CONTROLLED MECHANICAL ADHESION OF ELECTROLESS CU PATTERNS

The adhesion of electroless Cu to smooth ceramic substrates is poor. Controlled mechanical adhesion is accomplished by combining standard integrated-circuit processes with electroless Cu deposition. A Si wafer is covered with a SiO2 layer and a TiW pattern. To activate the TiW for electroless Cu, Pd nuclei are selectively deposited on the TiW via a displacement reaction in a PdCl2/HF solution. Simultaneously, the TiW pattern is underetched. Electroless Cu grows around the created TiW anchors only, thus clenching itself to the substrate. Good adherence of large structures can be obtained by dividing them into small lines or squares. Cu lines, 3 mum wide and 1 mum high have been deposited with good adhesion and selectivity