Design And Development Of The Confined Etchant Layer Technique Micro Fabrication System

With the development of science and technology, function integration,miniaturization and ultra-precision have become the developing direction ofmodern manufacture. Micromachining technology applied in micro electromechanical systems (MEMS) has become the research focus of many researchinstitutes both at home and abroad. Since it determines the machining accuracyand surface quality of micro electro mechanical components, it has also beenconsidered as one of the important marks of national manufacture level.Confined etchant layer technique (CELT) is one kind of chemical etchingtechnique which has advantages as distance-sensitive and mask-free. Itovercomes disadvantages of traditional chemical etching technique as isotropy,poor aspect ratio, poor mask stability, etc. Thus, it can be used in massivereplicate of complicate3D microstructures and has great potential in the field ofmicro fabrication.In this thesis, a set of CELT micro fabrication system has been developedaiming at the process characteristics of CELT micro fabrication. Research hasbeen conducted on the design and development of the CELT micro fabricationsystem from the perspective of improving fabrication accuracy and fabricationefficiency. The main research work consists of the following three parts:(1) Research on the design of the CELT micro fabrication system. Thesystem design is conducted according to the process requirements. Firstly, thegranite base, macro positioning stage and micro positioning stage are designedand optimized in order to improve the stiffness of the system. Secondly, machine vision system and micro force sensing unit are introduced to improve the systemcontrollability. Finally, experiments are conducted to verify the systemperformance.(2) Research on the machining accuracy of the CELT micro fabricationsystem. After analyzing the factors affect the machining accuracy during thefabrication process, research was conducted from these two perspectives of view,improving the system positioning accuracy and improving the zero pointdetection accuracy. Based on the analysis of zero point detection process, anovel zero point detection technique based on digital lock-in amplifier isproposed. With this phase-sensitive filter method, the noise signals withdifferent frequency are removed from the target signal. Since the machiningaccuracy mostly relies on the positioning accuracy, a micro positioning stagebased on flexible hinges and piezoelectric drivers is proposed. After establishingthe hysteresis model of the piezoelectric driver, a control strategy ofPID+feedforward is applied to the micro position stage. Finally, theexperimental results indicate that both the zero point detection accuracy and thestage positioning accuracy are within nanometer level.(3) Research on the processing efficiency of the CELT micro fabricationsystem. During the micro fabrication process, the system needs to withdrawcertain distance and return to zero point for many times due to the processingrequirement. Aiming at improving the efficiency of this repeat operation, amachine vision system and a micro force sensing unit are introduced tomonitoring the fabrication process. A novel automatic approaching method isproposed and verified in the experiment.