大厚度硅结构高精度干法刻蚀技术研究

Study of Deep Reactive Ion Etching（DRIE）of Silicon Structures with Large Thickness

关键词:  微机电系统  深硅刻蚀  侧壁垂直度  刻蚀均匀性

Key words:  MEMS  DRIE  Sidewall angle  Etch uniformity

摘要:

增大敏感结构厚度是提高微机电陀螺性能的一个途径。对大厚度敏感结构，在刻蚀过程中易出现“长草”、“缩口”和“屋檐”等典型缺陷，同时刻蚀后侧壁垂直度、刻蚀均匀性较差，严重影响其尺寸精度。研究了刻蚀/钝化比、刻蚀阶段钝化气体通入时间和反应气体流量等工艺参数对刻蚀形貌的影响，提出了一种分步刻蚀的方法，获得了侧壁垂直度8995°与片内均匀性34％的刻蚀结果。

Abstract:

The performances of a MEMS gyro can be improved by increasing the thickness of sensitive structure. For the silicon structure with large thickness, the grass, closing up, the eave and other typical defects are usually come out during the DRIE, which deteriorate the dimensional accuracy. In this paper, the effects of the key process parameters on the DRIE results are studied. The parameters include the etching and deposition time ratio, the duration of the passivation gas flow in etch phase and the flow rate of SF6. In order to improve the dimensional accuracy of silicon etching, a new multi-step process with different etching parameters in each step is presented. With this method, the grass effect, closing up, and the eave effect are successfully suppressed and the profiles with a side wall vertical of 8995° and a uniformity of 34% in a whole wafer are realized.