Controlling dislocations and bulk microdefects on fabricated wafers to prevent device leakage

摘要

Current leakage was found near the edge of a fabricated wafer. After device stripping and decorative etching, a dislocation pattern was observed near the edge of the wafer close to the device edges, suggesting the presence of furnace stress and device fabrication stress. In addition, these dislocations were found on both good and bad devices, indicating that device leakage was not strongly dependent on dislocations. A separate analysis showed that low BMD density led to insufficient intrinsic gettering, providing an additional source of failure. In IC manufacturing, gettering schemes play an important role in yield management. Since the discovery of the internal gettering effect in silicon wafers 20 years ago, many scientists and engineers have encountered difficulties in controlling the precipitation of oxygen in silicon precisely and reliably. During silicon wafer manufacturing, a wafer's bulk microdefect region has a minimum density of 10~8 cm~(-3) of oxygen precipitates. The uncontrolled precipitation of oxygen in the near-surface region of the wafer can result in device leakage, which can affect yields. Reliable and efficient internal gettering requires the robust formation of surface regions that are free of oxygen precipitates (precipitate-free zones). By reducing device leakage incidents, the MDZ method has been shown to reduce device failures and increase yields. The technique helps IC device manufacturers to minimize defect-related yield losses and to produce more good dies per wafer, boosting savings and margins in IC manufacturers' production lines.