Apparatus and method for indirect surface cleaning
View Patent ↗Methods for cleaning a surface of a substrate and for increasing the useable lifetime of a photomask substrate are provided. In one method, the surface of a substrate having a contaminating particulate disposed thereon is cleaned by directing a laser towards the substrate, generating a temperature increase in the substrate and transferring thermal energy from the substrate to the particulate to decompose the particulate. The laser has a wavelength that is substantially the same as a local maximum of the substrate absorption spectrum.
1. A method for cleaning a surface of a substrate, comprising:
directing a laser towards a substrate having a contaminating particulate disposed thereon, the laser having a wavelength that is substantially the same as a local maximum of the absorption spectrum of the substrate;
generating a temperature increase in the substrate; and
transferring thermal energy from the substrate to the particulate to decompose the particulate.
2. The method of claim 1 , further comprising directing the laser through a protective material positioned above the substrate.
3. The method of claim 2 , wherein the substrate is at least partially enclosed within a pellicle and the protective material is a pellicle film.
4. The method of claim 1 , wherein laser wavelength is above 8 micrometers.
5. The method of claim 1 , wherein the laser is partially absorbed by the particulate.
6. The method of claim 1 , wherein the substrate includes at least one thin film layer.
7. The method of claim 6 , wherein the thin film layer is patterned and includes void areas under which respective portions of the substrate are exposed.
8. The method of claim 1 , further comprising maintaining a temperature of the substrate below a threshold temperature to prevent damage thereto.
9. The method of claim 1 , wherein the substrate includes at least two materials and the laser wavelength is substantially the same as a local maximum of the absorption spectrum of one of the materials.
10. A method for increasing the useable lifetime of a photomask substrate, comprising:
directing electromagnetic radiation through a protective material towards a substrate having a contaminating particulate disposed thereon, the radiation having a wavelength that is substantially the same as a local maximum of the absorption spectrum of the substrate;
generating a temperature increase in the substrate; and
transferring thermal energy from the substrate to the particulate to decompose the particulate.
11. The method of claim 10 , wherein the photomask substrate is at least partially enclosed within a pellicle and the protective material is a pellicle film.
12. The method of claim 10 , wherein the substrate is quartz and the electromagnetic radiation wavelength is about 9 micrometers.
13. The method of claim 10 , wherein the electromagnetic radiation is partially absorbed by the particulate.
14. The method of claim 10 , wherein the photomask substrate includes at least one thin film layer.
15. The method of claim 14 , wherein the thin film layer is patterned and includes voids under which respective portions of the photomask substrate are exposed.
16. The method of claim 10 , further comprising maintaining a temperature of the photomask substrate below a threshold temperature to prevent damage thereto.
17. The method of claim 10 , wherein the substrate includes at least two materials and the electromagnetic radiation wavelength is substantially the same as a local maximum of the absorption spectrum of one of the materials.
18. A method for cleaning a surface of a substrate at least partially enclosed within a pellicle, comprising:
directing a laser through a pellicle film towards a substrate having a contaminating particulate layer disposed thereon, the laser having a wavelength that is substantially the same as a local maximum of the absorption spectrum of the substrate;
generating a temperature increase in the substrate; and
transferring thermal energy from the substrate to the particulate layer to decompose at least a portion of the particulate layer.
19. The method of claim 18 , wherein the particulate layer is a haze layer.
20. The method of claim 19 , wherein the haze layer is an ammonium sulfate haze layer.