DETERMINATION OF DOPANT-CONCENTRATION DIFFUSION LENGTH AND LIFETIME VARIATIONS IN SILICON BY SCANNING ELECTRON-MICROSCOPY

Compositional variations in Czochralski-grown silicon doped at levels above 1018/cm3 were observed with SEM in the EBIC mode employing large-area shallow p-n junctions. The EBIC contrast attributed to minority-carrier diffusion-length variations was related to dopant-concentration variations. Quantitative determination of dopant concentration, diffusion length, and lifetime variations on a microscale was obtained from the analysis of electron-beam-induced current measurements employing a model based on steady-state low-level excitation of minority carriers by the electron beam and on a phenomenological depth-dose function.