Lipon thin films grown by plasma-enhanced metalorganic chemical vapor deposition in a N 2–H 2–Ar gas mixture

Abstract

Lithium phosphorus oxynitride (Lipon) thin films have been deposited by a plasma-enhanced metalorganic chemical vapor deposition method. Lipon thin films were deposited on approximately 0.2 μm thick Au-coated alumina substrates in a N 2–H 2–Ar plasma at 13.56 MHz, a power of 150 W, and at 180 °C using triethyl phosphate [(CH 2CH 3) 3PO 4] and lithium tert-butoxide [(LiOC(CH 3) 3] precursors. Lipon growth rates ranged from 10 to 42 nm/min and thicknesses varied from 1 to 2.5 μm. X-ray powder diffraction showed that the films were amorphous, and X-ray photoelectron spectroscopy (XPS) revealed approximately 4 at.% N in the films. The ionic conductivity of Lipon was measured by electrochemical impedance spectroscopy to be approximately 1.02 μS/cm, which is consistent with the ionic conductivity of Lipon deposited by radio frequency magnetron sputtering of Li 3PO 4 targets in either mixed Ar–N 2 or pure N 2 atmosphere. Attempts to deposit Lipon in a N 2–O 2–Ar plasma resulted in the growth of Li 3PO 4 thin films. The XPS analysis shows no C and N atom peaks. Due to the high impedance of these films, reliable conductivity measurements could not be obtained for films grown in N 2–O 2–Ar plasma.