due to a variety of factors. These factors include temporally nonuniform illumination times, resulting, for example, from the loading of the photomask carrier with a new photomask or from downtimes due to faltering operations. The stated thermally induced deformations may be compensated in part by compensation mechanisms within the overall optical system of an EUV lithography unit, such as in the beam shaping of the illumination, for example. However, this compensation is limited, and it is therefore useful to minimize the individual contributions to (imaging) errors. Here it is necessary to consider not only thermally induced deformations of the material during illumination, but also the thermal characteristics overtime (thermal hysteresis). Materials having comparatively high thermal hysteresis, however, hinder the stated compensation and hence also the prevention of unwanted thermal imaging errors on the part of the photomask.

[0011] Further precision ELIVL components with exacting requirements in terms of their thermal properties are, in particular, ELIVL mirrors in the optical system of the ELIVL apparatus and also wafer carriers (also called wafer stages hereinafter) onto which the (Si-) wafers are placed for exposure.

[0012] Precision Materials

[0013] Materials and precision components featuring low thermal expansion are already known in the prior art. Known materials for such precision components are ceramics, Ti-doped quartz glass, and glass-ceramics. Glass-ceramics featuring low thermal expansion are, in particular, lithium aluminum silicate glass-ceramics (LAS glass-ceramics), which are described, for example, in US 4,851 ,372, US 5,591,682, EP 587979 A, US 7,226,881, US 7,645,714, DE 102004008824 A, and DE 102018111144 A. Further materials for precision components are cordierite ceramics or cordierite glass-ceramics.

[0014] The demands made in terms of the homogeneity of low thermal expansion components for precision applications increase constantly and therefore continuous development is required to improve the homogeneity of low thermal expansion precision materials.

[0015] A high (spatial) CTE homogeneity of a glass, glass-ceramic or ceramic material is believed to be closely related to a highly homogeneous distribution of the various components in the material. In case of glass-ceramics, a maximum homogeneous distribution of the components should be aimed at in the melt and in the green glass from which the glass-ceramic material is produced by ceramization. Efforts to improve the CTE homogeneity of a glass-ceramic material therefore have been directed to improve the homogeneous distribution of components in the melt. ThusFebruary 17, 2026

[0016] - 3 - WO 2015 / 124710 describes measures to improve CTE homogeneity by improving the homogeneity of the melt and the green glass. It was possible to substantially improve the CTE homogeneity of ZERODUR from about 10 ppb / K to values as low as 5 and 3 ppb / K depending on the size of the component.

[0017] It was, however, not until now possible to further improve the CTE homogeneity of glass-ceramic components to demanded CTE- homogeneities of 2 ppb / K and less by improvements during production of the green glass blanks.

[0018] The CTE is usually given as the mean CTE in a specific temperature interval, e.g. between 0 and 50°C, however, the actual CTE is a function depending on the temperature as further explained below. Usually, the optimum CTE for a certain application temperature is required and can in a certain range be set by the ceramizing conditions, as e.g. described in EP 1 321 440 A. However, the accuracy of this process was not sufficient for advanced applications.

[0019] Object of the invention

[0020] It was therefore the object of the invention to provide near zero thermal expansion precision components which have an even higher CTE homogeneity e.g. of less than 3 ppb / K and to provide measures which can be used to achieve such an improvement of CTE homogeneity. It was a further object of the invention to provide near zero thermal expansion precision components with a highly optimized CTE and measures to provide such components.

[0021] Aspects of the invention

[0022] This object is achieved by the embodiments described in the claims.

[0023] In particular, according to a first aspect, the invention relates to a precision component, comprising a linear coefficient of thermal expansion CTE(0;50) of at most 0 ± 20 ppb / K or at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K, and a spatial CTE(0;50) homogeneity of

[0024] at most 1 ,8 ppb / K for components with a surface diameter or edge length of less than to 500 mm, or

[0025] less than 3 ppb / K for components with a surface diameter or edge length of at least 500 mm.

[0026] According to a second aspect, the invention relates to a method of manufacturing precision components comprising the steps of

[0027] melting a batch of raw materials to form a green glass melt in a melting vessel (6) wherein the melting vessel (6) is heated using two or more heating circuits, each comprising aFebruary 17, 2026

[0028] -4- transformer (3) and at least two electrodes (5), wherein at least one heating circuit comprises an inverter (1) providing an alternating current (AC) to its heating circuit, withdrawing the green glass melt from the melting vessel (6),

[0029] forming the green glass melt into a green glass block,

[0030] optionally, machining the green glass block into the shape of a precision component, ceramizing the green glass to a glass ceramic,

[0031] optionally, polishing at least one surface of the precision component,

[0032] optionally, coating the polished surface of the precision component with a reflective coating.

[0033] According to a third aspect, the invention relates to a method of ceramizing a green glass component into a glass ceramic, comprising the steps:

[0034] providing a set of green glass blocks,

[0035] determining the characteristic temperature for ceramizing a first green glass block of said set of green glass blocks to a glass-ceramic, whereas said characteristic temperature is determined by measuring the temperature on the glass block and the oven temperature and determining the difference of these temperatures,

[0036] applying the so determined characteristic temperature to (a) control the oven temperature and / or (b) the holding time during the ceramization of further blocks of the set of green glass blocks.

[0037] According to a forth aspect, the invention relates to a use in metrology, spectroscopy, measurement technology, lithography, astronomy or Earth observation from space, for example as mirror or mirror carrier for segmented or monolithic astronomical telescopes or else as weight-reduced or ultra-light mirror substrates for, for example, space-based telescopes or as high-precision structure components for measurement of distance, for example in space, or optics for Earth observation, as precision components, such as standards for precision measurement technology, precision rules, reference plates in interferometers, as mechanical precision parts, for example for ring laser gyroscopes, spiral springs for the clock industry, as for example mirrors and prisms in LCD lithography, and for example as mask holders, wafer stages, reference plates, reference frames and grid plates in microlithography and in EUV microlithography, and as mirrors and / or photomask substrates, photomask carriers or reticle mask blanks in EUV microlithography.

[0038] According to a fifth aspect, the invention relates to a precision component, comprising a linear coefficient of thermal expansion CTE(19;25) of at most 0 ± 2 ppb / K or at most 0 ± 1 ppb / K or at most 0 ± 0.5 ppb / K, and, optionally, a spatial CTE(0;50) or CTE(19;25) homogeneity ofFebruary 17, 2026

[0039] - 5 - at most 1 ,8 ppb / K for components with a surface diameter or edge length of less than to 500 mm, or

[0040] less than 3 ppb / K for components with a surface diameter or edge length of at least 500 mm.

[0041] These and other aspects and objects, features and advantages of the present invention will become apparent upon a consideration of the following detailed description and the invention when read in conjunction with the Figures.

[0042] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention and are intended to provide an overview or framework for understanding the nature and character of the invention as claimed.

[0043] Brief description of the Figures

[0044] Figure 1 schematically shows a melting furnace with three heating circuits.

[0045] Figure 2 schematically shows a schematic representation of a ceramizing program for an LAS glass ceramic.

[0046] Figure 3a to 3c shows the expansion behavior of a glass-ceramic according to Example 2, whereas Figure 2b shows the Al / Io-T curve, Figure 3b shows the corresponding CTE -T curve and Figure 3c shows the dCTE / dT-T curve, i.e. the slope of the CTE-T curve.

[0047] Figure 4 schematically shows a precision component 40 and test samples 44 to be cut out of a blank 42.

[0048] Detailed description of the invention

[0049] Coefficient of Thermal Expansion CTE

[0050] The Coefficient of Thermal Expansion (CTE) describes how the size of an object changes with a change in temperature. In the context of this application, “CTE” means the linear coefficient of thermal expansion also denoted as a. “CTE” and “a” are used interchangeably in this application.

[0051] The CTE can firstly be specified as the “mean CTE” or “average CTE” of a material or component in a given temperature interval. The mean CTE can e.g. be determined by a static method in which the length of a test specimen is determined at the start and at the end of a temperatureFebruary 17, 2026

[0052] - 6 -interval, and the difference in length is used to calculate the mean CTE in this temperature interval. A typical temperature interval for the determination of the mean CTE is temperature interval from 0°C to 50°C and when this temperature interval is used the CTE is denoted as CTE(0;50) or a(0;50).

[0053] The mean CTE may be determined not only for the temperature interval CTE(0;50) but also, for example, for a temperature interval around the application temperature of a component, such as for example the interval from 19°C to 25°C, resulting in a mean CTE(19;25).

[0054] The components provided according to the invention show “(near) zero expansion”, meaning that they have a mean coefficient of thermal expansion CTE in the range from 0 to 50°C of at most 0 ± 0.02 x 10'6 / K or at most 0 ± 0.01 x 10'6 / K or at most 0 ± 0.007 x 10'6 / K or at most 0 ± 0.005 x 10-6 / K or at most 0 ± 0.002 x 106 / K, whereas e.g. “0 ± 0.002 x 10’6 / K” can also be written as “0 ± 0.002 ppm / K” or “0 ± 2 ppb / K” or “0 ± 2 ppb / °C”.

[0055] For particular applications, it may be advantageous to specify the mean CTE within a different temperature range, in particular, for a temperature interval around the actual application temperature of a material or component, for example, in the temperature interval from -30°C to +70°C or from -40°C to +80°C or from 19°C to 25°C. Also in these ranges, the mean CTE may have a value of at most 0 ± 0.02 x 10'6 / K or at most 0 ± 0.01 x 10'6 / K or at most 0 ± 0.005 x 10'6 / K or at most 0 ± 0.002 x 10-6 / K. If the mean CET was determined e.g. in the temperature interval from 19°C to 25°C, it is then denoted as CTE(19;25).

[0056] The CTE can also be determined as a function of the temperature, i.e. as the differential CTE(T). The differential CTE(T) is defined according to the following formula (1):

[0057] CTE (T) = (1 / Io) x (3 I / ST) (1)

[0058] The graph of the function CTE(T) - T is also called CTE-T curve in this application and shows the temperature dependency of the differential CTE(T). A CTE-T curve can be obtained by differentiation of the AI / lo-T curve or expansion curve or plot of the change in length Al / lo of a test specimen against the temperature.

[0059] For the creation of a Al / Io-T curve, the temperature-dependent change in length of a test specimen from the starting length l0at the initial temperature to to the length ltat the temperature t is measured. Here, preferably, small temperature intervals of 5 K or 3 K or 1 K or even less than 1 K, for example, are chosen for determining a measurement point. Such measurements may beFebruary 17, 2026

[0060] - 7 -carried out, for example, by dilatometry methods, interferometry methods, such as for example the Fabry-Perot method, i.e., the evaluation of the shift in the resonance peak of a laser beam injected into the material, or other suitable methods.

[0061] The chosen method of determining the CTE should have an accuracy of at least ± 3 ppb / K or at least ± 1 ppb / K or at least 0.5 ppb / K or at least 0.3 ppb / K or at least 0.1 ppb / K.

[0062] The AI / lo-T curve also can be used to calculate the mean CTE for a particular temperature interval.

[0063] The AI / lo-T curve can furthermore be used to determine the total change of length “TCL” within a temperature interval. The “total change of length” or “TCL” value is the distance between the highest dl / l0value and the lowest dl / l0value within a given temperature range, e.g. the temperature range of from 0°C (starting temperature) to 50°C:

[0064] TCL (0;50°C) = | dl / l0max. | + | dl / l0min.| (2)

[0065] where “dl” denotes the change in length at the respective temperature and “l0“ denotes the length of the test specimen at 0°C, as the starting and / or lowest temperature for TCL(0;50°C). The calculation is based in each case on the magnitudes of the dl / lo values.

[0066] Within the context of the invention, the TCL value can be reported for the temperature range of 0°C and 50°C and / or in the range of from 10 to 30°C and / or in the range of from 20 to 24°C and / or in the range of from 20 to 60°C. It is ascertained from the normalized AI / lo-T curve, with “normalized” meaning that the change in length at 0°C is set to 0 ppm for TCL(0;50), or set at 10°C for TCL(10;30), or set at 20°C for TCL(20;24) and TCL(20;60).

[0067] The TCL(0;50) preferably is in the range of at most 100 ppb or at most 50 ppb or at most 40 ppb or at most 20 ppb. The TCL(10;30) preferably is in the range of at most 50 ppb or at most 40 ppb or at most 20 ppb or at most 10 ppb or at most 5 ppb. The TCL(20;24) preferably is in the range of at most 20 ppb or at most 10 ppb or at most 5 ppb or at most 2 ppb or at most 1 ppb or less than 1 ppb. The TCL(20;60) preferably is in the range of at most 100 ppb or at most 50 ppb or at most 40 ppb or at most 20 ppb or at most 10 ppb or at most 5 ppb.

[0068] Further details of the thermal expansion of a material or component can be derived from the CTE-T curve such as the zero crossing of the CTE-T curve and the slope of the CTE-T curve.February 17, 2026

[0069] - 8 - A CTE-T curve preferably has at least one or two or three or more zero crossing, i.e. temperatures at which of the CTE-T curve crosses the T-axis and the CTE is 0 ppb / K. Around the temperature of such a zero-crossing, the glass-ceramic or component shows the least expansion with a temperature change. Zero crossings of the CTE-T curve are therefore preferred around the application temperature of the glass-ceramic or component such as e.g. zero crossings in the temperature range of from 20°C to 24°C, i.e. ambient temperature.

[0070] The CTE-T curve is also used to determine the shaping and position of a so-called CTE plateau.

[0071] CTE-T curve of a glass-ceramic or component having a “CTE plateau” means that the component shows an optimized zero expansion over a certain temperature range. The location of a CTE plateau is defined by its start temperature Tp(start) and its end temperature Tp(end) on the temperature axis of the CTE-T graph and by the width of the plateau whereas Tp(end) - Tp(start) = width of CTE plateau [K], e.g. a CTE plateau may start at 10°C and end at 50°C having a width of 40 K or 40°C. “Optimized zero expansion” means that the differential CTE across the width of the CTE plateau (i.e. from Tp(start) to Tp(end)) only varies in an very small amount close to 0 ppb / K and / or that the slope of the CTE-T curve across the width of the CTE plateau is 0 ppb / K2or close to 0 ppb / K2. For example, the differential CTE may vary across the width of the CTE plateau at most 0 ± 20 ppb / K or at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K or at most 0 ± 2 ppb / K. The slope of the CTE-T curve may vary across the width of the CTE plateau at most 0 ± 2.5 ppb / K2or at most 0 ± 2 ppb / K2or at most 0 ± 1.5 ppb / K2or at most 0 ± 1 ppb / K2or at most 0 ± 0.8 ppb / K2or at most 0 ± 0.5 ppb / K2.

[0072] A CTE plateau advantageously includes the application temperature (range) of the glass ceramic or the component, e.g. a CTE plateau typically be located within the range of from 0 to 100°C. The CTE plateau preferably has a width of at least 20 K or at least 30 K or at least 40 K or at least 50 K or at least 60 K. Preferably the width of the CTE plateau overlaps or covers the application temperature range of the glass ceramic or component.

[0073] Examples of CTE-plateaus within the temperature range of from 0°C to 100°C may have a width of at least 20 K and a CTE variation of at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K or at most 0 ± 3 ppb / K; or a width of at least 30 K and a CTE variation of at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K or at most 0 ± 3 ppb / K or at most 0 ± 1 ppb / K; or a width of at least 40 K and a CTE variation of at most 0 ± 20 ppb / K or at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K or at most 0 ± 3 ppb / K or at most 0 ± 1 ppb / K or at most 0 ± 0.5 ppb / K; or any other combination.February 17, 2026

[0074] - 9 -

[0075] Figure 3a to 3c shows the above-described thermal expansion behaviour of a glass ceramic according to Material 2.

[0076] In Figure 3a the Al / lo curve of the glass ceramic is shown. The Al / lo curve is extremely flat and the material exhibits a TCL(0;50) of 16 ppb in the range of from 0 to 50°C and a TCL(15;30) of 6,5 ppb in the range of from 15 to 30°C. The TCL(20;24) in the range of from 20 to 24 is zero in the context of measurement inaccuracy.

[0077] Figure 3b depicts the first derivative of the Al / lo curve, namely the CTE-T curve. This glass-ceramic shows a zero crossing of the CTE-T curve at 23°C. The glass ceramic shows a CTE plateau in the range of 15 to at least 45°C having a width of at least 30 K in which a CTE varies less than 0 ± 2 ppb. The glass ceramic also shows a CTE plateau in the range of 20 to 50 °C having a width of 30 K in which the CTE varies less than 0 ± 1 ppb.

[0078] Figure 3c shows the derivative of the CTE-T curve corresponding to the slope of the CTE-T curve. The slope at the zero-crossing temperature of 24°C is -0,25 ppb / K2. Furthermore, the slope of the CTE-T curve at the CTE plateau between 30°C and 40°C having a width of 10 K is less than 0,05 ppb / K2.

[0079] Spatial homogeneity of thermal expansion properties

[0080] The present invention relates to precision components with spatial homogeneous thermal expansion properties, i.e. even if the thermal expansion properties are measured at different locations of the precision component, these thermal expansion properties only vary to a very small amount. With “spatial homogeneous thermal expansion properties” or “total spatial variation of thermal expansion properties” the so-called “peak-to-valley value”, i.e. the difference between the respective highest and lowest value of a given thermal expansion property measured at different locations of a precision component is meant.

[0081] The spatial homogeneity of all of the above discussed thermal expansion properties can be determined for a precision component, for example, the spatial homogeneity of the mean CTE, a CTE-plateau, the zero crossing of a CTE-T curve or the slope of the CTE-T curve at the zero crossing of the CTE-T curve can be determined and specified.

[0082] To determine the spatial homogeneity of a thermal expansion property, said thermal expansion property is measured at at least two different locations of a precision component. Preferably,February 17, 2026

[0083] - 10 -such measurement is performed at at least 6 or at least 10 or even at more than 15 different locations of a precision component.

[0084] For such measurements, preferably a non-destructive CTE measurement method is used. Alternatively, two or more samples from different locations of the precision components can be used to determine the spatial homogeneity of the thermal expansion properties.

[0085] Since it is usually desirable to cut samples from a precision component itself, such samples 14 can be taken from the blank 12 from which the precision component 10 is produced within the scope of raw glass machining as shown in Figure 4. These samples 14 can then be laid out near the unceramized precision component in the ceramization furnace and ceramized together with the precision component. These samples represent a sufficient representation of the spatial fluctuations of the thermal expansion properties and can thus be used to determine the spatial distribution of the thermal expansion properties of a precision component.

[0086] Frist of all, the “spatial homogeneity of the linear mean CTE” or CTE homogeneity can be determined.

[0087] The (spatial) CTE homogeneity for the temperature range from 0°C to 50°C, i.e. , the spatial variation of the linear mean CTE(0;50), is also called CTE homogeneity(0;50) below. The CTE homogeneities for other temperature ranges may be identified analogously. Thus, for example, the CTE homogeneity for the temperature range from 19°C to 25°C, i.e., the spatial variation of the linear mean CTE(19;25), is also called CTE homogeneity(19;25) below.

[0088] In some embodiments, the precision component provided according to the invention has a CTE homogeneity(0;50) over the entire precision component of less than 3 ppb / K or at most 2.5 ppb / K or at most 2 ppb / K or less than 2 ppb / K or at most 1.75 ppb / K or at most 1.5 ppb / K and / or a CTE homogeneity(19;25) over the entire precision component of less than 2 ppb / K, or at most 1.9 ppb / K ppb / K or at most 1.75 ppb / K or at most 1.5 ppb / K or at most 1 ppb / K.

[0089] The CTE homogeneity depends on the size of the precision component. It is easier to achieve a highly homogeneous CTE in a smaller precision component and increasingly difficult with increasing size of the precision component.

[0090] As shown in Figure 4, a precision component 40 usually has a top and bottom surface with, in case of components having a round or ellipsoid surface, i.e. cylindric components, has a (surface) diameter D and a height h. In case of cubic or cuboid precision components, either theFebruary 17, 2026

[0091] - 11 -diagonal or the edge length of a top and bottom surface can be defined in addition to the height h of the components. Precision components or blanks therefore may have planar surfaces and simple geometric forms as shown in Figure 4. According to further embodiments, they have concave or convex surfaces or any other irregular shapes. In case a component has either more than one (surface) diameter, e.g. in case of ellipsoid components, or, in case of (rect)angular or polygona components, edges and / or diagonals with different length, the maximum diameter, edge length or diagonal, respectively, is the relevant parameter.

[0092] One embodiment relates to precision components with small dimensions i.e. components with a surface diameter or edge length of less than 500 mm, in particular in the case of (rect)angular shapes with edge lengths (width and / or depth) or with round surfaces with diameters of at least 50 mm or at least 100 mm and / or a less than 500 mm or less than 400 mm and / or a thickness of at most 50 mm or less than 20 mm or less than 10 mm and / or at least 1 mm or at least 2 mm or at least 5 mm.

[0093] One embodiment relates to precision components with very small dimensions, in particular with edge lengths (width and / or depth) or diameters and / or thicknesses of a few mm (for example less than 50 mm or at most 40 mm or at most 20 mm or at most 10 mm or at most 5 mm or at most 2 mm or at most 1 mm) to a few tenths of a mm (for example at most 0.7 mm or at most 0.5 mm). These precision elements can be, for example, a spacer, for example in an interferometer, or a component for ultra-stable clocks in quantum technology.

[0094] Such small or very small precision components with a surface diameter or edge length of less than 500 mm show a CTE homogeneity of at most 1.8 ppb / K or at most 1.5 ppb / K or at most 1.0 ppb / K.

[0095] However, it is also possible to produce large precision components, i.e. components with a surface diameter or edge length of at least 500 mm. One embodiment of the invention thus relates to components with a large volume. For the purposes of this application, this should be understood to mean a component with a mass of at least 300 kg, preferably at least 400 kg, preferably at least 500 kg, preferably at least 1 1, more preferably at least 21, according to one variant of the invention at least 51, or with edge lengths (width and / or depth) in the case of (rect)angular shapes of at least 0.5 m, more preferably at least 1 m, and / or with a thickness (height) of at least 50 mm, preferably at least 100 mm, preferably at least 200 mm, as a further preference at least 250 mm, or in the case of round shapes with a diameter of at least 0.5 m, more preferably at least 1 m, more preferably at least 1.5 m and / or with a thickness (height) of at least 50 mm, preferably at least 100 mm, preferably at least 200 mm, more preferably at least 250 mm.February 17, 2026

[0096] - 12 -

[0097] Specific embodiments of the invention may also be very large components with, for example, a diameter of at least 3 m or at least 4 m or larger 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 components, wherein preferably at least one surface has an area of at least 1 m2, preferably at least 1.2 m2, more preferably at least 1.4 m2, for some variants more preferably at least 3 m2or at least 4 m2and / or the thickness is 50 mm to 400 mm, preferably 50 mm to 300 mm. As a rule, large-volume components which have a significantly larger base area than height are produced. However, they may also be large-volume components which have a shape approximated to a cube or a sphere.

[0098] Large or very large precision components have a CTE homogeneity of less than 3 ppb / K or at most 2.5 ppb / K or at most 2.0 ppb / K or at most 1.8 ppb / K or at most 1.5 ppb / K.

[0099] Further physical properties

[0100] Advantageous glass-ceramics and precision components additionally have good internal quality. They preferably have at most 5 inclusions per 100 cm3, more preferably at most 3 inclusions per 100 cm3, most preferably at most 1 inclusion per 100 cm3. Inclusions are understood in accordance with the invention to refer both to bubbles and to crystallites having a diameter of more than 0.3 mm.

[0101] According to one variant of the invention, precision components are provided which have a diameter or an edge length of at most 800 mm and a thickness of at most 100 mm and have at most 5, preferably at most 3, more preferably at most 1 inclusion(s), in each case per 100 cm3, having a diameter of a size of more than 0.03 mm.

[0102] As well as the number of inclusions, the maximum diameter of the inclusions detected also serves as a measure of the level of the internal quality. The maximum diameter of individual inclusions within the total volume of a precision component having a diameter of less than 500 mm or edge lengths of less than 500 mm is preferably at most 0.6 mm, in the critical volume for the application, for example close to the surface, preferably at most 0.4 mm. The maximum diameter of individual inclusions in glass-ceramic components having a diameter of 500 mm to less than 2 m or edge lengths of 500 mm to less than 2 m is preferably at most 3 mm, in the volume critical for the application, for example close to the surface, preferably at most 1 mm. This may be advantageous in order to achieve the surface quality needed for the application.February 17, 2026

[0103] - 13 -

[0104] Compositions of green glass and glass ceramic

[0105] The precision component may comprise an LAS-glass ceramic comprising the following composition (in wt.-% based on oxide):

[0106] SiO235 - 72

[0107] Li2O 2 - 6

[0108] at least one component selected from the group consisting of P2Os, R2O, where R2O may be Na2O and / or K2O and / or Cs2O and / or Rb2O, and RO, where RO may be CaO and / or BaO and / or SrO,

[0109] and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2Os, Nb2Os, SnO2, MoOa, WO3.

[0110] The precision component may comprise an LAS-glass ceramic comprising the following composition (in wt.-% based on oxide):

[0111] SiO235 - 72

[0112] Al2o315 - 33

[0113] P2O50 - 12

[0114] Li2O 2 - 6

[0115] Na2O 0 - 2

[0116] K2O 0 - 3

[0117] MgO 0 - 3

[0118] CaO 0 - 4

[0119] BaO 0 - 5

[0120] SrO 0 - 3

[0121] ZnO 0 - 8

[0122] TiO20 - 6

[0123] ZrO20 - 5

[0124] and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2Os, Nb2Os, SnO2, MoOs, WO3.

[0125] In one embodiment, the glass which can be ceramized to form glass ceramic or the glass ceramic comprises the following composition (in wt.-% on an oxide basis):February 17, 2026

[0126] - 14- SiO245 - 72

[0127] AI2O3 15 -33

[0128] P2O5 0- 12

[0129] Li2O 2 -6

[0130] Na2O 0-2

[0131] K2O 0-3

[0132] MgO 0- 3

[0133] CaO 0-4

[0134] BaO 0- 5

[0135] SrO 0- 3

[0136] ZnO 0-5

[0137] TiO20- 6

[0138] ZrO20-5

[0139] and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiO2,ZrO2,Ta2Os, Nb2Os, SnC>2, MoOs, WO3.

[0140] In a further embodiment, the glass which can be ceramized to form glass ceramic or the glass ceramic comprises the following composition (in wt.-% on an oxide basis):

[0141] SiO250 - 70

[0142] AI2O3 17 -32

[0143] P2O5 3- 12

[0144] Li2O 2 - 5

[0145] Na2O 0-2

[0146] K2O 0-2

[0147] MgO 0-2

[0148] CaO 0-4

[0149] BaO 0- 5

[0150] SrO 0-2

[0151] ZnO 0-4

[0152] TiO20- 5

[0153] ZrO20-5

[0154] and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiO2,ZrO2,Ta2Os, Nb20s, SnC>2, MoOs, WO3.February 17, 2026

[0155] - 15 -

[0156] The glass ceramic preferably has a proportion of SiC>2 of 35 to 72 wt.-%. The proportion of SiC>2 is furthermore preferably at most 62 wt.-%, further preferably at most 60 wt.-%. The proportion of SiC>2 is further preferably at least 45 wt.-%, preferably at least 50 wt.-% and further preferably at least 54 wt.-%.

[0157] The proportion of AI2O3 is preferably 15 to 33 wt.-%. The glass ceramic more preferably contains at least 17 wt.-%, preferably at least 20 wt.-%, yet more preferably at least wt.-% AI2O3. The proportion of AI2O3 is more preferably at least 32 wt.-%, more preferably at most 28 wt.-%. The phosphate content P2O5 of the glass ceramic is 0 to 12 wt.-%. The glass ceramic more preferably contains at least 3 wt.-%, more preferably at least 4 wt.-%, yet more preferably at least 5 wt.-%, P2O5. The proportion of P2O5 is preferably restricted to at most 10 wt.-%, more preferably at most 8 wt.-%.

[0158] The glass ceramic preferably also contains TiC>2 in a proportion of 0 to 6 wt.-%, with a preference of at least 1 wt.-%, preferably at least 1.5 wt.-%, TiC>2. The proportion of TiC>2 is, however, preferably restricted to at most 4 wt.-%, more preferably at most 3 wt.-%.

[0159] The glass ceramic can also contain ZrC>2 in a proportion of at most 5 wt.-%, preferably at most 4 wt.-%. ZrC>2 is preferably present in a proportion of at least 0.5 wt.-%, more preferably at least 1 wt.-%.

[0160] The glass ceramic can furthermore contain alkali metal oxides, such as l_i2O, Na2O and K2O. Li2O is preferably present in a proportion of at least 2 wt.-%, preferably at least 3 wt.-%. The proportion of Li2O is preferably restricted to at most 6 wt.-%, more preferably at most 5 wt.-%, more preferably at most 4 wt.-%. Na2O and K2O are optionally present in the glass ceramic. Na2O is preferably present in a proportion of at most 2 wt.-%, preferably at most 1 wt.-%. The proportion of K2O is preferably at most 3 wt.-%, preferably at most 2 wt.-%, most preferably at most 1 wt.-%. Na2O and K2O can in any event and independently of one another be present in a proportion of at least 0.01 wt.-% in the glass ceramic, preferably at least 0.02 wt.-%, more preferably at least 0.05 wt.-%.

[0161] The glass ceramic can also contain alkaline earth metal oxides, such as MgO, CaO, BaO and / or SrO, and further bivalent metals such as ZnO. The proportion of CaO is preferably at most 4 wt.-%, more preferably at most 3 wt.-%, yet more preferably at most 2 wt.-%. The glass ceramic preferably contains at least 0.1 wt.-%, more preferably at least 0.5 wt.-%, CaO. MgO can be present in the glass ceramic in a proportion of at most 3 wt.-%, preferably at most 2 wt.-%,February 17, 2026

[0162] - 16-and / or preferably at least 0.1 wt.-%. The glass ceramic can contain BaO in a proportion of less than 5 wt.-%, preferably at most 4 wt.-%, and / or preferably at least 0.1 wt.-%. In individual embodiments, the glass ceramics are BaO-free. The glass ceramics can contain SrO in a proportion of at most 3 wt.-% and / or preferably at least 0.1 wt.-%. In individual embodiments, the glass ceramics are SrO-free. As a further metal oxide, the glass ceramic preferably contains ZnO in a proportion of preferably at least 1 wt.-%, more preferably at least 1.5 wt.-%. The proportion of ZnO is restricted to at most 8 wt.-%, preferably at most 5 wt.-%, preferably at most 4 wt.-% and preferably at most 4 wt.-%. Some embodiments are free from ZnO.

[0163] For the modulation of the optical properties, e.g. refractive index, for example, Gd2Oa, Y2O3, HfO2, Bi2Oa and / or GeO2 can be contained in some advantageous variants.

[0164] The above glass compositions can optionally contain additions of colouring oxides, such as e.g. Nd20s, Fe2Os, CoO, NiO, V2O5, MnO2, CuO, CeO2, CT2O3, rare earth oxides in contents of in each case individually or in total 0-3 wt.-%. Preferred variants are free from colouring oxides. In some embodiments, the glass ceramic according to the invention comprises from 1.5 wt.-% to 6 wt.-% of at least one component, selected from the group comprising TiO2, ZrO2, Ta2Os, Nb20s, SnO2, MoOs and WO3.

[0165] According to one advantageous embodiment of the present invention, the composition is free from components which are not mentioned above.

[0166] According to one embodiment of the present invention, a transparent glass ceramic is generated. As a result of the transparency, many properties of such a glass ceramic, in particular naturally their inner quality are better influenced. The glass ceramics according to the invention are transparent, i.e. they have a pure transmission of at least 70% in the wavelength range from 350 to 650 nm. B2O3 and / or higher fluoride contents can reduce transparency. Advantageous variants therefore do not contain one or both of the stated components.

[0167] The glass ceramics generated in the context of the invention are furthermore pore-free and crack-free. In the context of the invention, “pore-free” means a porosity of less than 1%, preferably less than 0.5%, more preferably less than 0.1%. A crack is a gap, i.e. a discontinuity, in an otherwise continuous structure.

[0168] Process for producing a precision component - Melting

[0169] A further aspect of the invention relates to a process for producing a precision component comprising the steps ofFebruary 17, 2026

[0170] - 17 - melting a batch of raw materials to form a green glass melt in a melting vessel (6) wherein the melting vessel (6) is heated using two or more heating circuits, each comprising a transformer (3) and at least two electrodes (5), wherein at least one heating circuit comprises an inverter (1) providing an alternating current (AC) to its heating circuit,

[0171] withdrawing the green glass melt from the melting vessel (6),

[0172] forming the green glass melt into a green glass block,

[0173] ceramizing the green glass block to form a glass-ceramic component.

[0174] A specific aspect of the invention relates to a process for producing a precision component comprising the steps of

[0175] melting a batch of raw materials to form a green glass melt in a melting vessel (6), wherein the melting vessel is heated using two or more heating circuits, each comprising a transformer (3) and at least two electrodes (5), wherein at least one heating circuit comprises an inverter (1) providing an alternating current (AC) to its heating circuit and adjusting the amplitude and / or phase angle of this current independently of the amplitudes and / or phase angles of the currents of the other heating circuits and applying a phase angle shift to its current relative to at least one other heating circuit,

[0176] withdrawing the green glass melt from the melting vessel (6),

[0177] forming the green glass melt into a green glass block,

[0178] ceramizing the green glass block to form a glass-ceramic component.

[0179] A state-of-the-art melting vessel utilizable for producing LAS glass ceramics is e.g. described in “Low Thermal Expansion Glass Ceramics”, Hans Bach (editor), Springer-Verlag, 1995, pages 131 -133. Heating of such conventional melting vessels generally is affected via burner flames in the superstructure of the melting vessel. Recently, attempts have been made to replace fossil fuels by hydrogen in melting processes for LAS glass ceramics, see US 2013 / 0081248A. However, since green hydrogen is not yet sufficiently available for glass melting processes, the inventors also indulged in the development of melting vessels and processes that use substantial amounts electrical power in the glass melting of LAS glass ceramics. State-of-the-art processes using electrical power in the glass melting process are not flexible enough for the production of LAS glass ceramics, however, the inventors have found that when using two or more heating circuits, each comprising a transformer and at least two electrodes, wherein at least one heating circuit comprises an inverter, it is possible to flexibly provide heat to a melting vessel and to stably produce LAS glass ceramics. Moreover, the inventors have found that by using such a process, the temperature distribution within the melting vessel can be controlled very precisely and surprisingly, a very homogeneous green glass can be produced that can be ceramized to yield a glass ceramic component with an extremely high homogeneous spatial CTE.February 17, 2026

[0180] - 18 -

[0181] This disclosure relates to methods which allow for the electric heating of a glass melt with multiple heating circuits at least one or some or all of which can be influenced independently of the others in amplitude and / or phase of the current supplied to the electrodes. This allows for the creation of different heating zones in the glass melt by targeted current and power distribution in the glass melt and an optimal current distribution in the glass melt based on desired patterns can be achieved. This flexibility is not fixed by construction measures but can be controlled and adjusted as necessary during the melting process. Thus, an optimal melting of a glass batch in the melting vessel is achieved and the homogeneity of the green glass melt is improved.

[0182] A "melting vessel" is a vessel used for holding a glass melt. A melting vessel may have a superstructure above the glass melt surface. The melting vessel comprises at least two heating circuits.

[0183] A ’’heating circuit” as used herein is meant to comprise a power source and at least two electrodes immersible into the glass melt (and of course the electric lines required for connecting them).

[0184] “Each heating circuit comprising at least two electrodes” means that each heating circuit is electrically connected to at least two electrodes. These electrodes can be electrically connected exclusively to one heating circuit, they can also be electrically connected to one or more other heating circuits, i.e. electrodes can be shared between two or more heating circuits. Hence, the total number of (physical) electrodes in a melting vessel may be less than the sum of the (logical) electrodes in the defined heating circuits in the melting vessel. However, the number of heating circuits in a melting vessel is not particularly limited. Depending on the size of the melting vessel, the melting vessel may comprise at least 2 or at least 3 or at least 6 or at least 8 heating circuits or at least 10 and / or up to 10 or up to 20 circuits.

[0185] One or more or all of the electrodes may be rod-shaped and / or plate-shaped and / or domeshaped and / or tube-shaped and / or block-shaped. One or more or all of the electrodes may be arranged horizontally extending from a wall of the melting vessel or vertically extending from a bottom of the melting vessel or from a surface of the glass melt. In further embodiments, one or more or all of the electrodes may be located partially or completely in or on a wall of the melting vessel and / or in or on the bottom of the melting vessel and / or in the super-structure of the melting vessel (6) and / or constitute a wall section and / or a bottom section and / or a superstructure section of the melting vessel. In further embodiments of the method, the electrode material ofFebruary 17, 2026

[0186] - 19 -one or more or all of the electrodes is selected from Pt, Rh, Ir, Pd, alloys of these noble metals, Ta, Mo, MoSi2, MoZrCh, W, SnC>2, C, and combinations thereof.

[0187] The electrodes may be operated at a current frequency of at least 20 Hz and at most 25,000 Hz, optionally of at least 50 Hz and at most 25,000 Hz, optionally of at least 50 Hz and at most 15,000 Hz, optionally of at least 50 Hz and at most 10,000 Hz, optionally of at least 100 Hz and at most 10,000 Hz, optionally of at least 1,000 Hz and at most 5,000 Hz, optionally of at least 1 ,000 Hz and at most 3,000 Hz. The electrodes may be operated at a current frequency of less than 25,000 Hz, less than 15,000 Hz, less than 12,500 Hz, less than 10,000 Hz, less than 7,500 Hz, less than 5,000 Hz, less than 4,500 Hz, less than 4,000 Hz, less than 3,500 Hz, or less than 3,000 Hz. The electrode may be operated at a current frequency of at least 20 Hz, at least 50 Hz, at least 100 Hz, at least 1,000 Hz, at least 1,500 Hz, at least 2,000 Hz, or at least 2,500 Hz.

[0188] In further embodiments, additional heating is provided by a fuel burner, or no fuel burner is used for additional heating. This burner may then be fueled by a "green gas", i.e. hydrogen produced from renewable energies.

[0189] As a power source for the heating circuit the heating circuit may comprise a transformer or an inverter as a power source.

[0190] A “transformer” is a power electronic component that regulates the power by transferring electrical energy from one electrical circuit to another circuit thereby allowing for a change of the power and / or voltage supplied within e.g. the grid frequency to a heating circuit and may e.g. be a thyristor power controller or a regulating transformer or any other suitable power electronic components.

[0191] A ’’thyristor controller” or “thyristor power controller” controls the power and / or voltage supplied within the grid frequency to a heating circuit.

[0192] A “matching transformer” is used to match current and voltage of a heating circuit to the conductivity of the glass melt and is typically positioned close to the electrodes of a heating circuit. In addition, a matching transformer provides galvanic isolation of the heating circuits. A matching transformer can be provided in each heating circuit in addition to a power electronic component such as an inverter, regulating transformer or thyristor power controller.February 17, 2026

[0193] - 20 - “Power grid frequency” or utility frequency or power line frequency or mains frequency is the nominal frequency of the oscillations of alternating current (AC) in a wide area synchronous grid transmitted from a power station to the end-user. Typically, the power grid frequency is 50 Hz or 60 Hz.

[0194] According to one embodiment, at least one heating circuit comprises an inverter. An “inverter” or “frequency changer” is a power electronic component which converts one alternating current of one frequency and / or phase to an alternating current of another frequency and / or phase, in particular an alternating current the frequency and / or phase of which is different from the frequency and / or phase of the grid. For example, an inverter may comprise of (a) a rectifier transforming alternating current (AC) into DC, followed by (b) an intermediate circuit e.g. comprising a capacitor and (c) an inverted rectifier transforming DC into an alternating current. Using such an inverter enables to convert a given AC (e.g. the power grid frequency) into an alternating current with any desired frequency and / or phase.

[0195] Not all heating circuits have to comprise an inverter which are comparatively expensive components. In particular, if the operating current frequency is not changed from the grid frequency, it is advantageous from an economical point of view to realize the power supply of at least one heating circuit by using e.g. a thyristor power controller and / or a regulating transformer. Such heating circuits without inverters can particularly be used in parts of the melting vessel where specifically tailored heat distribution profiles in the glass melt are not essential and / or the available frequencies from the primary transformers are sufficient and a phase angle shift for these heating circuits is not required. Heating circuits in parts of the melting vessel in which specific heat distribution profiles are essential are preferably equipped with inverters and thus the phase angle adjustment possibility of this invention in order to optimize the flow pattern and / or dwell time of the glass melt as described above.

[0196] The feature of "controlling the amplitude and / or phase of a current independently of the amplitudes and / or phase angles of the currents of other heating circuits" means that the one or more inverters can provide currents of different amplitudes and / or phase angles, i.e. the amplitude and / or phase angle of the current provided by one inverter is not affecting the amplitudes and / or phase angles of currents provided by other inverters in other heating circuits. It does not exclude that two or more inverters operate at different amplitudes and / or phase angles in a predetermined relationship, e.g. controlled by a common controller.

[0197] “Phase angle of the supplied current” encompasses also phase angle of the supplied voltage or power. Due to the relationship P = U * I, instead of the phase angle of the current I as well theFebruary 17, 2026

[0198] - 21 -phase of the power P or the phase of the voltage II can be controlled. The phases of II and I in a certain heating circuit at the electrodes are preferably in phase.

[0199] The “phase” or “phase angle” or “phase shift” or “phase angle shift” of an electrical circuit is a measure of the relative timing between two sinusoidal waveforms. It represents the delay or lead of one waveform to another. A phase angle is measured in degrees or radians and can be positive or negative, indicating whether one waveform leads or lags the other. The phase angle <p can also be expressed as a time delay At or “phase shift” according to the following formular

[0200] phase angle cp = (time delay At I period T) X 360° = (time delay At x frequency) x 360°.

[0201] In the context of electrical circuits, the expression “phase” or “phase angle” often used to describe the relationship between voltage and current in one AC (alternating current) circuit. If not otherwise specified, according to the present invention, “phase” or “phase angle” or “phase shift” or “phase angle shift” is defined as the phase difference of one specific physical quantity in one heating circuit (measured preferably near the electrodes of the heating circuit) relative to the same physical quantity in one or more other heating circuits, e.g. the phase angle of the current in one heating circuit is compared to the phase angle of the current in the other heating circuits and the difference is defined as the phase shift or phase angle or delay.

[0202] A “common controller” as used herein takes on several tasks and / or functions. First of all, the common controller collects some or all measurement data that are generated in some or preferably all heating circuits and optionally other parts of the melting vessel. Secondly, the common controller utilizes the collected measurement data to compare the actual values to the stored or set target values and sends out control signals to the control units such as e.g. thyristor power controllers, inverters and / or delay generators.

[0203] The common controller furthermore comprises or is connected to a clock generator or global clock generating a global clock signal. The global clock acts as a frequency control unit which provides an external time base for all inverters. It is used to provide a global clock signal to the delay generators providing an individual shift of the phase angle of the current provided by each inverter. In the case of one or more heating circuits using power grid frequency and phase, the global clock is synchronized to the power grid frequency and phase. “A heating circuit using power grid frequency and phase” means that such heating circuit does not comprise a rectification device such as e.g. an inverter.February 17, 2026

[0204] - 22 - All tasks and / or functions of the common controller can be concentrated in a single central common controller device; it is also possible that certain tasks and / or functions of the common controller are handled decentrally by further controllers or specialized devices such as e.g. a delay generator. One or more controlling tasks and / or functions of the common controller can also be executed by qualified workers.

[0205] According to a further embodiment, the present invention can also be used for phase angle correction of the current in one heating circuit relative to the phase of the voltage within the same heating circuit. As the phase angle of the voltage may shift relative to the phase angle of the current along the path from the inverter to the electrodes, a correction of this phase shift of the voltage relative from the phase of the current is particularly advantageous in two aspects. A detector which is installed at the electrodes can detect and measure the phase angle shift of the voltage relative to the current. Since the present method and apparatus allow for the free adjustment of the phase angle of the current, this detected shift can be corrected. To assure the maximum power at the electrodes, the phases of current and voltage of a heating circuit should be in phase. Thus, the detection of the phase angle between the phases of current and voltage allows for a correct assessment of the actual heating power distribution in the glass melt and optimized power in the melt. Such a correction is useful in a first aspect for the correct establishment of the intended heating profile and hotspot creation for influencing the flow pattern of the glass melt. In a second aspect, this can also be an important factor for minimizing the occurrence of parasitic currents and the power loss associated with them in a melting vessel which is operated with parallel heating circuits having a phase angle difference of 0° like the standard heating circuits used in prior art. This way, electrical efficiency may be improved when operating at higher frequencies and, consequently, either energy can be saved, or the operation frequency may be increased for lowering the electro corrosion further.

[0206] The common controller is preferably also connected to one or more heating circuits without inverters, can thus detect the phase angle of such heating circuits and can generate a clock signal relative to these heating circuits. The delay generators of the heating circuits with inverters can thus provide a shift of the phase angle of the current by applying a delay At > 0 ps to the clock signal of the common controller (8).

[0207] For example, the delay At applied by one the inverters to its heating circuit relative to a second heating circuit may differ by 0.1 ps (At2 = Ah + 0.1 ps) while the further heating circuits have the same or a different or no delay applied, i.e. At = Ah or At2, At Ah or At2, or At = 0 ps, respectively. As a result, between at least two heating circuits a certain shift in current phase angle willFebruary 17, 2026

[0208] - 23 -occur while the other heating circuits may have the same relative shift or a different one. According to one embodiment, one or more or all At > 0 ps.

[0209] The feature of "independently applying a delay At" means that the various inverters can be operated with different time delays applied to the clock signal, i.e. the inverters work with differently timewise modified clock signals by keeping the frequency constant resulting in a different phase angle of the supplied current. It does neither exclude that two or more inverters operate with different timewise modified clock signals in a predetermined relationship nor that two or more inverters operate with identically timewise modified clock signals.

[0210] In embodiments, the phase angle shift between the heating circuits with inverters is freely adjustable in a range of 0° to 360° relative to other heating circuits.

[0211] In embodiments, in one or more or all of the heating circuits a phase detector may be installed between the transformers and the electrodes which measures the actual current signal at the electrodes and the common controller detects a phase angle shift by comparing this actual current signal with the clock signal provided to the inverters including any applied delay At and adjusts the clock signal and / or the delay At in order to compensate for an undesired shift along the current flow from the inverter to the electrodes.

[0212] Electrotechnically, the glass melting system of the present disclosure can be seen as a complex meshed network. Each inverter can initially feed into the glass melt with different power, current, voltage, and phase. Due to a typical resistivity of the glass melt in a range of from 0,3 Q cm to 200 Q cm at a temperature of 1,600 °C, the inverters as sources of power are not independent from each other but electrically coupled via the glass melt. A change in a parameter at one inverter may cause a change in all other inverters being part of the same network. All heating circuits are to be operated with the same frequency in the range of from 20 Hz to 25,000 Hz and to have a defined phase relative to each other. These two conditions are achieved by a clock generator in a common controller which provides an external time base for all inverters connected to that common controller.

[0213] In a first mode of operation, where At = 0 for all heating circuits, all inverters have no phase angle shift relative to each other since all oscillations and / or sinusoidal or other periodical currents start at a certain point in time t = 0, which is defined by the common controller. In a second mode of operation, where a shift in the phase angle of a certain inverter is desired, a respective delay At in the clock signal supplied to this inverter will be applied. This can be done individually and independently from each other for all inverters. The delay in the trigger signals may beFebruary 17, 2026

[0214] - 24-implemented either by means of separate delay generators installed between the common controller (i.e. decentrally) and the respective inverters or by delay generators integrated within the common controller (i.e. centrally). With the delay set to zero, the system works like in the first mode of operation.

[0215] Using a phase detector which is installed at or in proximity of the electrode, it is possible to measure the actual signal curve of the current at the electrode and compare it to the signal of the clock generator in the common controller (including any applied delay At) for determining the phase angle shift of each electrode or heating circuit, respectively. This information can be used for varying the applied delay time At to precisely set a desired phase angle shift at an electrode or to readjust the electrode to be in phase with the others if no shift in phase angle is intended.

[0216] In embodiments of the method, the common controller may synchronize its clock signal with an external clock signal e.g. the phase of the power grid. The global clock e.g. within the common controller may synchronize to the external clock signal which is equivalent to a frequency by detecting the zero crossings of the external frequency signal and adjusting its own zero crossings of the clock signal with them. The frequencies may in this case be identical, but they do not have to be identical. In the latter case, the zero crossings of the lower frequency first signal may be matched with the nthzero crossing of the higher frequency second signal wherein n is dependent on the frequency difference. Such an external clock signal synchronization may be advantageous for adapting to the continuously slightly changing power grid frequency of neighboring components in a melting facility which is operated at the power grid frequency of 50 / 60 Hz.

[0217] The signal lines of the apparatus may be a direct or indirect connection by wire or wireless technique.

[0218] According to further embodiments, desired thermal zones are created within the glass melt in the melting vessel (6) by setting the amplitude and / or the phase of the current of each individual heating circuit. Heating circuits in parts of the melting vessel in which specific heat distribution profiles are essential are preferably equipped with inverters and thus the phase angle adjustment possibility of this invention in order to optimize the flow pattern and / or dwell time of the glass melt as described above.

[0219] The above-described process adds to the flexibility of a continuous melting process, where each phase of the glass melting process has a dedicated part of the furnace with individually optimized heating geometries. However, changes in glass types, glass composition,February 17, 2026

[0220] - 25 -glass flow rates can require flexible adjustments to the distribution of the electrical heating power, which is ensured by the described method.

[0221] In a discontinuous melting process, the fixed geometry of the heating circuits strongly limits the ability to adjust the local distribution of the electrical heating power to the different melting phases. The method described is particularly suitable to adapt the heat distribution in the melting vessel to the different melting phases, in particular, the melting down phase, the fining phase and the conditioning phase. E.g. during the melting down phase, defined hot spots in the melt can be created by adjusting heat distribution. During the fining phase, a different heat distribution can flexibly be created by the described method in order to optimize the bubble release from the glass melt and an effective glass flow can be created within the melt to optimize the homogenization of the melt. Finally, during the conditioning phase a homogeneous heat distribution in the melt can be set to effectively condition the homogenized melt before the casting phase. For example, convective currents can be counter-acted by a dedicated heat power distribution.

[0222] In further embodiments, the current density used at one or more or all of the electrodes is 0.2 A / cm2- 2.0 A / cm2. This range provides good balance between power input into the melt and corrosion as well as a possible reduction of the number of electrodes. The current density may be 0.2 A / cm2- 2.0 A / cm2or 0.3 A / cm2- 1.8 A / cm2or 0.4 A / cm2- 1.65 A / cm2or 0.5 A / cm2-1.5 A / cm2. The current density may be at least 0.2 A / cm2or at least 0.3 A / cm2or at least 0.4 A / cm2or at least 0.5 A / cm2. The current density may be at most 2.0 A / cm2or at most 1.8 A / cm2or at most 1.65 A / cm2or at most 1.5 A / cm2.

[0223] Figure 1 schematically shows a melting vessel comprising three heating circuits whereas two heating circuits comprise inverters. In Figure 1, the three conductors (Li, L2, L3) of a three-phase power line provided from the power grid are shown which are connected to three heating circuits either comprising an inverter (1) or a thyristor power controller (11) for varying the power output from 0 % to 100 %. The inverters (1) are connected via a power factor correction (2) for keeping the phase difference between current and voltage minimal and a matching transformer (3) to the electrodes (5). The thyristor power controller (11) is connected via a matching transformer (3) to electrodes (5). The matching transformer (3) also serves for galvanic isolation of the heating circuits.

[0224] The heating circuit without inverter uses the phase of the power grid. Besides varying the power output, the inverters (1) can furthermore impose a phase shift to their heating circuits relative to the other heating circuits. The inverters (1) are connected via a power factor correction (2) forFebruary 17, 2026

[0225] - 26 -keeping the phase difference between current and voltage minimal and a matching transformer (3) to the electrodes (5). According to this embodiment, the power grid frequency of 50 or 60 Hz is preferably used.

[0226] In other embodiments, in which all heating circuits comprise inverters, the inverters can furthermore convert the power grid frequency of 50 / 60 Hz to a medium range frequency of from 20 Hz to 25,000 Hz.

[0227] In the melting vessel (6) which is shown in a top view, three pairs of electrodes (5) are arranged extending horizontally from the wall. As indicated in the figure, in this example, the three heating circuits formed by the three pairs of electrodes (5) are shifted in their phase angle of the current by Aq>i and Aq , respectively. In each heating circuit, in the electrical lines connecting the matching transformers (3) with the electrodes (5) a phase detector (10) is installed in close proximity to one of the electrodes (5). These three phase detectors (10) measure the actual current signal at the electrodes (5) and provide this information via the further signal lines (7) to the common controller (8). The common controller (8) is connected to the global clock and acts as a clock generator generating a clock signal for the two heating circuits comprising inverters (1) in a defined phase angle to the heating circuit with the thyristor power controller (11). The two delay generators (9) installed in the signal lines (7) between the common controller (8) and the inverters (1) provide a shift of the phase angle of the current provided by them to the heating circuits by independently applying an individual delay Ah and At2to the trigger signal for its associated inverter (1).

[0228] Process for producing a precision component - Ceramization

[0229] The above-described process for producing a green glass block of a glass ceramic is essential to provide for a homogeneous distribution of the various chemical compounds in a glass ceramic component. However, it is also advisable to carefully control the ceramization conditions so that ceramization, meaning nucleation and growth of crystals in the glass matrix of the glass ceramic happen as controlled and as homogeneously as possible in the complete volume of the glass ceramic component. The inventors have found that the below described method improves the absolute mean CTE of the glass-ceramic component as well as the spatial CTE homogeneity.

[0230] It is known that during the transformation of a green glass to a glass-ceramic an exothermic reaction takes place, in particular the transformation of the matrix glass to a high quartz solid solution (HQSS). This effect is easily detectable in samples in measurement devices, however, during ceramization in particular during ceramization of larger glass ceramic blocks it was notFebruary 17, 2026

[0231] - 27 -possible until now to use this information to improve the ceramization process in actual production of glass-ceramic components.

[0232] The inventors have thoroughly investigated the ceramization process and found that the following method yields precision components with improved thermal expansion properties. In particular, it is necessary to determine a characteristic temperature for each set of green glass blocks and to use this characteristic temperature to control the ceramization program in a way that glass-ceramic components with improved thermal expansion properties can be achieved.

[0233] The inventors have found that the size and the shape of the green glass components influence said characteristic temperature. This is particularly the case for lager green glass blocks e.g. blocks having a weight of more than 100 kg or 200 kg or 500 kg.

[0234] Surprisingly, it was furthermore found that even very small compositional variations in the green glass influence the exothermic peak of the ceramization and thus the characteristic temperature. Very small variations of the composition can e.g. be found in different production batches or even, if the melt in a batch is not sufficiently homogenized. The above-described improved melting process yielding a very homogeneous green glass melt and green glass blocks was therefore also important for the further development of the ceramization process.

[0235] The invention therefore further relates to a method of ceramizing a green glass component into a glass ceramic, comprising the steps:

[0236] providing a set of green glass blocks,

[0237] determining the characteristic temperature for ceramizing a first green glass block of said set of green glass blocks to a glass-ceramic, whereas said characteristic temperature is determined by measuring the temperature on the glass block and the oven temperature and determining the difference of these temperatures,

[0238] applying the so determined characteristic temperature to (a) control the oven temperature and / or (b) the holding time during the ceramization of further blocks of the set of green glass blocks.

[0239] A “set of green glass blocks” means that all green glass blocks have the same or approximately the same shape and size and that all green glass blocks originate from the same highly homogeneous melting batch.

[0240] In this context green, glass blocks “having the same size” means green glass blocks the weight of which differs at most 5 % or at most 3 % or at most 1 % and / or “having the same shape”February 17, 2026

[0241] - 28 -means green glass blocks either (a) the diameter and height of a round green glass block differ by at most 5 % or at most 3 % or at most 1 % or (b) the edge lengths of a cubic or cuboid green glass blocks differ by at most 5 % or at most 3 % or at most 1 %.

[0242] Green glass blocks “originating from the same highly homogenized melting batch” means in case of a discontinuous melting process that all blocks originate from the same melting batch and having the same chemical composition e.g. compositional fluctuations of one or more or all components in a melt should be less than 0.5 wt.-% or less than 0.1 wt.-% or less than 0.05 wt.%. According to specific embodiments, “originating from the same melting batch” can also mean, originating from certain sections of the same melting batch, e.g. blocks cast during the first half of the melting batch or during the second half of the melting batch or during an otherwise specifically defined part of the melting batch.

[0243] At least one thermometer with an accuracy of at least ±1 Kelvin is placed on the surface of the green glass block to be ceramized. In particular, in case of large or very large green glass blocks, it is advantageous to use more than one thermometer, e.g. 2 or 4 or 6 or even more thermometers.

[0244] At least one further thermometer with an accuracy of at least ±1 Kelvin is placed in the oven to measure the oven temperature. More than one, e.g. 2 or 4 or 6 or even more thermometers, can be used to measure the oven’s temperature.

[0245] The difference between the thermometers on the surface of the green glass block and the thermometers in the oven atmosphere is closely monitored. During the phase transition, the difference between temperature on the blank and the oven temperature has a peak-like shape, and the characteristic temperature can be determined from this peak-like shape. According to one embodiment, a master peak shape can be fitted to the measurement of the thermometer.

[0246] When a characteristic temperature for a set of green glass blocks has been determined, this characteristic temperature is assigned to the standard ceramization program. Then this adapted ceramization program is used together with the measured blank temperature during ceramization to control the ceramization program of the further blocks from the set of green glass blocks. In particular, when detecting a deviation of the blank temperature from the calculated ceramiz-ing program for the set of green glass blocks, it is possible to control and adapt (a) the oven temperature and / or (b) the holding time during the ceramization of such further block of the set of green glass blocks and thus compensating the deviation of the ceramization program and / or the small deviation in chemical composition.February 17, 2026

[0247] - 29 -

[0248] The determination of the characteristic temperature and / or the controlling of the oven temperature and / or holding time using the characteristic temperature can be supported by artificial intelligence and / or machine learning programs in particular for compensation of noise.

[0249] Although determining the characteristic temperature for each set of green glass blocks seems meticulous, it nevertheless is of great advantage in mass production of high precision components. The above-mentioned improved ceramization process not only serves to improve the homogeneity of the thermal expansion properties, it also assures that e.g. the zero-crossing temperature can be set with high accuracy within the set of produced glass-ceramic blocks.

[0250] Use of the precision component

[0251] The invention also relates to the use of a precision component.

[0252] The precision component can advantageously be used in metrology, lithography, spectroscopy, astronomy, earth observation from space, for example as mirrors or mirror substrates for segmented or monolithic astronomical telescopes or as lightweight or (ultra)light mirror substrates for space-based telescopes, measurement technology, for example, as high-precision structural components for distance measurement, e.g. in space or optics for earth observation, as mirrors and prisms in LCD lithography, microlithography and / or EUV lithography, for example, as mask holders, wafer stages, reference plates, reference frames and grating plates in microlithography or additionally, mirrors or mask blanks in EUV lithography, or as mirrors or mirror substrates for range finders, directed energy weapons (DEW), laser fusion or particle accelerators. Another possible application is thermal insulation for cryogenic storage and transportation of liquid hydrogen or other liquid gases.

[0253] Precision components can be, for example, optical components, more specifically a "normal incidence mirror", i.e. a mirror which is operated close to the vertical incidence of radiation, or a "grazing incidence mirror", i.e. a mirror which is operated with a grazing incidence of radiation. In addition to the substrate, such a mirror comprises a coating which reflects the incident radiation. Particularly in the case of a mirror for X-rays, the reflective coating is, for example, a multilayer system or multilayer having a multiplicity of layers with a high reflectivity in the X-ray range in the case of non-grazing incidence. Such a multilayer system of a normal incidence mirror preferably comprises 40 to 200 layer pairs, consisting of alternating layers, for example one of the material pairs Mo / Si, Mo / Bi, Ru / Si and / or MoRu / Be.February 17, 2026

[0254] - 30 - In particular, the optical elements according to the invention can be X-ray optical elements, i.e. optical elements which are used in conjunction with X-rays, in particular soft X-rays or EUV radiation, in particular reticle masks or photomasks operated in reflection, in particular for EUV microlithography. They can advantageously be mask blanks. Furthermore, the precision component can advantageously be used as a mirror or as a substrate for a mirror for EUV lithography.

[0255] Furthermore, the precision component according to the invention can be a component, in particular a mirror for astronomical applications. Such components can be used for astronomical applications both terrestrially and in space. High-precision structural components for distance measurements, for example in space, are another advantageous field of application.

[0256] The precision component according to the invention can be a lightweight structure. The component according to the invention can furthermore comprise a lightweight structure. This means that, in some regions of the component, cavities are provided for weight reduction. Lightweight machining is preferably used to reduce the weight of a component by at least 80%, more preferably at least 90%, in comparison with the unmachined component.

[0257] Examples

[0258] Compositions as described in Table 1 were melted and cast into green glass blanks according to the process as described in WO 2015 / 124710, however, using an electrically heated furnace as shown in Figure 1. The green glass blanks were ceramized using the novel ceramization process as outlined above.

[0259] Comparative Examples 1 to 3 were melted and cast into green glass blanks according to the process as described in WO 2015 / 124710. The resulting blanks were ceramized using a state-of-the-art ceramization processes.February 17, 2026

[0260] - 31 - Table 1: Compositions (in wt.-%)

[0261]

[0262] Table 2: Precision components (Examples)

[0263]

[0264] February 17, 2026

[0265] - 32 - Table 3: Precision components (Comparative Examples)

[0266]

[0267] In the Tables:

[0268] CTE(0;50) [ppb / K] is mean / average CTE(0;50)

[0269] - CTE(19;25) [ppb / K] is mean / average CTE(19;25)

[0270] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and / or operating conditions of this invention for those used in the preceding examples.

[0271] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.February 17, 2026

[0272] - 33 - Reference numerals

[0273] 1 frequency changer (inverter)

[0274] 2 power factor correction

[0275] 3 matching transformer

[0276] 4 surface of the glass melt

[0277] 5 electrode

[0278] 6 melting vessel

[0279] 7 signal line

[0280] 8 common controller

[0281] 9 delay generator

[0282] 10 phase detector

[0283] 11 thyristor power controller

[0284] 12 global clock

[0285] Li, l_2, 1—3 conductors of a 3-phase power line

[0286] 40 Precision component

[0287] 42 Green glass block

[0288] 44 Test samples

Claims

Applicant: SCHOTT AG February 17, 2026 Our File: P06322 WOOfficial File No:- 34 -Claims1. Precision component, comprising a linear coefficient of thermal expansion CTE(0;50) of at most 0 ± 20 ppb / K or at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K, and a CTE(0;50) spatial homogeneity of- at most 1 ,8 ppb / K for components with a surface diameter or edge length of less than to 500 mm, or- less than 3 ppb / K for components with a surface diameter or edge length of at least 500 mm.

2. Precision component according to claim 1 , having at least one zero crossing of the CTE(T)- T curve within the temperature range of from 0°C to 100°C or within the temperature range from 10°C to 50°C, and / or a slope at the zero crossing of the CTE(T)-T curve of at most 2.0 ppb / K2or at most 1.0 ppb / K2.

3. Precision component to any of the preceding claims, comprising a zero crossing of the CTE(T)-T curve at 22°C + / - 1 and / or a slope of the CTE(T)-T curve at zero crossing of at most 0.5 ppb / K2.

4. Precision component to any of the preceding claims, comprising a linear coefficient of thermal expansion CTE(19;25) of at most 0 ± 20 ppb / K or at most 0 ± 10 ppb / K, and / or a spatial CTE(19;25) homogeneity of at most 2 ppb / K.

5. Precision component to any of the preceding claims, comprising a CTE-T plateau in the temperature range of from 0°C to 100° having a width of at least 10 K or at least 20 K, and having a CTE of at most 0 ± 20 ppb / K or at most 0 ± 5 ppb / K or at most 0 ± 2 ppb / K and / or having a maximum slope of the CTE-T curve of at most 1.0 ppb / K2.

6. Precision component to any of the preceding claims, wherein the height h of the precision component is at most 1 / 3 of the diameter D in case of round precision components and at most 1 / 3 of the edge length of a cuboid precision component.February 17, 2026- 35 - 7. Precision component according to any of the preceding claims, wherein the component comprises an LAS-glass ceramic comprising the following composition (in wt.-% based on oxide)SiO235 - 72AI2O315 - 33P2O50 - 12Li2O 2 -6Na2O 0 -2K2O 0 - 3MgO 0 - 3CaO 0 -4BaO 0 - 5SrO 0 - 3ZnO 0 - 8TiO20 -6ZrO20 - 5and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of Ti O2, ZrC>2, T a2Os, Nb20s, SnO2, MoOa, WO3.

8. Method of manufacturing precision components according to any of claims 1 to 7 comprising the steps of- melting a batch of raw materials to form a green glass melt in a melting vessel (6) wherein the melting vessel (6) is heated using two or more heating circuits, each comprising a transformer (3) and at least two electrodes (5), wherein at least one heating circuit comprises an inverter (1) providing an alternating current (AC) to its heating circuit, - withdrawing the green glass melt from the melting vessel (6),- forming the green glass melt into a green glass,- ceramizing the green glass to a glass-ceramic.

9. Method according to claim 8, wherein in at least one heating circuit comprising an inverter providing a current to its heating circuit, the amplitude and / or the phase angle of this current independently of the amplitudes and / or phase angles of the currents of the other heating circuits adjusted and a phase angle shift to its current relative to at least one other heating circuit is applied.February 17, 2026- 36 - 10. Method according to claim 8 or 9, wherein desired thermal zones are created within the glass melt in the melting vessel (6) by setting the amplitude and / or the phase of the current of each individual heating circuit.

11. Method according to any one of claims 8 to10, wherein the electrodes (5) are operated at a current frequency of at least 20 Hz and at most 25,000 Hz, optionally of at least 50 Hz and at most 25,000 Hz, optionally of at least 50 Hz and at most 15,000 Hz, optionally of at least 100 Hz and at most 12,000 Hz, optionally of at least 1,000 Hz and at most 10,000 Hz, optionally of at least 1 ,000 Hz and at most 5,000 Hz.

12. Method according to any one of claims 8 to 11, wherein in one or more or all of the heating circuits a phase detector (10) is installed between the transformers (3) and the electrodes (5) which measures the actual current signal at the electrodes (5) and a common controller (8) detects a phase angle shift by comparing this actual current signal with the clock signal provided to the inverters (1) including any applied delay At and adjusts the clock signal and / or the delay At in order to compensate for an undesired shift along the current flow from the inverter (1) to the electrodes (5).

13. Use of a precision component according to any of claims 1 to 7, in metrology, spectroscopy, measurement technology, lithography, astronomy or Earth observation from space, for example as mirror or mirror carrier for segmented or monolithic astronomical telescopes or else as weight-reduced or ultra-light mirror substrates for, for example, space-based telescopes or as high-precision structure components for measurement of distance, for example in space, or optics for Earth observation, as precision components, such as standards for precision measurement technology, precision rules, reference plates in interferometers, as mechanical precision parts, for example for ring laser gyroscopes, spiral springs for the clock industry, as for example mirrors and prisms in LCD lithography, and for example as mask holders, wafer stages, reference plates, reference frames and grid plates in microlithography and in EUV microlithography, and as mirrors and / or photomask substrates, photomask carriers or reticle mask blanks in EUV microlithography.

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