Effect of dislocation density on residual stress in polycrystalline silicon wafers
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The goal of this research was to examine the relationship between dislocation density and in-plane residual stress in edge-defined film-fed growth (EFG) silicon wafers. Previous research has shown models for linking dislocation density and residual stress based on temperature gradient parameters during crystal growth. Residual stress and dislocation density have a positive relationship for wafers with very low dislocation density such as Cz wafers. There has been limited success in experimental verifications of residual stress for EFG wafers, without any reference to dislocation density. No model of stress relaxation has been verified experimentally in post production wafers. A model that assumes stress relaxation and links residual stress and dislocation density without growth parameters will be introduced here. Dislocation density and predominant grain orientation of EFG wafers have been measured by the means of chemical etching/optical microscope and x-ray diffraction, respectively. The results have been compared to the residual stress obtained by a near infrared transmission polariscope. A model was established to explain the results linking dislocation density and residual stress in a randomly selected EFG wafer.