Thermal Deformation Suppression Chip Based on Material Symmetry Design for Single Center Supported MEMS Devices

Abstract

Structural thermal deformation is an important factor that affects the performance of MEMS devices. The mismatch of thermal expansion coefficient (CTE) between different materials is a major source. For single center supported MEMS devices, expansion difference between device and the substrate leads to the out of plane thermal deformation of the structure, resulting in the performance deterioration. This paper presents a thermal deformation suppression chip (TDSC) for single center supporting MEMS devices. It is fabricated by the MEMS process and consists of an upper plate and a lower plate. The materials of the upper and lower plates are the same as those of the device substrate and structure respectively. The principle of TDSC to suppress thermal deformation is material symmetry design. Single center anchor is adapted to connect the upper and lower plates. Besides, the center anchor can also isolate the packaging stress generated between TDSC and package shell. In this paper, center supported quadruple mass gyroscope (CSQMG) is used to verify the effect of TDSC. Finite element simulation shows that the thermal deformation suppression effect is determined by radius of TDSC anchor, and the deformation can be suppressed to 0. The conclusion is confirmed by White light interference experiment. In addition, the experiment results also show that the TDSC effectively reduce the thermal out-of-plane deformation after packaging, which is even better than that of the gyroscope without any packaging. It is further proved that TDSC can also significantly improve the temperature performance of the CSQMG. Moreover, the TDSC has simple process steps, small chip area, low cost, and is suitable for various MEMS devices with single center anchor.

Keywords

• CTE mismatch
• single center supported
• material symmetry
• thermal deformation suppression chip
• packaging stress isolation