The Effect of LaB sub 6 Cathode Shape on its Performance in a JBX 5DII Electron Beam Lithography System.

The focused beam size and current for a JBX 5DII electron beam lithography system was measured for various shaped, (100) single crystal LaB sub 6 cathodes at 50 kV beam voltage. The performance of a 90degree full angle, conically shaped cathode with a 15micron spherical apex radius was compared with a similar cathode, but with a variable diameter flat at the cathode apex. As the flat size varied from 15 to 30micron, the minimum beam size (for 50 pA of beam current) varied from 11 to 37 nm for a cathode temperature of 1830K. The performance of the 15micron truncated compared favorably with the 15micron spherical shaped cathode. For larger beam diameters, the beam current for the truncated cathode exceeded that of the 15micron spherical shaped emitter. The truncated cathode was operated in excess of 3100 hrs. with no performance degradation.