ESEM Imaging of P-N Junctions Using a Gaseous Secondary Electron Detector

Abstract

Contrast in secondary electron images of p-n junctions has been observed using a FESEM operating at 1kV. This contrast has been attributed to energy band-bending effects and dopant level variations. In this paper, we report that contrast from the depletion layer of a p-n junction can be obtained in an ESEM using a gaseous secondary electron detector (GSED). The contrast is caused by a signal induced in the GSED by charging and discharging of the device.A 1N4002 p+pn silicon power diode was cross-sectioned along the lead axis to expose the Ag ohmic contacts and the semiconductor device. The section was mechanically polished to an optical finish using diamond abrasives and mounted in a holder which allowed electrical connection to both the p and n sides of the diode. Imaging experiments were performed in a Philips Electroscan XL30 ESEM and a JEOL 6300F below-lens FESEM. Current images were obtained with a GW Electronics 103 specimen current amplifier.