High H2 ash process applications at advanced logic process

Abstract

Both shallow junction and HKMG have been integrated into the advanced logic process. This leads to the introduction of forming gas (4% H2 in N2/H2 mixture) to replace the traditional O2-based ashing process for the sake of material loss and metal oxidization in Lightly Doped Drain ash. In this work, we focused on the high volume H2 ashing not only from the point of view of physical performance but also the yield enhancement. Compared with conventional forming gas ash process, high H2 ash process delivers superior photo resist removal capability, much less Si loss and higher throughput at high-dose implant strip. Besides, Si-C bond after p-MOS Si recess etch could inhibit SiGe epitaxy, thus resulting in defect. We proved that high H2 ash process could effectively remove the Si-C bond at EPI surface and greatly reduce the SiGe EPI defect count. In Static Random Access Memory vehicle, high H2 process delivers >10% Vmin yield enhancement. In brief, high H2 ashing process can benefit throughput, photo resist removal capability and yield enhancement for HKMG process.