Quantitative Scanning Capacitance Microscopy

Scanning capacitance microscopy is an analytical technique able to provide direct carrier distribution information on the nanoscale using HF amplitude detection and lock-in techniques. For the reliability analysis of semiconductor devices also defect characterisation is necessary on the nanoscale. On the micrometer-scale the important parameters of deep defects in semiconductors (emission barrier energy, capture cross section, defect distribution) are determined by deep level transient spectroscopy where capacitance transients are measured with period widths ranging between microseconds and several seconds as a function of temperature. We designed an HF coaxial resonator with a resolution of 5.8×10−21F/Hz1/2 in combination with an IQ-demodulator system for temperature-dependent quantitative static and dynamic capacitance measurements on the nanoscale around the resonance frequency of ca. 2.2GHz of the sample-resonator unit. First results from isothermal spectroscopy measurements on a n-type conducting GaAs sample (n=1018cm−3) with native oxide reveal a “textbook” CV plot shifted on the voltage axis due to mobile ions.