Warpage of Czochralski-Grown Silicon Wafers as Affected by Oxygen Precipitation

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Abstract
The warpage of Czochralski-grown silicon wafers was investigated in relation to oxygen precipitation caused by simulated heat-treatments at 1000°C and LSI processing, using specimens cut from measured positions along the crystal length. The warpage of the wafers due to simulated thermal stresses increases with the concentration of precipitated oxygen atoms associated with the formation of SiO2 precipitates observed in infrared spectra at around 1224 cm-1, reaching a maximum in the seed-end and a minimum in the tail-end wafers. LSI processing experiments showed that the microdefect density resulting from the nuclei in as-grown ingots must be equal to or lower than 5×109 cm-3 to reduce the warpage and improve the chip yield of devices, even if the microdefect density in the bulk is increased to aim at the intrinsic gettering effect.