Lateral Diffusion Distance Measurement of 40–80 nm Junctions by Etching/TEM-Electron Energy Loss Spectroscopy Method

A new technique to measure the lateral diffusion distance of boron has been developed by wet-etching combined with TEM and Electron Energy Loss Spectroscopy (TEM-EELS). The position at a dopant concentration of 5×10 18 cm -3 can be correctly delineated with a spatial resolution of less than 5 nm. This technique is based on the fact that the gradient of the etched surface changes discontinuously at a dopant concentration of 5×10 18 cm -3 . This characteristic appeared for all carrier profiles as long as the etching time was sufficiently long. Etching time optimization is needed because an incubation time exists before the etching starts and because the incubation time depends on carrier distribution. Thickness distribution after the etching is measured by TEM-EELS which enables a high spatial resolution measurement. The lateral diffusion distance at the pn junction measured by this technique was about 0.6 times of the vertical diffusion distance for 40–80 nm junctions. These results were compared with those obtained by an electrical C - V measurement, and were consistent.