METHOD OF SELECTIVELY FORMING SILICIDE

摘要

In a crystalline silicon body (1) a shallow trench insulation (2) is made by etching a groove and filling it with silicon oxide. Ridges (11, 12, 13 and 14) of polysilicon are made on the surface of the silicon body (1) by applying a layer of polysilicon and patterning it with a known technique. Spacers (20) of silicon nitride are provided on the side walls of the polysilicon ridges (11, 12, 13 and 14). A first layer (3) of silicon nitride, a second layer (5) of TEOS and a patterned resist layer (7) are applied. The TEOS layer (5) is etched by immersion in a solution of 0.36 % HF for 14 minutes. Subsequently, the resist is stripped in H2SO4 or peroxide. The silicon nitride layer (3) is etched by immersion in phosphoric acid of 1650 DEG C for 15 minutes using the TEOS layer (5) as a mask. A titanium layer is applied. Subsequently, the body is rapidly heated to a temperature of 760 DEG C at which it is kept for 20 seconds. During this rapid thermal treatment titanium silicide (20, 21) is formed at locations where the titatium is in contact with silicon i.e. on top of the polysilicon ridges (12, 13 and 14) and also on the exposed crystalline regions (23 and 24).