Image Sensor Color Filter Structure for Higher Transmittance and Resolution
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Solution Overview
Problem
Current image sensors face challenges in achieving improved transmittance and resolution, particularly due to issues with light reflection and absorption, which affect their operational performance and image quality.
Innovation Solution
The image sensor design incorporates a substrate with photoelectric conversion devices, a color filter featuring dielectric layers of varying thicknesses, a reflective absorption layer made of tungsten, titanium, or aluminum, and an anti-reflective layer, along with micro lenses to enhance light transmission and absorption, thereby reducing reflectance and improving resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional color filter with uniform dielectric layers is used, then the manufacturing process is simple, but the light transmittance and resolution are insufficient
Solution Approach 1:
The color filter employs dielectric layers with locally varied thicknesses rather than uniform thickness throughout. Specifically, the first through fourth dielectric layers have different thickness distributions in the second direction, creating spatially varying optical properties that enhance resolution and light transmittance while maintaining manufacturability through standard deposition processes
Solution Approach 2:
The patent introduces thickness variation in the second direction (vertical dimension) of the dielectric layers to improve optical performance. By controlling the thickness of each dielectric layer differently along the second direction, the color filter achieves enhanced light management capabilities without complicating the planar layout or manufacturing process
2Manufacturing precision
If light reflection is not managed, then the structure is simpler, but transmittance and image quality deteriorate
Solution Approach 1:
The reflective absorption layer converts harmful light reflection into a beneficial effect by re-reflecting reflected light back toward the dielectric layers and photoelectric conversion devices. This layer, positioned between the color filter and anti-reflective layer, transforms what would be lost reflected light into additional useful light for image capture, thereby enhancing transmittance and image quality
Solution Approach 2:
The patent employs a composite layered structure combining dielectric layers with different refractive indices, a reflective absorption layer, and an anti-reflective layer. This multi-material composite approach optimizes light transmission by managing reflection at each interface, with each material selected for its specific optical properties to collectively enhance overall transmittance
3Manufacturing precision
If micro lenses are placed close to the substrate, then the structure is compact, but light transmission is blocked by the substrate
Solution Approach 1:
The anti-reflective layer serves as an intermediary element between the reflective absorption layer and the micro lenses. This intermediate layer reduces reflection losses and facilitates better light transmission from the micro lenses through the color filter to the photoelectric conversion devices, thereby improving light transmission without requiring increased spacing
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 configuration significantly enhances transmittance and resolution by effectively managing light reflection and absorption, leading to improved image sensor performance and reliability.
Implementation Method 1
the reflective absorption layer is configured to re-reflect light reflected from the plurality of dielectric layers toward the reflective absorption layer, such that the re-reflected light is reflected toward the plurality of dielectric layers
Implementation Method 2
a plurality of micro lenses on the reflective absorption layer, configured to focus external light on the plurality of photoelectric conversion devices
Implementation Method 3
a substrate including a plurality of photoelectric conversion devices that define a matrix
Data Source
AI summary
An image sensor includes a substrate including a plurality of photoelectric conversion devices, a color filter arranged on the substrate, a reflective absorption layer on the color filter and comprising at least one of tungsten, titanium, and aluminum, an anti-reflective layer arranged on the reflective absorption layer, and a plurality of micro lenses on the anti-reflective layer. The color filter may include a plurality of dielectric layers extending in a first direction that is parallel to a rear surface of the substrate, the plurality of dielectric layers having different thicknesses in a second direction that is perpendicular to the rear surface of the substrate and perpendicular to the first direction, such that the plurality of dielectric layers includes at least one dielectric layer having a thickness in the second direction that varies along the first direction.