Back to results
US 7,923,178 B2Granted
Glass substrate for mask blank and method of polishing for producing the same
AssigneeAsahi Glass Company, Limited
InventorsMasabumi Ito, Hiroshi Kojima
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeAsahi Glass Company, Limited
InventorsMasabumi Ito, Hiroshi Kojima
Estimating the term…
The present invention aims at providing a glass substrate required to have a surface polished with extremely high accuracy as in glass substrates for reflective masks for use in EUVL; and a polishing method for producing the glass substrate. The present invention provides a glass substrate for mask blank, which is a glass substrate comprising SiO2 as a main component and having a polished main surface, wherein concave defects and convex defects on the main surface have a depth of 2 nm or smaller and a height of 2 nm or smaller, respectively, and have a half-value width of 60 nm or smaller, so that the concave defects and/or the convex defects do not cause phase defects when the glass substrate is used to produce a mask for exposure and the mask is used. Also disclosed are a polishing method for producing the glass substrate, and a mask blank and a mask for exposure using the glass substrate.
A glass substrate comprising SiO2 as a main component and having a polished main surface, wherein concave defects and convex defects on the main surface have a depth of 2 nm or smaller and a height of 2 nm or smaller, respectively, and have a half-value width of 60 nm or smaller.
A method of polishing for producing a glass substrate, which comprises supplying a polishing slurry comprising colloidal silica having an average primary-particle diameter of 60 nm or smaller and water to a gap between a glass substrate comprising SiO2 as a main component and a nap layer of a polishing pad and polishing a main surface of the glass substrate with the nap layer, wherein the nap layer of the polishing pad has a compressibility of 10% or higher and a compressive modulus of 85% or higher to thereby polish the main surface so that concave defects and convex defects on the polished main surface have a depth of 2 nm or smaller and a height of 2 nm or smaller, respectively, and have a half-value width of 60 nm or smaller.
Dependencies are inferred from the claim text.