Study On MEMS Scanner Based On Electrostatic Comb Drive Actuator

Since it was invented,Micro Electro Mechanical Systems(MEMS)technology has been favored by most engineering fields such as optics,mechanics,and electronics,because of its low cost and good portability.With the development and maturity of Integrated Circuit(IC)in recent years,there are many popular products in MEMS fields,which have attracted a lot of attention in investment and high-tech innovation fields.Among them,MEMS scanning mirrors have the advantages of small size,low driving power consumption,fast response,high scanning frequency,and long life.Thus they have great application value in the fields of Light Detection and Ranging(Li DAR),projection display,optical coherence tomography(OCT)and optical communication,and are important research directions in the field of Micro Opto Electro Mechanical Systems(MOEMS).Because of its good process compatibility,small chip,high reliability and low processing cost,electrostatic comb drive has become a main driving mode of MEMS scanner,and it is also one of the research highlights.However,most of current MEMS scanners driven by electrostatic comb drive actuators are based on Lissajou scanning.They can not generate raster scanning pattern,and have the drawback of small aperture,and so on.In this paper,the electrostatic comb drive actuated MEMS scanner is systematically studied,including theoretical research,structural design,performance analysis,process,testing and packaging.The main contents are as follows:1.Theoretical study on electrostatic comb drive actuated MEMS scanner.The working principle and implementation of electrostatic comb drive actuator,including parallel plate actuator,in plane comb drive actuator,vertical comb drive actuator,and the combination method of comb drive actuator and scanner,are summarized systematically.The scanning dimension,scanning mode and key parameters of MEMS scanner are described.The theory of surface deformation,reflectivity and reliability of MEMS scanner are summarized.2.The structural design,theoretical analysis and simulation of MEMS two dimensional scanning mirror driven by electrostatic comb actuator.A vertical comb drive actuated MEMS two dimensional raster scanner based on stress self-assembly is proposed.The overall structure,slow axis and fast axis are designed.The performances of the scanner,including resonant frequency of fast axis,scanning angle,dynamic deformation,impact resistance,random vibration,are analyzed and simulated.3.Fabrication and performance test of MEMS two dimensional scanner driven by electrostatic comb drive actuator.The design of process flow is carried out,and the process is completed.Some key processes and driving modes are summaried.The performances of MEMS scanner,including surface figure,angle and frequency of fast axis and slow axis,are tested.4.Vacuum testing and packaging of MEMS two dimensional scanner driven by electrostatic comb drive actuator.The laser scanning system and vacuum test chamber are built,and the vacuum test of scanner are finished.Under vacuum condition,the resonant angle of fast axis is greatly increased.The vacuum package of MEMS scanner is designed and fabricated.In conclusion,an electrostatic comb drive actuated MEMS two dimensional raster scanner with a diameter of 4mm is proposed.The fast axis and slow axis are driven by in plane comb drive actuator and vertical comb drive actuator,respectively.A prototype is designed and fabricated.The measurement and package are finished,and optical scanning angle of about 59°×4° is realized.The scanning mirror developed in this work has the advantages of relative large aperture.Vertical comb drive actuators are achieved by bending of frame induced by residual stress and two dimensional raster scanning is realized.Therefore,the Lissajous scanning pattern of current most electrostatic actuated MEMS two dimensional scanner is overcome.It can be applied to a low cost and portable Li DAR system,which has a certain application prospect.The scanner has potential value and promotion effect on the development of MEMS scanner technology in China.