Spectroscopic study of plasma using zirconium tetra-tert-butoxide for the plasma enhanced chemical vapor deposition of zirconium oxide

Abstract

Plasma enhanced chemical vapor deposition of zirconium oxide using zirconium tetra-tert-butoxide (ZTB) as a metalorganic precursor, Ar as a carrier of the ZTB vapor, and O2 as an oxidant was investigated by using optical emission spectroscopy (OES), Langmuir probe, and x-ray photoelectron spectroscopy (XPS). The electron temperature (Te) and the O2 to Ar flow rate ratio (O2/Ar) were found to dominate the plasma chemistry: the Te determined the maximum Zr and Zr+ emission intensities at an intermediate pressure of 45 mTorr, the high C/C2 emission intensity ratio in the oxygen-rich plasma, and the transition between the dissociation-dominated chemistry at low pressures and the recombination-dominated chemistry at high pressures. The O2/Ar ratio changed the relative abundance of various atomic and diatomic species in the plasma: both ionic and atomic Zr species were depleted with the addition of O2 and a significant amount of ZrO and CO was produced. The O2/Ar ratio and Te determined the concentration ratio of C/O and C2/O in the plasma, the production and dissociation rates of diatomic molecules (C2, CH, CO, and OH), and the degree of decomposition. From XPS, x-ray diffraction, and OES measurements, the deposited ZrO2 was found to be stoichiometric and amorphous at O2/Ar ratios ⩾0.2, and hydrocarbon molecules rather than atomic carbon were more responsible for the carbon incorporation into the film. The carbon content in the film could be controlled by monitoring and varying the OES intensity ratio of C2 at 516.52 nm to O at 777.42 nm.