Buffer Oxide Layer Protects Metallization in BSI Image Sensor Etching

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Solution Overview

Problem

Existing methods for fabricating back side illuminated (BSI) image sensor devices face challenges due to the thick patternable layer required, which can lead to damage of metallization layers during the etching process, causing issues like air bubbles and penetration of etchants, resulting in incomplete removal and potential damage to the interconnection structure.

Innovation Solution

A one patterning/two etching (1P2E) process is employed, where a buffer oxide layer is used to protect the metallization layer, allowing for the thorough removal of the patternable layer without damaging the underlying metallization layers, by first forming recesses and then etching through them to expose the pad structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a thick patternable layer is used to ensure complete coverage, then the patternable layer can be formed over the entire structure, but the metallization layers are damaged during etching due to air bubbles and etchant penetration

Engineering Contradiction:

Improvepatternable layer coverageVSAvoidmetallization layer integrity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

A buffer oxide layer is introduced as an intermediary protective layer between the patternable layer and the metallization layers. This buffer oxide layer prevents direct contact between the etchant and metallization layers, eliminating air bubble formation and etchant penetration while maintaining complete patternable layer coverage.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The buffer oxide layer is formed in advance before depositing the patternable layer. This preliminary protective layer ensures that when the patternable layer is later removed through etching, the metallization layers are already protected and cannot be damaged by the etchant or air bubbles.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If the patternable layer is thoroughly removed to expose pad structures, then complete removal is achieved, but the metallization layers are exposed to damage from etchants and air bubbles

Engineering Contradiction:

Improvepatternable layer removal completenessVSAvoidetchant and air bubble damage

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The buffer oxide layer serves as a protective intermediary that allows complete removal of the patternable layer while preventing harmful etchants and air bubbles from reaching and damaging the metallization layers underneath.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The buffer oxide layer provides beforehand cushioning protection to the metallization layers. It absorbs and prevents the harmful effects of etchants and air bubbles before they can reach the sensitive metallization structures, ensuring complete patternable layer removal without damage.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Productivity

If etching is performed to remove the patternable layer, then the pad structures can be accessed, but air bubbles form and penetrate causing incomplete removal and potential damage

Engineering Contradiction:

Improvepad structure accessibilityVSAvoidinterconnection structure integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The buffer oxide layer acts as a mediator that enables the etching process to proceed completely for pad structure accessibility while simultaneously preventing air bubbles and etchants from penetrating to and damaging the interconnection structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The buffer oxide layer provides prior cushioning protection during the etching process. It prevents air bubbles from forming and penetrating to the metallization layers, ensuring complete patternable layer removal for pad accessibility without compromising interconnection structure integrity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 method effectively prevents damage to the metallization layers during the removal of the patternable layer, ensuring complete removal without compromising the interconnection structure, thus improving the fabrication process of BSI image sensor devices.

Implementation Method 1

a buffer oxide layer is used to protect the metallization layer, allowing for the thorough removal of the patternable layer without damaging the underlying metallization layers

Methodology Applied

Scientific EffectPhysical barrier protection:

Data Source

PatentUS20220367559A1Method for forming image sensor devices

Publication Date: 2022.11.17 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes forming a dielectric layer over a first surface of a semiconductor layer, the dielectric layer including a metallization layer. The method includes forming an opening to expose a portion of the dielectric layer. The method includes forming a buffer oxide layer lining the opening. The method includes forming, according to a patternable layer, a recess in the buffer oxide layer partially extending from a second surface of the buffer oxide layer. The method includes removing the patternable layer. The method includes extending the recess through the buffer oxide layer and a portion of the dielectric layer to expose a portion of the metallization layer. The method includes filling the recess with a conductive material to form a pad structure configured to provide electrical connection to the metallization layer.