Charge storage in SiO2 layers with embedded nanoclusters studied by scanning capacitance microscopy

Scanning capacitance microscopy and spectroscopy (SCM/SCS) were applied to study the charge storage, the retention behaviour and the response on dynamic voltage stress of thin SiO2 layers containing Si or Ge nanoclusters. The formation of the nanoclusters was accomplished by ion beam synthesis (IBS) and verified by transmission electron microscopy (TEM). Local charge injection into the implanted layers was performed by applying a dc bias to the metallic probe tip, which was in contact with the SiO2 layer. The dC/dV-curves reveal a shift along the voltage axis compared to an equivalent curve on an unstressed control position. The curve shifts allowed a quantitative analysis of the trapped charge. Monitoring the SCM contrast between an injection spot and its unstressed surroundings over several days allows to visualize the charge decay. The retention time of the stored charge could be estimated from the measured charge decay.