Laser-Induced Selective Copper Deposition on Polyimides and Semiconductors
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LASER-INDUCED SELECTIVE COPPER DEPOSITION ON POLYIMIDES AND SEMICONDUCTORS Seong-Don Hwang', S. S. Kher2 , J. T. Spencer' and P. A. Dowben' 'Department of Physics, Syracuse University, Syracuse, New York, 13244-1130 2 Department of Chemistry, Syracuse University, Syracuse, New York, 13244-4100
I. ABSTRACT It has been demonstrated that copper can be selectively deposited on a variety of substrates including Teflon (polytetrafluroethylene or PTFE), Kapton (polyimide resin), silicon and gallium arsnide from solution by photo-assisted initiated deposition. A copper containing solution was prepared from a mixture of copper(I) chloride (Cu2 C1,) and decaborane (BoH,,) in diethyl ether and/or THF (tetrahydrofuran). The copper films were fabricated by ultraviolet photolytic decomposition of copper chloride and polyhedral borane clusters. This liquid phase deposition has a gas-phase cluster analog that also results in copper deposition via pyrolysis. The approach of depositing metal thin films selectively by pholysis from solution is a novel and an underutilized approach to selective area deposition. lI. INTRODUCTION Laser-induced metal depositions on semiconductor surfaces have received much attention for possible use in electronic device fabrication. Also, metal/polyimide interfaces are important in microelectronic applications. Copper is one of the essential conducting metals in the microelectronic industry. Laser-induced copper deposition has recently been reported [1-14] . These investigations involve both UV laser photolysis [1-4] as well as laser pyrolysis [1,5-7] from the gas phase. A few laser assisted deposition studies of copper from solution have also been reported [8-14]. It has been demonstrated that copper (from solution of Cu2Cl, + BoH,,) can be deposited on Teflon (polytetrafluoroethylene or PTFE), Kapton (polyimide resin), silicon and gallium arsnide substrates using a pulsed nitrogen laser. In our work, copper was deposited on substrates via pulsed nitrogen laser irradiation of a copper solution in contact with the substrate surface. Copper deposition was found to occur via a UV photolytically induced reaction in solution between the substrate and the copper(I) chloride mediated by the borane cluster. The scheme is unique. Due primarily to its physical properties [15] decaborane (B,,H,,) was found to be the borane of choice. The postulated chemical reaction for deposition from this solution is:
hv Cu2C12 + B,,H
---------- > 2Cu(s) + B,0H,3C1 + HCl
340 0 C
(1)
The roll of the U.V. photolysis is that the extremely intense pulses can supply a sufficiently high density of incoming photons to initiate and sustain reaction (1). Since U.V. photolysis is not known as a thermal process, the localized light provides enough energy to deposit copper on plastic substrates such as Teflon and Kapton which have low thermal conductivities without heating the substrate. This may also be advantageous for certain applications where either high temperatures can result in for conventional alloying or otherwise
Mat. Res.
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