Stacked Image Sensor Charge Drain Layout for Clean OB Signals

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Solution Overview

Problem

Existing photoelectric conversion apparatuses fail to accurately prevent surplus electric charges from entering the optical black (OB) region, which affects the detection of black level reference signals, especially when photoelectric conversion units with larger light-shielded regions are present.

Innovation Solution

A laminated photoelectric conversion apparatus is designed with a first semiconductor element layer containing photoelectric conversion units and a second semiconductor element layer with signal processing circuits, where an outer periphery region with a semiconductor region of the same conductivity type as the signal electric charges is provided to discharge surplus electric charges, preventing them from entering the OB region.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If electric charge discharge pixels are disposed between the effective pixel region and the OB region to discharge signal electric charges leaking from the effective pixel region, then the black level reference signal detection accuracy is improved, but surplus electric charges entering the OB region from the periphery of the OB region still affect the black level reference signal

Engineering Contradiction:

Improveblack level reference signal detection accuracyVSAvoidblack level reference signal stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent divides the OB region into multiple segments: the original OB region for receiving leaked signal charges, and a newly added outer periphery OB region for receiving surplus charges from the periphery. This segmentation allows each region to handle specific charge sources independently, preventing interference between different charge types and improving overall black level reference signal stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary region (outer periphery OB region) between the periphery area and the main OB region. This intermediary captures surplus electric charges before they can enter the main OB region, acting as a buffer that protects the black level reference signal from contamination by peripheral surplus charges.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the OB region is enlarged to capture more leaked signal charges, then the detection accuracy is improved, but the OB region becomes more susceptible to contamination by surplus electric charges from the periphery

Engineering Contradiction:

Improvesignal electric charge detection accuracyVSAvoidsurplus electric charge contamination

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The OB region is segmented into an inner OB region and an outer periphery OB region. The inner region maintains its function of capturing leaked signal charges, while the outer region specifically handles surplus charges from the periphery. This segmentation allows the OB region to be enlarged without increasing susceptibility to peripheral contamination, as the outer region acts as a protective buffer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts the harmful effect of peripheral surplus charges into a beneficial function by creating a dedicated outer periphery OB region to capture these charges. What was originally a harmful contamination source becomes a controlled feature that protects the main OB region, transforming the problem into a solution.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 prevents surplus electric charges from entering the OB region, enabling more accurate detection of black level reference signals and improving the overall performance of the photoelectric conversion apparatus.

Implementation Method 1

the outer periphery region is provided with an electric charge discharge region including a semiconductor region of the same conductivity type as signal electric charges, and the electric charge discharge region is supplied with a fixed potential

Methodology Applied

Scientific EffectElectric charge discharge: Conduction (electrical)

Implementation Method 2

a first substrate having a first semiconductor element layer including a plurality of photoelectric conversion units

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS20240355857A1Photoelectric conversion apparatus, photoelectric conversion system, and moving object

Publication Date: 2024.10.24 CANON KK

AI summary

A photoelectric conversion apparatus includes a first substrate having a first semiconductor element layer including a plurality of photoelectric conversion units, and a second substrate having a second semiconductor element layer. The first and second substrates are laminated. The first semiconductor element layer has an effective pixel region, an optical black (OB) pixel region, and an outer periphery region. The effective pixel region includes a photoelectric conversion unit having a larger light-shielded area than other photoelectric conversion units out of the plurality of photoelectric conversion units. The OB pixel region overlaps with a light-shielding region, but the outer periphery region does not overlap with the light-shielding region in a planar view. The outer periphery region is provided with an electric charge discharge region including a semiconductor region of the same conductivity type as signal electric charges. The electric charge discharge region is supplied with a fixed potential.