AVS 54th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS1+TF-TuM

Paper PS1+TF-TuM12
Self-Limiting Growth of Aluminum Oxide by Pulsed Plasma-Enhanced Chemical Vapor Deposition

Tuesday, October 16, 2007, 11:40 am, Room 606

Session: Plasma Enhanced Atomic Layer Deposition and Plasma Deposition
Presenter: S.F. Szymanski, Colorado School of Mines
Authors: S.F. Szymanski, Colorado School of Mines
M.T. Seman, Colorado School of Mines
D. Richards, Colorado School of Mines
C.A. Wolden, Colorado School of Mines
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In this presentation we describe the self-limiting deposition (~ Å/pulse) of aluminum oxide by pulsed plasma-enhanced chemical vapor deposition (PECVD). In this process the trimethyl aluminum (TMA, Al(CH3)3) and oxygen are mixed and delivered simultaneously in a remote PECVD configuration. Deposited films were characterized by spectroscopic ellipsometry, Fourier transform infrared spectroscopy, and dielectric performance. In addition, the plasma and gas-phase chemistry in this system were characterized using optical emission spectroscopy (OES) and quadrupole mass spectrometry (QMS), respectively. The chemistry and deposition kinetics were quantified as a function of TMA concentration, 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 TMA concentration and pulse duration, the depositing rate may be readily adjusted over a broad range (1 - 10 Å/pulse). The deposition rate also decreases with plasma power, and OES is used to highlight the role of atomic oxygen in this process. The chemistry was quantified under steady-state operation using the QMS. It is shown that O2 and TMA are unreactive with the plasma off. In contrast, TMA is completely consumed during plasma operation. Combustion of the TMA precursor is complete, yielding a mixture of CO, CO2, H2O, and H2. Transient experiments show how TMA adsorbed on the walls of the chamber can impact both deposition rate and quality. The deposition rate was found to be independent of temperature for Ts > 100 °C. At lower temperatures the deposition rate per pulse increased, but film quality was degraded. Using a combination of ex situ film characterization and in situ diagnostics it is suggested that this behavior may be attributed to thermal chemistry occurring between TMA supplied during the off step with H2O produced during the plasma on step. This reaction adversely effects film quality, but its effects are mitigated when the both reactor walls and substrate are maintained at temperatures > 100 °C.