Improved E-Beam Proximity Mask
Original Publication Date: 1988-Apr-01
Included in the Prior Art Database: 2005-Feb-15
Heat and charge dissipation is improved when chemical vapor deposition (CVD) selective tungsten is used as a coating for electron beam proximity masks used in the fabrication of semiconductors. Basically, the purpose of an proximity mask is to image a pattern on a silicon (Si) wafer with an electron beam. To fabricate such a mask, boron is diffused into the top and side surfaces of a wafer to a depth of approximately 2-6 microns as an etch stop. The wafer is then placed in a anisotropic etch solution. The etch solution acts only on the back side of the wafer and etches the silicon to within 2-6 microns of the front surface where the etchant encounters the boron etch stop. The result is a silicon membrane shown in Fig. 1. Fig.