DEVICE STRUCTURE CHARACTERIZATION USING THE COMPARATIVE CAPACITANCE-VOLTAGE TECHNIQUE

Although the C-V profiling technique is usually applied to obtain the doping concentration of lightly doped wells, here we extend it to extr act structural information of high-performance double poly bipolar tra nsistors (BJTs) by comparing profiles taken from two adjacent but dist inct C-V structures. In particular, the trenching that occurs in unpro tected substrate silicon during the gate (base) poly overetch can be m easured by the change in p + source/drain implant to n + buried layer depletion width for two such diodes, one with and one without trenchin g. The diffused extrinsic base junction depth of the double-poly BJT c an be extracted similarly. Both of these physical dimensions must be a ccurately measured and tracked, to optimize bipolar device performance . Structural measurements by this comparative C-V technique are nondes tructive, simple, and agree with scanning electron microscopy and seco ndary ion mass spectroscopy within approximately 100 angstrom (5%).