MOSFET Gate Stack Work Function Tuning for Leakage Suppression
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Solution Overview
Problem
In metal-oxide-semiconductor field-effect transistors (MOSFETs), high impurity concentrations in channel regions to control threshold voltage can lead to increased sub-threshold leakage current, gate-induced drain leakage, and junction leakage.
Innovation Solution
The semiconductor device employs a layered structure for gate electrodes with varying thicknesses of conductive films, particularly titanium nitride, between the gate insulating films to adjust the effective work function, allowing for precise control of threshold voltages and reducing the need for high impurity concentrations in channel doping regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high impurity concentrations are introduced into channel regions to control threshold voltage, then threshold voltage control is improved, but leakage current increases
Solution Approach 1:
The patent changes the work function parameter of the gate electrode by introducing a titanium nitride layer with controlled thickness. This allows precise control of threshold voltage through parameter adjustment (layer thickness) rather than increasing impurity concentration, thereby resolving the contradiction between threshold voltage control and leakage current suppression.
Solution Approach 2:
The gate electrode is constructed as a composite structure combining titanium nitride layer and aluminum layer. This composite material approach enables independent optimization of different functions: titanium nitride controls work function for threshold voltage, while aluminum provides conductivity, avoiding the need for high impurity concentrations in the channel region.
2Manufacturing precision
If many impurities are introduced into channel region, then threshold voltage control is achieved, but sub-threshold leakage current and GIDL increase
Solution Approach 1:
The patent changes the work function parameter of the gate electrode by introducing a titanium nitride layer with controlled thickness. This allows precise control of threshold voltage through parameter adjustment (layer thickness) rather than increasing impurity concentration, thereby resolving the contradiction between threshold voltage control and leakage current suppression.
Solution Approach 2:
The patent extracts the threshold voltage control function from the channel region impurity doping and transfers it to the gate electrode structure. By taking out the work function adjustment function from the channel doping process and placing it in the gate electrode (titanium nitride layer), the channel region can maintain low impurity concentration, thus suppressing sub-threshold leakage current and GIDL.
3Manufacturing precision
If many impurities are introduced into channel region, then threshold voltage control is achieved, but junction leakage current increases
Solution Approach 1:
The patent changes the work function parameter of the gate electrode by introducing a titanium nitride layer with controlled thickness. This allows precise control of threshold voltage through parameter adjustment (layer thickness) rather than increasing impurity concentration, thereby resolving the contradiction between threshold voltage control and leakage current suppression.
Solution Approach 2:
The patent extracts the threshold voltage control function from the channel region impurity doping and transfers it to the gate electrode structure. By taking out the work function adjustment function from the channel doping process and placing it in the gate electrode (titanium nitride layer), the channel region can maintain low impurity concentration, thus suppressing sub-threshold leakage current and GIDL.
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 effectively lowers the threshold voltage of MOSFETs, suppresses leakage currents, and allows for the formation of transistors with different threshold voltages by adjusting the aluminum concentration between insulating films, thereby reducing the required channel doping impurity concentration.
Implementation Method 1
The semiconductor device employs a layered structure for gate electrodes with varying thicknesses of conductive films, particularly titanium nitride, between the gate insulating films to adjust the effective work function
Implementation Method 2
allows for the formation of transistors with different threshold voltages by adjusting the aluminum concentration between insulating films
Data Source
AI summary
A semiconductor device includes a first transistor of a first conductivity type having a first gate insulating film and a first gate structure on the first gate insulating film, the first gate structure including a first conductive film, a second conductive film on the first conductive film and a third conductive film on the second conductive film; and a second transistor of the first conductivity type having a second gate insulating film and a second gate structure on the second gate insulating film, the second gate structure including a fourth conductive film and a fifth conductive film on the fourth conductive film; wherein the first gate insulating film and the second gate insulating film are the same, the second conductive film and the fourth conductive film are the same and the third conductive film and the fifth conductive film are the same.