New developments in silicon Czochralski crystal growth and wafer technology

An overview of recent progress in large-diameter crystal pulling and associated new wafer preparation technologies is given. A clear trend can be observed that, with increasing crystal diameter, the average oxygen concentration and the density of intrinsic grown in defects is reduced. Oxygen reduction and control is achieved by using magnetic fields, while bulk defect reduction requires sophisticated hot zone engineering. New growing methods currently under development result in new crystal types with a high density of interstitials in the outer area and a lower density of vacancies in the center. In addition, crystals are grown under near-equilibrium conditions so the super-saturation of the intrinsic point defects remains below the critical value required for clustering of the point defects into larger agglomerates . Geometry and light point defects/localized light scatter requirements for future wafer generations are becoming more stringent with each decrease in design rule. This leads to the necessity of novel wafer surface preparation methodologies such as advanced single side polishing, double side polishing and plasma assisted chemical etching with local wafer surface treatment. Finally, the trend toward low thermal budget integrated circuit processes leads to the necessity of having oxygen precipitation tuning and gate oxide integrity tuning, as well as the creation of a denuded zone by the silicon wafer manufacturer. New approaches to meet these requirements are annealing at high temperature and/or rapid thermal processing. The development of the new epitaxial wafer types is highlighted.