Exposure apparatus including silica glass for photolithography
AssigneeNikon Corporation
InventorsHiroki Jinbo, Norio Komine, Hiroyuki Hiraiwa
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Abstract
A silica glass has a structure determination temperature of 1200 K or lower and an OH group concentration of at least 1,000 ppm. The silica glass is used for photolithography together with light in a wavelength region of 400 nm or shorter.
Claims21
A silica glass for photolithography used together with light in a wavelength region of 400 nm or shorter, said silica glass having a structure determination temperature of 1,200 K or lower and an OH group concentration of at least 1,000 ppm.
A method for producing a silica glass having a structure determination temperature of 1,200 K or lower and an OH group concentration of at least 1,000 ppm, said method comprising the steps of:
- heating a silica glass ingot having an OH group concentration of 1,000 ppm or more to a temperature of 1,200 to 1,350 K;
- maintaining said ingot at said temperature for a predetermined period of time;
- and then
- cooling said ingot to a temperature of 1,000 K or lower at a temperature-lowering rate of 50 K/hr or less to anneal said ingot.
Dependencies are inferred from the claim text.