Influence of back-end thermal processing on polysilicon-monosilicon contact resistance due to dopant deactivation

The effect of post-planarization rapid thermal anneal (RTA) steps on polysilicon-monosilicon contact resistance is critically dependent on the thermal requirements of the specific planarization technique used. While these RTA steps were found to increase R_c,polyn+/ for chemical mechanical polishing (CMP) type low or zero thermal budget back-end processes, they decreased R_c,polyn+/ when furnace glass reflow anneals were used. For a CMP back-end process when a high temperature (⩾1000°C) RTA is used to form the shallow n⁺ emitter junction, all subsequent anneals need to be carefully optimized to avoid drastic increases in R_c,polyn+/-for a 1065°C emitter RTA and 850°C RTA process, a 700°C RTA caused a 62% increase for a 30 sec anneal and a 125% increase for a 300 sec anneal