- Conference date: Apr 1993
- Location: Knoxville, Tennessee (USA)
Pulsed‐laser irradiation of wide bandgap ceramic substrates, using photons with sub‐bandgap energies, activates the ceramic surface for subsequent electroless copper deposition. The copper deposit is confined within the irradiated region when the substrate is subsequently immersed in an electroless copper bath. However, a high laser fluence (typically several J/cm2) and repeated laser shots are needed to obtain uniform copper coverage by this direct‐irradiation process. In contrast, by first applying an evaporated SiO x film (with x∼1), laser ablation at quite low energy density (∼0.5 J/cm2) results in re‐deposition on the ceramic substrate of material that is catalytic for subsequent electroless copper deposition. Experiments indicate that the re‐deposited material is silicon, on which copper nucleates. Using an SiO x film on a laser‐transparent substrate, quite fine (∼12 μm) copper lines can be formed at the boundary of the region that is laser‐etched in SiO x . Using SiO x with an absorbing (polycrystalline) ceramic substrate, more‐or‐less uniform activation and subsequent copper deposition are obtained. In the later case, interactions with the ceramic substrate also may be important for uniform deposition.
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