Titanium dioxide-silica glass with reduced hydroxyl and halide concentration and method for producing same

Abstract

The present disclosure provides a glass body including titanium dioxide and silicon dioxide, in which a plurality of sections of the glass body have an average hydroxyl concentration of about 0 ppm to about 100 ppm, and a peak-valley value of a hydroxyl concentration of about 60 ppm or less, the hydroxyl concentration being measured using transmission Fourier transform infrared spectroscopy, and the peak-valley value being greater than or equal to about 100 ppm, and the peak-valley value being greater than or equal to about 60 ppm, and the peak-valley value being less than or equal to about 60 ppm. And the plurality of segments includes each adjacent segment over the length and width of the glass body, the length being about 25 mm or more and the width being about 25 mm or more, and the glass body having a chlorine concentration of about 100 ppm or less.

Description

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

[0002] The present disclosure relates to titanium dioxide-silica glasses having reduced concentrations of hydroxyl and halide and methods of making the same, and more particularly, to titanium dioxide-silica glasses having lower concentrations of hydroxyl and halide that achieve uniform coefficients of thermal expansion throughout the glass body. The resulting glass articles can be suitable for extreme ultraviolet lithography applications. BACKGROUND

[0003] Extreme ultraviolet (EUV) lithography uses optics to illuminate, project, and reduce a pattern image, thereby forming an integrated circuit pattern. A benefit of using EUV radiation is that smaller integrated circuit features can be achieved. Currently, the optics used in EUV lithography are made from low thermal expansion glasses, such as titanium dioxide-silica glasses. Traditionally, the glasses are made by a flame hydrolysis process in which high purity precursors are injected into a flame, forming fine glass particles that are then deposited onto a glass body.

[0004] In EUV lithography systems, the glass is typically coated with a reflective surface, forming a mirror or photomask. In addition, the glass in EUV lithography systems must be able to meet the stringent thermal expansion requirements in the system. Specifically, the glass must be able to maintain its surface shape (referred to as “figure”) when the temperature in the system changes. Temperature stable glass is needed to avoid any induced distortions in the wavefront characteristics of the EUV projection optics. SUMMARY

[0005] Embodiments of the present disclosure include methods of producing glass bodies that are advantageously able to maintain their figure during operation of an EUV lithography system. Thus, the glass bodies according to embodiments of the present disclosure reduce or prevent any distortions in the wavefront characteristics of the EUV projection optics.

[0006] According to various aspects of the disclosure, a glass body comprising titania and silica is disclosed, wherein an average hydroxyl concentration of 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, and the plurality of segments comprises each adjacent segment across a length and a width of the glass body, the length is about 25 mm or more and the width is about 25 mm or more, and a chlorine concentration of the glass body is about 5 ppm or less.

[0007] According to various aspects of the disclosure, a method is disclosed, the method comprising the steps of: compression molding a titania-doped silica soot into a molded soot body such that a density of the titania-doped silica soot is about 0.65 g / cm 3 or more; consolidating the molded soot body by heating the molded soot body; and annealing the consolidated glass body, wherein a chlorine concentration of the consolidated and annealed glass body is about 5 ppm or less. BRIEF DESCRIPTION OF DRAWINGS

[0008] While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present application, it is believed the application will be better understood from the following description.

[0009] Figure 1 is a flow diagram of a process to form a glass body according to embodiments disclosed herein;

[0010] Figure 2A is a schematic diagram of a system to produce loose soot particles in a process according to embodiments disclosed herein; Figure 1

[0011] Figure 2B and 2C respectively show molded bodies made according to processes of Figure 1

[0012] Figure 3 is a flow diagram of a consolidation process in a process of Figure 1

[0013] Figure 4 is a flow diagram of a consolidation process in a process of Figure 1

[0014] Figure 5 is a flow diagram of a consolidation process in a process of Figure 1

[0015] Figure 6 is a flow diagram of a consolidation process in a process of Figure 1

[0016] ​​​​​​Figure 7A An exemplary glass body according to embodiments disclosed herein is shown;

[0017] Figure 7B An exemplary glass body according to embodiments disclosed herein is shown, Figure 7A A cross-section of a sample of the glass body according to embodiments disclosed herein is shown; and

[0018] Figure 7C Another cross-section of a sample of the glass body according to embodiments disclosed herein having an outer peripheral lip is shown. Figure 7A Another cross-section of a sample of the glass body according to embodiments disclosed herein having an outer peripheral lip is shown. DETAILED DESCRIPTION

[0019] As used herein, “ppm” means parts per million by weight.

[0020] As used herein, “atm” means atmosphere.

[0021] As used herein, and unless otherwise specified, the term “hydroxyl” or OH means a moiety or a collection of moieties each consisting of an oxygen atom and a protium atom (1 1 H, herein referred to as “H”). As used herein, n(OH) means the total number of OH or hydroxyl moieties in a material.

[0022] As used herein, “protium” refers to the hydrogen isotope with 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) atoms and molecules, respectively. As used herein, the terms n(H) and n(H2) refer to the total number of protium atoms and molecules, respectively, in a material.

[0023] As used herein, “deuterium” refers to the hydrogen isotope with one proton and one neutron in the atomic nucleus and an atomic weight of 2.0144. Unless otherwise specified, the symbols “D” and “D2” refer to deuterium (1 2 H) atoms and molecules, respectively. As used herein, the terms n(D) and n(D2) refer to the total number of deuterium atoms and molecules, respectively, in a material.

[0024] As used herein, the term “deuteroxyl” or OD means a moiety or a collection of moieties each consisting of an oxygen atom and a deuterium atom (1 2 H or 1 2 D, herein referred to as “D”). As used herein, n(OD) means the total number of OD moieties in a material. When hydroxyl and deuteroxyl are present at their natural isotopic abundance, the ratio of n(OD) / (n(OD)+n(OH)) in a material is equal to 2 x 10 -4 .

[0025] As used herein, unless otherwise indicated, the terms "hydrogen" and "molecular hydrogen" refer to a mixture of naturally occurring protium and deuterium molecules and atoms (99.98% protium and 0.02% deuterium).

[0026] Unless otherwise specified, when referring to any element other than hydrogen, it is understood that the element is present in its naturally occurring state; that is, the isotopic distribution of the element is as occurs in nature, and the element is not enriched in any one isotope.

[0027] As used herein, the term " fictive temperature" refers to a concept used to represent the structural state of a glass. A glass that is rapidly cooled from a high temperature will generally exhibit a higher fictive temperature than the same glass that is more slowly cooled from the same temperature, due to "freezing in" of the structure at a higher temperature. When the glass is at a high temperature, the glass structure has more time to relax toward the heat treatment temperature structure. The structure of a glass with a relatively high fictive temperature is more out of equilibrium than the structure of a glass with a relatively low fictive temperature.

[0028] Figure 1 A process 100 for producing a titanium dioxide-silica (Ti02-Si02) glass body suitable for EUV lithography applications is depicted. As discussed further below, the produced glass has a low halide concentration and a uniform OH concentration throughout the glass body. Because thermal expansion properties depend, at least in part, on OH uniformity, a uniform distribution of OH is essential to achieve uniform thermal expansion throughout the glass body. Having uniform thermal expansion throughout the glass body allows the glass body to not change shape when exposed to different temperature environments, which is beneficial in, for example, lithography applications. Accordingly, the glass bodies disclosed herein are suitable for use in, for example, EUV lithography applications. The glass can be ultra-low expansion glass (ULE® glass) manufactured by Corning Incorporated.

[0029] EUV lithography technology relies on an optical projection system to illuminate a mirror and / or photomask with EUV light such that light reflected from the mirror and / or photomask is directed onto a thin photosensitive layer deposited on the surface of a semiconductor wafer. This technology is commonly used in semiconductor device production processes. The working optical wavelength of EUV lithography systems is about 13.5 nm. This extremely short wavelength presents many challenges for the design of EUV systems. For example, the reflective coating on the mirror and / or photomask body in an EUV system cannot reflect all light at such a low wavelength. About 30% of the light is absorbed by the reflective coating instead of being reflected. The absorbed light generates undesirable heat in the glass body, causing the glass body to change shape (e.g., thermal expansion or contraction). These changes in the glass body, in turn, cause the reflective coating on the glass body to deform, resulting in wavefront aberrations of the reflected light. Wavefront aberrations can cause a decrease in the resolution of the EUV system and cause errors in the pattern formed on the photosensitive layer.

[0030] Accordingly, the glass body of the mirror and / or photomask must be able to maintain its shape and surface figure while subjected to the demanding thermal loads of an EUV system. Silica-titania glasses, such as ULE® glass, are currently the material of choice for the glass body in EUV systems.

[0031] It has recently been discovered that a higher level of compositional uniformity in a silica-titania glass minimizes any shape changes in the glass in an EUV system. More specifically, with this higher level of uniformity, the glass maintains its overall surface figure when subjected to temperature changes in an EUV system. Embodiments of the present disclosure are directed to producing a glass body having this compositional uniformity. In particular, embodiments of the present disclosure are directed to producing a glass body having a uniform OH (and OD) concentration.

[0032] Furthermore, embodiments of the present disclosure are directed to producing a glass body having a low OH (and OD) concentration. A relatively low OH (and OD) concentration is easier to achieve in the glass to produce the desired compositional uniformity than a relatively high concentration. More specifically, at a relatively low concentration, any deviation from the average OH (or OD) concentration is still within an acceptable range to achieve the desired compositional uniformity. Since the OH (and OD) concentration is low, any deviation from the average OH (or OD) is also relatively low. However, at a higher concentration, the deviation from the average concentration can become quite large, thereby producing a large variation in the OH (and OD) concentration throughout the glass body. Since the OH (and OD) concentration is high, the deviation from the average can also be quite high.

[0033] It is also known in the art that a glass body having a relatively low OH (and OD) concentration tends to have a higher viscosity, which allows the glass to reach a higher fictive temperature when annealed. Advantageously, a higher fictive temperature is associated with a lower coefficient of thermal expansion (CTE) value. As known in the art, the CTE is a material property of the glass that indicates the degree to which the material expands (changes shape) when heated. Thus, a lower CTE value advantageously allows the glass body to not change shape when exposed to different temperature environments, which is advantageous for lithography applications, as discussed above.

[0034] Ultimately, the compositional uniformity of the glass body (e.g., OH and OD uniformity) is needed to achieve a uniform and low CTE of the glass. A uniform and low CTE value advantageously allows the shape of the glass body to remain substantially unchanged when the glass is heated, which is necessary in an EUV system. As discussed above, undesirable or non-uniform heat in an EUV system can cause the glass body in the system to thermally expand or contract. However, a glass body having a uniform and low CTE value will not be as prone to this expansion or contraction distortion when heated.

[0035] Modifying agents can be added to the glass body to improve the expansion properties of the glass. However, it is known in the art that such modifying agents decrease the homogeneity of the glass, making it more difficult to manufacture a homogeneous glass. A homogeneous glass is not only important for the thermal expansion properties of the glass, but also for the polishing ability of the glass. For example, the homogeneity of the Ti02concentration throughout the glass body affects the polishing ability of the glass body. Specifically, a glass body having localized regions of different Ti02concentration will exhibit non-uniform polishing because the regions of the glass having different Ti02concentrations polish at different rates. Accordingly, embodiments of the present disclosure also produce glass bodies having a uniform Ti02concentration so that the glass will polish uniformly.

[0036] By using zero to minimal amounts of halogen, the homogeneity of the OH and Ti02concentrations in the glass body produced according to embodiments of the present disclosure is achieved. Accordingly, the halogen concentration in the produced glass body is also very low, in stark contrast to conventional processes. It is known in the art that, for example, when halogen is used to etch away OH in the glass, a glass body having a low OH concentration is produced. However, the inventors of the present disclosure were able to produce such a low OH concentration without the use of halogen.

[0037] Another important feature of the glass body in the EUV system is the temperature at which the CTE of the glass body exactly equals zero. This temperature is referred to as the zero crossing temperature, and is denoted by Tzc. Ideally, the Tzc value of the glass body in the EUV system should be close to the temperature at which the glass body is exposed to the EUV light of the EUV system. When the Tzc value coincides (or is close to) this temperature, the glass body will experience minimal expansion (and thus minimal face shape distortion) during the operation of the EUV system.

[0038] It should also be noted that Tzc is directly related to the OH and Ti02concentrations in the glass substrate (within a typical range of hypothetical temperatures). Accordingly, as the Ti02concentration increases, Tzc also increases. However, the OH concentration is negatively related to Tzc, so as the OH concentration increases, Tzc will decrease.

[0039] Referring to Figure 1 Step 110 of process 100 includes producing soot particles. More specifically, step 110 includes forming soot particles into loose soot particles, and then collecting the loose soot particles. Figure 2A A schematic diagram of a system 200 for producing loose soot particles using a combustion process is depicted. As Figure 2AAs shown in FIG. 2, the system 200 includes 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 for introducing a carrier gas, such as nitrogen, at or near the bottom of the reservoir. The carrier gas forms a gas stream with the silica precursor 224. Likewise, the second reservoir 230 includes an inlet 232 for introducing a carrier gas, such as nitrogen, at or near the bottom of the reservoir. The carrier gas in the second reservoir 230 forms a gas stream with the titania precursor 234.

[0040] The silica precursor 224 can include, for example, SiCl4and / or octamethylcyclotetrasiloxane (OMCTS). The titania precursor 234 can include, for example, TiCl4or titanium isopropoxide (TPT) (tetraisopropyl titanium (TTIP), titanium isopropoxide (TIPT)).

[0041] Bypass carrier gas streams are also introduced into the system 200 at inlets 226 and 236 to prevent the silica gas stream and the titania gas stream from becoming saturated. The silica gas stream then passes through a distribution system 242 to a manifold 248, and the titania gas stream passes through a distribution system 244 to the manifold 248.

[0042] The silica gas stream and the titania gas stream then mix in the manifold 248 to form a mixture of the two gas streams. As Figure 2A As further shown in FIG. 2, the mixture of the two gas streams flows into a reaction chamber 264. More specifically, the mixture of the two gas streams passes through a flue 252 into a burner 254 mounted in an upper portion of the reaction chamber 264. The two gas streams further join a fuel / oxygen mixture in the burner 254 to combust and oxidize the mixture. The fuel can be natural gas. Oxidation and combustion of the mixture forms loose soot particles 260 that are cooled and directed into the reaction chamber 264. The soot particles 260 include silica and titania. More specifically, the silica and titania in the particles mix at the atomic level to form Si-O-Ti bonds.

[0043] In some embodiments, dust particles 260 are guided upward through pipe 270 rather than downward into collection chamber 264. Pipe 270 may be a quartz tube that conveys the dust particles 260 in an airflow to one or more filter bags 272. The dust particles 260 are separated from the airflow through the filter bags 272 and then deposited into one or more collection chambers 264'. For example, the dust particles 260 fall downward from the filter bags 272 and into collection chamber 264'. N2 pulses may be applied periodically to the filter bags 272 to prevent excessive accumulation of dust particles 260 on the filter bags. In some embodiments, collection chamber 264' is a stainless steel hopper. The dust particles 260 can then be further collected from collection chamber 264' and deposited into a bucket, where they can be stored until further use.

[0044] The produced dust particles 260 are spherical in shape, and the distribution of SiO2 and TiO2 within the particles is basically uniform. The size of each dust particle 260 may vary depending on the conditions of the burner 254, but generally, the average diameter of the dust particles 260 is about 20 nm to about 500 nm, or about 50 nm to about 400 nm, or about 60 nm to about 300 nm, or about 50 nm to about 100 nm.

[0045] The dust particles 260 may be cooled to about 200°C or lower, or about 175°C or lower, or about 150°C or lower, or about 125°C or lower, or about 100°C or lower, or about 75°C or lower, or about 50°C or lower, or about 25°C or lower, or about 20°C or lower before reaching the collection chambers 264 and 264'.

[0046] See again Figure 1 In step 120 of process 100, dust particles 260 are removed from reaction chamber 264 and / or collection chamber 264' and deposited into a mold to form a molded dust mass with a density of approximately 0.50 g / cm³. 3 Or larger, or approximately 0.55 g / cm³ 3 Or larger, or approximately 0.60 g / cm³ 3 Or larger, or approximately 0.65 g / cm³ 3 Or larger, or approximately 0.70 g / cm³ 3 Or larger, or approximately 0.75 g / cm³ 3 Or larger, or approximately 0.80 g / cm³ 3 Or larger, or approximately 0.85 g / cm³ 3 Or greater. Alternatively, the density of the molded fume is approximately 1.50 g / cm³. 3 Or smaller, or about 1.40 g / cm³ 3or less, or about 1.30 g / cm 3 or less, or about 1.20 g / cm 3 or less, or about 1.15 g / cm 3 or less, or about 1.10 g / cm 3 or less, or about 1.00 g / cm 3 or less, or about 0.95 g / cm 3 or less, or about 0.90 g / cm 3 or less, or about 0.85 g / cm 3 or less, or about 0.80 g / cm 3 or less, or about 0.75 g / cm 3 or less, or about 0.70 g / cm 3 or less. In embodiments, the density of the molded soot body is about 0.50 g / cm 3 to about 1.50 g / cm 3 , or about 0.60 g / cm 3 to about 1.40 g / cm 3 , or about 0.80 g / cm 3 to about 1.30 g / cm 3 , or about 0.90 g / cm 3 to about 1.00 g / cm 3 , or about 0.80 g / cm 3 to about 1.50 g / cm 3 , or about 0.80 g / cm 3 to about 1.20 g / cm 3 , or about 0.80 g / cm 3 to about 0.90 g / cm 3 . The molded soot body is shaped such that the variation in density of any portion of the soot body relative to the average density of the entire soot body is about 5% or less, or about 4% or less, or about 3% or less, or about 2% or less, or about 1% or less, or about 0.75% or less, or about 0.50% or less, or about 0.25% or less, or about 0.20% or less, or about 0.15% or less, or about 0.10% or less, or about 0.05% or less, or about 0.02% or less, or about 0.01% or less, or about 0.00%. Figure 2B An exemplary cylindrical molded soot body is shown, and Figure 2C An exemplary rectangular molded soot body is shown, but the molded soot body can also comprise other shapes different from those specifically depicted herein. As Figure 2B and 2C shown, the molded soot body has a length L and a height H. It should be noted that the length L is alsoFigure 2B the diameter of the cylindrical body.

[0047] In embodiments, the length L of the body can be about 20 mm to about 1300 mm, or about 40 mm to about 1200 mm, or about 60 mm to about 1000 mm, or about 80 mm to about 800 mm, or about 100 mm to about 60 mm, or about 20 mm to about 40 mm. Further, in some embodiments, the height H of the body is about 50 mm to about 500 mm, or about 60 mm to about 400 mm, or about 80 mm to about 200 mm, or about 100 mm to about 200 mm, or about 250 mm to about 500 mm, or about 250 mm to about 400 mm, or about 250 mm to about 300 mm, or about 200 mm to about 500 mm, or about 200 mm to about 400 mm, or about 200 mm to about 300 mm. It should be noted, however, that the length L and height H of the body can vary and are not limited by the embodiments disclosed herein. It should also be noted that in some embodiments, the length L of the body is greater than the height H, while in other embodiments, the height H is greater than the length L.

[0048] Referring back to process 100, at step 130, the molded soot body is then consolidated into a glass body. After consolidation, the glass body is re-melted at step 140 and then annealed at step 150 to release any internal stresses in the glass body and to lower the Tf in the glass body while reducing the variation in Tf in the glass body. The release of internal stresses enables higher quality cutting and machining of the glass body, such as cutting the glass body into a plurality of pieces. In some embodiments, the glass body annealing duration is about 100 hours or more, or about 200 hours or more, or about 250 hours or more. The maximum annealing temperature can be about 750 °C to about 1200 °C, or about 800 °C to about 1100 °C, or about 900 °C to about 1000 °C. Upon completion of the annealing step, subsequent finishing steps, such as shaping, grinding, polishing, and / or slicing, can be performed on the glass body.

[0049] In a conventional consolidation process (in step 130 of process 100), the molded soot body is placed into a consolidation furnace and heated to dry the soot body. Specifically, the conventional consolidation process includes drying the soot body with a halide-containing gas (such as a chlorine-containing gas) while the soot body is heated. Next, the soot body is heated to a temperature of up to about 1500 °C in an inert gas atmosphere to fully consolidate the soot body into a glass body.

[0050] In embodiments disclosed herein, aspects of the disclosure include consolidating the molded soot body during consolidation at step 130 without exposing the soot to halides. Specifically,Figures 3 to 5 The consolidation processes of the'688 patent (discussed below) are all consolidating soot bodies without (i.e., zero) intentional addition of halides. Figure 6 The processes of the'688 patent minimize the addition of halides and oxygen while removing moisture to minimize the impact of halides on the Ti02. As a result, the produced glass bodies contain almost no halides (e.g., chlorine, fluorine, bromine) that can adversely cause non-uniformity of the glass. As known in the art, the presence of halides can cause undesirable reactions with the Ti02in the glass. For example, chlorine reacts with Ti02to form titanium chlorides and titanium oxychlorides (e.g., titanium tetrachloride TiCl4, titanium trichloride TiCl3, titanium dichloride TiCl2), which are in the gas phase and thus can move to different locations within the glass body. Since the titanium chlorides are capable of moving Ti within the glass body, the Ti is not uniformly dispersed throughout the glass body but rather is unevenly dispersed. In turn, the produced glass body can contain regions of relatively high Ti concentration. The higher levels of Ti in these regions will cause the glass body to polish unevenly. Thus, embodiments of the present disclosure consolidate soot bodies with minimal amounts of halides or without any intentional addition of halides.

[0051] Figure 3 A first exemplary embodiment of the consolidation step of the process 100 is depicted. More specifically, in some embodiments, the step 130 of the process 100 comprises the steps of the process 300. As shown in the'688 patent, the process 300 comprises actively drying (e.g., dehydrating) the molded soot body with carbon monoxide (CO) while consolidating the soot. Specifically, the process 300 comprises actively drying the molded soot body with CO to reduce the combined concentration of OH and OD in the consolidated glass body. Also, the process 300 comprises actively drying the molded soot body with CO to produce a glass body having a uniform concentration of OH and OD throughout. Figure 3

[0052] The process 300 is performed in an atmosphere that is substantially free of halogens. As used herein, "substantially free of halogens" means that halogens (e.g., chlorine, fluorine, bromine) are not intentionally added to the soot body in elemental form or in halogen-containing compounds. It is understood that the glass body can unintentionally contain small amounts of halogens due to contamination.

[0053] ​The mechanism by which the soot bodies are dried using the steps of process 300 is based on the reaction of CO with OH (or OD) to form H2 (or D2) and CO2. Step 310 of process 300 includes flowing a CO-containing gas into the consolidation furnace to dry (e.g., dehydrate) the molded soot bodies. In addition to CO, the gas can include other components, such as one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The gas includes from about 0.5 wt% to about 10 wt% CO, or from about 1 wt% to about 8 wt% CO, or from about 2 wt% to about 6 wt% CO, or from about 2 wt% to about 4 wt% CO. The drying of step 310 can be performed for a period of time ranging from about 1 hour to about 200 hours, or from about 5 hours to about 100 hours, or from about 10 hours to about 50 hours.

[0054] Unless otherwise specified, the drying steps disclosed herein are performed in an atmosphere in which a gas is continuously flowing over or "sweeping" the soot bodies.

[0055] The drying of step 310 is performed while the glass is heated, which causes any OH and / or OD in the soot to react with the CO gas to form CO2 and H2 (or D2), thereby removing any OH and / or OD from the soot. It is noted that one 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, at least one of OH and OD can be incorporated into the soot bodies prior to the drying of step 310 in order to achieve a predetermined or desired concentration of OH and / or OD in the produced glass bodies and to improve the uniformity of these molecules in the produced glass bodies.

[0056] At step 320, the CO gas can be removed from the consolidation furnace and the glass soot by, for example, flowing an inert gas (e.g., helium, argon, nitrogen, neon) through the consolidation furnace. In embodiments, the inert gas is helium. At step 330, oxygen (O2) is flowed through the consolidation furnace. The O2-containing gas can further include one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The O2-containing gas should be free or substantially free of water. If trace amounts of water are present in the O2-containing atmosphere, the soot bodies will absorb the water during the sintering step, resulting in an increase in the OH concentration of the glass at or near the sintered glass edge.

[0057] The O2-containing gas comprises about 0.5 wt% to about 5 wt% O2, or about 1 wt% to about 4 wt% O2, or about 1 wt% to about 3 wt% O2. The oxidation step (step 330) can be performed for a period of time ranging from about 30 minutes to about 5 hours, or about 30 minutes to about 2 hours, or about 30 minutes to about 1 hour. The O2 gas oxidizes the titanium species (Ti, TiO, Ti2O3) in the soot body, thereby re-forming titanium dioxide (TiO2). It is noted that the oxidation of the titanium species occurs while the soot body is still porous (before the soot is fully densified). In addition, the O2 gas ensures complete conversion of CO to CO2 and repairs any damage to the soot body caused by CO drying.

[0058] Unless otherwise specified, the oxidation steps disclosed herein are performed in an atmosphere in which a gas is continuously flowed over or “swept” over the soot body.

[0059] During steps 310-330, the consolidation furnace is heated to a first temperature (T1) of about 900 °C to about 1300 °C, or about 950 °C to about 1250 °C, or about 1000 °C to about 1200 °C, or about 1050 °C to about 1150 °C, or about 1100 °C to about 1200 °C. In some embodiments, the drying of step 310 is performed at a different temperature than the oxidation of step 330. As mentioned above, steps 310-330 are performed before the soot body is fully densified and the pores in the glass are open. The open-pore structure of the soot body enables more efficient drying of the glass and removal of water, OH, and OD groups with the CO-containing gas. At step 340, the temperature of the consolidation furnace is increased in order to densify the soot body. Specifically, the temperature is increased from the first temperature (T1) to a second temperature (T2) in order to fully densify the glass and close any open pores in the glass. The second temperature is about 1100 °C to about 1500 °C, or about 1150 °C to about 1450 °C, or about 1200 °C to about 1400 °C, or about 1225 °C to about 1350 °C, or about 1225 °C to about 1300 °C, or about 1250 °C to about 1300 °C, or about 1250 °C to about 1275 °C. The second temperature is higher than the first temperature. While the soot body is heated at the second temperature, an inert gas (e.g., helium, argon, nitrogen, neon) can be flowed through the consolidation furnace. In some embodiments, the heating soot body is performed in a vacuum.

[0060] The densification of step 340 can be performed for a period of time ranging from about 4 hours to about 20 hours, or about 5 hours to about 15 hours, or about 5 hours to about 10 hours. Thus, the soot body can be heated at the second temperature for these periods of time.

[0061] It is noted that during steps 310-330 of process 300, the OH (and OD) in the soot body is reduced and / or eliminated. Specifically, the OH (and OD) in the soot body is converted to H2 (or D2) and CO2 under the CO dryout. By reducing and / or eliminating the OH (and OD), the temperature of the consolidation furnace can be ramped up from the first temperature to the second temperature at a faster rate while reducing OH non-uniformity issues. In the case of a soot body containing a larger amount of OH (or OD), the glass is more susceptible to non-uniformity when subjected to such a fast temperature ramp rate during consolidation. A fast temperature ramp rate can cause the radially outer portions of the soot body to sinter before (and thus for a longer period of time than) the radially inner portions of the soot body. This can be a problem for soot bodies containing a larger amount of OH (or OD) because sintering causes the soot body to lose OH (or OD) molecules. As a result, the radially outer portions of the soot body can lose more OH (or OD) molecules than the radially inner portions of the soot body, resulting in a non-uniform glass body. This problem is greatly reduced when the concentration of OH (or OD) in the soot body is very low or even zero.

[0062] In embodiments, the temperature of the consolidation furnace is ramped up from the first temperature (T1) to the second temperature (T2) at a rate of about 5°C / hr or more, or about 8°C / hr or more, or about 10°C / hr or more, or about 12°C / hr or more, or about 15°C / hr or more, or about 20°C / hr or more, or about 25°C / hr or more, or about 30°C / hr or more, or about 35°C / hr or more, or about 40°C / hr or more, or about 45°C / hr or more, or about 50°C / hr or more (during step 340). Additionally or alternatively, the temperature of the consolidation furnace is ramped up from the first temperature to the second temperature at a rate of about 60°C / hr or less, or about 55°C / hr or less, or about 50°C / hr or less, or about 45°C / hr or less, or about 40°C / hr or less, or about 35°C / hr or less, or about 30°C / hr or less, or about 25°C / hr or less, or about 20°C / hr or less, or about 15°C / hr or less, or about 12°C / hr or less, or about 10°C / hr or less, or about 8°C / hr or less (during step 340). In embodiments, the temperature is ramped up at a rate of about 5°C / hr to about 60°C / hr, or about 8°C / hr to about 55°C / hr.

[0063] Figure 4 A second exemplary embodiment of the consolidating step of process 100 is depicted. More specifically, in some embodiments, step 130 of process 100 comprises the steps of process 400. As Figure 4As shown in FIG. 4, process 400 includes drying (e.g., dehydrating) the molded soot body in a graphite furnace. Similar to process 300 described above, the steps of process 400 are also performed in a substantially halogen-free atmosphere. The mechanism for drying the soot body using the steps of process 400 is based on the reaction of C in the graphite furnace with O2gas or CO2gas to produce CO, which dries the glass and reacts with OH (or OD) in the glass to produce H2 (or D2) and CO2.

[0064] Step 410 of process 400 includes flowing an O2-containing gas and / or a CO2- containing gas into the consolidation furnace to dry (e.g., dehydrate) the soot. In addition to O2and / or CO2, the gas can also include other components, such as one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The gas includes from about 0.5 wt% to about 10 wt% O2, or from about 1 wt% to about 8 wt% O2, or from about 2 wt% to about 6 wt% O2, or from about 2 wt% to about 4 wt% O2. Additionally or alternatively, the gas includes from about 0.5 wt% to about 10 wt% CO2, or from about 1 wt% to about 8 wt% CO2, or from about 2 wt% to about 6 wt% CO2, or from about 2 wt% to about 4 wt% CO2. The drying of step 410 can be performed for a period of time ranging from about 1 hour to about 200 hours, or from about 5 hours to about 100 hours, or from about 10 hours to about 50 hours.

[0065] The O2in the O2-containing gas and / or the CO2in the CO2-containing gas reacts with the 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 of step 410 removes OH and / or OD from the soot by reacting any OH and / or OD in the soot with the generated CO to form CO2, while the soot is being heated. In some embodiments, at least one of OH and OD can be incorporated into the soot body prior to the drying of step 410 in order to achieve a predetermined or desired concentration of OH and / or OD in the produced glass body and to improve the uniformity of these molecules in the produced glass body.

[0066] It should be noted that even without the addition of an O2-containing gas or a CO2-containing gas, OH in the soot will generate H2O or D2O when heated. These waters (H2O and D2O) react with the C in the graphite furnace to produce CO, which helps to dry the soot, as described above. However, in order to completely dry the soot, it is likely that an O2-containing gas and / or a CO2-containing gas will need to be added.

[0067] At step 420, the CO gas can be removed from the consolidation furnace and the soot body by, for example, flowing an inert gas (e.g., helium, argon, nitrogen, neon) through the consolidation furnace. In embodiments, the inert gas is helium.

[0068] Unlike process 300, process 400 does not include an oxidation step with an O2-containing gas because it would react with C in the graphite furnace and destroy the graphite furnace. Thus, the titanium species (Ti, TiO, Ti2O3) in the soot body are not oxidized by the O2-containing gas, such that the produced glass body will contain a reduced amount of titanium dioxide (TiO2).

[0069] During steps 410-420, the consolidation furnace is heated to a first temperature (T1), as discussed above. Steps 410-420 are performed before the soot body is fully densified and the open porosity in the soot is open. The open porosity structure of the soot body enables more efficient drying of the soot with the generated CO-containing gas and removal of water, OH, and OD groups. At step 430, the temperature of the consolidation furnace is increased in order to densify the soot body. In particular, as discussed above, the temperature is increased from the first temperature (T1) to a second temperature (T2) to fully densify the soot and close any open porosity in the soot. While heating the soot body at the second temperature, an inert gas (e.g., helium, argon, nitrogen, neon) can be flowed through the consolidation furnace or under vacuum.

[0070] The densification of step 430 can be performed for a period of time ranging from about 4 hours to about 20 hours, or from about 5 hours to about 15 hours, or from about 5 hours to about 10 hours. Thus, the soot body can be heated at the second temperature for these periods of time.

[0071] It is noted that during steps 410-420 of process 400, the OH (and OD) in the soot body are reduced and / or eliminated. In particular, the OH (and OD) in the soot body are converted to H2 (or D2) and CO2 under CO drying. By reducing and / or eliminating the OH (and OD), the temperature of the consolidation furnace can be rapidly increased from the first temperature to the second temperature at a faster rate as discussed above with reference to process 300 (e.g., from about 5 °C / hr to about 60 °C / hr).

[0072] Figure 5 A third exemplary embodiment of the consolidation step of process 100 is depicted. More specifically, in some embodiments, step 130 of process 100 includes the steps of process 500. As Figure 5As shown in FIG. 5, process 500 includes drying (e.g., dehydrating) the molded soot body containing carbon to reduce the combined concentration of OH and OD in the consolidated glass body. Similar to process 300 described above, the steps of process 500 are also performed in a substantially halogen-free atmosphere. The mechanism for drying the soot body using the steps of process 400 is based on the reaction of carbon in the molded soot body with either O2gas or CO2gas to produce CO, which dries the soot and reacts with OH (or OD) in the glass to produce H2 (or D2) and CO2.

[0073] In process 500, soot particles 260 (as discussed above with reference to FIG. 2) are first mixed with carbon powder. In some embodiments, soot particles 260 are mixed with carbon powder in reaction chamber 264. The resulting soot particles can include about 1 wt% to about 10 wt% carbon, or about 2 wt% to about 8 wt% carbon, or about 1 wt% to about 5 wt% carbon. These soot particles are then molded into a soot body, as discussed above. The molded soot body containing carbon is then consolidated using the steps of process 500.

[0074] Step 510 of process 500 includes flowing an O2-containing gas and / or a CO2- containing gas into the consolidation furnace to dry (e.g., dehydrate) the soot. The gas can include other components in addition to O2and / or CO2, such as one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). In some embodiments, the gas includes about 0.5 wt% to about 10 wt% O2, or about 1 wt% to about 8 wt% O2, or about 2 wt% to about 6 wt% O2, or about 2 wt% to about 4 wt% O2. Additionally or alternatively, in some embodiments, the gas includes about 0.5 wt% to about 10 wt% CO2, or about 1 wt% to about 8 wt% CO2, or about 2 wt% to about 6 wt% CO2, or about 2 wt% to about 4 wt% CO2. The drying of step 510 can be performed for a time 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.

[0075] The O2in the O2-containing gas and / or the CO2in the CO2-containing gas reacts 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 of step 510 removes OH and / or OD from the glass by reacting any OH and / or OD in the glass with the generated CO to form CO2, while the soot is heated. In some embodiments, at least one of OH and OD can be incorporated into the soot body prior to the drying of step 510 in order to achieve a predetermined or desired concentration of OH and / or OD in the produced glass body and to improve the uniformity of these molecules in the produced glass body.

[0076] At step 520, the CO gas can be evacuated from the consolidation furnace and soot body by, for example, flowing an inert gas (e.g., helium, argon, nitrogen, neon) through the consolidation furnace. In embodiments, the inert gas is helium.

[0077] At step 530, oxygen gas (O2) is flowed through the consolidation furnace. The O2-containing gas can further include one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The O2-containing gas should be free of water or substantially free of water. If trace amounts of water are present in the O2-containing atmosphere, the soot body will absorb the water during the sintering step, resulting in an increased OH concentration of the glass at or near the sintered glass edge.

[0078] The O2-containing gas includes about 0.5 wt% to about 5 wt% O2, or about 1 wt% to about 4 wt% O2, or about 1 wt% to about 3 wt% O2. The oxidation step (step 530) can be performed for a period of time ranging from about 30 minutes to about 5 hours, or about 30 minutes to about 2 hours, or about 30 minutes to about 1 hour. The O2 gas oxidizes the titanium species (Ti, TiO, Ti2O3) in the soot body, thereby re-forming titanium dioxide (TiO2). It is noted that the oxidation of the titanium species occurs while the soot body is still porous (before the soot is fully densified). Further, the O2 gas ensures that the CO is fully converted to CO2 and repairs any damage to the soot body caused by the CO drying.

[0079] During steps 510-530, the consolidation furnace is heated to a first temperature (T1), as discussed above. Steps 510-530 are performed before the soot body is fully densified and while the pores in the soot are open. The open-pore structure of the soot body enables more efficient drying of the soot and removal of water, OH, and OD groups with the generated CO-containing gas. At step 540, the temperature of the consolidation furnace is increased in order to densify the soot body. In particular, as discussed above, the temperature is increased from the first temperature (T1) to a second temperature (T2) in order to fully densify the soot and to close any open pores in the soot. While the soot body is heated at the second temperature, an inert gas (e.g., helium, argon, nitrogen, neon) can be flowed through the consolidation furnace or under vacuum.

[0080] The densification of step 540 can be performed for a period of time ranging from about 4 hours to about 20 hours, or about 5 hours to about 15 hours, or about 5 hours to about 10 hours. Accordingly, the soot body can be heated at the second temperature for these periods of time.

[0081] It is noted that during steps 510-530 of process 500, OH (and OD) in the glass body is reduced and / or eliminated. Specifically, OH (and OD) in the glass body is converted to H2 (or D2) and CO2 under CO drying. By reducing and / or eliminating OH (and OD), the temperature of the consolidation furnace can be rapidly increased from the first temperature to the second temperature at a faster rate as discussed above with reference to process 300 (e.g., about 5°C / hr to about 60°C / hr).

[0082] Figure 6 A fourth exemplary embodiment of the consolidation step of process 100 is depicted. More specifically, in some embodiments, step 130 of process 100 comprises the steps of process 600. As shown in FIG. 6, process 600 comprises drying (e.g., dehydrating) the molded soot body with a halogen at a desired ratio of the halogen to O2 to produce a soot body having a low halogen level. The mechanism for drying the soot body using the steps of process 600 is based on halogen drying and etching, but the halogen is kept at a low enough level such that it does not affect the CTE uniformity in the produced glass body. Figure 6

[0083] In step 610 of process 500, a gas comprising a halogen and O2 is flowed into the consolidation furnace. The ratio (X) of the partial pressure of the halogen to the partial pressure of O2 in the gas is defined by the following equation:

[0084] X = [partial pressure of halogen] / [partial pressure of O2] 2

[0085] where the partial pressure of the halogen and the partial pressure of O2 in the above equation are in units of atmospheres (atm). Thus, X is also in units of atm. X should be equal to about 5 x 10 -6 atm to about 1.0 atm to maintain the desired ratio of halogen to O2 (such that the halogen does not affect the CTE uniformity in the glass). Lower values of X correspond to reduced formation of titanium chloride (TiCl3), which in turn minimizes the movement of TiO2 in the produced glass body.

[0086] A preferred range of X is about 1 x 10 -6 atm to about 0.5 atm, or about 1 x 10 -6 atm to about 0.3 atm, or about 1 x 10 -6 atm to about 0.1 atm, or about 1 x 10 -5 atm to about 1.0 atm, or about 1 x 10 -5 atm to about 0.5 atm, or about 1 x 10 -5 atm to about 0.3 atm, or about 1 x 10 -5 ​​atm to about 0.1 atm, or about 5 x 10 -4 atm to about 1.0 atm, or about 1 x 10 -4 atm to about 0.5 atm, or about 1 x 10 -4 atm to about 0.3 atm, or about 1 x 10 -4 atm to about 0.1 atm, or about 5 x 10 -5 atm to about 0.1 atm, or about 5 x 10 -5 atm to about 0.01 atm, or about 0.0015 atm to about 0.5 atm, or about 0.0013 atm to about 0.5 atm, or about 0.0015 atm to about 0.01 atm, or about 0.0013 atm to about 0.01 atm. X represents the loss of TiO2in the glass due to the presence of halogen. Thus, in some embodiments, it is preferable to have X low to minimize TiO2loss. Preferably, the partial pressure of halogen in the gas ([halogen]) is low, and the partial pressure of O2in the gas ([O2]) is high, resulting in a low X value.

[0087] In one exemplary embodiment, the partial pressure of chlorine in the gas is 0.00218 atm, and the partial pressure of O2in the gas is 0.09071 atm, resulting in an X value of 5.2 x 10 -5 atm. In another exemplary example, the partial pressure of chlorine in the gas is 0.00109 atm, and the partial pressure of O2in the gas is 0.09081 atm, resulting in an X value of 1.31 x 10 -5 atm. In another exemplary example, the partial pressure of chlorine in the gas is 0.07692 atm, and the partial pressure of O2in the gas is 0.15385 atm, resulting in an X value of 3.85 x 10 -2 atm. In another exemplary example, the partial pressure of chlorine in the gas is 0.2 atm, and the partial pressure of O2in the gas is 0.13333 atm, resulting in an X value of 3.00 x 10 -1 atm. In another exemplary example, the partial pressure of chlorine in the gas is 0.00171 atm, and the partial pressure of O2in the gas is 0.28523 atm, resulting in an X value of 1.03 x 10 -5 atm.

[0088] The halogen-containing and O2-containing gas can further include one or more inert carrier gases (e.g., helium, argon, nitrogen, neon). The halogen-containing and O2-containing gas should be free of water or substantially free of water. The halogen etches the soot and dries (e.g., dehydrates) the soot. The O2 gas oxidizes the titanium species (Ti, TiO, Ti2O3) in the soot, thereby forming titanium dioxide (TiO2). It should be noted that the oxidation of the titanium species occurs while the soot is still porous (before the soot is fully densified).

[0089] At step 620, the halogen-containing and O2-containing gas can be removed from the consolidation furnace and the soot by, for example, flowing an inert gas (e.g., helium, argon, nitrogen, neon) through the consolidation furnace. In an embodiment, the inert gas is helium.

[0090] During steps 610-620, the consolidation furnace is heated to a first temperature (T1), as discussed above. Steps 610-620 are performed before the soot is fully densified and while the pores in the soot are open. The open-pore structure of the soot enables more efficient drying of the soot with the halogen. At step 630, the temperature of the consolidation furnace is increased in order to densify the soot. In particular, as discussed above, the temperature is increased from the first temperature (T1) to a second temperature (T2) to fully densify the soot and to close any open pores in the soot. While the soot is heated at the second temperature, an inert gas (e.g., helium, argon, nitrogen, neon) can be flowed through the consolidation furnace or flowed in a vacuum.

[0091] The densification of step 630 can be performed for a period of time ranging from about 4 hours to about 20 hours, or from about 5 hours to about 15 hours, or from about 5 hours to about 10 hours. Thus, the soot can be heated at the second temperature for these periods of time.

[0092] It should be noted that during steps 610-620 of process 500, the OH (and OD) in the glass body is reduced and / or eliminated. In particular, the halogen in the halogen-containing gas reacts with the 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. By reducing and / or eliminating the OH (and OD), the temperature of the consolidation furnace can be increased rapidly from the first temperature to the second temperature at a faster rate (e.g., from about 5 °C / hr to about 60 °C / hr) as discussed above with reference to process 300.

[0093] Referring again to Figure 1, process 100 includes annealing the glass after the consolidation step disclosed above. According to embodiments disclosed herein, the annealing step 150 of process 100 can include a post-forming fictivation process. As used herein, "fictivation" refers to imposing a specified temperature or thermal history on a glass through appropriate heat treatment. In embodiments disclosed herein, the fictivation process includes "rapidly cooling" the glass from a first fictive temperature (T 1f ) to a second fictive temperature (T 2f ) at a rate of about 5 °C / s or greater, or about 10 °C / s or greater, or about 15 °C / s or greater, or about 20 °C / s or greater, or about 25 °C / s or greater, or about 30 °C / s or greater. In some embodiments, the fictivation process includes heating the glass to the first fictive temperature (T 1f ) such that the viscosity of the glass is less than 10 13 poise, then equilibrating the glass at the first fictive temperature (T 1f ) for a predetermined period of time, and then rapidly quenching the glass to the second fictive temperature (T 2f ) that is below the strain point of the glass. In embodiments, the glass is heated to the first fictive temperature (T 1f ) such that the viscosity of the glass is about 10 9 poise to about 10 13 poise, or about 10 9 poise to about 10 12 poise, or about 10 9 poise to about 10 11 poise, or about 10 9 poise to about 10 10 poise, followed by the equilibrating and quenching steps.

[0094] In some embodiments, the first fictive temperature (T 1f ) is above the annealing point of the glass. For example, the first fictive temperature (T 1f ) is about 825 °C or greater, or about 850 °C or greater, or about 875 °C or greater, or about 900 °C or greater, or about 925 °C or greater, or about 950 °C or greater, or about 975 °C or greater, or about 1000 °C or greater, or about 1025 °C or greater, or about 1050 °C or greater, or about 1075 °C or greater, or about 1100 °C or greater, or about 1125 °C or greater, or about 1150 °C or greater. Further, in some embodiments, the second fictive temperature (T 2f ) is about room temperature (e.g., about 25 °C). In embodiments, the second fictive temperature (T 2fabout 40 °C or more below the isothermal holding temperature of the glass, or in the range of about 25 °C to about 600 °C, or about 100 °C to about 500 °C. The glass can be equilibrated at the first hypothetical temperature (T 1f ) for a period of about 12 hours or more, or about 16 hours or more, or about 20 hours or more, or about 24 hours or more, or about 30 hours or more. As a result of the disclosed hypothetical process, the resulting glass body has a high level of intrinsic damage resistance.

[0095] As discussed above, the glass bodies produced in embodiments disclosed herein include a uniform OH (and OD) concentration. Further, in embodiments, the produced glass bodies include a relatively low OH (and OD) concentration. For purposes of the present disclosure, the OH (and OD) concentration is measured by sectioning the produced glass body into a plurality of segments and measuring the OH (and OD) concentration of each segment, as discussed below with reference to Figures 7A to 7C . Figure 7A A glass body 10 produced by the process 100 of Figure 1 is shown. Thus, the glass body 10 is a glass body resulting after the annealing step 150 of the process 100. The glass body 10 can be an ingot or a substrate upon which one or more layers are coated in downstream processing.

[0096] As discussed above, the glass body 10 is a TiO2-SiO2glass. The SiO2concentration in the glass body 10 can be about 80 wt% or more, or about 85 wt% or more, or about 90 wt% or more, or about 92 wt% or more, or about 95 wt% or more, or about 97 wt% or more, or about 98 wt% or more, or about 99 wt% or more, or about 85 wt% to about 97 wt%, or about 90 wt% to about 95 wt%. The TiO2concentration in the glass body 10 can 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 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%.

[0097] The glass body 10 has a length L’, a width W’, and a height H’, as Figure 7AAs shown in FIG. 1, the length L' and the width W' can each be greater than the height H'. For example, the length L' and the width W' can 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. Additionally or alternatively, the length L' and the width W' of the glass body 10 can each be about 15 mm or greater, or about 20 mm or greater, or about 25 mm or greater, or about 50 mm or greater, or about 75 mm or greater, or about 100 mm or greater, or about 150 mm or greater, or about 200 mm or greater, or about 250 mm or greater, or about 300 mm or greater, or about 350 mm or greater, or about 400 mm or greater, or about 450 mm or greater, or about 500 mm or greater. In some embodiments, the length L' and the width W' can each be about 150 mm, or about 152 mm, or about 179 mm. However, it is also contemplated in some embodiments that the length L' can be different than the width.

[0098] Additionally, the height H' can be less than each of the length L' and the 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. Additionally or alternatively, the height H' is about 5 mm or greater, or about 10 mm or greater, or about 15 mm or greater, or about 20 mm or greater, or about 25 mm or greater, or about 50 mm or greater, or about 75 mm or greater, or about 100 mm or greater, or about 150 mm or greater, or about 200 mm or greater, or about 250 mm or greater, or about 300 mm or greater, or about 350 mm or greater, or about 400 mm or greater. In some embodiments, the height H' is about 63 mm, or about 150 mm, or about 152 mm.

[0099] As also discussed above, the glass body 10 can be cut into a plurality of samples. Figure 7A An exemplary sample 15 of the glass body 10 is shown, which is along the smallest dimension (i.e., the characteristic length Lc This forms a sub-section of the glass. Each sample 15 can also be considered a glass, a substrate, or a wafer. Figure 7A In this embodiment, the height H' is less than each of the length L' and the width W', such that the height H' is the minimum dimension. Therefore, the height h' of sample 15 extends along the height H' of glass body 10. Figure 7A In one embodiment, the glass body 10 includes a plurality of samples along its height H'. However, in other embodiments, it is also contemplated that a single sample 15 extends along the entire height H' of the glass body 10 (or along the entire minimum dimension of the glass body when the minimum dimension is not height H'). In these embodiments, the glass body 10 includes only one sample 15, such that one sample 15 forms the entire glass body 10.

[0100] Although Figure 7A Glass body 10 and sample 15 are depicted as square assemblies with flat surfaces, but other shapes are also contemplated in the embodiments. For example, the outer contours of glass body 10 and / or sample 15 may be circular, elliptical, or asymmetrical. Furthermore, glass body 10 and / or sample 15 may be curved, forming concave or convex structures. In one exemplary embodiment, glass body 10 is formed from a single sample 15 (such that the single sample 15 extends the entire length, width, and height of glass body 10), and glass body 10 has a concave structure. Sample 15 may be a photomask, photomask, mirror, and / or photomask support.

[0101] Each sample 15 had substantially uniform OH, OD, and TiO2 concentrations along its length and width. To determine the homogeneity of the samples within the vitreous, each sample was divided into segments along its length and width. For example, Figure 7B The sample 15 is shown to be divided into several segments 20 along its cross-sectional length L' and width W'. The concentration of one or more components (e.g., OH, OD, TiO2) in each segment 20 can then be determined to determine the uniformity of each of these components in the sample 15. For example, the OH concentration in each segment 20 can be measured to determine the uniformity of OH concentration across the cross-section of the sample 15. As discussed further below, the concentration of one or more components is determined by the entire thickness h' of each segment 20.

[0102] Although Figure 7B Segment 20 is shown as extending along the entire length L' and width W' of sample 15, but it is also considered that the portion of sample 15 containing segment 20 may be smaller than the entire cross-sectional length L' and width W'. For example, as Figure 7CAs shown, sample 15 may include an outer peripheral lip 17 on which no segment 20 is formed. Therefore, the outer peripheral lip 17 may be a gap between the end of segment 20 and the outer edge of sample 15. In embodiments, the outer peripheral lip may extend to 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.

[0103] Segment 20 can be an adjacent segment over a specific length and width of sample 15 (such that no gap is formed between adjacent segments). As discussed above, this specific length and width (the specific length and width over which all segments 20 extend) can be equal to or less than the length L' and width W' of sample 15. In an embodiment, segment 20 is an adjacent segment over the length and width of sample 15 (the length and width over which all segments 20 extend), such that the length and width are each about 25 mm or greater, or about 30 mm or greater, or about 40 mm or greater, or about 50 mm or greater, or about 60 mm or greater, or about 75 mm or greater, or about 100 mm or greater, or about 125 mm or greater, or about 150 mm or greater, or about 175 mm or greater, or about 180 mm or greater, or about 190 mm or greater, or about 200 mm or greater, or about 250 mm or greater.

[0104] When sample 15 contains a flat surface, segment 20 is formed along the flat planar surface, such as... Figure 7B As shown in the figure. However, when sample 15 includes a concave or convex surface, segment 20 is formed along the curved surface of sample 15.

[0105] like Figure 7B As shown, the length L" and width W" of each segment 20 are both approximately 12.7 mm. However, in other embodiments, it is also considered that the length L" is not 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 lip 17.

[0106] The height of each segment 20 is the height h' of sample 15, as discussed above. Therefore, in this embodiment, the height h' is approximately 7.62 mm.

[0107] As discussed above, the concentration of one or more components within each segment 20 can be determined. Thus, for example, the OH concentration of each adjacent segment 20 within sample 15 can be determined. When the length and width of each segment 20 is 12.7 mm, the component concentration is determined at a frequency of 12.7 mm across the cross-section of sample 15. For example, the OH concentration is measured at a frequency of 12.7 mm across the cross-section of sample 15.

[0108] The OH (and OD) concentration of each segment 20 is measured using transmission Fourier transform infrared spectroscopy (“FTIR”). As used herein, “transmission” refers to light being directed through the glass body to be measured to determine the OH or OD concentration (rather than using light reflected from the glass body to be measured to determine the OH or OD concentration). Thus, “transmission” requires a non-scattering surface. After sample 15 is loaded into the FTIR for measurement, beam alignment and background measurements can be taken first. Then, the FTIR measures the fundamental absorption peak of OH or OD, which measures the peak height relative to a background signal, which is a straight line between points around the absorption peak. The absorption peak height is then divided by the thickness h’ of sample 15 to arrive at the absorption coefficient β OH . The OH concentration is then derived from the absorption coefficient β OH using the following equation:

[0109] C = β OH / ε x MW OH / D glass x 106

[0110] where C is the OH concentration (in ppm) of a particular segment 20, β OH is the absorption coefficient of the glass, ε is the molar absorptivity of OH at the absorption peak of 3670 cm -1 , MW OH is the molecular weight of the hydroxyl group (g / mol), and D glass is the density of the glass (g / cm 3). It should be noted that the same formula can be used to determine 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 by reference herein. As discussed above, the OH (or OD) concentration of each section 20 of the sample 15 is measured, and the measurement is taken across the entire thickness h’ of each section 20. The OH (or OD) concentration measurement is then repeated across all sections 20 of the sample 15.

[0111] The OH (and OD) concentration of one or more sections 20 can be different than one or more other sections 20. However, in embodiments, each section has substantially the same OH (and OD) concentration regardless of where the section 20 is located on the substrate 10.

[0112] Further, an average OH (or OD) concentration along the length L’ and width w’ of the sample 15 can also be determined by averaging the OH (or OD) concentrations of the individual sections 20 together. According to embodiments disclosed herein, the average OH (and / or OD) concentration of the entire sample 15 can be in a range from about 0 ppm to about 100 ppm, or from about 1 ppm to about 80 ppm, or from about 2 ppm to about 60 ppm, or from about 3 ppm to about 50 ppm, or from about 4 ppm to about 40 ppm, or from about 5 ppm to about 30 ppm, or from about 1 ppm to about 25 ppm, or from about 1 ppm to about 20 ppm, or from about 1 ppm to about 15 ppm, or from about 1 ppm to about 10 ppm, or from about 1 ppm to about 8 ppm, or from about 1 ppm to about 5 ppm. In some embodiments, the average OH (and / or OD) concentration of the entire sample 15 is about 10 ppm or less, or about 8 ppm or less, or about 6 ppm or less, or 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.

[0113] In some particular embodiments, the maximum OH (and / or OD) concentration of the segments 20 can range from about 1 ppm to about 100 ppm, or from about 2 ppm to about 80 ppm, or from about 3 ppm to about 50 ppm, or from about 10 ppm to about 40 ppm, or from about 10 ppm to about 20 ppm, or from about 3 ppm to about 20 ppm, or from about 3 ppm to about 15 ppm, or from about 3 ppm to about 10 ppm, or from about 3 ppm to about 5 ppm. In some particular embodiments, the minimum OH (and / or OD) concentration of the segments 20 can 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.

[0114] The difference between the highest concentration and the lowest concentration of OH (or OD) for different segments 20 is the peak-to-valley (P-V) OH concentration. More specifically, the segment 20 having the highest OH concentration is compared to the segment 20 having the lowest OH concentration. Then, the difference between the highest OH concentration and the lowest OH concentration is calculated. This difference between the highest concentration and the lowest concentration in the sample 15 is referred to as the P-V difference in concentration. The smaller the P-V difference, the more uniform the concentration in a particular sample.

[0115] The OH (and / or OD) concentration P-V difference for the segments 20 in the sample 15 when produced using the process 100 can be 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 10 ppm or less, or about 9 ppm or less, or about 8 ppm or less, or about 7 ppm or less, or about 6 ppm or less, or 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 or less. In embodiments, the OH (and / or OD) concentration P-V difference for the segments 20 in the sample 15 ranges from about 0 ppm to about 60 ppm, or from about 0 ppm to about 50 ppm, or from about 0 ppm to about 40 ppm, or from about 0 ppm to about 30 ppm, or from about 0 ppm to about 20 ppm, or from about 0 ppm to about 10 ppm, or from about 1 ppm to about 30 ppm, or from about 1 ppm to about 25 ppm, or from about 1 ppm to about 20 ppm, or from about 1 ppm to about 15 ppm, or from about 1 ppm to about 5 ppm, or from about 1 ppm to about 3 ppm, or from about 3 ppm to about 10 ppm, or from about 5 ppm to about 10 ppm.

[0116] As discussed above, the P-V difference in OH concentration of the segments 20 is very small, providing a homogenous and uniform glass body 10. Because the P-V difference is so low, the glass body 10 will maintain its face shape in an EUV system. Further, in embodiments, the OH concentration of the segments 20 is also very low. As discussed above, the lower OH concentrations disclosed herein help to produce glass bodies with lower CTE values. In embodiments of the present disclosure, such uniform and low OH concentrations are achieved with little to no use of halides.

[0117] When produced using the process 100 disclosed herein, the average Ti02concentration of the segments 20 can be from about 1.0 wt% to about 15.0 wt%, or from about 6.0 wt% to about 12.0 wt%, or from about 6.0 wt% to about 8.5 wt%, or from about 6.0 wt% to about 8.0 wt%, or from about 6.0 wt% to about 7.5 wt%, or from about 6.0 wt% to about 7.0 wt%, or from about 6.0 wt% to about 6.8 wt%, or from about 6.0 wt% to about 6.5 wt%, or from about 6.5 wt% to about 7.5 wt%, or from about 6.5 wt% to about 7.0 wt%, as disclosed above.

[0118] Further, when produced using the process 100 disclosed herein, the average Ti02concentration of the segments 20 can be from about 1.0 wt% to about 15.0 wt%, or from about 6.0 wt% to about 12.0 wt%, or from about 6.0 wt% to about 8.5 wt%, or from about 6.0 wt% to about 8.0 wt%, or from about 6.0 wt% to about 7.5 wt%, or from about 6.0 wt% to about 7.0 wt%, or from about 6.0 wt% to about 6.8 wt%, or from about 6.0 wt% to about 6.5 wt%, or from about 6.5 wt% to about 7.5 wt%, or from about 6.5 wt% to about 7.0 wt%, as disclosed above. 3+ from about 100 ppm or lower, or from about 90 ppm or lower, or from about 80 ppm or lower, or from about 70 ppm or lower, or from about 60 ppm or lower, or from about 50 ppm or lower, or from about 40 ppm or lower, or from about 30 ppm or lower, or from about 20 ppm or lower, or from about 15 ppm or lower, or from about 10 ppm or lower, or from about 5 ppm or lower.

[0119] When produced using the process 100 disclosed herein, the Ti02concentration P-V difference for the section 20 in the sample 15 can be about 0.0200 wt% or less, or about 0.01500 wt% or less, or about 0.0100 wt% or less, or about 0.0090 wt% or less, or about 0.0080 wt% or less, or about 0.0070 wt% or less, or about 0.0060 wt% or less, or about 0050 wt% or less, or about 0.0040 wt% or less, or about 0.0035 wt% or less, or about 0.0030 wt% or less, or about 0.0025 wt% or less, or about 0.0020 wt% or less, or about 0.0015 wt% or less, or about 0.0010 wt% or less. In embodiments, the Ti02concentration P-V difference for the section 20 is in a range from about 0.0010 wt% to about 0.0050 wt%, or from about 0.0015 wt% to about 0.0045 wt%, or from about 0.0020 wt% to about 0.0040 wt%, or from about 0.0025 wt% to about 0.0035 wt%, or from about 0.0030 wt% to about 0.0050 wt%, or from about 0.0010 wt% to about 0.0030 wt%, or from about 0.0010 wt% to about 0.0025 wt%, or from about 0.0010 wt% to about 0.0020 wt%, or from about 0.0100 wt% to about 0.0500 wt%, or from about 0.0100 wt% to about 0.0400 wt%, or from about 0.0100 wt% to about 0.0300 wt%. The Ti02concentration P-V difference in the glass body 10 is very low, and thus the embodiments disclosed herein produce a homogeneous glass body 10 that not only has a uniform OH concentration, but also has a uniform Ti02concentration.

[0120] The Ti02concentration of each segment 20 is calculated based on the measured refractive index of each segment 20. As is well known in the art, the Ti02concentration in a glass body is related to the refractive index of the glass body. Thus, for the purposes of the present disclosure, the refractive index is measured to determine the Ti02concentration of the glass bodies disclosed herein. More specifically, the refractive index is measured using an optical interferometer having a working wavelength of 633 nm. Specifically, the optical interferometer is a Zygo Verifire HD by Zygo Corporation having a pixel size resolution of 270 microns and a working wavelength of 633 nm. The optical interferometer is set up such that the pixels are squares having a size of 270 microns by 270 microns, and each pixel extends through the entire thickness h' of the sample 15. The refractive index is measured at each pixel within the segment 20 and over the entire thickness of the pixel. The refractive index measured at each pixel within 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 of the segments 20 of the sample 15.

[0121] The average Ti02concentration of each segment 20 is then determined based on the average refractive index of each segment 20 using the following relationship:

[0122] 55 ppm RI = 0.0125% C Ti

[0123] where RI is the average refractive index of each segment 20, and C Ti is the average Ti02concentration (in weight %) of each segment 20. It should be noted that the above relationship assumes that the only effect on the change in refractive index comes from Ti02.

[0124] Further, the average CTE of each segment 20 is determined from the average refractive index of each segment 20 using the following relationship:

[0125] 55 ppm RI = 1 ppb / K CTE

[0126] where RI is the average refractive index of each segment 20, and CTE is the average coefficient of thermal expansion (in ppb / K) of each segment 20. It should be noted that the above relationship assumes that the only effect on the change in refractive index comes from CTE.

[0127] Additionally, the Tzc of each segment 20 is determined from the CTE of each segment 20 using the following relationship:

[0128] ΔCTE / CTE slope = ΔTzc

[0129] Where ΔCTE is the deviation of the CTE of a specific segment 20 from the average CTE of all segments 20 (in ppb / K), and the CTE slope is the slope of the CTE of all segments 20 as a function of temperature (in ppb / K). 2 (in units), and ΔTzc is the deviation (°C) of Tzc for the specific segment 20 compared to the average Tzc of all segments 20. It should be noted that the above relationship assumes that the only influence on the variation of Tzc comes from CTE.

[0130] The difference in refractive index PV between different sections 20 in the entire sample 15 can be approximately 1 × 10⁻⁶. -4 Or smaller, or about 5×10 -5 Or smaller, or about 1×10 -5 Or smaller, or about 5×10 -6 Or smaller, or about 1×10 -6 Or smaller, or about 5×10 -7 Or smaller, or about 1×10 -7 Or smaller, or about 1×10 -6 To approximately 1×10 -4 or approximately 6×10 -6 Approximately 9×10 -5 or approximately 10×10 -6 Approximately 6×10 -5 or approximately 1×10 -6 To approximately 1×10 -5 or approximately 1×10 -5 To approximately 1×10 -4 The refractive index distribution within a glass substrate is an indicator of the TiO2 concentration distribution within that substrate. Therefore, a glass substrate with a smaller refractive index (PV) difference will also have a smaller TiO2 PV difference. As discussed above, the smaller the TiO2 PV difference, the more uniform the polishing of the glass substrate.

[0131] Additionally, when produced using the processes 100 disclosed herein, the glass bodies 10 have ultra-low expansion properties that make the glass bodies suitable for use with EUV lithography applications. In embodiments, the glass bodies 10 have a CTE value at 20 °C in the range of -45 ppb / K to +20 ppb / K, or a CTE value at 20 °C of -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 in any range bounded 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 cause the shape of the glass bodies 10, whether formed as mirrors or photomasks (e.g., reflective masks), to remain substantially unchanged when heated during an EUV lithography process.

[0132] In embodiments, when produced using the processes 100 disclosed herein, the glass bodies 10 have a cross-over 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 bodies 400 have a cross-over 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 cross-over temperature is the temperature at which the CTE of the glass body 10 is exactly zero. When the glass bodies 10 are used in EUV lithography applications, it is desirable for the cross-over temperature to be within the temperatures that the glass body is expected to experience in order to minimize thermal expansion of the glass substrate during the lithography process. Designers of EUV lithography systems will calculate the optimal cross-over temperature for each glass body 10 in the system based on the thermal load, size, and heat dissipation provided by the system. The cross-over temperature of the glass bodies 10 is additionally determined by the techniques disclosed in U.S. Patent No. 10,458,936, which is incorporated by reference herein.

[0133] Additionally, when produced using the processes 100 disclosed herein, the glass bodies 10 have a CTE slope at 20 °C in the range of about 1.0 ppb / K 2 to about 2.5 ppb / K 2 , or about 1.15 ppb / K 2 to about 2.0 ppb / K 2 , or about 1.2 ppb / K 2 to about 1.9 ppb / K 2or about 1.3 ppb / K 2 or about 1.7 ppb / K 2 or about 1.6 ppb / K 2 or about 2.2 ppb / K 2 or about 1.7 ppb / K 2 or about 2.0 ppb / K 2 or about 1.8 ppb / K 2 or about 1.9 ppb / K 2 The CTE slope of the glass body 10 is the rate at which the CTE of the glass body 400 changes as a function of the temperature change of the glass body 400. When the glass body 10 is used for EUV lithography applications, it is desirable to minimize the slope of the CTE such that the thermal expansion experienced by the glass body due to temperature fluctuations of the glass body during the EUV lithography process is minimized. The CTE slope is measured by the techniques disclosed in the aforementioned U.S. Patent No. 10,458,936.

[0134] In embodiments, the fictive temperature (Tf) of the glass body 10 when produced using the process 100 disclosed herein is about 900 °C or greater, or about 910 °C or greater, or about 915 °C or greater, or about 920 °C or greater, or about 925 °C or greater, or about 930 °C or greater, or about 940 °C or greater, or about 950 °C or greater, or about 960 °C or greater, or about 970 °C or greater, or about 980 °C or greater. Additionally or alternatively, the fictive temperature (Tf) of the glass body 10 when produced using the process 100 disclosed herein is about 1500 °C or less, or about 1400 °C or less, or about 1200 °C or less, or about 1100 °C or less, or about 1000 °C or less, or about 900 °C or less.

[0135] In embodiments disclosed herein, the glass body 10 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 when produced using the process 100 disclosed herein. In particular, in embodiments disclosed herein, the glass body 10 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 when produced using the process 100 disclosed herein.

[0136] The glass body 10 can be a uniform glass with reduced or no striations when produced using the process 100 disclosed herein. Striations are periodic inhomogeneities in glass that can adversely affect the properties of the glass. More specifically, striations are formed from alternating thin layers of material in the glass that have different CTE values. As discussed above, the process 100 forms a glass substrate with a uniform CTE value throughout, and thus forms a glass substrate with reduced or no striations.

[0137] Because of the low striation content in the glass body 10, the glass body can be polished to a very low surface waviness. Polishing a glass with striations can result in uneven material removal from the glass. For example, the polishing rate of a first layer of glass material having a first CTE value can be faster 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 caused by the striations in the glass. Furthermore, in this example, the first layer can be removed from the glass at a faster rate than the second layer, even though both layers are exposed to the same polishing process. Thus, in this example, the material removal from the glass is not equal when polishing the first and second layers. This uneven material removal can result in a suboptimal surface waviness after the polishing process. Unlike this example, the produced glass body 10 has a uniform CTE value throughout the glass body. Thus, the glass body 10 can be polished to have an excellent surface waviness.

[0138] Using process 100, three exemplary glass bodies were produced utilizing the specific consolidation step of process 300 Figure 3 The first glass sample had a CTE slope of 1.987 ppb / K at 20 °C 2 and a cross-over temperature (Tzc) of 34.91 °C. The second glass sample had a CTE slope of 1.942 ppb / K at 20 °C 2 and a cross-over temperature (Tzc) of 34.39 °C. The third glass sample had a CTE slope of 2.012 ppb / K at 20 °C 2 and a cross-over temperature (Tzc) of 34.40 °C. The average CTE slope of the three glass samples was 1.98 ppb / K 2 with a standard deviation of 0.04. The average Tzc of the three glass samples was 34.57 °C with a standard deviation of 0.30.

[0139] The homogeneous and isotropic glass bodies produced herein have reduced radiation damage when exposed to a laser. When a Si02article is exposed to radiation from a short wavelength laser having a working wavelength of UV, deep UV (DUV), and vacuum UV, the radiation causes damage to a region of the article. Such lasers include, but are not limited to, lasers having a working wavelength of about 248 nm, 193 nm, 157 nm, 13.5 nm, and even shorter. One of the consequences of this radiation-induced damage is polarization-induced birefringence (PIB). As used herein, the term polarization-induced birefringence refers to the numerical difference between the peak birefringence level measured in the center 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 prior to exposure to the radiation.

[0140] PIB levels of a glass body were induced by directing a linearly polarized pulsed laser beam having a wavelength of about 193 nm and a beam diameter of about 3 mm to a fixed region of the glass body at a given fluence (expressed in µJ·cm -2 ·pulse -1 and a pulse length (typically on the order of tens of nanoseconds). After a certain number of pulses, the birefringence measurement of the center portion of the exposed region was measured. The PIB value was then calculated by subtracting the initial birefringence of the glass from the measured center birefringence. The relationship between the polarization-induced birefringence, the number of pulses, and the fluence can be tentatively described as PIB = a · N · F, where a is a sample-dependent factor, N is the number of pulses, F is the fluence, and PIB is the level of polarization-induced birefringence.

[0141] In one embodiment, the vitreous exhibits a polarization-induced birefringence of less than about 1 nm / cm when the vitreous is subjected to 5 billion pulses of a laser beam operating at about 193 nm, the laser beam having a fluence of about 500 µJ·cm -2 · pulses -1 and a pulse length of about 21 ns. In particular embodiments, the vitreous has a polarization-induced birefringence of less than about 0.5 nm / cm over an area of at least 25 cm 2 .

[0142] Another consequence of the damage to the vitreous caused by such radiation is wavefront distortion (WFD). Simply stated, wavefront distortion can be described as the distortion of a wavefront from its original or intended shape as the wavefront travels through an optical assembly. This distortion is caused by deviations or inhomogeneities within the vitreous. WFD is typically characterized by the peak-to-valley (P-V) deformation of the wavefront from its intended shape that occurs and is typically expressed in fractions of a wavelength. Such wavefront distortion can be induced when radiation from a laser or other light source produces inhomogeneities in a physical property (e.g., the density of the vitreous) upon exposure to light (e.g., a laser) (hence the terms light-induced wavefront distortion and laser-induced wavefront distortion (LIWFD)).

[0143] In one embodiment, the vitreous exhibits a light- or laser-induced wavefront distortion measured at a wavelength of 633 nm of less than about 3.0 nm / cm when the vitreous is subjected to 5 billion pulses of a laser beam operating at about 193 nm, the laser beam having a fluence of about 500 µJ·cm -2 · pulses -1 and a pulse length of about 21 ns.

[0144] According to a first aspect, a vitreous comprising titania and silica, wherein an average hydroxyl concentration of a plurality of sections of the vitreous is about 60 ppm or less, the hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy, and the plurality of sections comprises each adjacent section over a length and a width of the vitreous, the length is about 25 mm or more and the width is about 25 mm or more, and a chlorine concentration of the vitreous is about 5 ppm or less.

[0145] According to a second aspect, the vitreous of the first aspect, wherein the chlorine concentration is about 1 ppm or less.

[0146] According to a third aspect, the vitreous of the first aspect, wherein a halogen concentration of the vitreous is about 5 ppm or less.

[0147] According to a fourth aspect, the vitreous of the first aspect, wherein the average hydroxyl concentration of the plurality of sections of the vitreous is about 20 ppm or less.

[0148] According to a fifth aspect, the glass body of the fourth aspect, wherein the average hydroxyl concentration of the plurality of segments of the glass body is about 5 ppm or less.

[0149] According to a sixth aspect, the glass body of the first aspect, wherein the peak-to-valley value of the hydroxyl concentration of the plurality of segments is about 5 ppm or less.

[0150] According to a seventh aspect, the glass body of the sixth aspect, wherein the peak-to-valley value of the hydroxyl concentration of the plurality of segments is about 2 ppm or less.

[0151] According to an eighth aspect, the glass body of the seventh aspect, wherein the peak-to-valley value of the hydroxyl concentration of the plurality of segments is about 1 ppm or less.

[0152] According to a ninth aspect, the glass body of the first aspect, wherein the average titania concentration of the plurality of segments of the glass body is about 6.0 wt% to about 8.0 wt%.

[0153] According to a tenth aspect, the glass body of the ninth aspect, wherein the average titania concentration of the plurality of segments of the glass body is about 7.0 wt% to about 8.0 wt%.

[0154] According to an eleventh aspect, the glass body of the first aspect, wherein the peak-to-valley value of the titania concentration of the plurality of segments is about 0.0010 wt% to about 0.0050 wt%.

[0155] According to a twelfth aspect, the glass body of the first aspect, wherein the peak-to-valley value of the titania concentration of the plurality of segments is about 0.0100 wt% to about 0.0500 wt%.

[0156] According to a thirteenth aspect, the glass body of the first aspect, wherein the peak-to-valley value of the refractive index of the plurality of segments of the glass body is about 1 x 10 -5 or less.

[0157] According to a fourteenth aspect, the glass body of the thirteenth aspect, wherein the peak-to-valley value of the refractive index of the plurality of segments of the glass body is about 1 x 10 -6 to about 1 x 10 -4 .

[0158] According to a fifteenth aspect, the glass body of the first aspect, wherein the cross-over temperature (Tzc) of the glass body is about 20 °C to about 60 °C.

[0159] According to a sixteenth aspect, the glass body of the first aspect, wherein the length is about 50 mm or greater and the width is about 50 mm or greater.

[0160] According to a seventeenth aspect, the glass body of the sixteenth aspect, wherein the length is about 150 mm or more, and the width is about 150 mm or more.

[0161] According to an eighteenth aspect, the glass body of the first aspect, wherein the length (L") and the width (W") of each segment are about 12.7 mm.

[0162] According to a nineteenth aspect, the glass body of the first aspect, wherein the glass body is a photomask.

[0163] According to a twentieth aspect, a method comprising: compacting a titania-doped silica soot into a molded soot body such that a density of the titania-doped silica soot is about 0.65 g / cm 3 or more; consolidating the molded soot body by heating the molded soot body; and annealing the consolidated glass body, wherein a chlorine concentration of the consolidated and annealed glass body is about 5 ppm or less.

[0164] According to a twenty-first aspect, the method of the twentieth aspect, wherein consolidating the molded soot body comprises flowing a CO-containing gas into a consolidation furnace while heating the molded soot body to a first temperature (T1).

[0165] According to a twenty-second aspect, the method of the twenty-first aspect, further comprising increasing a temperature from the first temperature (T1) to a second temperature (T2) at a rate of about 10 °C / hr or more, the second temperature (T2) being higher than the first temperature (T1).

[0166] According to a twenty-third aspect, the method of the twenty-second aspect, 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.

[0167] According to a twenty-fourth aspect, the method of the twentieth aspect, wherein consolidating the molded soot body comprises flowing an O2-containing gas and / or a CO2-containing gas into a consolidation furnace constructed of graphite while heating the molded soot body to a first temperature (T1).

[0168] According to a twenty-fifth aspect, the method of the twentieth aspect, wherein the titania-doped silica soot comprises carbon, and consolidating the molded soot body further comprises flowing an O2-containing gas and / or a CO2-containing gas into a consolidation furnace while heating the molded soot body to a first temperature (T1).

[0169] According to a twenty-sixth aspect, the method of the twentieth aspect, wherein consolidating the molded soot body comprises passing a gas comprising halogen and O2 into a consolidation furnace while heating the molded soot body to a first temperature (T1), the ratio (X) of the partial pressure of halogen in the gas to the partial pressure of O2 in the gas is defined as:

[0170] X = [partial pressure of halogen] 2 / [partial pressure of O2]

[0171] wherein X is about 5 x 10 -6 atm to about 1.0 atm, and both the partial pressure of the halogen and the partial pressure of O2 are in units of atm.

[0172] According to a twenty-seventh aspect, the method of the twenty-sixth aspect, wherein X is about 1 x 10 -5 atm to about 0.5 atm.

[0173] According to a twenty-eighth aspect, the method of the twentieth aspect, wherein annealing the consolidated glass body comprises heating the consolidated glass body to a first fictive temperature (T 1f ) such that the viscosity of the consolidated glass body is less than about 10 13 poise, then equilibrating the consolidated glass body at the first fictive temperature (T 1f ) for a predetermined period of time, and then quenching the consolidated glass body to a second fictive temperature (T 2f ).

[0174] According to a twenty-ninth aspect, the method of the twenty-eighth aspect, wherein the first fictive temperature (T 1f ) is about 825 °C or greater.

[0175] According to a thirtieth aspect, the method of the twenty-ninth aspect, wherein the first fictive temperature (T 1f ) is about 900 °C or greater.

[0176] According to a thirty-first aspect, the method of the twenty-eighth aspect, wherein the second fictive temperature (T 2f ) is about 25 °C to about 600 °C.

[0177] According to a thirty-second aspect, the method of the twenty-eighth aspect, wherein the predetermined period of time is about 12 hours or greater.

[0178] According to a thirty-third aspect, the method of the twentieth aspect, wherein the chlorine concentration is about 1 ppm or less.

[0179] According to a thirty-fourth aspect, the method of the twentieth aspect, wherein the halogen concentration of the consolidated and annealed glass body is about 5 ppm or less.

[0180] According to a thirty-fifth aspect, the method of the twentieth aspect, wherein an average hydroxyl concentration of a plurality of segments of the consolidated and annealed glass body is about 60 ppm or less, the hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy, and the plurality of segments includes each adjacent segment over a length and a width of the glass body, the length is about 25 mm or more and the width is about 25 mm or more.

[0181] According to a thirty-sixth aspect, the method of the thirty-fifth aspect, wherein the average hydroxyl concentration of the plurality of segments of the glass body is about 10 ppm or less.

[0182] According to a thirty-seventh aspect, the method of the thirty-fifth aspect, wherein a peak-to-valley value of the hydroxyl concentration of the plurality of segments is about 5 ppm or less.

[0183] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

Claims

1. A vitreous body comprising: Titanium dioxide and silicon dioxide, in: The average hydroxyl concentration of multiple segments of the vitreous body is from about 0 ppm to about 100 ppm, and the peak and trough values ​​of the hydroxyl concentration of the multiple segments are about 60 ppm or less. The hydroxyl concentration is measured using transmission Fourier transform infrared spectroscopy. The multiple segments include each adjacent segment in the length and width of the vitreous body, the length being about 25 mm or longer and the width being about 25 mm or wider. The chlorine concentration of the vitreous body is about 100 ppm or lower.

2. The vitreous body according to claim 1, wherein the chlorine concentration is about 50 ppm or lower.

3. The vitreous body according to claim 1 or claim 2, wherein the halogen concentration of the vitreous body is about 5 ppm or lower.

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

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

6. The vitreous body according to any one of claims 1 to 5, wherein the peak-to-trough value of the hydroxyl concentration in the plurality of segments is about 40 ppm or lower.

7. The vitreous body according to claim 6, wherein the peak-to-valley value of the hydroxyl concentration in the plurality of segments is about 20 ppm or lower.

8. The vitreous body according to claim 7, wherein the peak-to-valley value of the hydroxyl concentration in the plurality of segments is about 10 ppm or lower.

9. The vitreous body according to any one of claims 1 to 8, wherein the average titanium dioxide concentration of the plurality of segments of the vitreous body is from about 6.0% by weight to about 8.0% by weight.

10. The vitreous body of claim 9, wherein the average titanium dioxide concentration of the plurality of segments of the vitreous body is from about 7.0% to about 8.0% by weight.

11. The vitreous body according to any one of claims 1 to 10, wherein the peak-to-valley value of the titanium dioxide concentration in the plurality of segments is from about 0.0010% by weight to about 0.0050% by weight.

12. The vitreous body according to any one of claims 1 to 11, wherein the peak-to-valley value of titanium dioxide concentration in the plurality of segments is from about 0.0015% by weight to about 0.0045% by weight.

13. The vitreous body according to any one of claims 1 to 12, wherein the refractive index peak-to-valley value of the plurality of segments of the vitreous body is about 1 × 10⁻⁶. -5 Or smaller.

14. The vitreous body according to claim 13, wherein the refractive index peak-to-valley value of the plurality of segments of the vitreous body is about 1 × 10⁻⁶. -6 To approximately 1×10 -4 .

15. The vitreous body according to any one of claims 1 to 14, wherein the cross temperature (Tzc) of the vitreous body is from about 20°C to about 60°C.

16. The vitreous body according to any one of claims 1 to 15, wherein the length is about 50 mm or longer, and the width is about 50 mm or wider.

17. The vitreous body of claim 16, wherein the length is about 150 mm or longer, and the width is about 150 mm or wider.

18. The vitreous body according to any one of claims 1 to 17, wherein the length (L) and width (W) of each segment are both about 12.7 mm.

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

20. A method comprising: Titanium dioxide-doped silica dust was pressed into a molded dust mass, such that the density of the titanium dioxide-doped silica dust was approximately 0.50 g / cm³. 3 Or larger; The molded fume body is solidified by heating; and The solidified glass is then annealed. The chlorine concentration in the consolidated and annealed glass is approximately 100 ppm or lower.

21. The method of claim 20, wherein solidifying the molded dust body comprises passing CO-containing gas into a solidification furnace while heating the molded dust body to a first temperature (T1).

22. The method of claim 21, further comprising increasing the temperature from the first temperature (T1) to a second temperature (T2) at a rate of about 10°C / hour or higher, the second temperature (T2) being higher than the first temperature (T1).

23. The method of claim 22, 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.

24. The method of claim 20, wherein the solidification of the molded dust body is performed by passing an O2-containing gas and / or a CO2-containing gas through a solidification furnace made of graphite, while the molded dust body is heated to a first temperature (T1).

25. The method of claim 20, wherein the titanium dioxide-doped silica fume contains carbon, and the solidification of the molded fume body is further comprising passing an O2-containing gas and / or a CO2-containing gas through a solidification furnace while heating the molded fume body to a first temperature (T1).

26. The method according to claim 20, wherein solidifying the molded dust mass comprises passing a halogen- and O2-containing gas through a solidification furnace while heating the molded dust mass to a first temperature (T1), wherein the ratio (X) of the partial pressure of halogen in the gas to the partial pressure of O2 in the gas is defined as: X = [Partial pressure of halogen] 2 / [partial pressure of O2], Where X is approximately 5 × 10 -6 The partial pressure of the halogen is approximately 1.0 atm to about 1.0 atm, and the partial pressure of the halogen and the partial pressure of O2 are both in atm.

27. The method of claim 26, wherein X is approximately 1 × 10⁻⁶. -5 atm to approximately 0.5 atm.

28. The method according to any one of claims 20 to 27, wherein annealing the consolidated glass comprises heating the consolidated glass to a first hypothetical temperature (T). 1f This results in the viscosity of the solidified glass being less than about 10. 13 Po, then the solidified glass body is placed at the first hypothetical temperature (T). 1f The solidified glass is then quenched to a second hypothetical temperature (T) after a predetermined time period of equilibration. 2f ).

29. The method of claim 28, wherein the first hypothetical temperature (T) 1f The temperature is approximately 825°C or higher.

30. The method of claim 29, wherein the first hypothetical temperature (T) 1f The temperature is approximately 900°C or higher.

31. The method of claim 28, wherein the second hypothetical temperature (T) 2f The temperature ranges from approximately 25°C to approximately 600°C.

32. The method of claim 28, wherein the predetermined time period is about 12 hours or longer.

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

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

35. The method according to any one of claims 20 to 34, wherein the average hydroxyl concentration of the plurality of segments of the consolidated and annealed glass body is from about 0 ppm to about 100 ppm, the hydroxyl concentration being measured using transmission Fourier transform infrared spectroscopy, and the plurality of segments comprising each adjacent segment in length and width of the glass body, the length being about 25 mm or longer and the width being about 25 mm or wider.

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

37. The method of claim 35, wherein the peak-to-valley values ​​of the hydroxyl concentration in the plurality of segments are about 40 ppm or lower.

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