pvd process

**Physical Vapor Deposition (PVD/Sputtering)** — depositing thin metal films by physically ejecting atoms from a target material onto the wafer using energetic ion bombardment. **How Sputtering Works** 1. Fill chamber with inert gas (argon) 2. Apply high voltage to ionize argon into plasma 3. Argon ions accelerate toward target (source material) 4. Impact knocks out target atoms (sputtering) 5. Ejected atoms travel to wafer and form thin film **Variants** - **DC Sputtering**: For conductive targets (metals). Simple, high rate - **RF Sputtering**: For insulating targets. Alternating field prevents charge buildup - **Magnetron Sputtering**: Magnets confine plasma near target — much higher rate and efficiency - **Ionized PVD (iPVD)**: Ionize sputtered atoms — directional deposition for filling high-AR features **Applications in CMOS** - Barrier/seed layers for copper damascene (TaN/Ta/Cu) - Metal gate electrodes (TiN, TiAl) - Silicide metals (Co, Ni, Ti) - Bond pad metals (Al) **PVD vs CVD** - PVD: Pure films, good adhesion, directional (poor step coverage) - CVD: Conformal (good step coverage), can fill features, but may have impurities **PVD** is the primary method for depositing metals in semiconductor manufacturing.