Copper film prepared from copper fine particle paste by laser sintering at room temperature: Influences of sintering atmosphere on the morphology and resistivity

Laser sintering method was applied for copper fine particle paste to generate electrically conductive copper film. The one-step sintering of the copper fine particle coating films at room temperature was carried out by scanning irradiation of a line-shaped laser beam under various atmospheric conditions. The laser sintering of the copper fine particle coating film under a hydrogen/argon (4/96) gas mixture flow gave a copper film with a low resistivity of 1.05 × 10^-5Ωcm. The scanning electron microscope (SEM) image of the laser sintered film showed the necking among copper fine particles. The film laser-sintered in air was insulator which showed the Raman band assigned to Cu₂O. The laser sintering of the copper fine particle coating film under argon gas flow gave also copper films with resistivities of the order of 10^-5Ωcm, which depended on the flow rate of argon gas. On the other hand, the film sintered by conventional heat treatment at 300 °C under argon gas flow showed a high resistivity. The formation of a copper wiring with several micrometers resolution was achieved by laser direct writing using copper fine particle with the size larger than 100nm. The advantages of the laser sintering in the preparation of a conductive film from copper fine particle paste were demonstrated.