Achieving high gate quality by wet process improvement

The charge to breakdown (Qbd) is one of the important gate oxide reliability characteristics. This paper describes Qbd problem we experienced before and its mechanism. One is the resist contamination during dry step in oxide wet etch for split gate. Resist reacts with IPA during IPA dry, and it causes Qbd degradation. Another is longer waiting time in DI water rinse step at gate oxide pre cleaning. Longer waiting time in rinse has the possibility to make Qbd worse.