| Micro-Electro-Mechanical Systems（MEMS）is an advanced manufacturing technology developed on the basis of semiconductor manufacturing technology that allows the construction of stand-alone intelligent systems on a size of a few millimetres or even smaller.MEMS are widely used in accelerometers,gyroscopes,micro-mirrors and micro-resonators due to their outstanding features of miniaturisation,intelligence,multi-functionality and high integration and have been successfully commercial applications.Micromirror is an important branch of MEMS.It uses micromachining technology to prepare microscopic mirrors,and drives the mirror surface to deflect or displace through microscopic driving structures.Due to its miniaturization and low power consumption,it is widely used in optical switches,displays,medical endoscopy mirrors and Li DAR,especially in today’s rapid development of autonomous driving technology,Li DAR’s demand for reliable MEMS micromirrors is also increasing.The drive methods are electromagnetic drive,electro-thermal drive,piezoelectric drive and electrostatic drive,of which electrostatic drive has a relatively simple structure,with fast response time and low power consumption,and is the most typical drive method.The vertical comb drive structure is currently the most widely used in electrostatic drive.This structure has a high driving force density and a wide continuous scanning range,so it is the focus of research by people in the industry.The manufacturing methods can be roughly divided into two categories according to the relative positions of the fixed comb teeth and the movable comb teeth: angular vertical comb drive structure（AVC）and staggered vertical comb drive structure（SVC）.The fixed and movable combs of the AVC structure are fabricated synchronously in the same plane,while the fixed and movable combs of the SVC structure are fabricated in two steps,and there is a vertical drop.In this paper,a staggered vertical comb-drive MEMS micromirror fabricated by bonding process based on SVC structure is designed,and its fabrication process is explored.The main research contents are as follows.（1）Based on the theoretical basis of the SVC-type electrostatic comb drive structure,the dimensions of the comb structure and the torsional beam dimensions of the micromirror were designed based on the analytical model equation of electrostatic drive and the characteristics of rectangular rod torsion in material mechanics,and a theoretical structurally stable device structure size was finally determined,with a theoretical maximum deflection angle of 10.3° for the micromirror when a drive voltage of 80 V was applied.（2）After completing the size design of the device structure,based on the experimental conditions and methods,the entire experimental process is completely designed,and the bonding method is used to prepare the micromirror structure.The overall experimental idea is: first complete the etching of the plate pattern,the reserved active space for the mirror surface and the bottom comb structure on the first silicon wafer,and then bond another silicon wafer on this sample,and the bonding The top silicon wafer is thinned and polished,and then the top comb tooth and micromirror structure are etched,and electrodes and reflective layers are prepared.（3）According to the experimental steps,use L-Edit software to draw the layout of each step,and reasonably arrange the arrangement of the devices on the sample.（4）Following the experimental design,the whole process of preparing the micromirror structure was explored,and problems were identified and solved during the experiments.The mask layer material,the type of photoresist and development conditions required for lithography,the deep silicon etching conditions and bonding conditions were finally determined for each etching step,and the prototype was finally successfully dissociated into a single device of 2 mm x 2000 mm. |
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