Characterization of heteroepitaxial silicon germanium carbon layers for metal oxide semiconductor field effect transistor (MOSFET) applications

This study characterizes heteroepitaxially-grown Silicon Germanium Carbon (SiGeC) on silicon for MOSFET applications. To that end, several experiments were designed and conducted to evaluate SiGeC.; Variable Angle Spectroscopic Ellipsometry (VASE) is used to determine the optical constants of a wide array of compositions and thicknesses of SiGeC. Trends are found and used to develop an algorithm for a Spectroscopic Interference Photoreflectometry (SIP) tool to be able to make fast characterizations of unknown material. Thickness characterizations are proven to be very accurate.; Membranes were designed and fabricated for Fourier Transform Infrared Spectroscopy (FTIR) using a low temperature masking technique and potassium hydroxide (KOH) etching. These were then characterized and the presence of substitutional carbon in the SiGeC layers was confirmed.; Direct Photo-Oxidation of SiGeC layers was investigated. High gate leakage currents and interface state densities limit the usefulness of directly photo-oxidized SiGeC for this application.; A SiGeC PMOSFET was designed and fabricated, incorporating a silicon cap layer to eliminate these limitations. Compositions were grown using Rapid Thermal Chemical Vapor Deposition (RTCVD).; Conductivity was examined for activations of medium dose boron implantations in the 400°C to 600°C range. SiGeC does not exhibit a peak in conductivity at low temperature; the conductivity increased over the entire range. Both SiGe and SiGeC showed much higher conductivities than silicon for a given anneal.; The silicon capped structure demonstrated superior oxide formation using photo oxidation, giving breakdown characteristics and interface state densities equivalent to silicon control samples.; The valence band offset of each composition was derived using the capacitance voltage (CV) curve and to estimate the substitutional carbon incorporation. Samples with carbon concentrations less than 1% showed higher substitutional incorporation.; The resulting SiGeC PMOSFETs were measured for mobility and gate delay. The best performing SiGeC transistor demonstrated a mobility of 164 cm 2/V·s, with the best SiGe PMOSFET giving 177 cm2/V·s and the average of the silicon control samples at around 80 cm 2/V·s. The best delay per gate average for a SiGeC composition was approximately 110 nS, with SiGe giving ≈130 nS and the silicon control at ≈220 nS.