Self-Aligned Inner Spacer for Smooth GAA Source/Drain Epitaxy
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Solution Overview
Problem
The fabrication of gate-all-around (GAA) transistors faces challenges due to poor epitaxial source and drain (S/D) growth, which results in mobility reduction and performance degradation.
Innovation Solution
The formation of self-aligned inner spacers by reflowing semiconductor layers provides a smooth S/D region interface, improving epitaxial S/D feature growth and reducing interface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fabrication processes are used for GAA transistors, then gate control is improved through multi-gate structure, but epitaxial source and drain growth quality deteriorates due to surface roughness
Solution Approach 1:
The method performs preliminary surface preparation by forming a sacrificial layer and performing selective etching to create a smooth template surface before epitaxial growth. This preliminary action ensures that the surface is properly prepared in advance, preventing the surface roughness that would otherwise degrade epitaxial S/D growth quality while maintaining the GAA structure's gate control benefits
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary element between the substrate and the epitaxial S/D regions. This sacrificial layer serves as a temporary structure that enables controlled surface preparation and provides a smooth interface for subsequent epitaxial growth, resolving the contradiction between maintaining gate control and achieving high-quality S/D growth
2Ease of manufacture
If epitaxial S/D features are grown on rough surfaces, then fabrication process is simplified, but device performance deteriorates due to mobility reduction
Solution Approach 1:
The method performs preliminary surface conditioning through controlled etching of the sacrificial layer to create a smooth surface template before epitaxial growth. This preliminary surface preparation enables high-quality epitaxial S/D growth without complicating the overall fabrication process, thereby maintaining ease of manufacture while improving device performance through reduced surface roughness
Solution Approach 2:
The patent changes the surface morphology parameter by performing selective etching to transform the surface from rough to smooth. This parameter change in surface roughness directly improves carrier mobility and device performance while the etching process itself is integrated into the existing fabrication flow, maintaining ease of manufacture
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 smooth S/D region interface achieved by self-aligned inner spacers enhances epitaxial growth, reducing defects and improving the overall performance of GAA devices.
Implementation Method 1
performing a reflow process to the first semiconductor layer to form an inner spacer
Implementation Method 2
epitaxially growing a sour/drain feature in the source and drain region
Data Source
AI summary
Semiconductor device and the manufacturing method thereof are disclosed herein. An exemplary method of forming a semiconductor device comprises forming a fin over a substrate, wherein the fin comprises a first semiconductor layer and a second semiconductor layer comprising different semiconductor materials, and the fin includes a channel region and a source/drain region; forming a dummy gate structure over the substrate and the fin; etching a portion of the fin in the source/drain region; selectively removing an edge portion of the second semiconductor layer in the channel region of the fin such that the second semiconductor layer is recessed, and an edge portion of the first semiconductor layer is suspended; performing a reflow process to the first semiconductor layer to form an inner spacer, wherein the inner spacer forms sidewall surfaces of the source/drain region of the fin; and epitaxially growing a sour/drain feature in the source/drain region.