Back-Illuminated CMOS Sensor Wiring with Segmented Reflection Film
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Solution Overview
Problem
In back-illumination type CMOS image sensors, long wavelength light is not adequately absorbed and can cause color mixture due to reflection from wiring layers, leading to degraded image quality, and existing solutions restrict wiring layout or fail to adequately suppress color mixture.
Innovation Solution
A solid-state imaging element with a photoelectric conversion unit and a wire pattern on its bottom surface, where the pattern is arranged to disperse transmitted light and prevent reflection back to adjacent pixels, and a reflection film that overlaps with part of the bottom surface of the photoelectric conversion unit to direct light back to the same pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reflection layer is formed on the opposite surface of the light incident side to prevent color mixture, then image quality is improved, but wiring layout is restricted
Solution Approach 1:
The reflection layer is segmented into a plurality of reflection regions with different reflectivities rather than using a uniform reflection layer. This segmentation allows different portions of the substrate to have optimized reflection characteristics, preventing color mixture while maintaining wiring layout flexibility.
Solution Approach 2:
Different reflection regions are assigned different reflectivities based on their local requirements. Regions closer to pixel centers have higher reflectivity to prevent color mixture, while regions near wiring areas have lower reflectivity to accommodate wiring layouts. This local optimization resolves the contradiction between image quality and wiring layout.
2Device complexity
If wiring layout is prioritized over reflection layer arrangement, then wiring flexibility is improved, but color mixture suppression is insufficient
Solution Approach 1:
The reflection layer is designed with spatially varying reflectivity where regions adjacent to wiring structures have reduced reflectivity to accommodate wiring placement, while other regions maintain high reflectivity to suppress color mixture. This local differentiation allows both wiring flexibility and color mixture prevention.
Solution Approach 2:
The wiring structures that would normally cause harmful reflections are positioned in regions with deliberately reduced reflectivity. The potential harm from wiring reflections is converted into a benefit by strategically placing low-reflection regions at wiring locations, thereby preventing color mixture while maintaining wiring layout flexibility.
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
Improves image quality by effectively dispersing transmitted light and reducing color mixture, while allowing for more flexible wiring layouts and maintaining high conversion efficiency.
Implementation Method 1
a photoelectric conversion unit adapted to photoelectrically convert incident light incident from a predetermined incident surface
Implementation Method 2
formed with a protruding pattern on a surface facing the photoelectric conversion unit... A plurality of the above-described patterns can be arranged in the one photoelectric conversion unit
Implementation Method 3
a reflection layer made of tungsten is formed on an opposite surface of a light incident side of a substrate layer... the light having passed through the photoelectric conversion unit is reflected in a direction to the same photoelectric conversion unit
Data Source
AI summary
The present technology relates to a solid-state imaging element and an electronic device capable of improving image quality of the solid-state imaging element. The solid-state imaging element includes a photoelectric conversion unit adapted to photoelectrically convert incident light incident from a predetermined incident surface. Also, the solid-state imaging element includes a wire arranged on a bottom surface side that is an opposite surface of the incident surface of the photoelectric conversion unit, and formed with a protruding pattern on a surface facing the photoelectric conversion unit. The present technology can be applied to, for example, a solid-state imaging element such as a CMOS image sensor, and an electronic device including the solid-state imaging element.