Mask blank, phase-shift mask, and method for manufacturing the same
Provided is a mask blank in which uniformity of the composition and optical characteristics of a phase-shift film in the in-plane direction and direction of film thickness is high, uniformity of the composition and optical characteristics of the phase-shift film between a plurality of substrates is also high, and defectivity is low even if a silicon-based material is applied to the material that forms the phase-shift film. A mask blank is provided in which a phase-shift film is provided on a transparent substrate, the phase-shift film having a function to transmit ArF exposure light therethrough at a predetermined transmittance and generate a predetermined amount of phase shift in the ArF exposure light that is transmitted therethrough, wherein the phase-shift film comprises a structure in which a low transmission layer and a high transmission layer are laminated, the low transmission layer and the high transmission layer are formed from a material consisting of silicon and nitrogen or a material consisting of silicon, nitrogen and one or more elements selected from semi-metallic elements, non-metallic elements and noble gases, and the low transmission layer has a relatively low nitrogen content in comparison with the high transmission layer.
1. A mask blank in which a phase-shift film is provided on a transparent substrate, the phase-shift film having a function to transmit ArF exposure light therethrough at a predetermined transmittance and a function to generate a predetermined amount of phase shift in the ArF exposure light that is transmitted therethrough; wherein,
the phase-shift film comprises a structure in which a low transmission layer and a high transmission layer are laminated,
the low transmission layer and the high transmission layer are formed from a material consisting of silicon and nitrogen or a material consisting of silicon, nitrogen and one or more elements selected from semi-metallic elements, non-metallic elements and noble gas, and
the low transmission layer has a relatively low nitrogen content in comparison with the high transmission layer.
2. The mask blank according to claim 1 , wherein the low transmission layer and the high transmission layer are composed of the same constituent elements.
3. The mask blank according to claim 1 , wherein the phase-shift film has two or more sets of a laminated structure composed of one layer of the low transmission layer and one layer of the high transmission layer.
4. The mask blank according to claim 1 , wherein the low transmission layer and the high transmission layer are formed from a material consisting of silicon and nitrogen.
5. The mask blank according to claim 1 , wherein the low transmission layer is formed from a material having a refractive index n with respect to ArF exposure light of less than 2.5 and an extinction coefficient k with respect to ArF exposure light of not less than 1.0, and
the high transmission layer is formed from a material having a refractive index n with respect to ArF exposure light of not less than 2.5 and an extinction coefficient k with respect to ArF exposure light of less than 1.0.
6. The mask blank according to claim 1 , wherein the thickness of a single layer of each of the low transmission layer and the high transmission layer is not more than 20 nm.
7. The mask blank according to claim 1 , wherein the phase-shift film is provided with an uppermost layer formed at a position farthest away from the transparent substrate, and the uppermost layer is formed from a material consisting of silicon, nitrogen and oxygen, or a material consisting of silicon, nitrogen, oxygen and one or more elements selected from semi-metallic elements, non-metallic elements and noble gases.
8. The mask blank according to claim 7 , wherein the uppermost layer is formed from a material consisting of silicon, nitrogen and oxygen.
9. A phase-shift mask in which a transfer pattern is formed on the phase-shift film of the mask blank according to claim 1 .
10. A method for manufacturing a mask blank provided with a phase-shift film on a transparent substrate, the phase-shift film having a function to transmit ArF exposure light therethrough at a predetermined transmittance and a function to generate a predetermined amount of phase shift in the ArF exposure light that is transmitted therethrough;
wherein the phase-shift film comprises a structure in which a low transmission layer and a high transmission layer are laminated,
wherein the method comprises:
a low transmission layer formation step of forming the low transmission layer on or above the transparent substrate by reactive sputtering in a sputtering gas comprising a nitrogen-based gas and a noble gas using a silicon target or a target composed of a material consisting of silicon and one or more elements selected from semi-metallic elements and non-metallic elements, and
a high transmission layer formation step of forming the high transmission layer on or above the transparent substrate by reactive sputtering in a sputtering gas comprising a nitrogen-based gas and a noble gas, and the sputtering gas having a higher mixing ratio of nitrogen-based gas than the mixing ratio of nitrogen-based gas in the sputtering gas for the low transmission layer formation step, using a silicon target or a target composed of a material consisting of silicon and one or more elements selected from semi-metallic elements and non-metallic elements.
11. The method for manufacturing a mask blank according to claim 10 , wherein a mixing ratio of nitrogen-based gas selected for the sputtering gas used in the low transmission layer formation step is lower than the range of nitrogen-based gas mixing ratios at which deposition is in a transition mode in which deposition has a tendency to become unstable, and
a mixing ratio of nitrogen-based gas selected for the sputtering gas used in the high transmission layer formation step is higher than the range of nitrogen-based gas mixing ratios at which deposition is in the transition mode.
12. The method for manufacturing a mask blank according to claim 10 , wherein the low transmission layer formation step forms the low transmission layer by reactive sputtering in a sputtering gas consisting of nitrogen gas and a noble gas using a silicon target, and the high transmission layer formation step forms the high transmission layer by reactive sputtering in a sputtering gas consisting of nitrogen and a noble gas using a silicon target.
13. The method for manufacturing a mask blank according to claim 10 , wherein the low transmission layer is formed from a material having a refractive index n with respect to ArF exposure light of less than 2.5 and an extinction coefficient k with respect to ArF exposure light of not less than 1.0, and
the high transmission layer is formed from a material having a refractive index n with respect to ArF exposure light of not less than 2.5 and an extinction coefficient k with respect to ArF exposure light of less than 1.0.
14. The method for manufacturing a mask blank according to claim 10 , further comprising an uppermost layer formation step of forming an uppermost layer, at a position of the phase-shift film farthest away from the transparent substrate, by reactive sputtering in a sputtering gas comprising a noble gas using a silicon target or a target composed of a material consisting of silicon and one or more elements selected from semi-metallic elements and non-metallic elements.
15. The method for manufacturing a mask blank according to claim 12 , further comprises an uppermost layer formation step of forming an uppermost layer, at a position of the phase-shift film farthest away from the transparent substrate, by reactive sputtering in a sputtering gas composed of nitrogen gas and a noble gas using a silicon target, and carrying out treatment in which at least the surface layer of the uppermost layer is oxidized.
16. A method for manufacturing a phase-shift mask, comprising: forming a transfer pattern in the phase-shift film of a mask blank manufactured according to the method for manufacturing a mask blank according to claim 10 .