Gate Insulating Film Threshold Voltage Control
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Solution Overview
Problem
In MOS transistors with high dielectric constant insulating films and metal gate electrodes, controlling the threshold voltage is challenging due to the complexity of the material interactions and layer compositions.
Innovation Solution
A semiconductor device production method involving the formation of a low-oxygen aluminum oxide capping layer and a tantalum-nitrogen-containing film, followed by patterning and heat treatment, to effectively control the threshold voltage by adjusting the equivalent oxide thickness and dielectric constant of the gate insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high dielectric constant insulating film and metal gate electrode are used in MOS transistors, then the transistor performance is improved, but the threshold voltage becomes difficult to control
Solution Approach 1:
The gate insulating film is segmented into multiple layers: a first gate insulating film (base layer) and a second gate insulating film (capping layer with aluminum oxide). This segmentation allows independent optimization of each layer's properties - the first layer provides high dielectric constant for performance, while the second layer enables threshold voltage control through its specific composition and interface characteristics with the metal gate electrode.
Solution Approach 2:
The patent employs composite material structure for the gate insulating film, combining a high dielectric constant material (such as hafnium oxide) with an aluminum oxide capping layer. This composite structure leverages the high dielectric constant of the first material for transistor performance while utilizing the aluminum oxide layer's properties for threshold voltage control, resolving the contradiction between performance improvement and control precision.
2Manufacturing precision
If a capping layer of heterogeneous material is provided between high dielectric constant insulating film and metal gate electrode, then threshold voltage control is improved, but the device structure becomes more complex
Solution Approach 1:
The aluminum oxide capping layer is applied locally only at the interface region between the high dielectric constant insulating film and the metal gate electrode, rather than throughout the entire device structure. This localized application provides the necessary threshold voltage control functionality while minimizing the overall structural complexity and material usage.
Solution Approach 2:
The patent extracts the threshold voltage control function into a separate, dedicated aluminum oxide capping layer that is distinct from the main high dielectric constant insulating film. This separation allows the capping layer to be optimized specifically for interface control purposes while the bulk insulating film maintains its high dielectric constant properties, simplifying the overall design approach.
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 method achieves precise control over the threshold voltage, reducing leak current and optimizing the equivalent oxide thickness, thereby enhancing the performance of MOS transistors.
Implementation Method 1
forming a first aluminum oxide film with an oxygen content lower than stoichiometric composition on the gate insulating film
Implementation Method 2
carrying out heat treatment after the formation of the tantalum-nitrogen-containing film
Implementation Method 3
forming a first aluminum oxide film with an oxygen content lower than stoichiometric composition on the gate insulating film
Implementation Method 4
forming a tantalum-nitrogen-containing film that contains tantalum and nitrogen on the first aluminum oxide film
Data Source
AI summary
A semiconductor device production method includes: forming a gate insulating film on the p-type region of a semiconductor substrate; forming a first aluminum oxide film with an oxygen content lower than stoichiometric composition on the gate insulating film; forming a tantalum-nitrogen-containing film that contains tantalum and nitrogen on the first aluminum oxide film; forming an electrically conductive film on the tantalum-nitrogen-containing film; patterning the electrically conductive film to form a gate electrode; injecting n-type impurities into the p-type region using the gate electrode as a mask; and carrying out heat treatment after the formation of the tantalum-nitrogen-containing film.