硅微谐振式加速度计的实现及性能测试

为了提高硅微谐振式加速度计性能,从一种基于DDSOG(Deep Dry Silicon on Glass)工艺的硅微谐振式加速度计样机入手,介绍了加速度计的结构、加工方法和接口电路。该谐振式加速度计结构包括敏感质量块、谐振器和微杠杆3部分,采用差动结构来减小共模误差的影响。接口电路中采用了自动增益控制电路来稳定谐振器的振幅,成功实现了谐振器的闭环自激振荡和频率检测。分析了谐振式加速度计频率输出与加速度输入的关系,测试了硅微谐振式加速度计样机性能,结果为量程±50g,标度因数143 Hz/g,零偏稳定性1.2 mg,零偏重复性0.88 mg,阈值170μg。文章最后提出,DDSOG工艺中采用的玻璃材料和硅材料温度系数不同,影响了加速度计的温度特性,因此需要进步一改进加工工艺。

Implementation and experiments of micromechanical differential silicon resonant accelerometer

To improve the performance of MEMS accelerometers, a micromechanical Silicon Resonant Accelerometer (SRA) prototype fabricated by Deep Dry Silicon on Glass (DDSOG) process was introduced, and some experiments for the accelerometer were performed. The structure, processing methods and the interface circuit of SRA were discribed in detail. The SRA adopted the differential structure composed of two identical resonators to eliminate common mode errors, and used the micro lever mechanism to magnify the scale factor. An interface circuit using the Automatic Gain Control (AGC) circuit was designed to maintain the oscillator stability, which could drive the resonator to achieve self-oscillation and to detect the frequency output. The relation between input acceleration and SRA frequency output was researched and the performance parameters of the prototype resonant accelerameter were tested. The test results show these performance parameters to be the sensitivity in 143 Hz/g, input range in ±50 g, bias stability in 1.2 mg, bias repeatability in 0.88 mg and the threshold in 170 μg. Moreover, it is found that the temperature coefficient of glass substrate is larger than that of the silicon structure in the DDSOG process, which affects the bias temperature sensitivity of resonators. Therefore,it points out that the processing method should be improved further.