I present details of novel sample preparation techniques used for delineating two-dimensional dopant profiles in silicon devices. These techniques are based on selective chemical etch of doped silicon in a mixture of hydrofluoric and nitric acid, or simply in buffered HF. The altered topography of the etched surface is imaged by transmission electron microscopy (TEM). Two different strategies will be presented by focusing on their sensitive, resolution, and field of application.

In the first case the silicon device is subjected to the conventional thinning procedure for TEM observations in cross-sectional configuration. The final thickness is obtained by Ar ion milling and it can vary between 50 to 500 nm. Sample is then immersed in a chemical solution containing HF (40%), HN03 (65%), and CH3COOH (95%) in the ratio 1:10:10. In presence of an intense illumination this mixture preferentially etches those device regions which are doped with boron, while in order to delineate n-type regions, the etching procedure must be performed in the dark.