非制冷红外焦平面微桥形变的主要原因及其控制

Main reason for deformation in microbridges of uncooled IRFPA and their control

微桥是微测辐射热计阵列像元的重要部分,经微细加工工艺制成的微桥结构常常发生弯曲变形,从而严重影响器件性能。利用有限元分析方法研究了造成微桥变形的原因。结果表明,重力导致的微桥形变值仅为1.44×10-5μm,而薄膜的本征应力导致的形变值却高达2.108μm,与实际观测值相当。因此,本征应力是造成微桥变形的主要原因。此外,还研究了本征应力梯度导致的形变,并提出了采用在电极的表面再沉积一层SiNx薄膜的方法,使桥腿的形变值由0.587μm明显地减小到0.271μm,有效地控制了本征应力梯度导致的桥腿变形。

Microbridge is an important part of the pixel of the bolometer arrays. Microbridges prepared by micro-fabricating process are usually deformed, which is harmful to the devices. The reason why the microbridges were deformed was investigated in this article by using finite element analysis. Results indicate that the deformation caused by gravity is 1.44×10^-5 μm. In contrast, the deformation induced by intrinsic stress is as high as 2.108 μm, similar to that observed practically. These suggest that the intrinsic stress is the main factor for the deformation of the microbridges. The deformation caused by intrinsic stress gradient was also investigated. A way of adding another SiNx thin film on the surface of electrodes for controlling the deformation was proposed. Thus, the deformation of beam caused by the intrinsic stress gradient can be obviously reduced from 0.587 μm to 0.271 μm, effectively controlling the deformation.