Scanning capacitance microscopy analysis of dram trench capacitors

Abstract

Two dimensional dopant concentrations of the side walls of trench capacitor cells of dynamic random access memory devices were profiled using the scanning capacitance microscopy technique. This technique permits the first direct study and semi-quantification of the dopant profiles in the silicon substrate as a function of trench depth. The SCM results indicate that for a fixed trench depth, the dopant profiles in any radial direction of the trench are consistent. However, difference in dopant distribution is clearly revealed between areas that are very close to the top of the trench and those situated deep in the silicon substrate. Variation in the SCM signal at the n+ doped bit-line contacts of the transfer gate transistor is attributed to possibly dopant redistribution during contact formation process.