Metal Gate Structure With Isolation Protection During Recess Etching
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Solution Overview
Problem
In the fabrication of multi-gate FET devices, the formation of recesses for epitaxial source/drain structures poses challenges due to high aspect ratios, leading to isolation loss, potential poly collapse, and improper epitaxial structure formation.
Innovation Solution
A protection layer is formed over the isolation structure to prevent consumption or damage during recess formation, thereby mitigating isolation loss and reducing the risks of poly collapse and improper epitaxial structure growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If recesses are formed for epitaxial source/drain structures in multi-gate FET devices, then the device can achieve proper source/drain formation, but the high aspect ratio of the recesses causes isolation loss, poly collapse, and improper epitaxial structure formation
Solution Approach 1:
The patent applies preliminary action by forming the protection layer over the isolation structure before forming the recesses. This advance protective measure prevents isolation loss during the subsequent recess formation process, eliminating the need for isolation repair steps and ensuring structural integrity throughout fabrication.
Solution Approach 2:
The protection layer serves as an intermediary element between the isolation structure and the recess formation process. This intermediate layer prevents direct harmful interactions between the etching process and the isolation structure, thereby preventing isolation loss and poly collapse while allowing proper recess formation.
2Ease of manufacture
If recesses with high aspect ratios are formed, then epitaxial source/drain structures can be accommodated, but poly collapse occurs due to loss of support
Solution Approach 1:
The protection layer is formed in advance over the isolation structure before recess formation begins. This preliminary protective measure ensures that the isolation structure maintains its integrity during the high-aspect-ratio recess formation process, preventing poly collapse and ensuring gate structure stability throughout manufacturing.
Solution Approach 2:
The protection layer acts as an intermediary that transfers the mechanical support function from the isolation structure to the recess formation process. By intervening between the etching process and the isolation structure, it prevents the loss of support that would otherwise cause poly collapse.
3Productivity
If recesses are formed without protection, then the fabrication process can proceed quickly, but isolation loss and improper epitaxial growth occur
Solution Approach 1:
The protection layer is formed as a preliminary step before recess formation and epitaxial growth. This advance preparation prevents isolation loss and ensures proper epitaxial structure formation, eliminating the need for subsequent repair steps and actually improving overall fabrication efficiency while maintaining high precision.
Solution Approach 2:
The protection layer serves as an intermediary that enables the fabrication process to proceed smoothly without compromising quality. It mediates between the recess formation process and the isolation structure, preventing harmful interactions that would otherwise require process interruptions and repairs.
Data Source
AI summary
A semiconductor structure includes an isolation structure in a substrate, a metal gate structure over the substrate and a portion of the isolation structure, a spacer at sidewalls of the metal gate structure, epitaxial source/drain structure at two sides of the metal gate structure, and a protection layer over the isolation structure. The protection layer and the spacer include a same material.