INVESTIGATION OF ELECTRICAL PROPERTY INHOMOGENEITIES FORMED BY PLASMA ETCHING

Abstract

Electron beam induced current (EBIC) mode of the scanning electron microscope is now widely used fo r the local characterization of semiconductor s t ructures [I-41. In the case of homogeneous materials a lot of methods were proposed f o r such measurements C2,51 but fo r nondestructive characterization of planar s t ruc tures the most suitable is the method based on the measurements of the collected efficiency dependence on electron beam energy [6,71. In many cases the minority carr ier diffusion length is inhomogeneous in depth and fo r reconstruction of its distribution it is necessary t o develop some special techniques. One of such method was proposed in C81. This method is based on the EBIC collected efficiency measurements on the beveled samples as a function of a coordinate along the beveled surface and therefore it demands special preparation of the samples, i.e. it is not nondestructive one. To develop other EBIC techniques f o r the reconstruction of diffusion length profile it is necessary t o have samples with known diffusion length distribution measured by other techniques. Such samples which have the distribution of deep level centers with characteristic length in the range 0.1-1 fim can be produced by reactive ion etching of Si [S] and GaAs [lo]. In the present paper it has been shown tha t the plasma etched Si samples with diffusion length profiles characterized by DLTS can be used a s a model object fo r the diffusion length reconstruction from the EBIC measurements. The diffusion length profile was obtained by fit t ing of the measured collected efficiency dependence on electron beam energy with calculated ones.