Sacrificial Layer

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.