Backside Illuminated Image Sensor Grid Structure

Solution Overview

Problem

Existing image sensor device structures face challenges in minimizing light loss and optical cross-talk due to separate formation of deep trench isolation and grid structures, which can lead to deformation issues during bonding and alignment problems, affecting the accuracy and efficiency of the fabrication process.

Innovation Solution

The deep trench isolation structure is formed in a single step as a continuous structure extending through the substrate, serving both as an isolation and grid structure, eliminating gaps and alignment concerns, and is integrated in the front-end-of-line process before bonding, ensuring minimal light loss and improved optical performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If separate formation of deep trench isolation and grid structures is used, then manufacturing flexibility is maintained, but alignment accuracy deteriorates and fabrication time increases

Engineering Contradiction:

Improvealignment accuracyVSAvoidstructure formation complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines the deep trench isolation structure and grid structure into a single integrated structure formed in one step. The isolation structure extends through the substrate and protrudes on the back surface, while the grid structure is formed simultaneously using the same isolation material, eliminating the need for separate formation processes and improving alignment accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The isolation structure serves dual functions: it provides electrical isolation between adjacent pixel regions and simultaneously acts as the grid structure for light guidance. This multi-functional design reduces the number of separate structures needed and simplifies the overall device architecture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If separate formation of deep trench isolation and grid structures is used, then structural independence is maintained, but fabrication time and cost increase

Engineering Contradiction:

Improvefabrication efficiencyVSAvoidfabrication time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent combines the deep trench isolation structure and grid structure into a single integrated structure formed in one step. The isolation structure extends through the substrate and protrudes on the back surface, while the grid structure is formed simultaneously using the same isolation material, eliminating the need for separate formation processes and improving alignment accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The isolation structure is formed to extend through the substrate and protrude on the back surface before subsequent processing steps. This preliminary formation of the protruding portion provides a pre-defined template for the grid structure, enabling simultaneous formation and eliminating later alignment operations.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If gaps exist between isolation and grid structures, then separate formation is simplified, but light loss and optical cross-talk increase

Engineering Contradiction:

Improvestructure formation easeVSAvoidlight loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent combines the deep trench isolation structure and grid structure into a single integrated structure formed in one step. The isolation structure extends through the substrate and protrudes on the back surface, while the grid structure is formed simultaneously using the same isolation material, eliminating the need for separate formation processes and improving alignment accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent converts the potential harm of gaps between separate structures (which cause light loss and cross-talk) into a benefit by creating a continuous integrated structure. The protruding portion of the isolation structure serves as both the isolation barrier and the grid pattern, ensuring continuous material coverage that prevents light leakage while maintaining ease of formation through a single process step.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS10163952B2Backside illuminated image sensor device structure

Publication Date: 2018.12.25 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method for forming a backside illuminated (BSI) image sensor device structure is provided. The BSI image sensor includes a first substrate having a top surface and a bottom surface, and a plurality of pixel regions formed at the top surface of the first substrate. The BSI image sensor also includes a grid structure through the first substrate and between two adjacent pixel regions. The grid structure extends continuously through the first substrate in a vertical direction and has a top surface and a bottom surface, the top surface of the grid structure protrudes above the bottom surface of the first substrate, and the bottom surface is leveled with the top surface of the first substrate.