Ultrafine mask cleaning technology using ultraviolet irradiation

The contact-free photomask cleaning using the UV irradiation has been studied. With the UV from the low pressure mercury lump, we can clean a photomask preventing the mask plate from any contacts with chemicals or DIW in the cleaning process steps. We can be free from any residua or waterprints in the photomask cleaning process process steps by UV. In the UV cleaning, we have observed the position selective cleaning effect. The dependence of the cleaning effect on the particle size has also been observed. As a result of a series of experiments, we can conclude that the cleaning effect strongly depends on the heat stored in the contamination. The chromium thinning free cleaning conditions is also examined.