Titania-silica glass with multiple compositional variation sections

Abstract

A titania and silica glass body comprising a first glass section having a crossover temperature of approximately 10°C to approximately 60°C, and a second glass section having an average striation height of approximately 10 microns or less, wherein the average striation height of the second glass section is smaller than the average striation height of the first glass section, and the first and second glass sections form a single monolithic glass body.

Description

[Technical Field]

[0001] This application claims priority under § 120 of U.S. Patent Act to U.S. Provisional Application No. 63 / 521,766, filed on 19 June 2023, and the contents of this Provisional Application are relied upon and incorporated herein by reference in their entirety.

[0002] field This disclosure relates to titania-silica glass having multiple compositional variation sections and a method for producing the same, and more specifically, to titania-silica glass having at least two sections having different striation content due to those compositional variations. The manufactured glass articles may be suitable for use in extreme ultraviolet lithography applications. [Background technology]

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

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

[0005] Embodiments of the present disclosure include a method for manufacturing glass bodies that can advantageously maintain their shape during operation of an EUV lithography system. Accordingly, according to embodiments of the present disclosure, the glass bodies reduce or prevent any distortion of the wavefront characteristics of the EUV projection optical elements. Furthermore, embodiments of the present disclosure manufacture glass bodies with high polishability.

[0006] According to aspects of the present disclosure, a titania and silica glass body is disclosed, comprising a first glass section having a crossover temperature of about 10°C to about 60°C, and a second glass section having an average striation height of about 10 microns or less, wherein the average striation height of the second glass section is smaller than the average striation height of the first glass section, and the first and second glass sections form a single monolithic glass body.

[0007] A method for producing a glass body is disclosed according to aspects of the present disclosure, the method comprising: discharging titania-silica soot particle droplets from a furnace burner in a collection cup, the titania-silica soot particle droplets being discharged in a laydown pattern in the collection cup to form a first glass section; modifying the laydown pattern of the titania-silica soot particle droplets to form a second glass section; and solidifying the titania-silica soot particle droplets in the collection cup, wherein the first and second glass sections comprise a single monolithic glass body, and the average striation height of the second glass section is less than the average striation height of the first glass section.

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

[0009] [Figure 1A] This specification shows a composite glass body having first and second glass sections according to embodiments disclosed herein. [Figure 1B] Figure 1A shows a composite glass body having individual deposit layers according to an embodiment disclosed herein. [Figure 2A] This is a schematic illustrative diagram of a system for manufacturing the glass body shown in Figure 1A, according to embodiments disclosed herein. [Figure 2B] Figure 2A shows an enlarged schematic view of the burner and collection cup of the system according to an embodiment disclosed herein. [Figure 2C] The vibration laydown patterns using the systems shown in Figures 2A and 2B, according to embodiments disclosed herein, are shown. [Figure 3] This is a plot of light delay against the length of glass, according to embodiments disclosed herein. [Figure 4A]An exemplary glass body having a sample therein, according to embodiments disclosed herein, is shown. [Figure 4B] A cross-sectional view of the sample of the glass body of FIG. 4A, according to embodiments disclosed herein, is shown. [Figure 4C] Another cross-sectional view of the sample of the glass body of FIG. 4A having an outer peripheral edge, according to embodiments disclosed herein, is shown.

MODE FOR CARRYING OUT THE INVENTION

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

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

[0012] As used herein, the term "glass composite material" refers to a glass body having at least two glass sections with different compositional variations such that each of the at least two glass sections remains as a distinct and distinguishable section within the finished structure of the glass body. By having different compositional variations, the at least two glass sections include variations in at least one compositional element, such as variations in the deposition of their compositional elements. However, as further discussed below, the finished glass body (having at least two glass sections) is a single monolithic body. Thus, the at least two glass sections are not joined together to manufacture the finished glass body.

[0013] Figure 1A shows an exemplary glass body 10 manufactured according to embodiments disclosed herein, suitable for use in EUV lithography applications. The glass body 10 is a glass composite material comprising titania-doped silica glass. As shown in Figure 1A, the glass body 10 comprises at least a first glass section 20 and a second glass section 30. The first glass section 20 includes a compositional variation of at least one compositional element that differs from that of the second glass section 30. In some embodiments, as will be further discussed below, due to the different compositional variation, the first glass section 20 has relatively uniform thermal expansion properties than the second glass section 30, thereby allowing the first glass section 20 to maintain its shape and appearance even when exposed to the demanding thermal loads required by the EUV system. The second glass section 30, due to the different compositional variation, has higher polishing capability and can therefore be polished to a smoother finish.

[0014] EUV lithography technology relies on an optical projection system to expose reflective mirrors and / or photomasks to EUV light, so that the light reflected from the mirrors and / or photomasks is directed onto a thin photosensitive layer deposited on the surface of a semiconductor wafer. This technique is commonly used in the manufacturing process of semiconductor devices. EUV lithography systems operate at a wavelength of light of approximately 13.5 nm. This very short wavelength presents several challenges in the design of EUV systems. For example, the reflective coating on the mirrors and / or photomasks in an EUV system cannot reflect all light at such low wavelengths. Approximately 30% of the light is absorbed by the reflective coating rather than reflected. The absorbed light generates undesirable heat in the glass body, causing it to thermally expand or contract. Such changes in the glass body can then deform the reflective coating on the glass body, potentially leading to wavefront distortion of the reflected light. Wavefront distortion can lead to a decrease in the resolution of the EUV system and errors in the patterns formed on the photosensitive layer.

[0015] As is known in the art, the coefficient of thermal expansion (CTE) is a material property of glass that indicates the degree to which a material expands (changes shape) when heated. Therefore, a lower CTE value is advantageous because the glass body does not change shape when exposed to different temperature environments, which is beneficial in lithography applications, as discussed above. Furthermore, a glass body with an overall uniform CTE value expands uniformly when heated. It is beneficial for glass bodies in an EUV system to contain both a uniform CTE value and a low CTE value. The first section 20 of the glass body 10 contains such a uniform and low CTE value. Specifically, the first glass section 20 of the glass body 10 contains a uniform expansion property in the radial direction (length direction) of the glass body. However, one consequence of the uniform radial expansion property of the first glass section 20 is that this glass section contains striations. As is known in the art, striations are compositional heterogeneity in the axial direction of the glass body. Therefore, the first glass section 20 includes radial uniformity but does not include such axial uniformity.

[0016] Streaks can be a result of thermal fluctuations in glass as fine particles are deposited. The occurrence of striations in glass results in thin, alternating layers of glass with different CTE values, and therefore alternating planes of compression and tension within each layer. The presence of striations in glass can affect the surface finish of the glass at the angstrom-rootmin square (rms) level, which can negatively impact the polishability of the glass. More specifically, polished glass containing striations can result in uneven material removal, which in turn leads to increased surface roughness. This can be problematic for demanding applications such as EUV lithography articles. For example, polished glass containing striations can result in a mid-frequency surface structure on the glass, which can cause image degradation, for instance, if the glass is used as a mirror in an EUV lithography projection system.

[0017] The glass body 10 therefore comprises a second glass section 30, which includes a reduction in striations compared to the first glass section 20. Thus, the second glass section 30 has much better polishing ability than the first section 20, and for this reason, the second glass section 30 can be polished to a smoother surface with lower surface roughness. Embodiments of the present disclosure include a glass body 10 comprising both a first glass section 20 having advantageous uniform expansion properties and a second glass section 30 having advantageous polishing properties within a monolithic glass body. In embodiments, the second glass section 30 is removed (either completely or partially) by machining and / or polishing of the glass. With both the first glass section 20 and the second glass section 30, the glass body 10 can have advantageous radial uniform expansion properties while being polishable to the strict smoothness required for EUV applications. Furthermore, the glass body 10 is a monolithic body, thus avoiding the time and cost of bonding two different glass sections.

[0018] Referring again to Figure 1A, the glass body 10 is a boule and may include a length L, a width W, and a height H. In embodiments, the length L and width W of the glass body 10 are, respectively, about 20 mm to about 2000 mm, or about 40 mm to about 1500 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. The length L and width W may be the same as or different from each other. Furthermore, in some embodiments, the height H of the glass body 10 is approximately 50 mm to approximately 500 mm, or approximately 60 mm to approximately 400 mm, or approximately 80 mm to approximately 200 mm, or approximately 100 mm to approximately 200 mm, or approximately 250 mm to approximately 500 mm, or approximately 250 mm to approximately 400 mm, or approximately 250 mm to approximately 300 mm, or approximately 200 mm to approximately 500 mm, or approximately 200 mm to approximately 400 mm, or approximately 200 mm to approximately 300 mm. However, it should be noted that the length L, width W, and height H of the glass body 10 may 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 of the glass body 10, while in other embodiments, the height H is greater than the length L.

[0019] In the embodiment, the glass body 00 has a mass of about 20 kg or more, or about 30 kg or more, or about 50 kg or more, or about 100 kg or more, or about 150 kg or more, or about 200 kg or more, or about 300 kg or more, or about 400 kg or more, or about 500 kg or more. Although Figure 1A depicts the glass body 10 as a rectangle, the glass body 10 is intended to have other shapes, such as circular or elliptical. The glass body 10 may be asymmetrical. It is also intended that one or more surfaces of the glass body 10 are curved (e.g., concave or convex).

[0020] Furthermore, the first glass section 20 has a height H f The second glass section 30 has a height H sIt has the following characteristics. Note that the length and width of the first glass section 20 and the second glass section 30 are the same as the length L and width W of the glass body 10. In this embodiment, the height H of the first glass section 20 f This is approximately 60% or more, or approximately 70% or more, or approximately 80% or more, or approximately 90% or more, or approximately 95% or more, or approximately 99% or more of the total height H of the glass body 10. Therefore, the height H of the first glass section 20 f The height H of the second section 30 s It is possible. Height H of the first glass section 20. f and the height H of the second glass section 30 s The sum of these may be equal to the total height H of the glass body 10 (therefore, the glass body 10 does not contain any other members along its height H). In this embodiment, the height H of the second glass section 30 s These ranges from approximately 1mm to 250mm, or 2mm to 200mm, or 4mm to 150mm, or 6mm to 100mm, or 8mm to 10mm to 75mm, or 15mm to 50mm, or 20mm to 35mm, or 25mm to 125mm, or 50mm to 100mm.

[0021] As discussed above, the glass body 10 may be a monolithic member such that the first glass section 20 and the second glass section 30 are not joined together. Instead, they consist of the same integral member. Therefore, no seal is formed between the first glass section 20 and the second glass section 30, or there is no seal at all. Such a seal would be formed separately and then between the two glass sections that are joined together, thus creating a seal plane at the joint interface. However, embodiments of the present disclosure do not include such a seal plane.

[0022] It should be noted that embodiments of the present disclosure also include the glass body 10 comprising one or more additional glass sections in addition to the first glass section 20 and the second glass section 30. In such embodiments, the glass body 10 still comprises the first and second glass sections 20, 30 and a monolithic (integrated member) formed from the additional glass sections.

[0023] Figure 1A shows a distinct and clear boundary line between the first glass section 20 and the second glass section 30, but it should be noted that the boundary may not actually be so. For example, the boundary between the first glass section 20 and the second glass section 30 may sway or vibrate. In some embodiments, the boundary between these two sections may be a slope, such that the first glass section 20 gradually transitions into the second glass section 30.

[0024] Both the first glass section 20 and the second glass section 30 contain titania-doped silica glass. The silica concentration in each of the first glass section 20 and the second glass section 30 is approximately 80% by weight or more, or approximately 85% by weight or more, or approximately 90% by weight or more, or approximately 92% by weight or more, or approximately 95% by weight or more, or approximately 97% by weight or more, or approximately 98% by weight or more, or approximately 99% by weight or more, or approximately 85% by weight to approximately 97% by weight, or approximately 90% by weight to approximately 95% by weight. The titania concentration in each of the first glass section 20 and the second glass section 30 is approximately 1.0 wt% to approximately 15.0 wt%, or approximately 6.0 wt% to approximately 12.0 wt%, or approximately 6.0 wt% to approximately 8.5 wt%, or approximately 6.0 wt% to approximately 8.0 wt%, or approximately 6.0 wt% to approximately 7.5 wt%, or approximately 6.0 wt% to approximately 7.0 wt%, or approximately 6.0 wt% to approximately 6.8 wt%, or approximately 6.0 wt% to approximately 6.5 wt%. The first glass section 20 may have different concentrations of silica and / or titania than the second glass section 30.

[0025] Both the first section 20 and the second section 30 contain a CTE of approximately -30 ppb / °C to approximately +30 ppb / °C within a temperature range of 15°C to 30°C. In some embodiments, the CTE is approximately -10 ppb / °C to approximately +10 ppb / °C within a temperature range of 15°C to 30°C, or approximately -5 ppb / °C to approximately +5 ppb / °C within a temperature range of 15°C to 30°C, or approximately -2 ppb / °C to approximately +2 ppb / °C within a temperature range of 15°C to 30°C, or approximately -1 ppb / °C to approximately 1 ppb / °C within a temperature range of 15°C to 30°C, or approximately 0 ppb / °C within a temperature range of 15°C to 30°C. The CTE of the first glass section 20 may be the same as or different from the CTE of the second glass section 30. Such ultra-low CTE values ​​at room temperature (or approximately room temperature) allow the shape of the glass body 10 to remain substantially constant during heating in the EUV lithography process, whether formed on a mirror or photomask (such as a reflective mask). For the purposes disclosed herein, the CTE was measured using a Zygo optical interferometer (specifically, a Zygo MST HDX with a 4-inch aperture).

[0026] In embodiments, both the first glass section 20 and the second glass section 30 include a crossover temperature (Tzc) in the range of about 10 °C to about 60 °C, or about 20 °C to about 40 °C, or about 20 °C to about 38 °C, or about 22 °C to about 38 °C. In embodiments, the first glass section 20 and the second glass section 30 include a crossover temperature of about 20 °C to about 60 °C, or about 25 °C to about 55 °C, or about 30 °C to about 50 °C, or about 35 °C to about 45 °C, or about 40 °C to about 45 °C, or about 20 °C to about 45 °C, or about 20 °C to about 40 °C, or about 10 °C to about 50 °C. The crossover temperature of the first glass section 20 can be the same as or different from the crossover temperature of the second glass section 30. The crossover temperature is the temperature at which the CTE of the glass is exactly zero. When the glass body 10 is used for EUV lithography applications, in order to minimize the thermal expansion of the glass substrate during the lithography process, the crossover temperature ideally falls within the temperature that the glass body is expected to experience. The designer of the EUV lithography system calculates the optimal crossover temperature for each glass body 10 within the system based on the thermal load, size, and heat removal rate provided by the system. The crossover temperature of the glass body 10 is additionally determined by the techniques disclosed in U.S. Patent No. 10,458,936, which is incorporated herein by reference.

[0027] Furthermore, the first glass section 20 and the second glass section 30 each have a value 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 2 or about 1.3 ppb / K 2 to about 1.7 ppb / K 2 or about 1.6 ppb / K 2 to about 2.2 ppb / K 2 or about 1.7 ppb / K 2 to about 2.0 ppb / K 2, or approximately 1.8 ppb / K 2 ~Approx. 1.9ppb / K 2 The CTE slope is the rate of change of the CTE of the glass as a function of the temperature of the glass. When the glass body 10 is used for EUV lithography applications, the CTE slope is ideally minimized to minimize the thermal expansion of the glass body due to temperature fluctuations during the EUV lithography process. The CTE slope is additionally measured by the technique disclosed in U.S. Patent No. 10,458,936.

[0028] The first glass section 20 and the second glass section 30 have similar chemical compositions, but these sections contain different compositional variations. Specifically, the titania deposits vary between the first glass section 20 and the second glass section 30, which is a result of different processes that form these different glass sections. The first glass section 20 can be formed by a deposition process that produces a relatively thick titania deposit layer (along the height H) compared to the second glass section 30. As shown in Figure 1B, each individual titania deposit layer 22 of the first glass section 20 is thicker than each individual titania deposit layer 32 of the second glass section 30. The relatively thick deposit layers 22 of the first glass section 20 allow for a more uniform titania concentration along the length L of each layer, resulting in higher CTE uniformity along the length L. Thus, the layers 22 can expand and contract uniformly so that the first glass section 20 maintains its shape when heated in an EUV system. However, the first glass section 20 contains relatively more striations than the second glass section 30.

[0029] As described above, striations are variations in the homogeneity of the glass body and negatively affect the polishability of the glass. Specifically, striations are heterogeneities between different sedimentary layers. For example, a first sedimentary layer may have a slightly different concentration of titania than a second and adjacent sedimentary layer, which results in heterogeneity between these layers. Therefore, striations are heterogeneities along the height H of the glass body 10.

[0030] The second glass section 30 comprises a relatively thinner titania deposit than the first glass section 20. Due to the thinner layer, the titania compounds within each individual deposit 32 diffuse together. The relatively thin deposit 32 within the second glass section 30 allows for such diffusion. Note that such diffusion does not occur in relatively thick deposits. Because the titania compounds diffuse together between the different deposit 32 of the second glass section 30, these different deposit 32 have a very uniform titania concentration between the different layers, resulting in a very low striation content. In other words, each of the individual deposit 32 within the second glass section 30 contains the same (or nearly the same) concentration of titania. Therefore, the second glass section 30 has very high polishing ability.

[0031] The second glass section 30 contains a reduced striation content compared to the first glass section 20, but it should be noted that the second glass section 30 is not as uniform across the length L of each deposit layer. Therefore, as discussed above, the first glass section 20 has a more uniform titania concentration across the length L of each layer, while the second glass section 30 has a more uniform titania concentration across different layers. As a result, the first glass section 10 has higher CTE uniformity along the length L of the glass body 10 (to maintain its shape when heated), while the second glass section 30 is polished to a higher degree of smoothness.

[0032] As discussed above, the second glass section 30 contains fewer striae than the first glass section 20. The content or amount of striae in each section is measured by the size of the striae, including the size of the striae (e.g., average height) and the spacing between adjacent striae. The size of the striae includes the height of the striae measured along the height H of the glass body 10, as disclosed herein. The spacing between adjacent striae includes the spacing between adjacent striae in the direction along the length L of the glass body 10, as disclosed herein. The second glass section 30 contains striae with reduced size (average height) and reduced spacing between adjacent striae compared to the first section 20. Therefore, the second glass section 30 is polished more evenly along its length compared to the first glass section 20. It should be noted that smaller striae that are closer to each other (and therefore have less titania heterogeneity) facilitate the diffusion of titania compounds together, and for this reason, these striae are no longer detectable compared to larger striae that are further apart.

[0033] In the embodiment, the average striation height in the first glass section 20, and the average striation height over the entire length of the first glass section 20, are in the range of about 10 microns to about 30 microns, or about 12 microns to about 28 microns, or about 15 microns to about 25 microns, or about 28 microns to about 22 microns, or about 24 microns to about 26 microns.

[0034] Conversely, the average striation height of the second glass section 30 is smaller than the average striation height of the first glass section 20. In some embodiments, the average striation height of the second glass section 30 is about 1 micron or less, or about 0.75 microns or less, or about 0.50 microns or less, or about 0.25 microns or less, or about 0.10 microns or less, or about 80 nm or less, or about 60 nm or less, or about 50 nm or less, or about 40 nm or less, or about 20 nm or less, or about 10 nm or less, or about 5 nm or less, or about 1 nm or less. In some embodiments, the second glass section 30 does not contain striations (or the striations are so small that they are undetectable), and therefore the average striation height of the second glass section 30 is 0.00 nm.

[0035] Furthermore, in the embodiment, the average spacing between adjacent striations within the first glass section 20, and the average spacing over the entire length of the first glass section 20, is approximately 1.00 mm or less, or approximately 0.80 mm or less, or approximately 0.75 mm or less, or approximately 0.60 mm or less, or approximately 0.50 mm or less, or approximately 0.55 mm or less, or approximately 0.50 mm or less, or approximately 0.45 mm or less, or approximately 0.40 mm or less, or approximately 0.35 mm or less, or approximately 0.30 mm or less, or approximately 0.25 mm or less, or approximately 0.20 mm or less, or approximately 0.15 mm or less, or approximately 0.1 mm or less, or approximately 75 microns or less, or approximately 50 microns or less, or approximately 25 microns or less, or approximately 10 microns or less. In some embodiments, the spacing in the first glass section 20 is in the range of about 0.10 mm to about 0.55 mm, or about 0.15 mm to about 0.50 mm, or about 0.2 mm to about 0.40 mm, or about 0.25 mm to about 0.35 mm, or any combination of these endpoints.

[0036] Conversely, the average spacing between adjacent striae in the second glass section 30 is smaller than the average spacing between adjacent striae in the first glass section 20. In some embodiments, the average spacing between adjacent striae in the second glass section 30 is about 10 microns or less, or about 8 microns or less, or about 5 microns or less, or about 4 microns or less, or about 2 microns or less, or about 1 micron or less, or about 0.75 microns or less, or about 0.50 microns or less, or about 0.25 microns or less, or about 0.10 microns or less, or about 80 nm or less, or about 60 nm or less, or about 50 nm or less, or about 40 nm or less, or about 20 nm or less, or about 10 nm or less, or about 5 nm or less, or about 1 nm or less. In some embodiments, the second glass section 30 does not contain striae (or the striae are so small that they are undetectable), and therefore the average spacing between striae is undetectable.

[0037] As used herein, the striation height and the spacing between adjacent striations are calculated based on the concentration of titania in the glass. The concentration of titania in the glass is determined using a microprobe analyzer. Specifically, glass samples for analysis using a microprobe analyzer are first prepared as polished sections, and a conductive carbon coating is deposited on the polished surface. Electron probe microanalyzer (EPMA) analysis is performed on the glass samples using a JEOL 8500F Hyperprobe (2008) electron microprobe analyzer. This microprobe analyzer is a wavelength-dispersive spectrometer that uses a pentaerythritol (PET) diffractometer to quantify measurements from the titanium K-alpha X-ray line. To calibrate the number of Ti K-alpha X-ray measurements with a known electron beam current and time, with the spectrometer position as the peak, standards of fine TiO2 rutile morphology in a 53 mineral standard block (serial No. 99-143 from Structure Probe Inc., West Chester Pa) are used. Typical beam parameters used for analysis are a beam current of 50–100 nA and an accelerating potential of 15 keV, with an on-peak count time ranging from 10–30 seconds. The beam current and count time can be increased or decreased depending on the titanium concentration and / or accuracy required for the analysis. Line scanning or point analysis is performed on glass samples using either a focused or diffused beam, where the beam spot size is determined based on the size of the feature area of ​​interest (e.g., focused or 1 μm spot for striations, diffused 10–20 μm spot for homogeneity), and the analysis is stepped across the region of interest with a step size defined by the size of the feature area of ​​interest. The results are reported as weight percent oxide, assuming stoichiometry.

[0038] The size of the striae (average height of the striae and average spacing between adjacent striae) is directly related to the light delay of the glass body. A glass body with striae having smaller average heights and smaller spacing between adjacent striae will have a smaller light delay. Since the second glass section 30 of the glass body 10 contains striae of a relatively smaller size than the first glass section 20, the second glass section 30 of the glass body 10 has a relatively smaller light delay than the first section 20.

[0039] In some embodiments, the second glass section 30 is machined or polished from the glass body 10 before further downstream processing. The entirety of the second glass section 30 or a portion less than the entirety of the second glass section 30 may be machined or polished away. For example, the second glass section 30 may be machined or polished to a height of about 10 mm or less, or about 8 mm or less, or about 5 mm or less, or about 2 mm or less, or about 1 mm or less, or about 0.2 mm or less, or about 0.1 mm or less, or about 0.05 mm or less.

[0040] Figure 2A shows a system 100 for forming a silica-titania glass body as described herein. The system 100 comprises a source of silica precursor 120 and a source of titania precursor 130. A carrier gas 110, such as nitrogen, is introduced at or near the base of the sources of silica precursor 120 and titania precursor 130 to entrain the vapors of silica precursor 120 and titania precursor 130, and carries the vapors to a mixing manifold 150 via a distribution system 140. To prevent vapor saturation, a flow of inert gas 115 (e.g., nitrogen gas) may be brought into contact with the vaporized silica and titania precursors. The vapors of silica precursor 120 and titania precursor 130 are mixed in the mixing manifold 150 and enter a burner 160 mounted on top of a furnace 170 via a conduit 155. The burner 160 produces a burner flame 165, and the mixture is delivered to a conversion site 175, where it is converted into soot particle droplets 180. The soot particle droplets 180 are deposited in a rotating collection cup 190 and deposited on the upper surface of a molded silica-titania glass body 12 in a furnace 170, where the soot particle droplets solidify and anneal to the silica-titania glass body 10.

[0041] The soot particle droplets 180 contain silicon dioxide and titanium dioxide. More specifically, the silicon dioxide and titanium dioxide in the particle droplets are mixed at the atomic level to form Si-O-Ti bonds. Furthermore, the soot particle droplets 180 are spherical in shape with a substantially uniform distribution of SiO2 and TiO2 within the particle. The size of each soot particle droplet 180 may vary depending on the state of the burner 160, but generally, the soot particle droplets 180 have an average diameter of 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.

[0042] Silica precursor 120 may include, for example, SiCl4 and / or octamethylcyclotetrasiloxane (OMCTS). Titania precursor 130 may include, for example, TiCl4, titanium isopropoxide (TPT), titanium tetraisopropoxide (TTIP), and tetraisopropyl titanate (TIPT).

[0043] As shown in Figure 2B, soot particle droplets 185 are discharged from the burner 160 as they are burned and oxidized from the fuel / oxygen mixture in the burner 160. Specifically, soot particle droplets 180 are discharged from each burner 160 in the discharge path 250. The soot particle droplets 180 then accumulate in the collection cup 190 and deposit on the growing glass body 10. The specific discharge path 250 of the burner 160 provides a smooth and uniform deposit layer of soot particle droplets 180 in the collection cup 190.

[0044] In one embodiment, each burner 160 of the system 100 is configured to move in a vibrating pattern relative to the collection cup 190, thus creating a helical discharge path 250. In another embodiment, the collection cup 190 moves in a vibrating pattern relative to the burner 160. Soot particle droplets 180 may be discharged from the burner 160 within such discharge path 250, thereby causing the soot particle droplets to accumulate in the collection cup 190 in a helical laydown pattern, such as the helical laydown pattern 254 shown in Figure 2C. It should be noted that the helical laydown pattern may be a result of the collection cup 190 moving relative to the burner 160 (and therefore relative to the discharge path 250), or a result of the burner 160 (and thus relative to the discharge path 250) moving relative to the collection cup 190. Thus, the helical laydown pattern may have different patterns (e.g., different vibrating and helical patterns) depending on how the components move relative to each other. In some embodiments, the collection cup 190 moves relative to the burner 160 in a first vibration pattern to produce a first laydown pattern (thus creating, for example, a second glass section 30), and then modulates its movement to move relative to the burner 160 in a second vibration pattern to produce a second laydown pattern (thus creating, for example, a first glass section 20). Referring again to Figure 2B, the discharge paths 250 of each burner 160 may overlap, and therefore the helical laydown patterns deposited in the collection cup 190 may also overlap. A particular laydown pattern affects the uniformity of the produced glass body. For example, a pattern with more gaps between the laydowns of soot particle droplets 180 results in a less homogeneous glass body. A particular laydown pattern affects the uniformity of the individual deposited layers 22 and 32, referring to Figure 1B.

[0045] Figure 2B shows six burners 160, but it should be noted that system 100 may include more or fewer burners 160. For example, system 100 may have a single integrated burner 160. In other embodiments, system 100 may have, for example, two, three, four, five, ten, or twenty burners 160.

[0046] As discussed above, the first glass section 20 may contain different compositional variations from the second glass section 30 of the glass body 10. Specifically, the first glass section 20 may contain different striation content (e.g., striation size) from the second glass section 30 due to differences in titania concentration between the deposited layers of these sections. In some embodiments, the striation content is controlled by altering the vibrational laydown pattern of the soot particle droplets 180 deposited in the collection cup 190. The x and y axes of the vibrational pattern are defined by the following equations. x(t)=r1sin2πω1t+r2sin2πω2t y(t)=r1cos2πω1t+r2cos2πω2t In the formula, x(t) and y(t) represent the coordinates of the center of the glass body 10 as a function of time (t) measured in minutes. The parameters r1, r2, ω1, and ω2 represent the rotational speed (rpm) of the glass body 10 with respect to its center. These parameters are further described in U.S. Patent No. 7,053,017, which is incorporated herein by reference in whole. In embodiments, the parameters r1, r2, ω1, and ω2 are relatively high when manufacturing the second glass section 30 than when manufacturing the first glass section 20, in order to have a reduced striation content in the second glass section 30. It has been shown that increasing each of these parameters to 5.0 or greater provides a vibrational laydown pattern that results in a reduced striation content. Accordingly, embodiments of the present disclosure include r1, r2, ω1, and ω2 being less than 5.0 (or less than 5.0 and greater than 1.0) in order to manufacture the first glass section 20. Embodiments of the present disclosure further include that, in order to manufacture the second glass section 30, r1, r2, ω1, and ω2 are each 5.0 or greater (or 5.0 to 10.0, or 5.0 to 8.0).

[0047] In some embodiments, the striation content is controlled by adjusting the distance between the collection cup 190 and the burner 160, which is shown as distance A in Figure 2B. Specifically, distance A is measured from the end of the burner 160 to the bottom cavity of the collection cup 190 where the soot particle droplets 180 accumulate. Larger distances A have been shown to produce glass with reduced or relatively low striation content. Soot particle droplets traveling a relatively large distance A are typically the first soot laid during the laydown process. These droplets therefore spend a longer time at the formation temperature in the collection cup 190, which allows for increased diffusion of titania among the soot particle droplets. This, in turn, results in a more uniform distribution of titania, which provides a lower striation content. Thus, a relatively large distance A may be used to form a second glass section 30 of the glass body 10, and a relatively small distance A may be used to form a first glass section 20 of the glass body 10. Embodiments of the present disclosure include manufacturing a second glass section 30 before manufacturing a first glass section 20, so that the second glass section 30 is initially installed in the collection cup 190 before the first glass section 20.

[0048] In some embodiments, the striation content is controlled by controlling the flow of gas through exhaust ports and / or vents in the system 100. It has been shown that closing or reducing the number of vents in the system 100 results in more striation in the manufactured glass body compared to an operating system 100 having more open vents. Embodiments of the present disclosure include an operating system 100 having more open vents (e.g., six or more open vents) when manufacturing a second glass section 30 than when manufacturing a first glass section 20.

[0049] Figure 3 illustrates the optical delay of first and second glass sections 20, 30 of a glass body manufactured according to embodiments disclosed herein. Note that the size and spacing of striations in the glass are directly related to the optical delay; therefore, glass with striations that are larger in size and have increased spacing will have a greater optical delay. In Figure 3, the y-axis represents the optical delay (nm) of the glass, while the x-axis represents the length of the glass as pixels, with a pixel size of approximately 0.0085 microns per pixel. The second glass section 30 has a lower optical delay than the first glass section 20, clearly indicating that the second glass section 30 has reduced striations than the first glass section 20.

[0050] As discussed above, the titania deposits fluctuate within the first and second glass sections 20 and 30, thus creating compositional variations between these layers. The peak-to-valley (PV) of titania concentration in each glass section was measured to determine the variation in titania deposits between glass sections. The PV titania concentration is the difference between the highest and lowest concentrations of titania in the glass body. Lower PV values ​​for titania indicate a more uniform titania concentration within the glass body.

[0051] For the purposes of this disclosure, the PV titania concentration was measured by segmenting the manufactured glass body into multiple segments and measuring the titania concentration in each segment, as discussed below with reference to Figures 4A to 4C. Figure 4A shows a glass body 10 manufactured according to an embodiment disclosed herein. In the embodiment of Figure 4A, the glass body 10 includes a cylindrical member.

[0052] The glass body 10 can be sliced ​​into multiple samples within each of the first section 20 and the second section 30. Figure 4A shows exemplary samples 15 of the body 10 forming the lower portion of the body. In the embodiment of Figure 4A, the sample 15 is the lower portion of the first section 20. Each sample 15 may be considered as a body, substrate, or wafer. Each sample 15 has a length L', width W', and height H'. The body 10 includes multiple samples 15 along the height H and / or length L of the glass body 10.

[0053] Although Figure 4A depicts the sample 15 as a rectangular component with a flat surface, in some embodiments, the sample 15 may include other shapes. For example, the outer shape of the sample 15 may be circular, elliptical, or asymmetrical. Furthermore, the sample 15 may be curved to form a concave or convex structure. In some embodiments, the sample 15 includes a single deposit layer 22 in the first glass section 20, or a single deposit layer 32 in the second glass section 30.

[0054] To determine the uniformity of titania concentration throughout a sample, each sample is divided into segments along the length and width of the sample. For example, Figure 4B shows sample 15 divided into segments 14 along the cross-sectional length L' and width W' of sample 15. The concentrations of one or more components (e.g., titania) along sample 15 can then be determined for each segment 14 in order to determine the uniformity of each of these components. As will be further discussed below, the concentration of one or more components is determined throughout the entire thickness (height H') of each segment 14.

[0055] Figure 4B shows a segment 14 extending along the entire length L' and width W' of the sample 15, but it is also intended that a portion of the sample 15 containing the segment 14 may be less than the entire cross-sectional length L' and width W'. For example, as shown in Figure 4C, the sample 15 may include an outer peripheral edge 17 on which no segment 14 is formed. Thus, the outer peripheral edge 17 may be the gap between the end of the segment 14 of the sample 15 and the outer edge. In embodiments, the outer peripheral edge may extend in 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.

[0056] Segment 14 can be an adjacent segment of sample 15 that extends over a specific length and width (so that no gap is formed between adjacent segments). As discussed above, this specific length and width (over which all segments 14 extend) can be less than or equal to the length L' and width W' of sample 15. In embodiments, segment 14 is an adjacent segment (over which all segments 14 extend) such that the length and width of sample 15 are, respectively, about 25 mm or more, or about 30 mm or more, or about 40 mm or more, or about 50 mm or more, or about 60 mm or more, or about 75 mm or more, or about 100 mm or more, or about 125 mm or more, or about 150 mm or more, or about 175 mm or more, or about 180 mm or more, or about 190 mm or more, or about 200 mm or more, or about 250 mm or more.

[0057] If the sample 15 includes a flat surface, the segment 14 is formed along the flat plane, as shown in Figure 4B. However, if the sample 15 includes a concave or convex surface, the segment 14 is formed along the curved surface of the sample 15.

[0058] As shown in Figure 4B, each segment 20 has a length L'' and a width W'', each approximately 12.7 mm. However, in other embodiments, the length L'' may not be equal to the width W''. It should also be noted that in some embodiments, the length L'' and width W'' of segment 14 may be equal to the length L''' of the peripheral edge 17.

[0059] The height of each segment 14 is the height H' of the sample 15, as discussed above. Therefore, in this embodiment, the height H' is approximately 7.62 mm.

[0060] As discussed above, the concentration of one or more components can be determined within each segment 14. Therefore, for example, the concentration of titania can be determined for each adjacent segment 14 in the sample 15. If each segment 14 has a length and width of 12.7 mm, the concentrations of the components are determined at a frequency of 12.7 mm across the cross-section of the sample 15. For example, the concentration of titania is measured at a frequency of 12.7 mm across the cross-section of the sample 15.

[0061] One or more segments 14 may have a different titania concentration than one or more other segments 14. The average titania concentration along the length L' and width W' of the sample 15 can be determined by averaging the titania concentrations of the individual segments 14 together. The average titania concentration between segments 14 (in each of the first glass section 20 and the second glass section 3, as also considered above with respect to the glass body 10, is approximately 1.0 wt% to approximately 15.0 wt%, or approximately 6.0 wt% to approximately 12.0 wt%, or approximately 6.0 wt% to approximately 8.5 wt%, or approximately 6.0 wt% to approximately 8.0 wt%, or approximately 6.0 wt% to approximately 7.5 wt%, or approximately 6.0 wt% to approximately 7.0 wt%, or approximately 6.0 wt% to approximately 6.8 wt%, or approximately 6.0 wt% to approximately 6.5 wt%).

[0062] The difference between the highest and lowest concentrations of titania among different segments 14 is the PV titania concentration. More specifically, segment 14 with the highest titania concentration is compared with segment 14 with the lowest titania concentration. Then, the difference between the highest and lowest OH titania concentrations is calculated. This difference between the highest and lowest concentrations in sample 15 is called the PV difference of concentration. The smaller the PV difference, the more uniform the concentration is in a particular sample.

[0063] If sample 15 comprises a single deposit layer 22 or 32, the PV difference of titania concentration in segment 14 within sample 15 is approximately 0.0200 wt% or less, or approximately 0.01500 wt% or less, or approximately 0.0100 wt% or less, or approximately 0.0090 wt% or less, or approximately 0.0080 wt% or less, or approximately 0.0070 wt% or less, or approximately 0.0060 wt% or less, or approximately 0.0050 wt% or less, or approximately 0.0040 wt% or less, or approximately 0.0035 wt% or less, or approximately 0.0030 wt% or less, or approximately 0.0025 wt% or less, or approximately 0.0020 wt% or less, or approximately 0.0015 wt% or less, or approximately 0.0010 wt% or less. In the embodiment, if the sample 15 comprises a single deposit layer 22 or 32, the PV difference of the titania concentration of segment 14 in the sample 15 is in the range of about 0.0010 wt% to about 0.0050 wt%, or about 0.0015 wt% to about 0.0045 wt%, or about 0.0020 wt% to about 0.0040 wt%, or about 0.0025 wt% to about 0.0035 wt%, or about 0.0030 wt% to about 0.0050 wt%, or about 0.0010 wt% to about 0.0030 wt%, or about 0.0010 wt% to about 0.0025 wt%, or about 0.0010 wt% to about 0.0020 wt%. In the embodiment, the PV of the titania concentration in the deposit layer 32 of the second glass section 30 is smaller than the PV difference of the titania concentration in the deposit layer 22 of the first glass section 20. The PV difference of the titania concentration in the glass body 10 is very small, and therefore, the embodiments disclosed herein produce a homogeneous glass body 10 having a uniform concentration of titania.

[0064] If sample 15 comprises a single deposit layer 22 or 32, the PV difference in refractive index of the segment 14 across sample 15 is approximately 1 × 10⁻⁶. -4 Below, or approximately 5 x 10 -5 The following, or approximately 1 × 10 -5 Below, or approximately 5 x 10 -6 The following, or approximately 1 × 10 -6 Below, or approximately 5 x 10 -7 The following, or approximately 1 × 10 -7 The following, or approximately 1 × 10 -6 ~Approx. 1×10 -4 , or approximately 6 x 10 -6 ~Approx. 9×10 -5 , or approximately 10 x 10 -6 ~Approx. 6×10 -5 The following, or approximately 1 × 10 -6 Approximately 1×10 -5 , or approximately 1 x 10 -5 ~Approx. 1×10 -4 Therefore, the refractive index distribution within a glass substrate is an indicator of the titania concentration distribution within that glass substrate. Consequently, glass substrates with smaller PV differences in refractive index also have smaller PV differences in titania concentration. As discussed above, smaller PV differences in titania allow for more uniform polishing of the glass substrate.

[0065] Embodiments of the present disclosure also include a method for manufacturing a monolithic glass body 10 comprising a first glass section 20 and a second glass section 30 without a sealing plane between them. Thus, the monolithic glass body 10 does not have deformations that may occur in a sealing plane. Instead, the first glass section 20 and the second glass section 30 are formed sequentially from the same soot laydown process. In embodiments, the second glass section 30 is formed before the first glass section 20. In some embodiments, the glass body 10 consists of the first glass section 20 and the second glass section 30.

[0066] According to a first embodiment, a titania and silica glass body comprising a first glass section having a crossover temperature of about 10°C to about 60°C, and a second glass section having an average striation height of about 10 microns or less, wherein the average striation height of the second glass section is smaller than the average striation height of the first glass section, and the first and second glass sections form a single monolithic glass body.

[0067] According to a second embodiment, the titania and silica glass body according to the first embodiment, wherein the average striation height of the second glass section is about 1 micron or less.

[0068] According to a third embodiment, the titania and silica glass body according to the second embodiment, wherein the average striation height of the second glass section is about 50 nm or less.

[0069] According to a fourth aspect, the titania and silica glass body according to the first aspect, wherein the average striation height of the first glass section is about 1 mm or less.

[0070] According to the fifth aspect, the titania and silica glass body according to the first aspect, wherein the glass body has a titania concentration of about 6.0% by weight to about 8.5% by weight.

[0071] According to the sixth aspect, the titania and silica glass body according to the fifth aspect, wherein the titania concentration is about 6.0% by weight to about 6.8% by weight.

[0072] According to the seventh aspect, the titania and silica glass body according to the first aspect, wherein the crossover temperature is approximately 20°C to approximately 40°C.

[0073] According to the eighth aspect, the titania and silica glass body according to the first aspect, wherein the first glass section has a coefficient of thermal expansion of about -10 ppb / °C to about +10 ppb / °C within the temperature range of 15°C to 30°C.

[0074] According to the ninth aspect, the glass body is approximately 1.0 ppb / K 2 ~Approximately 2.5 ppb / K 2 A titania and silica glass body according to the first embodiment, having a gradient of CTE at 20°C in the range of .

[0075] According to the tenth embodiment, the titania and silica glass body according to the first embodiment, wherein the height of the first glass section is about 60% or more of the height of the glass body.

[0076] According to the eleventh embodiment, the titania and silica glass body according to the first embodiment, wherein the height of the second glass section is approximately 10 mm to approximately 75 mm.

[0077] According to the twelfth aspect, the titania and silica glass body according to the first aspect, wherein the average spacing between striations in the second glass section is smaller than the average spacing between striations in the first glass section.

[0078] According to the 13th embodiment, the second glass section is a titania and silica glass body according to the first embodiment, which is striation-free.

[0079] According to the 14th aspect, the first glass section comprises a titania and silica glass body according to the 13th aspect, including striations.

[0080] According to the 15th embodiment, the titania and silica glass body according to the first embodiment, wherein the glass body comprises the first glass section and the second glass section.

[0081] According to the sixteenth aspect, the titania and silica glass body according to the first aspect, wherein the glass body is a photomask or a mirror.

[0082] According to the 17th aspect, a method for producing a glass body, comprising: discharging titania-silica soot particle droplets from a furnace burner in a collection cup, wherein the titania-silica soot particle droplets are discharged in a laydown pattern in the collection cup to form a first glass section; modifying the laydown pattern of the titania-silica soot particle droplets to form a second glass section; and solidifying the titania-silica soot particle droplets in the collection cup, wherein the first glass section and the second glass section comprise a single monolithic glass body, and the average striation height of the second glass section is less than the average striation height of the first glass section.

[0083] According to the 18th aspect, the method according to the 17th aspect, wherein modifying the laydown pattern of the titania-silica soot particle droplets involves moving the collection cup relative to the burner such that the laydown pattern changes from a first helical pattern to a second helical pattern.

[0084] According to the 19th aspect, the method according to the 17th aspect, wherein modifying the laydown pattern of the titania-silica soot particle droplets is such that the titania deposit layer in the first glass section is thicker than the titania deposit layer in the second glass section.

[0085] The method according to the 17th embodiment, further comprising forming the glass body consisting of the first glass section and the second glass section without joining the first glass section to the second glass section, according to the 20th embodiment.

[0086] Those skilled in the art will see that various modifications and variations can be made to the embodiments of this disclosure without departing from the spirit and scope of this disclosure. Therefore, this disclosure is intended to encompass such modifications and variations, insofar as they remain within the scope of the appended claims and their equivalents.

Claims

1. Titania and silica glass body, A first glass section having a crossover temperature of approximately 10°C to approximately 60°C, It comprises a second glass section containing an average striation height of approximately 10 microns or less, The average striation height of the second glass section is smaller than the average striation height of the first glass section. The first glass section and the second glass section form a titania and silica glass body, which together form a single monolithic glass body.

2. The titania and silica glass body according to claim 1, wherein the average striation height of the second glass section is about 1 micron or less.

3. The titania and silica glass body according to claim 2, wherein the average striation height of the second glass section is about 50 nm or less.

4. The titania and silica glass body according to any one of claims 1 to 3, wherein the average striation height of the first glass section is about 1 mm or less.

5. The titania and silica glass body according to any one of claims 1 to 4, wherein the glass body has a titania concentration of about 6.0% by weight to about 8.5% by weight.

6. The titania and silica glass body according to claim 5, wherein the titania concentration is approximately 6.0% by weight to approximately 6.8% by weight.

7. The titania and silica glass body according to any one of claims 1 to 6, wherein the crossover temperature is approximately 20°C to approximately 40°C.

8. The titania and silica glass body according to any one of claims 1 to 7, wherein the first glass section has a coefficient of thermal expansion of about -10 ppb / °C to about +10 ppb / °C in a temperature range of 15°C to 30°C.

9. The glass body is approximately 1.0 ppb / K ２ ~Approximately 2.5 ppb / K ２ A titania and silica glass body according to any one of claims 1 to 8, having a tilt of CTE at 20°C in the range of .

10. The titania and silica glass body according to any one of claims 1 to 9, wherein the height of the first glass section is approximately 60% or more of the height of the glass body.

11. The titania and silica glass body according to any one of claims 1 to 10, wherein the height of the second glass section is approximately 10 mm to approximately 75 mm.

12. The titania and silica glass body according to any one of claims 1 to 11, wherein the average spacing between striations in the second glass section is less than the average spacing between striations in the first glass section.

13. The titania and silica glass body according to any one of claims 1 to 12, wherein the second glass section is striation-free.

14. The titania and silica glass body according to claim 13, wherein the first glass section includes striations.

15. The titania and silica glass body according to any one of claims 1 to 14, wherein the glass body comprises the first glass section and the second glass section.

16. The titania and silica glass body according to any one of claims 1 to 15, wherein the glass body is a photomask or a mirror.

17. A method for producing a glass body, wherein the method is Discharge titania-silica soot particle droplets from the furnace burner in a collection cup, wherein the titania-silica soot particle droplets are discharged in a laydown pattern within the collection cup to form a first glass section. Modify the laydown pattern of the titania-silica soot particle droplets to form a second glass section, This includes solidifying the titania-silica soot particle droplets in the collection cup, The first glass section and the second glass section each comprise a single monolithic glass body. The method wherein the average striation height of the second glass section is less than the average striation height of the first glass section.

18. The method according to claim 17, wherein modifying the laydown pattern of the titania-silica soot particle droplets involves moving the collection cup relative to the burner such that the laydown pattern changes from a first helical pattern to a second helical pattern.

19. The method according to claim 17 or 18, wherein modifying the laydown pattern of the titania-silica soot particle droplets makes the titania deposit in the first glass section thicker than the titania deposit in the second glass section.

20. The method according to any one of claims 17 to 19, further comprising forming the glass body consisting of the first glass section and the second glass section without bonding the first glass section to the second glass section.

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