Scanning capacitance microscopy: A tool for the detection of localized charges in semiconductors on a nanoscale

摘要

A challenge in the present semiconductor technology is the knowledge of doping profiles and localized charge distributions. As the device dimensions unswervingly shrink, new concepts and methods are required for 2D and 3D profiling of charge carrier distributions in real device structures. Scanning probe techniques are suitable to provide spatially resolved information about surface properties of electronic materials. Specific extensions such as scanning capacitance microscopy (SCM) are aimed to study the local electric behaviour of surfaces and thin layers. Though the method has been established more than a decade ago, its breakthrough was retarded in the past by a lack of quantitative understanding. The intention of this contribution is to address the following two issues: first, how to detect and resolve the location of semiconductor hetero- and homojunctions, with a special emphasis on the role of the surface passivation layers, and second, the verification of trapped charges in oxide layers containing semiconductor nanoclusters. The latter in particular should demonstrate, how quantitative trapping parameters such as the trap density or the charge retention time can be derived from SCM measurements.