Apparatus and method for indirect surface cleaning
View Patent ↗Methods for cleaning a surface of a photomask and for increasing the useable lifetime of the photomask are disclosed. One method includes, a first wafer print processing using a photomask and a pellicle disposed across the photomask, and cleaning the photomask. The cleaning the photomask includes directing a laser beam through the pellicle toward the photomask, the laser beam having a wavelength that is substantially equal to a local maximum of an absorption spectrum of the photomask, heating the photomask with the laser beam, and transferring heat from the photomask to a contaminant disposed on the photomask, thereby thermally decomposing the contaminant.
1. A wafer fabrication cleaning process, comprising:
directing an energy source toward a photomask, the energy source including a wavelength that is substantially equal to a local maximum of an absorption spectrum of the photomask;
heating the photomask with the energy source; and
transferring heat from the photomask to a contaminant disposed on the photomask, decomposing the contaminant.
2. The process of claim 1 , further comprising directing a gas flow onto a pellicle disposed across the photomask to control a temperature of the pellicle.
3. The process of claim 1 , wherein the photomask includes a thin film layer disposed thereon.
4. The process of claim 3 , wherein the thin film layer is patterned and includes void areas under which respective portions of the photomask are exposed.
5. The process of claim 1 , further comprising maintaining a temperature of the photomask below a threshold temperature to prevent damage thereto.
6. The process of claim 1 , wherein the contaminant is a contaminant layer.
7. The process of claim 6 , wherein the contaminant layer is a haze layer.
8. The process of claim 7 , wherein the haze layer includes ammonium sulfate.
9. The process of claim 6 , wherein the contaminant layer is inorganic.
10. The process of claim 1 , wherein the wavelength of the energy source is selected to effect absorption of an energy from the energy source by the photomask.
11. The process of claim 1 , wherein the contaminant is a particle.
12. The process of claim 11 , wherein the particle contains ammonium sulfate.
13. The process of claim 1 , further comprising a first wafer print processing using the photomask before the directing the energy source toward the photomask.
14. The process of claim 13 , further comprising a second wafer print processing using the photomask, the second wafer print processing occurring after the decomposing the contaminant.
15. The process of claim 14 , further comprising post-print wafer processing after the second wafer print processing.
16. The process of claim 15 , further comprising pre-print wafer processing before the first wafer print processing.