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High Resolution Measurements of Two Dimensional Dopant Diffusion in Silicon

The development of the very large and ultra large scale integrated technology technology is based on the shrinkage of the lateral dimensions of semiconductors devices to a sub-micron level. Under these conditions the precise control of the total amount of dopant atoms dissolved in the silicon substrate, and of their depth and lateral distribution, become crucial requirements. One of the most promising device characterization technique is that based on transmission electron microscopy (TEM) analysis. Indeed, by means of TEM observations the device morphology can be imaged with a spatial resolution of the order of 0.1 — 0.3 nm; and, after an appropriate sample preparation method, based on selective chemical etch of doped silicon regions, the 2D dopant concentration profiles can be delineated with a resolution of the order of 5nm. The chemical solution used for this aim consists of a mixture of both nitric and hydrofluoric acid.