MEMS硅半球陀螺球面电极成形工艺

Development of spherical capacitive electrodes of MEMS silicon hemispherical gyros

由于球面电极是曲面结构,电极各处的电感耦合等离子体(ICP)刻蚀深度不一致,在加工过程中常发生球面电极还未刻蚀到位而谐振器已被破坏的现象,故本文提出了新的球面电极成形工艺。基于ICP刻蚀固有的lag效应,采用刻蚀窗口宽度由60μm渐变至10μm的V形刻蚀掩模调制电极各处的刻蚀速度,在电极各处获得了基本一致的归一化刻蚀速度(2.3μm/min)。利用台阶结构拟合球面电极的3D曲面结构,并保证通刻阶段的硅厚度基本一致为150μm来消除球面电极加工时最薄处已经刻穿阻挡层并破坏谐振器而最厚处还没有刻蚀到位的现象。结合台阶状的二氧化硅掩模对球面电极各点处的硅ICP刻蚀当量进行了调整,使其基本相等,通过一次ICP刻蚀即完成了对硅球面电极的加工。利用提出的方法成功制备出了具有功能性输出的微机电系统(MEMS)半球陀螺的硅球面电极,其最大半径可达500μm。

Due to the spherical shape,the spherical electrode has different etching depths in ICP（Inductively Coupled Plasma）etching,and the resonator following the stopping layer is often damaged in the thin place of the electrode before the ICP etching front reaches the stopping layer in the thick place of the electrode.Therefore,this paper proposes a novel method to fabricate 3Dsilicon spherical electrodes.On the basis of the inhenrent lag effect of ICP etching,a V-shaped mask with an open window width gradually shrinked from 60μm to 10μm was used to modulate the etching speeds of the electrode and the etching speed was tuned to be a normalized speed nearly 2.3μm/min in all places of the electrode.Then,a silicon step structure was used to simulate the 3Dspherical profile of the electrode and to ensure the silicon depth of the last step to be about 150μm,by which the etching front across the spherical electrode could be made to reach the stopping layer almost simultaneously.With the step-shaped silicon dioxide mask,the normalized ICP etching depth of the spherical electrode was tuned to be approximately the same and the spherical electrodes were fabricated successfully by one ICP etching process.It concludes that the silicon spherical electrode with functional output for MEMShemisphere gyros can be fabricated successfully,and the maximum radius of the sphere is 500μm.