Plasma-enhanced chemical vapor deposited SiO2/InP interface

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Abstract
Plasma‐enhanced chemical vapor deposited (PECVD) SiO2 using silane and nitrous oxide has previously been used to fabricate metal insulator semiconductor field‐effect transistors (MISFETs) and MISFET integrated circuits on InP. These devices exhibit hysteresis in their curve‐tracer characteristics and drift in the MISFET drain current. The inversion layer electron mobility is also known to vary from sample to sample. These electrical characteristics may be caused by an interfacial oxide. This paper presents x‐ray photoelectron spectroscopy (XPS) depth profiles of the PECVD SiO2/InP interfacial region for various in situ processing. The depth profiles indicate that a native InP oxide is present at all the PECVD SiO2/InP interfaces and that the thickness and composition of the oxide is relatively independent of the in situ chemical treatments. This native oxide appears to be a plasma grown InPO4 with a thickness in the range of 10–25 Å. The composition and topography of air, thermal, and plasma grown oxides without SiO2 deposition were also investigated with XPS and transmission electron microscopy (TEM). For very thin layers, all of these oxides were found to have a similar phosphate composition which is probably InPO4. As the oxide became thicker, the outer layer became depleted of phosphorus and appeared to be primarily In2O3. The topography of the plasma grown oxides was observed to be rougher than that of the thermal or air grown oxides. This roughness could contribute to the reduction of inversion layer mobility.

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