| With the continued miniaturization of thin film devices, growth techniques are required that deposit conformal films with atomic layer control. In this thesis, atomic layer deposition (ALD) techniques were developed to achieve conformal and atomic layer controlled film growth. Reactors were constructed and optimized for testing potential precursors and deposition processes. Several methods of volatilization and delivery into the reactor were studied and optimized. All of the ALD methods are based on sequential, self-limiting surface reactions. The research included developing new chemistries and new precursors for ALD, optimizing and characterizing film growth and evaluating properties of ALD films. This thesis is based on experimental work carried out during the years 1999–2002 at Harvard. It will first review ALD in general. Then, the growth and properties of films of metal oxides and nitrides will be described. The self-limiting film growth mechanism in ALD ensures excellent film conformality and uniformity over large areas, and atomic level composition and thickness control. A variety of electronic films have been deposited by ALD. In this thesis, ALD deposition and material characterization of two groups of films will be examined: (i) insulating films and (ii) conductive films. In every case atomic layer controlled growth was shown to occur. In the present work, the deposition of silver-colored, conductive tungsten nitride barrier films by ALD using a novel precursor, bis(tert-butylimido)bis(dimethylamido)tungsten, (t-BuN)2(Me2N)2W, and ammonia at low substrate temperatures (250–350°C) is reported. The basic bulk properties of these films were investigated, as well as their performance as a barrier to the diffusion of copper.; The thesis also deals with a new type of ALD reaction, using trimethylaluminum and tris(tert-butoxy)silanol, that deposits dozens of monolayers in cycles less than half a minute long, resulting in a deposition rate more than 100 times faster than previously known ALD reactions for silica nanolaminates. In addition, new deposition processes for metal silicates for hafnium, zirconium, lanthanum and yttrium from metal alkylamides and tris(alkoxy)silanols are reported.; Using metal alkylamide precursors and ammonia, films of pure insulating nitrides of hafnium and zirconium were prepared and characterized. The ALD of thin films of Hf3N4 and Zr3N4 using homoleptic tetrakis(dialkylamido)metal(IV) complexes and ammonia at low substrate temperatures (150–250°C) is reported. Hafnium and zirconium oxynitride (HfOxNy and ZrOxN y) dielectrics were also made by ALD using, homoleptic tetrakis(dimethylamido)metal(IV), water and ammonia at low substrate temperatures (200–250°C). The basic bulk properties of these films were investigated, as well as their electrical properties for the application of these materials as gate dielectrics. |
