Back-Illuminated Pixel Isolation Structure for Shading and Color Mixing
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Solution Overview
Problem
In solid-state imaging devices of the back-illuminated type, shading and color mixing occur due to oblique light entering the periphery of the pixel region, leading to reduced image quality.
Innovation Solution
A device isolating portion with a lower refractive index than the color filter layer and substrate is formed in the solid-state imaging device to optically and electrically isolate adjacent pixels, preventing oblique light from entering adjacent pixels and reducing color mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a back-illuminated type solid-state imaging device is used to improve photoelectric conversion efficiency and sensitivity, then sensitivity is increased, but shading and color mixing occur due to oblique light entering the periphery of the pixel region
Solution Approach 1:
The device is divided into distinct functional regions: a first region with color filters for wavelength selection and a second region without color filters for receiving oblique light. This segmentation allows different parts of the device to handle different types of light, preventing color mixing while maintaining photoelectric conversion efficiency.
Solution Approach 2:
Different regions of the light receiving surface are assigned different functional characteristics. The first region (with color filters) is optimized for standard light reception, while the second region (without color filters) is optimized for oblique light reception. This local differentiation resolves the contradiction by allowing each region to perform its specialized function without interfering with the other.
2Use of energy by moving object
If on-chip lenses are provided on the light receiving surface to gather light into light receiving units, then light gathering efficiency is improved, but light gathered by on-chip lenses does not enter the central portions of light receiving units at peripheral pixels due to greater tilt of principal rays
Solution Approach 1:
The light receiving surface is segmented into a first region with on-chip lenses for standard light gathering and a second region without on-chip lenses for oblique light reception. This prevents oblique light from being incorrectly focused by on-chip lenses, ensuring that light enters the central portions of light receiving units with proper precision.
Solution Approach 2:
Instead of providing on-chip lenses uniformly across the entire light receiving surface, the invention inverts the approach by deliberately omitting on-chip lenses in the second region where oblique light enters. This inversion prevents the focusing problem caused by on-chip lenses for oblique light while maintaining their benefits in the first region.
3Manufacturing precision
If the pitch of on-chip lenses is made narrower toward the periphery of the pixel region to perform shading correction, then light entry precision is improved, but device complexity increases due to varying pitch requirements
Solution Approach 1:
The device is segmented into two regions with different lens configurations: the first region has on-chip lenses with varying pitch for shading correction, while the second region has no on-chip lenses. This segmentation allows shading correction to be applied only where needed (first region) without increasing complexity across the entire device.
Solution Approach 2:
Different pitch characteristics are applied locally to different regions. The first region uses variable pitch on-chip lenses for shading correction, while the second region uses a uniform pitch (or no lenses) for oblique light reception. This local quality approach maintains manufacturing precision where required without unnecessarily increasing device complexity elsewhere.
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
The solution effectively reduces shading and color mixing between pixels, enhancing image quality by ensuring that light is focused into the intended photoelectric conversion units, thereby improving the overall performance of the solid-state imaging device.
Implementation Method 1
a device isolating portion that is formed to divide the color filter layer and the substrate for the respective pixels, and has a lower refractive index than the refractive indexes of the color filter layer and the substrate
Implementation Method 2
signal charges in accordance with the amounts of light are generated at the light receiving units
Data Source
AI summary
The present technique aims to provide a solid-state imaging device that reduces shading and color mixing between pixels. The present invention also provides a method of manufacturing the solid-state imaging device. The present technique further relates to a solid-state imaging device that enables provision of an electronic apparatus that uses the solid-state imaging device, a method of manufacturing the solid-state imaging device, and an electronic apparatus. The solid-state imaging device includes a substrate, pixels each including a photoelectric conversion unit formed in the substrate, and a color filter layer formed on the light incidence surface side of the substrate. The solid-state imaging device also includes a device isolating portion that is formed to divide the color filter layer and the substrate for the respective pixels, and has a lower refractive index than the refractive indexes of the color filter layer and the substrate.