Epitaxial Source Drain Structures With Dopant Segregation
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Solution Overview
Problem
Conventional integrated circuit fabrication processes face challenges in scaling to sub-10 nanometer nodes due to variability and dopant diffusion issues, particularly with arsenic and phosphorous dopants, which affect contact resistivity and device performance.
Innovation Solution
Implementing a post-nucleation etch process to remove arsenic adatoms from the surface after growing an arsenic-doped nucleation layer, reducing arsenic incorporation into the phosphorous-doped main epitaxial layer and thereby improving contact resistivity and device drive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an arsenic-doped nucleation layer is grown to improve contact resistivity, then contact resistivity is improved, but arsenic incorporates into the phosphorous-doped main epitaxial layer causing dopant diffusion issues
Solution Approach 1:
The patent removes arsenic adatoms from the surface after growing the arsenic-doped nucleation layer through a post-nucleation etch process. This extraction of harmful arsenic prevents its unwanted incorporation into the phosphorous-doped main epitaxial layer while preserving the beneficial low contact resistivity properties of the nucleation layer.
Solution Approach 2:
The patent performs a preliminary etching action immediately after nucleation layer formation but before growing the main epitaxial layer. This preliminary removal of arsenic adatoms prevents subsequent dopant diffusion issues while maintaining the nucleation layer's protective function during the main layer growth process.
2Ease of manufacture
If conventional fabrication processes are used for scaling, then manufacturing simplicity is maintained, but variability limits extension into sub-10 nanometer node range
Solution Approach 1:
The patent segments the epitaxial growth process into distinct stages: nucleation layer formation, post-nucleation etching to remove adatoms, and main epitaxial layer growth. This segmentation allows precise control over dopant distribution at each stage, reducing variability while maintaining scalability for sub-10 nanometer nodes.
Solution Approach 2:
The patent introduces a post-nucleation etch process as an intermediary step between nucleation layer formation and main layer growth. This intermediary action removes surface adatoms that would otherwise cause unwanted dopant incorporation, enabling reliable sub-10 nanometer fabrication while preserving process scalability.
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 post-nucleation etch significantly reduces arsenic incorporation in the bulk epitaxial source/drain regions, leading to lower contact resistivity and improved device performance by localizing arsenic dopants to the nucleation layer, as evidenced by APT data showing reduced arsenic concentration in the main epi layer.
Implementation Method 1
Implementing a post-nucleation etch process to remove arsenic adatoms from the surface after growing an arsenic-doped nucleation layer
Implementation Method 2
after growing an arsenic-doped nucleation layer
Data Source
AI summary
In an example, an integrated circuit structure includes a first vertical stack of horizontal nanowires laterally spaced apart from a second vertical stack of horizontal nanowires. An epitaxial source or drain structure is between the first and second vertical stacks of horizontal nanowires. The epitaxial source or drain structure includes a nucleation layer having a first portion in contact with the first vertical stack of horizontal nanowires and a second portion in contact with the second vertical stack of horizontal nanowires. The nucleation layer includes silicon with arsenic dopants. The epitaxial source or drain structure also includes an epitaxial fill layer laterally between the first and second portions of the nucleation layer. The epitaxial fill layer includes silicon with phosphorous dopants. The epitaxial fill layer has a total atomic concentration of arsenic less than half of a total atomic concentration of arsenic of the nucleation layer.