EVALUATION OF BERYLLIUM FOILS FOR X-RAY-LITHOGRAPHY BEAMLINES

A commonly used exit window material for x-ray lithography beamlines i s beryllium, which combines a high degree of transparency to x rays wi th photon energies greater than 1000 eV, with the material strength th at allows the use of thin windows that can support atmospheric pressur e. The mechanical and x-ray transmission properties of beryllium foils are dependent on the purity of the initial materials and the fabricat ion technique used in the foil formation. An evaluation of the strengt h and x-ray transmission of foils prepared by using different initial materials and different techniques is presented. Improvements in expos ure uniformity that are obtained by scanning to average the x-ray tran smission variations are discussed.