Nitrided Inner Spacers for Selective Epitaxy in Nanosheet FETs
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Solution Overview
Problem
The challenge in manufacturing nanosheet gate-all-around FETs is the random nucleation of epitaxial growth on gate spacers due to lowered growth temperatures, which affects the selectivity of epitaxial growth on inner spacers and bottom dielectric isolations.
Innovation Solution
Increasing the nitrogen content on the surfaces of inner spacers and bottom dielectric isolations to enhance the reactivity with epitaxial precursors, thereby improving the selectivity of epitaxial growth and reducing random nucleation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If growth temperature is lowered to promote absorption of precursor materials on inner spacers, then absorption efficiency is improved, but random nucleation occurs on gate spacers reducing selectivity
Solution Approach 1:
The patent applies local quality by introducing nitrogen specifically to the inner spacer surfaces to create a chemically distinct region. The nitrogen treatment modifies the surface chemistry of inner spacers to enhance precursor absorption, while gate spacers remain untreated. This localized modification allows selective epitaxial growth on inner spacers without affecting gate spacers, resolving the selectivity issue that would otherwise occur at lowered growth temperatures.
2Manufacturing precision
If nitrogen content on inner spacer surfaces is increased to enhance reactivity with epitaxial precursors, then selectivity of epitaxial growth is improved, but process complexity increases
Solution Approach 1:
The patent applies preliminary action by performing nitrogen introduction to inner spacer surfaces before the epitaxial growth process. This pre-treatment modifies the surface chemistry in advance, creating nitrogen-rich sites that will selectively attract precursor materials during subsequent growth. By preparing the surface beforehand, the actual epitaxial growth can proceed under more relaxed conditions without requiring complex real-time control mechanisms.
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 improves the quality of source/drain features by promoting selective epitaxial growth on nitrogen-rich surfaces, reducing defects and voids, and enhancing the overall performance of the FETs.
Implementation Method 1
selectivity of epitaxial growth on inner spacers and bottom dielectric isolations
Implementation Method 2
Increasing the nitrogen content on the surfaces of inner spacers and bottom dielectric isolations
Data Source
AI summary
A semiconductor structure includes a channel structure, a gate structure, two source/drain features, and a plurality of inner spacers. The channel structure includes a plurality of channel features which are spaced apart from each other. The gate structure is disposed to surround the channel features. The source/drain features are disposed at two opposite sides of the channel structure such that each of the channel features interconnects the source/drain features. Each of the inner spacers is disposed to separate the gate structure from a corresponding one of the source/drain features. Each of the inner spacers includes an inner spacer body and a lateral nitrided portion. The lateral nitrided portion is in direct contact with the corresponding one of the source/drain features and has a nitrogen content greater than that of the inner spacer body.