| Micro-bolometer has given many new opportunities in the field of civilian andmilitary applications due to its low power consumption, light weight, low cost andeasily mass production. Taking the micro-bolometers based on amorphous silicon thinfilms as our main objects, this thesis systematically analyzed the basic mechanics anddynamics of micro-bridges, and analyzed the origin of gas in package cavity and thevibration effect of thin gas film in the cavity using FEM. Finially, a few vibration andimpact tests followed a standard of device-level reliability were carried out to verify thethe results of early simulation.The micro-bridges in bolometers have high resonance frequency and the maximumdisplacement occurs on the center of the micro-bridges, and the legs are easy to bend.The micro-bolometer with Y style legs has better structural reliability than that of I styleand L style legs.The leg length has great effects on modal shape of the bolometers. Thefirst tensile stress and the first compressive stress of L style legs in micro-bolometersare0.55MPa and0.18MPa, respectively. The bolometer structure is more stable in thestate of tensile stress than in compress stress. So we should adjust the farbricationtechnology and the structural parameters to make the amorphous silicon thin films in thestate of tensile stress and prevent the stress value from exceeding the bending limits.Low frequency vibration has almost no influence on the micro-bolometers. Thecenter of bridges has the maximum displacement and the stress focuses on the corner ofbridges or between the bridge and leg. The maximum displacement is as high as0.68μm，which is beyond the half of the cavity depth. At this point, the micro-bridge iseasy to adhere onto the substrate, making the structure out of work. When the randomvibration is set at2(m/s~2)~2/Hz, a maximum structural displacemen on the center of themicro-bolometer is found, and the stress focus on the the inner side of the cornerbetween legs and stuns. When a peak acceleration impact is set at500g, a delay about0.2ms happens. The maximum stresses in X, Y and Z directions are0.28MPa,0.42MPa,and0.56MPa, respectively. It is found that the bridge structure is not stable when thestress in Z direction is beyond the bending limit. Vacuum degree in package cavity has a great influence on the vibrationcharacteristics of the micro-bolometers. The main factors that matter include materialreleasing and failure of shell bound in packaging. The generated thin film gases willmake the structure more unstable when vibration occurs, and the higher the pressure ofthe gas, the bigger the press in the micro-bolometers is.The observation by SEM reveals that the structure of the micro-bolometers keepsintegrity after a random vibration test on several final devices at2(m/s~2)~2/Hz. When apeak acceleration impact is set at1000g, several places of micro-bridge collapse andlegs bending are easily found in the specimens. The cell failure in the ofmicro-bolometers after peak acceleration impact at the direction of X, Y and Z, is5.6%,6.1%and18.7%respectively. It is also found that the abruption focuses on the cornerbetween stuns and legs, or on the corner between legs and center of the bolometers. Thecollapsed bridges overlap each other in the inner of the device, making even morefailure in the bolometers. The real observation on the effect of vibration in the devicesmatches well with the computer simulation. Both the results of simulations and theresults of device vibration tests reveal that the experimental detecters have a greatdynamic stability and would meet the reliability requirement of microelectronic devicesat2(m/s~2~)2/Hz random vibriation and at500g peak acceleration. |
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