RELIABILITY STUDY OF SUBMICRON TITANIUM SILICIDE CONTACTS

Kelvin bridge type contact resistance test structures were fabricated for studying the behavior of p-type titanium silicide contacts of sub- micron dimensions. The shallow junctions were formed by using the impl ant through metal (ITM) technique, SIMS profiles showed that the boron concentration at the silicide-si interface was about 2 x 10(20) cm(-3 ), The resulted specific contact resistivity was in the range of (3-6) x 10(-7) Omega . cm(2). For the contacts whose smallest size is 0.5 x 0.5 mu m(2), the contact resistance still increased linearly with the inverse of contact area. Electrical stress test revealed that the sub -micron contacts exhibited degradation phenomena even though a titaniu m tungsten layer was deposited prior to depositing aluminum contact pa ds. In some cases, the degradation rate was found to be dependent on t he polarity of stressing current. This study indicates that the reliab ility of sub-micron contacts needs to be seriously considered.