Phase shift blankmask and photomask for EUV lithography
Disclosed is a blankmask for EUV lithography, including a reflective film, a capping film and a phase shift film which are sequentially formed on a substrate. The phase shift film includes a first layer containing niobium (Nb) and chrome (Cr), and a second layer containing tantalum (Ta) and silicon (Si). In the first layer, the content of niobium (Nb) ranges from 20 to 50 at %, and the content of chrome (Cr) content ranges from 10 to 40 at %. The blankmask can implement an excellent resolution and NILS, and implement a low DtC.
1 . A blankmask for extreme ultraviolet (EUV) lithography, comprising a substrate, a reflective film formed on the substrate, a capping film formed on the reflective film, and a phase shift film formed on the capping film,
the phase shift film comprising:
a first layer formed on the capping film, containing chrome (Cr) and niobium (Nb) and further containing one or more of oxygen (O), nitrogen (N), and carbon (C), having a thickness of 30 to 60 nm, and having a refractive index (n) of 0.925 to 0.935 and an extinction coefficient (k) of 0.015 to 0.025 with respect to exposure light having a wavelength of 13.5 nm, and
a second layer formed on the first layer and containing tantalum (Ta) and further containing one or more of oxygen (O), nitrogen (N), and carbon (C), having a thickness of 2 to 10 nm, and having a refractive index (n) of 0.940 to 0.960 and an extinction coefficient (k) of 0.025 to 0.035 with respect to exposure light having a wavelength of 13.5 nm.
2 . The blankmask of claim 1 , wherein content of niobium in the first layer ranges from 20 to 50 at %.
3 . The blankmask of claim 1 , wherein content of chrome (Cr) in the first layer ranges from 10 to 40 at %.
4 . The blankmask of claim 1 , wherein content of nitrogen (N) in the first layer ranges from 10 to 60 at %.
5 . The blankmask of claim 1 , wherein the first layer has a thickness of 80% or more of a total thickness of the phase shift film.
6 . The blankmask of claim 1 , wherein content of tantalum (Ta) in the second layer is higher than or equal to 50 at %.
7 . The blankmask of claim 6 , wherein the second layer further contains boron (B).
8 . The blankmask of claim 7 , wherein content of boron (B) in the second layer ranges from 5 to 20 at %.
9 . The blankmask of claim 6 , wherein the second layer has a surface reflectivity of 40% or lower to inspection light having a wavelength of 193 nm.
10 . The blankmask of claim 1 , wherein the phase shift film has a relative reflectivity of 6 to 15% to the reflective film with respect to exposure light having a wavelength of 13.5 nm.
11 . A photomask prepared using the blankmask for extreme ultraviolet (EUV) lithography of claim 1 .