DBIE shape and hardness dependence on gate oxide breakdown location in MOSFET channel

For nMOSFETs stressed in inversion and accumulation modes, the hardness and shape of dielectric breakdown induced epitaxy (DBIE) are strongly dependent on the location of gate oxide (Gox) breakdown in the channel. Regardless of breakdown hardness (i.e. soft or hard), subtle and sharp DBIE is always found close to the edge of the transistor channel. On the other hand, a more gentle and rounded DBIE associated with soft breakdown is found somewhere in the middle of the channel. In this case, hard breakdown with DBIE is hardly detected. The main driving force of the shape and hardness dependence on the channel location is postulated to be the effective resistance associated with the initial Gox breakdown path between the cathode and anode.