MOS transient: A powerful analysis technique for in-process monitoring of nuclear detectors

For certain applications such as X-ray spectroscopy, silicon particle detectors require very low leakage currents in order to obtain very good resolutions. Fundamental parametersthat have an influence on the leakage current are the bulk generation lifetime (tg) and the surface generation velocity (Sg). We have developed a simple method of measurement that allows the characterization of these parameters in the beginning, during and after the process. The method makes use of a MOS structure and derives the generation lifetime and surface generation velocity from the measurement of the transition kinetics from overdepletion to equilibrium inversion. These extracted values can be correlated with the leakage current which is inversely proportional to the generation lifetime. The surface generation velocity depends on the density of traps at the wafer surface and can give an idea of the perfection of the wafer polishing. This analysis helps to quantify processes and allows to make a better choice of material.