Anti-reflective coating for optical elements
An optical element including an anti-reflective coating is provided. The optical element includes a silicon substrate and a reflective layer disposed onto a first portion of the surface of the silicon substrate. An anti-reflective layer is disposed onto a second portion of the surface of the silicon substrate such that destructive interference at the anti-reflective layer substantially reduces any reflection of radiation incident on the anti-reflective layer.
1. An optical element, comprising:
a silicon substrate;
a reflective layer disposed onto a first portion of a surface of the silicon substrate; and
an anti-reflective layer disposed onto a second portion of the surface of the silicon substrate,
wherein the anti-reflective layer comprises hafnium oxide (HfOx),
wherein the thickness of the anti-reflective layer is approximately 10 nm, and
wherein the anti-reflective layer is configured to generate destructive interference between light reflected from the anti-reflective layer and light reflected from the silicon substrate in order to substantially eliminate reflection of radiation of a predetermined wavelength incident on the anti-reflective layer.
2. The optical element of claim 1 , wherein the anti-reflective layer has a refractive index that is approximately equivalent to square root of a refractive index of the silicon substrate.
3. The optical element of claim 1 , wherein the anti-reflective layer has a composition and a thickness configured to generate destructive interference of incident radiation at the predetermined wavelength of approximately 193 nm.
4. The optical element of claim 1 , wherein the anti-reflective layer reflects less than approximately 0.2% of incident radiation at the predetermined wavelength of approximately 193 nm.
5. The optical element of claim 1 , wherein the anti-reflective layer comprises an oxide of tantalum, an oxide of titanium, an oxide of niobium, or silicon nitride.
6. The optical element of claim 1 , wherein the reflective layer is substantially reflective to radiation at the predetermined wavelength of about 193 nm.
7. The optical element of claim 1 , wherein the reflective layer comprises one or more of aluminum, an oxide of aluminum, an oxide of silicon, or a fluorinated metallic compound.
8. A lithographic apparatus, comprising:
a support structure configured to support a patterning device that is configured to pattern a beam of radiation from an illumination system; and
a projection system configured to project the patterned beam towards an optical element support configured to support an optical element, the optical element comprising:
a silicon substrate;
an anti-reflective layer disposed onto the entire surface of the silicon substrate,
wherein the anti-reflective layer comprises hafnium oxide (HfOx),
wherein the thickness of the anti-reflective layer is approximately 10 nm, and
wherein the anti-reflective layer is configured to generate destructive interference between light reflected from the anti-reflective layer and light reflected from the silicon substrate in order to substantially eliminate reflection of radiation of a predetermined wavelength incident on the anti-reflective layer; and
a reflective layer disposed onto a portion of a surface of the anti-reflective layer.
9. The lithographic apparatus of claim 8 , wherein the anti-reflective layer has a refractive index that is approximately equivalent to square root of a refractive index of the silicon substrate.
10. The lithographic apparatus of claim 8 , wherein the anti-reflective layer has a composition and a thickness configured to generate destructive interference of incident radiation at the predetermined wavelength of about 193 nm.
11. The lithographic apparatus of claim 8 , wherein the anti-reflective layer reflects less than approximately 0.2% of incident radiation at the predetermined wavelength of about 193 nm.
12. The lithographic apparatus of claim 8 , wherein the anti-reflective layer comprises an oxide of tantalum, an oxide of titanium, an oxide of niobium, or silicon nitride.
13. The lithographic apparatus of claim 8 , wherein the reflective layer is substantially reflective to radiation at the predetermined wavelength of about 193 nm.
14. The lithographic apparatus of claim 8 , wherein the reflective layer comprises aluminum, an oxide of aluminum, an oxide of silicon, or a fluorinated metallic compound.