Laser-Induced Metal Deposition From The Liquid Phase

A process is described to selectively deposit metal tracks from ammoniacal metal salt solutions. The substrate is locally heated using a 5W CW Ar+ laser. At the irradiated area, the NH3 is thermally decomposed. The liberated electrons reduce the metal ions to the corresponding metal. Simultaneously, the focused laser beam induces local boiling phenomena, leading to a stationary jet flow with extremely efficient replenishment of reactants and correspondingly high deposition rates. In this way, Pd tracks 20 μm wide and 10 μm high have been grown at a lateral rate of 500μm s-1. At present, the process is used to rewire integrated circuits, to facilitate testing and failure analysis.