Solid-State Image Sensor Asymmetric Well Contact Layout

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Solution Overview

Problem

Existing solid-state image sensors lack an effective method for advantageous placement of well contact regions, which is crucial for focus detection functionality, leading to inefficiencies in phase-difference detection and potential issues with shading and dark currents.

Innovation Solution

A solid-state image sensor design that includes a semiconductor substrate with photoelectric converters and well contact regions for focus detection pixels, where the relative positions of these regions differ to improve layout flexibility and reduce dark currents, while using light shielding portions to define distinct regions for pupil division-based focus detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If well contact regions are placed in conventional positions in focus detection pixels, then the sensor structure is simple, but layout flexibility is reduced and dark currents increase

Engineering Contradiction:

Improvelayout flexibilityVSAvoidsensor structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by placing well contact regions at different relative positions in first focus detection pixels versus second focus detection pixels. Specifically, in first focus detection pixels, the well contact region is positioned at a first relative position with respect to the photoelectric converter, while in second focus detection pixels, it is positioned at a second relative position. This asymmetric arrangement provides layout flexibility for pupil division-based focus detection while maintaining a relatively simple sensor structure without requiring fundamental design changes.

Inventive Principle:

Principle #4Asymmetry

2Adaptability or versatility

If well contact regions are positioned to improve layout freedom, then focus detection capability is enhanced, but shading effects and dark currents may increase

Engineering Contradiction:

Improvelayout freedomVSAvoidshading effects and dark currents

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by making the well contact region position pixel-type-dependent. First focus detection pixels have the well contact region at a first relative position, while second focus detection pixels have it at a second relative position. This localized differentiation optimizes each pixel type's performance characteristics, reducing dark currents and shading effects in specific regions while maintaining overall layout freedom for focus detection functionality.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If conventional well contact region placement is used, then manufacturing is straightforward, but phase-difference detection efficiency is reduced

Engineering Contradiction:

Improvephase-difference detection efficiencyVSAvoidwell contact region placement

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent implements asymmetry in well contact region placement where first focus detection pixels use a first relative position and second focus detection pixels use a second relative position. This asymmetric configuration enhances phase-difference detection efficiency by optimizing light path separation while maintaining compatibility with standard manufacturing processes, as the different positions can be implemented through conventional photolithography patterning without requiring complex additional manufacturing steps.

Inventive Principle:

Principle #4Asymmetry

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

Enhances focus detection capabilities by improving layout freedom and reducing dark currents, thereby enhancing image quality and suppressing shading effects.

Implementation Method 1

a semiconductor substrate including photoelectric converters of the plurality of image sensing pixels, a photoelectric converter and a first well contact region of the first focus detection pixel, and a photoelectric converter and a second well contact region of the second focus detection pixel

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

a first light shielding portion configured to define the first region and shield the first well contact region from light; a second light shielding portion configured to define the second region and shield the second well contact region from light

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS9881950B2Solid-state image sensor and camera with light-shielding portions and amplification transistors

Publication Date: 2018.01.30 CANON KK

AI summary

The solid-state image sensor includes image sensing pixels, first and second focus detection pixels configured to respectively detect lights passing through different regions of a pupil of an image sensing lens. The sensor includes a semiconductor substrate including photoelectric converters of the image sensing pixels, a photoelectric converter and a first well contact region of the first focus detection pixel, and a photoelectric converter and a second well contact region of the second focus detection pixel, a first contact plug electrically connected to the first well contact region, and a second contact plug electrically connected to the second well contact region. The relative position of the first well contact region in the first focus detection pixel differs from a relative position of the second well contact region in the second focus detection pixel.