Temperature Gradient Method for Alleviating Bonding-Induced Warpage in a High-Precision Capacitive MEMS Accelerometer

Abstract

Capacitive MEMS accelerometers with area-variable periodic-electrode displacement transducers found wide applications in disaster monitoring, resource exploration and inertial navigation. The bonding-induced warpage, due to the difference in the coefficients of thermal expansion of the bonded slices, has a negative influence on the precise control of the interelectrode spacing that is essential to the sensitivity of accelerometers. In this work, we propose the theory, simulation and experiment of a method that can alleviate both the stress and the warpage by applying different bonding temperature on the bonded slices. A quasi-zero warpage is achieved experimentally, proving the feasibility of the method. As a benefit of the flat surface, the spacing of the capacitive displacement transducer can be precisely controlled, improving the self-noise of the accelerometer to 6 ng/√Hz @0.07 Hz, which is about two times lower than that of the accelerometer using a uniform-temperature bonding process.

A Semi-Linear Elliptic Model for a Circular Membrane MEMS Device Considering the Effect of the Fringing Field

“…This because they provide an excellent approximation of the human–machine interface in all the cases wherein miniaturized-integrated electromechanical systems are required [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Since the first batch device was produced in 1964 [ 22 ], the scientific and technological development in the field has strongly influenced the analysis and synthesis of physical-mathematical models that can describe the extremely complex underneath MEMS multi-physics [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. However, such theoretical models hardly provide analytical solutions.…”

Research on High-Resolution Miniaturized MEMS Accelerometer Interface ASIC

“…In Equation (20), fs is the sampling frequency. The equivalent noise of the charge amplifier is independent of the transistor parameters; it is only related to the capacitance of the sensitive structure, integral capacitance, and sampling frequency.…”

“…After calibration, the parasitic mismatch-induced bias could be suppressed to sub-mg level. With the development of MEMS technology, the integration, intelligence, and digitization of capacitive MEMS accelerometers have become an important research direction [ 18 , 19 , 20 ]. It is of great significance to study closed-loop interface circuits for high-performance capacitive MEMS accelerometers.…”

A New Approach for the Control and Reduction of Warpage and Residual Stresses in Bonded Wafer

“…In [ 19 ], by utilizing the analysis of variance, the most effective parameters on the warpage are found to be the substrate and the epoxy moulding compound thicknesses, while the least effective parameter is the substrate material. Liu et al [ 20 ] proposed a bonding process with different temperature peaks at the cap and the sensor wafer. This thermal gradient approach results in a significant warpage reduction for silicon to glass wafer bonding.…”