FinFET Buffer Layer Geometry to Block Source/Drain Dopant Diffusion
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Solution Overview
Problem
In fin-based transistors, dopants from the source/drain region can diffuse into the mesa region, leading to increased electron tunneling, short channel effects, and leakage, which degrade device performance by enhancing off-current and leakage.
Innovation Solution
A buffer layer is formed under the source/drain region with a curved top surface and specific widths extending over shallow trench isolation regions, fully situated between the source/drain and mesa regions to block dopant diffusion, thereby reducing short channel effects and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If source/drain region is formed adjacent to fin structure, then transistor functionality is achieved, but dopant diffusion into mesa region increases leakage and short channel effects
Solution Approach 1:
A buffer layer is introduced as an intermediary structure between the source/drain region and the mesa region. This buffer layer acts as a barrier that prevents dopant diffusion from the source/drain region into the mesa region, thereby reducing leakage current and short channel effects while maintaining the functional integrity of the transistor.
Solution Approach 2:
The structure is segmented into distinct regions: source/drain region, buffer layer, and mesa region. By dividing the continuous structure into separate segments with the buffer layer in between, dopant diffusion pathways are interrupted, preventing harmful diffusion into the mesa region while preserving transistor operation.
2Reliability
If buffer layer is added to block dopant diffusion, then leakage is reduced, but device structure becomes more complex
Solution Approach 1:
The buffer layer is implemented as a thin film or shell-like structure that provides effective dopant blocking with minimal added complexity. The thin-film nature allows it to be integrated into existing transistor structures without significantly increasing overall device complexity or footprint.
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 buffer layer effectively decreases short channel effects, off-current, and leakage, enhancing the overall performance of the device by preventing dopant diffusion and improving control over the channel region.
Implementation Method 1
Dopants from the source/drain region of fin-based transistors, such as finFETs and nanostructure transistors, diffuse into the mesa region. A buffer layer is formed under the source/drain region with a curved top surface and specific dimensions to prevent dopant diffusion
Data Source
AI summary
In some implementations, a buffer layer is formed under a source/drain region of a device. A shape of the buffer layer may include a curved top surface having a height that extends to increase coverage of nanosheets of a fin structure of the device. The shape also includes regions having widths that extend towards shallow trench isolation regions of the device. The shape reduces a likelihood of dopants diffusing from the source/drain region into a mesa region of the fin structure. As a result, a performance of the device may be increased by decreasing short channel effects, decreasing an off-current of the device, and decreasing leakage within the device, among other examples.