Electroless copper deposition using glyoxylic acid as reducing agent for ultralarge scale integration metallization

Electroless copper from solutions that contain glyoxylic acid as reducing agent formed a conformal thin film compatible with very large scale integrated technology for integrated circuits and microelectromechanical systems applications. Glyoxylic acid is an alternative reducing agent that can replace formaldehyde for basic copper sulfate based solutions without compromising thin film properties and process capabilities. Electroless copper was deposited on a silicon surface activated with palladium as well as on an oxide film activated by a thin layer of copper or cobalt. The resistivity of thin copper film, thicker than 300 nm, deposited from glyoxylic based solution was 2.3-2.4 mu Omega cm as deposited, and 1.9-2.0 mu Omega cm after a 200 degrees C anneal for 30 min. Thinner film resistivity increased as film thickness decreased following a simple power low. Electroless copper was deposited from solution with glyoxylic acid into via contact of 0.2 mu m diam and up to 4:1 aspect ratio. The deposit was smooth and conformal. (C) 2000 The Electrochemical Society. S1099-0062(99)12-007-8. All rights reserved.