Dual damascene advanced interconnects: new copper seed layer enhancement process metrology using ion chromatography
Physical vapor deposition (PVD) copper seeding and subsequent fill by electroplating have become the most attractive technique for the implementation of copper metallization. However, a PVD seed layer provided as a continuous thin film with low resistivity to carry current for the subsequent electroplating process might have limitations of poor step coverage, rough morphology, discontinuity, overhang, and coverage asymmetry. Hence, it is of importance to extend the capability of PVD seed-layer deposition process for future high performance devices. An ion chromatography (IC) method is shown to be capable for electrochemical copper seed layer enhancement (SLE) process metrology. Composition dynamics of fresh and aged SLE bath solutions with an electroplating time up to 66.5min are measured and analyzed with an IC system. The solution dynamics are found to be significant for electroplated copper film properties, the resistivity and roughness, which are found to be crucial for filling by electroplating the sub-0.2?m vias and trenches of high aspect ratio. A strong correlation between the ion chromatograms and the electroplated copper film properties is observed.
dual damascene copper seed layer metrology ion chromatography