Lateral nonuniformity of effective oxide charges in MOS capacitors with Al/sub 2/O/sub 3/ gate dielectrics

The high-frequency Terman´s method for interface-trap-density (D _it) extraction is used to examine the lateral nonuniformity (LNU) of effective oxide charges in MOS capacitors. The two-parallel-subcapacitor model is constructed to simulate LNU charges, and it was shown that the value of the found effective D_it appears negative as the LNU occurs in the gate oxide. This technique was first used to examine the effective oxide charge distribution in Al₂O₃ high-k gate dielectrics prepared by anodic oxidation and nitric-acid oxidation. It was found that the LNU effect in Al₂O₃ is sensitive to oxidation mechanisms and can be avoided by using an appropriate oxidation process. The proposed technique is useful for the preparation and reliability improvement of high-k gate dielectrics