Study on Stability of CrFx Flms for Phase Shifting Mask

Abstract

Chromium fluoride film was thought to be a promising material as phase-shifting mask in deep-UV region. However, it degrades at humid condition. So we studied the degradation phenomena to propose a degradation mechanism of chromium fluoride films. We used several tools such as x-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS), to investigate how the composition and the chemical state change while the degradation proceeds. As a result, we could find that the degradation mechanism of chromium fluoride films can be described by multiple steps, which includes HF gas evolution, Cr-oxide precipitation, and crack propagation. This phenomena occurred all the range of the composition being applicable to the PSM at 193 nm, 248 nm, 365 nm and 436 nm. So it is required the development of other material or careful treatment of chromium fluoride for PSM applications