Photomask blank, photomask, and photomask manufacturing method
A photomask blank and a photomask having favorable wafer transfer characteristics and irradiation resistance. A photomask blank is for fabricating a photomask for an exposure wavelength of 193 nm, the photomask blank comprising: a light-transmissive substrate; a phase shift film formed on the light-transmissive substrate and providing phase shift effects of a light transmittance of at least 30% with respect to exposure light; and a light-shielding film formed on the phase shift film. The phase shift film is constituted by lamination of: a first phase shift film (that uses a silicon nitride-based material, has a refractive index n1 of 2.5 to 2.7, and an extinction coefficient k1 of 0.2 to 0.4; and a second phase shift film that uses a silicon oxynitride-based material, has a refractive index n2 of 1.55 to 2.20, and an extinction coefficient k2 greater than 0 but no greater than 0.1.
1. A photomask blank used for fabricating a photomask to which an exposure light with a wavelength of 193 nm is applied, the photomask blank comprising:
a light-transmissive substrate;
a phase shift film formed on the light-transmissive substrate and providing a phase shift effect; and
a light shielding film formed on the phase shift film,
wherein the phase shift film is composed by laminating
a first phase shift film using a silicon nitride-based material, and
a second phase shift film using a silicon oxynitride-based material,
the phase shift film has a light transmittance of 30% or more with respect to the exposure light,
the first phase shift film has a refractive index n1 of 2.5 or more and 2.75 or less, and the second phase shift film has a refractive index n2 of 1.55 or more and 2.20 or less,
the first phase shift film has an extinction coefficient k1 of 0.2 or more and 0.4 or less, and the second phase shift film has an extinction coefficient k2 that is greater than 0 and no greater than 0.1, and
a total film thickness of the phase shift film is greater than 70 nm and is 114 nm or less.
2. The photomask blank of claim 1 ,
wherein the phase shift film is composed by laminating the second phase shift film on the first phase shift film that is formed on the light-transmissive substrate.
3. The photomask blank of claim 1 ,
wherein in the phase shift film, a film thickness D1 of the first phase shift film and a film thickness D2 of the second phase shift film satisfies the following relationship:
D 1(nm)>−0.5· D 2(nm)+45 nm, and
D 1(nm)<−0.5· D 2(nm)+75 nm.
4. The photomask blank of claim 1 ,
wherein the light shielding film is substantially not etched by fluorine-based dry etching and is capable of being etched by oxygen-containing chlorine-based dry etching, and has a chromium content of 20 atomic % or more.
5. A photomask to which an exposure light with a wavelength of 193 nm is applied, the photomask comprising:
a light-transmissive substrate, and
a circuit pattern which is a pattern formed on a phase shift film laminated on the light-transmissive substrate,
wherein the phase shift film is composed by laminating
a first phase shift film using a silicon nitride-based material, and
a second phase shift film using a silicon oxynitride-based material,
the phase shift film has a light transmittance of 30% or more with respect to the exposure light,
the first phase shift film has a refractive index n1 of 2.5 or more and 2.75 or less, and the second phase shift film has a refractive index n2 of 1.55 or more and 2.20 or less,
the first phase shift film has an extinction coefficient k1 of 0.2 or more and 0.4 or less, and the second phase shift film has an extinction coefficient k2 that is greater than 0 and no greater than 0.1, and
a total film thickness of the phase shift film is greater than 70 nm and is 114 nm or less.
6. The photomask of claim 5 ,
wherein the phase shift film is composed by forming the first phase shift film on the light-transmissive substrate, and further laminating the second phase shift film on the first phase shift film.
7. The photomask of claim 5 ,
wherein in the phase shift film, a film thickness D1 of the first phase shift film and a film thickness D2 of the second phase shift film satisfies the following relationship:
D 1(nm)>−0.5· D 2(nm)+45 nm, and
D 1(nm)<−0.5· D 2(nm)+75 nm.
8. The photomask of claim 5 ,
wherein the photomask comprises a light shielding film laminated on the phase shift film positioned at a periphery portion of an effective area including the circuit pattern, and,
the light shielding film is substantially not etched by fluorine-based dry etching and is capable of being etched by oxygen-containing chlorine-based dry etching, and has a chromium content of 20 atomic % or more.
9. The photomask of claim 8 ,
wherein a light transmittance to the exposure light of a laminated film combining with the light shielding film and the phase shift film provided on the periphery portion is 0.1% or less.
10. A photomask manufacturing method using the photomask blank of claim 1 , comprising:
forming a pattern on the light shielding film by performing dry etching using an oxygen-containing chlorine-based gas to the light shielding film;
forming a circuit pattern and a periphery portion pattern that forms a periphery portion of an area including the circuit pattern on the phase shift film, by performing dry etching using a fluorine-based gas to the phase shift film using the pattern formed on the light shielding film as a mask;
forming a resist pattern on the periphery portion pattern, and performing dry etching using an oxygen-containing chlorine-based gas using the resist pattern as a mask to remove a portion of the light shielding film; and
removing the resist pattern.