Near neighbor chemical bonding effects on Si atom native bonding defects in silicon nitride and silicon dioxide insulators

Abstract

There has been considerable interest in the use of deposited thin films of Si3N4 and SiO2 as gate insulators and/or passivation layers for compound semiconductors. This is contingent on a low temperature deposition process which: (a) produces insulators which are effectively free of native bonding defects and impurity atoms, and at the same time (b) minimizes chemical degradation, and the associated generation of interfacial defect states at the compound semiconductor surfaces. Recently, the group at North Carolina State University and The Research Triangle Institute has developed a low temperature, remote plasma-enhanced chemical vapor deposition (CVD) process for depositing trilayer gate insulators consisting of SiO2–Si3N4–SiO2 layers onto p-type (In,Ga)As to produce high gain, stable, n-channel conducting field-effect transistor (FET) devices. The processing chemistry for the deposition of these Si3N4 and SiO2 layers prevents the incorporation of significant amounts of chemical impurities in the form of oxygen atoms in the Si3N4, and hydrogen and nitrogen atoms in the SiO2. This paper addresses the question of native bonding defects in Si3N4 and SiO2, and considers the effects of near neighbor impurity atoms on the gap state energies of two types of defects, Si dangling bonds and Si–Si bonds.