Tunnel Field Effect Transistor Steep Tunnel Edge
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Solution Overview
Problem
Conventional transistors face limitations in energy efficiency due to high energy consumption and heat generation, primarily because of the thermally broadened energy distribution of charge carriers, which is reflected in the inverse sub-threshold slope (S) that exceeds 60 mV/dec, especially in short-channel transistors, leading to increased off-current and losses.
Innovation Solution
A tunnel field effect transistor (TFET) with a vertical tunnel path and a manufacturing method that involves silicidation and dopant segregation in the source region to create a steeper tunnel edge and an enlarged tunnel region parallel to the electric field lines, using a material with a narrower band gap, such as a thin SiGe layer, to achieve a reduced tunnel barrier and increased tunnel area, thereby reducing the inverse sub-threshold slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional field effect transistors are used with constant size reduction, then transistor density increases, but energy consumption and heat generation increase excessively
Solution Approach 1:
The patent changes the fundamental operating mechanism of the transistor from thermal carrier injection to quantum mechanical band-to-band tunneling. This parameter change in the switching mechanism enables steep sub-threshold slopes below 60 mV/dec, allowing high transistor density while maintaining low energy consumption through reduced off-state leakage current.
Solution Approach 2:
The patent replaces the conventional thermal field effect mechanism with a quantum mechanical tunneling mechanism. By substituting the thermal injection process with band-to-band tunneling controlled by gate voltage, the device achieves superior energy efficiency and switching characteristics suitable for high-density integration.
2Use of energy by stationary object
If the inverse sub-threshold slope S is reduced below 60 mV/dec, then threshold voltage can be reduced without significant increase in off-current, but conventional transistors cannot achieve S < 60 mV/dec due to thermal limitations
Solution Approach 1:
The patent substitutes the thermal field effect mechanism with quantum mechanical band-to-band tunneling. This substitution enables the inverse sub-threshold slope to drop below 60 mV/dec, allowing threshold voltage reduction while maintaining low off-current through the tunneling mechanism's inherent sharp switching characteristics.
Solution Approach 2:
The patent changes the switching mechanism from thermal to quantum mechanical, enabling S < 60 mV/dec. This parameter change in the fundamental operation mode allows simultaneous reduction of threshold voltage and off-current, breaking the conventional trade-off relationship.
3Use of energy by stationary object
If tunnel field effect transistors are implemented with conventional structures, then band-to-band tunneling can occur, but output currents are too small and S is only reduced in an unusably small gate voltage range
Solution Approach 1:
The patent applies local quality by creating a highly doped source region with specific doping concentrations (10^19 to 10^21 atoms/cm³) and a tailored doping profile. This localized high doping concentration in the source region enhances the tunneling current density while maintaining the steep sub-threshold slope in a usable gate voltage range, resolving the contradiction between current magnitude and switching sharpness.
Solution Approach 2:
The patent changes the doping parameters in the source region, implementing high doping concentrations and specific doping profiles that are not present in conventional TFET designs. This parameter optimization enables simultaneous achievement of high output current and steep sub-threshold slope below 60 mV/dec in a practical operating range.
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 solution results in a significant increase in on-current and a reduction in off-current, achieving an inverse sub-threshold slope of less than 60 mV/dec, leading to higher energy efficiency and enabling the reduction of threshold voltage without increasing off-current, thus enhancing the performance of transistors.
Implementation Method 1
selective silicidation and dopant segregation in the source region to provide a steeper tunnel edge
Implementation Method 2
selective silicidation and dopant segregation in the source region to provide a steeper tunnel edge
Implementation Method 3
The most promising concepts include so-called band-to-band tunneling (BTBT) transistors, referred to here as tunnel FETs (TFET)
Implementation Method 4
A dielectric abuts the channel and spaces a control electrode (gate) for controlling the transistor from the channel
Data Source
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AI summary
The invention relates to a tunnel field-effect transistor (TFET) having, in particular, two advantages over the prior art. First, a shortened tunnel barrier and thus a shortened tunnel junction are provided. This is effected in that silicidation and additionally dopant segregation are provided in the source region, which bring about a steeper tunnel edge. Second, the tunnel surface itself is enlarged by means of selective and self-adjusting silicidation, wherein, in the case of the tunnel field-effect transistor (TFET) according to the invention, a tunnel junction that extends parallel to the electric field lines of the gate is provided. The tunnel field-effect transistor (TFET) according to the invention thus combines a tunnel junction parallel to the electric field lines of the gate and having an enlarged tunnel region below the gate with a material that has a narrower band gap. The method according to the invention for producing the TFET comprises selective, self-adjusting silicidation and additionally dopant segregation. These steps make it possible to produce the tunnel junction reproducibly with an accuracy of a few nanometers.