Retrograde Profile for X-Ray Masks by Molecular Beam Epitaxy
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
X-ray lithography involves fabricating thin, structurally stable masks. One approach is the use of thin silicon membranes that support a gold absorbing layer that is patterned, as desired. This is achieved by using the process depicted in Fig. 1 wherein an oxide diffusion mask is defined to stop boron diffusion in selected areas. Then, in Fig. 2, a heavy boron-doped layer is diffused on both sides of the mask, and acts as an etch stop. In Fig. 3, the oxide is stripped away and then the film is etched as shown in Fig. 4. The boron-doped films are under tensile stress which is required for mechanical stability of the mask. The optical properties of the boron-doped membrane are compromised by the defects in the film that result from the high doping level.