Stacked Photoelectric Conversion Substrates for Warpage-Controlled Bonding
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Solution Overview
Problem
The increasing complexity of stack type photoelectric conversion apparatuses leads to warpage issues in substrates, which can result in defects such as void generation or misalignment during bonding, particularly in Cu-Cu connection type systems, where a configuration to reduce warpage is not adequately addressed.
Innovation Solution
The implementation of a photoelectric conversion apparatus with a second silicon nitride film having higher compression stress and thicker film thickness than the first silicon nitride film, along with a low-k interlayer film, to reduce the warpage of the circuit substrate and prevent bonding defects, while managing stress gradients to avoid stress-induced voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of wiring layers is increased to handle complex photoelectric conversion apparatus, then the functionality and signal processing capability are improved, but the warpage of substrates increases
Solution Approach 1:
The patent changes the physical parameters of the silicon nitride film, specifically increasing its thickness and adjusting its compression stress characteristics. By forming a second silicon nitride film with greater thickness than the first silicon nitride film, the stress distribution in the substrate is modified to counteract the warpage induced by multiple wiring layers, thus maintaining substrate flatness while supporting increased functionality
Solution Approach 2:
The patent employs a composite structure consisting of multiple silicon nitride films with different thicknesses and stress characteristics. The first silicon nitride film provides baseline stress control, while the second, thicker silicon nitride film adds enhanced compression stress to specifically address warpage issues, creating a multi-layer composite solution that balances functionality and structural stability
2Ease of manufacture
If substrates with large warp are bonded, then manufacturing complexity is reduced, but defects such as void generation or misalignment occur
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for potential bonding defects through the strategic design of the second silicon nitride film. The enhanced compression stress and increased thickness of this film are configured in advance to counteract the warpage that would otherwise lead to void generation or misalignment during the bonding process, ensuring both ease of manufacture and high bonding quality
3Shape
If a second silicon nitride film with higher compression stress and greater thickness is added, then warpage is reduced, but stress gradient increases which may cause stress-induced voids
Solution Approach 1:
The patent applies local quality by positioning the second silicon nitride film with enhanced compression stress and greater thickness at specific locations where warpage control is most critical. This localized enhancement provides targeted warpage reduction while minimizing the overall stress gradient across the entire substrate, preventing stress-induced voids in regions where they are less likely to occur
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces warpage in the circuit substrate, preventing bonding failures and misalignment, and facilitates hydrogen supply to photodiodes, thereby reducing dark current and enhancing the reliability of the photoelectric conversion apparatus.
Implementation Method 1
a second silicon nitride film having higher compression stress and a greater film thickness than a first silicon nitride film
Implementation Method 2
While it is effective to form a low-k interlayer film, a stress gradient occurs in the low-k interlayer film, and stress-induced voids are generated due to the stress gradient
Data Source
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AI summary
In a stack type photoelectric conversion apparatus in which a first substrate and a second substrate are bonded with junction electrodes disposed on the respective substrates, a first silicon nitride film disposed on the first substrate and a second silicon nitride film disposed on the second substrate differ in compression stress.