Silicide conductors reliability research

An investigation into the reliability of polycide conductors has been performed utilizing highspeed CMOS logic circuits (QMOS) and a parametric test circuit, the contact-resistance test vehicle (CRTV). The hermetically-packages QMOS units were split into control- and test-circuit groups; control circuits utilizing standard QMOS processing with n+ polysilicon gates, test circuits utilizing n+ polysilicon/TaSi2 (polycide) gates. Relevant features of the CRTV include long, narrow (2.5 micron to 3 micron) polycide lines connected to overlying Al or Al-1%Si Kelvin-contact patterns through small (1.5 micron x 1.5 micron to 2 micron x 2 micron) interlevel contacts, and large (600 micron x 600 micron) polycide/oxide/silicon capacitors, the (3000 A polysilicon/1600 A TaSi2) polycide being separated from the silicon substrate by an unpatterned, 500 A stream-grown gate oxide. No significant degradation in either CRTV polycide line integrity or CRTV gate-oxide breakdown strength was experienced during 30 cycles of thermal shock (-70 C to +100 C).