A new technique for measuring the lateral diffusion distance of B was developed by combining wet-etching, transmission electron microscopy and electron energy loss spectroscopy. The position, at a dopant concentration of 5 x 1018/cm3, could be correctly delineated with a spatial resolution of less than 5nm. The technique was based upon the fact that the gradient of the etched surface changed discontinuously at a dopant concentration of 5 x 1018/cm3. This occurred for all carrier profiles, provided that the etching time was sufficiently long. Optimisation of the etching time was required because an incubation time occurred before etching began, and because the incubation time depended upon the carrier distribution. The thickness distribution after etching was measured by using transmission electron microscopy and electron energy loss spectroscopy and this gave a high spatial resolution. The lateral diffusion distance at a pn junction, measured using this technique, was equal to about 60% of the vertical diffusion distance for 40 to 80nm junctions.

Lateral Diffusion Distance Measurement of 40-80nm Junctions by Etching/TEM-Electron Energy Loss Spectroscopy Method. Y.Kunimune, N.Nishio, N.Kodama, H.Kikuchi, T.Toda, A.Mineji, S.Shishiguchi, S.Saito: Japanese Journal of Applied Physics - 1, 1999, 38[4B], 2314-8