Reflective mask blank and reflective mask
A reflective mask blank includes a backside conductive film on a back surface of a substrate. The backside conductive film has a laminated structure including a stress compensation layer and a conductive layer in this order from the substrate side. The conductive layer includes a metal nitride. The stress compensation layer has a compressive stress and the stress compensation layer includes at least one compound selected from the group consisting of oxides, oxynitrides, and nitrides, each having an absorption coefficient (k) over the wavelength range of 400 nm to 800 nm being 0.1 or less. The conductive layer has a thickness of 5 nm or more and 30 nm or less. The backside conductive film has a total thickness of 50 nm or more.
1. A reflective mask blank, comprising: a backside conductive film on a back surface of a substrate, wherein the backside conductive film has a laminated structure comprising:
a stress compensation layer; and
a conductive layer;
in this order from the substrate side,
wherein
the conductive layer comprises a metal nitride,
the stress compensation layer has a compressive stress,
the stress compensation layer comprises at least one compound selected from the group consisting of oxides of Sn, Zr, Zn, Ti, Nb and Al, oxynitrides of Sn, Zr, Zn, Ti, Nb and Al, and nitrides of Sn, Zr, Zn, Ti Nb and Al, each having an absorption coefficient (k) over the wavelength range of 400 nm to 800 nm being 0.1 or less,
the metal nitride in the conductive layer comprises at least one element selected from the group consisting of Cr, Ti, Zr, and Nb,
the conductive layer has a thickness of 5 nm or more and 30 nm or less, and has a different composition than the stress compensation layer, and
the backside conductive film has a total thickness of from 100 nm to 600 nm.
2. The reflective mask blank according to claim 1 , wherein the backside conductive film has a compressive stress with a total stress of 50 Pa·m to 400 Pa·m.
3. The reflective mask blank according to claim 1 , wherein the stress compensation layer has a compressive stress with a film internal stress per unit film thickness of 300 MPa to 2,000 MPa.
4. The reflective mask blank according to claim 1 , wherein the stress compensation layer has a refractive index (n) over the wavelength range of 400 nm to 800 nm of 1.7 or more.
5. The reflective mask blank according to claim 1 , wherein the conductive layer has a refractive index (n) at a wavelength of 532 nm of 3.5 or less and an absorption coefficient at a wavelength of 532 nm of 4.0 or less.
6. The reflective mask blank according to claim 1 , wherein the backside conductive film has a sheet resistance (Rs) of 250 Ω/square or less.
7. The reflective mask blank according to claim 1 , wherein the backside conductive film has transmittance over the wavelength range of 400 nm to 800 nm of 10% or more.
8. The reflective mask blank according to claim 1 , which comprises a reflective layer which reflects EUV light and an absorber layer which absorbs EUV light on/above a front surface of the substrate in this order from the substrate side.
9. A reflective mask obtained by forming a pattern in the absorber layer of the reflective mask blank according to claim 8 .