Influence of oxygen precipitates on the warpage of annealed silicon wafers
The warpage of conventional Czochralski (CZ) and nitrogen-doped Czochralski silicon (NCZ) wafers with similar oxygen concentration were investigated. In the experiments, a two-step annealing process was taken to generate oxygen precipitates. After the elevated temperature annealing, no obvious warpage in both the CZ and NCZ silicon wafers was found, even if nitrogen was found to enhance oxygen precipitation and the stronger internal stresses were detected at the edge and center of an annealed wafer. It is considered that oxygen precipitates with relatively smaller sizes were successful in preventing the warpage of the silicon wafers, which is mainly dependent on thermal stress, because the oxygen precipitates can pin dislocations.
oxygen precipitates warpage silicon nitrogen