Manufacturing method for SiO
A method for manufacturing an SiO 2 —TiO 2 based glass upon a target by a direct method, includes a first process of preheating the target and a second process of growing an SiO 2 —TiO 2 based glass ingot to a predetermined length upon the target which has been preheated, wherein the target is heated in the first process such that, in the second process, the temperature of growing surface of the glass ingot is maintained at or above a predetermined lower limit temperature.
1. A method for manufacturing an SiO 2 —TiO 2 based glass upon a target by a direct method, comprising:
a first process of preheating the target; and
a second process of growing an SiO 2 —TiO 2 based glass ingot to a predetermined length upon the target which has been preheated, wherein
the target is heated in the first process such that, in the second process, a temperature of a growing surface of the glass ingot is maintained at or above a predetermined lower limit temperature,
the target includes a thermal storage portion that accumulates heat during the first process, and a heat insulating portion that suppresses conduction of heat from the thermal storage portion in the direction opposite to that of the glass ingot,
the thermal storage portion and the heat insulating portion comprise a plate-shaped first member and a plate-shaped second member, respectively,
the first member has a larger thermal capacity than the second member,
the second member has a lower thermal conductivity than the first member, and
the thermal storage portion has convex portions upon a surface of the first member that is opposite to the glass ingot.
2. The method for manufacturing an SiO 2 —TiO 2 based glass according to claim 1 , wherein:
a thermal dose for heating the target is set so that the temperature of growing surface of the glass ingot is maintained at 1600° C. or higher.
3. The method for manufacturing an SiO 2 —TiO 2 based glass according to claim 1 , wherein:
a condition for the second process to start is that, in the first process, the temperature of the target should have reached a predetermined temperature.
4. The method for manufacturing an SiO 2 —TiO 2 based glass according to claim 1 , wherein:
the target comprises a circular plate-shaped target member and an SiO 2 glass layer formed upon the target member.
5. The method for manufacturing an SiO 2 —TiO 2 based glass according to claim 1 , wherein:
the first member and the second member are in mutual thermal contact via the convex portions.
6. A method for manufacturing a plate-shaped member made of SiO 2 —TiO 2 based glass, the method comprising:
manufacturing SiO 2 —TiO 2 based glass according to the manufacturing method of claim 1 ; and
manufacturing a plate-shaped member by applying heat to and pressure molding the SiO 2 —TiO 2 based glass.
7. A method for manufacturing a photo-mask substrate made of SiO 2 —TiO 2 based glass, comprising:
manufacturing the SiO 2 —TiO 2 based glass by the manufacturing method according to claim 1 ;
applying heat and pressure to the SiO 2 —TiO 2 based glass, so that the SiO 2 —TiO 2 based glass is formed into a plate-shaped member; and
polishing the plate-shaped member formed from the SiO 2 —TiO 2 based glass.