Tunnel Field-Effect Transistor Metal-Semiconductor Alloy Source
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Solution Overview
Problem
Current tunnel field effect transistors (TFETs) face challenges in achieving high on-currents and low leakage currents while maintaining a subthreshold swing below 60 mV/decade, which is essential for reducing power consumption and enabling operation at lower supply voltages.
Innovation Solution
A method for manufacturing TFETs involving the formation of a highly doped, tip-shaped or wedge-shaped source-channel interface using a metal-semiconductor alloy, where the metal layer interacts with the semiconductor material to create a pyramidal or wedge-shaped source-channel junction, enhancing tunneling efficiency and reducing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional CMOS transistors are scaled down to increase integration density, then packaging density is improved, but power consumption increases due to leakage currents and inability to further decrease supply voltage
Solution Approach 1:
The patent changes the fundamental operating mechanism of the transistor from drift-diffusion (CMOS) to quantum tunneling (TFET). This parameter change in the transport mechanism enables sub-60mV/dec subthreshold swing, allowing supply voltage to be reduced below the conventional limit while maintaining switching functionality, thereby reducing power consumption despite high integration density
Solution Approach 2:
The patent replaces the conventional drift-diffusion charge transport mechanism with quantum mechanical band-to-band tunneling. This substitution enables the transistor to operate outside the constraints of classical semiconductor physics, achieving subthreshold swing below 60mV/dec and enabling lower supply voltage operation for reduced power consumption
2Ease of manufacture
If all-silicon TFET structures are used, then manufacturing simplicity is improved, but on-current is reduced due to large tunnel barrier resistance
Solution Approach 1:
The patent employs heterostructure TFET design combining different semiconductor materials (e.g., Ge-Si alloys, InGaAs) with different bandgaps. The source region uses narrow-bandgap material to reduce tunnel barrier resistance and increase on-current, while the channel maintains appropriate properties for low off-current, achieving both high on-current and low power consumption
3Reliability
If heterostructure TFETs are used to increase on-current, then tunneling efficiency is improved, but achieving subthreshold swing below 60mV/dec with reasonable Ion/Ioff ratio becomes difficult
Solution Approach 1:
The patent applies different material compositions and doping levels to specific regions: the source region uses narrow-bandgap material with heavy doping for efficient tunneling and high on-current, the channel uses wider-bandgap material with light or zero doping for low off-current and controlled subthreshold swing. This local differentiation enables simultaneous achievement of high on-current and sub-60mV/dec subthreshold swing
4Reliability
If source doping levels are increased to improve subthreshold swing, then on-current is enhanced, but leakage current control becomes more difficult
Solution Approach 1:
The patent implements spatially varying doping profiles with heavy doping concentrated in the source region to enhance tunneling and on-current, while maintaining light or zero doping in the channel region to suppress leakage current. This localized doping strategy resolves the contradiction between achieving high on-current through increased doping and controlling leakage current by limiting doping in the channel
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 results in TFETs with high on-currents above 100 μA/μm and low off-currents below 1 nA/μm, allowing for operation at reduced power supply voltages and improved performance compared to state-of-the-art TFETs.
Implementation Method 1
forming from the metal layer and from part of the semiconductor channel region in contact with the metal, a metal-semiconductor alloy
Implementation Method 2
Tunnel field effect transistors (TFET) are provided, wherein the drive current of the transistor is based on band-to-band tunneling
Data Source
AI summary
A tunnel Field Effect Transistor is provided comprising an interface between a source and a channel, the source side of this interface being a layer of a first crystalline semiconductor material being substantially uniformly doped with a metal to the solubility level of the metal in the first crystalline material and the channel side of this interface being a layer of this first crystalline semiconductor material doped with this metal, the concentration decreasing towards the channel.