1. A silica glass containing TiO2, which has a TiO2 concentration of from 3 to 10 mass %, a OH group concentration of at most 600 mass ppm and a Ti3+ concentration of at most 70 mass ppm, characterized by having a fictive temperature of at most 1,000\xb0 C., a coefficient of thermal expansion CTE0-100 from 0 to 100\xb0 C. of 0\xb1150 ppb\xb0 C., and an internal transmittance T400-700 per 1 mm thickness in a wavelength range of from 400 to 700 nm of at least 80%.
2. The silica glass containing TiO2 according to claim 1, which has a F concentration of at least 100 mass ppm.
3. The silica glass containing TiO2 according to claim 1, which has an internal transmittance T300-3000 per 1 mm thickness in a wavelength range of from 300 to 3,000 nm of at least 70%.
4. The silica glass containing TiO2 according to claim 1, which has a temperature range of at least 4.0\xb0 C. wherein the coefficient of thermal expansion becomes is 0\xb15 ppb\xb0 C.
5. The silica glass containing TiO2 according to claim 1, wherein the fictive temperature is at most 900\xb0 C.
6. The silica glass containing TiO2 according to claim 1, wherein the TiO2 concentration is from 5 to 9 mass %.
7. The silica glass containing TiO2 according to claim 1, wherein T400-700 per 1 mm thickness in a wavelength range of from 400-700 nm is at least 90%.
8. The silica glass containing TiO2 according to claim 1, wherein CTE0-100 from 0 to 100\xb0 C. is 0\xb1100 ppb0\xb0 C.
9. The silica glass containing TiO2 according to claim 1, wherein the OH group concentration is at most 100 mass ppm.
10. The silica glass containing TiO2 according to claim 1, wherein the Ti3+ concentration is at most 20 mass ppm.
11. The silica glass containing TiO2 according to claim 1, which has an internal transmittance T300-700 per 1 mm thickness in wavelength range of from 300 to 700 nm of at least 80%.
12. The silica glass containing TiO2 according to claim 3, wherein T300-3000 per 1 mm thickness in wavelength range of from 300 to 3000 nm is at least 80%.
13. The silica glass containing TiO2 according to claim 2, wherein the F concentration is at least 5000 mass ppm.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of forming semiconductor structures, the method comprising:
receiving a substrate having a pattern thereon defined by spacers formed on sidewalls of a plurality mandrels; and
transferring the pattern defined by the spacers into the substrate using a plasma etch process that etches the mandrels and the substrate, the transferring forming first recessed features in the substrate below the mandrels and second recessed features in the substrate between the mandrels,
wherein the plasma etch process utilizes an etching gas containing O2 gas, and the relative amount of O2 gas in the etching gas is selected to control the depth of the first recessed features relative to the depth of second recessed features.
2. The method of claim 1, further comprising:
selecting an amount of O2 gas in the etching gas such that a depth of the first recessed features is greater than the depth of the second recessed features.
3. The method of claim 1, further comprising:
selecting an amount of O2 gas in the etching gas such that a depth of the first recessed features is smaller than the depth of the second recessed features.
4. The method of claim 1, further comprising:
selecting an amount of O2 gas in the etching gas such that a depth of the first recessed features is substantially the same as the depth of the second recessed features.
5. The method of claim 1, wherein the etching gas further contains a halogen-containing gas.
6. The method of claim 1, wherein the etching gas further contains a silicon-halogen-containing gas.
7. The method of claim 6, wherein the silicon-halogen-containing gas is selected from the group consisting of SiF4 and SiCl4.
8. The method of claim 1, wherein the spacers contain SiO2.
9. The method of claim 1, wherein the mandrels contain a photoresist.
10. The method of claim 1, wherein the substrate contains a carbon-containing material.
11. A method of forming semiconductor structures, the method comprising:
receiving a substrate having a mask layer thereon and a pattern on the mask layer, the pattern defined by spacers formed on sidewalls of a plurality mandrels; and
transferring the pattern defined by the spacers into the substrate using a plasma etch process that etches the mandrels, the mask layer, and the substrate, the transferring forming first recessed features in the mask layer and in the substrate below the mandrels and second recessed features in the mask layer and the substrate between the mandrels,
wherein the plasma etch process utilizes an etching gas containing O2 gas, and the relative amount of O2 gas in the etching gas is selected to control the depth of the first recessed features relative to the depth of second recessed features.
12. The method of claim 11, further comprising:
selecting an amount of O2 gas in the etching gas such that a depth of the first recessed features is greater than the depth of the second recessed features.
13. The method of claim 11, further comprising:
selecting an amount of O2 gas in the etching gas such that a depth of the first recessed features is smaller than the depth of the second recessed features.
14. The method of claim 11, further comprising:
selecting an amount of O2 gas in the etching gas such that a depth of the first recessed features is substantially the same as the depth of the second recessed features.
15. The method of claim 11, wherein the etching gas comprises O2 and a halogen-containing gas.
16. The method of claim 11, wherein the etching gas comprises O2 and a silicon-halogen-containing gas selected from the group consisting of SiF4 and SiCl4.
17. The method of claim 11, wherein the spacers contain SiO2.
18. The method of claim 11, wherein the mandrels contain a photoresist.
19. The method of claim 11, wherein the substrate contains a carbon-containing material.
20. The method of claim 11, wherein the mask layer contains a silicon-containing antireflective coating (SiARC).