Characteristics of CeO2 thin films etched with a high-density CF4/Ar plasma

Cerium dioxide (CeO2) was used as an intermediate layer for a metal-ferroelectric-semiconductor field-effect transistor to improve the interface property by preventing the interdiffusion of the ferroelectric material into the Si substrate. CeO2 thin films were etched with a CF4/Ar gas combination in an inductively coupled plasma (ICP). The maximum etch rate of the CeO2 thin films was 270 A/min for CF4(20%)/Ar at 600 W/-200 V, 15 mTorr, and 25 .deg. C. The selectivities of CeO2 to the photoresist and SrBi2Ta2O9 were 0.21 and 0.25, respectively. The surface reaction of the etched CeO2 was investigated with X-ray photoelectron spectroscopy(XPS) and secondary-ion mass spectrometry (SIMS). Ce reacts with F radicals and forms Ce-F bonds, which remain on the surface of the CeO2. Those products can be removed by Ar-ion bombardment sputtering. The etch slope of CeO2 with the 0.5-μm line pattern was about 65 .deg. C