Effect of the silicidation reaction condition on the gate oxide integrity in Ti-polycide gate

The effect of the silicidation reaction between the sputtered titanium film and underlying polysilicon on the gate oxide integrity in the Ti-polycide gate was studied. The gate oxide breakdown failure increased with increasing silicidation temperature for both cases of 1-step and 2-step silicidation processes. This is related to increased amount of Ti diffusion from Ti-silicide to the gate oxide. However, for 1-step silicidation process reliability of the gate oxide for 750° C silicidation is better than for 650° C silicidation. This is because of the formation of the metastable C49 structure when solid-state reaction between the sputtered titanium film and underlying polysilicon occurs. Therefore, to obtain better reliablility of the Ti-polycide gate low temperature silicidatlon and the stable C54 phase are essential.