Laser-Induced Thermal Decomposition of Platinum Metallo-Organic Films
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LASER-INDUCED THERMAL DECOMPOSITION OF PLATINUM METALLO-ORGANIC
FILMS
2
A. Guptal, R.C. Sausal, and J.R. White 1 Yorktown Heights, 2 IBM Thomas J. Watson Research Center, IBM Systems Technology Division, Endicott, NY 13760
NY 10598
ABSTRACT The focused output from an argon ion laser (514 nm) has been used to pattern micron-size platinum features by decomposition of spun-on metallo-organic film on quartz substrate. The role of laser power and energy density on the thermal decomposition of the film is studied using pulsed and cw laser irradiation. Transient reflectivity has been used as a probe to study the reaction steps involved in the decomposition of the metallo-organic containing film. Preliminary results on the use of the platinum features as seed layer for electroless copper plating is presented.
INTRODUCTION The use of solid metallo-organic films in place of gas phase or liquid precursors for laser direct writing of metal features has been explored in a number of recent publications [1- 6] . Compatibility with traditional photolithographic techniques and process simplicity makes the use of metalloorganic films attractive for metallization in integrated circuit and packaging applications. Fisanick and co-workers [3 -5] have used a scanning cw argon ion laser to produce micron-size gold lines using gold resinates. The lines exhibited periodic structure under a broad range of experimental conditions. Mechanistic studies pointed to a thermal decomposition pathway in which the heat released in the exothermic reaction drives the reaction front ahead of the laser Their work also showed that large shrinkage of the gold irradiated area. metallo-organic films during decomposition limits the thickness of the lines to only a few thousand angstroms, and that the lines contain carbon and sulfur impurities. Resistivity measurements yielded a value of -1Ox bulk gold. Photochemical decomposition of metal resinates using an excimer laser has also been reported [6]. Although finer features can be patterned using UV photolysis compared to pyrolysis, the resulting films have a lot of impurities and are not electrically conducting. When metallo-organic resinates containing noble metal are thermally decomposed slowly in an oven, they result in formation of metal films with very little impurities, and have resistivity as low as films produced by vacuum deposition techniques [7] . This suggests that the rate of decomposition of the metallo-organic and the temperature distribution profile produced by the heat source are important in determining the purity and quality of the deposit. We have studied the photothermal decomposition of platinum resinate using an argon ion laser in order to probe the mechanism of decomposition during laser heating. We examine and discuss the role of laser power and energy density on the localized decomposition of the films, and present results from transient reflectivity measurements which provide information about the decomposition steps leading to formation of platinum. In addition, we report preli
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