Light pattern exposure method, photomask, and photomask blank
A light pattern exposure method is by irradiating ArF excimer laser light to a resist film through a photomask. The photomask includes a transparent substrate and a pattern of optical film of a material comprising a transition metal, silicon, nitrogen and oxygen, with contents thereof falling in a specific range. The photomask may be irradiated with ArF excimer laser light in a cumulative dose of at least 10 kJ/cm 2 .
1. A light pattern exposure method comprising irradiating a pattern of light to a resist film through a photomask using ArF excimer laser light as the light source, wherein
the photomask used is such that it has been irradiated with ArF excimer laser light in a cumulative dose of at least 10 kJ/cm 2 ,
said photomask comprising a transparent substrate and a pattern of optical film of a material comprising a transition metal, silicon, and nitrogen and/or oxygen, the transition metal having potentially a valence of 6,
the contents of transition metal, silicon, nitrogen and oxygen in the optical film meeting both the formulae (1) and (2):
6×C M /100−4×C Si /100≦−0.89 (1)
6C M ×3C N /(6C M ×6C M +6C M ×4C Si +6C M ×3C N +6C M ×2C O +4C Si ×4C Si +4C Si ×3C N +4C Si ×2C O )≧0.094 (2)
wherein C M is a transition metal content in atom %, C Si is a silicon content in atom %, C N is a nitrogen content in atom % and C O is an oxygen content in atom %, except for an outermost surface region extending from the film surface remote from the substrate to a depth of 10 nm.
2. The method of claim 1 wherein the photomask has been treated for defect correction by directing a high-energy radiation beam in a fluorine base gas atmosphere.
3. The method of claim 1 wherein the transition metal is molybdenum.
4. A photomask for use in a light pattern exposure method comprising irradiating a pattern of light to a resist film through the mask using ArF excimer laser light as the light source, said photomask being such that it may be irradiated with ArF excimer laser light in a cumulative dose of at least 10 kJ/cm 2 ,
said photomask comprising a transparent substrate and a pattern of optical film, the pattern being obtained by forming an optical film of a material comprising a transition metal, silicon, and nitrogen and/or oxygen on the substrate and patterning the film, the transition metal having potentially a valence of 6,
the contents of transition metal, silicon, nitrogen and oxygen in the optical film meeting both the formulae (1) and (2):
6×C M /100−4×C Si /100≦−0.89 (1)
6C M ×3C N /(6C M ×6C M +6C M ×4C Si +6C M ×3C N +6C M ×2C O +4C Si ×4C Si +4C Si ×3C N +4C Si ×2C O )≧0.094 (2)
wherein C M is a transition metal content in atom %, C Si is a silicon content in atom %, C N is a nitrogen content in atom % and C O is an oxygen content in atom %, except for an outermost surface region extending from the film surface remote from the substrate to a depth of 10 nm.
5. The photomask of claim 4 wherein the transition metal is molybdenum.
6. The photomask of claim 4 wherein the transparent substrate is a silicon oxide substrate, and an etching selectivity ratio of at least 4 is established between the optical film and the silicon oxide substrate.
7. A photomask blank from which a photomask is prepared, wherein the photomask is used in irradiating a pattern of light to a resist film using ArF excimer laser light as the light source, and the photomask may be irradiated with ArF excimer laser light in a cumulative dose of at least 10 kJ/cm 2 ,
said photomask blank comprising a transparent substrate and an optical film of a material comprising a transition metal, silicon, and nitrogen and/or oxygen, the transition metal having potentially a valence of 6,
the contents of transition metal, silicon, nitrogen and oxygen in the optical film meeting both the formulae (1) and (2):
6×C M /100−4×C Si /100≦−0.89 (1)
6C M ×3C N /(6C M ×6C M +6C M ×4C Si +6C M ×3C N +6C M ×2C O +4C Si ×4C Si +4C Si ×3C N +4C Si ×2C O )≧0.094 (2)
wherein C M is a transition metal content in atom %, C Si is a silicon content in atom %, C N is a nitrogen content in atom % and C O is an oxygen content in atom %, except for an outermost surface region extending from the film surface remote from the substrate to a depth of 10 nm.
8. The blank of claim 7 wherein the transition metal is molybdenum.
9. The blank of claim 7 wherein the transparent substrate is a silicon oxide substrate, and an etching selectivity ratio of at least 4 is established between the optical film and the silicon oxide substrate.