Stress Characterization of Post-CMP Copper Films Planarized Using Novel Low-Shear and Surface-Engineered Pads

A family of novel low-shear and surface-engineered pads for copper chemical mechanical planarization (CMP) are designed and evaluated for polishing characteristics and process induced stress. Tribological studies are carried out on blanket copper films using these low-shear/surface-engineered pads and comparison is made with state of the art commercial pads (IC1000 and JSR). Results indicate that low-shear surface-engineered pads exhibit vastly improved tribological performance. These pads exhibit a 40% lower coefficient of friction (COF) over a larger range of Sommerfeld numbers (So) compared to commercial pads. A simplified XRD line profiling technique has been utilized to characterize stress within post-CMP copper films. The (222) Bragg peak position obtained from the XRD spectra of films polished using low-shear surface-engineered pads indicates virtually no shift compared to the peak position for the unpolished copper films. This result establishes that almost no stress is incorporated during bulk Copper removal using the newly designed pads.