Temperature gradients during absorber etching and their effect on x-ray mask patterning

Pattern transfer in x-ray mask absorbers is often accomplished by reactivel y etching in chlorine containing plasmas. In this article, we show that the etch rate of one such absorber, TaSi, is a strong function of substrate te mperature. We also show that the etch rate Versus temperature behavior of T aSi is a result of the Ta in the film. Hence, other Ta based absorbers (Ta, Ta4B, TaGe, etc.) may also exhibit a similar behavior. We use finite eleme nt modeling to demonstrate that under cei-tain conditions, significant temp erature variations can exist on a National Institute Standards and Technolo gy (NIST) x-ray mask which in turn can;lead to etch rate variations. We als o present experimental verification of these modeling results. Finally, thr ough modeling, we discuss the effect of this etch rate variation on the pat tern placement accuracy of NIST x-ray masks. (C) 1998 American Vacuum Socie ty. [S0734-211X(98)07506-4].