Accurate measurements of MEMS geometries and motions are crucial to achieving the desired performance of the devices. The wide variety of MEMS devices in development and production requires very flexible metrology for single-platform characterization.In addition to having greatly varying geometries, devices must also be characterized statically and under actuation.White-light interferometry, fortunately, is a technique flexible enough to meet most MEMS measurement needs. This high-speed, noncontact measurement method allows both large lateral and vertical ranges with nanometerlevel vertical resolution and position accuracy. When standard illumination is replaced with strobed light, dynamic measurements of MEMS can also be carried out.This paper presents some of the hardware and software design considerations for producing a single metrology platform with the required flexibility for production MEMS metrology. Several static and dynamic MEMS measurements are presented to illustrate the design requirements.
Optical profiling (white light interferometry) has proven successful for measuring surface features of unpackaged MEMS devices. Most devices, however, perform differently once encased in their final packaging, which may include vacuum, elevated temperature or other special environments. This paper describes a novel interferometric surface profiling technique for high magnification measurement of devices through transparent packaging or environmental chambers. Three techniques are introduced into a long working distance interferometric objective: aberration correction, shaped illumination, and dispersive compensation. Data demonstrates that measurement results through the protective media are comparable to those of a standard objective measuring an unpackaged device.
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