Design,Fabrication And Impact-resistance Study Of Uncooled Infrared Focal Plane Array Based On ?-Si

Uncooled infrared focal plane array has the advantages of low cost,low power consumption and no refrigeration equipment,which has been widely used in military and civil field.The paper takes amorphous silicon uncooled infrared focal plane array as the research object,developing the electrical properties study of amorphous silicon sensitive film,the optimal design of pixel structure from optical,thermal and mechanical aspects,and the preparation experiment.Firstly,the influence of process parameters on electrical properties of amorphous silicon thin films was studied.The paper prepared the amorphous silicon films with different germanium content by plasma enhanced chemical vapor deposition?PECVD?.According to electrical test,the temperature coefficient?TCR?and resistivity of thin film samples were measured.The results showed that the TCR and resistivity of the thin film decreased with the increase of the reaction gas flow rate?GeH₄/SiH₄?.And high germanium doping would cause the amorphous silicon film cracked after the metal stripped off process.The paper finally determined the deposition parameters of amorphous silicon thin films with high quality,high TCR?-3.5%/K?and moderate conductivity(1.47×10^-3??cm?^-1).Secondly,the optical and thermal design of array pixel structure was discussed.Based on admittance matrix method,the absorption rate model of pixel infrared resonator was established.Also,numerical simulation was used to optimize the thickness of resonator film system.The average infrared absorption rate of the membrane system structure could reach 93%during 8-14mm.Theoretical calculation and simulation analysis were carried out for the thermal parameters of different configuration pixels,and the thickness of the film system of the bridge arm was optimized by taking the thermal deformation of the pixels as the main index.The influence of dc bias and pulse bias on pixel performance was analyzed based on the thermoelectric coupling simulation results.Thirdly,the mechanical property and impact resistance of focal plane array pixels are studied.Through nano-indentation test,the influences of silicon nitride deposition parameters?difference of frequency time ratio?,annealing temperature and photolithography process on elastic modulus and hardness of silicon nitride thin films were studied.The analytical solutions for the deformation of the U-type micro-bridge structure with the same temperature rise and the deformation of bridge arm which had gradient distribution of the temperature are derived.The solutions were also verified by simulation.The impact resistance characteristics of the pixels are simulated by applying the impact loads vertically and horizontally.At the same time,based on the impact sensitivity analysis of the pixels,the critical dimensions of the length and width of the bridge arm structure are optimized.Finally,combining the optimal design results,the uncooled infrared focal plane array was prepared and tested.The preparation process design and layout design were carried out.During the process of tapping out,the key processes,including lift-off process and electrode column hole etching process,were designed and improved,and the morphology of the key process steps was characterized.After the completion of tapping out,the thermal response time parameters were determined through the thermal response test.The thermal response time of the dual-?-type pixel was 4.03ms and that of the U-type pixel was 14.80ms.