Trapezoidal Pixel Gate Structure for FWC and Crosstalk Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensors face challenges in improving full well capacity (FWC) and reducing optical crosstalk, which affect image quality.
Innovation Solution
The image sensor structure incorporates a gate with a trapezoidal cross-section located in the substrate, featuring different widths for opposing surfaces to enhance full well capacity and adjust optical crosstalk, including a dielectric layer, photodetector, and floating diffusion region, with optional protrusions and isolation structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the gate width is increased to improve full well capacity, then the light collection area is improved, but optical crosstalk between adjacent pixels increases
Solution Approach 1:
The gate is designed with an asymmetric cross-sectional shape where the first width (at the light-receiving surface) is greater than the second width (at the bottom surface). This asymmetric configuration allows the gate to collect more light at the top while maintaining better isolation at the bottom, thereby improving full well capacity without significantly increasing optical crosstalk.
Solution Approach 2:
Different portions of the gate have different widths to serve different functions: the wider first width at the light-receiving surface optimizes light collection, while the narrower second width at the bottom surface improves isolation between pixels. This local variation in geometry resolves the contradiction between light collection and crosstalk reduction.
2Object-generated harmful factors
If the gate is positioned deeper in the substrate to reduce optical crosstalk, then isolation between pixels is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of simply moving the gate deeper in the substrate (one-dimensional solution), the invention introduces a two-dimensional cross-sectional shape variation with different first and second widths. This dimensional approach allows the gate to achieve better isolation without requiring excessive depth, thereby reducing manufacturing complexity while still reducing optical crosstalk.
3Ease of manufacture
If the gate cross-section is made uniform to simplify manufacturing, then fabrication is easier, but optical crosstalk reduction is compromised
Solution Approach 1:
The gate employs an asymmetric cross-section with different first and second widths, which provides effective optical crosstalk reduction. While this increases fabrication complexity compared to a uniform gate, the asymmetric design can be integrated into existing manufacturing processes through controlled deposition and etching techniques, achieving a balance between performance and manufacturability.
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 effectively increases full well capacity and reduces optical crosstalk, thereby enhancing image quality.
Implementation Method 1
The photodetector is located in the substrate on one side of the gate
Data Source
AI summary
An image sensor structure including a substrate and a pixel structure is provided. The substrate includes a front side and a backside opposite to each other. The pixel structure includes a gate, a dielectric layer, a photodetector, and a floating diffusion region. The gate is located in the substrate. The gate includes a first surface and a second surface opposite to each other. The first surface is closer to the front side than the second surface. The width of the first surface is different from the width of the second surface. The dielectric layer is located between the gate and the substrate. The photodetector is located in the substrate on one side of the gate. The floating diffusion region is located in the substrate between the front side and the photodetector.