Epitaxial staircase structure for the calibration of electrical characterization techniques

Abstract

Frequently electrical characterization techniques [such as the spreading resistance probe (SRP)], rely on the availability of a set of well-calibrated, homogeneously doped Si samples to establish the calibration curves (and parameters) necessary for the conversion of resistance measurements into carrier profiles. Although ideally such a calibration should be verified daily, in practice, time considerations limit the daily verification to one (or a few) calibration samples. To remedy this situation a special multilayer Si structure has been grown consisting of a decreasing B-doped staircase containing seven flat 4–5 μm thick calibration layers doped from 1020/cm3 down to 1015/cm3 separated by slightly (factor 2–3) higher doped 1–2 μm thick interface layers. The latter are included to facilitate the SRP calibrations as the SRP correction factor within the calibration layers now becomes very close to one. Since presently, a calibration curve can be generated quickly from a single measurement, daily measurements over a period of several months clearly indicate concentration-dependent drifts of the SRP-calibration curve. In addition to the calibration purposes we will demonstrate that this sample also can be used for the direct comparison of SRP, nano-SRP, scanning capacitance microscopy (SCM), and selective etching, etc. in terms of their dynamic range, quantification properties, and sensitivity.