High-quality deposited gate oxide MOSFET's and the importance of surface preparation

The fabrication and electrical characteristics of MOSFETs incorporating thin gate oxides deposited by a modified plasma-enhanced chemical-vapor-deposition (PECVD) process are reported. The gate oxide deposition and all subsequent steps were carried out at or below 400 degrees C. These results represent the first demonstration of near-thermal-gate oxide quality. MOSFETs fabricated using a low-temperature PECVD gate oxide process without requiring a high-temperature anneal. The ultimate performance of the deposited oxide devices is shown to be critically dependent on the degree of process induced microroughness of the starting silicon surface. Low-temperature effective mobility measurements are used to compare inversion-layer scattering mechanisms in these devices.>