DIRECT COMPARISON OF CROSS-SECTIONAL SCANNING CAPACITANCE MICROSCOPE DOPANT PROFILE AND VERTICAL SECONDARY ION-MASS SPECTROSCOPY PROFILE

The scanning capacitance microscope (SCM) has been shown to be useful for quantitative 2D dopant profiling near the surface of silicon. An a tomic force microscope is used to position a nanometer scale tip at a silicon surface, and local capacitance change is measured as a functio n of sample bias. A new feedback method has been recently demonstrated in which the magnitude of the ac bias voltage applied to the sample i s adjusted to maintain a constant capacitance change as the tip is sca nned across the sample surface. The applied ac bias voltage as a funct ion of position is then input into an inversion algorithm to extract t he dopant density profile. The new feedback approach allows for the us e of a quasi-1D model in the inversion algorithm. Since there are no a lternative 2D dopant profiling techniques which are well established a t present, evaluation of the quantitative character of 2D SCM measured profiles has been a challenge. To avoid this obstacle, we have develo ped sample preparation methods which allow direct comparison of latera l SCM measured profiles on cleaved wafers (cross-sectional plane) with vertical secondary ion-mass spectroscopy (SIMS) profiles. The direct comparison of inverted SCM data and SIMS profiles indicates that quant itative 2D dopant profiling can be achieved by the SCM on a nanometer scale. (C) 1996 American Vacuum Society.