Stacked Image Sensor Fence Insulation for Stain-Free Color Filters
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Solution Overview
Problem
Image sensors with a stack structure face challenges in minimizing stain defects due to differences in height between patterns on the back side, leading to issues during the spin coating process for color filters, which can result in image quality degradation.
Innovation Solution
The implementation of a fence insulating layer made of the same material as the fence, extending from the shield area to the I/O pad and chip edge areas, helps to reduce height differences and minimize stain defects by replacing the metal layer outside the shield area, thereby improving image sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal layer is used in the peripheral area outside the shield area, then electrical shielding and signal integrity are improved, but height differences between patterns on the back side increase causing stain defects during spin coating
Solution Approach 1:
The patent changes the material parameter of the peripheral area layer from metal to insulating material, which eliminates the height difference issue while maintaining functional integrity through alternative design approaches
Solution Approach 2:
The patent introduces a fence insulating layer as an intermediary structure that provides mechanical support and defines boundaries without creating height differences, replacing the need for metal shielding layers in the peripheral area
2Manufacturing precision
If the fence insulating layer is extended to the I/O pad and chip edge areas, then height uniformity is improved and stain defects are reduced, but device complexity increases
Solution Approach 1:
The fence insulating layer is designed to serve multiple functions: it provides mechanical support, defines area boundaries, and ensures height uniformity across different regions including I/O pad and chip edge areas, thereby reducing overall device complexity despite extended coverage
Solution Approach 2:
The patent merges the fence insulating layer with the back-side insulating layer in certain regions, creating a unified insulating structure that simplifies manufacturing while maintaining height uniformity across the entire back side
Data Source
AI summary
An image sensor may include a first semiconductor chip including a pixel area and a peripheral area, the pixel area including a plurality of pixels, and a second semiconductor chip coupled to a lower surface of the first semiconductor chip, the second semiconductor chip including a plurality of logic elements, the pixel area including a plurality of color filters and a fence in the pixel area, the plurality of color filters corresponding to the plurality of pixels, the fence having a grid pattern, and each of the color filters of the plurality of color filters separated from each other by the fence, the peripheral area including a shield area and a shield outer area, the shield area surrounding the pixel area, and a fence insulating layer included in the shield outer area, the fence insulating layer including a same material as the fence.