Sectioned Epitaxial Source-Drain for Multi-Gate Transistors
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Solution Overview
Problem
Wide gate pitches in multi-gate field-effect transistors lead to underfilling of semiconductor material in cavities, degrading radio-frequency performance, reducing drain current, increasing contact resistance, and causing contact open issues.
Innovation Solution
A structure and method for forming a field-effect transistor with a semiconductor body, where a first and second gate structure extend over the body, and a source/drain region is formed with a first and second semiconductor layer, including sections that are laterally positioned between the gate structures, allowing for epitaxial growth in smaller cavities to alleviate underfilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wide gate pitches are used in multi-gate field-effect transistors, then device layout flexibility is improved, but semiconductor material underfilling in cavities occurs degrading radio-frequency performance
Solution Approach 1:
The source/drain region is divided into multiple semiconductor layers (first semiconductor layer and second semiconductor layer) with the second layer positioned laterally between sections of the first layer. This segmentation allows each layer to independently fill the cavity space, ensuring complete filling even with wide gate pitches, thereby maintaining radio-frequency performance while preserving layout flexibility.
2Adaptability or versatility
If wide gate pitches are used in multi-gate field-effect transistors, then device layout flexibility is improved, but drain current is reduced
Solution Approach 1:
The segmented semiconductor layer structure provides multiple parallel conduction paths through the source/drain region. The first and second semiconductor layers create additional current flow channels, compensating for the increased resistance that would normally result from wide gate pitches, thus maintaining high drain current while preserving layout flexibility.
Solution Approach 2:
The invention transitions from a planar source/drain structure to a multi-layer vertical structure. By adding the second semiconductor layer positioned laterally between sections of the first layer, the current conduction path is extended into the vertical dimension, providing additional conduction channels that maintain high drain current despite wide gate pitches.
3Adaptability or versatility
If wide gate pitches are used in multi-gate field-effect transistors, then device layout flexibility is improved, but contact resistance is increased
Solution Approach 1:
The segmented semiconductor layer structure creates multiple contact interfaces and parallel conduction paths at the contact region. This segmentation reduces the effective contact resistance by providing multiple current flow channels, compensating for the increased resistance that would normally result from wide gate pitches while preserving layout flexibility.
4Adaptability or versatility
If wide gate pitches are used in multi-gate field-effect transistors, then device layout flexibility is improved, but contact open issues occur
Solution Approach 1:
The segmented semiconductor layer structure provides multiple independent conduction paths through the source/drain region. This segmentation reduces the risk of contact open issues by ensuring that if one path is compromised, alternative paths remain available, thereby improving contact formation reliability while preserving layout flexibility.
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 approach improves filling of source/drain regions, reduces contact resistance, and enhances radio-frequency performance by utilizing smaller cavities for epitaxial growth, compensating for larger gate pitches and preventing underfilling.
Implementation Method 1
Another approach is to epitaxially grow sections of a semiconductor material from the semiconductor body to form the source and drain. The semiconductor material may be in situ doped during epitaxial growth with either an n-type dopant or a p-type dopant.
Data Source
AI summary
Structures for a field-effect transistor and methods of forming a structure for a field-effect transistor. First and second gate structures extend over the semiconductor body, a second gate structure that extends over the semiconductor body. A source/drain region is positioned laterally between the first gate structure and the second gate structure. The source/drain region includes a first semiconductor layer and a second semiconductor layer. The first semiconductor layer has a first section and a second section. The second semiconductor layer is positioned laterally between the first section of the first semiconductor layer and the second section of the first semiconductor layer.