For MEMS companies, finding and establishing a partnership with a full-service MEMS foundry is critical to successful device development and to reaching high-volume production. The selection process must include foundries that have the capability to provide services for prototyping, process development, and high-volume manufacturing. It is also important to select a foundry that can offer intelligent design feedback or cooperate on designing the device itself to ensure manufacturability. To be successful, the partnering foundry must meet all these needs and be flexible in the application of its capabilities and services.
Many complex MEMS devices do not fit simple rules of fabrication and varied materials are often required for making these MEMS work. Companies need a foundry partner that can invent outside fixed design rules and is not hindered by materials limitations. The foundry partner should allow use of non-CMOS materials, including various metals and other materials (e.g., Au, Ni, Ru, In, Pt, Cr, Co, Mo, AlO2, TiO2, Ta2O3, polymers, etc.) to solve and circumvent design issues.

click the image to enlarge Figure 1: Simulation of liquid flow for microfluidics application. Simulations like this are used for studying the flow rate, turbulence, friction, and other events that a MEMS device would experience, thus helping to predict/ determine device performance and reliability.

Additionally, superior processing tools and metrology capabilities add to the probability of successful manufacturing for complex MEMS.
For example, sub-micron photolithography may be necessary for making fine-scale featuresand even
if the MEMS device’s feature sizes require only low-resolution contact lithography, the device can benefit substantially from the finer lateral and vertical dimensional controls offered by higher resolution photolithography tools (e.g., 5X i-line stepper). Tighter dimensional controls can provide devices with better performance and with higher reliability over time.
High-volume production manufacturing in a foundry is very different from prototyping in an R&D facility. Designs with manufacturability in mind have a vastly superior opportunity for success relative to designs that are intended simply to demonstrate feasibility or performance of one or a few devices. The design must be conceived with the requirement that it meet well-thought-out tolerances that are achievable in volume production. A full service foundry can offer its experience in product design to overcome this particular hurdle. The foundry with extensive modeling capability and Monte Carlo simulations (Fig. 1) for multiple iteration variables has a much better chance for meeting its customers’ requirements for manufacturability.

click the image to enlarge Fig. 2: Process capability demonstration across 110 sample points of 2 micron diameter etched holes. The top chart shows the process distribution with average and standard deviation well within specifications. The bottom chart shows box and whisker plot for the wafers.

The importance of selecting a foundry with experience in manufacturing controls for high-volume production cannot be over-emphasized. These include metro-logy and test for process optimization, and statistical quality and process control (SQC, SPC) for predictability in manufacturing and product performance (Fig. 2). Once the design is locked down, the foundry must have a process control plan, various gage and process control charts with appropriate reaction plans for out-of-control conditions, and a well-defined implementation methodology. It also must be able to forecast wafer and die yield, as well as process capability. And finally, be sure to select a foundry from the outset that can handle your production volumes product transfers from foundry to foundry are notoriously difficult and should be avoided if at all possible.
Innovative Micro Technology (IMT) offers all these services at its Santa Barbara, CA location, with what we believe is the world’s largest and best equipped independent MEMS fab (30,000 sq ft of active work area). IMT’s overriding goal is to partner with companies to develop and manufacturer products based on MEMS technology.

Monteith G. Heaton
VP, Marketing and Sales
Innovative Micro Technology (IMT)
monte@imtmems.com