A Technique Of Shortened Procedures On MEMS Machining Based On Laser Writing

Photolithography of traditional MEMS (Micro-electromechanical System) machining process usually transforms pattern by mask. The design and production of mask is indispensable procedures of traditional MEMS machining process. It requires valuable equipments and takes more time. With extreme high peak power, ultra-short laser pulses is good at micromachining as cutty, surface reparation and otherwise.In this thesis, with application of directly writing by ultra-short laser pulses instead of traditional lithography is put forward. First, the surface of substrate is covered by a layer of thin mask, which function is similar to photoresist. The mask is ablated by high power laser pulses. The ablated part can be directly removed to be patterned. This procedure is different to traditional photoresist procedure. The following procedure is removal of residual layers which is ejected on laser directly ablation. The later chemistry etching is the same as which of traditional MEMS machining process. The substrate is protected by the mask.Fashion of laser directly writing brings that MEMS has cut short the processing flow, cycle and its cost. So, for different with traditional MEMS machining, this paper names this technique as a technique of shortened procedures on MEMS machining (sp-MEMS machining). In this paper, we explore about how to optimize this technique and the feasibility of theory, study the key of it by experiments.In the field of short pulse laser, femtosecond laser has shorter pulse width and higer peak power than picosecond-nanosecond pulse laser. Theoretical analysis and experimental result show that femtosecond laser is superior for sp-MEMS machining.Experiment has been done on silicon(100) wafers (SiN film) by using laser of 800nm wavelength and 50fs pulse width, etched with KOH solution, and the etch mask is removed by HF solution. Experimental result shows that movement of stage and pulse energy influences the depth and width of writing. When movement of stage is picked up and pulse energy is hold, the depth of writing decreases exponentially. But when the velocity of stage movement is higher 5,000μm ? s?1, the change of velocity has no effect on the width of writing. At the same time, we can control the width of lines and precise removal of mask. So sp-MEMS machining is a kind of controllable micromachining technique.Sp-MEMS machining is suitable for a small amount of MEMS samples manufacture, also have showed prospect of extensive application.