In Situ XPS Studies of the Deposition of TiN_xC_y Films from Tetrakis(dimethylamido)titanium(IV) and Bis[N,N′-bis(tert-butyl)ethylenediamido]titanium(IV)

摘要

The decreasing feature size of integrated circuits requires new low-temperature, chlorine-free CVD processes for titanium nitride (TiN) diffusion barriers. The thermal deposition of TiN from organometallic precursors, e.g., tetrakis(dimethylamido)titanium (TMT), results in a high carbon contamination of the films. Using in situ X-ray photoelectron spectroscopy (XPS), we show that the contamination of TiN films deposited on silicon consists mostly of hydrocarbon inclusions and a smaller amount of titanium carbide (TiC). From these results we confirm and extend the mechanism for the thermolysis reaction of TMT proposed by other authors, showing the formation of TiC as being inherent to this precursor. The reaction of TMT with ammonia decreases the amount of carbon contamination, yet the spontaneous reaction in the gas phase results in a poor step coverage. On the basis of these results, we suggest in agreement with other authors that at small NH_3/TMT ratios and very low pressures the reaction proceeds via a polymeric transamination at the substrate surface. The importance of gas-phase reaction increases at higher NH_3/TMT ratios. Activated hydrogen from a plasma afterglow source significantly reduces the hydrocarbon contamination leaving only a small amount of hydrocarbon and carbidic carbon in the films. It is shown that at least a part of the aliphatic carbon found in the films originates from the adsorption and subsequent decomposition of the product amines at the TiN surface. Attempts to avoid the TiC formation were made by using the precursor bis[N,N′-bis(tert-butyl)-ethylenediamido]titanium (BTET).