Cell Deep Trench Isolation for Near-Infrared Crosstalk Reduction
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Solution Overview
Problem
Current image sensors face challenges in achieving high near-infrared light sensitivity and reducing crosstalk, particularly in security and automotive applications where improved visibility in low light conditions is crucial.
Innovation Solution
The implementation of cell deep trench isolation (CDTI) structures in pixel cells of CMOS imaging systems, which include a central portion and planar outer portions extending laterally, enhances quantum efficiency and near-infrared light sensitivity while minimizing crosstalk by optimizing the depth and arrangement of these structures within the semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isolation structures are used in pixel cells, then manufacturing is simpler, but near-infrared light sensitivity is insufficient and crosstalk is high
Solution Approach 1:
The isolation structure is divided into multiple trenches arranged in a grid pattern within each pixel cell, creating segmented isolation regions that improve near-infrared light sensitivity while maintaining manufacturability through standardized replication across the sensor array
Solution Approach 2:
The isolation structure extends into the depth dimension of the semiconductor substrate with trenches having specific depths and spacing, creating a three-dimensional isolation architecture that enhances optical performance without increasing planar footprint
2Object-generated harmful factors
If deeper trench isolation structures are implemented, then crosstalk is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The trench depth, width, and spacing parameters are optimized to specific ranges that effectively reduce crosstalk while remaining within the capabilities of standard semiconductor manufacturing processes, balancing performance improvement with manufacturing feasibility
Solution Approach 2:
The isolation trenches are strategically positioned at specific locations within each pixel cell where crosstalk is most problematic, providing localized suppression of optical interference rather than uniform isolation throughout the entire cell
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
The CDTI structures significantly improve near-infrared light sensitivity and reduce crosstalk, leading to enhanced image quality and performance in low light conditions, particularly in security and automotive applications.
Implementation Method 1
The CDTI structures significantly improve near-infrared light sensitivity and reduce crosstalk
Implementation Method 2
The image sensor includes an array of pixels having photosensitive elements (e.g., photodiodes) that absorb a portion of the incident image light and generate image charge upon absorption of the image light
Data Source
AI summary
A pixel cell includes a photodiode disposed in a pixel cell region and proximate to a front side of a semiconductor layer to generate image charge in response to incident light directed through a backside to the photodiode. A cell deep trench isolation (CDTI) structure is disposed in the pixel cell region along an optical path of the incident light to the photodiode and proximate to the backside. The CDTI structure includes a central portion extending a first depth from the backside towards the front side. Planar outer portions extend laterally outward from the central portion. The planar output portions further extend a second depth from the backside towards the front side. The first depth is greater than the second depth. Planes formed by each of the planar outer portions intersect in a line coincident with a longitudinal center line of the central portion of the CDTI structure.