salicide (self-aligned silicide)

**Salicide** (Self-Aligned Silicide) is the **self-aligned process for forming silicide simultaneously on the gate, source, and drain** — without requiring a separate lithography mask, because the silicide reaction occurs selectively only on exposed silicon surfaces. **How Does Salicide Work?** - **Key**: Spacers (SiN/SiO₂) on the gate sidewalls protect the gate-to-S/D junction. - **Process**: Blanket metal deposit -> Anneal (silicide forms on Si, not on spacer/STI) -> Wet etch unreacted metal -> Second anneal. - **Self-Alignment**: No mask needed. The gate, spacers, and STI define where silicide forms. **Why It Matters** - **Cost**: Eliminates one lithography step (no silicide block mask needed for standard transistors). - **Alignment**: Perfect alignment guaranteed by the device geometry itself. - **Silicide Block (SAB)**: Some analog devices intentionally block silicide using an extra mask to control resistance (e.g., precision resistors). **Salicide** is **geometry-driven metallization** — letting the device structure itself determine where the conductive silicide forms, without human alignment.