Design and Development of an Integrated MEMS Sensor for Real Time Control of Plasma Etching

B.G. Morris and G.S May
Georgia Institute of Technology, US

Keywords: ANSYS, micromachined sensor, reactive ion etching, real-time control, resonant frequency

Abstract:
This paper explores a novel technique for monitoring film thickness in reactive ion etching that incorporates a micromachined sensor. The prototype sensor correlates film thickness with the change in resonant frequency that occurs in the micromachined platform during etching. The prototype sensor consists of a platform that is suspended over a drive electrode on the surface of the substrate and electrically excited into resonance. As material is etched from the platform, its resonant vibrational frequency shifts by an amount proportional to the amount of material etched, allowing etch rate to be inferred. The micromachined sensor is simulated using ANSYS 7.0. Simulation shows a direct correlation between platform film thickness and resonant frequency, as well as between the platform thickness and its capacitance. Modeling the sensor as a variable capacitor in an auto-zeroing floating gate amplifier (AFGA) circuit using HSPICE reveals that the deflections of the platform are amplified as expected

Nanotech 2004 Conference Technical Program Abstract