Application of sodium hydroxide in analysis of gate oxide issue of leakage failures

Continuous scale-down of advanced ULSI CMOS technologies has resulted in the corresponding thinning of the gate-oxide thickness in wafer fabrication. Such ultra thinner gate oxide will be more vulnerable to GOI (gate oxide integrity) failures. Potassium hydroxide (KOH) has been reported to be the choice of chemical for etching poly (Chen et al., 1995). But it is so aggressive that over-etch often happens, especially for ultra-thin gate oxide. Thus, in this paper we discuss on the application of sodium hydroxide (NaOH), which has shown a better result for units with I/O (input/output) pin leakage failures. Poly was removed completely without attacking the underlying gate-oxide, and thus it enables us to characterize the physical defects of gate oxide.