Image Sensor Pixel Structure for Dual-Direction Focus Detection

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Solution Overview

Problem

Existing image sensors face challenges in increasing saturation charge amount while maintaining the number of pupil division directions for focus detection, leading to high manufacturing costs and reduced light reception area due to the use of transfer transistors or complex vertical transfer transistors.

Innovation Solution

An image sensor design featuring a pixel array with microlenses, where pairs of regions at different depths are arranged orthogonally to each other, connected by N-type connecting regions, allowing for phase difference focus detection using pupil division signals without the need for multiple transfer transistors, thereby simplifying the configuration and increasing saturation charge capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a transfer transistor is provided for each photoelectric conversion portion formed at different depths, then the saturation charge amount increases, but the number of transfer transistors becomes large and the area of the light receiving region becomes small, leading to high manufacturing cost

Engineering Contradiction:

Improvesaturation charge amountVSAvoidnumber of transfer transistors

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

Multiple photoelectric conversion portions formed at different depths share a common transfer transistor instead of each having its own transfer transistor. This merging approach reduces the total number of transfer transistors while still enabling charge transfer from all photoelectric conversion portions, thereby increasing the saturation charge amount without proportionally increasing device complexity and manufacturing cost.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The common transfer transistor serves multiple photoelectric conversion portions simultaneously, performing a universal function for charge transfer across different depths. This multi-functional design allows a single transistor to handle charges from multiple photoelectric conversion portions, reducing the overall transistor count while maintaining the ability to transfer sufficient charge for imaging.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Quantity of substance

If a vertical transfer transistor is used to transfer signals from multiple photoelectric conversion portions, then the saturation charge amount increases, but the manufacturing cost increases due to the complicated process for forming the transistor

Engineering Contradiction:

Improvesaturation charge amountVSAvoidmanufacturing cost

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The patent combines multiple photoelectric conversion portions at different depths to share a common transfer transistor, avoiding the need for complex vertical transfer transistor structures. This merging approach achieves increased saturation charge amount while using standard planar transistor fabrication processes, thereby reducing manufacturing cost and simplifying the manufacturing process.

Inventive Principle:

Principle #5Merging (Combining)

3Quantity of substance

If the number of transfer transistors is increased to increase saturation charge amount, then the saturation charge amount increases, but the area of the light receiving region becomes small

Engineering Contradiction:

Improvesaturation charge amountVSAvoidarea of the light receiving region

Core Design Contradiction:

Quantity of substanceVSArea of stationary object

Solution Approach 1:

By merging multiple photoelectric conversion portions to share a common transfer transistor, the patent reduces the total area occupied by transfer transistors. This allows more area to be allocated to the light receiving regions of the photoelectric conversion portions themselves, thereby increasing the effective light receiving area while still achieving increased saturation charge amount through the combined charge capacity of multiple photoelectric conversion portions.

Inventive Principle:

Principle #5Merging (Combining)

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 design enhances the saturation charge amount while maintaining two pupil division directions for focus detection, reducing manufacturing costs and improving light reception efficiency without the complexity of multiple transfer transistors.

Implementation Method 1

a plurality of microlenses; and a pixel array having, with respect to each of the microlenses

Methodology Applied

Scientific EffectLight focusing: Lens

Implementation Method 2

photoelectric conversion portions formed at different depths to photoelectrically convert visible light in different wavelength ranges

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS11825196B2Image sensor and image capturing apparatus

Publication Date: 2023.11.21 CANON KK

AI summary

An image sensor comprising a plurality of microlenses, and a pixel array having, with respect to each of the microlenses, a pair of first regions formed at a first depth from a surface on which light is incident, a pair of second regions formed at a second depth deeper than the first depth, and a plurality of connecting regions that connects the pair of first regions and the pair of second regions, respectively. A direction of arranging the pair of second regions corresponding to each microlens is a first direction, and a direction of arranging the pair of first regions is either the first direction or a second direction which is orthogonal to the first direction.