THE SPRAY DEPOSITION OF TRANSITION METAL NITRIDE THIN FILMS USING ALCOHOL BASED PRECURSOR SOLUTIONS K.S. WEIL AND P.N. KUMTA Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 ABSTRACT A new alcohol solution based approach has been developed for preparing transition metal nitride thin films and coatings. In this technique, the metal of interest is dissolved as a chloride in acetonitrile, then chelated with triethanolamine to form a highly viscous solution which settles out of the solvent phase. The acetonitrile is then evaporated off and the remaining thick liquid precursor is easily diluted with water or methanol, yielding a semi- viscous liquid which can be used directly to coat various substrates. When heat treated under the appropriate conditions in ammonia, the precursor coating transforms to yield the corresponding nitride. This approach is currently being considered for preparing nitride- based thin film electrical components and has been successfully used thus far to spray deposit TaN and NbN nitride films onto silicon substrates. Results of the preliminary study on these two nitride films are discussed in this paper. INTRODUCTION Transition metal nitride materials, such as TiN, ZrN, and Fe4N are important in a wide range of applications including wear and corrosion resistant coatings, high-temperature structural components, and magnetic storage devices. However, the most immediate use of transition metal nitrides may depend on their electrical properties. Thin tantalum nitride and niobium nitride films are of particular interest. Tantalum nitride films are used extensively in microelectronic applications such as in resistors and capacitors because of their low thermal coefficients of resistance and stable resistance values under long term operating conditions (1). The 8 phase of NbN is a type II superconductor with a useful T, of 17.3 K and high breakdown current value, and it has found important applications in devices such as dc- superconducting quantum interference devices, Josephson junctions, and switches for pulsed power applications (2). In recent years, a number of synthesis techniques have been developed for preparing transition metal nitride coatings and films. These include: reaction sputtering (3), laser ablation (4), the ammonolysis of sol-gel derived spin coated films (5), and thermal decomposition of [(CH 3 ) 3 Si] 2 NH based compounds (6). Synthetic approaches based on liquid precursor techniques may offer several advantages over line of sight physical film deposition methods, such as sputtering, including the opportunity to better control the stoichiometry and microstructure of nitride thin films. We have recently demonstrated a new solution based approach which offers the potential to synthesize a number of ternary transition metal nitride powders (7,8). The focus of the present study is to demonstrate the utility of this approach in preparing nitride thin films for electronic device applications. The process involves dissolving a metal chloride in acetonitrile and chelating the metal species with an alkanolamine complexing agent to form a liquid precursor. Depending on the choice of the alkanolamine, this liquid can be further modified to prepare precursors for generating a nitride powder or coating. Precursors for the powders, for example, are prepared using a low molecular weight bidentate chelating agent, such as ethanolamine, followed by subsequent hydrolysis to form a metallo-organic hydroxide precipitate which can be filtered and dried. Thin film precursors, on the other hand, can be prepared by chelating the transition metal chloride species with a higher molecular weight alkanolamine, such as triethanolamine. The 227 Mat. Res. Soc. Symp. Proc. Vol. 495 © 1998 Materials Research Society