Glass ring made of multi-component glass, and method and device for producing said glass ring

Abstract

It is an object of the invention to produce near-net geometry rings, in particular thick-walled rings having a wall thickness greater than 10 mm, from multi-component glass. To this end, an annular blank is first produced from the multi-component glass using a casting process, in which a strand made of a glass melt of the multi-component glass is fed into a casting mold having an annular casting cavity extending about a central axis. The strand impinging on the impingement zone branches off into a right side sub-stream and a left side sub-stream, wherein the sub-streams merge at a merging zone in the casting cavity and fill the casting cavity over at least a portion of the height of the casting cavity. After the cooling of the glass melt, an annular blank is obtained, which is further processed into a glass ring made of the multi-component glass.

Description

Background Technology

[0001] The present invention relates to a method for producing glass rings from multi-component glass, particularly a method for producing large, preferably thick-walled, glass rings.

[0002] Furthermore, the present invention relates to an apparatus for producing glass rings from multi-component glass.

[0003] The present invention also relates to a glass ring made of multi-component glass.

[0004] For example, in semiconductor manufacturing, such glass rings are used as so-called "plasma etching rings" to hold semiconductor wafers in a plasma etching system.

[0005] Plasma-assisted manufacturing processes (such as plasma-assisted dry etching, also simply referred to as "plasma etching") are techniques used to produce ultra-fine structures for semiconductor components, high-resolution displays, and solar cells. Plasma etching is performed in a plasma chamber that is flushed with etching gases at low pressure, where reactive etching plasma is generated. For etching silicon-based structures, halogen-containing etching gases such as CF4, C2F6, C3F8, C4F6, CH2F2, C4F8, NF3, SF6, HF, HCl, or HBr are typically used. The components in the plasma chamber are periodically cleaned, which is also usually accomplished using plasma and fluorinated etching gases. Existing technology

[0006] Rings exposed to plasma and etching gases are typically made of quartz glass and are also known as etched rings. To produce etched rings, according to EP 3 656 746 A1, an intermediate product in the form of a hollow cylinder made of synthetically produced quartz glass is manufactured, from which the etched ring is then cut.

[0007] Synthetically produced quartz glass is characterized by high purity, UV transparency, chemical resistance to many substances used in the manufacturing process, and high-temperature resistance. However, in the presence of halogen-containing, especially fluorine-containing etching gases, quartz glass is eroded by plasma, and due to this erosion, the surface roughness of the quartz glass increases, and particle formation increases during the manufacturing process.

[0008] It is known that multicomponent glasses containing various other components besides SiO2, particularly rare earth metal compounds, can exhibit improved dry etching resistance. For example, US 6,887,576 B2 proposes improving the dry etching resistance of quartz glass by doping with elements capable of reacting with fluorine to form fluorides with boiling points higher than SiF4. Examples of such elements are: Al, Sm, Eu, Yb, Pm, Pr, Nd, Ce, Tb, Gd, Ba, Mg, Y, Tm, Dy, Ho, Er, Cd, Co, Cr, Cs, Zr, In, Cu, Fe, Bi, Ga, and Ti.

[0009] US Patent 2014 / 0274653 A1 discloses multi-component glasses containing rare-earth oxides and yttrium oxide, characterized by their superior resistance to plasma erosion compared to quartz glass. The specific chemical compositions of these plasma-resistant multi-component glasses are as follows:

[0010] Yttrium oxide (Y2O3): 5% to 40% by weight

[0011] Alumina (Al2O3) 5% to 30% by weight

[0012] Silicon dioxide (SiO2): 10% to 80% by weight

[0013] Magnesium oxide (MgO) 1% to 20% by weight.

[0014] Technical goals

[0015] Multicomponent glasses are typically produced by melting powdered raw materials, and due to manufacturing-related reasons, their purity is lower than that of glasses "synthesized," for example, by precipitating glass-forming components from the gas phase. Specifically, depending on the purity of the raw materials used, multicomponent glasses may contain impurities that are harmful to semiconductor manufacturing.

[0016] Plasma-resistant multicomponent glasses containing rare-earth oxides, as well as other specialty glasses, typically exhibit a strong tendency to crystallize. However, during plasma dry etching processes, crystals, pores, and other inhomogeneities within the glass lead to grain formation. To avoid crystallization, for example, for the production of plasma-resistant multicomponent glass components as described in US 2014 / 0274653 A1, it is recommended to melt a mixture of starting components and then quench the melt, or to first melt the multicomponent glass, pulverize it into powder, and sinter the powder at a temperature below the glass melting temperature.

[0017] However, glass is generally a poor conductor of heat, so it is only possible to quench it rapidly from high temperatures without crystallization at very small wall thicknesses. This makes it difficult to produce thick-walled rings with a wall thickness of 10 mm or more in this way. When glass powder is sintered at temperatures below its melting point, residual porosity remains in the sintered bulk, making it impossible to obtain transparent and porosity-free multicomponent glass. Furthermore, due to the high specific surface area of ​​glass powder, crystallization at elevated temperatures is a particularly critical effect.

[0018] The present invention is specifically based on the following objective: to specify a method that enables the production of near-net-shape rings from multicomponent glass, even in the case of thick-walled rings with a wall thickness greater than 10 mm.

[0019] Alternatively or additionally, the present invention is based on the objective of providing a casting method for glass rings that allows for sufficiently high cooling rates while minimizing associated crystal formation, and, in the best case, no crystal formation even in the case of thick-walled glass rings with a wall thickness greater than 10 mm.

[0020] Furthermore, the present invention aims to provide an apparatus for performing the method.

[0021] Furthermore, the object of the present invention is to provide a thick-walled ring made of multi-component glass and substantially free of defects such as bubbles, inclusions and crystals. Detailed Implementation

[0022] Regarding this method, this objective is achieved by a method having the features described in claim 1.

[0023] This method is used to produce glass rings from multi-component glass containing rare earth oxides by casting a glass melt of multi-component glass in a mold.

[0024] In a melting unit, such as a glass melting bath or crucible, glass melts are produced from multicomponent glasses. Glasses that tend to crystallize (such as the multicomponent glasses relevant here) must be heated to sufficiently high melting temperatures to obtain a homogeneous melt, molten crystals, and / or to avoid nucleation within the glass melt. Melting temperatures typically result in low viscosity glass melts, which fundamentally makes them more difficult to process in casting processes. This is because, particularly when casting low-viscosity glasses, glass melts at different temperatures can readily undergo forced convection, wrinkling, and mixing, which promotes the formation of streaks. Streaks are material variations within the material that result in significant differences in the glass's refractive index.

[0025] When processing multi-component glass by casting, the glass melt advantageously possesses a temperature of 10 1 dPa·s to 10 4 Viscosity in the range of dPa·s.

[0026] One or more castings can be produced simultaneously from this low-viscosity glass melt.

[0027] Due to gravity, the free-flowing glass filament typically has a vertical orientation of its longitudinal axis and, in the simplest and preferred case, reaches the impact zone directly, which is located within the casting cavity or has a fluid connection to the casting cavity. Alternatively, the casting stream can be fed into the impact zone with different orientations of its longitudinal axis by means of deflecting elements (such as feed troughs or feed pipes).

[0028] Specifically, in order to quickly fill the casting cavity with minimal stripe formation and crystallization, the casting stream is divided into a right sub-stream and a left sub-stream after flowing away from the impact zone.

[0029] This division halves the flow path required to close the loop or fill the casting cavity. This also means the flow time is halved or at least reduced. This helps the two sub-flows to have roughly similar thermal histories and surface temperatures, especially when they meet in the merging zone.

[0030] In the simplest and preferred embodiment, the casting stream is divided into two sub-streams within the casting cavity. The casting stream impacts the inner wall of the casting cavity and splits into a right-side sub-stream and a left-side sub-stream. The sub-streams flow around the inner wall of the casting cavity, cool, and rejoin in a merging zone. In the region where the sub-streams merge, distinctive process-related streaks are formed, which are also referred to below as "casting streaks." These casting streaks can be used as positioning markers. This is helpful, for example, in applications where a specific circumferential position of the glass ring must be maintained, or in systems where the same glass ring must be reinstalled in the same position after removal.

[0031] The low-viscosity multicomponent glass cools and solidifies rapidly upon contact with the casting cavity walls. This applies to the sidewalls of the casting cavity and, more importantly, to the cavity floor. Advantageously, the supply of the glass melt and any tilting of the cavity floor are coordinated in such a way that both sub-streams fill the cavity as completely as possible, both covering the cavity floor and contacting the cavity sidewalls. The cavity is optionally filled with a melt front, which preferably extends across the entire width of the cavity, thus moving continuously and at an approximately constant speed over the solidified melt, similar to an avalanche. The thermal insulation of the solidified multicomponent glass helps maintain the high temperature and low viscosity of the glass melt, allowing the melt front to continue moving further toward the merging zone despite the same initial viscosity. This can lead to an increased speed of melt front movement when the cavity floor is completely covered by the solidified glass melt. To adjust the speed of melt front movement, the tilt of the cavity floor relative to the horizontal plane can be varied during the casting process.

[0032] The central axes of the impact zone, the merging zone, and the mold are preferably on the same line.

[0033] In particular, for low-stripe formation and crystallization, it has proven advantageous that the impact zone is located at the upper high-level E1 and the merging zone is located at the lower high-level E2.

[0034] During the casting process, the bottom plate of the mold cavity is tilted at least temporarily relative to the horizontal plane, allowing the molten glass to flow from the impact point at the upper height level E1 to the merging zone at the lower height level E2 within the mold cavity. Starting from the impact zone at the upper height level E1, the cast flow gradually fills the mold cavity. The tilt accelerates the filling of the mold cavity by the molten glass.

[0035] After the glass melt cools, a ring-shaped preform made of multi-component glass can be removed from the mold. The glass ring, with its final product dimensions, is then obtained through further processing. This further processing may include, for example, heat treatment to relieve mechanical stress and / or machining by cutting, grinding, or polishing.

[0036] The impact zone is located at an upper height level E1, which is higher than the lower height level E2 where the merging zone is located, creating an angle of inclination relative to the horizontal plane between these two zones at height levels E1 and E2, such that the angle of inclination is, for example, in the range of 1° to 30°. This allows the molten glass in the casting cavity to flow downwards from the impact zone to the merging zone. The impact zone is fluidly connected to the casting cavity and, for example, is located within the casting cavity. Particularly preferably, the merging zone is located within the casting cavity.

[0037] In this case, it has proven advantageous that the mold is oriented such that the bottom plate of the casting cavity has an inclination relative to the horizontal plane between height levels E1 and E2, wherein this inclination is changed during the casting process.

[0038] The height difference between height levels E1 and E2 can be achieved by the orientation of the entire mold in space with its tilt relative to the horizontal plane and / or by the structural design of the casting cavity base plate having one downward-sloping ramp or multiple downward-sloping ramps. The height difference can remain constant during the casting process, but preferably varies during the casting process. In a preferred variation, a higher tilt angle is set at the start of the casting process, and this tilt angle is reduced at least temporarily during the casting process.

[0039] In its simplest form, the bottom plate of the casting cavity is flat in cross-section between the sidewalls of the casting cavity. In an alternative approach, a bottom plate with a U-shaped or V-shaped cross-section is provided between the sidewalls of the casting cavity, such that the bottom plate guides two branching sub-flows at its center. This may delay the point at which the molten glass contacts the inner or outer wall of the casting cavity. In this embodiment, the mold is also preferably inclined relative to the horizontal plane between height levels E1 and E2, wherein this inclination may change during the casting process.

[0040] Temporary changes in the tilt of the entire mold relative to the horizontal plane are preferably performed by a controlled or adjusting mechanism. Preferably, the tilt is reduced during the casting process.

[0041] Preferably, the tilt of the mold is controlled to prevent glass charge buildup, particularly in the impact zone, and to achieve trouble-free merging of the glass fibers in the merging zone. For this purpose, a tilt angle in the range of 1 to 30 degrees has proven advantageous. Permanent tilt can cause the glass ring height to be inconsistent, resulting in a higher glass ring in the merging zone than in the impact zone. However, by gradually reducing the tilt angle, it is possible to reach a horizontal position before the end of the casting process, thus balancing the generally undesirable height difference.

[0042] When the bottom plate of the casting cavity reaches a horizontal orientation, the change in the mold's inclination typically ceases. Preferably, the rate of change in the mold's inclination is constant; however, this rate can also be variable. Specifically, the rate at the start of the casting process may be higher than the rate at the end. Preferably, the mold's inclination is changed only after the two sub-streams have first merged.

[0043] The variable tilt of the mold, especially the variable tilt of the bottom plate of the casting cavity, helps the glass filaments to merge without failure in the merging zone.

[0044] In this case, it has also proven advantageous if the location of the impact zone is variable during the first casting stage. Initially, the impact zone is preferably located on a slope sloping downwards from the outside towards the inner wall of the casting cavity. During the second casting stage, the location of the impact zone on the slope changes and is preferably shifted outwards away from the inner wall of the casting cavity.

[0045] The ramp may extend along a portion of the outer circumference of the casting cavity. For example, when viewed from above, the ramp is wedge-shaped, wherein the wedge-shaped surface transverse to the slope direction is straight or may have curvature. The ramp can be considered part of the casting cavity or the casting cavity floor. The ramp creates a higher slope in the impact zone. This means that the arriving glass melt is deflected at an angle greater than the inclination angle of the rest of the casting cavity floor but less than 90°, which supports the glass melt flow away from the impact zone. The slope of the ramp can be described as a "ramp angle," wherein the average ramp angle is preferably in the range of 1 degree to 60 degrees, and more preferably in the range of 25 degrees to 45 degrees. In the simplest and preferred case, the slope of the ramp is constant. However, the ramp may also have another concave or convex shape on at least one axis, but it is always a monotonically descending shape.

[0046] The casting process can be divided into several casting stages. During the first casting stage, the molten glass flows onto the mold base plate and fills the base plate area. During this stage, there is no or only a slight accumulation of glass in the impact zone. This can remain in the same position, but back-and-forth oscillating movement of the cast stream is also possible. These back-and-forth oscillating movements that cause displacement of the impact zone are small and typically range from 1 mm to 10 mm.

[0047] The end of the first casting stage is characterized, for example, by the point in time when the bifurcated sub-streams first merge, causing the height of the continuing flowing molten glass (or more precisely, the glass rings) to also accumulate. Therefore, the second casting stage is characterized by the molten glass also moving upwards and the height of the glass rings beginning to accumulate. This means that the molten glass flows over the lower portion of the cooled glass into the mold and fills most or all of the casting cavity. Any existing tilt of the mold can then be reduced (reduced to horizontal and possibly even briefly above horizontal) to flatten any thickness differences from the first casting stage, with the aim of achieving a largely uniform filling level throughout the casting cavity.

[0048] In the second casting stage, relative movement can also occur between the casting stream and the mold, more precisely, between the impact zone and the casting cavity. For example, in the second casting stage, the position of the impact zone shifts outward, advantageously away from the inner wall of the casting cavity on the "rising ramp". This outward shift of the impact zone on the "rising ramp" may occur intermittently, but preferably continuously, and preferably in the direction of the connecting line between the impact zone and the merging zone. During the second casting stage, the shifting speed on the rising ramp is constant or variable, and preferably in the range of 1 mm / min to 100 mm / min, more preferably in the range of 1 mm / min to 30 mm / min.

[0049] The connecting line between the impact zone and the merging zone advantageously passes through the centerline of the annular casting cavity. In this case, the right sub-stream and the left sub-stream have equal lengths, and the merging zone is located at the lowest point of the casting cavity in plane E2. If the formation of the merging zone above plane E2 becomes significant during the casting process, this can be advantageously counteracted by displacing the impact zone relative to the mold. The impact zone can be displaced along the circumference of the annular casting cavity in the azimuth direction, or more simply and therefore preferably by moving the mold laterally perpendicular to the connecting line mentioned above, or by tilting the mold around and along the connecting line (i.e., by lateral tilting), or by rotating the mold (e.g., around the center of the annular casting cavity). During the relative displacement of the impact zone, the height distance between the outlet of the glass filament and the impact point advantageously remains constant. This means that, for example, in the case where the impact zone reaches a slope, the relative displacement of the impact zone follows the shape of the slope (straight or curved) in the displacement direction.

[0050] The term "casting process" here and below refers to the entire method steps of casting molten glass into a mold, including a first casting stage, a second casting stage, and an optional third casting stage. The third casting stage may include measures taken after the mold has been fully filled to complete the actual casting process.

[0051] As the impact zone shifts along the rising ramp, the casting cavity continues to fill with molten glass during the second casting stage, and the vertical distance between the outlet for the cast stream and the surface of the molten glass in the impact zone may shorten. To maintain this distance constant, it is advantageous to lower the mold during the second casting stage.

[0052] Due to the preferred continuous displacement of the impact zone and the preferred continuous lowering of the mold, the glass melt is deflected from the impact zone into the casting cavity, such that although the melt diffuses horizontally and fills the casting cavity, the meniscus of the glass melt flowing into the casting cavity remains approximately constant.

[0053] During the casting process, a ramp typically forms a closed surface that the casting stream impacts. However, in a preferred variation of this method, the ramp can be opened and closed, and optionally equipped with a closable opening. Before filling the casting cavity begins, the opening is opened, allowing the casting stream to fall downwards through it. By closing the opening, the casting stream is cut off and redirected from its vertical descent direction, from the ramp towards the bottom plate of the casting cavity.

[0054] For example, the opening and closing of the ramp opening is performed by means of a portion of the ramp, which can move horizontally and radially in the direction of the mold's central axis, and is referred to below as a "slider". The slider can be considered as part of a multi-part ramp or a multi-part mold. When the ramp is open, the slider is positioned at a certain distance from the rest of the mold, thus leaving a "casting gap". In this case, the casting gap forms the opening of the ramp. At the start of the casting process, the ramp (casting gap) is open, and the casting flow flows freely downward through the casting gap. For example, in this casting gap, the casting flow is collected in a container. The casting gap closes by pushing the slider toward the rest of the mold. The originally vertically oriented casting flow is cut like scissors, impacts the ramp in the impact zone, and then flows further down the ramp at an angle of less than 90 degrees, as explained in more detail above with reference to the description of the ramp. When closed, the slider forms part of the ramp.

[0055] Therefore, the first advantageous function of the slider is to close the casting gap and separate the glass filament flowing vertically through the casting gap from above. The second advantageous function of the slider is to deflect the glass filament in the direction of the mold's central axis, thereby redirecting the outflow of the sub-flow from the impact zone towards the merging zone. Furthermore, it has also proven helpful that when the casting gap is closed, the slider is adjacent to the casting cavity bottom plate and, for example, tangentially contacts the outer periphery of the casting cavity bottom plate.

[0056] The flow rate of the glass melt is preferably measured in the range of 150 ml / min to 3000 ml / min, and particularly preferably in the range of 300 ml / min to 1500 ml / min. Preferably, in the casting process, the flow rate is constant, but it can also be variable.

[0057] The method according to the invention is particularly suitable for processing glass melts with low viscosity. The viscosity during feeding is preferably in the range of 10 Pa·s to 10,000 dPa·s, and particularly preferably in the range of 100 Pa·s to 1,000 dPa·s.

[0058] During the casting process, the flowing molten glass heats the mold. Heating the mold has proven advantageous, especially at the beginning of the casting process, to counteract the rapid cooling of the molten glass on the walls of the casting cavity.

[0059] Heating the mold has proven advantageous in reducing the high heat loss of the molten glass at the mold cavity walls. Heating is preferably carried out electrically, for example, by induction, by radiation, or by means of a heating cylinder. The heating temperature depends on the temperature / viscosity profile of the given glass. For example, the heating temperature is in the range of the so-called transformation or glass-forming temperature Tg or lower, such as in the temperature range of Tg-300°C to Tg. Heating reduces the risk of cracking during the cooling of the glass rings and has a positive effect on flow properties by preventing excessively rapid cooling below Tg. Alternatively or additionally, it is also advantageous to thermally insulate the mold, for example, by placing a refractory material over the mold or by actively heating the molten glass in the mold from above (e.g., by means of a gas flame or a porous burner).

[0060] In a preferred variation of the method, the inner wall and / or outer wall of the casting cavity are conical and movable in the vertical direction relative to the bottom plate of the casting cavity.

[0061] The inner wall is formed, for example, by a lowerable cylinder or ring, preferably a cone. During the cooling of the glass melt, the cylinder / cone (i.e., the inner wall of the casting cavity) can preferably move vertically a few millimeters, thereby creating a gap between the solid glass and the inner wall of the casting cavity. In the case of a conical inner wall, it is irrelevant whether the cone tapers upwards or downwards: the vertical movement during cooling always occurs in such a way that the diameter of the inner wall decreases compared to the inner diameter of the glass ring, thus creating a gap and therefore preventing wedging when the glass ring is removed from the mold.

[0062] Regarding the apparatus for producing glass rings from multi-component glass, the aforementioned objective is achieved by an apparatus having the features described in claim 11.

[0063] The device includes

[0064] (a) A casting mold comprising an annular casting cavity extending about a central axis, the annular casting cavity having a casting cavity height and having a casting cavity bottom plate defined by an inner wall and an outer wall, and a casting cavity opening opposite the casting cavity bottom plate.

[0065] (b) for supplying the molten glass to the outlet of the mold, and

[0066] (c) A moving unit for spatial movement of the outlet and / or the mold.

[0067] The moving unit is used to position the mold at a specified location and / or orientation relative to the outlet, and / or to move the mold along a specified moving path relative to the outlet. Preferably, the necessary positioning and movement of the mold or outlet are performed by the moving unit in a computer-controlled manner.

[0068] Therefore, the moving unit preferably has components (such as joints and axes of rotation) for rotating and tilting the component, and the moving unit has components (such as linear units) for translating the component in three spatial directions x, y, z, where "z" here represents the height direction.

[0069] The device has displacement, tilting, rotation, and / or sliding functions. Specifically, the casting stream flowing out of the outlet can be positioned such that it impacts an impact zone and flows from that zone to the inner wall of the casting cavity, where the casting stream is divided into a right-side sub-stream and a left-side sub-stream. The sub-streams flow together at a merging zone within the casting cavity, as explained above in the description of the method according to the invention.

[0070] The impact zone is preferably located at the upper height level E1, and the merging zone is located at the lower height level E2.

[0071] This apparatus is adapted to perform the method according to the invention. Advantageous embodiments of the apparatus according to the invention can be found in the dependent claims. For further explanation regarding embodiments of the apparatus specified in the dependent claims designed according to the method mentioned in the dependent claims for the method according to the invention, please refer to the above statements concerning the corresponding method claims.

[0072] Regarding the glass ring made of multi-component glass, the aforementioned objective is achieved by a glass ring having the features described in claim 16.

[0073] The glass ring can be produced using the method according to the invention. Sub-flows flowing around the inner wall of the casting cavity and converging in the merging region form casting stripes in the region at the azimuth position of the merging region. These stripes partially or preferably completely traverse the ring cross-section in the radial direction. The optical detection capability of the casting stripes in the glass ring is improved if an optical path difference of at least 30 nm is generated in the multi-component glass.

[0074] Since there is only a single casting stripe throughout the entire cross-section of the ring, this casting stripe can be used as a position marker. This is helpful, for example, in applications where a specific circumferential position of the glass ring must be maintained, or in systems where the same glass ring must be reinstalled in the same location after removal.

[0075] Multicomponent glasses are characterized by high purity, which is exemplified by the fact that impurities of Cr, Mn, Fe, Co and Ni, as well as compounds of each of these elements, are each less than 50 ppm by weight, particularly preferably less than 20 ppm by weight, and the sum of impurities of Cr, Mn, Fe, Co and Ni is less than 100 ppm by weight.

[0076] In addition, high-purity multicomponent glass is characterized by its higher dry etching stability in reactive ion etching (RIE) compared to quartz glass.

[0077] Therefore, glass rings are suitable as plasma etching rings for holding wafers during plasma-assisted dry etching processes. Glass rings typically have an outer diameter in the range of 300 to 500 mm, a wall thickness greater than 10 mm, and a height of at least 5 mm.

[0078] Definitions and measurement methods

[0079] The terms used in the above specification are further defined below. These definitions are part of this specification. For terms and measurement methods not specifically defined in the specification, the interpretation of the International Telecommunication Union (ITU) shall apply. In the event of any inconsistency between one of the following definitions and the rest of the specification, the statements elsewhere in this specification shall prevail.

[0080] Multi-component glass

[0081] Multicomponent glasses consist of at least three components. In the simplest and preferred case, the multicomponent glass is a pure oxide glass, wherein all anions are composed of oxygen ions (O₂). 2- The composition is as follows: Oxygen ions can occupy 100% of the anionic sites in the glass's network structure. In another equally preferred embodiment, some oxygen ions are replaced by fluoride ions. In this case, the multi-component glass has a network structure with anionic sites, wherein...

[0082] (100-x)% of the anion sites are occupied by oxygen ions (O). 2- ) occupy, and the fraction x (%) is occupied by fluoride ions (F - ) occupy, where x is the degree of substitution (in %) and is in the range between 0.1 and 10.

[0083] slope

[0084] The ramp can be considered as part of the casting cavity and also as part of the lateral boundary of the outer wall of the mold. The ramp has a slope in the direction of the mold centerline and is used to deflect the glass flow from the outlet pipe, guiding the glass fiber from its vertical orientation on the bottom plate of the casting cavity toward the inner wall of the cavity. For this purpose, the ramp can be equipped with a closable casting gap.

[0085] Viscosity

[0086] The processing of multi-component glasses is carried out in a liquid, low-viscosity state, through a process involving 10... 1 dPa·s to 10 4 Viscosity in the range of dPa·s, preferably in the range of 10 2 dPa·s to 10 3 Viscosity is characterized by a range of dPa·s. For multicomponent glasses, this viscosity range is typically achieved at temperatures ranging from 900°C to 1500°C. Viscosity is measured by shear or rotational viscometry according to DIN ISO 7884-2 (1998).

[0087] Viscosity values ​​are typically specified using the common logarithm in the form of log(dPa·s) rather than exponential notation.

[0088] stripe

[0089] Stripes are spatially finite fluctuations in the material homogeneity within glass, causing localized differences in refractive index. The size is short-range, ranging from approximately 0.1 mm to approximately 2 mm. Differences in refractive index (optical path difference) are typically only visually perceptible starting from 30 nm.

[0090] Therefore, the fringes can be characterized as optical features. The casting fringes that appear at the junction of the sub-flows are the sum of a large number of small defects (stripes) aligned along the radius of the glass ring. Individual stripes have a small extent of extension in the circumferential direction, but overall they have a large area and extend to the outer edge of the glass ring.

[0091] For optical marking of stripes at the location of cast stripes, the shading method is appropriate, as described in the manual "Technical information for optical devices TIE-25: Striae inoptical glass" published by Schott AG in June 2006.

[0092] Measurement of dry etching resistance

[0093] To measure dry etching resistance, a standard dry etching procedure was performed on multi-component glass samples in a RIE plasma reactor. The processing steps are as follows:

[0094] (a) Polish one flat side of the test sample to give it R a The value is a surface roughness of 4 nm or less.

[0095] (b) Cover the polished, flat side of the surface with varnish.

[0096] (c) A dry etching process is performed on the polished flat side, characterized by the following parameters:

[0097] ● Feed 600 watts of power to the HF energy source.

[0098] ●Use an HF power source to apply a negative 100 volt bias voltage to the test sample with an input power of 10 watts.

[0099] ● Introduce the following process gases into the reaction chamber: 5 sccm argon, 1 sccm CF4, and 0.3 sccm O2.

[0100] ● Set the chamber pressure to 6 Pa.

[0101] ● The etching time is 60 minutes.

[0102] Compared to a reference sample made of synthetic quartz glass (Suprasil; trade name of Heraeus Quarzglas GmbH & Co. KG), the etching rate was less than 50%, therefore the multicomponent glass was classified as dry-etch resistant.

[0103] purity

[0104] A multicomponent glass is defined herein as “high purity” if the fractions of impurities of Cr, Mn, Fe, Co and Ni, and the fractions of compounds of each of these elements, are less than 50 ppm by weight, and if the sum of impurities of Cr, Mn, Fe, Co and Ni is less than 100 ppm by weight.

[0105] Exemplary Implementation

[0106] The invention will now be explained in more detail with reference to exemplary embodiments and accompanying drawings. Specifically, in the schematic diagrams,

[0107] Figure 1 A three-dimensional view shows the mold for producing glass rings mounted on a frame.

[0108] Figure 2 Along Figure 1 The cross-sectional side view of line AA' shows details of the mold and frame.

[0109] Figure 3 A sketch is shown to explain the height level and tilt of the mold.

[0110] Figure 4 A sketch is shown to illustrate the impact zone and merging zone when casting glass rings.

[0111] Figures 5 to 12 A sketch is shown to explain the steps of the method for producing glass rings.

[0112] Figure 1 An embodiment of the device of the present invention is schematically shown, wherein a mold 1 is mounted on a frame 2. The frame 2 is equipped with a linear unit 2a for positioning the mold 2 in the height direction (z-direction) and another linear unit 2b for translating the mold 2 in a plane (x-direction). Furthermore, the frame 2 has an electrically movable joint 2c for adjusting the tilt of the mold 1. The orientation is shown by coordinate system 3. The movement of the mold 1 by means of the linear units 2a and 2b and the tilting of the mold 1 by means of the joint 2c are performed in a computer-controlled manner.

[0113] This apparatus is used to produce glass rings from high-purity multi-component glass by casting molten glass into a mold 1. The mold 1 has a circular, closed casting cavity 1a that opens at the top. A fixed outlet pipe 4 ( Figure 2 It is positioned above the casting cavity 1a. The glass melt is supplied from a conventional melting crucible (not shown) to the outlet pipe 4.

[0114] Further details of mold 1 are available in Figure 2 As can be seen, the casting cavity 1a has a circular casting cavity base plate 1b opposite to the gap opening. This circular casting cavity base plate is defined on the outer side by an annular outer wall 1c and on the inner side by an inner wall 1d. The outer diameter of the casting cavity 1a is 360 mm, the inner diameter is 300 mm, and the height is 30 mm.

[0115] The inner wall 1d is formed by the insert body 1e, which tapers slightly towards the top. During the casting process, the insert body 1e closes the central opening of the mold 1, which extends coaxially with the central axis 1f. After the casting process, the insert body is pushed downward (in the y-direction) out of the central opening.

[0116] A portion of the outer wall 1c or a portion of the casting cavity bottom plate 1b is formed by a wedge-shaped body 1g, which is displaceable in the radial direction (x direction) and arranged before the casting process such that it leaves a casting gap with the mold 1. The method and... Figures 6 to 12 The function of the wedge-shaped body 1g and the casting gap will be explained in more detail.

[0117] At the start of the casting process, the mold 1 is oriented in space such that the bottom plate 1b of the casting cavity is inclined relative to the horizontal plane. This is in Figure 3 The angle α is indicated in the sketch.

[0118] Mold 1 is positioned at outlet pipe 4 ( Figure 2 Below this point, the initial impact zone 5 of the casting flow is formed at a height level E1. From this height level, the casting flow enters the casting cavity 1b and reaches the inner wall 1d of the casting cavity, which acts as a "watershed" for the glass melt, dividing the casting flow into a right sub-flow 7a and a left sub-flow 7b. This schematically indicated dividing zone 5a is located at... Figure 4The region included in the plan view is the area at the intersection of the inner wall 1d of the casting cavity and the centerline 1r of the mold 1. Two sub-flows 7a and 7b flow downwards in the casting cavity 1b according to their inclination and merge in the merging zone 6 located at height level E2. The impact zone 5, the dividing zone 5a, the merging zone 6, and the central axis 1s of the mold 1 extending perpendicular to the plane of the sheet are located on the centerline 1r. Over time, the casting cavity 1a fills with glass melt, thereby forming casting stripes 6a in the region of the merging zone 6. Small defects, such as small streaks, can be seen in the casting stripes 6a. The casting stripes 6a form a visually recognizable whole of these smaller streaks.

[0119] In an exemplary embodiment, the initial inclination of the casting cavity bottom plate 1b is 15 degrees, and when the distance between the impact zone 5 and the merging zone 6 is 370 mm, the height difference y1 between the height level E1 at the raised end of the casting cavity bottom plate 1b and the height level E2 at the opposite end of the casting cavity bottom plate 1b is approximately 61 mm.

[0120] The following text uses references Figures 1 to 12 The following examples illustrate the method according to the invention in more detail:

[0121] Glass ring 13 produced by casting Figure 12 The outer diameter of the mold is 360 mm, the inner diameter is 300 mm, and therefore the wall thickness is 30 mm and the height is 25 mm. The casting cavity 1a of the mold 1 is designed accordingly.

[0122] Melt a glass melt having the following composition in a crucible:

[0123]

[0124] At a melting temperature of approximately 1380°C, glass has a viscosity of approximately 100 dPa·s.

[0125] Figure 5 The mold 1, outlet pipe 4, and casting stream 8 are schematically shown, which flows vertically through the mold 1 and out of the outlet pipe 4. The mold 1 is initially inclined at 15 degrees relative to the horizontal plane. A stable jet with a flow rate of 1000 ml / min is established and then continued. Unused glass frit is collected in a container.

[0126] Figure 6 The method step (1) is schematically illustrated, in which a wedge 1g is pushed radially toward the casting flow 8, as indicated by the directional arrow 1h. An ramp 1i is formed on the upper side of the wedge 1g facing the mold 1, which slopes downward toward the mold 1. The casting flow 8 initially flows through a casting gap 9, which is formed between the ramp 1i and the bottom plate 1b of the casting cavity of the mold 1.

[0127] Figure 7 The method step (2) is shown, in which the ramp 1i finally closes the casting gap 9 by further pushing the body 1g forward, thereby interrupting the casting flow 8. The casting flow impacts the ramp 1i in the region of the initial impact zone 5. Figure 6 ), and from there deflected to the bottom plate 1b of the casting cavity ( Figure 4 As indicated by directional arrow 1k, this marks the beginning of the first casting stage. The vertical casting stream 8 impacts the initial impact zone 5 at a height of horizontal E1, dividing into two sub-streams 7a and 7b in the dividing zone 5a. Figure 4 These two sub-flows flow around the insert body 1e and merge again in the region of the merging zone 6 at a lower height level E2, thus forming the casting stripe 12.

[0128] The initial impact zone 5 is located on the surface of the wedge 1i, which forms a downward-sloping ramp for the glass melt 11 to flow into the mold. This ramp is inclined at 30 degrees relative to the mold base plate. Together with the 15-degree tilt angle caused by the initial tilt of the mold base plate 1b, this results in an impact surface for the casting flow 8 at the initial impact zone 5, which is inclined downward at 45 degrees relative to the horizontal plane.

[0129] The glass melt 11 cools and solidifies on the walls of the casting cavity 1a, particularly on the bottom plate 1b of the casting cavity. As the casting cavity 1a continues to be filled, the melt front 7c (in) Figure 4 (Indicated by an arc-shaped gray area extending across the entire width of casting cavity 1a) it moves continuously further toward merging zone 6 at an approximately constant speed over the solidified melt. Layering the glass melt as uniformly as possible prevents convection and associated streaks.

[0130] Once the casting cavity bottom plate 1b is completely covered by the solidified glass melt, this causes the two melt fronts 7c to merge in the merging zone 6. To reduce the movement speed of the melt fronts 7c, the inclination of the casting cavity bottom plate 1b relative to the horizontal plane is continuously reduced at approximately 15 degrees per minute.

[0131] Therefore, in step (3) of the method, the mold 1 gradually enters a horizontal orientation, as... Figure 8 The direction arrow 1m is schematically shown, and the second casting stage begins. The pivot point for the tilting movement is fixed and located in the outlet area of ​​outlet pipe 4.

[0132] Meanwhile, the mold 1 is continuously lowered relative to the fixed outlet pipe 4 at a speed of approximately 15 mm / min, as indicated by the directional arrow 1n, and moves along the contour of the ramp, so that the outlet pipe 4 and the glass melt 11 maintain a roughly constant distance of approximately 3 mm to 5 mm.

[0133] Figure 9The method step (4) is schematically illustrated, in which the mold 1 and the casting cavity bottom plate 1b ( Figure 4 Together, they have achieved a horizontal orientation. The glass melt 11 in the initial impact zone 5 has been cooled to a temperature below the softening temperature of the glass and submerged by another low-viscosity glass melt 11, thus forming a horizontal melt surface. By continuously lowering the mold 1 relative to the outlet pipe 4 ( Figure 8 As indicated by directional arrow 1n, and by continuously translating the mold 1 as indicated by directional arrow 1o, a new impact zone 5.1 for the casting flow 8 has been generated. This new impact zone continues to be located at approximately the same distance above the ramp 1i of the wedge-shaped body 1g. The new impact zone 5.1 is permanently located at the edge of the forming glass ring, such that the flow direction of the glass melt 11 always points towards the center of the mold, or at most deflects to one side, but no glass melt flows in the opposite direction.

[0134] The casting process continues until the glass melt 11 has filled the casting cavity 1 to reach the glass ring 13 to be produced. Figure 12 The degree of height of ). This state (method step (5)) in Figure 10 As shown in the image.

[0135] The subsequent method step (6) can be referred to as the third casting stage, in which the casting process is terminated by the following: the casting stream 8 still flowing from the outlet pipe 4 is guided away from the ramp of the insert body 1g by means of the wedge-shaped body 1g, along with the remaining mold 1 (such as... Figure 11 (As indicated by the directional arrow 1p) it moves together so that it reaches the area of ​​the recess 12 in the insert body 1g and falls vertically downward into the collection container.

[0136] As per reference Figures 5 to 11 In the steps (1) to (6) of the method explained, the movement of the mold 1 and the wedge body 1g is performed in a computer-controlled manner.

[0137] During the further cooling of the glass melt 11, the conical insert body 1e is lowered by a few millimeters (method step (7)), as... Figure 12 The direction arrow 1q indicates this. This prevents the heated glass ring 13 from shrinking onto the inner wall 1d.

[0138] The resulting annular glass preform 13 is tempered and ground to the desired dimensions of the glass ring in a stress-free manner, which are almost achieved by near-net-shape forming in the casting process.

[0139] This yields a glass ring made of high-purity multi-component glass, characterized by high transparency, high purity, and high plasma resistance.

[0140] The high purity of multicomponent glasses is demonstrated by the fact that the fractions of impurities Cr, Mn, Fe, Co and Ni, as well as the fractions of compounds of each of these elements, are less than 50 ppm by weight, and the total fraction of impurities Cr, Mn, Fe, Co and Ni is less than 100 ppm by weight.

[0141] The high plasma resistance of multi-component glass is demonstrated by the fact that its etching rate is less than 25% of that of synthetically produced quartz glass (Suprasil) when a standard dry etching process is performed.

[0142] The glass ring shows distinctive casting stripes 6a ( Figure 4 The casting stripe extends across a portion or the entire cross-section (full width and full height) of the glass ring in the region of the previously merged region 6. The casting stripe 6a has a circumferential extension of less than 2 mm and induces an average optical path difference greater than 30 nm in multicomponent glass for a measurement beam with a measurement wavelength of 535 nm. The casting stripe can be used as a position marker in systems such as plasma etching systems for semiconductors.

Claims

1. A method for producing glass rings from multi-component glass, characterized in that, A ring-shaped preform is produced from the multi-component glass using a casting process, the casting process comprising the following steps: (a) A mold (1) is provided, the mold comprising an annular casting cavity (1a) extending about a central axis (1s), the annular casting cavity having a casting cavity height, and having a casting cavity bottom plate (1b) defined by an inner wall (1d) and an outer wall (1c), and a casting cavity opening opposite to the casting cavity bottom plate. (b) The glass melt used to produce the multi-component glass. (c) The casting stream (8) of the glass melt is fed into the mold (1), wherein the casting stream (8) impacts the impact zone (5; 5.1) and branches into a right sub-stream (7a) and a left sub-stream (7b), wherein the sub-streams (7a; 7b) merge at the merging zone (6) in the casting cavity (1a) and fill the casting cavity (1a) at least a portion of the height of the casting cavity. (d) The glass melt contained in the casting cavity (1a) is cooled to form an annular blank (13), and the annular blank (13) is further processed to form a glass ring.

2. The method according to claim 1, characterized in that, The impact zone is located at the upper height level E1, and the merging zone is located at the lower height level E2, wherein the mold is preferably oriented such that the bottom plate of the casting cavity has an inclination relative to the horizontal plane between the height levels E1 and E2, wherein the inclination changes during the casting process.

3. The method according to claim 2, characterized in that, During the first casting stage, the impact zone is located in the region of a slope sloping downwards from the outside in, and during the second casting stage, the position of the impact zone on the slope changes, preferably shifting outwards, wherein the mold is preferably lowered during the second casting stage.

4. The method according to claim 3, characterized in that, The ramp can be opened and closed, wherein the casting flow is cut off and redirected from the vertical falling direction to the bottom plate of the casting cavity by closing the ramp.

5. The method according to one or more of the preceding claims, characterized in that, The casting flow is metered to a flow rate in the range of 150 ml / min to 3000 ml / min, preferably in the range of 300 ml / min to 1500 ml / min.

6. The method according to one or more of the preceding claims, characterized in that, The glass melt is adjusted to a feed viscosity in the range of 10 dPa·s to 10,000 dPa·s, particularly preferably in the range of 100 dPa·s to 1,000 dPa·s.

7. An apparatus for producing glass rings from glass by casting molten glass, the apparatus comprising: (a) A casting mold comprising an annular casting cavity extending about a central axis, the annular casting cavity having a casting cavity height and having a casting cavity bottom plate defined by inner and outer walls, and a casting cavity opening opposite the casting cavity bottom plate. (b) For supplying the molten glass to the outlet of the mold, The device is characterized by having a moving unit for spatial movement of the outlet and / or the mold, by means of which the mold can be moved relative to the outlet and positioned such that the casting stream flowing out of the outlet pipe impacts the impact zone and branches into a right sub-stream and a left sub-stream, and the sub-streams merge at a merging zone in the casting cavity.

8. The apparatus according to claim 7, characterized in that, The moving unit is designed to adjust the inclination of the mold relative to the horizontal plane in such a way that the impact zone is located at the upper height level E1 and the merging zone is located at the lower height level E2.

9. The apparatus according to claim 7 or 8, characterized in that, The moving unit is designed to lower the mold relative to the outlet.

10. The apparatus according to claim 9, characterized in that, The casting cavity bottom plate includes a ramp with an opening that can be closed by means of a movable slider.

11. A glass ring made of multi-component glass, the glass ring having a centerline and a cross-section defined by an upper side, a bottom side opposite to the upper side, an outer wall and an inner wall, and the glass ring having radial casting stripes at an azimuth position, the casting stripes extending radially in the region between the inner wall and the outer wall relative to the centerline.

12. The glass ring according to claim 11, characterized in that, The casting stripes completely fill the cross-section between the upper side, the bottom side, the outer wall, and the inner wall.

13. The glass ring according to claim 11 or 12, characterized in that, The casting stripes produce an optical path difference of at least 30 nm for a measurement beam with a wavelength of 535 nm.

14. The glass ring according to one or more of claims 11 to 13, characterized in that, The glass ring has an outer diameter in the range of 300 mm to 500 mm and a wall thickness of at least 10 mm.

15. The glass ring according to one or more of claims 11 to 14, characterized in that, In the multicomponent glass, the fractions of impurities of Cr, Mn, Fe, Co and Ni, and the fractions of compounds of each of these elements, are each less than 50 ppm by weight, and particularly preferably less than 20 ppm by weight, and the sum of said impurities of Cr, Mn, Fe, Co and Ni is less than 100 ppm by weight.

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