When a MEMS device fails, it's removed from the enclosure and a cross-sectional view is taken of it by a focused ion beam. This cross section is then observed by the microscope, allowing the test operator to draw conclusions about how, when, and where failures occur.
Reliability testing is one more big problem. Just how do you define long-term reliability for MEMS devices? It's apparent that VHDL/analog simulators are needed as well. Furthermore, process tools must be faster and more capable of deeper etching. Cost modeling, which is generally not included in simulators, is important to manufacturing engineers and, therefore, should be included.
There's no standard platform for integrating MEMS structures with other IC processes, particularly CMOS. Unlike conventional CMOS ICs, MEMS devices scale differently with respect to dimensions and voltages. While the frontend of a MEMS process may be similar to that of a conventional IC, it differs at the backend (Fig. 6).
Moving mechanical MEMS structures must be handled differently during a process flow. Special sectioning, probing, and handling procedures are needed to protect these parts, some of which might be sealed later, and some which must remain exposed to interact with the environment they serve.
From all of these challenges, the term "seamless microsystem engineering" has risen. This is a foundry strategy based on the cluster integration of several stages in the production cycle. Seamless microsystem engineering is said to allow a strategic alliance to form between multidisciplinary partners. Eventually, it leads to a shorter concept-to-production cycle, and minimizes costs. In fact, several MEMS companies, specifically many European companies, have implemented, or are in the process of implementing the seamless microsystem engineering concept.
Aside from the well-known technical barriers to MEMS/MST commercialization, many MEMS experts with more business acumen have pointed out a certain salient fact that tends to hinder commercialization. These experts acknowledge that embracing MEMS for the sake of technology can be a big stumbling block. Customers really don't care how a device is made, or by what technology it's produced, as long as it solves a particular problem for them.
Fascinating is the technology that makes possible lilliputian structures like microgears to arm an atomic bomb, microrobots able to clear out clogged human arteries, complete DNA analysis systems on one tiny chip, and miniscule micromotors that can drive other miniscule structures such as microcars. It's understandable that this technology can fire up an engineer's imagination to no end. But, that facet is quickly disappearing in the face of the market pressures that place more of an onus on MEMS /MST designers to arrive at the right solutions to critical problems.
Of course, MEMS/MST technology has inherent performance, small-size, reliability, low-weight, and low-cost advantages. In that respect it can be the right answer for many applications. That's what has been driving the MEMS market for some time. This is particularly true in an era where smaller, lighter, less-power-hungry, and cheaper electronics are the call to arms (see "A Low-Cost Investment Road Beckons," p. 92).
In their efforts to reach larger commercial markets, these are the lessons that many MEMS companies have learned the hard way. If the present trends of technology maturation continue, MEMS and MST devices will become even more common, and the next age beyond of nanoelectronics using carbon fibers, nanotubes, etc., might not be too far off on the horizon.