Global Shutter Pixel Storage Shielding Against Charge Damage

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Solution Overview

Problem

Existing image sensors with global shutters face challenges in efficiently capturing fast-moving objects due to limitations in the design and manufacturing of storage devices within the pixel units.

Innovation Solution

The proposed image sensor design includes a storage device with a memory element, a first dielectric layer, and a light shielding element, where the light shielding element is electrically isolated from the memory element and overlaps with the perimeter of the storage transistor gate, effectively shielding the storage device from incident light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a memory element is added to each pixel to enable global shutter function, then the ability to capture fast-moving objects is improved, but the device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improveglobal shutter capabilityVSAvoidpixel structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The light shielding element is nested within the pixel structure, positioned between the lens and the memory element. This nested configuration allows the light shielding element to be integrated into the existing pixel architecture without requiring separate external components, thereby enabling global shutter capability while managing device complexity through compact integration.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The light shielding element acts as an intermediary component that mediates between the incident light and the memory element. By positioning this intermediate structure, the patent prevents harmful light from directly reaching the memory element during non-exposure periods, thus protecting stored image charges while maintaining the global shutter function.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Illumination intensity

If the storage device is exposed to incident light, then the memory element can capture more light for better image quality, but the stored image charges are damaged by unintended light exposure

Engineering Contradiction:

Improvelight capture for image qualityVSAvoidlight-induced charge damage

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The light shielding element performs preliminary anti-action by blocking incident light before it can reach the memory element during non-exposure periods. This preventive measure is implemented in advance of any potential charge damage, ensuring that stored image charges remain intact by preemptively stopping harmful light exposure.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The light shielding element provides localized protection specifically to the memory element and storage device region, while allowing other parts of the pixel structure to remain exposed to light as needed. This selective shielding approach ensures that only the sensitive charge storage areas are protected, maintaining local quality control over light exposure.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If a light shielding element is added to protect the storage device, then the accuracy of captured image data is improved, but the device complexity and manufacturing precision requirements increase

Engineering Contradiction:

Improveimage data accuracyVSAvoidalignment precision between light shielding element and storage device

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The light shielding element is merged with the color filter structure, forming an integrated component rather than a separate element. This merging approach allows the light shielding function to be combined with the existing color filter layer, thereby improving image data accuracy through better light control while reducing manufacturing precision requirements by eliminating the need for separate alignment processes.

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 ability to capture accurate image data by preventing damage to stored image charges from incident light, thereby improving the overall performance of the image sensor in capturing fast-moving objects.

Implementation Method 1

the light shielding element is overlapped with at least a part of a perimeter of the storage transistor gate in a vertical projection on a plane along a stacking direction of the memory element and the light shielding element

Methodology Applied

Scientific EffectLight shielding: Absorption (EM radiation)

Data Source

PatentUS12218159B2Image sensor and manufacturing method thereof

Publication Date: 2025.02.04 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An image sensor includes a storage device, where the storage device includes a memory element, a first dielectric layer and a light shielding element. The memory element includes a storage node and a storage transistor gate, where the storage transistor gate is located over the storage node. The first dielectric layer is located over a portion of the storage transistor gate. The light shielding element is located on the first dielectric layer and includes a semiconductor layer. The semiconductor layer is electrically isolated from the memory element, where the light shielding element is overlapped with at least a part of a perimeter of the storage transistor gate in a vertical projection on a plane along a stacking direction of the memory element and the light shielding element, and the stacking direction is normal to the plane.