Lateral dopant profiling on a 100 nm scale by scanning capacitance microscopy

Abstract

Measurement of dopant density in silicon with lateral resolution on the 100 nm scale has been demonstrated with a “near field” capacitance microscope. The technique is based upon the measurement of local capacitance between a 100 nm tip and the sample surface as the tip is scanned over the surface. The capacitive microscope used to image the iopant is capable of measuring capacitance variations of 3 X 10-22F/√Hz, and previously has demonstrated a 25 nm resolution on metallic surfaces. Dopant imaging is achieved by scanning the tip under feedback control close to a silicon surface, and measuring the capacitance variations. Several types of measurements have been made on the submicrometer scale. First, direct two-dimensional visualization of the dopant in silicon has been achieved by this nondestructive, noncontacting technique. Second, capacitance versus voltage (C-V) measurements have been made with high spatial resolution, providing the means for the measurement of many of the properties of silicon and its oxide. Third, the effects of optical pumping on the local depletion capacitance signal have been observed. Finally, first-order modeling has shown reasonable agreement between theory and experiment, and should provide the means of extraction of dopant density in three dimensions at high resolution. © 1990, American Vacuum Society. All rights reserved.