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 Spectr oscopy (TEM-EELS). The position at a dopant concentration of 5 x 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 surfa ce changes discontinuously at a dopant concentration of 5 x 10(18) cm(-3). This characteristic appeared for all carrier profiles as long as the etchin g time was sufficiently long. Etching time optimization is needed because a n incubation time exists before the etching starts and because the incubati on time depends on carrier distribution. Thickness distribution after the e tching is measured by TEM-EELS which enables a high spatial resolution meas urement 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 electri cal C-V measurement, and were consistent.