Highly Chemical Reactive Ion Etching of Silicon in CF4 Containing Plasmas

Silicon (Si) etching process with low temperature is used for initial processing of semiconductor field emitter array cathodes for vacuum microelectronics, for optical reflecting gratings, for opto- and micromechanical devices. Most of them are performed by dry etching process especially in reactive ion etching (RIE) method with fluorocarbon-gases such as CF₄, CHF₃ and C₃F₈. In this work, results are shown that reactive ion etching of silicon using CF₄/H₂ is capable at meeting the requirement (anisotropy, high etch rate and high selectivity, simultaneously) similar to that by using reactive ion etching with fluorine-containing plasma. We have investigated the etching rate dependency on the percentage of hydrogen in the gas mixture, the total pressure and flow gas and found that by using a gas mixture with 33% of H₂, the optimum rate of Si is achieved. The etch rate are found to increase with voltage, attaining a maximum rate 1780 A/min at -482V. Surface morphology of the etched samples is characterized by scanning electron microscopy and atomic force microscopy. The results revealed that the etched surface was anisotropic and the smoothness of the etched surface is comparable to that of polished wafer.