Reticle haze measurement by spectroscopic ellipsometry

Abstract

Haze formation on reticle continues to be a significant problem for the semiconductor industry. Haze can be formed on the outside pellicle and on the quartz back side of the reticle. Major component of the haze is known to be aluminum sulfate that comes from the reticle cleaning process. The reticle materials, the exposure wavelength, roughness of photomask and this haze will affect the resolution and process latitude. So the haze on the mask surface becomes more important. We need to know the usable lifetime of the reticle in terms of haze and need to know how to increase the lifetime by removing the haze, if possible. This paper introduces the haze measurement method by using the spectroscopic ellipsometry. The quantity of the haze including the roughness of the reticle can be accurately measured by the spectroscopic ellipsometry. The spectroscopic data shows the increase of the delta value with the energy dose given to the reticle. We confirm that this signal increase is directly the result of the haze increase with dose.