Solid-State Imaging Device Charge Discharge via Deep Light Receiving Portion
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Solution Overview
Problem
In solid-state imaging devices, excess electric charge generated in light receiving portions can cause color mixture and reduce saturation output and sensitivity, especially when the infrared light receiving portion extends below the visible light receiving portion, requiring a surface-side drain that narrows the light receiving portion and reduces sensitivity.
Innovation Solution
The device incorporates shallow and deep light receiving portions connected to form a second light receiving portion, allowing excess electric charge to be discharged to the deep portion without the need for a surface-side drain, thereby reducing color mixture and maintaining sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a drain is formed on the surface side of the substrate to discharge excess electric charge, then color mixture is reduced, but the light receiving portion becomes narrower and sensitivity decreases
Solution Approach 1:
The patent resolves the contradiction by moving the charge discharge function from the surface dimension to the depth dimension. The deep light receiving portion extends below the shallow light receiving portion to provide a discharge path for excess electric charge. This vertical extension allows charge discharge without requiring a surface drain, thereby maintaining the full width of the shallow light receiving portion and preserving sensitivity while still preventing color mixture.
2Manufacturing precision
If the light receiving portion is made wider to increase sensitivity, then saturation output improves, but excess electric charge cannot be properly discharged
Solution Approach 1:
The patent extends the light receiving portion in the vertical dimension (depth) rather than the horizontal dimension (width). The deep light receiving portion provides additional volume for charge discharge while keeping the shallow light receiving portion width maximized for high sensitivity. This dimensional separation allows both wide light receiving area and adequate charge discharge capacity.
3Reliability
If a surface-side drain is added to discharge excess charge, then image quality improves, but device complexity increases
Solution Approach 1:
The patent merges the charge discharge function with the deep light receiving portion structure. Instead of adding a separate surface drain component, the deep light receiving portion itself serves dual purposes: receiving infrared light and providing a discharge path for excess electric charge from the shallow light receiving portion. This integration eliminates the need for additional surface drain structures and simplifies the overall device architecture.
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 effectively discharges excess electric charge, reducing color mixture and maintaining high sensitivity and saturation output, even when infrared light receiving portions extend below visible light receiving portions, without the need for a surface-side drain, thus improving image quality.
Implementation Method 1
a photodiode photoelectrically converting infrared light extends to a lower part of a photodiode photoelectrically converting visible light
Data Source
AI summary
A solid-state imaging device includes a plurality of pixels two-dimensionally arranged on a semiconductor substrate. Each of the pixels includes at least one shallow light receiving portion formed near a surface of the semiconductor substrate and at least one deep light receiving portion formed under the shallow light receiving portion. One or more of the shallow light receiving portions and the deep light receiving portion are connected to each other so as to form a second light receiving portion. The rest of the shallow light receiving portions forms a first light receiving portion. Excess electric charge in the first light receiving portion is discharged to the deep light receiving portion.