A study on the surface correction of large format infrared detectors

Abstract

Large format hybrid infrared focal array detectors, which require a wide range and high resolution, are of significant technical importance for earth observation systems and scientific space programmes. A typical large hybrid infrared focal plane array (IRFPA) detector formed by a detector chip is directly hybridized to a silicon readout integrated circuit (Si-ROIC) via indium bumps. However, for a large format IRFPA detector, the connection rate of the indium bumps strongly depends on the warpage of the Si-ROIC and the detector chip, which usually results from technological processes. In this paper, a surface correction structure is proposed to optimize the warpage of the Si-ROIC and the detector chip before flip-chip. The warpage of the Si-ROIC is analysed by the finite element method. The simulation results are in good agreement with the experiment. After optimization, the warpage of a 2048 × 2048 Si-ROIC decreased from 13 μm to less than 3 μm. Thus, it is beneficial to improve the IRFPA bump connection rate. Compared with traditional growth stress films, this method is more flexible and has easy accessibility. Eventually, it could enhance the stability of the large format IRFPA detector.