Soft breakdown of gate oxides in metal-SiO2-Si capacitors under stress with hot electrons

We have investigated the intrinsic dielectric breakdown of gate oxide layers with thickness of 12 and 7 nm in n+ polycrystalline Si-SiO2-Si metal/oxide/semiconductor (MOS) capacitors after stress with constant current either under Fowler-Nordheim or under hot electron injection. Occurrence of soft breakdown without thermal damage in the MOS structure is demonstrated even in a 12 nm oxide under particular stress conditions. In general, it is found that the type of stress determines the breakdown mode (soft or hard).