Evaluation of ONO compatibility with high-k metal gate stacks for future embedded flash products

Embedded flash memories having high-k metal gate-based logic devices will require modifications to the flash cells in order to remain economically feasible. One potential integration scheme is to keep the traditional ONO layer as the flash cell's inter-gate dielectric and replace its poly-Si control gate with the same high-k metal gate stack used for the logic devices. Preliminary electrical tests show that an HfSiON/TiN/a-Si gate stack does not significantly impact the EOT or leakage properties of the ONO layer. This stack is more robust than the traditional ONO with a poly-Si gate.