Mechanical and tribological properties of interlayer films for the damascene-Cu chemical-mechanical planarization process

Abstract

Chemical-mechanical planarization (CMP) is a key technology for the Cu-damascene wiring process in integrated circuit (IC) manufacturing. 1-3 Chemical-mechanical planarization (CMP) is important for the semiconductor industry in manufacturing six or more levels of multilevel interconnects with critical dimensions of sub-one-tenth micron. In general, each silicon wafer is exposed to 15 or more CMP steps prior to final device assembly. During CMP, the wafer is pressed face down against a rotating polishing pad, while a chemically and physically active slurry planarizes the wafer. As wafer size grows, device sizes shrink, process requirements become more rigorous, and the uniformity within die/wafer and the CMP removal rate become a greater concern. Often, a change in slurry or operating conditions leads to conflicting results. Hence, there is a need for a better understanding of all the complex tribological interactions among slurry, polishing pad, wafer, and pad conditioner. Fundamental tribological studies and characterization of consumables allow the optimization of the pad design, material selection, process pressure, orbital and linear speed, chemical solution, within-wafer uniformity, and local planarization. [4][5][6][7][8] With the shrinkage of the device dimension and the increase in device density, low dielectric-constant (low-k) materials have attracted enormous interest because they can minimize the propagation delay, interconnect capacitance, and cross talk between signal lines for deep submicron ICs. 9-11 Various low-k materials are emerging as potential replacements for SiO 2 . In addition, electrically more conductive Cu has replaced Al metallization to reduce the overall RC (resistance-capacitance) delay. 12,13 Although the device performance will improve by using low (k Ͻ 3) films along with Cu metallization, several problems need to be solved from