A multilayer resist (MLR) scheme for the manufacturing of sub-0.25-mum x-ray masks has been developed. MLR facilitates the generation of high-aspect ratio patterns by electron beam lithography and dry etching. The top three layers are standard MLR structures : a thin imaging resist layer, a thin intermediate layer, and a thick organic underlayer. Previously, others have used spin-on-glass or silicon nitride for the intermediate layer [R. Viswanathan, R. Acosta, D. Seeger, H. Voelker, A. D. Wilson, 1. Babich, J. Maldonado, J. Warlaumont, O. Vlad’imirsky, F. Hohn, D. Crockatt, and R. Fair, Microelectron. Eng. 9, 93 (1989). A. Huberger, Microelectron. Eng. 5, 3 (1986)]. Sufficiently, thin low-stress tantalum or tungsten was utilized to provide oxygen reactive-ion etching resistance. The following layers are utilized under the MLR stack : another thin tantalum or tungsten etch stop layer; a thin gold plating base; and finally a 2.5-mum silicon membrane. Low image size bias dry etch processes that were successfully developed and performed on the thin x-ray mask membranes using a specially modified Plasma-Therm model 720 etch tool capable of automatically handling x-ray masks are described. Also, studies of membrane surface temperature as a function of plasma conditions are presented. Other dry etch processing issues that are driven by the uniqueness of processing on a membrane substrate and by the uniqueness of the x-ray mask fabrication process are discussed. Lastly, mask pattern distortion issues associated with MLR processing are examined.