Multi-Gate Source/Drain Structure With Diffusion Stop Layer for Leakage
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Solution Overview
Problem
Conventional multi-gate transistor structures fail to adequately address leakage, capacitance, and resistance issues, limiting their performance in advanced semiconductor devices.
Innovation Solution
The introduction of a diffusion stop layer with a higher germanium content than the outer epitaxial layer, formed through conformal deposition and selective etching, to control dopant diffusion and reduce leakage, combined with epitaxial layers to enhance carrier mobility and reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional multi-gate transistor structures are used, then device complexity is reduced, but leakage and parasitic capacitance increase
Solution Approach 1:
The source/drain region is segmented into multiple epitaxial layers with different germanium contents. The first epitaxial layer has lower germanium content while the second epitaxial layer has higher germanium content, creating distinct functional zones within the source/drain region to simultaneously reduce leakage and control dopant diffusion
Solution Approach 2:
The source/drain region uses a composite structure combining two different epitaxial materials with varying germanium contents. This composite approach allows the device to achieve multiple objectives (reducing leakage, controlling diffusion, managing capacitance) that cannot be accomplished with a single material
2Reliability
If higher germanium content epitaxial layers are added, then dopant diffusion is controlled and leakage is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The first epitaxial layer with lower germanium content is formed first as a preliminary structure, followed by the formation of the second epitaxial layer with higher germanium content. This sequential approach allows for controlled dopant diffusion and leakage reduction while managing the complexity of multiple epitaxial growth steps
3Productivity
If multi-gate structures are scaled down, then functional density increases, but leakage and short-channel effects worsen
Solution Approach 1:
Different regions of the source/drain structure have different germanium contents tailored to their specific functions. The first epitaxial layer with lower germanium content addresses short-channel effects in the channel region, while the second epitaxial layer with higher germanium content reduces leakage in the source/drain contact regions, allowing aggressive scaling without compromising device performance
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 diffusion stop layer effectively reduces leakage and parasitic capacitance, improving the performance and reliability of multi-gate transistors by controlling dopant diffusion and enhancing carrier mobility.
Implementation Method 1
a diffusion stop layer with a higher germanium content than the outer epitaxial layer, formed through conformal deposition and selective etching, to control dopant diffusion and reduce leakage
Implementation Method 2
combined with epitaxial layers to enhance carrier mobility and reduce parasitic capacitance
Data Source
AI summary
Methods and semiconductor structures are provided. A method according to the present disclosure includes depositing a top epitaxial layer over a substrate, forming a fin structure from the top epitaxial layer and a portion of the substrate, recessing a source/drain region of the fin structure to form a source/drain recess, conformally depositing a semiconductor layer over surfaces of the source/drain recess, etching back the semiconductor layer to form a diffusion stop layer over a bottom surface of the source/drain recess, depositing a first epitaxial layer over the diffusion stop layer and sidewalls source/drain recess, depositing a second epitaxial layer over the first epitaxial layer, and depositing a third epitaxial layer over the second epitaxial layer. A germanium concentration of the diffusion stop layer is greater than a germanium concentration of the top epitaxial layer or a germanium concentration of the first epitaxial layer.