MECHANISM OF NUCLEATION AND ATOMIC LAYER GROWTH OF ALN ON SI

We have studied by X-ray photoelectron spectroscopy the adsorption and decomposition of trimethylaluminum (TMA) on Si(100), the low-temperature formation of AlN from pyrolysis of TMA and NH3, and have demonstrated a mechanism for atomic layer growth of AlN at 600 K. TMA adsorbs dissociatively to Si at temperatures above 300 K. At < 650 K adsorption is self-limiting at < 1 monolayer, with most carbon remaining in the form of CH3. At higher temperatures, decomposition of the TMA is rapid, and continuous deposition is observed with production of carbides as the primary product. Coadsorption of TMA and NH3 at room temperature leads to formation of Al-N covalent bonding as well as a surface adduct species, Al:N, which is converted quantitatively to Al-N at higher temperature. At substrate temperatures < 550 K, coadsorption of TMA and NH3 is self-limiting at less than a monolayer, while above this temperature reaction to form AlN is rapid and continuous deposition is observed. Self-limiting adsorption of TMA at < 650 K and rapid, site-selective reaction with NH3 to from AlN at > 550 K satisfy the conditions for atomic layer growth of AlN at 600 K using sequential exposures of TMA and NH3. The chemical nature of the interfacial and growth surface are discussed.