W-CMP for sub-micron inverse metallisation

Chemical Mechanical Polishing (CMP) of tungsten for an inverse metallisation scheme is investigated. The influence of CMP parameters on removal rate and uniformity is studied. The main effects on the removal rate are the applied pressure and the rotation rate of the polishing pad. To the first order Preston's equation is obeyed. The uniformity is best with equal rpm of pad and wafer and with perforated pads. Also, pattern density effects of CMP of W/PETEOS are investigated. Dishing increased at larger W-linewidth. Oxide erosion increased at larger pattern density and smaller W-linewidth. Electrical measurements on submicron (0.4 and 0.5 ¿m) test structures yielded good CMP results