The present invention provides a TiO 2 —SiO 2 glass in which when used as an optical member for an exposure tool for EUVL, a thermal expansion coefficient is substantially zero at the time of irradiation with high-EUV energy light, and physical properties of a multilayer can be kept over a long period of time by releasing hydrogen from the glass. The present invention relates to a TiO 2 -containing silica glass having a fictive temperature of 1,100° C. or lower, a hydrogen molecule concentration of 1×10 16 molecules/cm 3 or more, and a temperature, at which a linear thermal expansion coefficient is 0 ppb/° C., falling within the range of from 40 to 110° C.
1. A TiO 2 -containing silica glass having a TiO 2 content of at least 8% by mass, a fictive temperature of 1,100° C. or lower, a hydrogen molecule concentration of at least 1×10 17 molecules/cm 3 , an OH concentration of at least 600 ppm, temperature width in which a linear thermal expansion coefficient is 0±5 ppb/° C. (ΔT) of at least 8° C., and a temperature, at which a linear thermal expansion coefficient is 0 ppb/° C., falling within the range of from 40 to 110° C.
2. The TiO 2 -containing silica glass according to claim 1 , having a TiO 2 content of from 8 to 12% by mass.
3. The TiO 2 -containing silica glass according to claim 1 , having an average linear thermal expansion coefficient at from 20 to 100° C. of 60 ppb/° C. or lower.
4. The TiO 2 -containing silica glass according to claim 1 , wherein (ΔT) is at least 15° C.
5. The TiO 2 -containing silica glass according to claim 1 , which is free from an inclusion.
6. An optical member for EUV lithography using the TiO 2 -containing silica glass according to claim 1 .
7. The TiO 2 -containing silica glass according to claim 1 , wherein the hydrogen molecule concentration is at least 5×10 17 molecules/cm 3 .
8. The TiO 2 -containing silica glass according to claim 1 , wherein the hydrogen molecule concentration is at least 1×10 18 molecules/cm 3 .
9. The TiO 2 -containing silica glass according to claim 1 , wherein the temperature, at which a linear thermal expansion coefficient is 0 ppb/° C., is within the range of from 45 to 100° C.
10. The TiO 2 -containing silica glass according to claim 1 , wherein the temperature, at which a linear thermal expansion coefficient is 0 ppb/° C., is within the range of from 50 to 80° C.
11. The TiO 2 -containing silica glass according to claim 3 , wherein the average linear thermal expansion coefficient at from 20 to 100° C. is at least −120 ppb/° C.
12. The TiO 2 -containing silica glass according to claim 3 , wherein the average linear thermal expansion coefficient at from 20 to 100° C. is at least −100 ppb/° C.
13. The TiO 2 -containing silica glass according to claim 3 , wherein the average linear thermal expansion coefficient at from 20 to 100° C. is at least −60 ppb/° C.
14. The TiO 2 -containing silica glass according to claim 3 , wherein the average linear thermal expansion coefficient at from 20 to 100° C. is at least −50 ppb/° C.
15. The TiO 2 -containing silica glass according to claim 1 , wherein the TiO 2 content is at least 8.5% by mass.
16. The TiO 2 -containing silica glass according to claim 1 , wherein the fictive temperature is 900° C. or lower.
17. The TiO 2 -containing silica glass according to claim 1 , wherein the fictive temperature is 850° C. or lower.
18. The TiO 2 -containing silica glass according to claim 1 , wherein the fictive temperature is 800° C. or lower.
19. The TiO 2 -containing silica glass according to claim 1 , wherein the variation in the fictive temperature is within 50° C.
20. The TiO 2 -containing silica glass according to claim 1 , wherein the variation in the fictive temperature is within 30° C.