Materials science aspects of dielectric film compositions in the planar technology of Ge-based MIS structures

Abstract

A new fabrication route for Ge based metal-insulator-semiconductor (MIS) transistors has been developed based on materials research of dielectric layer compositions. Unwanted impurities were encapsulated in the Ge substrate by using the gate-first process and a modified thermal GeO₂ layer with increased viscosity at the interface with the Ge substrate. Increasing the density of the oxide layer near germanium interaction with the deposited Si₃N₄ film hindered diffusion of the impurities adsorbed by the substrate surface into the transistor channel. This increased the electron mobility in the MIS transistor and prevented its decrease at cryogenic temperatures.