Non-quasistatic simultaneous HF/LF-CV measurements for rapid characterization of MOS structures

We report rapid, nbn-quasistatic CV (capacitance-voltage) measurements for a comprehensive characterization of MOS structures. The purpose is to speed up and simplify the characterization of simple MOS test structures in a process line environment. This approach replaces the time-consuming successive application of several CV tools by one accurate and rapid technique. Contrary to quasistatic CV measurements, the use of faster gate voltage ramp rates enables a drastic reduction of the total time for the data acquisition for the characterization of high quality silicon MOS structures. The simultaneous measurement of the high frequency (HF)- and the low frequency (LF)-MOS capacitance from deep depletion toward accumulation in a non-quasistatic mode permits the determination of the density of fast interface states D-it(E) from midgap to the flatband energy level, the generation lifetime tau(g)(x(g)), and the doping profile N(x(d)). The doping profile is corrected for voltage stretch out due to the generated inversion charge and recharges of interface traps. To speed up the relaxation process for the determination of the generation lifetime, a gate voltage ramp was used after pulsing into deep depletion, instead of a constant voltage. Driving the MOS capacitor from deep depletion toward accumulation with a linear gate voltage ramp causes a rapid relaxation of the depleted MOS capacitor to the equilibrium state. To calculate; the generation active depletion width x(g), the equilibrium depletion width in inversion x(f) must be known, x(f) can be conveniently determined from the sharply marked equilibrium point at the transition from generation to recombination. Consequently no extra measurement time is required for the determination of x(f). The technique proposed is also applicable for the characterization of MOS capacitors with very thin oxides below 10 nm. Published by Elsevier Science Ltd. All rights reserved.