Investigation of chromium contamination induced TDDB degradation in MOSFET

For the first time, we have demonstrated the reliability degradation of gate dielectric due to contamination of chromium in the silicon substrate. Before semiconductor processing, it is difficult to detect the chromium in bare wafer because the Cr-ion is quite low concentration and stable in the Si-sub. Combining time-dependent dielectric breakdown (TDDB) test with Secondary Ion Mass Spectrometer (SIMS) analysis, it performed that the drastically increasing of Cr-ion concentration in the gate oxide during thermal oxidation which decreased the lifetime of TDDB because chromium tends to oxidize and then becomes charged trap in gate oxide. Therefore, the control of Cr-ion concentration is important to increase the gate oxide reliability during semiconductor fabrication.