A Review on Key Issues and Challenges in Devices Level MEMS Testing

Table 2

Summary of failures, their causes, and procurement for various MEMS devices.

Group	Causes of failures	Reliability test
Group 1
Chemical sensor; nozzles; microfluidic; DNA sequencers	Dielectric breakdown	The reliability test of flagellar microfluidic motors was performed in environmental conditions. Probabilistic mathematical model was used to analyze the rotational behavior. The decay time of 55 h was predicted for the bacterial motor [35].
Group 1 or Group 2
Accelerometers	Fracture, fatigue, mechanical wear, charging, and change in friction	(1) Accelerated life time of devices was tested experimentally for 1000 hours at about 145°C to 200° C [36].; (2) Tytron 250 was used to test fatigue. The experiment showed fatigue life between 7.78 × 10^4 and 1.48 × 10^7 cycles when the stresses increased from 2.05 to 2.83 GPa [37].; (3) Sandia National Laboratories developed the SHiMMeR (Sandia High Volume Measurement of Micro Machine Reliability) that can simultaneously control and test up to 256 MEMS parts [38].; (4) Fatigue and creep were observed by using X-rays diffraction. Wear was analyzed through DLC coating (Diamond Like Carbon), stiction was observed by using MIL-STD-883F (Military Test Standard Device) and SAM (Scanning Acoustic Microscope) was used for contamination [39].
Group 2
Pressure Sensors	Vibrations, shock Fatigue, fracture, and change in friction	The fatigue was detected in the fabricated sensors operating below the stress level; it is observed that fatigue can occur at equal stress and fracture levels [40].
Gyroscopes	Vibrations, shock, and charging	(1) The reliability assessment of a three-axis gyroscope was performed under several shock loading conditions [41].; (2) The temperature degradation and variations in signal to noise ratio were also reported [42].
Group 3
Thermal actuators	Vibration, shock, and mechanical wear	(1) Weibull statistics was used to analyze the fracture tests on the beam by applying different loads.; (2) Experimental technique was proposed for micro switches to observe malfunctioning due to charging and creep [43, 44].; (3) The effects of pull-in voltages were observed during bending and torsional modes of beams. Mechanical wear and fatigue tests were performed to predict the life time [45].
Micro relays	Fatigue, fracture, mechanical wear, shock, vibrations, and charging	Effects of stiction and welding failure were performed at 10^9 on/off switching cycles [46, 47].
Group 4
Electrostatic actuators	Charge in friction, fatigue, fracture, mechanical wear, shock, and vibrations	Stochastic method was used to analyze the pull-in and pull-out voltages for prediction of device life time [48, 49].
Mirror devices	Optical degradation, fatigue, fracture, mechanical wear, shock, and vibrations	Texas Instruments (TI) developed the optical inspection tool for DMD devices that examines each pixel of the DMD array [50].
Gear devices	Charge in friction, fatigue, fracture, mechanical wear, shock, and vibrations	Sliding surfaces were analyzed through simulations to prevent adhesion and wear [51].