Stacked Image Sensor Alignment Keys for Miniaturized Pixels
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Solution Overview
Problem
Current image sensors face challenges in achieving miniaturization and high resolution while maintaining reliability, particularly in the design and manufacturing processes.
Innovation Solution
The image sensor design includes a stacked chip structure with a first and second substrate, interconnection structures, insulating layers, photoelectric conversion elements, grid layers, color filters, and a key pattern layer in the alignment key area to enhance alignment accuracy and reliability, optimizing the structure to improve manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the chip structure is miniaturized to achieve high resolution, then the resolution is improved, but the alignment accuracy deteriorates
Solution Approach 1:
The chip structure is divided into a first chip structure and a second chip structure that are disposed at different heights. The first chip structure includes a first substrate with a first interconnection structure and first insulating layer, while the second chip structure includes a second substrate with photoelectric conversion elements, second interconnection structure, and second insulating layer. This segmentation allows each chip structure to be optimized independently for both miniaturization and alignment accuracy.
Solution Approach 2:
The patent introduces a vertical dimension by stacking the first and second chip structures at different heights. The first chip structure is disposed at a first height and the second chip structure is disposed at a second height, creating a three-dimensional stacked architecture. This dimensional change enables miniaturization in the horizontal plane while maintaining alignment accuracy through vertical positioning and alignment key structures.
2Manufacturing precision
If the chip structure is miniaturized to achieve high resolution, then the resolution is improved, but the reliability deteriorates
Solution Approach 1:
Alignment key structures are formed on both the first and second substrates before the final assembly process. These alignment keys extend through the insulating layers and provide predetermined alignment references that cushion against misalignment during manufacturing and assembly, ensuring reliable positioning even in miniaturized high-resolution chips.
Solution Approach 2:
Insulating layers are introduced as intermediary structures between the interconnection structures and the alignment keys. The first insulating layer covers the first interconnection structure, and the second insulating layer covers the second interconnection structure, providing electrical isolation while allowing the alignment keys to maintain mechanical and positional integrity throughout the stacked structure.
3Manufacturing precision
If alignment key structures are added to improve alignment accuracy, then the alignment accuracy is improved, but the device complexity increases
Solution Approach 1:
The alignment key structures serve multiple functions: they provide alignment references for stacking accuracy, extend through insulating layers to maintain electrical isolation, and are integrated into the existing substrate and interconnection structure fabrication processes. This multi-functionality reduces the need for separate alignment mechanisms, thereby limiting the increase in device complexity.
Solution Approach 2:
The alignment keys are merged with the substrate and insulating layer structures during the fabrication process. The first alignment keys are formed on the first substrate with the first insulating layer, and the second alignment keys are formed on the second substrate with the second insulating layer, combining alignment functionality with the structural layers rather than adding separate components.
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 design improves the reliability and alignment accuracy of image sensors, addressing the challenges of miniaturization and high resolution by optimizing the chip structure and manufacturing processes.
Implementation Method 1
photoelectric conversion elements disposed in the second substrate disposed in the pixel area
Data Source
AI summary
Provided is an image sensor including a substrate, in which a pixel area including a plurality of unit pixels, an optical black area located outside of the pixel area, and an alignment key area located outside of the pixel area are included, the substrate having a first surface and a second surface opposing the first surface, an interconnection structure below the first surface of the substrate, photoelectric conversion elements in the pixel area of the substrate, an insulating layer on the second surface of the substrate, a grid layer on the insulating layer in the pixel area and the alignment key area, a key pattern layer between the insulating layer disposed in the alignment key area and the grid layer disposed in the alignment key area, the key pattern layer including a protruding region to correspond to the grid layer, and color filters on the insulating layer and the grid layer in the pixel area.