MEMS Technology has become more ubiquitous in recent years but still metrology for MEMS materials has lagged in
terms of standardization and common industry usage. MEMS metrology encompasses a very wide range of test methods
for various kinds of functional and manufacturing characteristics of these devices but in this article we only refer to test
techniques for extraction of mechanical properties essential to the product development process and process monitoring.
These include methods such as test structures and other methods for measuring elastic modulus, Poisson's ratio,
residual stress and stress gradients, and CTE, etc. as well as properties important to device reliability such as creep,
fatigue and wear.
Metrology for MEMS materials has always included attempts by researchers and engineers to miniaturize existing
macro level test methods like the uniaxial tensile test, hardness test, bulge test etc. but historically another approach has
always existed in parallel. Novel on-wafer or on-chip test structures are continuously being developed in an attempt to
achieve stream-lined in-line tests that don't require the "destructive" nature of the former group of test methods. The
vision is that in-line methods would eventually be standardized to the point where they, in the mask layout phase, could
be "dropped onto" wafer as in-line process control monitors (PCMs). Today, we're still far away from realizing this
ideal situation in the sense that the ASTM standards list does not include a single unique test structure for material
property extraction. The focus of this current article is to critically compare the various techniques that have been
developed so far and contrast their viability and potential as candidates for standardization either in-line or off-line.
Designing manufacturable MEMS devices requires a strong link between design and process engineers. Establishing systematic design principles through a common CAD framework facilitates this. A methodology for MEMS Design for Manufacturing (DFM) is presented that focuses on solid process and design qualification through systematic parametric modeling and testing, from initial development of specifications to volume manufacturing. This strategy has been applied to two MEMS fabrication processes, including CMOS-compatible SOI micromachining and metal-nitride surface micromachining. Case studies of designed, simulated, fabricated and characterized test structures demonstrate the methodology and benefits of the outlined DFM approach - including extraction of material properties and process capabilities enabling a prediction of fabricated device performance distribution. The overall result is a MEMS product design framework that incorporates a top-down design methodology with parametric re-usable libraries of MEMS, IC and relevant system components capable of allowing to design within a specific process (via a process design kit) to enable virtual manufacturing.
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