Defect Control in Cz Silicon
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DEFECT CONTROL IN Cz SILICON
Yeh * and P.D. Wildes * F.G. Kirscht *, S.B. Kim *, J.J. *Siltec Silicon, 1351 Tandem Avenue N.E., Salem, Oregon, 97303 P. Zaumseil ** **Institute of Semiconductor Physics, Frankfurt/Oder, Walter Korsing Str. 2, Germany ABSTRACT Generic and interaction aspects of oxygen precipitation, related defect formation and denudation in Cz-Si wafers are presented. Bulk defect profiles and homogenization control are shown to be achievable by proper design of post-growth annealing. Gettering-related phenomena are discussed including stacking fault-rich bulk defect structures and peculiarities in different epitaxy systems. Introduction Device manufacturers expect process wafers to behave reproducibly even with some variability in the device process. This is achieved mainly through gettering capability [1,2]. Surface and bulk characteristics of process wafers are increasingly controlled, such as the concentration level of metals and non-metals. Oxygen as the main impurity in Cz-Si is evaluated constantly, both in terms of the initial concentration and also in respect to potential surface stacking fault formation using oxidation tests. Nonetheless, it is challenging to optimize the sequence crystal growth - wafer manufacturing - device processing because of device yield - limiting effects of substrate defects and contamination. After assuring a high level in structural surface perfection and cleanliness of starting wafers, it is most important to realize near-surface regions of high perfectness applying defect denudation of polished wafers or/and deposition of epitaxial layers. Another question is how to guarantee reproducible processing behavior by homogenization of the wafer bulk. Having these requirements under control, one can start optimizing gettering techniques and processes. This paper deals with oxygen precipitation and related defect formation in current Cz silicon, with emphasis on vertical and lateral defect distribution in wafers and means of their control. Furthermore, some aspects of gettering are discussed including peculiarities of epitaxial wafers.
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Oxygen Precipitation and Related Phenomena
Annealing induced oxygen precipitation is known to increase with the initial oxygen concentration (enhanced supersaturation) and pre-annealing in the temperature range 450°C... 800°C (enhanced precipitate nucleation) [3,4]. In particular, this has been demonstrated extensively for the temperature range T Ž 1000°C because this is the range of interest for many current device processes. For low-thermalMat. Res. Soc. Symp. Proc. Vol. 262. ©1992 Materials Research Society
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the typically in budget processes, range T D 900C, the understanding and use of intrinsic point defectcontrolled defect processes will become important, contrary or supplementing to oxygen-controlled ones. But, interaction of oxygen precipitation and intrinsic point defects is also decisive for defect processes in the high-temperature/high oxygen mobility range. Due to volume
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