Phase Transition Material Regions in Junctionless Transistors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Junctionless transistors face high off-current due to band-to-band tunneling, leading to a low on-current to off-current ratio, which limits their use, and attempts to suppress this with a thin oxide region in the channel reduce on-current, posing manufacturing challenges.
Innovation Solution
Incorporating phase transition material (PTM) regions, such as vanadium dioxide or vanadium oxide, between the source/drain and channel regions, which act as dielectrics at low bias to prevent parasitic bipolar junction transistors and transition to conductors at higher bias without affecting on-state current, improving the on-current to off-current ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a thin oxide region is introduced in the channel region to suppress parasitic BJT and reduce leakage current, then off-state current is reduced, but on-state current is also reduced
Solution Approach 1:
The patent applies local quality by placing oxide regions specifically at the source and drain ends of the channel where parasitic BJT formation occurs, rather than uniformly throughout the channel. This localized approach suppresses leakage current at critical points while preserving the channel's overall conductivity for on-state current flow.
Solution Approach 2:
The oxide regions act as intermediary elements that mediate between the heavily doped source/drain regions and the intrinsic channel. These oxide intermediaries prevent direct band-to-band tunneling and parasitic BJT formation while allowing controlled carrier flow when the transistor is on, thus decoupling the harmful leakage effect from the desired conduction function.
2Object-generated harmful factors
If the oxide region thickness is adjusted to optimize leakage suppression, then off-state current is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses thin oxide regions (5-20 nm) which is a partial thickness compared to conventional gate oxides. This partial thickness is sufficient to suppress parasitic BJT and reduce leakage current through band alignment effects, while being manufacturable with standard thin-film deposition techniques, thus avoiding excessive precision requirements.
Solution Approach 2:
The patent changes the material parameter (introducing oxide with different dielectric properties) rather than relying solely on precise geometric control. By adjusting oxide composition and thickness within a reasonable range, the patent achieves leakage suppression through material property changes that are more tolerant to manufacturing variations than precise dimensional control would be.
3Device complexity
If junctionless transistor structure is used to eliminate doping junctions, then device complexity is reduced, but off-state current increases due to band-to-band tunneling
Solution Approach 1:
The patent introduces oxide regions as intermediary layers between the heavily doped source/drain regions and the intrinsic channel in junctionless transistors. These oxide intermediaries prevent direct band-to-band tunneling that would otherwise occur at the sharp interfaces of junctionless structures, thus suppressing parasitic BJT formation and reducing off-state leakage while preserving the simplified junctionless architecture.
Solution Approach 2:
The patent creates a composite structure combining heavily doped semiconductor regions, intrinsic semiconductor channel, and oxide layers. This composite material approach leverages the advantages of junctionless simplicity while using oxide-semiconductor interfaces to control band alignment and suppress parasitic effects, achieving both low complexity and low leakage.
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 use of PTM regions effectively reduces off-state current while maintaining on-state current, enhancing the on-current to off-current ratio and simplifying fabrication with self-aligned structures and customizable transition temperatures.
Implementation Method 1
phase transition material (PTM) regions, such as vanadium dioxide or vanadium oxide, between the source/drain and channel regions, which act as dielectrics at low bias to prevent parasitic bipolar junction transistors and transition to conductors at higher bias
Data Source
AI summary
A transistor includes a semiconductor substrate, a first source/drain region and a second source/drain region in the semiconductor substrate with a channel region between the source/drain regions, and a gate over the channel region. In addition, the transistor includes a first phase transition material (PTM) region between the first source/drain region and the channel region, and a second PTM region between the second source/drain region and the channel region. The PTM regions provide the transistor with improved off-state current (IOFF) without affecting the on-state current (ION), and thus an improved ION/IOFF ratio. The transition threshold of PTM regions from dielectric to conductor can be customized based on, for example, PTM material type, doping therein, and/or strain therein.