A Technique of Shortened Procedures on MEMS Machining Based on Laser Writing
|School||Huazhong University of Science and Technology|
|Course||Machinery and electronics|
|Keywords||Microelectromechanical systems Laser Technology Femtosecond laser Short process technology Micromachining|
Traditional microelectronic mechanical systems (Micro-electromechanical Systems, MEMS) in the processing flow that contains a photolithography process is generally through a lithographic mask to achieve graphics conversion. Traditional MEMS processing process must exist during the preparation of the lithographic mask, the process equipment requirements, and time consuming. Ultrashort laser pulses with high peak power, this feature makes it suitable for cutting and micromachining, surface repair. The paper described the direct write mask using ultra-short laser pulses to achieve the conversion of the graphics, instead of the original lithography mask mode. First using physical or chemical methods to be processed in the wafer surface covered with a mask, and then using a high power laser beam to inscribe the silicon surface of the mask layer, and is etched portion is directly removed, form the graphic. Unlike traditional photoresist lithography modified process. Subsequently a developing process is simply to clean the residue was ejected in the laser direct writing. Late chemical etching is completely similar to traditional MEMS processing, mask layer under it silicon protective effects. Laser direct-write processing makes MEMS processing flow reduction cycles, reduced processing costs. Therefore, in order to distinguish it from the traditional MEMS processing technology, the paper referred to this process as the process of the MEMS short process. The thesis that the process optimization and feasibility of the theoretical discussion, experimental study of the process key technologies. In the field of short-pulse laser, the femtosecond laser nanosecond, picosecond laser pulse width shorter with higher peak processing power. The theoretical analysis and experimental results show that the femtosecond laser with thermal effects, can process a variety of materials, precision existence of threshold effect characteristics, relatively more suitable for laser direct writing process of MEMS short process. Optional repetition frequency of 1kHz, the pulse width 50 fs, and the center wavelength of 800nm ??femtosecond laser in the silicon nitride film layer is covered with a silicon wafer on inscribing, potassium hydroxide is used for the chemical etching, using hydrofluoric acid to remove the mask layer. Experimental results show that the the the laser inscribing depth, the width of the laser inscribing by single pulse energy, the impact of the platform moving speed. Pulse energy to maintain a certain time, the platform moving speed of the laser inscribing depth exponential decrease, and in the speed is greater than 5,000 μm? S? 1 speed change to inscribe width almost no effect. This rule implies the processing of short process inscribed linewidth control at the same time be able to accurately remove the mask layer of the premise. In short, the processing of short process is controllable micro-processing technology. The process of MEMS short process applies to the rapid development of a small amount of MEMS samples, has a broad application prospects.