Mechanistic, surface chemistry, and growth studies of novel precursors for aluminum nitride thin films.

摘要

One of the primary techniques for thin film deposition used in the fabrication of microelectronic and optoelectronic devices is chemical vapor deposition (CVD). In CVD, nutrient elements for film growth are transported in the gas phase to the growth surface where a complex series of chemical reactions occurs. The selection of the chemicals and process parameters determines the properties of the film that will be obtained.;Aluminum nitride (AlN) is a direct wide bandgap material with excellent physical properties making it useful for a wide variety of solid state device applications. This research focused on (1) screening novel chemicals as viable sources for vapor phase deposition of AlN by investigating their adsorption and decomposition behavior on technologically important substrates, (2) developing growth strategies from these results, (3) implementing the growth strategies, and (4) characterizing the thin films that were deposited.;Surface chemistry investigations of four potential AlN CVD sources were conducted. The sources were bis[amidobis(trimethylsilyl)aluminum] (BABTMSA), 1,1-dimethylhydrazine (DMHy), ammonia (NH3), and dimethylethylamine alane (DMEAA). BABTMSA, a potential single source precursor, did not have adsorption properties that allowed for facile decomposition to AlN. DMHy, NH3, and DMEAA all showed adsorption and decomposition behavior on Si(100) under certain conditions that was promising for AIN deposition.;A growth strategy was developed for the deposition of AlN thin films at low temperature with minimal impurities employing a temperature modulated atomic layer growth (ALG) process using DMHy and DMEAA precursors. The growth strategy was implemented and investigated. The deposition proceeded primarily through the dehydrogenation of AlHyNHx species where regeneration of these species occurred in each cycle. This was also found to be the primary mechanism for ALG of AlN using DMEAA and NH3 and similar processing conditions.;The low temperature growth of AlN on oxidized Si(100) using DMHy and DMEAA was also conducted in a high vacuum CVD reactor (chemical beam reactor). At a growth temperature of 723 K, AlN thin films with a preferred {00.1} orientation were deposited. XPS analysis of the films indicated low carbon contamination (<4 atomic percent), and an index of refraction of 2.03 was measured by ellipsometry.