Surface effects and adhesion of polysilazane and polyimide film bonding to copper redistribution layer with oxygen plasma treatment for advanced semiconductor packaging

• This study examines adhesion of PSZ and PI coatings in semiconductor interfaces. • Oxygen plasma treatment increases surface energy by introducing polar groups. • PI and PSZ coatings show increased roughness with curing temperature and plasma. • PSZ improves peeling strength by 240%, 119%, and 93% compared to PI at 200-300°C. • Plasma treatment enhances adhesion, but its effect varies with film thickness. This study investigates the peeling strength and adhesion of polysilazane (PSZ) and polyimide (PI) coatings deposited as interfaces between silicon wafers and sputtered titanium and copper films. The effects of various surface treatments, including different curing temperatures, oxygen plasma treatment durations, surface energy, roughness, and adhesion properties of the films, were examined. The results show that the contact angles of PI and PSZ coatings increase with curing temperature. However, water contact angles significantly decrease after oxygen plasma treatment, indicating that the plasma introduces polar functional groups, thereby enhancing surface energy. Extended oxygen plasma treatment further reduces the diiodomethane contact angle and increases surface energy. Atomic force microscopy reveals that the roughness of the PI film increases with temperature, while PSZ cured at 250°C exhibits the highest roughness. The roughness of both films increases with plasma treatment duration. The results of the 180° tape peeling test indicate that the adhesion of PI and PSZ cured at 200°C without oxygen treatment is optimal and decreases with higher temperatures. Using PSZ as the interface enhances peeling strength by 240%, 119%, and 93% compared to the PI interface when cured at 200°C, 250°C, and 300°C and subjected to plasma treatment for 5 minutes; therefore, PSZ can be one of the potential materials to replace with PI. The impact of plasma treatment on adhesion improvement was more pronounced with increasing film thickness. For thicknesses of 4.75 µm and 5.25 µm thick PSZ films, adhesion improvements are approximately 50% and 45%, respectively. Additionally, comparing surface energy and roughness measurements with adhesion results reveals a non-intuitive relationship: while surface energy and roughness increase with plasma treatment duration, adhesion does not necessarily follow this trend. Therefore, curing temperature and plasma treatment must be considered comprehensively for advanced semiconductor packaging.