Back-illuminated Imaging Device Interconnect Routing
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Solution Overview
Problem
Back-illuminated image sensors face challenges in simplifying the routing of interconnects between capacitive deep trench isolations and biasing voltage contact pads without interfering with control logic, and existing methods complicate fabrication with metal filling and chemical mechanical planarization risks.
Innovation Solution
A continuous electrically conductive layer forms electrodes in capacitive deep trench isolations and acts as a redistribution layer to connect to biasing voltage contact pads, eliminating the need for additional trenches and simplifying fabrication, while also serving as a light guide to enhance quantum efficiency and prevent moisture penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal filling and chemical mechanical planarization are used to create capacitive deep trench isolations, then crosstalk suppression is improved, but fabrication complexity and delamination risks increase
Solution Approach 1:
The patent extracts the metal filling step and chemical mechanical planarization process from the fabrication sequence, replacing them with a simplified approach using only dielectric material filling. This eliminates the delamination risks and fabrication complexity while preserving the capacitive isolation function through alternative means.
Solution Approach 2:
The patent discards the metal filling approach entirely, recovering instead a pure dielectric filling method that achieves the same electrical isolation and capacitive effect without the harmful side effects of metal deposition and planarization processes.
2Reliability
If additional trenches are created for interconnect routing, then electrical connection between electrodes and contact pads is improved, but control logic layout flexibility is reduced
Solution Approach 1:
The dielectric layer serving as trench filling material is given multiple functions: it provides electrical isolation in the trenches, forms capacitive structures, and simultaneously serves as the interconnect routing medium. This multi-functionality eliminates the need for separate metal interconnect trenches, preserving layout flexibility while ensuring electrical connectivity.
Solution Approach 2:
The patent merges the isolation function, capacitive function, and interconnect routing function into a single dielectric structure. By combining these functions that were previously separated into different components (metal trenches for routing, separate isolation structures), the design maintains layout flexibility while achieving all necessary electrical functions.
3Reliability
If the back side of the substrate is used for illumination, then quantum efficiency is improved, but interconnect routing becomes more complex
Solution Approach 1:
Instead of routing interconnects through the front side (BEOL) as in conventional designs, the patent inverts the approach by using the back side dielectric layers for interconnect routing. This inversion leverages the already-present dielectric structures on the back side, turning what would be a complexity into a solution that maintains both back-illumination capability and simplified routing.
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 solution simplifies interconnect routing, reduces fabrication complexity, enhances quantum efficiency, and prevents delamination risks, ensuring compatibility with CMOS processes and low thermal budgets, while effectively biasing capacitive trenches without interfering with control electronics.
Implementation Method 1
capacitive deep trench isolations
Implementation Method 2
said filling material holding negative fixed charges, which said filling material makes it possible to attract holes
Data Source
AI summary
A back-illuminated integrated imaging device is formed from a semiconductor substrate including a zone of pixels bounded by capacitive deep trench isolations. A peripheral zone is located outside the zone of pixels. A continuous electrically conductive layer forms, in the zone of pixels, an electrode in a trench for each capacitive deep trench isolation, and forms, in the peripheral zone, a redistribution layer for electrically coupling the electrode to a biasing contact pad. The electrode is located in the trench between a trench dielectric and at least one material for filling the trench.