Titania-silica glass with reduced hydroxyl and halide concentrations and method for producing it

Abstract

A glass body containing titania and silica, wherein the average hydroxyl concentration between multiple segments of the glass body is approximately 0 ppm to approximately 100 ppm, the peak-valley of the hydroxyl concentration between multiple segments is approximately 60 ppm or less, the hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy, the multiple segments include all adjacent segments across the length and width of the glass body, the length is approximately 25 mm or more, the width is approximately 25 mm or more, and the glass body contains a chlorine concentration of approximately 100 ppm or less.

Description

[Technical Field]

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 521479, filed June 16, 2023, and Dutch Patent Application No. 2035339, filed July 11, 2023, which is relied upon and incorporated herein in its entirety by reference.

[0002] This disclosure relates to titania-silica glass having reduced hydroxyl and halide concentrations, and methods for producing the same, more specifically, to titania-silica glass having low concentrations of hydroxyl and halides that achieve a homogeneous coefficient of thermal expansion throughout the glass. The resulting glass articles may be suitable for use in extreme ultraviolet lithography applications. [Background technology]

[0003] Extreme ultraviolet (EUV) lithography uses optical elements to irradiate, project, and reduce patterned images to form integrated circuit patterns. The use of extreme ultraviolet radiation is beneficial in that it can achieve smaller integrated circuit features. Optical elements for EUV lithography are currently made from low thermal expansion glass, such as silica-titania glass. This glass is traditionally produced by a flame hydrolysis process in which a high-purity precursor is injected into a flame to form glass nanoparticles, which are then deposited onto a glass body.

[0004] In EUV lithography systems, glass is typically coated with a reflective surface to form a reflective mirror or photomask. Furthermore, this glass must be able to meet the strict thermal expansion requirements of the EUV lithography system. Specifically, it must be able to maintain its surface shape (known as "morphology") when exposed to temperature changes in the system. Temperature-stable glass is required to avoid any distortion induced in the wavefront properties of the EUV projection optical element. [Overview of the project]

[0005] Embodiments of the present disclosure include methods for manufacturing glass bodies that can advantageously maintain their shape during operation of an EUV lithography system. Accordingly, according to embodiments of the present disclosure, the glass bodies reduce or prevent any distortion in the wavefront characteristics of an EUV projection optical element.

[0006] According to aspects of the present disclosure, a glass body containing titania and silica is disclosed, wherein the average hydroxyl concentration between multiple segments of the glass body is about 60 ppm or less, the hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy, the multiple segments include all adjacent segments across the length and width of the glass body, the length is about 25 mm or more, the width is about 25 mm or more, and the glass body contains a chlorine concentration of about 5 ppm or less.

[0007] According to an aspect of this disclosure, titania-doped silica soot is pressurized to obtain a titania-doped silica soot of approximately 0.65 g / cm³. 3 A method is disclosed comprising the steps of forming a molded soot body having the above density, fixing the molded soot body by heating it, and annealing the fixed glass body, wherein the fixed and annealed glass body contains a chlorine concentration of about 5 ppm or less.

[0008] Although this specification concludes with claims that specifically identify and clearly claim the subject matter described herein, it is believed that this description will be better understood from the following specification when used in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart of the process for forming a glass body according to embodiments disclosed herein. [Figure 2A]This is a schematic diagram of a system that generates loose soot particles in the process shown in Figure 1, according to embodiments disclosed herein. [Figure 2B] The molded product produced by the process shown in Figure 1 is shown. [Figure 2C] The molded product produced by the process shown in Figure 1 is shown. [Figure 3] Figure 1 is a flowchart of the process for fixing the process. [Figure 4] Figure 1 is a flowchart of the process for fixing the process. [Figure 5] Figure 1 is a flowchart of the process for fixing the process. [Figure 6] Figure 1 is a flowchart of the process for fixing the process. [Figure 7A] An exemplary glass body according to embodiments disclosed herein is shown. [Figure 7B] Figure 7A shows a cross-sectional view of a glass sample according to an embodiment disclosed herein. [Figure 7C] Another cross-sectional view of the glass sample of Figure 7A having an outer peripheral edge, according to an embodiment disclosed herein, is shown. [Modes for carrying out the invention]

[0010] As used herein, "ppm" means parts per million by weight.

[0011] As used herein, "atm" means atmospheric pressure.

[0012] As used herein, the terms "hydroxyl(plural)" or "OH" refer to oxygen atoms and protium atoms (1) unless otherwise specified. 1 H (hereinafter referred to as "H") means a part or group of parts consisting of each of these. As used herein, n(OH) means the total number of OH or hydroxyl parts in the material.

[0013] As used herein, “protium” refers to the hydrogen isotope having a mass number of 1 and consisting of a single proton and electron. Unless otherwise specified, the symbols “H” and “H2” refer to protium (1) 1 H) represents atoms and molecules. As used herein, the terms n(H) and n(H2) represent the total number of protium atoms and molecules in the material, respectively.

[0014] As used herein, “deuterium” refers to the hydrogen isotope having one proton and one neutron in its nucleus and an atomic weight of 2.0144. Unless otherwise specified, the symbols “D” and “D2” refer to deuterium (1 2 H) Represents atoms and molecules. As used herein, the terms n(D) and n(D2) represent the total number of deuterium atoms and molecules in the material, respectively.

[0015] As used herein, the terms “duteroxyl” (plural) or “OD” refer to an oxygen atom and a deuterium atom (1 2 H or 1 2 D (hereinafter referred to as "D") means a portion or group of portions consisting of D. As used herein, n(OD) means the total number of OD portions in the material. When hydroxyl and deuteroxyl groups are present in their natural isotopic abundances, the ratio of n(OD) / (n(OD)+n(OH)) in the material is 2 x 10⁻¹⁰ -4 It is equal to.

[0016] As used herein, the terms “hydrogen” and “molecular hydrogen” refer to a spontaneously occurring mixture of molecules and atoms of protium and deutherium (99.98% protium and 0.02% deutherium), unless otherwise specified.

[0017] Unless otherwise specified, when referring to any element other than hydrogen, it is understood that the element exists in its spontaneous state, that is, its isotopic distribution occurs naturally, and the element is not enriched in any single isotope.

[0018] As used herein, the term “virtual temperature” refers to a concept used to identify the structural state of glass. Glass cooled rapidly from a high temperature typically exhibits a higher virtual temperature than the same glass cooled more slowly from the same temperature, due to a “frozen” higher temperature structure. When glass is held at a high temperature, the glass structure is given more time to relax toward the heat-treated temperature structure. Glass with a relatively high virtual temperature has a structure further away from equilibrium than glass with a relatively low virtual temperature.

[0019] Figure 1 illustrates process 100 for producing a titania-silica (TiO2-SiO2) glass body suitable for use in EUV lithography applications. As will be further discussed below, the resulting glass has a low halide concentration and a uniform OH concentration throughout the glass body. A uniform distribution of OH is necessary to achieve uniform thermal expansion throughout the glass body, as the thermal expansion properties depend (at least partially) on OH uniformity. Having uniform thermal expansion throughout the glass body prevents the glass body from changing shape when exposed to different temperature environments, which is beneficial, for example, in lithography applications. Therefore, the glass bodies disclosed herein are suitable for use, for example, in EUV lithography applications. The glass may be an ultra-low expansion glass (ULE® glass) manufactured by Corning Incorporated.

[0020] EUV lithography technology relies on an optical projection system to expose reflective mirrors and / or photomasks with EUV light so that light reflected from the mirrors and / or photomasks is directed onto a thin photosensitive layer deposited on the surface of a semiconductor wafer. This technique is commonly used in the manufacturing process of semiconductor devices. EUV lithography systems operate at a wavelength of light of approximately 13.5 nm. This very short wavelength presents several challenges in the design of EUV systems. For example, the reflective coating on the mirror and / or photomask in an EUV system cannot reflect all light with such a short wavelength. Approximately 30% of the light is absorbed by the reflective coating rather than reflected. The absorbed light generates undesirable heat in the glass body, altering its shape (e.g., thermally expanding or contracting). Such changes in the glass body can then deform the reflective coating on the glass body, leading to wavefront distortion of the reflected light. Wavefront distortion can lead to a decrease in the resolution of the EUV system and errors in the patterns formed on the photosensitive layer.

[0021] Therefore, the glass bodies of mirrors and / or photomasks must be able to maintain their shape and form even when exposed to the severe thermal loads of the EUV system. Silica-titania glass, such as ULE® glass, is currently the material of choice for glass bodies in EUV systems.

[0022] Recent studies have shown that a higher level of compositional uniformity in silica-titania glass in EUV systems minimizes any changes in the shape of the glass. More specifically, with such a higher level of uniformity, the glass maintains its overall shape when exposed to temperature changes in an EUV system. Embodiments of the present disclosure relate to producing a glass body having such compositional uniformity. Specifically, embodiments of the present disclosure relate to producing a glass body having a uniform OH (and OD) concentration.

[0023] Furthermore, embodiments of this disclosure relate to producing glass bodies having low concentrations of OH (and OD). At relatively low concentrations of OH (and OD), it is easier to achieve the desired compositional uniformity in the glass than at relatively high concentrations. More specifically, at relatively low concentrations, any deviation from the average OH (or OD) concentration is still within an acceptable range for achieving the required compositional uniformity. Because the OH (and OD) concentration is very low, any deviation from the average OH (or OD) is also very low. However, at higher concentrations, the deviation from the average concentration can be very large, and therefore produces OH (and OD) concentrations that vary widely across the glass body. Because the OH (and OD) concentration is very high, the deviation from the average can also be very high.

[0024] It is also known in the art that glass bodies with relatively low OH (and OD) concentrations tend to have higher viscosity, which allows the glass to achieve a higher virtual temperature when annealed. A higher virtual temperature favorably correlates with a lower coefficient of thermal expansion (CTE) value. As is known in the art, CTE is a material property of glass that indicates the degree to which a material expands (changes shape) when heated. Therefore, a lower CTE value favorably prevents the glass body from changing shape when exposed to different temperature environments, which is beneficial in lithography applications, as discussed above.

[0025] The uniformity of the glass body's composition (e.g., uniformity of OH and OD) is ultimately desired to achieve a uniform and low CTE of the glass. A uniform and low CTE value advantageously allows the glass body's shape to remain substantially constant when heated, which is necessary in EUV systems. As discussed above, undesirable or non-uniform heat within an EUV system can cause the glass bodies in the system to thermally expand or contract. However, a uniform glass body with a low CTE value is less susceptible to such expansion or contraction strain when heated.

[0026] Modifiers can be added to glass bodies to improve the expansion behavior of glass. However, it is known in the art that such modifiers reduce the homogeneity of glass, making it more difficult to produce homogeneous glass. Homogeneous glass is important not only with respect to the thermal expansion behavior of glass but also with respect to its abrasiveness. For example, the uniformity of TiO2 concentration throughout the glass body affects the abrasiveness of that glass body. In particular, a glass body having localized regions with different TiO2 concentrations will be abrasively polished as regions with different concentrations of TiO2 in the glass abrasive at different rates. Therefore, embodiments of the present disclosure also produce a glass body with a uniform concentration of TiO2 so that the glass is abrasively polished.

[0027] The uniform concentrations of OH and TiO2 in the glass bodies produced according to embodiments of this disclosure are achieved by using zero to very small amounts of halogen. Therefore, the resulting glass bodies also contain very low concentrations of halogen, which is in stark contrast to conventional processes. It is known in the art that, for example, glass bodies with low OH concentrations can be produced by etching and removing OH from glass using halogen. However, the inventors of this disclosure were able to produce such low OH concentrations without using halogen.

[0028] Another important characteristic of glass bodies in EUV systems is that their CTE is exactly equal to zero. This temperature is known as the zero-crossing temperature and is denoted as Tzc. Ideally, a glass body in an EUV system should have a Tzc value close to its temperature when exposed to the EUV light of the EUV system. When the Tzc value matches (or is close to) this temperature, the glass body experiences minimal expansion (and therefore minimal geometric distortion) during the operation of the EUV system.

[0029] It should also be noted that Tzc is directly related to the concentrations of OH and TiO2 in the glass substrate (within a typical hypothetical temperature range). Therefore, as the TiO2 concentration increases, Tzc also increases. However, since the OH concentration is inversely correlated with Tzc, as the OH concentration increases, Tzc decreases.

[0030] Referring to Figure 1, step 110 of process 100 includes the generation of soot particles. More specifically, step 110 includes forming the soot particles as loose soot particles and then collecting the loose soot particles. Figure 2A depicts a schematic diagram of system 200 for generating loose soot particles using a combustion process. As shown in Figure 2A, system 200 comprises a first reservoir 220 containing a silica precursor 224 and a second reservoir 230 containing a titania precursor 234. The first reservoir 220 includes an inlet 222 at or near the base of the reservoir for introducing a carrier gas such as nitrogen. The carrier gas forms a vapor stream having the silica precursor 224. Similarly, the second reservoir 230 includes an inlet 232 at or near the base of the reservoir for introducing a carrier gas such as nitrogen. The carrier gas in the second reservoir 230 forms a vapor stream having a titania precursor 234.

[0031] Silica precursor 224 may include, for example, SiCl4 and / or octamethylcyclotetrasiloxane (OMCTS). Titania precursor 234 may include, for example, TiCl4 or titanium isopropoxide (TPT) (titanium tetraisopropoxide (TTIP), tetraisopropyl titanate (TIPT)).

[0032] To prevent saturation of the silica vapor flow and titania vapor flow, a bypass flow of carrier gas is also introduced into system 200 at inlets 226 and 236. The silica vapor flow then enters manifold 248 through distribution system 242, and the titania vapor flow enters manifold 248 through distribution system 244.

[0033] Subsequently, the silica vapor stream and the titania vapor stream are mixed in the manifold 248 to form a mixture of the two streams. As further shown in Figure 2A, the mixture of the two streams flows into the reaction chamber 264. More specifically, the mixture of the two streams enters the burner 254, which is mounted on top of the reaction chamber 264, via the fume line 252. The two streams further merge with the fuel / oxygen mixture in the burner 254 to burn and oxidize the mixture. The fuel may be natural gas. The oxidation and combustion of the mixture form loose soot particles 260, which are cooled and directed into the reaction chamber 264. The soot particles 260 contain silicon dioxide and titanium dioxide. More specifically, the silicon dioxide and titanium dioxide in the particles mix at the atomic level to form Si-O-Ti bonds.

[0034] In some embodiments, the soot particles 260 are directed upward through the tube 270 rather than downward into the collection chamber 264. The tube 270 can be a quartz tube that carries the soot particles 260 in the vapor stream to one or more filter bags 272. The soot particles 260 are removed from the vapor stream by the filter bags 272 and then deposited within one or more collection chambers 264'. For example, the soot particles 260 fall downward from the filter bags 272 and enter the collection chamber 264'. To prevent excessive accumulation of the soot particles 260 on the bags, N2 pulses can be applied periodically to the filter bags 272. In some embodiments, the collection chamber 264' is a stainless - steel hopper. Thereafter, the soot particles 260 can be further collected from the collection chamber 264' and deposited within the barrel, where the soot particles 260 can be stored until further use.

[0035] The generated soot particles 260 are spherical and have a substantially uniform distribution of SiO2 and TiO2 within the particles. The size of each soot particle 260 can vary depending on the state of the burner 254, but generally, the soot particles 260 have an average diameter of from about 20 nm to about 500 nm, or from 50 nm to about 400 nm, or from 60 nm to about 300 nm, or from 50 nm to about 100 nm.

[0036] The soot particles 260 can be cooled to about 200 °C or less, or about 175 °C or less, or about 150 °C or less, or about 125 °C or less, or about 100 °C or less, or about 75 °C or less, or about 50 °C or less, or about 25 °C or less, or about 20 °C or less before reaching the collection chambers 264, 264'.

[0037] Referring again to FIG. 1, in step 120 of process 100, the soot particles 260 are removed from the reaction chamber 264 and / or the collection chamber 264' and deposited in the mold to about 0.50 g / cm 3 or more, or about 0.55 g / cm 3 or more, or about 0.60 g / cm 3 or more, or about 0.65 g / cm 3 or more, or about 0.70 g / cm3 Above, or approximately 0.75 g / cm³ 3 Above, or approximately 0.80 g / cm³ 3 Above, or approximately 0.85 g / cm³ 3 This forms a pressurized and molded soot body having the above density. In addition to or instead of this, the molded soot body may have a density of approximately 1.50 g / cm³. 3 The following, or approximately 1.40 g / cm³ 3 The following, or approximately 1.30 g / cm³ 3 The following, or approximately 1.20 g / cm³ 3 The following, or approximately 1.15 g / cm³ 3 The following, or approximately 1.10 g / cm³ 3 The following, or approximately 1.00 g / cm³ 3 The following, or approximately 0.95 g / cm³ 3 The following, or approximately 0.90 g / cm³ 3 The following, or approximately 0.85 g / cm³ 3 The following, or approximately 0.80 g / cm³ 3 The following, or approximately 0.75 g / cm³ 3 The following, or approximately 0.70 g / cm³ 3 It has the following density: In the embodiment, the molded soot body is approximately 0.50 g / cm³. 3 ~Approx. 1.50g / cm 3 , or approximately 0.60 g / cm³ 3 ~Approx. 1.40g / cm 3 , or approximately 0.80 g / cm³ 3 ~Approx. 1.30g / cm 3 , or approximately 0.90 g / cm³ 3 ~Approx. 1.00g / cm 3 , or approximately 0.80 g / cm³ 3 ~Approx. 1.50g / cm 3 , or approximately 0.80 g / cm³ 3 ~Approx. 1.20g / cm 3 , or approximately 0.80 g / cm³ 3 ~Approx. 0.90g / cm 3It has a density of . The molded soot body is formed such that any density variation in any part of the body is less than or equal to about 5%, or less than or equal to about 4%, or less than or equal to about 3%, or less than or equal to about 2%, or less than or equal to about 1%, or less than or equal to about 0.75%, or less than or equal to about 0.50%, or less than or equal to about 0.25%, or less than or equal to about 0.20%, or less than or equal to about 0.15%, or less than or equal to about 0.10%, or less than or equal to about 0.05%, or less than or equal to about 0.02%, or less than or equal to about 0.01%, or less than or equal to about 0.00%. Figure 2B shows an exemplary cylindrical molded soot body, and Figure 2C shows an exemplary rectangular molded soot body, but the molded soot body may include other shapes other than those specifically described herein. As shown in Figures 2B and 2C, the molded soot body has a length L and a height H. Note that length L is also the diameter of the cylinder in Figure 2B.

[0038] In some embodiments, the body length L may be approximately 20 mm to approximately 1300 mm, or approximately 40 mm to approximately 1200 mm, or approximately 60 mm to approximately 1000 mm, or approximately 80 mm to approximately 800 mm, or approximately 100 mm to approximately 60 mm, or approximately 20 mm to approximately 40 mm. Furthermore, in some embodiments, the body height H is approximately 50 mm to approximately 500 mm, or approximately 60 mm to approximately 400 mm, or approximately 80 mm to approximately 200 mm, or approximately 100 mm to approximately 200 mm, or approximately 250 mm to approximately 500 mm, or approximately 250 mm to approximately 400 mm, or approximately 250 mm to approximately 300 mm, or approximately 200 mm to approximately 500 mm, or approximately 200 mm to approximately 400 mm, or approximately 200 mm to approximately 300 mm. However, it should be noted that the body length L and height H can vary and are not limited by the embodiments disclosed herein. Furthermore, it should be noted that in some embodiments, the length L of the body is longer than the height H, while in other embodiments, the height H is longer than the length L.

[0039] Referencing process 100 again, the formed soot body is then fixed to the glass body in step 130. After fixing, the body is remelted in step 140 and then annealed in step 150 to relieve any internal stress within the body and reduce the Tf fluctuations within the body, as well as lower the Tf within the body. The relieved internal stress allows for higher quality cutting and machining of the body, such as slicing the body into multiple slices. In some embodiments, the body is annealed for a duration of about 100 hours or more, or about 200 hours or more, or about 250 hours or more. The maximum annealing temperature may be about 750°C to about 1200°C, or about 800°C to about 1100°C, or about 900°C to about 1000°C. Once the annealing step is complete, the body may be subjected to subsequent finishing steps such as shaping, grinding, polishing, and / or slicing.

[0040] In the traditional bonding process (in step 130 of process 100), the molded soot body is placed in a bonding furnace and heated to dry the body. In particular, the conventional bonding process involves drying the soot body with a halogenated gas (e.g., a chlorine-containing gas) while heating the soot body. The soot body is then heated to a maximum temperature of approximately 1500°C under an inert gas atmosphere to completely bond the soot body to the glass body.

[0041] In embodiments disclosed herein, aspects of the disclosure include fixing the molded soot body without exposing the soot to halides during the fixing step 130. In particular, the fixing processes in Figures 3 to 5 (as discussed below) each fix the soot body without intentionally added halides (i.e., zero). The process in Figure 6 removes water with minimal addition of halides along with oxygen to minimize the effect of halides on TiO2. Thus, the resulting glass body contains little to no halides (such as chlorine, fluoride, and bromine) and adversely affects the heterogeneity of the glass. As is known in the art, the presence of halides can cause undesirable reactions with TiO2 in the glass. For example, chlorine and TiO2 react to produce titanium chloride and oxychlorides (e.g., titanium tetrachloride TiCl4, titanium trichloride TiCl3, titanium dichloride TiCl2), which are in the gas phase and can therefore move to different locations within the glass body. Titanium chloride can move Ti within the glass body, so the Ti is not evenly distributed and is not uniform throughout the glass body. Instead, the resulting glass body may contain certain locations with relatively high concentrations of Ti. The higher levels of Ti in these locations cause the resulting glass body to be unevenly polished. Therefore, embodiments of the present disclosure fix soot with minimal amounts of halide, or avoid any intentionally added halides.

[0042] Figure 3 depicts a first exemplary embodiment of the fixation step of process 100. More specifically, in some embodiments, step 130 of process 100 includes a step of process 300. As shown in Figure 3, process 300 includes actively drying (e.g., dehydrating) the molded soot body with carbon monoxide (CO) while fixing the soot. In particular, process 300 includes actively drying the molded soot body with CO to reduce the total concentration of OH and OD in the fixed glass body. Process 300 includes actively drying the molded soot body with CO to produce a glass body having uniform concentrations of OH and OD throughout.

[0043] Process 300 is carried out in a substantially halogen-free atmosphere. As used herein, “substantially halogen-free” means that halogens (e.g., chlorine, fluorine, bromine) are not intentionally added to the soot, either in elemental form or as halogen-containing compounds. It should be understood that the vitreous body may inadvertently contain small amounts of halogen due to contamination.

[0044] The mechanism for drying the soot using the steps of process 300 produces protium H2 (or deuterium D2) and CO2 based on the reaction between CO and OH (or OD). Step 310 of process 300 includes flowing a CO-containing gas through a solidification furnace to dry (e.g., dehydrate) the formed soot. The gas may contain other components in addition to CO, such as one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The gas contains about 0.5% to about 10% by weight of CO, or about 1% to about 8% by weight of CO, or about 2% to about 6% by weight of CO, or about 2% to about 4% by weight of CO. The drying in step 310 may be carried out over a period ranging from about 1 hour to about 200 hours, or about 5 hours to about 100 hours, or about 10 hours to about 50 hours.

[0045] Unless otherwise specified, the drying steps disclosed herein are carried out in an atmosphere in which gas(s) flow continuously over or "pass through" the soot body.

[0046] The drying in step 310 removes any OH and / or OD from the soot by heating the glass and reacting these molecules with CO gas to form CO2 and H2 (or D2). It should be noted that a side effect of using CO to dry the soot is that some of the TiO2 in the soot is reduced to TiO and Ti2O3. In some embodiments, the soot can be doped with at least one of OH and OD before drying in step 310 to achieve a predetermined or desired concentration of OH and / or OD in the resulting glass and to improve the homogeneity of these molecules in the resulting glass.

[0047] In step 320, the CO gas can be purged from the sintering furnace and the glass soot by passing an inert gas (e.g., helium, argon, nitrogen, neon) through the sintering furnace. In embodiments, the inert gas is helium gas. In step 330, oxygen gas (O2) is passed through the sintering furnace. The O2-containing gas may further contain one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The O2-containing gas should not contain water, or should be essentially water-free. If trace amounts of water are present in the O2-containing atmosphere, the soot will absorb the water during the sintering step, resulting in an increase in the OH concentration of the glass at or near the edges of the sintered glass.

[0048] The O2-containing gas contains approximately 0.5% to 5% by weight of O2, or approximately 1% to 4% by weight of O2, or approximately 1% to 3% by weight of O2. The oxidation step (step 330) can be carried out over a period ranging from approximately 30 minutes to approximately 5 hours, or approximately 30 minutes to approximately 2 hours, or approximately 30 minutes to approximately 1 hour. The O2 gas oxidizes the titanium species (Ti, TiO, Ti2O3) in the soot, and thus forms titania (TiO2) again. It should be noted that the oxidation of the titanium species occurs while the soot is still porous (before the soot is completely densified). Furthermore, the O2 gas ensures the complete conversion of CO to CO2 and repairs any damage to the soot caused by CO drying.

[0049] Unless otherwise specified, the oxidation steps disclosed herein are carried out in an atmosphere in which a gas(s) flows continuously over or "passes through" the soot.

[0050] During steps 310–330, the densification furnace is heated to a first temperature (T1) of approximately 900°C–1300°C, or approximately 950°C–1250°C, or approximately 1000°C–1200°C, or approximately 1050°C–1150°C, or approximately 1100°C–1200°C. In some embodiments, the drying in step 310 is carried out at a different temperature than the oxidation in step 330. As described above, steps 310–330 are carried out before the soot is completely densified and while the pores in the glass are open. The open porosity of the soot allows for more effective drying of the glass, as well as the removal of water, OH, and OD groups by CO-containing gas. In step 340, the temperature of the densification furnace is increased to densify the soot. In particular, the temperature is increased from a first temperature (T1) to a second temperature (T2) to completely densify the glass and close any open pores in the glass. The second temperature is approximately 1100°C to 1500°C, or approximately 1150°C to 1450°C, or approximately 1200°C to 1400°C, or approximately 1225°C to 1350°C, or approximately 1225°C to 1300°C, or approximately 1250°C to 1300°C, or approximately 1250°C to 1275°C. The second temperature is higher than the first temperature. While heating the soot body at the second temperature, an inert gas (e.g., helium, argon, nitrogen, neon) may be flowed through the densifying furnace. In some embodiments, heating the soot body is carried out in a vacuum.

[0051] The densification in step 340 can be carried out over a period ranging from approximately 4 to 20 hours, or from approximately 5 to 15 hours, or from approximately 5 to 10 hours. Therefore, the soot can be heated at a second temperature during these periods.

[0052] It should be noted that during steps 310–330 of process 300, the OH (and OD) in the soot was reduced and / or removed. In particular, the OH (and OD) in the soot was converted to protium H2 (or deuterium D2) and CO2 by CO drying. The reduction and / or removal of OH (and OD) allows the temperature of the settling furnace to be increased rapidly and quickly from the first temperature to the second temperature, while mitigating concerns about OH non-uniformity. In the case of larger amounts of OH (or OD), the glass is more prone to non-uniformity when exposed to such a rapid rate of temperature increase during settling. The rapid rate of temperature increase causes the radially outer portion of the soot to sinter first (and therefore for a longer period) compared with the radially inner portion of the soot. This can be problematic in soot containing larger amounts of OH (or OD) because sintering causes the soot to lose OH (or OD) molecules. Therefore, the radially outer portion of the soot body loses more OH (or OD) molecules than the radially inner portion, resulting in a heterogeneous glass body. This problem is greatly mitigated when the soot body contains low to zero concentrations of OH (or OD).

[0053] In the embodiment, the temperature of the fixing furnace increases from a first temperature (T1) to a second temperature (T2) (during step 340) at a rate of approximately 5°C / hour or more, or approximately 8°C / hour or more, or approximately 10°C / hour or more, or approximately 12°C / hour or more, or approximately 15°C / hour or more, or approximately 20°C / hour or more, or approximately 25°C / hour or more, or approximately 30°C / hour or more, or approximately 35°C / hour or more, or approximately 40°C / hour or more, or approximately 45°C / hour or more, or approximately 50°C / hour or more. In addition to or instead of this, the temperature of the fixing furnace is increased from the first temperature to the second temperature (during step 340) at a rate of about 60°C / hour or less, or about 55°C / hour or less, or about 50°C / hour or less, or about 45°C / hour or less, or about 40°C / hour or less, or about 35°C / hour or less, or about 30°C / hour or less, or about 25°C / hour or less, or about 20°C / hour or less, or about 15°C / hour or less, or about 12°C / hour or less, or about 10°C / hour or less, or about 8°C / hour or less. In the embodiment, the temperature increase is at a rate of about 5°C / hour to about 60°C / hour, or about 8°C / hour to about 55°C / hour.

[0054] Figure 4 depicts a second exemplary embodiment of the fixing step of process 100. More specifically, in some embodiments, step 130 of process 100 includes a step of process 400. As shown in Figure 4, process 400 includes drying (e.g., dehydrating) the soot formed in the graphite furnace. Similar to process 300 described above, the steps of process 400 are also carried out in a substantially halogen-free atmosphere. The mechanism for drying the soot using the steps of process 400 is based on the reaction between C in the graphite furnace and O2 gas or CO2 gas to dry the glass and produce CO, which reacts with OH (or OD) in the glass to produce protium H2 (or deuterium D2) and CO2.

[0055] Step 410 of process 400 includes flowing an O2-containing gas and / or a CO2-containing gas through the solidification furnace to dry (e.g., dehydrate) the soot. The gas may contain other components in addition to O2 and / or CO2, such as one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The gas contains about 0.5% to about 10% by weight of O2, or about 1% to about 8% by weight of O2, or about 2% to about 6% by weight of O2, or about 2% to about 4% by weight of O2. In addition to or instead of this, the gas contains about 0.5% to about 10% by weight of CO2, or about 1% to about 8% by weight of CO2, or about 2% to about 6% by weight of CO2, or about 2% to about 4% by weight of CO2. The drying in step 410 can be carried out over a period ranging from approximately 1 hour to approximately 200 hours, or from approximately 5 hours to approximately 100 hours, or from approximately 10 hours to approximately 50 hours.

[0056] O2 in the O2-containing gas and / or CO2 in the CO2-containing gas react with C in the graphite furnace (during step 410) to produce CO, which dries the soot as discussed above with reference to process 300. In particular, the drying in step 410 removes any OH and / or OD from the soot by heating the soot and reacting these molecules with the produced CO to form CO2. In some embodiments, the soot body may be doped with at least one of OH and OD before drying in step 410 to achieve a predetermined or desired concentration of OH and / or OD in the resulting glass body and to improve the homogeneity of these molecules in the resulting glass body.

[0057] It should be noted that even without the addition of O2-containing or CO2-containing gas, the OH groups in soot will produce H2O or D2O when heated. These waters (H2O and D2O) react with C in the graphite furnace to produce CO, which helps to dry the soot as described above. However, to completely dry the soot, the addition of O2-containing gas and / or CO2-containing gas is most likely necessary.

[0058] In step 420, the CO gas can be purged from the slag furnace and the soot by passing an inert gas (e.g., helium, argon, nitrogen, neon) through the slag furnace. In embodiments, the inert gas is helium gas.

[0059] In contrast to process 300, process 400 does not involve an oxidation step with an O2-containing gas, as this would react with carbon in the graphite furnace and destroy the furnace. Therefore, since the titanium species (Ti, TiO, Ti2O3) in the soot are not oxidized by the O2-containing gas, the resulting glass body will contain a reduced amount of titania (TiO2).

[0060] During steps 410–420, the densification furnace is heated to a first temperature (T1), as discussed above. Steps 410–420 are carried out before the soot is completely densified and while the pores in the soot are open. The open porosity of the soot allows for more effective drying of the soot, as well as the removal of water, OH, and OD groups by the resulting CO-containing gas. In step 430, the temperature of the densification furnace is increased to densify the soot. In particular, as discussed above, the temperature is increased from the first temperature (T1) to a second temperature (T2) to completely densify the soot and close any open pores in the soot. While heating the soot at the second temperature, an inert gas (e.g., helium, argon, nitrogen, neon) may flow through the densification furnace or under vacuum.

[0061] The densification in step 430 can be carried out over a period ranging from approximately 4 to 20 hours, or from approximately 5 to 15 hours, or from approximately 5 to 10 hours. Thus, the soot can be heated at a second temperature during these periods.

[0062] It should be noted that during steps 410–420 of process 400, OH (and OD) in the soot was reduced and / or removed. In particular, the OH (and OD) in the soot was converted to protium H2 (or deuterium D2) and CO2 by CO drying. Due to the reduction and / or removal of OH (and OD), the temperature of the slag furnace can be rapidly increased from the first temperature to the second temperature at the fast rate considered above with reference to process 300 (e.g., about 5°C / hour to about 60°C / hour).

[0063] Figure 5 depicts a third exemplary embodiment of the fixing step of process 100. More specifically, in some embodiments, step 130 of process 100 includes a step of process 500. As shown in Figure 5, process 500 includes drying (e.g., dehydrating) the molded soot containing carbon in order to reduce the total concentration of OH and OD in the fixed glass body. Similar to process 300 above, the steps of process 500 are also carried out in a substantially halogen-free atmosphere. The mechanism for drying the soot using the steps of process 400 is based on the reaction between carbon in the molded soot and O2 gas or CO2 gas to dry the soot and react with OH (or OD) in the glass to produce protium H2 (or deuterium D2) and CO2.

[0064] In process 500, the soot particles 260 are first mixed with carbon powder (as discussed above with reference to Figure 2). In some embodiments, the soot particles 260 are mixed with carbon powder in a reaction chamber 264. The resulting soot particles may contain about 1% to 10% by weight of carbon, or about 2% to 8% by weight of carbon, or about 1% to 5% by weight of carbon. These soot particles are then formed into soot bodies as discussed above. The formed carbon-containing soot bodies are then fixed using the steps of process 500.

[0065] Step 510 of process 500 includes flowing an O2-containing gas and / or a CO2-containing gas through the solidification furnace to dry (e.g., dehydrate) the soot. The gas may contain other components in addition to O2 and / or CO2, such as one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). In some embodiments, the gas contains about 0.5% to about 10% by weight of O2, or about 1% to about 8% by weight of O2, or about 2% to about 6% by weight of O2, or about 2% to about 4% by weight of O2. In addition to or instead of this, the gas may, in some embodiments, contain about 0.5% to about 10% by weight of CO2, or about 1% to about 8% by weight of CO2, or about 2% to about 6% by weight of CO2, or about 2% to about 4% by weight of CO2. The drying in step 510 can be carried out over a period ranging from approximately 1 hour to approximately 200 hours, or from approximately 5 hours to approximately 100 hours, or from approximately 10 hours to approximately 50 hours.

[0066] O2 in the O2-containing gas and / or CO2 in the CO2-containing gas react with the carbon in the molded soot body (during step 510) to produce CO, which dries the soot as discussed above with reference to process 300. In particular, the drying in step 510 removes any OH and / or OD in the glass by heating the soot and reacting these molecules with the produced CO to form CO2. In some embodiments, the soot body may be doped with at least one of OH and OD before drying in step 510 to achieve a predetermined or desired concentration of OH and / or OD in the resulting glass body and to improve the homogeneity of these molecules in the resulting glass body.

[0067] In step 520, the CO gas can be purged from the slag furnace and the soot by passing an inert gas (e.g., helium, argon, nitrogen, neon) through the slag furnace. In embodiments, the inert gas is helium gas.

[0068] In step 530, oxygen gas (O2) is flowed through the sintering furnace. The O2-containing gas may further contain one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The O2-containing gas should be water-free or essentially water-free. If trace amounts of water are present in the O2-containing atmosphere, the soot will absorb the water during the sintering step, resulting in an increase in the OH concentration of the glass at or near the edges of the sintered glass.

[0069] The O2-containing gas contains approximately 0.5% to 5% by weight of O2, or approximately 1% to 4% by weight of O2, or approximately 1% to 3% by weight of O2. The oxidation step (step 530) can be carried out over a period ranging from approximately 30 minutes to approximately 5 hours, or approximately 30 minutes to approximately 2 hours, or approximately 30 minutes to approximately 1 hour. The O2 gas oxidizes the titanium species (Ti, TiO, Ti2O3) in the soot, and thus forms titania (TiO2) again. It should be noted that the oxidation of the titanium species occurs while the soot is still porous (before the soot is completely densified). Furthermore, the O2 gas ensures the complete conversion of CO to CO2 and repairs any damage to the soot caused by CO drying.

[0070] During steps 510–530, the densification furnace is heated to a first temperature (T1), as discussed above. Steps 510–530 are carried out before the soot is completely densified and while the pores in the soot are open. The open porosity of the soot allows for more effective drying of the soot, as well as removal of water, OH, and OD groups by the resulting CO-containing gas. In step 540, the temperature of the densification furnace is increased to densify the soot. In particular, as discussed above, the temperature is increased from the first temperature (T1) to a second temperature (T2) to completely densify the soot and close any open pores in the soot. While heating the soot at the second temperature, an inert gas (e.g., helium, argon, nitrogen, neon) may flow through the densification furnace or under vacuum.

[0071] The densification in step 540 can be carried out over a period ranging from approximately 4 to 20 hours, or from approximately 5 to 15 hours, or from approximately 5 to 10 hours. Therefore, the soot can be heated at a second temperature during these periods.

[0072] It should be noted that during steps 510–530 of process 500, OH (and OD) in the glass body was reduced and / or removed. In particular, the OH (and OD) in the glass body was converted to protium H2 (or deuterium D2) and CO2 by CO drying. Due to the reduction and / or removal of OH (and OD), the temperature of the solidification furnace can be rapidly increased from the first temperature to the second temperature at the fast rate considered above with reference to process 300 (e.g., about 5°C / hour to about 60°C / hour).

[0073] Figure 6 depicts a fourth exemplary embodiment of the fixing step of process 100. More specifically, in some embodiments, step 130 of process 100 includes a step of process 600. As shown in Figure 6, process 600 includes drying (e.g., dehydrating) the molded soot with halogens within a desired halogen-to-O2 ratio to produce a low-halogen level soot. The mechanism for drying the soot using the steps of process 600 is based on halogen drying and etching, but keeps the halogen at a sufficiently low level so as not to affect the CTE uniformity in the resulting glass body.

[0074] In step 610 of process 500, a halogen and O2-containing gas is flowed into the solidification furnace. The ratio (X) of the partial pressure of halogen in the gas to the partial pressure of O2 in the gas is given by the following formula: X = [partial pressure of halogens] 2 [Partial pressure of O2] Defined by, In the formula, the partial pressures of halogen and O2 are in units of atmospheric pressure (atm). Therefore, X is also in units of atm. X is approximately 5 × 10 to maintain the desired ratio of halogen and O2 (so that the halogen does not affect the uniformity of CTE in the glass).-6 The pressure should be approximately 1.0 atm. The low X value corresponds to reduced formation of titanium chloride (TiCl3), which minimizes the movement of TiO2 in the resulting glass body.

[0075] The preferred range for X is approximately 1 x 10 -6 atm ~ approximately 0.5 atm, or approximately 1 x 10 -6 atm ~ approximately 0.3 atm, or approximately 1 x 10⁻¹⁰ -6 atm ~ approximately 0.1 atm, or approximately 1 x 10⁻¹⁰ -5 atm ~ approximately 1.0 atm, or approximately 1 x 10 -5 atm ~ approximately 0.5 atm, or approximately 1 x 10 -5 atm ~ approximately 0.3 atm, or approximately 1 x 10⁻¹⁰ -5 atm ~ approximately 0.1 atm, or approximately 1 x 10⁻¹⁰ -4 atm ~ approximately 1.0 atm, or approximately 1 x 10 -4 atm ~ approximately 0.5 atm, or approximately 1 x 10 -4 atm ~ approximately 0.3 atm, or approximately 1 x 10⁻¹⁰ -4 atm ~ approximately 0.1 atm, or approximately 5 x 10 -5 atm ~ approximately 0.1 atm, or approximately 5 x 10 -5 The partial pressure is approximately 0.01 atm, or approximately 0.0015 atm to 0.5 atm, or approximately 0.0013 atm to 0.5 atm, or approximately 0.0015 atm to 0.01 atm, or approximately 0.0013 atm to 0.01 atm. X represents the loss of TiO2 in the glass body due to the presence of halogens. Therefore, in some embodiments, it is preferable to lower X to minimize TiO2 loss. Preferably, to produce a lower X value, the partial pressure of halogens in gas ([halogen]) is low and the partial pressure of O2 in gas ([O2]) is high.

[0076] In one exemplary embodiment, the partial pressure of chlorine in the gas is 0.00218 atm, and the partial pressure of O2 in the gas is 0.09071 atm, and therefore 5.2 x 10 -5Generate the X value in atm. In another example, the partial pressure of chlorine in the gas is 0.00109 atm, and the partial pressure of O2 in the gas is 0.09081 atm, therefore 1.31 × 10⁻¹⁰ -5 Generate the X value in atm. In another example, the partial pressure of chlorine in the gas is 0.07692 atm, and the partial pressure of O2 in the gas is 0.15385 atm, therefore 3.85 x 10 -2 Generate the X value in atm. In another example, the partial pressure of chlorine in the gas is 0.2 atm, and the partial pressure of O2 in the gas is 0.13333 atm, therefore 3.00 x 10 -1 Generate the X value in atm. In another example, the partial pressure of chlorine in the gas is 0.00171 atm, and the partial pressure of O2 in the gas is 0.28523 atm, therefore 1.03 × 10⁻¹⁰ -5 Generate the X value for atm.

[0077] The halogen and O2-containing gas may further contain one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The halogen and O2-containing gas should be water-free or essentially water-free. The halogen etches and dries (e.g., dehydrates) the soot. The O2 gas oxidizes the titanium species (Ti, TiO, Ti2O3) in the soot, thus forming titania (TiO2). Note that the oxidation of the titanium species occurs while the soot is still porous (before the soot is completely densified).

[0078] In step 620, the halogen and O2-containing gases can be purged from the slag furnace and soot by, for example, passing an inert gas (e.g., helium, argon, nitrogen, neon) through the slag furnace. In embodiments, the inert gas is helium gas.

[0079] During steps 610–620, the densification furnace is heated to a first temperature (T1), as discussed above. Steps 610–620 are carried out before the soot is completely densified and while the pores in the soot are open. The open porosity of the soot allows the halogen to dry the soot more effectively. In step 630, the temperature of the densification furnace is increased to densify the soot. In particular, as discussed above, the temperature is increased from the first temperature (T1) to a second temperature (T2) to completely densify the soot and close any open pores in the soot. While heating the soot at the second temperature, an inert gas (e.g., helium, argon, nitrogen, neon) may flow through the densification furnace or in a vacuum.

[0080] The densification in step 630 can be carried out over a period ranging from approximately 4 to 20 hours, or from approximately 5 to 15 hours, or from approximately 5 to 10 hours. Thus, the soot body can be heated at a second temperature during these periods.

[0081] It should be noted that during steps 610-620 of process 500, OH (and OD) in the glass body is reduced and / or removed. In particular, halogens in halogen-containing gases react with OH or OD to form HX or DX, respectively, where X can be a fluorine atom, a chlorine atom, or a bromine atom, depending on the halogen used. Due to the reduction and / or removal of OH (and OD), the temperature of the solidification furnace can be rapidly increased from the first temperature to the second temperature at the fast rate considered above with reference to process 300 (e.g., about 5°C / hour to about 60°C / hour).

[0082] Referring again to Figure 1, process 100 includes annealing the glass body after the fixing step disclosed above. According to embodiments disclosed herein, the annealing step 150 of process 100 may include a post-formation fixation process. As used herein, “fixation” means imposing a specific temperature or thermal history on the glass through appropriate heat treatment. In embodiments disclosed herein, the fixation process is performed at a rate of about 5°C / second or more, or about 10°C / second or more, or about 15°C / second or more, or about 20°C / second or more, or about 25°C / second or more, or about 30°C / second or more, to a first fixation temperature (T 1f ) to the second fixation temperature (T 2f ) includes “rapid cooling” of the glass. In some embodiments, the fixtureation process is performed when the glass is 10 13 The glass is heated to a first fixation temperature (T) so that it has a viscosity of less than poise. 1f ) to heat, and then the glass to the first fixture temperature (T 1f Equilibrate the glass at a predetermined temperature (T) for a specified period, and then, afterwards, bring the glass to a second fixation temperature (T) below the strain point of the glass. 2f This includes rapidly cooling the glass to a first fixture temperature (T). In this embodiment, the glass is cooled to a first fixture temperature (T). 1f ) is heated to approximately 10 9 Poise ~ about 10 13 Poise, or about 10 9 Poise ~ about 10 12 Poise, or about 10 9 Poise ~ about 10 11 Poise, or about 10 9 Poise ~ about 10 10 It has a poise viscosity, followed by an equilibration step and a quenching step.

[0083] In some embodiments, the first activation temperature (T 1f ) is above the annealing point of the glass. For example, the first fixation temperature (T 1fThe second activation temperature (T) is approximately 825°C or higher, or approximately 850°C or higher, or approximately 875°C or higher, or approximately 900°C or higher, or approximately 925°C or higher, or approximately 950°C or higher, or approximately 975°C or higher, or approximately 1000°C or higher, or approximately 1025°C or higher, or approximately 1050°C or higher, or approximately 1075°C or higher, or approximately 1100°C or higher, or approximately 1125°C or higher, or approximately 1150°C or higher. Furthermore, in some embodiments, the second activation temperature (T) 2f The temperature is approximately room temperature (for example, about 25°C). In the embodiment, the second activation temperature (T 2f The temperature is either approximately 40°C or more below the isothermal holding temperature of the glass, or within the range of approximately 25°C to 600°C, or approximately 100°C to 500°C. The glass has a first fixture temperature (T 1f The vitrified glass can be equilibrated over a period of approximately 12 hours or more, or approximately 16 hours or more, or approximately 20 hours or more, or approximately 24 hours or more, or approximately 30 hours or more. Due to the disclosed fixtureation process, the resulting glass body has a high level of intrinsic damage resistance.

[0084] As discussed above, the glass bodies produced in the embodiments disclosed herein contain a uniform concentration of OH (and OD). Furthermore, in the embodiments, the produced glass bodies contain a relatively low concentration of OH (and OD). For the purposes of this disclosure, the OH (and OD) concentration was measured by segmenting the produced glass body into multiple segments and measuring the OH (and OD) concentration of each segment, as discussed below with reference to Figures 7A-7C. Figure 7A shows the glass body 10 produced by process 100 of Figure 1. Thus, body 10 is the body resulting after the annealing step 150 of process 100. Body 10 may be an ingot or substrate to which one or more layers are applied during downstream processing.

[0085] As discussed above, body 10 is TiO2-SiO2 glass. The SiO2 concentration in body 10 may be approximately 80% by weight or more, or approximately 85% by weight or more, or approximately 90% by weight or more, or approximately 92% by weight or more, or approximately 95% by weight or more, or approximately 97% by weight or more, or approximately 98% by weight or more, or approximately 99% by weight or more, or approximately 85% by weight to approximately 97% by weight, or approximately 90% by weight to approximately 95% by weight. The TiO2 concentration in body 10 may be approximately 1.0 wt% to approximately 15.0 wt%, or approximately 6.0 wt% to approximately 12.0 wt%, or approximately 6.0 wt% to approximately 8.5 wt%, or approximately 6.0 wt% to approximately 8.0 wt%, or approximately 6.0 wt% to approximately 7.5 wt%, or approximately 6.0 wt% to approximately 7.0 wt%, or approximately 6.0 wt% to approximately 6.8 wt%, or approximately 6.0 wt% to approximately 6.5 wt%, or approximately 6.5 wt% to approximately 7.5 wt%, or approximately 6.5 wt% to approximately 7.0 wt%.

[0086] Body 10 has a length L', a width W', and a height H', as shown in Figure 7A. In some embodiments, the length L' and width W are each longer than the height H'. For example, the length L' and width W' may each be about 500 mm or less, or about 450 mm or less, or about 400 mm or less, or about 350 mm or less, or about 300 mm or less, or about 250 mm or less, or about 200 mm or less, or about 150 mm or less, or about 100 mm or less, or about 75 mm or less, or about 50 mm or less, or about 25 mm or less, or about 20 mm or less, or about 15 mm or less. In addition to or instead of the above, the length L' and width W' of the glass body 10 are, respectively, about 15 mm or more, or about 20 mm or more, or about 25 mm or more, or about 50 mm or more, or about 75 mm or more, or about 100 mm or more, or about 150 mm or more, or about 200 mm or more, or about 250 mm or more, or about 300 mm or more, or about 350 mm or more, or about 400 mm or more, or about 450 mm or more, or about 500 mm or more. In some embodiments, both the length L' and width W' are about 150 mm, or about 152 mm, or about 179 mm. However, in some embodiments, it is also intended that the length L' may be different from the width.

[0087] Furthermore, the height H' may be shorter than each of the length L' and width W'. In some embodiments, the height H' is about 400 mm or less, or about 350 mm or less, or about 300 mm or less, or about 250 mm or less, or about 200 mm or less, or about 150 mm or less, or about 100 mm or less, or about 75 mm or less, or about 50 mm or less, or about 25 mm or less, or about 20 mm or less, or about 15 mm or less, or about 10 mm or less, or about 5 mm or less. In addition to or instead of the above, the height H' is approximately 5 mm or more, or approximately 10 mm or more, or approximately 15 mm or more, or approximately 20 mm or more, or approximately 25 mm or more, or approximately 50 mm or more, or approximately 75 mm or more, or approximately 100 mm or more, or approximately 150 mm or more, or approximately 200 mm or more, or approximately 250 mm or more, or approximately 300 mm or more, or approximately 350 mm or more, or approximately 400 mm or more. In some embodiments, the height H' is approximately 63 mm, or approximately 150 mm, or approximately 152 mm.

[0088] As discussed above, body 10 can be sliced ​​into multiple samples. Figure 7A shows the minimum dimensions of body 10 (i.e., characteristic length L). c An exemplary sample 15 of the body 10 is shown, forming the lower portion of the body along the height H'. Each sample 15 may be considered a body, substrate, or wafer. In the embodiment of Figure 7A, the height H' is shorter than each of the length L' and width W', such that the height H' is the minimum dimension. Thus, the height h' of the sample 15 extends along the height H' of the body 10. In the embodiment of Figure 7A, the body 10 includes multiple samples along its height H'. However, in other embodiments, it is also intended that one sample 15 extends along the entire height H' of the body 10 (or along the entire minimum dimension of the body if the minimum dimension is not height H'). In these embodiments, the body 10 includes only one sample 15, such that one sample 15 forms the entire body 10.

[0089] Figure 7A depicts the body 10 and sample 15 as square components with flat surfaces; however, in embodiments, the body 10 and / or sample 15 may also include other shapes. For example, the external shape of the body 10 and / or sample 15 may be circular, elliptical, or asymmetrical. Furthermore, the body 10 and / or sample 15 may be curved to form a concave or convex structure. In one exemplary embodiment, the body 10 is formed from a single sample 15 (so that the single sample 15 extends across the entire length, width, and height of the body 10), and the body 10 has a concave structure. The sample 15 may be a reticle, a photomask, a mirror, and / or a photomask holder.

[0090] Each sample 15 has substantially uniform concentrations of OH, OD, and TiO2 across the length and width of the sample. To determine the uniformity of the sample throughout, each sample is divided into segments across the length and width of the sample. For example, Figure 7B shows sample 15 divided into segments 20 across the cross-sectional length L' and width W' of sample 15. The concentrations of one or more components (e.g., OH, OD, TiO2) can then be determined for each segment 20 to determine the uniformity of each of these components along sample 15. For example, to determine the uniformity of the OH concentration across the cross-section of sample 15, the concentration of OH can be measured for each segment 20. As will be further discussed below, the concentrations of one or more components are determined throughout the total thickness h' of each segment 20.

[0091] Figure 7B shows a segment 20 extending along the entire length L' and width W' of the sample 15, but it is also intended that the portion of the sample 15 containing the segment 20 may be less than the entire cross-sectional length L' and width W'. For example, as shown in Figure 7C, the sample 15 may include an outer peripheral edge 17 on which the segment 20 is not formed. Thus, the outer peripheral edge 17 may be the gap between the end of the segment 20 of the sample 15 and the outer edge. In embodiments, the outer peripheral edge may extend for a length L''' of about 2 mm to about 20 mm, or about 4 mm to about 16 mm, or about 5 mm to about 16 mm, or about 8 mm to about 14 mm, or about 10 mm to about 12 mm. In some embodiments, the length L''' is about 12.5 mm or about 12.7 mm.

[0092] Segment 20 can be an adjacent segment of sample 15 that spans a specific length and width (so that no gaps are formed between adjacent segments). As discussed above, this specific length and width (over which all segments 20 extend) can be less than or equal to the length L' and width W' of sample 15. In embodiments, segment 20 is an adjacent segment (over which all segments 20 extend) such that the length and width of sample 15 are, respectively, about 25 mm or more, or about 30 mm or more, or about 40 mm or more, or about 50 mm or more, or about 60 mm or more, or about 75 mm or more, or about 100 mm or more, or about 125 mm or more, or about 150 mm or more, or about 175 mm or more, or about 180 mm or more, or about 190 mm or more, or about 200 mm or more, or about 250 mm or more.

[0093] If sample 15 includes a flat surface, segment 20 is formed along the flat plane, as shown in Figure 7B. However, if sample 15 includes a concave or convex surface, segment 20 is formed along the curved surface of sample 15.

[0094] As shown in Figure 7B, each segment 20 has a length L'' and a width W'', each approximately 12.7 mm. However, in other embodiments, the length L'' may not be equal to the width W''. It should also be noted that in some embodiments, the length L'' and width W'' of segment 20 may be equal to the length L''' of the peripheral edge 17.

[0095] The height of each segment 20 is the height h' of the sample 15, as discussed above. Therefore, in this embodiment, the height h' is approximately 7.62 mm.

[0096] As discussed above, the concentration of one or more components can be determined within each segment 20. Therefore, for example, the concentration of OH can be determined for each adjacent segment 20 in the sample 15. If each segment 20 has a length and width of 12.7 mm, the concentrations of the components are determined at 12.7 mm intervals across the cross-section of the sample 15. For example, the concentration of OH is measured at 12.7 mm intervals across the cross-section of the sample 15.

[0097] The OH(OD) concentration in each segment 20 is measured using transmission Fourier transform infrared spectroscopy ("FTIR"). As used herein, "transmission" means that the OH or OD concentration is determined by directing light through the glass body to be measured (rather than using light reflected from the body to be measured to determine the OH or OD concentration). Thus, "transmission" requires a non-scattering surface. Once the sample 15 is loaded into the FTIR for measurement, beam alignment and background measurements may be performed first. The FTIR then measures the underlying absorption peak for OH or OD, thereby measuring the peak height relative to the background signal, which is a straight line between points surrounding the absorption peak. The absorption peak height is then divided by the thickness h' of the sample 15 to obtain the absorption coefficient β OH This is obtained. Then, the OH concentration is calculated using the following formula: C=β OH / ε×MW OH / D ガラス ×106 is used to derive the absorption coefficient β OH where C is the concentration of OH in ppm of a particular segment 20, and β OH is the absorption coefficient of the glass, ε is the molar absorptivity of OH for the absorption peak at a wavenumber of 3670 cm -1 , MW OH is the molecular weight of hydroxyl (g / mol), and D ガラス is the density of the glass (g / cm 3 ). Note that the same equation can be used to determine the OD concentration. The FTIR analysis disclosed above is further disclosed in K.M. Davis, et al, “Quantitative infrared spectroscopic measurement of hydroxyl concentration in silica glass,” J. Non-Crystalline Solids, 203 (1996) 27-36, which is incorporated herein by reference. As discussed above, the OH (or OD) concentration is measured for each segment 20 of the sample 15 and through the total thickness h’ of each segment 20. Thereafter, the measurement of the OH (or OD) concentration is repeated over all segments 20 of the sample 15.

[0098] One or more segments 20 may have a different OH (or OD) concentration than one or more other segments 20. However, in an embodiment, each segment 20 has a substantially the same OH (or OD) concentration regardless of where the segment is located on the substrate 10.

[0099] Furthermore, the average OH (or OD) concentration along the length L' and width' of sample 15 can be determined by averaging the OH (or OD) concentrations of the individual segments 20 together. According to embodiments disclosed herein, the average OH (and / or OD) concentration of the entire sample 15 can be in the range of about 0 ppm to about 100 ppm, or about 1 ppm to about 80 ppm, or about 2 ppm to about 60 ppm, or about 3 ppm to about 50 ppm, or about 4 ppm to about 40 ppm, or about 5 ppm to about 30 ppm, or about 1 ppm to about 25 ppm, or about 1 ppm to about 20 ppm, or about 1 ppm to about 15 ppm, or about 1 ppm to about 10 ppm, or about 1 ppm to about 8 ppm, or about 1 ppm to about 5 ppm. In some embodiments, the average OH (and / or OD) concentration of the entire sample 15 is approximately 10 ppm or less, or approximately 8 ppm or less, or approximately 6 ppm or less, or approximately 5 ppm or less, or approximately 4 ppm or less, or approximately 3 ppm or less, or approximately 2 ppm or less, or approximately 1 ppm or less.

[0100] In some specific embodiments, the maximum OH (and / or OD) concentration between segments 20 may be in the range of about 1 ppm to about 100 ppm, or about 2 ppm to about 80 ppm, or about 3 ppm to about 50 ppm, or about 10 ppm to about 40 ppm, or about 10 ppm to about 20 ppm, or about 3 ppm to about 20 ppm, or about 3 ppm to about 15 ppm, or about 3 ppm to about 10 ppm, or about 3 ppm to about 5 ppm. In some specific embodiments, the minimum OH (and / or OD) concentration between segments 20 may be about 5 ppm or less, or about 4 ppm or less, or about 3 ppm or less, or about 2 ppm or less, or about 1 ppm or less, or about 0 ppm.

[0101] The difference between the highest and lowest concentrations of OH (or OD) between different segments 20 is the peak-valley (PV) OH concentration. More specifically, segment 20 with the highest OH concentration is compared to segment 20 with the lowest OH concentration. The difference between the highest and lowest OH concentrations is then calculated. This difference between the highest and lowest concentrations in sample 15 is called the PV difference of concentration. A smaller PV difference indicates that the concentration is more uniform in a particular sample.

[0102] The PV difference of the OH (and / or OD) concentration of segment 20 in sample 15 may be approximately 60 ppm or less, or approximately 50 ppm or less, or approximately 40 ppm or less, or approximately 30 ppm or less, or approximately 20 ppm or less, or approximately 10 ppm or less, or approximately 9 ppm or less, or approximately 8 ppm or less, or approximately 7 ppm or less, or approximately 6 ppm or less, or approximately 5 ppm or less, or approximately 4 ppm or less, or approximately 3 ppm or less, or approximately 2 ppm or less, or approximately 1 ppm or less, or approximately 0 ppm or less, when generated in process 100. In the embodiment, the PV difference of the OH (and / or OD) concentration of segment 20 in sample 15 is within the range of approximately 0 ppm to approximately 60 ppm, or approximately 0 ppm to approximately 50 ppm, or approximately 0 ppm to approximately 40 ppm, or approximately 0 ppm to approximately 30 ppm, or approximately 0 ppm to approximately 20 ppm, or approximately 0 ppm to approximately 10 ppm, or approximately 1 ppm to approximately 30 ppm, or approximately 1 ppm to approximately 25 ppm, or approximately 1 ppm to approximately 20 ppm, or approximately 1 ppm to approximately 15 ppm, or approximately 1 ppm to approximately 5 ppm, or approximately 1 ppm to approximately 3 ppm, or approximately 3 ppm to approximately 10 ppm, or approximately 5 ppm to approximately 10 ppm.

[0103] As discussed above, the PV difference in OH concentration between segments 20 is very low, and therefore provides a homogeneous and uniform glass body 10. Due to such a low PV difference, the glass body 10 will maintain its shape in the EUV system. Furthermore, in the embodiments, the OH concentration between segments 20 is also very low. As discussed above, the lower OH concentration disclosed herein contributes to the production of a glass body with a lower CTE value. In the embodiments of this disclosure, such a uniform and low OH concentration was achieved with little to no use of halides.

[0104] The average concentration of TiO2 in segment 20, when produced by process 100 disclosed herein, may be about 1.0 wt% to about 15.0 wt%, or about 6.0 wt% to about 12.0 wt%, or about 6.0 wt% to about 8.5 wt%, or about 6.0 wt% to about 8.0 wt%, or about 6.0 wt% to about 7.5 wt%, or about 6.0 wt% to about 7.0 wt%, or about 6.0 wt% to about 7.0 wt%, or about 6.0 wt% to about 6.8 wt%, or about 6.0 wt% to about 6.5 wt%, or about 6.5 wt% to about 7.5 wt%, or about 6.5 wt% to about 7.0 wt%, as disclosed above.

[0105] Furthermore, the average Ti between the 20 segments 3+ The concentration, when produced by process 100 disclosed herein, is about 100 ppm or less, or about 90 ppm or less, or about 80 ppm or less, or about 70 ppm or less, or about 60 ppm or less, or about 50 ppm or less, or about 40 ppm or less, or about 30 ppm or less, or about 20 ppm or less, or about 15 ppm or less, or about 10 ppm or less, or about 5 ppm or less.

[0106] The PV difference of the TiO2 concentration of segment 20 in sample 15 may be about 0.0200% by weight or less, or about 0.01500% by weight or less, or about 0.0100% by weight or less, or about 0.0090% by weight or less, or about 0.0080% by weight or less, or about 0.0070% by weight or less, or about 0.0060% by weight or less, or about 0.0050% by weight or less, or about 0.0040% by weight or less, or about 0.0035% by weight or less, or about 0.0030% by weight or less, or about 0.0025% by weight or less, or about 0.0020% by weight or less, or about 0.0015% by weight or less, or about 0.0010% by weight or less, when produced by process 100 disclosed herein. In the embodiment, the PV difference of the TiO2 concentration in segment 20 is approximately 0.0010 wt% to approximately 0.0050 wt%, or approximately 0.0015 wt% to approximately 0.0045 wt%, or approximately 0.0020 wt% to approximately 0.0040 wt%, or approximately 0.0025 wt% to approximately 0.0035 wt%, or approximately 0.0030 wt% to approximately 0.0050 wt%, or approximately The PV difference of the TiO2 concentration in the glass body 10 is very low, and therefore the embodiments disclosed herein produce a homogeneous glass body 10 having not only a uniform OH concentration but also a uniform TiO2 concentration.

[0107] The TiO2 concentration in each segment 20 is calculated based on the measured refractive index of each segment 20. As is known in the art, the concentration of TiO2 in a glass body correlates with the refractive index of the glass body. Therefore, for the purposes of this disclosure, the refractive index is measured to determine the TiO2 concentration of the glass body disclosed herein. More specifically, an optical interferometer operating at a wavelength of 633 nm is used to measure the refractive index. Specifically, the optical interferometer is a Zygo Verifire HD from Zygo Corporation, having a resolution of 270 micron pixel size and operating at a wavelength of 633 nm. The optical interferometer is set up so that the pixels are square with a size of 270 microns × 270 microns, and each pixel extends through the total thickness h' of the sample 15. The refractive index is measured at each pixel in the segment 20, through the total thickness of the pixel. The refractive index measured for each pixel in the segment 20 is then averaged together to determine the average refractive index of each segment 20. The refractive index measurement is then repeated over all segments 20 of the sample 15.

[0108] Subsequently, the average TiO2 concentration of each segment 20 is determined based on the average refractive index of each segment 20 using the following relationship: 55 ppm RI = 0.0125%C Ti RI is the average refractive index of each segment 20, and C Ti This represents the average concentration (by weight) of TiO2 in each segment 20. Note that the above relationship assumes that the sole influence on the change in refractive index comes from TiO2.

[0109] Furthermore, the average CTE for each segment 20 is related to the following: 55 ppm RI=1 ppb / K CTE It is determined from the average refractive index of each segment 20 using RI is the average refractive index of each segment 20, and CTE is the average coefficient of thermal expansion (ppb / K) of each segment 20. It should be noted that the above relationship assumes that the only influence on the change in refractive index is from the CTE.

[0110] In addition to this, the Tzc of each segment 20 has the following relationship: ΔCTE / CTE slope = ΔTzc is determined from the CTE of each segment 20 using where ΔCTE is the deviation of the CTE (in ppb / K units) for a particular segment 20 compared to the average CTE of all segments 20, and CTE slope is the slope of the CTE of all segments 20 (in ppb / K 2 units) as a function of temperature, and ΔTzc is the deviation of the Tzc of a particular segment 20 compared to the average Tzc of all segments 20 (in °C). It should be noted that the above relationship assumes that the only influence on the change in Tzc is from the CTE.

[0111] The P-V difference in the refractive index of segment 20 across sample 15 is about 1x10 -4 or less, or about 5x10 -5 or less, or about 1x10 -5 or less, or about 5x10 -6 or less, or about 1x10 -6 or less, or about 5x10 -7 or less, or about 1x10 [[ID=...]] -4 ​​​​​​​​​​​​​​​​​​This is possible. The refractive index distribution within a glass substrate is an indicator of the TiO2 concentration distribution within that glass substrate. Therefore, a glass substrate with a smaller PV difference in refractive index will also have a smaller PV difference in TiO2. As discussed above, a smaller PV difference in TiO2 allows the glass substrate to be polished more uniformly.

[0112] Furthermore, when the glass body 10 is produced by process 100 as disclosed herein, it has ultra-low expansion properties that make it suitable for use in EUV lithography applications. In embodiments, the glass body 10 includes a CTE value at 20°C in the range of -45 ppb / K to +20 ppb / K, or a CTE value at 20°C in the range of -45 ppb / K to +20 ppb / K, or in any range limited by -45 ppb / K, -40 ppb / K, -35 ppb / K, -30 ppb / K, -25 ppb / K, -20 ppb / K, -15 ppb / K, -10 ppb / K, -5 ppb / K, 0 ppb / K, +5 ppb / K, +10 ppb / K, +15 ppb / K, +20 ppb / K, or any range limited by any two of these values ​​(e.g., -40 ppb / K to -25 ppb / K, -15 ppb / K to +15 ppb / K, etc.). Such ultra-low CTE values ​​at room temperature allow the shape of the glass body 10 to remain substantially constant during heating, whether formed on a mirror or photomask (such as a reflective mask) during the EUV lithography process.

[0113] In embodiments, the glass body 10, when produced by process 100 disclosed herein, includes a crossover temperature (Tzc) in the range of about 10°C to about 60°C, or about 20°C to about 38°C, or about 22°C to about 38°C. In embodiments, the glass body 400 includes a crossover temperature (Tzc) of about 20°C to about 60°C, or about 25°C to about 55°C, or about 30°C to about 50°C, or about 35°C to about 45°C, or about 40°C to about 45°C, or about 20°C to about 45°C, or about 20°C to about 40°C, or about 10°C to about 50°C. The crossover temperature is the temperature at which the CTE of the glass body 10 is exactly zero. When the glass body 10 is used in EUV lithography applications, the crossover temperature is ideally within the temperature that the glass body is expected to experience in order to minimize thermal expansion of the glass substrate during the lithography process. The designer of the EUV lithography system calculates the optimal crossover temperature for each glass body 10 in the system based on the thermal load, size, and heat removal rate provided by the system. The crossover temperature of the glass body 10 is further determined by the technique disclosed in U.S. Patent No. 10,458,936, which is incorporated herein by reference.

[0114] Furthermore, when the glass body 10 is produced by the process 100 disclosed herein, it has a viscosity of approximately 1.0 ppb / K at 20°C. 2 ~Approximately 2.5 ppb / K 2 , or approximately 1.15 ppb / K 2 ~Approximately 2.0 ppb / K 2 , or approximately 1.2 ppb / K 2 ~Approx. 1.9ppb / K 2 , or approximately 1.3 ppb / K 2 ~Approx. 1.7ppb / K 2 , or approximately 1.6 ppb / K 2 ~Approx. 2.2ppb / K 2 , or approximately 1.7 ppb / K 2 ~Approximately 2.0 ppb / K 2 , or approximately 1.8 ppb / K 2 ~Approx. 1.9ppb / K 2The glass body 10 has a CTE slope within a certain range. The CTE slope of the glass body 10 is the rate of change of the CTE of the glass body 400 as a function of the temperature of the glass body 400. When the glass body 10 is used in EUV lithography applications, the CTE slope is ideally minimized to minimize thermal expansion of the glass body caused by temperature fluctuations of the glass body during the EUV lithography process. The CTE slope is further measured by the technique disclosed in U.S. Patent No. 10,458,936.

[0115] In embodiments, when the glass body 10 is produced by process 100 disclosed herein, it includes a virtual temperature (Tf) of about 900°C or higher, or about 910°C or higher, or about 915°C or higher, or about 920°C or higher, or about 925°C or higher, or about 930°C or higher, or about 940°C or higher, or about 950°C or higher, or about 960°C or higher, or about 970°C or higher, or about 980°C or higher. In addition to or instead of this, when the glass body 10 is produced by process 100 disclosed herein, it includes a virtual temperature (Tf) of about 1500°C or lower, or about 1400°C or lower, or about 1200°C or lower, or about 1100°C or lower, or about 1000°C or lower, or about 900°C or lower.

[0116] In embodiments disclosed herein, the glass body 10, when produced by process 100 disclosed herein, has a halogen content of about 100 ppm or less, or about 75 ppm or less, or about 50 ppm or less, or about 30 ppm or less, or about 25 ppm or less, or about 20 ppm or less, or about 15 ppm or less, or about 10 ppm or less, or about 5 ppm or less, or about 2.5 ppm or less, or about 2 ppm or less, or about 1 ppm or less, or about 0.5 ppm or less, or about 0.2 ppm or less, or about 0.1 ppm or less. In particular, in the embodiments disclosed herein, when the glass body 10 is produced by the process 100 disclosed herein, it has a chlorine content of about 100 ppm or less, or about 75 ppm or less, or about 50 ppm or less, or about 30 ppm or less, or about 25 ppm or less, or about 20 ppm or less, or about 15 ppm or less, or about 10 ppm or less, or about 5 ppm or less, or about 2.5 ppm or less, or about 2 ppm or less, or about 1 ppm or less, or about 0.5 ppm or less, or about 0.2 ppm or less, or about 0.1 ppm or less.

[0117] When the glass body 10 is produced by process 100 as disclosed herein, it may be a homogeneous glass with reduced or no strietes. Strietes are periodic heterogeneities in glass that can adversely affect the properties of the glass. More specifically, strietes are formed by alternating thin layers of material in the glass having different CTE values. Process 100, as discussed above, forms a glass substrate having a homogeneous CTE value throughout, and therefore forms a glass substrate with reduced or no strietes.

[0118] Due to a low strie content in the glass body 10, the glass body can be polished to a very low surface undulation. Polished glass with strie results in uneven removal of the glass material. For example, a first layer of glass material having a first CTE value may be polished at a faster rate than a second layer of glass material having a second CTE value. In this example, the different CTE values ​​in the layers of glass material are a result of strie in the glass. Furthermore, in this example, even if both layers are exposed to the same polishing process, the first layer may be removed from the glass at a faster rate than the second layer is removed from the glass. Thus, in this example, the glass has uneven removal of the material when polishing the first and second layers. Such uneven removal of the material results in suboptimal surface undulation after the polishing process. In contrast to this example, the glass body 10 is produced to have a homogeneous CTE value throughout the entire glass body. Thus, the glass body 10 can be polished to have excellent surface undulation.

[0119] Three exemplary glass bodies were produced using process 100 with specific fixation steps in process 300 shown in Figure 3. The first glass sample had a concentration of 1.987 ppb / K at 20°C. 2 The CTE slope and crossover temperature (Tzc) of 34.91°C were included. The second glass sample showed 1.942 ppb / K at 20°C. 2 The CTE slope and crossover temperature (Tzc) of 34.39°C were included. The third glass sample showed 2.012 ppb / K at 20°C. 2 The CTE slope and crossover temperature (Tzc) of 34.40°C were included. The average CTE slope of the three glass samples was 1.98 ppb / K 2 The standard deviation was 0.04. The average Tzc of the three glass samples was 34.57°C, with a standard deviation of 0.30.

[0120] The uniform and homogeneous glass bodies produced herein reduce radiation damage when exposed to lasers. When an SiO2 article is exposed to radiation from short-wavelength lasers operating at UV, deep UV (DUV), and vacuum UV wavelengths, the radiation causes damage within a region of the article. Such lasers include, but are not limited to, those operating at wavelengths of approximately 248 nm, 193 nm, 157 nm, 13.5 nm, and even shorter wavelengths. One consequence of such radiation-induced damage is polarization-induced birefringence (PIB). As used herein, the term polarization-induced birefringence refers to the numerical difference between the measured peak birefringence level in the central portion of a region of glass exposed to a polarized laser beam after a certain time interval or number of laser pulses, and the initial birefringence of the glass before exposure to radiation.

[0121] The PIB level of the glass body is given a fluence (μJ·cm). -2 • Pulse -1 Polarization-induced birefringence (PIB) is induced by directing a linearly polarized pulsed laser beam with a wavelength of approximately 193 nm and a beam diameter of approximately 3 mm onto a fixed region of a glass body, with a pulse length (typically around several tens of nanoseconds). The birefringence measured at the center of the exposed region is measured after a certain number of pulses. The PIB value is then calculated by subtracting the initial birefringence of the glass from the measured central birefringence. The relationship between polarization-induced birefringence, pulse count, and fluence can be tentatively explained by the sample-dependent coefficient PIB = a·N·F, where N is the pulse count, F is the fluence, and PIB is the level of polarization-induced birefringence.

[0122] In one embodiment, the glass body exhibits polarization-induced birefringence of less than approximately 1 mn / cm when exposed to 5 billion pulses of a laser beam operating at approximately 193 nm, and the laser beam is approximately 500 μJ·cm -2 • Pulse -1 It has a fluence and a pulse length of about 21 ns. In certain embodiments, the glass body is at least 25 cm 2 It exhibits polarization-induced birefringence of less than approximately 0.5 nm / cm across this region.

[0123] Another consequence of such radiation-induced damage to glass bodies is wavefront distortion (WFD). Simply put, wavefront distortion can be described as the distortion of a wavefront from its original or intended shape as it propagates through an optical component. Such distortion is caused by deviations or inhomogeneities within the glass body. WFD is often characterized by a peak-valley (PV) deformation of the emerging wavefront from its intended shape, usually expressed as a fraction of wavelength. Such wavefront distortion can be induced when radiation from a laser or other light source creates inhomogeneities in the physical properties of the glass body, such as its density, due to exposure to light, for example, a laser (hence the terms photo-induced wavefront distortion and laser-induced wavefront distortion (LIWFD)).

[0124] In one embodiment, when the glass body is exposed to 5 billion pulses of a laser beam operating at approximately 193 nm, it exhibits light or laser-induced wavefront distortion measured at a wavelength of 633 nm of less than approximately 3.0 nm / cm, and the laser beam is approximately 500 μJ·cm -2 • Pulse -1 It has a fluence and a pulse length of approximately 21 ns.

[0125] According to the first embodiment, a glass body comprising titania and silica, wherein the average hydroxyl concentration between a plurality of segments of the glass body is about 60 ppm or less, the hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy, the plurality of segments comprises all adjacent segments over the length and width of the glass body, the length is about 25 mm or more, the width is about 25 mm or more, and the glass body contains a chlorine concentration of about 5 ppm or less.

[0126] According to the second embodiment, the glass body according to the first embodiment, wherein the concentration of chlorine is about 1 ppm or less.

[0127] According to a third embodiment, the glass body according to the first embodiment, wherein the glass body contains a halogen concentration of about 5 ppm or less.

[0128] According to a fourth aspect, the glass body according to the first aspect, wherein the average hydroxyl concentration between the plurality of segments of the glass body is about 20 ppm or less.

[0129] According to the fifth aspect, the glass body according to the fourth aspect, wherein the average hydroxyl concentration between the plurality of segments of the glass body is about 5 ppm or less.

[0130] According to the sixth aspect, the glass body according to the first aspect, wherein the peak-valley of hydroxyl concentrations between the plurality of segments is approximately 5 ppm or less.

[0131] According to the seventh aspect, the glass body according to the sixth aspect, wherein the peak-valley of the hydroxyl concentration between the plurality of segments is about 2 ppm or less.

[0132] According to the eighth aspect, the glass body according to the seventh aspect, wherein the peak-valley of the hydroxyl concentration between the plurality of segments is about 1 ppm or less.

[0133] The glass body according to the first embodiment, wherein the average titania concentration between the plurality of segments of the glass body is about 6.0% by weight to about 8.0% by weight.

[0134] The glass body according to the ninth embodiment, wherein the average titania concentration between the plurality of segments of the glass body is about 7.0% by weight to about 8.0% by weight.

[0135] According to the eleventh embodiment, the glass body according to the first embodiment, wherein the peak-valley of titania concentration between the plurality of segments is about 0.0010% by weight to about 0.0050% by weight.

[0136] According to the twelfth aspect, the glass body according to the first aspect, wherein the peak-valley of titania concentration between the plurality of segments is about 0.0100% by weight to about 0.0500% by weight.

[0137] According to the 13th aspect, the peak-valley of the refractive index between the plurality of segments of the glass body is approximately 1 × 10⁻⁶. -5 The glass body described in the first embodiment is as follows:

[0138] According to the 14th aspect, the peak-valley of the refractive index between the plurality of segments of the glass body is approximately 1 × 10⁻⁶ -6 ~Approx. 1×10 -4 The glass body according to the 13th embodiment.

[0139] According to the 15th aspect, the glass body is the glass body according to the first aspect, wherein the glass body includes a crossover temperature (Tzc) of about 20°C to about 60°C.

[0140] According to the sixteenth aspect, the glass body according to the first aspect, wherein the length is approximately 50 mm or more and the width is approximately 50 mm or more.

[0141] According to the 17th aspect, the glass body according to the 16th aspect, wherein the length is approximately 150 mm or more and the width is approximately 150 mm or more.

[0142] According to the 18th aspect, the glass body according to the first aspect, wherein each segment has a length (L'') and a width (W'') of approximately 12.7 mm, respectively.

[0143] According to the 19th aspect, the glass body is a photomask, as described in the first aspect.

[0144] According to the 20th aspect, a method comprising pressurizing titania-doped silica soot so that the titania-doped silica soot is approximately 0.65 g / cm³ 3 A method comprising: forming a molded soot body having the above density; heating the molded soot body to fix it; and annealing the fixed glass body, wherein the fixed and annealed glass body contains a chlorine concentration of about 5 ppm or less.

[0145] According to the 21st aspect, the method according to the 20th aspect, wherein fixing the molded soot body includes heating the molded soot body to a first temperature (T1) while flowing a CO-containing gas into a fixing furnace.

[0146] The method according to the 21st embodiment, further comprising increasing the temperature from a first temperature (T1) to a second temperature (T2) at a rate of about 10°C / hour or more, wherein the second temperature (T2) is higher than the first temperature (T1).

[0147] The method according to the 22nd embodiment, wherein the first temperature (T1) is about 900°C to about 1300°C and the second temperature (T2) is about 1100°C to about 1500°C.

[0148] The method according to the 20th embodiment, wherein fixing the molded soot body includes heating the molded soot body to a first temperature (T1) while flowing an O2-containing gas and / or CO2-containing gas into a fixing furnace made of graphite.

[0149] The method according to the 20th embodiment, wherein the titania-doped silica soot contains carbon, and fixing the molded soot further comprises heating the molded soot to a first temperature (T1) while flowing an O2-containing gas and / or CO2-containing gas into a fixing furnace.

[0150] According to the 26th aspect, fixing the molded soot body includes heating the molded soot body to a first temperature (T1) while flowing a halogen and O2-containing gas into the fixing furnace,

[0151] The ratio (X) of the partial pressure of halogen in the gas to the partial pressure of O2 in the gas is, X = [partial pressure of halogens] 2 [Partial pressure of O2] Defined by, In the formula, X is approximately 5 × 10 -6 The method according to the 20th embodiment, wherein the pressure is approximately 1.0 atm, and the partial pressures of the halogen and O2 are each in units of atm.

[0152] According to the 27th aspect, X is approximately 1 × 10 -5 The method according to the 26th embodiment, wherein the atm is approximately 0.5 atm.

[0153] According to the 28th aspect, annealing the fixed glass body is performed such that the fixed glass body is approximately 10 13 The fixed glass body is heated to a first fixation temperature (T) such that it has a viscosity of less than poise. 1f ) to heat to the first fixation temperature (T 1f Equilibration is performed at a predetermined temperature (T) for a specified period, and thereafter the fixed glass body is heated to a second fixation temperature (T) 2f The method according to the 20th embodiment, comprising rapidly cooling to )

[0154] According to the 29th aspect, the first activation temperature (T 1f The method according to the 28th embodiment, wherein the temperature is approximately 825°C or higher.

[0155] According to the 30th aspect, the first activation temperature (T 1f The method according to the 29th embodiment, wherein the temperature is approximately 900°C or higher.

[0156] According to the 31st aspect, the second activation temperature (T 2f The method according to the 28th embodiment, wherein the temperature is approximately 25°C to approximately 600°C.

[0157] According to the 32nd aspect, the method according to the 28th aspect, wherein the predetermined period is approximately 12 hours or more.

[0158] According to the 33rd aspect, the method according to the 20th aspect, wherein the concentration of chlorine is about 1 ppm or less.

[0159] According to the 34th aspect, the method according to the 20th aspect, wherein the fixed and annealed glass body contains a halogen concentration of about 5 ppm or less.

[0160] The method according to the 20th embodiment, wherein the average hydroxyl concentration between the plurality of segments of the fixed and annealed glass body is about 60 ppm or less, the hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy, the plurality of segments include all adjacent segments over the length and width of the glass body, the length is about 25 mm or more, and the width is about 25 mm or more.

[0161] According to the 36th aspect, the method according to the 35th aspect, wherein the average hydroxyl concentration between the plurality of segments of the glass body is about 10 ppm or less.

[0162] According to the 37th aspect, the method according to the 35th aspect, wherein the peak-valley of hydroxyl concentrations between the plurality of segments is approximately 5 ppm or less.

[0163] Those skilled in the art will see that various modifications and variations can be made to the embodiments of this disclosure without departing from the spirit and scope of this disclosure. Therefore, this disclosure is intended to encompass such modifications and variations, insofar as they remain within the scope of the appended claims and their equivalents.

Claims

1. It is a glass body, Contains titania and silica, The average hydroxyl concentration between the multiple segments of the glass body is approximately 0 ppm to approximately 100 ppm, the peak-valley of the hydroxyl concentration between the multiple segments is approximately 60 ppm or less, the hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy, the multiple segments include all adjacent segments across the length and width of the glass body, the length is approximately 25 mm or more, and the width is approximately 25 mm or more. The glass body is a glass body containing a chlorine concentration of approximately 100 ppm or less.

2. The glass body according to claim 1, wherein the concentration of chlorine is approximately 50 ppm or less.

3. The glass body according to claim 1 or 2, wherein the glass body contains a halogen concentration of about 5 ppm or less.

4. The glass body according to any one of claims 1 to 3, wherein the average hydroxyl concentration between the plurality of segments of the glass body is about 1 ppm to about 80 ppm.

5. The glass body according to claim 4, wherein the average hydroxyl concentration between the plurality of segments of the glass body is about 2 ppm to about 60 ppm.

6. The glass body according to any one of claims 1 to 5, wherein the peak-valley of hydroxyl concentrations between the plurality of segments is approximately 40 ppm or less.

7. The glass body according to claim 6, wherein the peak-valley of the hydroxyl concentration between the plurality of segments is about 20 ppm or less.

8. The glass body according to claim 7, wherein the peak-valley of the hydroxyl concentration between the plurality of segments is about 10 ppm or less.

9. The glass body according to any one of claims 1 to 8, wherein the average titania concentration between the plurality of segments of the glass body is about 6.0% by weight to about 8.0% by weight.

10. The glass body according to claim 9, wherein the average titania concentration between the plurality of segments of the glass body is about 7.0% by weight to about 8.0% by weight.

11. The glass body according to any one of claims 1 to 10, wherein the peak-valley of titania concentration between the plurality of segments is about 0.0010% by weight to about 0.0050% by weight.

12. The glass body according to any one of claims 1 to 11, wherein the peak-valley of titania concentration between the plurality of segments is approximately 0.0015% by weight to approximately 0.0045% by weight.

13. The peak-valley of the refractive index between the plurality of segments of the glass body is approximately 1 × 10 －５ The glass body according to any one of claims 1 to 12, which is as follows:

14. The peak-valley of the refractive index between the plurality of segments of the glass body is approximately 1 × 10 －６ ~Approx. 1×10 －４ The glass body according to claim 13.

15. The glass body according to any one of claims 1 to 14, wherein the glass body includes a crossover temperature (Tzc) of about 20°C to about 60°C.

16. The glass body according to any one of claims 1 to 15, wherein the length is approximately 50 mm or more and the width is approximately 50 mm or more.

17. The glass body according to claim 16, wherein the length is approximately 150 mm or more, and the width is approximately 150 mm or more.

18. The glass body according to any one of claims 1 to 17, wherein each segment has a length (L'') and a width (W'') of approximately 12.7 mm.

19. The glass body according to any one of claims 1 to 18, wherein the glass body is a photomask.

20. It is a method, Titania-doped silica soot is pressurized, and the titania-doped silica soot yields approximately 0.50 g / cm³. ３ To form a molded soot body having the above density, The molded soot is solidified by heating it, This includes annealing the fixed glass body, A method wherein the fixed and annealed glass body contains a chlorine concentration of approximately 100 ppm or less.

21. The process of fixing the molded soot is to heat the molded soot to a first temperature (T １ The method according to claim 20, comprising heating the furnace while flowing a CO-containing gas into the furnace.

22. raising the temperature from the first temperature (T １ ) to a second temperature (T ２ ) at a rate of about 10 °C / hour or more, the second temperature (T ２ ) being higher than the first temperature (T １ ), the method of claim 21.

23. The first temperature (T １ The temperature is approximately 900°C to approximately 1300°C, and the second temperature (T ２ The method according to claim 22, wherein the temperature is approximately 1100°C to approximately 1500°C.

24. The process of fixing the molded soot is to heat the molded soot to a first temperature (T １ While heating, O ２ Containing gases and / or CO ２ The method according to claim 20, comprising flowing a contained gas.

25. The titania-doped silica soot contains carbon, and the molded soot body is fixed to the first temperature (T １ While heating, place O in the solidification furnace. ２ Containing gases and / or CO ２ The method according to claim 20, further comprising flowing a contained gas.

26. The process of fixing the molded soot is to heat the molded soot to a first temperature (T １ While heating, halogen and O into the fixing furnace ２ This includes flowing a contained gas, and comparing the partial pressure of halogens in the gas with the O in the gas. ２ The ratio of the partial pressures (X) is X = [partial pressure of halogen] ２ / [O ２ [Partial pressure of] Defined by, In the formula, X is approximately 5 × 10 －６ atm to approximately 1.0 atm, and the partial pressure of the halogen and O ２ The method according to claim 20, wherein each of the partial pressures is in units of atm.

27. X is approximately 1 × 10 －５ The method according to claim 26, wherein the pressure is between atm and approximately 0.5 atm.

28. Annealing the fixed glass body results in the fixed glass body being approximately 10 １３ The fixed glass body is heated to a first fixation temperature (T) such that it has a viscosity of less than poise. １ｆ ) to heat to the first fixation temperature (T １ｆ ) to equilibrate for a predetermined period, and thereafter, the fixed glass body is heated to a second fixation temperature (T ２ｆ The method according to any one of claims 20 to 27, comprising rapidly cooling to the specified temperature.

29. The first fixture temperature (T １ｆ The method according to claim 28, wherein the temperature is approximately 825°C or higher.

30. The first fixture temperature (T １ｆ The method according to claim 29, wherein the temperature is approximately 900°C or higher.

31. The second fixture temperature (T ２ｆ The method according to claim 28, wherein the temperature is approximately 25°C to approximately 600°C.

32. The method according to claim 28, wherein the predetermined period is approximately 12 hours or more.

33. The method according to any one of claims 20 to 32, wherein the concentration of chlorine is about 50 ppm or less.

34. The method according to any one of claims 20 to 33, wherein the fixed and annealed glass body contains a halogen concentration of about 5 ppm or less.

35. The method according to any one of claims 20 to 34, wherein the average hydroxyl concentration between the plurality of segments of the fixed and annealed glass body is about 0 ppm to about 100 ppm, the hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy, the plurality of segments include all adjacent segments over the length and width of the glass body, the length is about 25 mm or more, and the width is about 25 mm or more.

36. The method according to claim 35, wherein the average hydroxyl concentration between the plurality of segments of the glass body is about 1 ppm to about 80 ppm.

37. The method according to claim 35, wherein the peak-valley of hydroxyl concentrations between the plurality of segments is approximately 40 ppm or less.

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