Choosing a MEMS Foundry

By Karen Lightman, managing director, MEMS Industry Group

While micro-electromechanical systems (MEMS) industry leaders such as STMicroelectronics, Texas Instruments, Hewlett Packard, Robert Bosch and Kionix rely on their captive fabs to meet volume production, the movement toward fabless and fab-lite models continues to gain ground. InvenSense, for example, has always been a fabless company, and even powerhouse Analog Devices uses a hybrid approach, choosing internal and external foundries to produce MEMS die for inertial sensor products. Despite the advantages of having a captive fab, which supporters say includes greater control over both capacity and intellectual property (IP), the primary disadvantage—cost—has spurred the use of third-party foundries.

In addition to cost savings, companies work with third-party MEMS foundries for a variety of reasons. They may want to prove a design, prototype a design that is already proven, or mass-produce a MEMS device. With a multitude of options, choosing a MEMS foundry is not a simple decision.

Pure-play MEMS foundries, such as Silex Microsystems, Micralyne, Teledyne DALSA, Asia Pacific Microsystems, Innovative Micro Technology (IMT) and Tronics do not offer design services but they do offer volume production. Partially captive foundries offer another alternative. They will fabricate MEMS die for outside customers when there is excess fab capacity.

Companies such as A.M. Fitzgerald & Associates, Nanoshift and SVTC specialize in design and rapid prototyping, and also consult with their clients to find the perfect foundry partner. Dr. Carolyn White of A.M. Fitzgerald & Associates, who specializes in design, analysis and fabrication for her firm, explains why foundry selection is so critical in the MEMS industry: “In the IC world, you can potentially have a device ready to ship to customers in 18 months—but not in the MEMS world. Even with an existing prototype (with a proven process flow), it takes time to choose a foundry partner and bring the process flow into production. Foundries first do an initial prototype run, then move to pilot production and finally go to full-volume production. That takes at least a year and a half. Total time to market can be five years and could cost in the range of US$10 million for a new device using the fabless model.”

White says that a foundry partner with the right experience can help companies to overcome common technical and logistical challenges—such as coupled physics, moving parts, environmental exposure, and test and packaging challenges. MEMS also presents design challenges that foundries cannot meet alone, according to White. With few formal standards, diverse tool sets and foundry-specific design rules not yet available for existing simulation packages, companies need good design and process engineers to work with the foundry throughout the process.

One Size Does Not Fit All

Rob O’Reilly, senior staff engineer at Analog Devices (ADI), explains the company’s hybrid approach to manufacturing MEMS devices: “We do ‘smart partitioning manufacturing’ at ADI. We make monolithic designs—which comprise about 75% of what we ship into automotive. We also make package-level multi-chip designs. For one of our first big consumer wins, we needed high quality, high volume and quick turnaround so we decided to take the sensor away from the ASIC. We met with TSMC and developed a secure line on a 6″ flow that is exclusive to ADI. We finish the devices with ‘the special sauce.’”

O’Reilly admits that “one size does not fit all,” explaining that the “automotive industry is not ready for fabless or fab-lite.” Thus, ADI uses its own captive fab for its automotive MEMS products.

ADI’s hybrid approach to MEMS manufacturing may give them the best of both worlds. They can work with pure-play foundries for high-volume products, and they can rely on their own fab for the automotive market—with its strict quality-compliance requirements and longer design-to-delivery timelines.

Launching your Search for a MEMS Foundry Mate

Because choosing the right foundry relationship is one of the most important decisions for a MEMS company, MEMS Industry Group (MIG), the trade association advancing MEMS across global markets, spearheaded (with our member companies) the development of a “MEMS Foundry Engagement Guide”, a step-by-step wiki-guide for companies looking for MEMS foundry services.

MIG also created MEMS Marketplace, an online public portal that helps companies to search for potential business partners, including foundries. MEMS Marketplace lists companies by category and includes company-specific descriptions and contact information. These tools in tandem help to simplify the process of approaching foundries with both informal questions and formal requests for proposal.

Before beginning to search for a MEMS foundry partner, it is important to understand the fundamentals, including the differences between traditional IC manufacturing and MEMS manufacturing. The main distinguishing factor is that MEMS foundries tend to specialize in a certain application field. MEMS technology, by definition, covers an array of micro-devices across a broad spectrum of applications. Because the manufacturing processes, though built on the same basic materials and tool sets as ICs, vary so widely from application to application, no single foundry can be expected to have expertise and be efficient in producing volumes at a low cost without specialization. Understanding this can help to narrow the field of potential candidates without even having to pick up the phone.

The next requirement is to complete a self-evaluation checklist to determine your level of readiness for working with a foundry partner. Consider application and market projections, package type and integration requirements, cost targets, volume projections, risk evaluation, product life cycle assessment, design and fabrication considerations, and process flow.

Foundry Selection

Once you determine that your product is ready for fabrication, it is time to contact potential foundry partners. Understand that there is certain information that you should be willing to share with a foundry upfront, including product maturity level. On the flipside, you should be prepared to ask questions. Questions that you should ask a foundry include: the location of the fab, methods to protect IP, the cost of a prototype run (excluding wafers & masks), cost to develop the product (including per-wafer cost.) Other important questions should focus on design kits/design support, CMOS compatibility, fab transfer process, development flexibility, and the financial security/profitability of the fab.

At the same time that you are deciding whether a foundry is a good fit for you, the foundry is looking at you just as critically. Foundries do not just look for customers that will turn a profit in the short term. They consider many factors in customer selection. Foundries consider a potential customer’s expertise in MEMS, similarities in business culture, the market potential for the manufactured product, the maturity level of the product (and the customer’s understanding of this), the match of customer needs and fab capabilities, IP ownership expectations, and the desire to build a long-term relationship.

Making the Right Choice

Once you have found your match, remember that good communication is essential. Create a schedule for face-to-face meetings and conference calls, and use email to address other issues as they arise. When the information flows between your company and your foundry partner, your manufacturing process will keep flowing, too.

Craig Trautman, vice president, business development at IMT, states that the collaboration between a MEMS company and foundry must be a close one. “As a foundry, we have some customers ‘living’ at IMT. We give them free office space because a lot of things that we do are really hard. Our customers need to collaborate with us, sometimes in a very hands-on way, to make it all work.”

When asked how foundries can assure customers working on site that their IP is well protected, Trautman says, “Our goal is to be Switzerland, and if we’re not Switzerland, our business model fails.” Thus, protecting a customer’s IP is critically important to making the relationship successful—for both parties.

Through MIG’s Foundry Engagement Guide, device manufacturers and foundries can find their MEMS “soul mates” and achieve long-term success. To read the complete guide and learn how to improve your foundry relationship, visit www.memsindustrygroup.org/foundryguide.

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