Pattern effects and how to explore them

Pattern effects in RTP are of increasing interest as device feature sizes decrease because of their strong impact on process uniformity and defect generation, but it has been recognized that they can sometimes be difficult to diagnose. In the literature pattern effects in production are discussed and how they affect overlay shifts. Pattern effects within test structures and their evaluation are described as well. This paper emphasizes the comparison of pattern effects with semiempirical calculations as an evidence for the existence of such pattern induced temperature inhomogeneities. Starting with the heat conduction equation a temperature profile from a pattern structure was derived and this is compared with the measured sheet resistance (R_S) distribution after RTP on a chessboard-patterned wafer that had been ion implanted on the opposite side to the pattern. The R_S distribution suggests good agreement between theoretical and measured temperature distributions. Examples of how to overcome such pattern effects are shown. Also different approaches are presented of how to measure and visualize pattern-induced non-uniformities.