CMOS Linear Sensor Wiring Stacking for Uniform Light Reception
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Solution Overview
Problem
CMOS linear image sensors face issues with uneven light reception due to multilayer wirings, leading to shading and reduced signal-to-noise ratio, particularly in scanners where light incidence angles vary across pixels, limiting the optical system's versatility.
Innovation Solution
The configuration of the photoelectric conversion element includes a photodetector with a first shaded region and a second shaded region, where the openings between wirings are optimized to minimize light rejection, allowing for uniform light reception across pixels regardless of light incidence angles, and the arrangement of wirings is adjusted to reduce shading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple circuits and multilayer wirings are configured in a CMOS sensor pixel, then high speed processing capability is improved, but the opening area of the pixel is reduced and light reception becomes uneven
Solution Approach 1:
The patent applies dimensionality change by transitioning from a two-dimensional planar wiring layout to a three-dimensional stacked wiring structure. Multiple wiring layers are arranged vertically above the photodiode, allowing circuits to be configured in the depth dimension rather than competing for horizontal space. This enables sufficient opening area to be maintained while accommodating complex multilayer wiring for high-speed processing.
Solution Approach 2:
The patent segments the wiring structure into multiple independent layers, with each layer serving specific functions (signal lines, power lines, ground lines). This segmentation allows optimized placement of different wiring types in different vertical positions, improving both light reception by reducing horizontal wiring obstruction and processing capability by providing dedicated wiring paths for each function.
2Manufacturing precision
If opening position is fixed according to light incidence angle to reduce shading, then light reception uniformity is improved, but optical system versatility is limited
Solution Approach 1:
The patent resolves this contradiction by moving the wiring structure to three-dimensional space above the photodiode. Instead of adjusting the opening position in the two-dimensional plane according to incidence angle, the stacked wiring layers are positioned vertically, allowing light to pass through the opening to the photodiode without being blocked by horizontal wiring. This enables uniform light reception across different incidence angles while maintaining compatibility with various optical systems.
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
This configuration reduces light unevenness and shading effects, ensuring consistent sensitivity across pixels and expanding the range of applicable lenses without limiting the optical system's versatility.
Implementation Method 1
photoelectric conversion of incident light is performed by a photodiode (PD)
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A photoelectric conversion element (11, 40) comprises: a plurality of photodetectors (PD) that perform photoelectric conversion per pixel to output an analog image signal, and that are arranged on a straight line; and wirings that are formed on a wiring layer (M1, M2), and that are enabled to be used as at least one of a signal line used in a peripheral circuit of the photodetector (PD), a power source, and a ground, wherein the photodetector (PD) is formed to have a first shaded region and a second shaded region in which light is shaded by the wirings that are positioned on the straight line sandwiching an opening, respectively, when light that has passed through the opening that opens being sandwiched by the wirings positioned on the straight line is incident perpendicularly on a light receiving surface photodetector (PD).