Issues involved in the atomic layer deposition of metals

Auger Electron Spectroscopy (AES) was used to study the nucleation and growth of tungsten on aluminum oxide surfaces. Tungsten metal was deposited using Atomic Layer Deposition (ALD) techniques. ALD uses sequential surface reactions to deposit material with atomic layer control. W ALD is performed using sequential exposures of WF₆ and Si₂H₆. The step-wise nature of W ALD allows nucleation studies to be performed by analyzing the W surface concentration after each ALD reaction. Nucleation and growth regions can be identified by quantifying the AES signal intensities from both the W surface and the Al₂O₃ substrate. W nucleation occurred in 3 ALD reaction cycles. The AES results yielded a nucleation rate of 1.0 Å/ALD cycle and a growth rate of ≈3 Å/ALD cycle. AES studies also explored the nucleation and growth of Al₂O₃ on W. Al₂O₃ nucleated in 1 ALD cycle giving a nucleation rate of 3.5 Å/ALD cycle and a subsequent growth rate of 1.0 Å/ALD cycle.; Mass spectrometry was then used to study the ALD reaction chemistry of tungsten deposition. Because of the step-wise nature of the W ALD chemistry, each W ALD reaction could be studied independently. The gaseous mass products were identified from both the WF₆ and Si₂H₆ reactions. H₂, HF and SiF₄ mass products were observed for the WF₆ reaction. The Si₂H₆ reaction displayed a room temperature reaction and a 200°C reaction. Products from the room temperature Si₂H₆ reaction were H₂ and SiF₃H. The reaction at 200°C yielded only H₂ as a reaction product. H₂ desorption from the surface contributes to the 200°C Si₂H₆ reaction. AES was used to confirm that the gas phase reaction products are correlated with a change in the surface species.; Atomic hydrogen reduction of metal halides and oganometallic compounds provides another method for depositing metals with atomic layer control. The quantity of atomic hydrogen necessary to perform this chemistry is critical to the metal ALD process. A thermocouple probe was constructed to measure atomic hydrogen in a molecular hydrogen flow environment. Atomic hydrogen recombines to form H₂ on different surfaces at different rates. The rate of this recombination was measured for stainless steel, aluminum, pyrex, and quartz. Knowing the hydrogen recombination rate of various materials allowed for an atomic hydrogen assisted ALD flow reactor to be constructed.; An atomic hydrogen assisted ALD flow reactor was constructed and used to deposit titanium and tin metals. The metal growth was monitored using quartz crystal microbalance. The metal films were characterized ex situ using x-ray diffraction and stylus profilometry.