The impact of organic contamination on the oxide-silicon interface

This paper collects the results of a study aimed to investigate the impact of organic contamination on the electrical properties of the silicon oxide and of the silicon oxide-silicon interface. Some wafers were contaminated by immersion in solution of diethylphthalate (DEP) in solvent. The wafers were then oxidized to perform surface recombination velocity measurements by Elymat, and capacitors were fabricated for capacitance vs. voltage and capacitance vs time measurements. In addition, the interface state density was measured by the MOS-DLTS technique and the gate oxide integrity was evaluated by constant current stress. Elymat measurements of surface recombination velocity show that surface recombination velocity is increased by organic contamination. From the point-of-view of the intrinsic properties of the silicon oxide-silicon interface, MOS-DLTS showed the most significant effects. These measurements allowed identifying a band of interface states located around E v+0.1eV as related to organic contamination. However, the most relevant effects of organic contamination were observed by electrical stress of the oxide. Indeed, the fraction of capacitors with degraded breakdown voltage increased dramatically in contaminated wafers.