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.