Adjusting expansivity in doped silica glasses
OwnerAdam Ellison, Kenneth Hrdina +1inventors
InventorsAdam Ellison, Kenneth Hrdina, Sabyasachi Sen
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Abstract
The invention is directed to ultra-low expansion glasses to which adjustments have been made to selected variables in order to improve the properties of the glasses, and particularly to lower the expansivity of the glasses. The glasses are titania-doped silica glasses. The variables being adjusted include an adjustment in β-OH level; an adjustment to the cooling rate of the molten glass material through the setting point; and the addition of selected dopants to impact the CTE behavior.
Claims14
A method for making and adjusting the expansivity of a silica-titania ultra-low expansion glass, the method comprising:
- making a silica-titania containing powder or powder preform using a silica precursor and a titanium precursor compound;
- consolidating the powder or powder preform into glass in the presence of an inert gas containing water vapor,
- lowering the temperature of the consolidated glass from a consolidation temperature to an annealing temperature, annealing the glass;
- and
- cooling the glass to ambient temperature to form an ultra-low expansion silica-titania glass having a β-OH level in ppm by weight in the range of greater than 100 ppm to 1500 ppm.
The method according to claim 2, wherein the inert gas is helium.
A method of making an ultra-low expansive glass suitable for use as a reflective optic substrate in extreme ultraviolet lithographic systems, said method comprising:
- making a silica-titania glass by flame hydrolysis by supplying a silica precursor, a titania precursor and, optionally, a dopant precursor to a flame to form a soot;
- depositing the soot in a vessel whose temperature is below the consolidation temperature of the soot;
- consolidating the soot at a consolidation temperature in the presence of an inert gas containing water vapor to form a glass;
- lowering the temperature of the glass to an annealing temperature;
- annealing the glass;
- and
- lowering the temperature of the annealed glass to ambient temperature.
A method of making an ultra-low expansive glass suitable for use as a reflective optic substrate in extreme ultraviolet lithographic systems, said method comprising:
- making a silica-titania glass by flame hydrolysis by supplying a silica precursor, a titania precursor and, optionally, a dopant precursor and water vapor to a flame to form a soot;
- depositing the soot in a vessel whose temperature is at or above the consolidation temperature of the soot;
- consolidating the soot at said consolidation temperature to form a glass;
- lowering the temperature of the glass to an annealing temperature;
- annealing the glass;
- and
- lowering the temperature of the annealed glass to ambient temperature.
Dependencies are inferred from the claim text.