Characterization of vertical RESURF diodes using scanning probe microscopy

Recently, a new process to manufacture vertical RESURF devices was proposed. By using trench etching and subsequent vapor phase doping the alternating p–n junctions in the drift region of such a diode can be formed. For the characterization of these diodes, a two-dimensional (2D) characterization technique is necessary. The use of atomic force microscopy based techniques, such as scanning capacitance microscopy (SCM) and Nanopotentiometry (NP) are nowadays promising tools for the 2D dopant profiling of semiconductor devices. In a first part SCM is used to image the 2D carrier profile of the device, more specific the boron doped layer at the trench sidewalls. A uniform profile is observed along the trench sidewalls. The thickness of the alternating regions in the drift region can be determined with high resolution. Also a semi-quantitative analysis is done with SCM. The concentration in the p-type layer is estimated to be between 1×1017 and 4×1018 at. cm−3. In a second part NP is used to image the evolution of the depletion region within the drift region, when the diode is under reverse bias. For higher voltages the depletion region in the drift region expands. Also a comparison between the experimental results and simulations for NP is presented.