Micromachining of CVD diamond by RIE for MEMS applications

Reactive Ion Etching (RIE) is an effective method for etching of diamond films. In this paper, the influences of maskant, gas pressure and the composition of reactive gas on the etch rate and etched surface of diamond are studied. The patterned metal film used as hard mask plays an important role in etching process, it can be sputtered and re-deposited as metal oxides on the etched surface of diamond, acting as a micromask on the bottom face and a passivating layer on its sidewall. Trying to enhance the sidewall passivation and destroy the micromask on the bottom of the etched trench, the diamond film can be precisely patterned into smooth, steep and straight microstructures with inerratic and integrated boundaries and well kept dimensions of patterns as well. This is the so-called sidewall passivation mechanism for micromachining of CVD diamond. A gas mixture of oxygen and argon is used as the etching gas, with the concentration of argon being in the range of 0% to 100% (V/V), and the etching result reveals that increase in argon always leads the etch rate to going down, thus it is not necessary. The gas pressure influences the etched surface and etched contours of fabricated diamond microstructures remarkably.