Image Sensor Substrate Lens and Surface Trap Region Design
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Solution Overview
Problem
Highly integrated image sensors face challenges with increased signal noise and cross-talk due to smaller pixel sizes, which affect light concentration and dark current characteristics.
Innovation Solution
The image sensor design includes a substrate with a photoelectric conversion part, a multi-layered interconnection, and a substrate lens part with a surface trap region, where the substrate lens part can have various shapes and is formed using laser irradiation to improve light concentration and reduce interference, and the surface trap region is doped with materials like boron, fluorine, and germanium to enhance dark current characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pixel size is reduced for higher integration, then the integration density increases, but cross talk between pixels increases and signal noise increases
Solution Approach 1:
The substrate is divided into multiple pixel regions with isolated photoelectric conversion parts. Each pixel is separated by substrate removal regions, creating physical segmentation that prevents cross-talk while maintaining high integration density. The segmentation is achieved by selectively removing substrate material between pixels to form isolated islands of photoelectric conversion structures.
Solution Approach 2:
The substrate lens parts are formed with different shapes (convex, concave, or flat) at different pixel locations to optimize light concentration for each pixel's specific requirements. The surface trap regions are selectively formed only at specific locations where needed for dark current suppression, rather than uniformly across the entire substrate, allowing localized optimization of photoelectric conversion efficiency.
2Productivity
If the pixel size is reduced for higher integration, then the integration density increases, but the light concentration capability decreases
Solution Approach 1:
Convex substrate lens parts are formed at selected pixel locations by removing surrounding substrate material, creating curved surfaces that focus and concentrate incident light onto the photoelectric conversion parts. The spherical or dome-shaped lens structures increase light concentration capability despite the reduced pixel size, improving the optical collection efficiency of each pixel.
Solution Approach 2:
The substrate lens parts are formed as simplified versions of traditional micro-lens structures, using the substrate material itself rather than adding separate lens layers. This copying approach replicates the light-focusing function of conventional micro-lenses while being integrated into the substrate fabrication process, reducing complexity and maintaining high integration density.
3Illumination intensity
If a substrate lens part is added to improve light concentration, then the light concentration increases, but the device complexity increases
Solution Approach 1:
The substrate lens parts are merged with the substrate itself, forming an integrated structure where the lens is not a separate component but a modification of the substrate material. The photoelectric conversion parts, substrate lens parts, and surface trap regions are combined in a single fabrication process sequence, reducing the number of discrete components and simplifying the overall device structure while maintaining light concentration capability.
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support, contains the photoelectric conversion parts, forms the substrate lens parts for light concentration, and creates surface trap regions for dark current suppression. This multi-functionality reduces the need for additional separate components, simplifying the device structure while achieving multiple performance improvements simultaneously.
4Reliability
If surface trap region is formed to improve dark current characteristic, then the dark current suppression improves, but the manufacturing process complexity increases
Solution Approach 1:
Surface trap regions are formed preliminarily during the substrate processing stage, before the photoelectric conversion parts are fully assembled. By creating the surface trap regions early in the fabrication process through selective substrate removal and doping, the patent simplifies subsequent manufacturing steps and reduces overall process complexity while achieving dark current suppression.
Solution Approach 2:
The substrate material itself is used to create the surface trap regions through selective removal and doping, rather than requiring separate trap region materials or components. The substrate serves its own function of creating the trap regions that will suppress dark current, eliminating the need for additional materials or complex assembly steps.
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 enhances light sensitivity by increasing light concentration, reducing pixel interference, and improving dark current characteristics through the use of a substrate lens part and surface trap region, leading to improved image sensor performance.
Implementation Method 1
irradiating a laser on a surface of the substrate pattern to change a shape of the substrate, thereby forming a substrate lens part
Implementation Method 2
the substrate pattern may be heated at a temperature within a range of about 1000 degrees Celsius to about 1450 degrees Celsius by irradiating the laser
Implementation Method 3
The PD converts an incident light into an electric signal
Implementation Method 4
the impurities may be diffused and activated at a surface of the substrate lens part by irradiating the laser
Data Source
AI summary
The inventive concept provides image sensors and methods of forming the same. In the image sensor, a surface trap region may be disposed to be adjacent to a surface of a substrate lens component. Thus, a dark current characteristic may be improved.