Fine Line Patterning By Focused Ion Beam Induced Decomposition of Palladium Acetate Films
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FINE LINE PATTERNING BY FOCUSED ION BEAM INDUCED DECOMPOSITION OF PALLADIUM ACETATE FILMS
L. R. Harriott, K. D. Cummings, M. E. Gross, W. L. Brown, J. Linnros, and H. 0. Funsten* AT&T Bell Laboratories, Murray Hill, NJ 07974
ABSTRACT Fine conducting features have been produced on Si and SiO 2 substrates by irradiation of spin-on palladium acetate, [Pd(O 2CCH 3) 2] 3 films with a submicron focused ion beam. The exposures were made with a 20 keV GaC,focused to a 02 micrometer spot. Electrical conductivity measuremnents were made on the resultant features as a function of ion dose for linewidths of one and ten micrometers. The sheet conductivity in the 4two cases2 was comparable and increased dramatically in the dose range between 2x101 and 5x101 ions/cm . The conductivity of the exposed lines was further increased after heating in a hydrogen atmosphere. Measurements of carbon and oxygen content indicate that even at the highest ion doses a significant amount of organic material remains. Results are compared to those for 2 MeV He* and Ne* broad beam exposures. Potential applications are also discussed. INTRODUC'ION Decompo•ition of metallo-organic [1] compoinis has been studied using irradiation from lasers [2], electron beams [3], and broad area ion beams [4,5]. We present a direct-write method of patterning palladium metal using a submicron focused gallium ion beam. The palladium acetate precursor is decomposed by the energy loss of the ion beam in non-thermal processes. This technique is capable of high resolution limited only by the diameter Cf the ion beam. No periodic structures are observed as with laser exposures. Palladium metal features are produced only where the precursor has been exposed to the ions. Palladium acetate is a unique material in that it can be spin-coated from solution to form a uniform, apparently anxrphous solid film. Palladium itself is of interest for its metallic conductivity, optical opacity and ability to catalyze the electroless plating of copper. In this paper we present results of the non-thermal decomposition of palladium acetate with a focused gallium ion beam as well as a comparison to exposures of the films to 2 MeV He* and Ne' broad area beams. Sheet resistance as well as carbon and oxygen content have been measured as a function of fluence for each ion type. EXPERIMENTAL Samples were produced by spin-coating palladium acetate in chloroform solution onto silicon, oxidized silicon or polished beryllium substrates. Film thickness is controlled by solution cmcentration and spin speed. Patterned films are developed in chloroform to rermoe unexposed material. The focused ion beam system used for the gallium eaposures was dewloped primarily for micrornachining applications such as mask repair and has been described elsewhere [6]. Ions from a are accelerated to 20 KeV and focused to a 02 inn diameter spot and liquid metal gallium source current density of 1 A/cm2 by an electrostatic lens. The beam may be deflected under computer control 0 Present Address: School of Engine ing and Ap
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