Plasma passivation of compound semiconductors for device applications.

Abstract

Plasma processing such as PECVD can be used in a variety of ways for both film deposition and surface passivation to improve the performance of solid state devices in both the silicon and compound semiconductor areas. Film properties can be improved over the conventional constant temperature uninterrupted deposition method, and plasma pretreatment can be used to alter the semiconductor surface prior to film deposition. Novel deposition techniques consisting of interrupting the SiO$\sb2$ film deposition for in-situ plasma treatments have been developed to improve the electrical behavior of the plasma SiO$\sb2$-Si interface. The most successful of these was the two-temperature method, where the interface was formed at lower temperature than the rest of the film. Low power hydrogen plasmas were used during the temperature ramp to simulate a conventional MOS post-metallization anneal and reduce the interface trap density. Hydrogen sulfide plasmas were used to passivate the surfaces of both GaAs and InP for subsequent dielectric deposition (SiO$\sb2$). Plasma processing provides a high degree of reproducibility compared to wet chemical processes through computer control of parameters such as chamber pressure, gas flows, temperature, rf power, and exposure time. The electrical and structural properties of the interfaces were characterized with C-V, XPS, SE and PL. The H$\sb2$S treatments were more robust than similar treatments involving nitrogen plasmas. The applicability of these passivation techniques was demonstrated by fabricating metal-insulator-semiconductor FET's on GaAs and InP substrates using a fully ion implaned planar process for both inversion and depletion mode transistors. The sulfide treated samples showed considerable improvement in performance over the control samples.