Uv Excimer Laser Induced Prenucleation of Surfaces from Spin-on Films Followed by Electroless Metallization
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UV EXCIMER LASER INDUCED PRENUCLEATION OF SURFACES FROM SPIN-ON FILMS FOLLOWED BY ELECTROLESS METALLIZATION
Hilmar Esrom, Georg Wahl and Michael Stuke* Asea Brown Boveri, CRH, D-6900 Heidelberg, FRG *Max-Planck-Institut f. biophys. Chemie, D-3400 Gbttingen,
FRG
ABSTRACT UV excimer laser light-induced prenucleation of various surfaces from spin-on films in air is described. Good results were obtained using palladium acetate on substrate materials ranging from ceramics to polymers and even paper. Virtually any surface material can be prenucleated in this way. The Pd-prenucleated planar and curved surfaces can be metallized by a vast variety of metals using electroless plating solutions (Cu, Ni, Au, Pt, Co, Sn, and even alloys). Results are described in detail for copper from a standard electroless solution (Doduco or Shipley). Contact metallization through via holes using this process was achieved with excellent contact properties. INTRODUCTION In recent years, there has been considerable work on direct deposition of materials by laser driven processes. These methods usually involve laser-induced pyrolytic and photolytic deposition of films from gas phase, liquids and thin metallorganic films[l]. Characteristically of all these direct deposition methods is in most cases the low deposition rate, relative high impurities in the films and in individual cases the self-limiting of film thickness[2]. To overcome these problems, we developed a two-step hybrid process. The first step is the UV photo-induced deposition and patterning of a thin catalyst on substrate surfaces with excimer lasers followed by the second step, the usage of the activated surfaces for the selective electroless metal deposition. The prenucleation of substrate surfaces can be achieved by laser decomposition of thin metallorganic or inorganic films on non active surfaces[3]. The decomposition process in the solid phase has similarities to chemical vapor deposition (CVD) processes, however with the advantages of increased safety and ease of handling. The decomposition of the films can be performed in air, and no specialized vacuum equipments are needed. Recently, R.C. Sausa et al.[4] reported the pyrolytic Ar+ laser decomposition of platinum metallorganic films and H.S. Cole et al.[5] reported the photolytic Ar+ laser decomposition of palladium acetate films for electroless copper plating. In this paper, we report parts of our investigations[6] concerning the deposition of structured palladium catalysts by means of excimer laser photolytic decomposition of thin palladium acetate films on rough ceramic surfaces for electroless copper plating.
Mat. Res. Soc. Symp. Proc. Vol. 131. '1989 Materials Research Society
582
EXPERIMENT A commercial excimer laser (Lambda Physik, model EMG 103) was used for the UV irradiation of the spin-on Pd acetate films. The intensity distribution across the rectangular beam profile (20x6 mm2 ) was inhomogeneous and was therefore apertured with slits to minimize the spatial intensity inhomogenity. The laser pulse energy w
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