Stiction

Stiction is the adhesion-related sticking of released MEMS structures to nearby surfaces due to capillary, van der Waals, or electrostatic forces - it is a major yield and reliability failure mode in MEMS.

What Is Stiction?

• Definition: Unintended contact and adhesion that prevents intended mechanical motion.
• Typical Triggers: Capillary forces during drying, roughness interaction, and insufficient restoring force.
• Failure Timing: Can occur during release drying, packaging, or field operation.
• Device Impact: Leads to stuck beams, shifted resonance, or permanent performance loss.

Why Stiction Matters

• Yield Loss: Stiction can render otherwise correctly fabricated devices non-functional.
• Reliability Risk: Intermittent sticking causes drift and unpredictable behavior in service.
• Process Sensitivity: Minor changes in drying or surface chemistry can trigger failures.
• Design Constraint: Mechanical geometry must provide sufficient restoring force margins.
• Packaging Coupling: Humidity and contamination during assembly can worsen stiction effects.

How It Is Used in Practice

• Surface Engineering: Apply anti-stiction coatings and control roughness at contact interfaces.
• Drying Strategy: Use critical-point or supercritical drying to avoid meniscus forces.
• Design Safeguards: Increase gap, add dimples, and tune spring constants for release robustness.

Stiction is a primary mechanical-yield challenge in MEMS manufacturing - stiction prevention requires coordinated process, design, and packaging controls.