On measurement of surface impurity profiles of laterally diffused regions

A better understanding for two-dimensional diffused profiles becomes crucial with the trend toward smaller device geometries. However, little experimental data has been available. This paper describes an experiment which extracts the surface impurity profiles near the mask edges from the inversion characteristics of nonuniformly doped surface regions. Test structures for this purpose have been fabricated with a CMOS process. An algo rithm has been developed to extract the surface doping profile in the laterally diffused regions from the IDvs. VGcharacteristics of these devices, The measured profiles are in good agreement with a first-order two-dimensional diffusion model.