Image Sensor Light Focusing Pattern for Optical Crosstalk Reduction
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Solution Overview
Problem
Conventional image sensors face challenges in light focusing and sensitivity due to limited lightguide opening areas, leading to increased production costs and optical shading effects, as well as inefficiencies in guiding obliquely incident light.
Innovation Solution
Incorporating a light focusing pattern between the lens and the lightguide, formed from a material with a higher refractive index than the lightguide, to control incident angles and improve light focusing ability, while reducing the need for high refractive index materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the opening area of the lightguide is increased to improve light focusing ability, then the light focusing ability is improved, but the metal interconnections formed in the interlayer dielectric layer limit the opening area
Solution Approach 1:
The patent introduces a light focusing pattern layer between the lens and lightguide, adding a new dimensional element to the optical path. This pattern layer has a larger area than the lightguide opening, effectively increasing the light gathering area without modifying the lightguide structure itself, thereby resolving the contradiction between light focusing ability and opening area limitations.
2Manufacturing precision
If high refractive index material is used for the lightguide to satisfy total reflection condition, then the light focusing ability is improved, but the production cost increases
Solution Approach 1:
The patent introduces a light focusing pattern layer as an intermediary element between the lens and lightguide. This pattern layer, formed from standard interlayer dielectric material, mediates the optical path to achieve total reflection conditions without requiring the lightguide itself to be made from high refractive index materials, thereby maintaining standard manufacturing processes and reducing production costs.
3Reliability
If adjacent hemispheric lenses are spaced apart to secure incident angle for total reflection, then the total reflection condition is satisfied, but the lens design margin is reduced and light incident between adjacent lenses is lost
Solution Approach 1:
The light focusing pattern layer acts as an intermediary that extends the effective optical collection area between adjacent lenses. By having this pattern layer with larger area than the lightguide opening, it captures obliquely incident light that would otherwise be lost between lenses and guides it to the lightguide, thereby improving adaptability and lens design margin while maintaining total reflection conditions.
4Ease of manufacture
If the lightguide opening area is limited by metal interconnections, then the interlayer dielectric layer structure is maintained, but the light focusing ability is degraded
Solution Approach 1:
The patent adds a light focusing pattern layer as an additional dimensional element above the interlayer dielectric layer. This pattern layer compensates for the limited opening area imposed by the metal interconnections by providing a larger effective light gathering area, thereby maintaining the standard interlayer dielectric layer structure while improving light focusing ability.
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
Enhances light focusing and angular response, minimizes optical crosstalk, and decreases production costs by optimizing light guiding conditions and reducing material requirements.
Implementation Method 1
formed from a material with a higher refractive index than the lightguide, to control incident angles
Implementation Method 2
secure an incident angle which satisfies a total reflection condition of light incident on the lightguide
Data Source
AI summary
An image sensor includes: a substrate having a plurality of unit pixel region; a light receiving element formed in the substrate at the unit pixel region; an interlayer dielectric layer formed over the substrate; a lightguide formed in the interlayer dielectric layer for the light receiving element; a light focusing pattern formed over the interlayer dielectric layer at the pixel region; a planarization layer formed over the substrate and covering the light focusing pattern; and a lens formed over the planarization layer at the pixel region.