silicide agglomeration

**Silicide Agglomeration** is a **degradation mechanism where a continuous silicide film breaks up into isolated islands** — driven by grain growth and surface energy minimization at elevated temperatures, causing dramatic increases in sheet resistance and contact resistance. **What Causes Agglomeration?** - **Driving Force**: The silicide film minimizes its total surface energy by reducing its surface area -> breaks into spherical/hemispherical islands. - **Temperature**: NiSi agglomerates above ~600-700°C. CoSi₂ above ~800°C. TiSi₂ is relatively stable. - **Narrow Lines**: Worse on narrow features because the surface-to-volume ratio is higher. **Why It Matters** - **Thermal Budget**: Sets a maximum temperature for all processing steps after silicide formation. - **NiSi Challenge**: NiSi's low thermal stability makes it vulnerable to agglomeration during subsequent anneals. - **Solutions**: Alloying (NiPtSi instead of NiSi delays agglomeration by ~100°C), capping layers. **Silicide Agglomeration** is **the melting of the contact layer** — where thermal energy breaks the continuous conductive film into useless islands, destroying the electrical connection.