Separately-formed Source and Drain Transistors for Leakage Control
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Solution Overview
Problem
The existing methods for forming source and drain regions in field-effect transistors, such as ion implantation or epitaxial growth, limit the ability to separately engineer their properties, which hinders optimization of transistor operating characteristics for specific design applications.
Innovation Solution
A structure and method for forming field-effect transistors where one source/drain region is formed by epitaxial growth with a specific dopant concentration and the other by ion implantation, allowing for asymmetrical formation and independent optimization of dopant concentrations, with the epitaxial source/drain region being coupled to the semiconductor body and the ion-implanted region positioned adjacent to the gate structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If source and drain are simultaneously formed by ion implantation or epitaxial growth, then the formation process is simplified, but the ability to separately engineer their properties is lost
Solution Approach 1:
The source and drain regions are formed through separate fabrication steps - one region via epitaxial growth and the other via ion implantation - allowing independent property engineering while maintaining process feasibility
Solution Approach 2:
Different doping methods are applied to different spatial locations (source vs. drain) to achieve locally optimized properties, with each region having independently engineered dopant concentrations and profiles
2Reliability
If asymmetrical dopant concentrations are implemented in source and drain regions, then transistor performance for specific applications is optimized, but the fabrication complexity increases
Solution Approach 1:
The fabrication process is divided into separate steps for source and drain formation, with independent doping control, enabling asymmetrical dopant concentrations without requiring complete process redesign
Solution Approach 2:
Independent control of dopant concentration parameters in source and drain regions allows optimization of transistor characteristics for specific applications while managing fabrication complexity through systematic process separation
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 reduces leakage current while maintaining performance benefits, enabling the field-effect transistor to be used in integrated circuits with improved electrical characteristics and flexibility in design applications.
Implementation Method 1
epitaxially growing a semiconductor layer containing a first concentration of a dopant from a first portion of the semiconductor body to provide a first source/drain region
Implementation Method 2
ion implanting a second portion of the semiconductor body to form a second source/drain region containing a second concentration of the dopant
Data Source
AI summary
Structures for a field-effect transistor and methods of forming a structure for a field-effect transistor. A gate structure is arranged over a channel region of a semiconductor body. A first source/drain region is coupled to a first portion of the semiconductor body, and a second source/drain region is located in a second portion the semiconductor body. The first source/drain region includes an epitaxial semiconductor layer containing a first concentration of a dopant. The second source/drain region contains a second concentration of the dopant. The channel region is positioned in the semiconductor body between the first source/drain region and the second source/drain region.