Reflective mask blank, reflective mask and method of manufacturing semiconductor device
Provided are a reflective mask blank, having a phase shift film having little dependence of phase difference and reflectance on film thickness, and a reflective mask. The reflective mask blank is characterized in that the phase shift film is composed of a material comprised of an alloy having two or more types of metal so that reflectance of the surface of the phase shift film is more than 3% to not more than 20% and so as to have a phase difference of 170 degrees to 190 degrees, and when a group of metal elements that satisfies the refractive index n and the extinction coefficient k of k>α*n+β is defined as Group A and a group of metal elements that satisfies the refractive index n and the extinction coefficient k of k<α*n+β is defined as Group B, the alloy is such that the composition ratio is adjusted so that the amount of change in the phase difference is within the range of ±2 degrees and the amount of change in reflectance is within the range of ±0.2% when one or more types of metal element each is selected from the Group A and the Group B and the film thickness of the phase shift film has fluctuated by ±0.5% with respect to a set film thickness (provided that α: proportional constant, β: constant).
1. A reflective mask blank comprising:
a substrate;
a multilayer reflective film formed on the substrate; and
a phase shift film formed on the multilayer reflective film,
wherein the phase shift film comprises an alloy having at least two metal elements, the at least two metal elements including at least one metal element from a Group A and at least one metal element from a Group B, and
wherein a reflectance R is more than 3% and not more than 20%, the reflectance R being a reflectance, to EUV light, of a surface of the phase shift film indicated as a percentage of a reflectance, to EUV light, of the multilayer reflective film in an absence of the phase shift film, and
wherein a phase difference θ of the phase shift film is in a range of from 170 degrees to 190 degrees, and
wherein n and k denote a refractive index and an extinction coefficient, respectively, at a wavelength of EUV light; the Group A is defined as a group of metal elements that have a refractive index n and an extinction coefficient k that satisfy the following formula (1); and the Group B is defined as a group of metal elements that have a refractive index n and an extinction coefficient k that satisfy the following formula (2), and
wherein a composition ratio among the at least two metal elements in the alloy is such that a fluctuation of a film thickness of the phase shift film by ±0.5% relative to a set film thickness results in an amount of change in the phase difference θ that is within a range of ±2 degrees and an amount of change in the reflectance R that is within a range of ±0.2%:
k>α*n+β Formula (1)
k<α*n+β Formula (2)
wherein α and β denote constant values.
2. The reflective mask blank according to claim 1 , wherein the reflectance R is more than 5% and not more than 10%, and
the value of α is −0.303 and the value of β is 0.309.
3. The reflective mask blank according to claim 1 , wherein the reflectance R is more than 3% and not more than 5%, and
the value of α is −0.331 and the value of β is 0.339.
4. The reflective mask blank according to claim 1 , wherein the reflectance R is more than 10% and not more than 20%, and
the value of α is −0.192 and the value of β is 0.194.
5. The reflective mask blank according to claim 1 , wherein the alloy comprises at least three metal elements.
6. The reflective mask blank according to claim 1 , wherein the film thickness of the phase shift film is 25 nm to 70 nm.
7. The reflective mask blank according to claim 1 , wherein a layer of the multilayer reflective film of that is closest to the phase shift film is a protective film.
8. A method of manufacturing a reflective mask from the reflective mask blank according to claim 1 , the method comprising patterning the phase shift film of the reflective mask blank to have a phase shift film pattern.
9. A reflective mask blank comprising:
a substrate;
a multilayer reflective film formed on the substrate; and
a phase shift film formed on the multilayer reflective film,
wherein the phase shift film comprises an alloy having at least two metal elements such that, for a set film thickness of the phase shift film:
a reflectance R has a value R 0 that is one of 4%, 6%, or 12%, the reflectance R being a reflectance, to EUV light, of a surface of the phase shift film indicated as a percentage of a reflectance, to EUV light, of the multilayer reflective film in an absence of the phase shift film, and
a phase difference θ of the phase shift film has a value θ 0 that is 180 degrees, and
wherein a composition ratio among the at least two metal elements in the alloy is such that a fluctuation of a film thickness of the phase shift film by ±0.5% relative to the set film thickness causes the phase difference θ to be within a tolerance range of θ 0 −5 degrees≤θ≤θ 0 +5 degrees and the reflectance R to be within a tolerance range of 0.9 R 0 ≤R≤1.1 R 0 .
10. The reflective mask blank according to claim 9 , wherein, at a wavelength of EUV light, a refractive index of the alloy has a value within the range of from 0.877 to 0.881 and an extinction coefficient of the alloy has a value within the range of from 0.046 to 0.052.
11. The reflective mask blank according to claim 9 , wherein, at a wavelength of EUV light, a refractive index of the alloy has a value within the range of from 0.901 to 0.907 and an extinction coefficient of the alloy has a value within the range of from 0.035 to 0.041.
12. The reflective mask blank according to claim 9 , wherein the alloy comprises at least three metal elements.
13. The reflective mask blank according to claim 9 , wherein the film thickness of the phase shift film is 25 nm to 70 nm.
14. The reflective mask blank according to claim 9 , wherein a layer of the multilayer reflective film that is closest to the phase shift film is a protective film.
15. A method of manufacturing a reflective mask from the reflective mask blank according to claim 9 , the method comprising patterning the phase shift film of the reflective mask blank to have a phase shift film pattern.
16. A reflective mask comprising:
a substrate;
a multilayer reflective film formed on the substrate; and
a phase shift film pattern formed on the multilayer reflective film,
wherein the phase shift film pattern comprises an alloy having at least two metal elements, the at least two metal elements including at least one metal element from a Group A and at least one metal element from a Group B, and
wherein a reflectance R is more than 3% and not more than 20%, the reflectance R being a reflectance, to EUV light, of a surface of the phase shift film pattern indicated as a percentage of a reflectance, to EUV light, of the multilayer reflective film, and
wherein a phase difference θ of the phase shift film pattern is in a range of from 170 degrees to 190 degrees, and
wherein n and k denote a refractive index and an extinction coefficient, respectively, at a wavelength of EUV light; the Group A is defined as a group of metal elements that have a refractive index n and an extinction coefficient k that satisfy the following formula (1), and the Group B is defined as a group of metal elements that have a refractive index n and an extinction coefficient k that satisfy the following formula (2), and
wherein a composition ratio among the at least two metal elements in the alloy is such that a fluctuation of a film thickness of the phase shift film pattern by ±0.5% relative to a set film thickness results in an amount of change in the phase difference θ that is within a range of ±2 degrees and an amount of change in the reflectance R that is within a range of ±0.2%:
k>α*n+β Formula(1)
k<α*n+β Formula(2)
wherein α and β denote constant values.
17. A method of manufacturing a semiconductor device comprising forming a pattern on a semiconductor substrate using the reflective mask according to claim 16 .
18. The reflective mask according to claim 16 , wherein the film thickness of the phase shift film pattern is 25 nm to 70 nm.
19. A reflective mask comprising:
a substrate;
a multilayer reflective film formed on the substrate; and
a phase shift film pattern formed on the multilayer reflective film,
wherein the phase shift film pattern comprises an alloy having at least two metal elements such that, for a set film thickness of the phase shift film pattern:
a reflectance R has a value R 0 that is one of 4%, 6%, or 12%, the reflectance R being a reflectance, to EUV light, of a surface of the phase shift film pattern indicated as a percentage of a reflectance, to EUV light, of the multilayer reflective film, and
a phase difference θ of the phase shift film pattern has a value θ 0 that is 180 degrees, and
wherein a composition ratio among the at least two metal elements in the alloy is such that a fluctuation of a film thickness of the phase shift film pattern by ±0.5% relative to the set film thickness causes the phase difference θ to be within a tolerance range of θ 0 −5 degrees≤θ≤θ 0 +5 degrees and the reflectance R to be within a tolerance range of 0.9 R 0 ≤R≤1.1 R 0 .
20. A method of manufacturing a semiconductor device comprising forming a pattern on a semiconductor substrate using the reflective mask according to claim 19 .