Mask blank, transfer mask, and methods of manufacturing the same
This invention provides a mask blank in which a thin film for transfer pattern formation is provided on a main surface of a transparent substrate. The thin film is made of a material containing a transition metal and silicon and further containing at least one of oxygen and nitrogen. The thin film has as its surface layer an oxide layer with an oxygen content higher than that of a region, other than the surface layer, of the thin film. The thin film is formed so that the thickness of its central portion is greater than that of its outer peripheral portion on the main surface side. The oxide layer is formed so that the thickness of its central portion is greater than that of its outer peripheral portion on the main surface side.
1. A mask blank comprising a thin film for transfer pattern formation on a main surface of a transparent substrate,
wherein the thin film is made of a material containing a transition metal and silicon and further containing at least one of oxygen and nitrogen,
wherein the thin film has as its surface layer an oxide layer with an oxygen content higher than that of a region, other than the surface layer, of the thin film,
wherein the thin film is formed so that a thickness of its central portion is greater than that of its outer peripheral portion on the main surface side, and
wherein the oxide layer is formed so that a thickness of its central portion is greater than that of its outer peripheral portion on the main surface side.
2. The mask blank according to claim 1 , wherein the thin film is a semitransmissive film having a transmittance of 1% or more for exposure light.
3. The mask blank according to claim 1 , wherein the thin film is a halftone phase shift film having a transmittance of 1% or more for exposure light and adapted to produce a phase difference between exposure light transmitted through the thin film and exposure light transmitted in air for a distance equal to the thickness of the thin film.
4. The mask blank according to claim 2 , wherein the thin film is such that an in-plane distribution of the transmittance is in a range of 0.6%.
5. The mask blank according to claim 3 , wherein the thin film is such that an in-plane distribution of the phase difference is in a range of 4 degrees.
6. A transfer mask, wherein the thin film of the mask blank according to claim 1 is formed with a transfer pattern.