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.