Fine pattern fabrication of α-type Ta on a membrane for X-ray mask absorber using ECR ion stream etching

We investigated the etching of alpha-Ta by an ECR ion stream with Cl-2 for use in the x-ray mask process. Fine alpha-Ta patterns with a vertical shape and accurate width were obtained at a low pressure of about 1.5x10(-4) Torr and a high substrate temperature of about 130 degrees C. A temperature control system using He gas was added to the wafer holder to control the membrane temperature during etching. This system enabled us to fabricate uniform 100-nm Ta patterns with precise well shape on a membrane. Over the window region, the variation in pattern width is less than +/-10%.