An advanced finite element model for BiCMOS process oriented ultra-thin wafer deformation

Cao, Zhibo and Goritz, Alexander and Stocchi, Matteo and Wietstruck, Matthias and Hoyer, Christian and Steinweg, Luca David and Carta, Corrado and Ellinger, Frank and Tillack, Bernd and Kaynak, Mehmet (2022) An advanced finite element model for BiCMOS process oriented ultra-thin wafer deformation. IEEE Transactions on Semiconductor Manufacturing, 35 (1). pp. 2-10. ISSN 0894-6507 (Print) 1558-2345 (Online)

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A process-oriented wafer-scale finite element model is developed and validated. The model is used to study the relationship between the in-plane residual stress and the deformation of state-of-the-art 0.13- μ m SiGe BiCMOS fully processed 8-inch wafers. Based on the in-situ wafer bow measurement results, the residual stress values are extracted regarding each deposited material per process step. The extracted material residual stress values are integrated into the in-plane stresses of each back-end redistribution layer by knowing the material densities, greatly reducing the computational effort. An advanced finite element model composed of these integrated redistribution layers is therefore developed by exploiting the first order shear deformation theory. The model is validated using analytical solutions and is used to characterize the wafer thickness-deflection non-linear relationship. As a comparison, 8 fully processed BiCMOS wafers from the same lot are thinned to different thicknesses ranging from 50 μ m to 600 μ m for bow measurement. After taking the gravity-induced deflection and grinding effect into consideration, the wafer bow predicted by the finite element model deviates less than 20% from the measurement results for all the thickness values.
Item Type: Article
Uncontrolled Keywords: BiCMOS process; finite element analysis (FEA); stress modeling; ultra-thin wafer; wafer warping
Divisions: Faculty of Engineering and Natural Sciences
Depositing User: Mehmet Kaynak
Date Deposited: 27 Aug 2022 11:07
Last Modified: 27 Aug 2022 11:07

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