Dummy Oxide Removal in High-K Last Process Integration how to Avoid Silicon Corrosion Issue

The industry has diverged into two main approaches for high-k and metal gate (HKMG) integration. One is the so called gate-first. The other is gate-last, also called replacement metal gate (RMG) where the gate electrode is deposited after junctions formation and the high-k gate dielectric is deposited in the beginning of the flow (high-k first-RMG) or just prior to gate electrode deposition (high-k last-RMG) [1-. We can distinguish two RMG process flows called either high-k first or high-k last. In RMG high-k first, poly silicon is removed on top of a TiN etch stop layer whereas on high-k last poly silicon is removed on top of a dummy oxide layer. This dummy oxide has also to be removed in order to redeposit a novel high-k and work function metal (Figure 1).