THICKNESS DETERMINATION OF SIC-ON-SI THIN-FILMS BY ANISOTROPIC REACTIVE ION ETCHING AND PREFERENTIAL WET ETCHING

An accurate and relatively simple technique for measuring the thickness of thin SiC films (20-300 nm) on Si is described. The technique consists of SiC patterning by anisotropic reactive ion etching in fluorinated plasma followed by selective and crystallographically preferential wet chemical etching of the underlying Si in KOH/isopropyl solutions. This process reveals a free-standing portion of the SiC film which can be readily examined and measured by scanning electron microscopy (SEM). The location of the SiC/Si interface, which is very difficult to determine by other measurement techniques, is very distinct after the preferential etching. The minimum film thickness that can be readily measured (approximately 30 nm) is only limited by the resolution of SEM. The measurement accuracy is approximately +/-10% and is dependent on the film surface roughness. Film thickness values obtained with this technique are compared to those provided by ellipsometry and cross-sectional transmission electron microscopy.