Research On The Key Technology For SOI-based Micromachined Gyroscope Manufacturing

The performance of the micromachined gyroscope has been a bottleneck which limits its development and application.The key factors influencing the performance of the micromachined gyroscope include structural design,chip manufacturing and interface circuit.Among them,the chip manufacturing procedure which converts the layout to the physical entity by chip processing and chip packaging technique determines the performance of the gyroscope to a great extent.Footing,stiction,dicing damage and packaging stress are the common problems in gyroscope chip manufacturing.These problems will cause the degradation or failure of the gyroscope which have a strong impact on its performance and yield.This dissertation focuses on the effect of footing,stiction,dicing damage and packaging stress on the micromachined gyroscope.On this basis,a dicing-free process based on SOI double-side etching technique and a low stress vacuum package technology are developed.The proposed manufacturing technologies can prevent the gyroscope from performance degradation and structure failure,which improved the performance and yield of the gyroscope significantly.The main contents are as following:The model describing the effect of footing,stiction,dicing damage and packaging stress on the gyroscope is established.Taking the symmetric gyroscope and the tuning fork gyroscope as examples,the generation mechanism of footing,stiction,dicing damage and packaging stress and its effect on the gyroscope are discussed and analyzed.The established model provides the theoretical support for the gyroscope structure optimization and the manufacturing technology improvement.A dicing-free process based on SOI double-side etching technique is proposed to solve the problems of footing,stiction and dicing damage.More precisely,the dicing-free process forms cavities on the SOI handle layer by the double-side etching technique to eliminate the footing effect in DRIE process and stiction in wet releasing step.Moreover,the gyroscope chip is separated by the misplaced double-sided grooves to avoid the structure fracture and the fragments pollution.The proposed process improves the processing quality and yield of the micromachined gyroscopes significantly.A low stress vacuum packaging technology which reduces the packaging stress greatly is presented.The packaging stress is reduced by the stress isolation structure which is located on the SOI handle layer.The stress isolation structure constrains the packaging stress within the handle layer which reduces the packaging stress and in-plane deformation of the gyroscope for two orders of magnitude.The packaging stress induced chip warping is also reduced for more than 10 times.Finally,a symmetric gyroscope and a tuning fork gyroscope are fabricated by the proposed dicing-free process and low stress vacuum packaging technology.The bias stability of the symmetric gyroscope is up to 2.1 °/h which is promoted by one order of magnitude contrasting to previous prototype.The bias stability of the tuning fork gyroscope is 8.8 °/h with a bandwidth of 270 Hz,which is a high-bandwidth,tactical-grade gyroscope.