CMOS Image Sensor Charge Transfer Through a Shared Gate Opening

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Solution Overview

Problem

CMOS image sensors face challenges in efficiently transferring charges from photodiodes to analog memories while maintaining light shielding properties to prevent new charge generation due to photoelectric conversion.

Innovation Solution

The imaging device incorporates a photoelectric conversion section and a charge holding section laminated in the thickness direction of a semiconductor substrate, with a horizontal light shielding film interposed between them. Additionally, a plurality of vertical gate electrodes pass through an identical opening in the horizontal light shielding film and extend to the photoelectric conversion section, optimizing charge transfer efficiency and reducing the area occupied by these components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple vertical gate electrodes are formed through separate openings in the horizontal light shielding film, then charge transfer efficiency is improved, but the area occupied by the gate electrodes and openings increases

Engineering Contradiction:

Improvecharge transfer efficiencyVSAvoidarea occupied by gate electrodes and openings

Core Design Contradiction:

ProductivityVSArea of stationary object

Solution Approach 1:

Multiple vertical gate electrodes are merged into a single opening in the horizontal light shielding film. The gate electrodes are arranged side-by-side within the same opening, allowing charge transfer from multiple photodiodes while occupying less area than separate openings would require. This merging approach resolves the contradiction by maintaining charge transfer efficiency while reducing the total area occupied.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Multiple vertical gate electrodes are nested within a single opening structure. The electrodes are positioned adjacent to each other inside the same opening, creating a nested arrangement where multiple functional elements share a common structural envelope. This nesting reduces the overall area required while preserving the charge transfer functionality of each electrode.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Area of stationary object

If the charge holding section is provided laminated over the photoelectric conversion section, then the photodiode area is maintained, but light shielding becomes more critical to prevent new charge generation

Engineering Contradiction:

Improvephotodiode areaVSAvoidphotoelectric conversion in charge holding section

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

A horizontal light shielding film is introduced as an intermediary layer between the photoelectric conversion section and the charge holding section. This intermediate structure blocks light from reaching the charge holding section, preventing unwanted photoelectric conversion while allowing the photodiode area to be maintained for efficient charge generation. The light shielding film acts as a mediator that resolves the contradiction between maintaining photodiode area and preventing harmful photoelectric conversion.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enhances the efficiency of charge transfer from the photoelectric conversion section to the charge holding section, while maintaining effective light shielding properties, thereby improving the overall performance of the CMOS image sensor.

Implementation Method 1

a photoelectric conversion section provided in a semiconductor substrate

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 2

a horizontal light shielding film that is provided between the photoelectric conversion section and the charge holding section

Methodology Applied

Scientific EffectLight shielding: Absorption (EM radiation)

Data Source

PatentUS12211866B2Imaging device

Publication Date: 2025.01.28 SONY SEMICON SOLUTIONS CORP

AI summary

An imaging device according to an embodiment of the present disclosure includes a photoelectric conversion section provided in a semiconductor substrate, a charge holding section that is provided as being laminated over the photoelectric conversion section in a thickness direction of the semiconductor substrate and holds a charge photoelectrically converted by the photoelectric conversion section, a horizontal light shielding film that is provided between the photoelectric conversion section and the charge holding section and extends in an in-plane direction of the semiconductor substrate, and a plurality of vertical gate electrodes that passes through an identical opening provided in the horizontal light shielding film and extends to the photoelectric conversion section in the thickness direction of the semiconductor substrate.