Correlation of SIMOX processing and device performance by combined DLTS and transistor analysis

Summary form only given. The authors report that current deep-level transient spectroscopy (DLTS) studies on MOSFETs fabricated in SIMOX (separation by implantation of oxygen) material did not detect any electrically active deep states. As appropriate process control results in reduced deep trap concentrations, DLTS should be complemented by other measurements in order to assess the material and device quality. The SIMOX wafers under investigation were fabricated with implantation doses of 1.4×10¹⁸, 1.8×10¹⁸ , and 2.1×10¹⁸ cm^-2. The implantation energy was 150 keV and they were annealed at 1275°C for 5-10 hours in a N₂+1%O₂ ambient. An epilayer of 0.3 μm was grown on all the substrates prior to device fabrication. Short-channel transistors were fabricated with conventional CMOS technology. It was found that the back-channel mobilities varied from 120-500 cm²/Vs, the threshold voltages from 20-40 V, and the density of interface states from 4×10¹¹ to 2×10¹² cm^-2 eV^-1. In contrast with the back-channel the properties of the front-channel showed much less variation