Surface Science 409 (1998) 428–434 The surface chemistry of hexafluoroacetylacetone on clean and oxygen pre-covered Cu(210): a temperature-programmed desorption study H.L. Nigg, R.I. Masel * Department of Chemical Engineering, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA Received 7 November 1997; accepted for publication 27 January 1998 Abstract The surface chemistry of hexafluoroacetylacetone (Hhfac) on clean and oxygen pre-covered Cu(210) has been investigated by temperature-programmed desorption. On the clean surface, the Hhfac decomposes to form ten products desorbing in 13 desorption states, including a CF 3 COCOCF 3 fragment which could only form via Hhfac disproportionation or polymerization. In contrast, on the oxygen pre-covered (oxidized ) surface, there were only six fragments and much simpler chemistry. Some of the Hhfac is oxidized, while the remainder reacts to form Cu(hfac) 2 at 425 K. Our results show that low-temperature copper etching can occur on an oxidized Cu(210) surface. However, it is important to keep oxygen on the surface or else polymerization of the Hhfac, and subsequent contamination will occur. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Carboxylic acid; Chemical vapor; Chemical vapor deposition; Copper 1. Introduction Cu–bis(hfac) must decompose on the surface leav- ing only a metal film. On the other hand, in order Most VLSI manufacturers are now in the pro- to etch Cu, hfac and the etching product, cess of converting from Al to Cu in their devices Cu–bis(hfac), must remain intact through desorp- due to the lower resistivity and greater electromi- tion [18,19]. In either case, unfortunately, the hfac gration resistance of this transition metal. There ligand itself may decompose leading to impurities. are, presently, two main routes for depositing Cu This is a particular problem on barrier layers and in the fabrication of these integrated circuits: a sometimes results in film contamination. At pre- chemical vapor deposition (CVD) route and an sent there is little understanding of the mechanism electrochemical route. In the CVD route, a metal– of the contamination process. The objective of this inorganic or a metal–organic precursor such as paper is to examine the mechanism of the contami- Cu–bis(hfac) is used to deposit the copper [1–4]. nation process using temperature-programmed Fig. 1 shows the complete gas-phase structures of desorption ( TPD). Cu–bis(hfac) and hexafluoroacetylacetone [5,6]. In previous literature, Girolami et al. [7] have In order to deposit Cu onto a substrate, determined the adsorbate binding mode of hex- afluoroacetylacetone on a Cu(111) surface using * Corresponding author. IR spectroscopy. Their results indicated that hex- 0039-6028/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII: S0039-6028(98)00197-6