Image Sensor Gate Pattern Height Segmentation for Halo Implantation
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Solution Overview
Problem
In image sensor manufacturing, the formation of a self-aligned photoelectric conversion region is challenging due to the difficulty in maintaining a thin gate pattern, which affects the threshold voltage control of MOS transistors and overall image quality, especially when the gate pattern height is reduced in peripheral circuit regions.
Innovation Solution
A method involving the sequential stacking of a gate electrode layer and a mask layer on a substrate, patterning to form gate patterns, and subsequent impurity implantation in the pixel array region to create a self-aligned photoelectric conversion region, while maintaining a thin gate pattern in the peripheral circuit region, using layers like silicon oxide or silicon oxide nitride for the mask and specific etching solutions for mask removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the gate pattern height is reduced in peripheral circuit regions to enable halo ion implantation, then the aspect ratio problem is resolved and halo implantation becomes possible, but the threshold voltage control of MOS transistors deteriorates due to undesired impurity diffusion
Solution Approach 1:
The substrate is divided into pixel array regions and peripheral circuit regions, with different gate pattern heights in each region. The pixel array region maintains a first gate pattern height that prevents impurity diffusion, while the peripheral circuit region uses a second gate pattern height that enables halo ion implantation. This spatial segmentation resolves the contradiction by allowing both conditions to coexist in different locations.
Solution Approach 2:
Different gate pattern heights are applied to different functional regions of the substrate. The pixel array region requires a specific gate height for precise threshold voltage control, while the peripheral circuit region requires a different gate height for halo implantation capability. This local differentiation allows each region to have optimized properties for its specific function.
2Manufacturing precision
If a thick gate pattern is used in pixel array region to prevent impurity diffusion, then threshold voltage control is maintained, but halo ion implantation becomes impossible in peripheral circuit regions
Solution Approach 1:
The substrate is divided into pixel array regions and peripheral circuit regions, with different gate pattern heights in each region. The pixel array region maintains a first gate pattern height that prevents impurity diffusion, while the peripheral circuit region uses a second gate pattern height that enables halo ion implantation. This spatial segmentation resolves the contradiction by allowing both conditions to coexist in different locations.
Solution Approach 2:
Different gate pattern heights are applied to different functional regions of the substrate. The pixel array region requires a specific gate height for precise threshold voltage control, while the peripheral circuit region requires a different gate height for halo implantation capability. This local differentiation allows each region to have optimized properties for its specific function.
3Ease of manufacture
If the gate pattern height is uniformly reduced across the entire substrate, then halo ion implantation is enabled in peripheral circuits, but undesired impurity diffusion occurs in pixel array region affecting image quality
Solution Approach 1:
The substrate is divided into pixel array regions and peripheral circuit regions, with different gate pattern heights in each region. The pixel array region maintains a first gate pattern height that prevents impurity diffusion, while the peripheral circuit region uses a second gate pattern height that enables halo ion implantation. This spatial segmentation resolves the contradiction by allowing both conditions to coexist in different locations.
Solution Approach 2:
Different gate pattern heights are applied to different functional regions of the substrate. The pixel array region requires a specific gate height for precise threshold voltage control, while the peripheral circuit region requires a different gate height for halo implantation capability. This local differentiation allows each region to have optimized properties for its specific function.
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 ensures the formation of a self-aligned photoelectric conversion region in the pixel array, maintaining reliable transistor driving capability in the peripheral circuit region, thereby enhancing image sensor quality and preventing undesired impurity diffusion.
Implementation Method 1
implanting impurities in the substrate in the pixel array region to form a photoelectric conversion region
Data Source
AI summary
In an image sensor and a method for forming the same, the method comprises: preparing a substrate having a pixel array region and a peripheral circuit region; sequentially stacking a gate electrode layer and a mask layer on the substrate; patterning the gate electrode layer and the mask layer to form a gate pattern; implanting impurities in the substrate in the pixel array region to form a photoelectric conversion region; and removing the mask layer.