Photomask blank and photomask making method

Abstract

A photomask blank comprises a transparent substrate, a light-shielding film deposited on the substrate and comprising a metal or metal compound susceptible to fluorine dry etching, and an etching mask film deposited on the light-shielding film and comprising another metal or metal compound resistant to fluorine dry etching. When the light-shielding film is dry etched to form a pattern, pattern size variation arising from pattern density dependency is reduced, so that a photomask is produced at a high accuracy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing one exemplary photomask blank in a first embodiment of the invention, FIG. 1A corresponding to a light-shielding film disposed directly on a transparent substrate and FIG. 1B corresponding to a light-shielding film disposed on a transparent substrate via a phase shift film.

FIG. 2 is a cross-sectional view showing one exemplary photomask blank in a second embodiment of the invention, FIG. 2A corresponding to a light-shielding film disposed directly on a transparent substrate and FIG. 2B corresponding to a light-shielding film disposed on a transparent substrate via a phase shift film.

FIG. 3 schematically illustrates steps of a method for preparing a photomask according to the invention, the method using the photomask blank of the first embodiment and producing a binary mask with the etching mask film being removed.

FIG. 4 schematically illustrates steps of a method for preparing a photomask according to the invention, the method using the photomask blank of the second embodiment and producing a binary mask with the etching mask film being left.

FIG. 5 schematically illustrates steps of a method for preparing a photomask according to the invention, the method using the photomask blank of the first embodiment and producing a halftone phase shift mask with the etching mask film being removed.

FIG. 6 schematically illustrates steps of a method for preparing a photomask according to the invention, the method using the photomask blank of the second embodiment and producing a halftone phase shift mask with the etching mask film being left.

FIG. 7 schematically illustrates steps of a method for preparing a photomask according to the invention, the method using the photomask blank of the first embodiment and producing a Levenson mask with the etching mask film being removed.

FIG. 8 schematically illustrates steps of a method for preparing a photomask according to the invention, the method using the photomask blank of the second embodiment and producing a Levenson mask with the etching mask film being left.

FIG. 9 schematically illustrates steps of a method for preparing a photomask according to the invention, the method using the photomask blank of the first embodiment and producing a chromeless mask with the etching mask film being removed.

FIG. 10 schematically illustrates steps of a method for preparing a photomask according to the invention, the method using the photomask blank of the second embodiment and producing a chromeless mask with the etching mask film being left.

FIG. 11 is a graph showing a rate of chlorine gas dry etching versus a chromium content of a chromium-based material film as measured in Experiment 2.

Claims

1. A photomask blank from which is produced a photomask comprising a transparent substrate and a mask pattern formed thereon including transparent regions and effectively opaque regions to exposure light, said photomask blank comprising a transparent substrate,a light-shielding film disposed on the substrate, optionally with another film intervening therebetween, said light-shielding film comprising a metal or metal compound susceptible to fluorine dry etching, andan etching mask film formed on said light-shielding film, said mask film comprising another metal or metal compound resistant to fluorine dry etching.

2. A photomask blank from which is produced a photomask comprising a transparent substrate and a mask pattern formed thereon including transparent regions and effectively opaque regions to exposure light according to claim 1, said photomask blank comprising a transparent substrate,a light-shielding film disposed on the substrate, optionally with another film intervening therebetween, said light-shielding film comprising a metal or metal compound susceptible to fluorine dry etching,an antireflective film formed on said light-shielding film, andan etching mask film formed on said antireflective film, said mask film comprising another metal or metal compound resistant to fluorine dry etching,said antireflective film and said etching mask film being composed of different elements or composed of the same elements in a different compositional ratio.

3. The photomask blank of claim 2, wherein said antireflective film comprises the same metal as in said light-shielding film.

4. A photomask blank from which is produced a photomask comprising a transparent substrate and a mask pattern formed thereon including transparent regions and effectively opaque regions to exposure light according to claim 1, said photomask blank comprising a transparent substrate,a light-shielding film disposed on the substrate, optionally with another film intervening therebetween, said light-shielding film comprising a metal or metal compound susceptible to fluorine dry etching,an etching mask film formed on said light-shielding film, said mask film comprising another metal or metal compound resistant to fluorine dry etching, andan antireflective film formed on said mask film,said antireflective film and said etching mask film being composed of different elements or composed of the same elements in a different compositional ratio.

5. The photomask blank of claim 4, wherein said antireflective film comprises the same metal as in said light-shielding film.

6. The photomask blank of claim 2, wherein said light-shielding film, antireflective film, and etching mask film are contiguously laminated.

7. The photomask blank of claim 1, wherein said light-shielding film has a selectivity ratio in fluorine dry etching of at least 2 relative to said etching mask film.

8. The photomask blank of claim 1, wherein said transparent substrate has a selectivity ratio in fluorine dry etching of at least 10 relative to said etching mask film.

9. The photomask blank of claim 1, wherein said etching mask film is composed of chromium alone or a chromium compound comprising chromium and at least one element selected from oxygen, nitrogen and carbon.

10. The photomask blank of claim 9, wherein said chromium compound contains at least 50 atom % of chromium.

11. The photomask blank of claim 1, wherein said etching mask film is composed of tantalum alone or a tantalum compound comprising tantalum and free of silicon.

12. The photomask blank of claim 1, wherein said light-shielding film is composed of silicon alone or a silicon compound comprising silicon and at least one element selected from oxygen, nitrogen and carbon.

13. The photomask blank of claim 1, wherein said light-shielding film is composed of an alloy of a transition metal with silicon or a transition metal silicon compound comprising a transition metal, silicon, and at least one element selected from oxygen, nitrogen and carbon.

14. A photomask blank from which is produced a photomask comprising a transparent substrate and a mask pattern formed thereon including transparent regions and effectively opaque regions to exposure light according to claim 2, said photomask blank comprising a transparent substrate,a light-shielding film formed on the substrate, optionally with another film intervening therebetween, said light-shielding film comprising a transition metal and silicon susceptible to fluorine dry etching,an antireflective film disposed contiguous to said light-shielding film, said antireflective film comprising a transition metal, silicon, and nitrogen, andan etching mask film disposed contiguous to said antireflective film, said etching mask film comprising chromium and free of silicon, or comprising tantalum and free of silicon.

15. A photomask blank from which is produced a photomask comprising a transparent substrate and a mask pattern formed thereon including transparent regions and effectively opaque regions to exposure light according to claim 4, said photomask blank comprising a transparent substrate,a light-shielding film disposed on the substrate, optionally with another film intervening therebetween, said light-shielding film comprising a transition metal and silicon susceptible to fluorine dry etching,an etching mask film disposed contiguous to said light-shielding film, said etching mask film comprising chromium with a chromium content of at least 50 atom %, andan antireflective film disposed contiguous to said etching mask film, said antireflective film comprising chromium and oxygen with a chromium content of less than 50 atom %.

16. The photomask blank of claim 13, wherein said transition metal is at least one element selected from the group consisting of titanium, vanadium, cobalt, nickel, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten.

17. The photomask blank of claim 13, wherein said transition metal is molybdenum.

18. The photomask blank of claim 13, wherein said light-shielding film further comprises nitrogen with a nitrogen content of 5 atom % to 40 atom %.

19. The photomask blank of claim 1, wherein said etching mask film has a thickness of 2 to 30 nm.

20. The photomask blank of claim 1, wherein a phase shift film intervenes as the other film between the laminated films.

21. The photomask blank of claim 20, wherein said phase shift film is a halftone phase shift film.

22. A method for preparing a photomask, comprising patterning the photomask blank of claim 1.

23. The method of claim 22, comprising fluorine dry etching said light-shielding film through said etching mask film as an etching mask.

24. The method of claim 22, comprising fluorine dry etching said transparent substrate through said etching mask film as an etching mask.

25. The method of claim 22, wherein said photomask is a Levenson mask.