Microstructure Fracture Prediction Services

Micro-mirror fracture example
  • Having trouble with yield or field losses?
  • Are parts breaking during processing?
  • Need to match reliability to customer requirements?
  • Upgrading an existing microstructure design?

AMFitzgerald's microstructure failure and load limit prediction services are based on our patented algorithms and methods.

Failures of crystalline microstructures occur at surfaces. The surfaces are weaker than the bulk crystalline material due to microscopic imperfections that are caused by manufacturing processes. Details such as etch tool type and operating parameters are very important.

The quality of etched surfaces, for example, depends strongly on etch process details. Different process parameters can lead to significant differences in surface strength and device fracture probability.

Surface properties of silicon etched by different processes vary greatly and have a significant effect on fracture strength

We quantify the effect that a manufacturing process has on surface strength using test structures. This yields information that is specific to a particular process run on a particular tool. However, our protocol is designed so that we never need to know our customers’ proprietary process details.

Test structures etched by different processes exhibit a wide range of fracture strengths

Relying on our deep experience with finite-element numerical simulation, we model stresses in devices under load. Load limits and failure points are then predicted by our algorithm, which combines simulation results with data on surface strength obtained from test structures.

Sample output: Probability of failure versus applied force for a silicon micro-mirror. The prediction was verified by breaking actual micro-mirrors. The predicted characteristic strengths are within 7% and 12% of experimentally measured values for torsion and tensile loads, respectively.

How We Predict Failure

First, a statistical characterization of the influence of a manufacturing process on surface strength is obtained from test structures. This information is applicable to any device made by the same process.

Failure prediction flow chart

Next, a finite-element model of a proposed or existing microstructure is created in ANSYS. Stresses in the microstructure device under an applied load are simulated. Many different load scenarios may be tested in the simulation.

Finally, the results of load simulation are combined with surface strength information to predict failure points and load limits. With this information, one may revise the device design or process, or proceed to manufacturing.

Contact us at (650) 347-MEMS or info@amfitzgerald.com for an initial consultation.