Decrease in gap states at ultrathin SiO2/Si interfaces by crown-ether cyanide treatment

A simple method to passivate interface states at ultrathin SiO2/Si interfaces is developed. In this method, ultrathin SiO2-covered Si is immersed in a KCN solution containing crown-ether, followed by a rinse in water at 25 degreesC. The conductance-voltage measurements show that the interface state density is decreased to similar to1/10 by this crown-ether cyanide treatment. The capacitance-voltage measurements show that contamination by K+ ions is effectively avoided by the inclusion of crown-ether. These results demonstrate that crown-ether molecules effectively capture K+ ions and consequently CN- ions effectively may react with defect states, probably forming Si-CN bonds. The passivation of interface states by the cyanide treatment improves the electrical characteristics of metal-oxide-semiconductor tunneling diodes. (C) 2000 American Institute of Physics. [S0003-6951(00)04351-5].