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An Experimental and Numerical Study on Glass Frit Wafer-to-Wafer Bonding
Seyed Amir Fouad Farshchi Yazdi1, Matteo Garavaglia2, Aldo Ghisi1
1Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy.
Micromachines
|January 21, 2023
Summary
This study investigates thermo-mechanical wafer bonding using glass frit, analyzing residual stresses and wafer warpage. Experiments and simulations reveal key material properties and their impact on bonding integrity.
Area of Science:
- Materials Science
- Mechanical Engineering
- Semiconductor Manufacturing
Background:
- Wafer-to-wafer bonding is critical in semiconductor fabrication.
- Residual stresses significantly impact wafer warpage and device performance.
- Glass frit is a potential material for advanced bonding processes.
Purpose of the Study:
- To experimentally characterize the thermo-mechanical properties of glass frit material.
- To investigate the effect of residual stresses on wafer warpage during bonding.
- To validate a thermo-mechanical numerical model for predicting wafer deformation.
Main Methods:
- Material characterization using confocal laser profilometry, scanning electron microscopy, energy dispersive X-ray spectroscopy, nanoindentation, and die shear tests.
- Experimental analysis of glass frit mechanical properties (Young's modulus, Poisson's ratio, hardness, shear strength).
- Thermo-mechanical numerical simulations to model residual stress effects on wafer warpage.
Main Results:
- Measured Young's modulus: 86.5 ± 9.5 GPa; Poisson's ratio: 0.19 ± 0.02; Hardness: 5.26 ± 0.8 GPa.
- Lowest nominal shear strength measured between 1.13–1.58 MPa across tested strain rates.
- Numerical simulations showed acceptable agreement with experimental warpage measurements.
Conclusions:
- The study provides crucial material data for glass frit in wafer bonding.
- Thermo-mechanical modeling effectively predicts wafer warpage due to residual stresses.
- The findings contribute to optimizing wafer bonding processes for reduced warpage.
