The Decomposition Chemistry of an AlN Precursor Bis-Dimethylaluminum Deutero-Amide, [(CH 3 ) 2 AlND 2 ] 3 , as Revealed
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THE DECOMPOSITION CHEMISTRY OF AN ALN PRECURSOR BIS-DIMETHYLALUMINUM DEUTERO-AMIDE, [(CH 3)2 AIND2]3, AS REVEALED BY TIME-OF-FLIGHT MOLECULAR BEAM MASS SPECTROMETRY CARMELA C. AMATO, JOHN B. HUDSON**, AND LEONARD V. INTERRANTE* *Chemistry Dept., Rensselaer Polytechnic Institute, Troy, NY 12180 "**MaterialsEngineering Dept. , Rensselaer Polytechnic Institute, Troy, NY 12180
Abstract A molecular beam mass spectrometer coupled to the inlet portion of a hot-wall CVD reactor has been used to measure the time-of-flight (TOF) distribution of molecules sampled from the reactor. The molecular weights of the species in the reactor can be determined from test TOF distributions. This technique has been used to identify the gas phase species present in a hot-wall reactor during the CVD of AIN using bis-dimethylaluminum deutero-amide,[(CH 3 )2 AIND213 (I), as the precursor. Evidence has been found for: deuterated methane, CH 3 D, trimeric form of the
precursor I, and its dimeric form. TOF evidence also supports the presence of an oligomer of I with a pentameric structure, as well as a number of substituted versions of trimer and dimer.
Mechanisms have been formulated that explain methane elimination from the precursor as well as the formation of all species observed. Introduction The cyclic organoaluminum compound, tris-dimethylaluminum amide, [(CH 3 )2 AINH 2] 3 , has been demonstrated to be an effective precursor to AIN.! In order to understand how the molecular structure and chemical properties of such molecules influence the deposition process and the properties of the final product, it is necessary to understand the chemical reactions occurring inside the CVD reactor. This in turn may permit to modifications in the precursor structure or deposition parameters in order to obtain control of the chemical and morphological properties of the product. Recently the area of chemical vapor deposition has moved to a sophisticated development based on understanding the growth mechanisms of deposited materials. Much of this work has concentrated on elucidating surface chemistry of precursor molecules. However, gas phase reactions which generate molecules that impinge upon the growth surface may be important. In order to completely understand any CVD process, it is necessary to characterize the gas phase chemistry as well as the surface chemistry. We describe here our efforts at identifying the gas phase species present in a hot-wall CVD reactor during the chemical vapor deposition of AIN using the deuterated analogue of bisdimethylaluminum amide, [(CH 3 )2 AIND 2 ]3 (I) as the precursor. Previous efforts have involved obtaining the mass spectrum of the gas flow emerging from the reactor at various temperatures for both [(CH 3 )2 AIND 2 ]3 and [(CH 3 )2 AINH 2 ]3. 2. 3 in this work. It was not possible to determine which ion signals in the mass spectrum resulted from new products and which ion signals were a result of fragmentation of the precursor in the ion source due to the complexity of the decomposition process.. Thus, a molecul
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