Simulation And Optimization Of A Micro-Machined Silicon Condenser Microphone Using A Perforated Diaphragm

Micro electro mechanical system (MEMS) is an advanced scientific field of multiple highly interactive subjects. It’s developing very fast in recent twenty years, and it is a hotspot of scientific research. As an important branch in MEMS, micro-machined silicon microphone has been the focus of people’s attention in recent years. The microphones are widely used in mobile phones, laptops, mp3, hearing aids and so on. It is replacing the traditional microphone gradually. So, the study on the micro-machined silicon microphone is of far-reaching significance.View in a large number of literatures about MEMS microphones, the present research and development trend of MEMS microphones are analyzed and summarized. Study the working principle, performance indicators, simulation methods and other content of different types of MEMS microphones, and then compare their advantages and disadvantages. On this basis, this paper analyzes, simulates and optimizes the micro-machined silicon condenser microphone because this kind of microphone has the advantages of higher sensitivity, flatter frequency response, better thermal stability and so on than other micro-machined silicon microphone. It is the mainstream in MEMS microphone market. The main work and results of this paper are listed as follows:1. After comparing the advantages and the disadvantages of the existing structures for the microphone and simulation methods, this paper designs a micro-machined silicon condenser microphone using a perforated diaphragm. Different from the microphone using a perforated back-plate, this kind of microphone avoids making the holes on the back-plate and etching the back chamber. For this structure, a new modeling method is proposed, which combines the finite element analysis and the microphone equivalent circuit to establish a more accurate microphone equivalent circuit, and simulate it using Pspice.2. Analyzes the effects of diaphragm area, the number and the distribution of the microphone acoustic holes and air gap on the microphone performance, which can provide the theoretical guidance for the design of microphone. 3. Proposes an algorithm to optimize the structure of this microphone. This algorithm is similar to the steepest descend method. The expression of the objective function is unknown, the simulation of microphone should be used to solve this problem. Through this algorithm, a set of microphone parameters can be got which let the microphone not only meet the frequency requirement, but also has a better sensitivity.4. Initially proposes the fabrication process and the package of the microphone. The technology of the fabrication process is surface micromachining, it can be compatible with CMOS process.