Design Of MEMS Microbridge And Parameter Optimization Of Photolithography

Uncooled infrared detectors were firstly raised and designed in 1980 s. Due to the advantages of low cost, high reliability, easy integration, working on room temperature, and well compatibility, it has been widely applied in military and civilian detections. The chips of uncooled infrared array detector were composed of readout circuit, sensitive material and micro-bridge structure with the working principle of radiation-to-heat and heat-to-electrical conversion. The micro-bridge structure fabricated by MEMS technology can effectively reduce the thermal conductivity, thus the unit of detector obtained a high sensitivity under room temperature. Therefore, conducting the researches on micro-bridge structure with low thermal conductivity has significant importance in theoretical analysis and practical application. Each pattern of micro-bridge structure in different plane was fabricated by the photolithography technology, which play an important role in the fabrication of critical unit width and size. Consequently, optimizing the condition of photolithography technology is the fundamental of high-performance infrared detector integrating with micro-bridge structures.This paper is focus on the design and deposition of VOx-based uncooled infrared detector, and optimizing the photolithography technology to apply on the detector fabrication. The main researches have been presented as following.(1) Analysis the working principle of micro-bolometer, the structural characteristics of micro-bridge, the thermal and mechanical properties. Using software Intelli Suite to simulate and analysis the mechanical and thermal properties on micro-bridge structure. The simulation results exhibited that the unit size at25*25μm2 and the width of bridge leg at 0.9 μm has the best performance.(2) Fabricate the micro-bridge structure, and compare the mechanical stability between simulation and experimental results. The results suggest that using the double L-shape of cantilever has a better mechanical stability than traditional L-shape cantilever.(3) Optimize the process for micro-bridge fabrication and improve the parameter of photolithograph technology, which contained two solutions. First, according to surface morphology of metal thin film, selects different align method to advance the alignment precise. The other is changing the spraying procedure in photolithography to avoid lateral etching.This paper desires to seek suitable preparation condition for well-performance micro-bridge, including photolithograph, etching, CVD, PECVD and etc. In our experiment, we used software L-edit to design the graph of each mask, and then fabricated the 320×340 focal plane array in ultra-clean environment. Additionally, 10 types of micro-bridge units have been researched like different unit sizes or different widths of bridge-leg. At last, we simulated the thermal and mechanical properties of micro-bridge by using FDTD solutions, and prepared a FPA detector with micro-bridge structure, which presented great stable thermal, optical and mechanical properties.