Multi-Threshold FinFETs via Doping and Geometry Control
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Solution Overview
Problem
The challenge in integrated circuits is to control the trade-off between leakage current and drive current in FinFETs, particularly in making smaller transistors without increasing chip area, as existing methods either fail to effectively manage leakage or require uniform transistor footprints.
Innovation Solution
Controlling the doping of the fin body and geometry of the fin above its base to achieve desired electrical performance parameters, allowing for FinFETs with different thresholds on the same integrated circuit, using various fin geometries such as triangular, rectangular, and trapezoidal cross-sections, and optimizing fin-body doping levels to manipulate leakage and drive currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the channel length is reduced to make transistors smaller, then the transistor size decreases, but leakage current increases due to short-channel effects
Solution Approach 1:
The patent transitions from planar FETs to FinFETs by introducing a vertical fin structure that protrudes from the substrate. The gate electrode wraps around the fin on multiple sides (front, back, and both sides), providing three-dimensional control of the channel. This dimensional change allows effective control of short-channel effects even when the channel length is reduced, thereby enabling smaller transistor footprints without suffering from excessive leakage current.
Solution Approach 2:
The patent employs a composite structure combining the fin body (semiconductor material), shallow trench isolation (dielectric material), and gate electrode (conductive material) to create a FinFET device. The fin body is doped with specific doping levels to optimize electrical characteristics, while the isolation and gate materials provide structural support and electrical control, collectively resolving the leakage issue in scaled transistors.
2Object-generated harmful factors
If the fin base size is reduced to decrease leakage current, then leakage current decreases, but manufacturing difficulty increases
Solution Approach 1:
The patent controls leakage current by adjusting the doping level parameter of the fin body rather than reducing the fin base dimensions. By varying the doping concentration in the fin body, the patent achieves different threshold voltages and leakage characteristics while maintaining a uniform fin base size that is compatible with standard manufacturing processes. This parameter change approach decouples leakage control from geometric scaling, simplifying fabrication.
3Adaptability or versatility
If different fin base sizes are used to achieve different threshold voltages, then transistor threshold control improves, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent applies local quality by doping different regions of the fin body with different doping levels. Specifically, the fin body can have a first doping level in certain regions and a second doping level in other regions, allowing different threshold voltages to be achieved in different transistors on the same chip. This enables localized property variation without changing the overall fin base geometry, thereby maintaining fabrication simplicity while achieving threshold voltage diversity.
4Object-generated harmful factors
If source and drain implants are retracted to decrease leakage, then leakage current decreases, but transistor area increases
Solution Approach 1:
The patent uses the vertical fin structure to achieve leakage control without increasing the planar footprint. The wrapped gate configuration in the vertical dimension provides enhanced control over the channel, allowing leakage reduction while maintaining compact transistor dimensions in the planar view. This three-dimensional approach avoids the area penalty associated with retracted source and drain implants in planar FETs.
Data Source
AI summary
A method for manufacturing a FinFET having a fin that has a fin body includes selecting a desired electrical performance parameter, selecting a base dimension of the fin, identifying a combination of fin-body doping and fin-geometry that causes the FinFET to have the desired electrical performance parameter, doping the fin body according to the identified fin-body doping, and fabricating the fin according to the fin-geometry.