Through-wafer interrogation of MEMS device motion

Dawson, Jeremy

doi:10.33915/etd.967

Cited by 2 publications

(4 citation statements)

References 29 publications

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“…These benefits include added dimensionality, high bandwidth, and complex packaging [35]. MEMS optical monitoring schemes using bulk optical counter parts of integrated optical components such as waveguides and free-space optical interconnects have been shown, in preliminary testing, to provide an adequate means of optically monitoring MEMS device motion [36], [37]. While promising improved performance, the integrated optical monitoring elements must be compatible with current MEMS and other chip-level device and packaging technologies to minimize system complexity and costs.…”

Section: Integrated Optical Monitoring and Control Explorationmentioning

confidence: 99%

Integrated through -wafer optical monitoring of MEMS for closed -loop control

Dawson¹

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Current trends in many microelectronic systems show an increased use of microelectromechanical systems (MEMS) to perform a variety of tasks. The increased market for MEMS has led to microsystem technologies being employed in physically demanding environments and safety critical applications. This creates the need for higher degrees of certainty in MEMS operation, especially in systems that contain drive components operating under time varying load conditions. Situations such as these give rise to the need for detailed knowledge of the operational states of MEMS over the lifetime of the device, as well as device fault detection. Accurately obtaining this information by a means decoupled from the system shows the potential to further enable both complex and simple MEMS, and allows for the application of closed-loop control. Preliminary through-wafer optical monitoring research efforts have shown that through-wafer optical probing is suitable for characterizing and measuring the behavior of lateral harmonic oscillators. This presentation will discuss research undertaken to establish integrated optical monitoring (IOM) for closed-loop control. Design of the optical microprobe setup, as well as device geometry, were completed to achieve a through-wafer optical signal with increased positional resolution and mechanical stability. Successful linear closed-loop control results achieved using the redesigned probe setup and devices will be presented. Increased displacement information in the optical output waveform is needed for the successful application of more robust, nonlinear control routines. Theoretical optical output field intensity studies are presented and compared with experimental output waveforms, showing a positional resolution of 2 µm using grating structures. Initial binary Fresnel diffractive optical microelement design layout, fabrication parameters, and testing results will be given as well for implementation of a fully integrated optical monitoring system.

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Section: Integrated Optical Monitoring and Control Explorationmentioning

confidence: 99%

Integrated through -wafer optical monitoring of MEMS for closed -loop control

Dawson¹

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“…Previous work [1,2,3] in our group has dealt with MEMS devices, particularly lateral comb resonators. These devices are 300um long, 100um wide, and oscillate laterally when excited with an alternating current.…”

Section: Prior Mems Workmentioning

confidence: 99%

“…The inner fingers move side to side because of the voltage difference produced by the AC current on the outer fingers. Current and previous work within our group is concentrated on control, fault detection, and integrated optical monitoring of these MEMS devices [1,2,3]. All of those efforts were intended to increase reliability and robustness of theses systems.…”

Section: Prior Mems Workmentioning

confidence: 99%

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Characterization of diffractive optical lenses for use in MEMS integrated optical monitoring

Hollandsworth¹

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Mechanical Machines (MEMS) are finding use in an increasing number of applications. Many of these applications, especially safety critical ones, require continuous knowledge of the operational status of the MEMS device over its lifetime. In-situ monitoring of the operational status of these devices is better suited to optical methods which provide a non-invasive way of continuously determining device position as a function of time. This data is central to determining the MEMS state and operational condition. Whether the optical source is internal to the MEMS package or external to the package and introduced via optical fiber, lenses will be required within the package to focus the MEMS optical probe beam to and from the test device. The need for hybrid co-integration with the MEMS die within its package results in physical dimension and focal length constraints on the lenses used and points toward the applicability of diffractive optical lenses to realize the goal of MEMS insitu integrated optical monitoring. The spot diameter must be of a width comparable to any lateral displacement that must be measured so that acceptable resolution of the motion can be observed. Diffractive lenses are capable of meeting all of these requirements. Previous work designed and fabricated Fresnel binary phase diffractive lenses in borofloat glass substrates as a means to achieve the required lens function for either a visible (632 nm wavelength) or near IR (1310 nm) probe beam. This work undertakes the full optical characterization of these previously fabricated lenses, compares their performance (spot size, focal length, efficiency) to that expected from theory, and determines if they meet the original lens design criteria, These results enable an initial assessment of these lenses for use in MEMS in-situ lifetime optical monitoring.

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Through-wafer interrogation of MEMS device motion

Cited by 2 publications

References 29 publications

Integrated through -wafer optical monitoring of MEMS for closed -loop control

Integrated through -wafer optical monitoring of MEMS for closed -loop control

Characterization of diffractive optical lenses for use in MEMS integrated optical monitoring

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