Controllable Isolation Grid Bias for Image Sensor Cross-Talk

Solution Overview

Problem

In image sensors with small pixel sizes, cross-talk between pixels remains significant, and there is a trade-off between reducing cross-talk and increasing quantum efficiency due to the application of bias voltage on the in-substrate metal grid, which limits performance.

Innovation Solution

The in-substrate metal grid is coupled to a contact pad for external analog control of the bias voltage, allowing dynamic adjustment of the trade-off between cross-talk reduction and quantum efficiency based on application, environment, or mode of operation, using conductive structures that bypass the front side of the substrate and integrate with standard contact pads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If bias voltage is applied on the in-substrate metal grid to reduce cross-talk, then cross-talk between pixels is reduced, but quantum efficiency decreases

Engineering Contradiction:

Improvecross-talkVSAvoidquantum efficiency

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent implements dynamic control of the bias voltage on the in-substrate metal grid by coupling it to a contact pad that accepts external analog control signals. This allows the bias voltage to be adjusted in real-time based on operating conditions, enabling the system to optimize the trade-off between cross-talk reduction and quantum efficiency dynamically rather than being fixed. The metal grid structure with external controllability transforms the static isolation approach into a dynamic one, where the isolation strength can be modulated according to specific application requirements, environmental conditions, or operational modes.

Inventive Principle:

Principle #15Dynamics

2Area of stationary object

If smaller pixel sizes are used to increase integration, then device size is reduced, but cross-talk between pixels increases

Engineering Contradiction:

Improvedevice sizeVSAvoidcross-talk

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by implementing an in-substrate metal grid that provides localized isolation between adjacent pixels. Rather than uniformly increasing isolation across the entire sensor (which would consume more space), the metal grid is positioned specifically at the boundaries between pixels where cross-talk occurs. This localized approach to isolation allows small pixel sizes to be maintained while providing targeted cross-talk suppression only where needed, preserving the benefits of high integration without the penalty of increased inter-pixel interference.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If fixed bias voltage is applied to reduce cross-talk, then cross-talk is reduced, but adaptability to different operating conditions is lost

Engineering Contradiction:

Improvecross-talkVSAvoidadaptability

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic control of the bias voltage on the in-substrate metal grid by coupling it to a contact pad that accepts external analog control signals. This allows the bias voltage to be adjusted in real-time based on operating conditions, enabling the system to optimize the trade-off between cross-talk reduction and quantum efficiency dynamically rather than being fixed. The metal grid structure with external controllability transforms the static isolation approach into a dynamic one, where the isolation strength can be modulated according to specific application requirements, environmental conditions, or operational modes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent enables continuous variation of the bias voltage parameter on the in-substrate metal grid through external analog control. By changing the voltage parameter dynamically, the system can adapt to different operating conditions such as varying light levels, temperature conditions, or specific application requirements. This parameter change capability allows optimization of both cross-talk reduction and quantum efficiency for different scenarios, providing versatility that a fixed voltage configuration cannot achieve.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20240379710A1Csi with controllable isolation structure and methods of manufacturing and using the same

Publication Date: 2024.11.14 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A metal grid within a trench isolation structure on the back side of an image sensor is coupled to a contact pad so that a voltage on the metal grid is continuously variable with a voltage on the contact pad. One or more conductive structures directly couple the metal grid to a contact pad. The conductive structures may bypass a front side of the image sensor. A bias voltage on the metal grid may be varied through the contact pad whereby a trade-off between reducing cross-talk and increasing quantum efficiency may be adjusted dynamically in accordance with the application of the image sensor, its environment of use, or its mode of operation.