Mask blank and method of manufacturing photomask
A mask blank has a structure where a thin film for pattern formation and a hard mask film are stacked in this order on a transparent substrate, featured in that the thin film is formed of a material containing chromium, the hard mask film includes a stacked structure of a lower layer and an upper layer, the lower layer is formed of a material containing silicon and oxygen, the upper layer is formed of a material containing tantalum and oxygen with an oxygen content of 30 atom % or more, and the ratio of a thickness of the upper layer relative to a total thickness of the hard mask film is 0.7 or less.
1. A mask blank having a structure where a thin film for pattern formation and a hard mask film are stacked in this order on a transparent substrate,
wherein the thin film is formed of a material containing chromium,
wherein the hard mask film has a stacked structure of a lower layer and an upper layer,
wherein the lower layer is formed of a material containing silicon and oxygen,
wherein the upper layer is formed of a material containing tantalum and oxygen and containing the oxygen of 30 atom % or more, and
wherein a ratio of a thickness of the upper layer relative to a total thickness of the hard mask film is 0.7 or less.
2. The mask blank according to claim 1 , wherein the upper layer has a thickness of 1 nm or more.
3. The mask blank according to claim 1 , wherein the hard mask film has a thickness of 4 nm or more and 14 nm or less.
4. The mask blank according to claim 1 , wherein the upper layer contains boron.
5. The mask blank according to claim 1 , wherein the lower layer is formed of a material with a total content of silicon and oxygen of 96 atom % or more, or a material with a total content of silicon, nitrogen, and oxygen of 96 atom % or more.
6. The mask blank according to claim 1 , wherein the upper layer is formed of a material with a total content of tantalum and oxygen of 90 atom % or more, or a material with a total content of tantalum, oxygen, and boron of 90 atom % or more.
7. The mask blank according to claim 1 , wherein the thin film is an absorber film.
8. The mask blank according to claim 7 comprising a phase shift film consisting of a material containing silicon between the transparent substrate and the absorber film.
9. A method of manufacturing a photomask using the mask blank according to claim 8 , comprising the steps of:
forming a resist pattern on a hard mask film of the mask blank,
dry-etching the hard mask film with fluorine-based gas with the resist pattern as a mask to form a hard mask pattern,
dry-etching the absorber film with mixed gas of chlorine and oxygen with the hard mask pattern as a mask to form an absorber film pattern, and
dry-etching the phase shift film with fluorine-based gas with the absorber film pattern as a mask to form a phase shift film pattern while removing the hard mask pattern.
10. A method of manufacturing a photomask using the mask blank according to claim 1 , comprising the steps of:
forming a resist pattern on a hard mask film of the mask blank,
dry-etching the hard mask film with fluorine-based gas with the resist pattern as a mask to form a hard mask pattern, and
dry-etching the thin film for pattern formation with mixed gas of chlorine and oxygen with the hard mask pattern as a mask to form a thin film pattern.