A new model of haze generation and storage-life-time estimation for mask

Abstract

After quartz blanks with various sulfate ion amount on the surfaces were exposed by an ArF laser, growing defects, haze, on the surfaces were consequently counted by an inspection tool. As a result, the number of haze largely depends on the sulfate ion amount, and it is found that no haze is generated when the sulfate ion amount is smaller than a threshold value. A new haze generation model is provided to explain the threshold phenomenon. And then storage impact on increase of the sulfate ion amount was investigated. The sulfate ion amount increases with storage time and airborne SO_x concentration. From the results, the adsorption coefficient of an extended Langmuir equation was calculated, and the adsorption phenomenon was analyzed in detail. Simulation results show that it is recommended, regarding for storage environment, to keep under 0.01 ppbv airborne SO_x concentration in order to prevent haze for one year.