New two-dimensional dopant delineation techniques for sub-micron device characterization

We discuss the sample preparation technique for two-dimensional dopant concentration profiling in silicon based on selective chemical etch in combination with transmission electron microscopy analysis. The mechanism of the etching process and its dependence on the dopant concentration are discussed. The high Spatial resolution and feasibility of the technique are demonstrated by discussing specific applications, concerning the characterization of high speed bipolar and Flash memory EEPROM devices. The main limitations of this method are represented by the impossibility to simultaneously delineate n and p-type regions on the same sample, and by the necessity to have a p(+)n junction for delineating a boron doped region. It is demonstrated these limitations can be overcome by using a selective electrochemical etch based on anodic oxidation of silicon.