Binary photomask blank and binary photomask making method

摘要

A binary photomask blank has on a transparent substrate a light-shielding film including substrate-side and surface-side compositionally graded layers, having a thickness of 35-60 nm, and composed of a silicon base material containing a transition metal and N and/or O. The substrate-side compositionally graded layer has a thickness of 10-58.5 nm , and a N+O content of 25-40 at % at its lower surface and 10-23 at % at its upper surface. The surface-side compositionally graded layer has a thickness of 1.5-8 nm, and a N+O content of 10-45 at % at its lower surface and 45-55 at % at its upper surface.

主权项

1. A binary photomask blank comprising a transparent substrate and a light-shielding film thereon having an optical density of 2.5 to 3.5, wherein
said light-shielding film i) consists of a substrate-side compositionally graded layer disposed contiguous to the transparent substrate, a surface-side compositionally graded layer disposed remote from the transparent substrate, or a substrate-side compositionally graded layer disposed contiguous to the transparent substrate, a surface-side compositionally graded layer disposed remote from the transparent substrate, and an intermediate layer in between the substrate-side compositionally graded layer and the surface-side compositionally graded layer, ii) has a thickness of 35 to 60 nm, and iii) is composed of a silicon base material containing a transition metal and nitrogen and/or oxygen, said substrate-side compositionally graded layer is a layer haying a thickness of 10 to 58.5 nm in which the total content of nitrogen and oxygen increases in a thickness direction toward the transparent substrate, said substrate-side compositionally graded layer comprises iv) a layer whose composition varies continuously in the thickness direction, v) a combination of at least three layers each having a consistent composition, vi) a combination of a layer having a consistent composition with a layer whose composition varies continuously in the thickness direction, or vii) a combination of layers whose composition varies continuously in the thickness direction, the silicon base material of said substrate-side compositionally graded layer contains the transition metal and silicon in an atomic ratio from 1:2 to 1:9, the total content of nitrogen and oxygen in said substrate-side compositionally graded layer is 25 to 40 atom % at its surface contiguous to the transparent substrate and 10 to 23 atom % at its surface remote from the transparent substrate, said surface-side compositionally graded layer is a layer having a thickness of 1.5 to 6 nm in which the total content of nitrogen and oxygen decreases in the thickness direction toward the transparent substrate, said surface-side compositionally graded layer comprises a layer whose composition varies continuously in the thickness direction, a combination of at least two layers each having a consistent composition, a combination of a layer having a consistent composition with a layer whose composition varies continuously in the thickness direction, or a combination of layers whose composition varies continuously in the thickness direction, the silicon base material of said surface-side compositionally graded layer contains the transition metal and silicon in an atomic ratio from 1:2 to 1:9, the total content of nitrogen and oxygen in said surface-side compositionally graded layer is 10 to 45 atom % at its surface nearer to the transparent substrate and 45 to 55 atom % at its surface remote from the transparent substrate, and wherein said light-shielding film has a reflectance of up to 40% on both the front and back surfaces of the light-shielding film.