NVM Tunnel Oxide Integration in an Advanced BCD Node and its Impact on GOI

This paper presents the options to integrate tunnel oxide (TOX) in an advanced node Bipolar-CMOS-DMOS (BCD) process and compare their impact on the GOI of TOX. In the case of using silicon nitride a protection layer and Hot phosphoric acid etches (HotPhos) process for its removal, we study its effects to TOX in terms of residual Phosphorus, its clean-up method, and the resulting Gate Oxide Integrity (GOI) through Ramp-to-breakdown (Vbd) and Time-Dependent Dielectric Breakdown (TDDB) measurements. We find that HotPhos significantly degrades GOI and it's not due to the residual Phos it leaves in the shallow surface of TOX. SkinClean process is effective in residual Phosphorus removal but not helpful for GOI improvement.