Back-Illuminated Sensor Layout for Optical Black Signal Accuracy
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Solution Overview
Problem
Back illuminated photoelectric conversion devices face accuracy issues in acquiring a reference signal of a black level due to light entering the optical black pixel area as a waveguide, leading to errors in the reference signal.
Innovation Solution
A photoelectric conversion device is designed with a semiconductor substrate having a light shielding layer and an attenuating member in specific areas to prevent guided light from entering the optical black pixel area, using a light absorbing member or diffraction grating to attenuate light, thereby reducing the intensity of guided light reaching the optical black pixel area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light shielding film is added to block light from entering the optical black pixel area, then reference signal accuracy improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The light shielding film in the optical black pixel area is merged with the existing pixel structure and wiring layers. The shielding film is integrated into the back surface illumination structure, sharing the same fabrication process steps as the pixel electrodes and wiring, thereby reducing overall device complexity despite adding light blocking functionality.
Solution Approach 2:
The light shielding film serves multiple functions: it blocks light from reaching optical black pixels during normal operation, acts as an electrode for the back-illuminated structure, and can be patterned to define pixel boundaries. This multi-functionality reduces the need for separate components and simplifies the overall device structure.
2Measurement precision
If the semiconductor substrate is thinned to reduce reflection loss, then sensitivity improves, but manufacturing precision requirements increase due to handling difficulties
Solution Approach 1:
The semiconductor substrate is thinned to the required thickness before the pixel structure and wiring layers are formed. This preliminary thinning action allows subsequent processing steps to be performed on a substrate of the final required thickness, ensuring that no additional thinning is needed after device assembly, thereby maintaining manufacturing precision while achieving the sensitivity benefits of a thin substrate.
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 attenuates guided light, improving the accuracy of the reference signal by reducing light interference, thus enhancing the overall performance of the photoelectric conversion device.
Implementation Method 1
An attenuating member that attenuates a guided light entering the first area and propagating to the second area with the semiconductor substrate as a waveguide is arranged in the third area
Implementation Method 2
light incident from an area having no light shielding film may enter the optical black pixel area with the semiconductor substrate as a waveguide
Data Source
AI summary
Provided is a back illuminated photoelectric conversion device including a semiconductor substrate that has a first area that is not light-shielded by a light shielding layer, a second area that is light-shielded by the light shielding layer and in which a second pixel is arranged, and a third area that is arranged between the first area and the second area in a plan view. An attenuating member that attenuates a guided light entering the first area and propagating to the second area with the semiconductor substrate as a waveguide is arranged in the third area.