Low-Resistance Source/Drain Epitaxy for Void-Free GAA Contacts
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Solution Overview
Problem
Existing methods for forming source/drain features in multi-gate transistors, particularly in gate-all-around (GAA) transistors, result in voids due to faceted growth of source/drain materials, leading to increased resistance and contact resistance, which can cause electrical connection failures.
Innovation Solution
The method involves forming a void-free source/drain feature by using a germanium-containing epitaxial layer that undergoes a thermal treatment to reshape it into a smooth profile, reducing the likelihood of void formation and enhancing the conductivity of the source/drain contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If source/drain materials are deposited using conventional epitaxial growth methods, then the source/drain features are formed, but voids are created due to faceted growth, leading to increased resistance and contact resistance
Solution Approach 1:
The patent changes the material composition parameter by incorporating germanium into the silicon epitaxial layer, creating a silicon-germanium alloy. This compositional change modifies the growth characteristics to eliminate faceting and void formation, while the subsequent thermal treatment further adjusts the material properties to achieve a smooth profile and low resistance
Solution Approach 2:
The patent performs preliminary actions by first forming the epitaxial layer with controlled composition, then applying thermal treatment before final metallization. This sequence of preliminary steps prepares the source/drain features in advance to prevent void formation and ensure smooth profiles, thereby guaranteeing reliable electrical connections in subsequent processing
2Manufacturing precision
If germanium-containing epitaxial layer is formed and thermally treated, then void-free smooth source/drain features are achieved, but process complexity increases
Solution Approach 1:
The patent merges multiple functions into the epitaxial growth process itself: the same process that forms the source/drain features also controls the germanium distribution and establishes the foundation for the smooth profile. The thermal treatment step combines annealing and profile shaping into a single operation, reducing the number of separate process steps needed to achieve void-free features
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 results in reduced resistance and contact resistance, ensuring reliable electrical connections and improved performance of multi-gate transistors by minimizing voids and facilitating smooth epitaxial growth.
Implementation Method 1
a first epitaxial layer is formed over the source/drain trench. The first epitaxial layer is subjected to a thermal treatment to reshape the first epitaxial layer into a smooth profile
Implementation Method 2
A low-resistance epitaxial layer is selectively deposited from surfaces of the reshaped epitaxial layer
Data Source
AI summary
Methods of forming a low-resistance source/drain feature for a multi-gate device are provided. A example method includes forming a fin-shaped structure that includes a plurality of channel layers interleaved by a plurality of sacrificial layers, recessing a source/drain region of the fin-shaped structure to form a source/drain recess, selectively and partially recessing sidewalls of the plurality of sacrificial layers to form inner spacer recesses, forming inner spacers in the inner spacer recesses, forming a bottom dielectric layer over the substrate, depositing a first epitaxial layer over the inner spacers and the sidewalls of the plurality of the channel layers, performing a thermal treatment to reshape the first epitaxial layer, after the performing of the thermal treatment, depositing a second epitaxial layer over the first epitaxial layer. The first epitaxial layer includes germanium and the second epitaxial layer is free of germanium.