Conformal Doped Isolation for Image Sensor Dark Current Control
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Solution Overview
Problem
Conventional semiconductor image sensors face challenges in controlling excessive dark current and cross-talk due to shrinking pixel sizes, with existing methods being costly and complex, and often resulting in poor performance.
Innovation Solution
The method involves forming conformal doped regions around deep trench isolation structures using solid phase or gas phase doping processes, eliminating the need for ion implantation and reducing fabrication complexity, thereby improving dark current and cross-talk performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ion implantation processes are used to control dark current and cross-talk, then pixel isolation can be achieved, but the fabrication complexity and cost increase significantly
Solution Approach 1:
The patent extracts and eliminates the ion implantation step from the conventional fabrication process. Instead of using complex ion implantation to create doped regions, the invention uses simple thermal diffusion of dopants through the isolation dielectric material, thereby reducing fabrication complexity while maintaining dark current control performance
Solution Approach 2:
The isolation dielectric material serves as an intermediary that enables dopant diffusion to create doped regions. By using the dielectric material itself as the diffusion path, the patent eliminates the need for separate ion implantation equipment and processes, reducing both complexity and cost while achieving the desired pixel isolation
2Reliability
If ion implantation processes are used for dopant diffusion, then doped regions can be formed, but expensive lithography tools are required
Solution Approach 1:
The patent removes the requirement for expensive lithography tools by eliminating ion implantation. The doped regions are formed through thermal diffusion processes that use standard semiconductor fabrication equipment, significantly reducing manufacturing costs while maintaining effective cross-talk isolation between pixels
Solution Approach 2:
The isolation dielectric material serves a dual function: it provides electrical isolation between pixels and simultaneously acts as the medium for dopant diffusion. This self-service approach eliminates the need for separate, expensive lithography and ion implantation steps, making the process more cost-effective
3Productivity
If pixel size is reduced to increase sensor resolution, then more pixels can be packed, but dark current and cross-talk become harder to control
Solution Approach 1:
The patent forms doped regions around the isolation structures before the pixels are fully defined and before dark current issues manifest. This preliminary doping action creates isolation barriers in advance, enabling better control of dark current and cross-talk even as pixel sizes continue to shrink for higher density sensors
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 enhances dark current and cross-talk performance by creating effective barriers between pixels without the need for expensive lithography tools or complex implantation processes, using existing equipment and processes for dopant diffusion.
Implementation Method 1
a doped region is formed in the substrate using one of: a solid phase doping process and a gas phase doping process
Data Source
AI summary
Provided is a semiconductor image sensor device. The image sensor device includes a substrate. The image sensor device includes a first pixel and a second pixel disposed in the substrate. The first and second pixels are neighboring pixels. The image sensor device includes an isolation structure disposed in the substrate and between the first and second pixels. The image sensor device includes a doped isolation device disposed in the substrate and between the first and second pixels. The doped isolation device surrounds the isolation structure in a conformal manner.