Research On Vacuum Reliability Testing Technology Of Wafer-level Package Uncooled Infrared Detector

Uncooled infrared focal plane detector(IRUFPA)has the advantages of low cost,small size,light weight,no refrigeration,etc.It has broad application prospects in the field of thermal imaging.In order to improve the performance of the detector,it is necessary to vacuum package the UFPA device and ensure that the device works in a vacuum environment under 5 Pa for a long time.A Micro Pirani vacuum gauge compatible with the device manufacturing process is built into the UFPA device packaging cavity,which can monitor the vacuum inside the device in real time,it is very important for the vacuum reliability of the device.The main content are as follows:Explore the working principle of the Micro Pirani vacuum gauge,on this basis,simulate the performance of the device,determine the key structural parameters of the device,and complete the layout design and production process design of the device,successfully produced the device,and finally tested the device performance.In the study of the working principle of the Pirani vacuum gauge,the gas heat dissipation model was simplified to a gas molecule collision heat exchange model between two parallel plates with a certain temperature difference,and a mathematical model of the device was established.Considering the performance requirements,process compatibility of the device,the test error of the test platform and the laboratory preparation conditions,several key structural parameters of the Micro Pirani vacuum gauge that meet the project requirements are determined through theoretical calculations as follows:The area of the micro-bridge structural unit cell is 37×37?m~2,the length of the bridge legs is 74?m,and the width is 0.8?m,the area of the bridge surface is 789?m~2,and the height of the suspended cavity of the micro-bridge is 2?m;Combined with the processing characteristics of the device,the layout design of the device unit and overall structure and test electrode was designed and completed.The device was fabricated through a micromechanical process,which is compatible with the UFPA device process,thereby obtaining a miniature Pirani vacuum gauge with complete appearance and no structural collapse.Build a test platform and use the four-wire method to accurately measure the change in resistance,reducing the measurement error of resistance.At the same time,the vacuum calibration is completed,and the best working current of the device is determined.It can be seen from the test that the device has good repeatability and consistency,Comparing the calculation results,it is found that the response of the resistance and thermal conductivity under different vacuum degrees is in good agreement with the theoretical calculation.In addition,a special PCB board for testing is designed,which effectively solves the problem that the probe scratches the test electrode and the surface of the device during the test and causes the device to fail.