Rc. Taft et Ms. Noell, DEVICE STRUCTURE CHARACTERIZATION USING THE COMPARATIVE CAPACITANCE-VOLTAGE TECHNIQUE, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 12(1), 1994, pp. 332-335
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%).