Contact-less electrical defect characterisation of silicon by MD-PICTS

Abstract

The visualisation of so far not detectable defects in electronic grade silicon was achieved by improving the sensitivity of a microwave detection system by several orders of magnitude. This approach to a new detection scheme opens possibilities for a variety of contact-less non-destructive electrical defect characterisation methods which can be applied to high-quality silicon wafers and even to thin epitaxial layers [Dornich K, Grundrig-Wendrock B, Hahn T, Niklas JR. Adv Eng Mater 2004; 598]. Electrical properties such as lifetime, mobility and diffusion length can be measured even at low injection levels with a spatial resolution only limited by the diffusion length of the charge carriers. The doping level of the material plays no major role. Due to the high sensitivity a microwave absorption signal caused by carrier emission from defects can be observed even in high-quality material at low injection levels. This allows for the first time the electrical investigation of the well-known thermal donor (TD) also in electronic grade p-doped silicon, which is not feasible with deep level transient spectroscopy (DLTS). Temperature treatment of such samples allows new insight into the transformation of TDs during annealing. Furthermore, the correlation with photoluminescence (PL) spectroscopy allows for an assignment of deep levels, which can be investigated by microwave-detected–photo-induced current transient spectroscopy (MD–PICTS) [Dornich K, Hahn T, Niklas JR. Freiberg Forschungsh B 2004; 327: 270; Dornich K, Hahn T, Niklas JR In: Proceedings of the MRS spring meeting vol. 864, 2005].