Design And Performance Test Research Of Small Size Micro-bridge Structure Detection Unit

With the continuous advancement of semiconductor manufacturing processes and the improvement of application requirements,the technology of uncooled infrared focal plane arrays(UIRFPA)had developed toward intelligence,high performance,and low cost.UIRFPA had widely used in the military and civilian fields for the advantages of low cost,low power consumption,light weight and small size.Compared with its fabrication technology,the development of computer-aided design technology for uncooled infrared focal plane detectors was relatively lagging.In particular,there was not a tightly link between the design of the microbolometer and its unit test.Then such simulation method cannot be corrected or updated in time according to the relevant device test,which resulted in the lower accuracy and reliability of the design.In the design process of the microbolometer in this paper,the MEMS finite element software Intellisuite was used for mask design,virtual process simulation,3D modeling and finite element mesh dividing,and the thermal and mechanical performance simulation analysis as well.At the same time,according to the test results of related devices,the optimization design method was modified to effectively improve the reliability and accuracy of device design results.Firstly,the design simulation of the microbolometer of 37?m × 37?m,25?m × 25?m and 17?m × 17?m were finished,including electrical,mechanical and thermoelectric coupling simulation.And DOE strategy was introduced to optimize the mechanical simulation.Absorption characteristic simulation was also accomplished by Matlab software.The equivalent temperature difference of the noise was also analyzed.At the same time,the unit test bench was built where the device can be tested in vacuum environment.Considering the corresponding relationship between the response voltage and frequency,the frequency of the blackbody radiation was converted by chopping.The response voltage of the three sizes of microbolometer cell structure was tested.The voltage response rate and thermal time constant were calculated.Comparing the test and simulation result,performance deviation was analyzed and proposed to improve design scheme.By considering the error of the absorption rate,response voltage was corrected.Then the simulation data was fitted and analyzed to improve the design accuracy.The self-heating effect was also taken in consideration to correct the deviation of the thermal time constant.The thermal time constant increased by about 2ms and the thermal conductivity decreased by about 20% after the TCR constant was corrected.Finally,the design of a 12?m × 12?m small-scale microbolometer for ultra-largescale uncooled infrared focal plane detector module was developed,the optical absorption film system was established,and the thickness of each layer of the high absorption rate film system was comfirmed,and a 3D model was built as well.The stress deformation of the 12?m × 12?m micro-bridge structure was simulated,and the infrared absorption rate was calculated by Matlab software to ensure its high absorption rate and stability.Using the improved simulation method,the resistance,the value of TCR,thermal conductivity G,thermal capacity C,and thermal time constant ? of the structure were calculated.In this way,the designing time was shortened and a more accurate microbolometer structure was obtained.