X-ray mask fabrication process

Abstract

The Center for X-ray Lithography (CXrL) has developed an x-ray mask fabrication process based on silicon nitride membranes and gold absorber. The LPCVD conditions for the growth of the nitride film produce 2 micrometers thick films with low tensile stress and an optical transmission sufficient for optical alignment. The membranes are formed with an reactive ion etch of the membrane window on the backside nitride, followed by a KOH etch of the silicon wafer. A plating base of 100 angstrom chrome followed by 200 angstrom gold is evaporated on the wafers. The wafer is then mounted on a glass ring using either adhesive or anodic bonding. The absorber pattern is delineated via e-beam lithography into either PMMA or SAL 601. Following resist development and an oxygen plasma cleaning, gold plating is used to produce features of the desired thickness.