Sacrificial layer is the temporary material layer in MEMS fabrication that is removed later to free movable structures - it defines air gaps and mechanical clearance in surface-micromachined devices.
What Is Sacrificial layer?
- Definition: Process layer intentionally deposited for later selective removal.
- Function: Sets spacing between structural films and creates release cavities.
- Material Options: Common choices include oxides, polymers, or metals with selective etchants.
- Integration Rule: Must be removable without damaging structural or anchor materials.
Why Sacrificial layer Matters
- Geometry Definition: Gap height and motion range depend on sacrificial thickness control.
- Release Success: Incomplete removal causes stuck or non-functional MEMS parts.
- Selectivity Criticality: Poor selectivity can undercut anchors or thin structural layers.
- Yield Sensitivity: Sacrificial residue and byproducts are frequent failure sources.
- Device Performance: Mechanical response and capacitance often depend on final gap accuracy.
How It Is Used in Practice
- Material Pairing: Choose sacrificial and structural stacks with proven selective etch windows.
- Access Design: Place release holes to ensure full etchant penetration and byproduct removal.
- Post-Release Clean: Use controlled rinsing and drying to avoid residue and stiction.
Sacrificial layer is a core temporary layer concept in MEMS process architecture - sacrificial-layer control directly governs release yield and device functionality.