2-DIMENSIONAL CARRIER PROFILING OF INP STRUCTURES USING SCANNING SPREADING RESISTANCE MICROSCOPY

Scanning spreading resistance microscopy (SSRM) is an analytical techn ique originally developed for measuring two-dimensional carrier distri bution in Si device structures with high spatial resolution. It is in essence an atomic force microscope equipped with a conducting tip that is biased relative to the sample. The spreading resistance value deri ved from the measured electrical current is a function of the local ca rrier concentration at the surface region surrounding the probe's tip. In this letter, we report the successful application of SSRM to the a nalysis of InP semiconductor device structures. We imaged a multilayer epitest structure, and a cross section of a three-dimensional structu re in which we observed lateral Zn-dopant diffusion. Comparison of the SSRM profiles with one-dimensional secondary ion mass spectrometry de pth profiles shows good qualitative agreement. SSRM analysis of InP-ba sed device structures was found to be much simpler than that of Si str uctures: there is no need for surface preparation of the cleaved surfa ce, a lower tip force is required, and metal tips, rather than doped d iamond can be used. (C) 1998 American Institute of Physics. [S0003-695 1(98)01241-8].