Oxide Semiconductor Transistor Gate Insulator Design
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Solution Overview
Problem
Miniaturization of MOSFETs leads to short-channel effects such as punch-through phenomenon and hot carrier degradation, which are difficult to suppress without increasing tunnel current or transistor size, especially when using silicon-based semiconductors.
Innovation Solution
Employing an oxide semiconductor with a high-k gate insulating film and eliminating impurities like hydrogen to reduce minority carriers, allowing for a thicker equivalent oxide thickness without reducing physical thickness, thereby preventing short-channel effects without the need for an LDD region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the gate insulating film is reduced to suppress short-channel effects, then the operation speed and integration degree are improved, but tunnel current increases causing reliability deterioration
Solution Approach 1:
The patent changes the material parameter of the gate insulating film from conventional silicon oxide to high-k material (hafnium oxide), which has a higher dielectric constant. This allows achieving the same electrical capacitance effect with a thicker physical film, thereby suppressing tunnel current while maintaining gate control effectiveness for short-channel suppression.
Solution Approach 2:
The patent employs a composite gate insulating film structure combining high-k material (hafnium oxide) with silicon oxide layers. This composite structure leverages the high dielectric constant of hafnium oxide to reduce equivalent oxide thickness while using silicon oxide to prevent tunnel current, resolving the contradiction between speed and reliability.
2Productivity
If the channel length is reduced to improve operation speed and integration degree, then miniaturization is achieved, but short-channel effects such as punch-through phenomenon and hot carrier degradation become pronounced
Solution Approach 1:
The patent changes the semiconductor material parameter from conventional silicon to oxide semiconductor (In-Ga-Zn-O). This material change fundamentally alters the electrical characteristics, enabling short channel lengths to be used without exhibiting traditional short-channel effects like punch-through and hot carrier degradation, thus allowing miniaturization while maintaining reliability.
3Reliability
If an LDD region is formed to prevent hot carrier degradation, then reliability is improved, but transistor size increases and switching speed decreases
Solution Approach 1:
The patent extracts and eliminates the need for the LDD region by changing the semiconductor material to oxide semiconductor. The inherent material properties of oxide semiconductor provide sufficient hot carrier resistance without requiring the additional LDD structure, thereby removing the source of increased transistor size and reduced switching speed.
Solution Approach 2:
The patent changes the semiconductor material parameter from silicon to oxide semiconductor, which inherently provides better hot carrier resistance. This material parameter change eliminates the need for structural modifications like LDD regions, maintaining compact transistor size and high switching speed while improving reliability.
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 oxide semiconductor transistor achieves high-speed operation, high integration, low power consumption, and high reliability by eliminating short-channel effects and reducing leakage current, while maintaining a compact size and low cost.
Implementation Method 1
study in which instead of silicon oxide, a high-k material (e.g., hafnium oxide), which has a higher permittivity than silicon oxide, is used as a material of the gate insulating film has been conducted
Implementation Method 2
Employing an oxide semiconductor with a high-k gate insulating film and eliminating impurities like hydrogen to reduce minority carriers
Implementation Method 3
Hot carriers generated by application of high electric field to the vicinity of a drain region have energy large enough to pass an oxide film such as a gate insulating film, and part of the hot carriers causes deterioration
Data Source
AI summary
The semiconductor device includes a transistor including an oxide semiconductor film having a channel formation region, a gate insulating film, and a gate electrode layer. In the transistor, the channel length is small (5 nm or more and less than 60 nm, preferably 10 nm or more and 40 nm or less), and the thickness of the gate insulating film is large (equivalent oxide thickness which is obtained by converting into a thickness of silicon oxide containing nitrogen is 5 nm or more and 50 nm or less, preferably 10 nm or more and 40 nm or less). Alternatively, the channel length is small (5 nm or more and less than 60 nm, preferably 10 nm or more and 40 nm or less), and the resistivity of the source region and the drain region is 1.9×10−5 Ω·m or more and 4.8×10−3 Ω·m or less.