Strength Prediction for MEMS Components  
   
MEMS Component support mechanical load in a micro interlocking system of a Mesoscale Actuator Device Types of Microridges:

1. U-groove: etched by 30% KOH

2. V-groove: etched by 45% KOH

3. Trapezoid: etched by 30% KOH

4. Round-groove: etched by DeepRIE
Strength Prediction for MEMS Components

 
   
Motivation  

I. Importance of Strength Prediction for MEMS:
  • Notches and sharp corners often appear as a result of MEMS fabrication.
  • Difficulty to compare basic material property to component test.
  • Influence of fabrication process on component strength (i.e. influence on surface texture) not known

II. Expand Proposed Criteria to Other Materials (Need Verification):
  • Aluminum (Al2O3), high Young’s Modulus
  • Zirconia (ZrO2, stabilized by Y2O3), high Fracture Toughness
 
Concept

Use Converged Stress to identify the location where stress concentrations will be compared.

Strain Energy calculated at critical radius: to predict failure loads.
SEM picture for U-groove ridges

SEM picture for U-groove ridges

 Failure of microridges in device caused by large loads (400 N)

Failure of microridges in device caused by large loads (400 N)
Finite element model
 
Results for Silicon
Predicted strength for different geometric shapes
Results for Silicon
 
Results for Different Materials

SCS: Single Crystal Silicon

Al: Alumina (Al2O3), High Young’s Modulus

Zr: Zicronia (ZrO2+Y2O3), High Fracture Toughness
U-groove Round-groove
Estimated Strength of U-groove Estimated Strength of Round-groove
 
Conclusions

Fabrication processes strongly influence strength based on different micro-features (geometry) produced.

The developed strength calculations provide good correlation with experiments.

MEMS component strength can be predicted with limited experimental data.

Optimal strength prediction occurs for a critical height of ridges.

Strength can be significantly increased if other materials used.