Low Temperature Selective Area Chemical Vapor Deposition of Gold Films: Growth and Characterization
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LOW TEMPERATURE SELECTIVE AREA CHEMICAL VAPOR DEPOSITION OF GOLD FILMS: GROWTH AND CHARACTERIZATION
PAUL F. SEIDLER, STEVEN P. KOWALCZYK, MARK M. BANASZAK HOLL,
JOHN J. YURKAS, MAURICE H. NORCOTT, AND F. READ MCFEELY IBM Research Division, T. J. Watson Research Center, Yorktown Heights, NY 10598. ABSTRACT
Substrate-selective, low-temperature chemical vapor deposition of high quality gold films was obtained with the new precursor ethyl(trimethylphosphine)gold(l) in an ultrahigh vacuum reactor designed to handle wafers up to 3 inches in diameter. Growth behavior at temperatures as low as room temperature as well as substratc pre-cleaning procedures1 are presented. Activation energies of 35.1 ± 0.4 kcal mol' and 18.3 ± 0.7 kcal mol were found for growth of gold films on gold and copper substrates, respectively. INTRODUCTION
Gold is often used as a conductor in microelectronic applications because of its low resistivity, chemical inertness, and low tendency to electromigrate. A number of studies have examined chemical vapor deposition (CVD) of gold films from organogold compounds, particularly from acetylacetonato gold species.' In order to pattern these films, a variety of beam techniques can be used, such as photothermal decomposition using laser irradiation. Unfortunately, these relatively harsh methods of decomposition often incorporate impurities into the deposited films, making them less attractive for a 2 variety of applications. We recently discovered a method for thermal CVD of gold from the new precursor CHCH 2 AuP(CH 3) 3 which permits film growth at remarkably low temperatures as wellfas complete substrate selectivity without the use of lasers. 3 , 4 The process exploits the advantages inherent in chemical vapor deposition by carrying out the reaction under conditions of kinetic control, where some substrate materials are essentially inert, while others are highly reactive. In this paper we describe a CVD reactor which was built to investigate this process on substrates with diameters as large as 3 inches. Because substrate selectivity in this process depends on the precise identity of the reaction surface and its maintenance in an unadulterated condition, a key aspect of the reactor is its ultrahigh vacuum (UHV) base pressure. We also discuss the conditions for the initiation and continuation of growth at temperatures as low as room temperature, as well as growth rate behavior and film characterization. THE EXPERIMENTAL APPARATUS
Figure 1 shows a schematic diagram of the apparatus in which CVD of gold was performed. It consists of two UHV chambers. The first chamber serves as a load-lock for introduction of substrates and is pumped by a 60 L/s turbomolecular pump. The load-lock chamber is equippcd with an ASTeX Model CECR 0.25 Compact ECR Plasma Source for cleaning of substrates, e.g. for removal of native oxide from metals. A manifold provides gases for generation of various plasmas. The second chamber, the CVD reaction chamber, is pumped with a 60 L/s turbomolecular pump as well as a titanium sublim
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