Chemical Vapor Deposition Precursor Chemistry. 2. Formation of Pure Aluminum, Alumina, and Aluminum Boride thin Filmsfrom Boron-Containing Precursor Compounds by Chemical Vapor Deposition

Thin films of pure aluminum, aluminum boride, and aluminum oxide have been prepared from the chemical vapor deposition (CVD) of volatile boron-containing precursor compounds. Chemical vapor depositions on a variety of amorphous and monolithic substrates have been explored for the source compounds Al(BH₄)₃,1, and AlH2(BH₄)-N(CH₃)3, 2. The formation of pure polycrystalline aluminum thin films from 2 was accomplished at 100 °C without substrate pretreatment, and at 25 °C with the substrate briefly pretreated with TiCl₄. Room-temperature depositions of mirrorlike pure polycrystalline aluminum films were demonstrated on thermally sensitive substrates. Aluminum boride films were similarly prepared from compound 1 at 300 °C. Depositions with 1 in a partial pressure of oxygen yielded pure polycrystalline alumina (AI₅O₃) films. All films were characterized by XES, AES, SEM, XRD, and resistivity measurements. Each film was shown by AES to be compositionally uniform in the bulk sample with only very shallow surface contaminations of oxygen and carbon from atmospheric exposure. Film thicknesses ranging from 500 Å to 2 μm were readily prepared by controlling the precursor flow rate into the cell, the substrate temperature, the precursor exposure times to the substrate, and the nature of the substrate pretreatment. The two source compounds were, in general, relatively thermally stable, volatile, air-sensitive liquids, thus providing excellent precursor properties for chemical vapor deposition experiments.