|AVS 55th International Symposium & Exhibition|
|Plasma Science and Technology||Thursday Sessions|
|Session:||Plasma Deposition and Plasma Enhanced Atomic Layer Deposition and Etching|
|Presenter:||N.G. Kubala, Colorado School of Mines|
|Authors:||N.G. Kubala, Colorado School of Mines
C.A. Wolden, Colorado School of Mines
|Correspondent:||Click to Email|
In this presentation we describe the self-limiting deposition (~ Å/pulse) of titanium dioxide by pulsed plasma-enhanced chemical vapor deposition (PECVD) at low temperature (< 150ºC). In this process the titanium tetrachloride (TiCl4) and oxygen are mixed and delivered simultaneously in a remote PECVD configuration. The as-deposited films were characterized by spectroscopic ellipsometry, Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), and dielectric performance. In addition, the plasma chemistry in this system was characterized using quadrupole mass spectrometry (QMS) and optical emission spectroscopy (OES). QMS measurements confirmed that TiCl4 and O2 are inert in this system in the absence of plasma. During continuous wave plasma operation TiCl4 is completely consumed, no deposition is observed, and the main byproducts are Cl/Cl2. While no film growth is observed with the plasma on or off, self-limiting deposition was readily obtained by pulsing the plasma at low frequency (~1 Hz). The deposition kinetics and film quality were evaluated as a function of precursor exposure, plasma power, substrate temperature, and pulse parameters. The deposition rate per pulse scaled with the degree of precursor exposure during the plasma off step. Through appropriate control of the TiCl4 concentration and pulse duration, the depositing rate may be adjusted over a narrow range (0.6 – 1.3 Å/pulse). High refractive indices were obtained, scaling with exposure and plasma power over a range of 2.3 to 2.6 at 580 nm. The deposition rate also decreased with plasma power, and OES was used to highlight the role of atomic oxygen in this process. XPS analysis showed that the titanium was fully oxidized. At low plasma power a small amount of Cl contamination was observed, however no Cl was detected in films deposited at higher powers. FTIR characterization of these amorphous films display broad absorption features at low wavenumbers that are distinct from the sharp peaks associated with the crystalline phases of TiO2. A comprehensive analysis of dielectric performance is underway and will be reported at the symposium.