Solid-state imaging device light reflector suppresses color mixing
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Solution Overview
Problem
In solid-state imaging devices with a shared on-chip lens for four photoelectric conversion sections, light scattering at the intersection of isolation regions leads to unnecessary light entering adjacent pixels, causing color mixing and reducing image definition and resolution.
Innovation Solution
Incorporating a light reflector in the photoelectric conversion sections with an inclined surface that redirects scattered light back towards the light incident surface, preventing it from entering adjacent pixels, and ensuring the inclination angle satisfies the condition θ1 ≤ 90 - arcsin(n2/n1, where n1 and n2 are the refractive indices of the photoelectric conversion section and isolation region respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a shared on-chip lens is positioned at the intersection of isolation regions to serve four photoelectric conversion sections, then the lens can be efficiently shared by multiple pixels, but light scattering occurs at the isolation region interfaces causing color mixing between adjacent pixels
Solution Approach 1:
A light reflector is introduced as an intermediary component between the shared on-chip lens and the photoelectric conversion sections. The reflector has a specific inclination angle θ1 ≤ 90 - arcsin(n2/n1) that redirects scattered light away from adjacent pixels, preventing color mixing while maintaining the shared lens configuration
Solution Approach 2:
The inclination angle of the light reflector is precisely controlled to satisfy θ1 ≤ 90 - arcsin(n2/n1), where n1 and n2 are the refractive indices of the photoelectric conversion section and isolation region respectively. This parameter optimization ensures total internal reflection of scattered light, converting the harmful scattering effect into a beneficial redirection mechanism
2Use of energy by moving object
If the condensing point of the shared on-chip lens is positioned in the isolation region, then light can be condensed effectively, but scattered light enters adjacent photoelectric conversion sections at angles exceeding the critical angle
Solution Approach 1:
The light reflector serves as a mediator that intercepts scattered light before it can enter adjacent pixels. By positioning the reflector in the photoelectric conversion sections and orienting it with the specific angle, scattered light is reflected back toward the light incident surface rather than entering neighboring pixels
Solution Approach 2:
The scattered light that would normally cause color mixing is redirected by the light reflector back toward the light incident surface. This converts the harmful scattered light into a beneficial effect by preventing it from degrading image quality while maintaining efficient light condensing at the isolation region interface
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
Effectively suppresses color mixing between pixels of different colors by redirecting scattered light, thereby improving image definition and resolution by ensuring the scattered light is totally reflected and does not enter adjacent pixels.
Implementation Method 1
the light reflector causing light condensed at the condensing point and scattered in the isolation region to be reflected toward a side opposite to the light incident surface of the semiconductor layer
Implementation Method 2
incident light condensed at the condensing point of the shared on-chip lens is scattered due to a refractive index difference between a silicon layer (n = 3.9) of the photoelectric conversion section and a silicon oxide film (n = 1.4) of the isolation region
Data Source
AI summary
Color mixing between pixels of different colors is suppressed. A solid-state imaging device includes: a semiconductor layer including a plurality of photoelectric conversion sections partitioned by an isolation region; a shared on-chip lens arranged on a light incident surface side of the semiconductor layer, the shared on-chip lens being shared by the photoelectric conversion sections adjacent to each other with the isolation region interposed between the photoelectric conversion sections, and having a condensing point positioned in the isolation region; and a concave portion provided in an upper portion of the photoelectric conversion sections that share the shared on-chip lens on the light incident surface of the semiconductor layer.