Fabrication of Micro-Cantilevers Using RF Magnetron Sputtered Silicon Carbide Films

In the present work, silicon carbide (SiC) films were deposited by RF magnetron sputtering process on Si (100) substrates for micro-cantilever fabrication. The films were deposited without external substrate heating using a ceramic SiC target at 10 mTorr sputtering pressure, 200 W power and 50 mm target-to-substrate spacing. X-ray diffraction pattern shows that the films were amorphous in nature. In order to investigate the chemical inertness, the SiC coated Si substrates were dipped in buffered HF (BHF) at room temperature and in 40% KOH solution at 80 °C for varying length of time. Atomic force microscope was used to investigate surface roughness and morphology of the films before and after chemical processing. Micro-cantilever beams of the SiC film were fabricated by a single mask process. The SiC film was patterned using reactive ion etching (RIE) in SF6-O2 plasma. Thermally evaporated Al film was used as a mask during RIE process. This process also resulted in the formation of convex corners which were exploited for anisotropic etching of Si under the SiC film. The SiC cantilever beams were released by anisotropic etching of Si in KOH at 80 °C without using additional masking material. Scanning electron microscopy was used to observe the fabricated SiC micro-cantilever beams. The morphology of the SiC film after prolonged exposure to KOH was observed to be similar to that of the as-deposited film. The RF magnetron sputtered SiC films were found to be highly inert in KOH and BHF solutions. Due to difficulty in micromachining of bulk SiC material and its high cost, the RF sputtered SiC films on Si can provide a low cost structural material in MEMS.