TFET Bandgap Engineering for Source-Gate Misalignment
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Solution Overview
Problem
Conventional CMOSFET switches face reliability and performance issues at small scales due to manufacturing challenges in achieving precise alignment between the source region and gate structure, leading to suboptimal on/off transitions and current conduction in tunneling field effect transistor (TFET) devices.
Innovation Solution
A TFET device structure is developed with a semiconductor substrate comprising layers of intermediate, low, and high bandgap materials, where the low bandgap material enhances tunneling at the source-channel junction and the high bandgap material inhibits tunneling, allowing for improved current conduction and reduced sensitivity to source/gate misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional TFET devices are used with standard doping structures, then manufacturing is simpler, but alignment precision between source region and gate structure deteriorates at small scales
Solution Approach 1:
The patent applies local quality by creating distinct bandgap regions within the channel structure. Specifically, a first channel region with a first bandgap and a second channel region with a second bandgap are formed, allowing different sections of the device to have optimized properties for their specific functions. This local differentiation enables precise control of carrier tunneling in critical regions without complicating the entire device structure.
Solution Approach 2:
The patent employs composite materials by combining semiconductor layers with different bandgap energies. The channel structure comprises regions with different bandgaps (e.g., InGaAs with lower bandgap and InAlAs with higher bandgap), creating a composite structure that leverages the advantages of each material. This composite approach enables enhanced tunneling efficiency while maintaining manufacturing feasibility through established material systems.
2Productivity
If the source region is heavily doped to enhance tunneling current, then current conduction improves, but sensitivity to source/gate misalignment increases
Solution Approach 1:
The patent applies local quality by creating distinct bandgap regions within the channel structure. Specifically, a first channel region with a first bandgap and a second channel region with a second bandgap are formed, allowing different sections of the device to have optimized properties for their specific functions. This local differentiation enables precise control of carrier tunneling in critical regions without complicating the entire device structure.
Solution Approach 2:
The patent employs parameter changes by varying the bandgap energy parameter across different channel regions. By transitioning from a uniform bandgap structure to a graded or stepped bandgap structure, the device optimizes tunneling probability while reducing sensitivity to alignment variations. The bandgap parameter is strategically modified to achieve robust performance.
3Reliability
If conventional single-bandgap channel structure is used, then device structure is simpler, but tunneling efficiency and on/off transitions are suboptimal
Solution Approach 1:
The patent applies local quality by creating distinct bandgap regions within the channel structure. Specifically, a first channel region with a first bandgap and a second channel region with a second bandgap are formed, allowing different sections of the device to have optimized properties for their specific functions. This local differentiation enables precise control of carrier tunneling in critical regions without complicating the entire device structure.
Solution Approach 2:
The patent employs composite materials by combining semiconductor layers with different bandgap energies. The channel structure comprises regions with different bandgaps (e.g., InGaAs with lower bandgap and InAlAs with higher bandgap), creating a composite structure that leverages the advantages of each material. This composite approach enables enhanced tunneling efficiency while maintaining manufacturing feasibility through established material systems.
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 TFET device exhibits predictable and consistent current conduction and on/off transitions, even with source/gate misalignment, enhancing tunneling efficiency and reducing dependence on gate bias, thus overcoming scaling limitations and alignment challenges in small-scale semiconductor fabrication.
Implementation Method 1
the low bandgap material enhances tunneling at the source-channel junction
Implementation Method 2
the high bandgap material inhibits tunneling
Data Source
AI summary
A tunneling field effect transistor (TFET) device includes a semiconductor substrate having a layer of relatively intermediate bandgap semiconductor material, a layer of relatively low bandgap semiconductor material overlying the layer of relatively intermediate bandgap semiconductor material, and a layer of relatively high bandgap semiconductor material overlying the layer of relatively low bandgap semiconductor material. The TFET device includes a source region, a drain region, and a channel region defined in the semiconductor substrate. The TFET device also has a gate structure overlying at least a portion of the channel region. The source region is highly doped with an impurity dopant having a first conductivity type, and the drain region is highly doped with an impurity dopant having a second conductivity type. The layer of relatively low bandgap semiconductor material promotes tunneling at a first junction between the source region and the channel region, and the layer of relatively high bandgap semiconductor material inhibits tunneling at a second junction between the source region and the channel region.