Improved instrument for probing static potential profiles in semiconductor devices

Improvements to the positional accuracy of point-contact probes permit smaller features to be investigated in higher-doped semiconductors. An xy stage with an accuracy of within 0¿5 ¿m has been developed for use with an etched-tungsten probe with a tip radius of about 0.5 ¿m. The probe is constrained to move in a vertical plane by a special cone-pivoted arm so that it can be raised and lowered repeatedly over a fixed point while the sample is moved underheath it. This arm is also counterbalanced so that the probe pressure can be finely controlled. The effectiveness of these measures has been assessed by probing a known (Schottky barrier) potential; an error of 15% over 5 ¿m is typical.