Modeling and experiments have been conducted to understand better the factors affecting process yields in silicon-silicon direct wafer bonding. An energy-based bonding criterion for direct bonding has been found to be highly effective at predicting the effects of multiple parameters, including, nanotopography, wafer shape, patterning, tool-compliance, clamping, wafer thickness and surface treatment. The work of adhesion is equated to the strain energy accumulation rate, associated with overcoming variations in wafer shape (e.g. bow and nanotopography). The strain energy accumulation rate is calculated via appropriate mechanics analysis. Insight is also provided regarding the use of the double cantilever beam test to evaluate work of adhesion. An overview of the underlying mechanics and key results is provided together with the implications of this work for improved process control and process robustness.
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