FTIR STUDIES OF THE ADSORPTION DESORPTION BEHAVIOR OF COPPER CHEMICAL-VAPOR-DEPOSITION PRECURSORS ON SILICA .2. 5,5-HEXAFLUOROACETYLACETONATO)(2-BUTYNE)COPPER(I)/

The reactions of (hfac)Cu(2-butyne) and 2-butyne on high-surface-area SiO2 with three different combinations and concentrations of reactive surface sites (highly dehydroxylated, I, containing isolated surface h ydroxyl groups and,strained four-membered siloxane rings;partially deh ydroxylated,II, containing isolated and hydrogen-bonded surface hydrox yl groups; and as-loaded, III, containing a higher concentration of is olated and hydrogen-bonded surface hydroxyl groups) have been investig ated by transmission Fourier transform infrared (FTIR) spectroscopy. T he silica surface was dosed at -130 and 25 degrees C, and the subseque nt temperature and time-dependent spectra were studied. The 2-butyne p hysisorbed all three SiO2 surfaces and molecularly desorbed on heating from -130 to -50 degrees C. Similar adsorption/desorption behavior wa s observed for (hfac)Cu(2-butyne) on all three surfaces. The (hfac)Cu( 2-butyne) compound physisorbed on the SiO2 surfaces at -130 degrees C with no observable hydrogen bonding to the surface hydroxyl groups or reaction with the strained siloxane sites. On heating the substrate, a change in the adsorbate spectrum was observed at approximately -50 de grees C, consistent with chemisorption of the adsorbate and loss of 2- butyne and the presence of adsorbed Cu(hfac)(2). The FTIR spectrum aft er dosing at 25 degrees C was virtually identical to that observed on dosing the same surfaces with Cu(hfac)(2) under identical conditions, On surface I, physisorption with isolated surface hydroxyl groups and reaction with strained siloxane rings was observed after dosing at 25 degrees C. On surfaces II and III, reaction with the hydrogen-bonded s urface hydroxyl groups was observed, based on the lack of restoration of the original integrated intensity of these peaks after complete rem oval of the adsorbate and the reaction byproducts. The substrate had t o be heated to about 400 degrees C for complete removal of the remaini ng adsorbed species derived from the hfac ligand. The interpretation t hat these data are consistent with the presence of Cu(hfac)(2) and can also be interpreted as consistent with the observed chemical vapor de position (CVD) of copper onto both copper and SiO2 surfaces using (hfa c)Cu(2-butyne) via the disproportionation reaction, 2(hfac)Cu-1(2-buty ne) --> Cu-O + Cu-II(hfac)(2) + 2(2-butyne).