Deep-Trench Isolation Structure for Low Cross-Talk Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing backside-illuminated (BSI) image-sensor devices face issues with dark current and white pixel defects due to optical cross-talk, which become more pronounced as pixel sizes and spacing shrink, and current isolation methods are insufficient in addressing these defects.
Innovation Solution
The implementation of deep-trench isolation structures with a negatively charged film and a reflective grid over the substrate to reduce dark current and optical cross-talk, where the negatively charged film creates a depletion region and the reflective grid prevents incident radiation from entering the isolation structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel sizes and spacing are reduced to increase resolution, then image quality and resolution are improved, but dark current and optical cross-talk increase due to insufficient isolation between pixels
Solution Approach 1:
The substrate is divided into isolated pixel regions by deep trenches filled with dielectric material. This segmentation physically separates adjacent pixels, preventing optical cross-talk and dark current leakage between pixels, thereby maintaining image quality even as pixel sizes are reduced.
Solution Approach 2:
A dielectric material is introduced as an intermediary substance filling the deep trenches between pixels. This intermediary provides electrical isolation and optical barrier, blocking harmful effects (dark current and cross-talk) while allowing the pixels to function independently at higher densities.
2Productivity
If pixel spacing is reduced to increase pixel density, then productivity and resolution are improved, but optical cross-talk between adjacent pixels worsens
Solution Approach 1:
Deep trenches are etched between adjacent pixels to create physical segmentation. This segmentation maintains optical isolation between pixels even when spacing is reduced, enabling higher pixel density without increasing cross-talk.
Solution Approach 2:
Instead of increasing horizontal spacing to reduce cross-talk, the solution moves to the vertical dimension by etching deep trenches into the substrate. This vertical segmentation effectively blocks optical cross-talk while maintaining tight horizontal pixel spacing for high density.
3Object-affected harmful factors
If isolation structures are made deeper to reduce dark current, then dark current reduction is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The isolation structures are optimized by controlling the depth, width, and dielectric material properties of the trenches. By adjusting these parameters, effective dark current suppression is achieved without excessive depth that would complicate manufacturing.
Solution Approach 2:
The isolation structure uses composite construction with dielectric material filling the trenches. This composite approach provides both electrical isolation and optical blocking functions, effectively reducing dark current while maintaining manageable structural complexity.
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 effectively minimizes dark current and white pixel defects, enhancing the light-sensing reliability and accuracy of the image-sensor device by reducing unwanted photon interference and current leakage.
Implementation Method 1
the negatively charged film creates a depletion region
Implementation Method 2
the reflective grid prevents incident radiation from entering the isolation structures
Data Source
AI summary
An image-sensor device is provided. The image-sensor device includes a semiconductor substrate and a radiation-sensing region in the semiconductor substrate. The image-sensor device also includes a doped isolation region in the semiconductor substrate and a dielectric film extending into the doped isolation region from a surface of the semiconductor substrate. A portion of the doped isolation region is between the dielectric film and the radiation-sensing region.