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| Category | Source of failure | Testing issues | Observations |
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RF MEMS
Switches,
resonators,
lab-on-chip,
capacitor,
varactor,
sensors, and
filters.
| Stiction failure, surface contaminations, and accumulation of charges in the dielectric part. | A short occurred when two parts of the device stick to one another.
Major issue was because leftover charge in the dielectric causes increase in voltage required for the device actuation and signal transmission.
Other issues of catastrophic failure occurred due to constant increase in voltage that causes the dielectric breakdown.
Crack initiated due to high stress in the structure.
Breakage of structure due to impact with the substrate. | A challenge in RF MEMS testing was to analyze stiction failure nondestructively.
Tracing the genuine adhesion point without removal of any part or component was challenging.
Hillocks and high roughness of contact area created gap between contact surfaces.
Issues about contact area, geometry and the asperity in contact area were highlighted to understand RF MEMS [98–101]. |
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Optical MEMS
Sensor,
resonator, optical buffers, mirrors and filters | High surface roughness,
stiction, and accumulation of charges. | Roughness of micromirror surface, stiction due to the accumulation of charges that caused stuck in actuation.
Tracing faults of shorts and stiction beneath the mirror surface.
Cracks initiated during detachment of the micromirror while doing failure analysis under the mirror surface.
Structure breakage during handling. | Surface roughness of single mirror was determined feasibly and it takes time for analysis of various mirror locations.
The surface roughness analysis of arrays of mirrors was not reasonable using current AFM techniques.
Parallel test technique provided satisfactory results in determining surface roughness of entire array or collection of mirrors [102–104]. |
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Microfluidics
Lab-on-chip,
flow sensors,
micro channel,
and micro needles. | Fluid contamination, leakage,
no compatibility with MEMS,
short-circuit defect, and
catastrophic and parametric faults due to structural defects. | Device was flushed of fluid before analysis; this effort negotiated the failure mechanism and induce erroneous outcomes.
The common issues are fluid contamination, deprocessing, leak detection and compatibility with MEMS.
The fluid flowing under electrostatic domain was stuck due to opposite charged molecules causes channel blockage.
Channel with the rough walls caused a turbulent flow of fluid sample. | During typical analysis using SEM, the device was flushed of fluid before analysis.
High quality resolution was required for microfluidic systems during an analysis of pressure or flow sensor exclusive of flushing the device.
Therefore in verification of device functionality, purpose of using test fluid was helpful in tracing the movement of the fluid during operation. The approach of using diagnostic fluid also proved helpful to trace the breakage, leakage or cracks in the device [105–108].
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BioMEMS
Lab-on-chip,
biosensors. | Fluid contamination, leakage,
blockage of channel,
cracks,
and material compatibility. | Analogous tribulations with the existence of additional biological materials was experienced during testing.
In the analysis of DNA purification, the surface area of channel was limited. Sample clogging occurs in the channel during testing [109–111]. | Challenges of functional testing were device deprocessing and biocompatibility. |
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