Cathodoluminescence microscopy of semiconductor devices using a novel detector with high collection and backscattered electron rejection efficiency

Abstract

An optically optimized light collector suitable for both panchromatic and spectroscopic cathodoluminescence (CL) analysis in the scanning electron microscope (SEM) is described. The light collector is a semiellipsoidal mirror of high ellipticity which ensures high optical coupling with a light guide to a monochromator. A light collection efficiency of over 85% is achieved. A high backscattered electron efficiency of better than 90% is achieved by using a low atomic material for the light collector. The high collection efficiency of the system allows CL images to be obtained from a cold field emission SEM with low total beam current. Examples of CL images obtained for semiconductor devices are shown to illustrate the high collection efficiency and high backscattered electron rejection efficiency of the system. With the system, a new CL contrast mechanism was observed in a silicon device with a passivation layer of Si3N4/a-SiO2 The contrast was observed between the Si3N4/a-SiO2/metal and the Si3N4/a-SiO2/SiO2 (thermal)/Si regions. The system was also used to monitor the hot-electron-injection-induced 2.7eV luminescence centres and the interfacial stress dependence of the 2.7eV CL peak build-up in SiO2-Si structures.