Difficulties in characterizing high-resistivity silicon

High-resistivity silicon (HRS) plays an important role in modern telecommunication IC chips and HR Czochralski (CZ) crystals are gaining more importance. During our study of CZ-HRS wafers, both bulk and Silicon-On-Insulator (SOI), we observed it is not easy to use traditional characterization techniques such as capacitance-voltage (C-V) or resistivity measurement techniques on HRS. During C-V measurements using a Schottky contact directly on HRSOI film we observed a bias spreading effect, where the capacitance was much higher than that due to the gate area. Effects of various factors such as frequency, contact size, light, temperature, and annealing are discussed. The challenges in accurate resistivity measurement using four-point probe, Hall method, and C-V profile are highlighted and a new approach using Impedance Spectroscopy to extract resistivity is discussed.