MOSFET Epitaxial Layer Protection During FinFET Etching
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Solution Overview
Problem
During the formation of FinFET structures, the source/drain portion, including a cap layer and an epitaxial layer, is often damaged by etching processes, leading to potential gate metal leakage and operational failure due to direct contact between the silicon fin and the epitaxial silicon definition layer.
Innovation Solution
A method involving the use of a protection layer, such as germanium or silicon-germanium, is employed to safeguard the epitaxial layer by forming a trench and depositing this layer within it, which can withstand subsequent etching processes, thereby preventing damage to the epitaxial layer and ensuring the integrity of the FinFET structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If etching processes are used during FinFET formation, then the gate metal layer can be formed, but the source/drain portion including the epitaxial layer is damaged leading to leakage and operational failure
Solution Approach 1:
A protection layer is formed over the epitaxial layer before the etching process begins. This protection layer serves as a sacrificial barrier that prevents the etchant from directly contacting and damaging the epitaxial layer during subsequent gate metal formation processes
Solution Approach 2:
The protection layer acts as an intermediary between the etching process and the epitaxial layer. It absorbs the harmful effects of the etchant, allowing the etching to proceed for gate metal formation while the protection layer degrades instead of the critical epitaxial layer
2Ease of manufacture
If the source/drain portion is exposed to multiple etching processes, then the gate structure can be formed, but direct contact between silicon fin and epitaxial silicon definition layer occurs causing gate metal leakage
Solution Approach 1:
The protection layer is deposited in advance before any etching operations. This preliminary protective measure ensures that when multiple etching processes are subsequently performed to form the gate structure, the epitaxial layer remains intact and properly positioned
Solution Approach 2:
The protection layer provides beforehand cushioning against the cumulative damage from multiple etching processes. It absorbs the mechanical and chemical stress that would otherwise compromise the precise interface between the silicon fin and epitaxial layer
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
The protection layer effectively shields the epitaxial layer from damage during etching, maintaining operational accuracy and preventing leakage, thus ensuring the reliability of the FinFET structure.
Implementation Method 1
depositing this layer within it, which can withstand subsequent etching processes
Data Source
AI summary
Devices are described herein that include an epitaxial layer, a cap layer above the epitaxial layer, a gate layer adjacent to the epitaxial layer on which an etching process is performed, a trench above the cap layer, and a source/drain portion includes the epitaxial layer.