cavity formation

**Cavity formation** is the **process of creating enclosed internal space within a package or bonded wafer stack to allow mechanical movement or controlled atmosphere** - it is fundamental in many MEMS and sensor package architectures. **What Is Cavity formation?** - **Definition**: Manufacturing of void regions by etch, spacer, or cap-wafer design techniques. - **Functional Purpose**: Provides mechanical clearance and environmental isolation for active structures. - **Geometry Variables**: Cavity depth, footprint, pressure, and vent path determine final behavior. - **Integration Stage**: Implemented before final sealing and external interconnect completion. **Why Cavity formation Matters** - **Device Function**: Many MEMS elements require free movement that only cavities provide. - **Performance Tuning**: Cavity volume and pressure influence sensitivity and damping. - **Protection**: Enclosed space shields delicate structures from external contamination. - **Yield Impact**: Defect-free cavity formation is necessary for consistent functional output. - **Packaging Compatibility**: Cavity design must align with bonding and sealing process windows. **How It Is Used in Practice** - **Profile Control**: Use calibrated etch and mask design to hit cavity geometry targets. - **Contamination Management**: Maintain strict cleanliness to avoid trapped particles before sealing. - **Post-Form Metrology**: Inspect cavity depth, sidewalls, and structural clearance before bond. Cavity formation is **a defining structural step in cavity-based package design** - accurate cavity engineering directly drives MEMS performance and yield.