Abstract:
Ti interlayer and Cu thin film were deposited on alumina ceramic substrate by magnetron sputtering to improve the interfacial adhesion of copper film. Four-factor, three-level orthogonal experiments were carried out with sputtering power, pulse frequency, bias voltage and sputtering pressure as variables. The surface morphology, phase composition, electrical conductivity and adhesion performance of the films were characterized by SEM, EDS, XRD and four-point probe tester as well as scratch tester. The effects of process parameters on the surface quality, deposition rate and film adhesion of the Ti film were analyzed. The range analysis shows that the sputtering power exerts the most significant effect on the adhesion and deposition rate of Ti film, while the bias voltage mainly governs its surface quality. With the increase of sputtering power, the adhesion of Ti film increases continuously, whereas the deposition rate decreases first and then rises. Increasing pulse frequency improves the surface quality, yet reduces the deposition rate and adhesion. Moderate bias voltage facilitates particle diffusion, whereas excessive bias voltage induces etching damage. Elevated sputtering pressure weakens particle kinetic energy and degrades adhesion. Through weighted comprehensive score optimization, the optimal process parameters are determined as follows: sputtering power of 3 kW, pulse frequency of 90 kHz, bias voltage of 200 V, and sputtering pressure of 1 Pa. The performance tests reveal that the adhesion of directly deposited Cu film is only 9.1 N, while that of Ti-Cu composite film reaches 26.4 N. The composite film possesses a total thickness of 3.6 μm with dense microstructure, and its average resistivity is 1.5533×10
-4 Ω·cm, whose electrical conductivity meets the service requirements for electronic substrates. Benefiting from the matched thermal expansion coefficients between Ti and alumina, combined with the mechanical interlocking effect on the substrate surface, the interfacial thermal stress is effectively alleviated and the film-substrate bonding strength is improved. This work can provide a reference for the magnetron sputtering process of ceramic metallization.