Chemical Vapor Deposition of Gold
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CHEMICAL VAPOR DEPOSITION OF GOLD CARL E. LARSON, THOMAS H. BAUM, and ROBERT L. JACKSON, IBM Almaden Research Center, San Jose California 95120 ABSTRACT Chemical vapor deposition of gold from dimethyl-2,4-pentandionato gold (III) and two fluorinated derivatives is reported. At substrate temperatures of 200-300 0C, high purity gold films were obtained on Si0 2 and Si substrates. Films with resistivities down to 1.3 times that of bulk gold were obtained at deposition temperatures of -200 0 C, where films with very small grain size could be deposited. INTRODUCTION Chemical vapor deposition (CVD) of metals has been extensively studied recently due to the potential of this technique for increasing the density of metallization layers on integrated circuits [1-5]. Since CVD is in principle an isotropic deposition process, better coverage of sharp steps can be achieved than by sputtering or evaporation. As a result, vias interconnecting metallization layers on integrated circuits can have 900 sidewalls, rather than sloped sidewalls, reducing the area that each via occupies. CVD of tungsten from WF 6 has been the focus of much of the work in metal CVD [1,2], due to the selectivity of the process for deposition onto Si vs. Si0 2 and because WF 6 is one of the few, readily available, gaseous CVD metal precursors. It is important, however, to continue searching for new CVD processes and for new precursors capable of producing lower resistivity metal films, since pure tungsten has an inherent resistivity higher than that of other metals, e.g. aluminum [3] and gold [61, that have been used in metallization layers of integrated circuits. We have previously reported laser-induced chemical vapor deposition (photothermal) of high purity gold onto various substrates from dimethyl2,4-pentandionato gold (III) [7-91. We now report that high-purity gold films can also be deposited by CVD from this complex as well as from two fluorinated derivatives: dimethyl-(1,1,1-trifluoro-2,4-pentandionato) gold (III) and dimethyl(1,1,1,5,5,5-hexafluoro-2,4-pentandionato) gold (Ill) [9]. We discuss the conditions of deposition and the quality of the gold films obtained as well as the properties of the organogold precursors. EXPERIMENTAL Dimethyl-(2,4-pentandionato) gold (III), Me2Au(acac), was prepared by the method of Brain and Gibson [10]. Diriethyl-(1,1,1-trifluoro-2,4-pentandionato) gold (III) and dimethyl-(1,1,1,5,5,5-hexafluoro-2,4-pentandionato) gold (III), Me2Au(tfac) and Me2Au(hfac) respect.vely, were prepared by an analogous route. CVD of gold from each complex was carried out in a stainless steel vacuum chamber. The chamber was pumped by a turbomolecular pump to a base pressure of < 10-6 torr prior to beginning each deposition run. A flow of argon carrier gas through a Pyrex tube containing a small quantity of one of the gold compounds is used to deliver the precursor vapor into the chamber. The tube was maintained at room temperature in all experiments. The chamber pressure was measured during a deposition run by a capacitance manometer. C
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