FinFET Source/Drain Contact Layout Using CESL Surface Exposure
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, challenges arise in integrating more components into a given area, including issues with contact formation and the need to expose additional surfaces of epitaxial source/drain regions for better contact formation without damaging underlying shallow trench isolation regions.
Innovation Solution
A contact etch stop layer (CESL) is formed before epitaxial source/drain regions, allowing for over-etching of inter-layer dielectric layers during contact formation, which exposes more surfaces of the epitaxial source/drain regions without damaging the shallow trench isolation regions, thereby increasing the surface area available for contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional contact formation is used without CESL, then the process is simpler, but the surface area of epitaxial source/drain regions exposed for contacts is insufficient
Solution Approach 1:
A contact etch stop layer (CESL) is formed prior to epitaxial source/drain region formation. This preliminary layer enables subsequent over-etching of inter-layer dielectric layers to expose additional surfaces of the epitaxial source/drain regions without damaging underlying shallow trench isolation regions, thereby increasing the contact surface area.
Solution Approach 2:
The CESL acts as an intermediary layer between the inter-layer dielectric and the shallow trench isolation region. It allows the etch process to selectively remove dielectric material while stopping before damaging the isolation region, enabling controlled exposure of epitaxial source/drain surfaces.
2Area of moving object
If over-etching is performed to expose more surfaces, then contact surface area increases, but underlying shallow trench isolation regions may be damaged
Solution Approach 1:
The CESL is deposited before epitaxial growth, creating a protective barrier that will later enable selective removal of dielectric material without exposing the underlying isolation region to damaging etch conditions.
Solution Approach 2:
The CESL serves as a protective intermediary layer during the contact etch process. It allows the etch to proceed through the inter-layer dielectric and expose epitaxial source/drain surfaces while preventing etch damage to the shallow trench isolation regions beneath.
3Productivity
If feature sizes are reduced to increase integration density, then more components fit in given area, but contact formation becomes more difficult
Solution Approach 1:
The CESL is formed in advance before epitaxial growth and contact patterning. This preliminary structure enables subsequent processing steps to achieve adequate contact surface area even as overall device dimensions are reduced for higher integration density.
Solution Approach 2:
The invention addresses contact surface area limitations by utilizing vertical dimensionality through the CESL structure and over-etching process, rather than relying solely on lateral dimensions. This allows contact surface area to be increased without increasing the lateral footprint of the device.
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 approach enhances contact formation by increasing the surface area of epitaxial source/drain regions, reducing contact resistance and parasitic capacitance, and improving the performance of FinFETs, especially at smaller technology nodes.
Implementation Method 1
A contact etch stop layer (CESL) is formed before epitaxial source/drain regions, allowing for over-etching of inter-layer dielectric layers during contact formation
Data Source
AI summary
In an embodiment, a structure includes: a contact etch stop layer (CESL) over a substrate; a fin extending through the CESL; an epitaxial source/drain region in the fin, the epitaxial source/drain region extending through the CESL; a silicide contacting upper facets of the epitaxial source/drain region; a source/drain contact contacting the silicide, lower facets of the epitaxial source/drain region, and a first surface of the CESL; and an inter-layer dielectric (ILD) layer surrounding the source/drain contact, the ILD layer contacting the first surface of the CESL.