k first process

**High-k First** is an **HKMG integration variant where the high-k dielectric is deposited early (before dummy gate removal)** — the high-k layer is formed on the channel before the dummy gate and survives all subsequent processing, while the metal gate is deposited during the RMG step. **High-k First Process** - **Deposit High-k**: Deposit interfacial oxide + high-k dielectric on the channel surface. - **Dummy Gate**: Deposit and pattern the sacrificial poly-Si gate on top of the high-k layer. - **S/D Processing**: Standard S/D formation and high-temperature anneal (high-k is in place and experiences this anneal). - **RMG**: Remove dummy poly → deposit metal gate into the trench (on top of the pre-existing high-k). **Why It Matters** - **Interface Quality**: The high-k/channel interface is formed on a pristine surface before any S/D processing. - **Anneal**: High-k receives the S/D anneal — improves high-k crystallization and interface quality. - **Trade-Off**: Better interface quality but less flexibility in high-k thickness and composition. **High-k First** is **placing the dielectric early** — forming the critical high-k/channel interface on a clean surface before subsequent processing steps.