Research On The ICP Key Technology And The Detection Circuit For Accelerometer Sensor

Minimize size, to achieve the micromation--this is one of the main technical targets to the sensor. Micromation is not only to decrease the number of the element but also to make a basic system with the minimum size as far as possible. The study on Micro Electro Mechanical System-MEMS is a primary externalization of the trend. As the MEMS industry matures, MEMS acceleration sensors have also become a successful commercial device following the pressure sensors. The main advantages of capacitive accelerometer are high sensitivity and accuracy; good stability, small temperature drift, low power consumption; good ability of overload protection; self-checking by static electricity and etc. So it is widely used.In recent years, by introducing and modificating the technology, China sensors have formatted a certain industrial foundation and ability of fabrication. Five kinds of new type sensor have been included in the focus of research and development, one of which is MEMS. According to the "2006 ~ 2007 China Electronics Companies" compiled by the Institute of Scientific and Technological Information of Ministry of Information Industry, there are 455 manufacturers fabricating the sensitive components and sensors in China mainland. At present, the sensor technology is developing in the direction of intelligent, miniaturized, low-power, wireless, portable. The demand of the sensor applications has a sustained high-speed growth. While the international giants have entered the sensor intense competitive environment, the Chinese mainland sensor industry is faced with new opportunities for development and challenges.This paper presents a area-variable micro-machined capacitive accelerometer. It consists of a silicon upper electrode and a glass lower electrode. They are bonding together. The upper electrode is a movable plate, the lower electrode is a fixed electrode plate, the two plates formed a capacitance. The upper electrode is made up of mass and folded beams. When there is a inertial force, the mass will have a micro-displacement. According to the principles of mechanics of materials, we can know that the relation between the deformation of the cantilever beam and the acceleration is proportional, in another word, the relation between the micro-displacement of the mass and the acceleration is linear. It solved the difficult problem of the complex detection circuit for the nonlinear signals of the space variable capacitive accelerometer sensor.According the difference of the support beam structure and number, we proposed two kind of folded beam design--dual-beam and four-beam. Further, the formula of mass displacement under accelerometer, variation of capacitance and the effective rigidity of folding spring are deduced by utilizing knowledge of material mechanics. From these formulas, we get the relationship among structural parameters. In addition,this theis study the effective operating range of folding spring through its analysis of inactivation. The performance index such as natural frequency, sensitivity, measurement range damping, distinguish ability are also discussed. Further more, the method of theory optimization is put forward, acted as a theoretical basis for the modeling and simulation. We use the finite element analysis software ANSYS to modeling and entities simulating respectively on the dual-beam and four-beam structure. And the static structural analysis and its anti-overload situation are separately done on the folded beam. By changing the thickness of the folded beam and the mass, spring horizontal width, we anglicizing the modals and the stress distribution of the two structures. After simulation analysis, we decide to choose the four-beam structure under the premise of that we can get the optimum performance. The structural parameters are optimized and the structure of the device is tentatively determined.The technique of the ICP etching is the key technique to fabricate the acceleration sensor sensitive part. This thesis introduces the principle of ICP etching process and equipment working principle in-depth. And we show the effects on the results of the etching by different parameters. We find that the flux of the gas and the duration of the etching are very important to the result of the etching. If the gas flow or etching time becomes larger, the effect of etching is larger too. Contrarily, if flow or time of the protecting gas changes larger, the performance for the protection becomes larger. When the power of the lower electrode plate increases, etching also will be increased, leading to severe corrosion at the bottom side. Adjusting the pressure of the reaction chamber will lead to the change of the etching result. Regularly speaking, if you reduce the reaction pressure, the etching can increase. But it decreases when the pressure exceeds a certain value, the etching effect will lead to smaller because of the decreases of the plasma density. We can finally get the best process parameters to obtain the spring beam by quantity experiments.We designed the detailed processes to fabricate the acceleration sensor, and confirmed the optimum parameters of the equipment every step used according to quantity experiments results. The reasons of the problems we met in the process are analyzed, and the problems are solved For exampled, in order to solve the problem of double-sided lithography, we have adopted a common lithography machines by using the alignment makers twice to achieve double-sided lithography. These research results have some innovation, they provide a number of new ways to solve the problem in the fabricating process of MEMS accelerometer sensor, and the conclusions of the study are certain universal, they are also suitable to other types of MEMS devices.A single-carrier dual integrator modulation detection circuit is designed for an area changeable capacitive micro-machined accelerometer in this thesis, there are theoretical analyses and detail data for choosing and designing of the detection circuit for micro-machined accelerometer. After comparing square wave with sine wave as the carrier wave, we choose 100 kHz sine wave as the carrier wave. Then the specifications of open-loop accelerometer are given,with factors influencing each performance analyzed.