LOW-TEMPERATURE BONDING OF CU ON SI3N4 USING LASER-ABLATION PROCESS

Low temperature bonding of a Cu specimen on a Si3N4 plate was examined. Si3N4 plates were irradiated with KrF excimer laser beam in vacuum. The energy density of laser was 0.3 J/mm(2). At the laser irradiation area Si3N4 was decomposed into Si and N-2 and then thin Si layer was formed on Si3N4. XPS analysis revealed that the thickness of the thin Si layer was 0.04 mu m. An Ar ion sputtered Cu specimen was pressed on a Si3N4 plate through thin Si layer at temperatures of 560 similar to 630 K for 3.6 ks in vacuum. The bonding strength was 100-200 MPa and the Si layer was essential for low temperature bonding of Cu and Si3N4.