Threshold Voltage Shifting Layer via Cyclical Deposition
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Solution Overview
Problem
Conventional methods for scaling semiconductor devices, such as CMOS devices, face challenges in finding suitable dielectric stacks and controlling the threshold voltage of field-effect transistors, particularly in forming an insulating barrier between the gate and channel of field-effect transistors.
Innovation Solution
A cyclical deposition process, including atomic layer deposition and cyclical chemical vapor deposition, is used to form threshold voltage shifting layers on substrates with silicon oxide or high-k dielectric surfaces, utilizing elements like scandium, lanthanum, and yttrium, with specific precursors and reactants to achieve precise control over the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional scaling techniques are used to improve speed and density, then device performance is improved, but controlling the threshold voltage of field effect transistors becomes difficult
Solution Approach 1:
The gate dielectric stack is segmented into multiple functional layers: an interfacial layer (silicon oxide) for interface quality, a high-k dielectric layer for capacitance, and a threshold voltage control layer (containing scandium, yttrium, or lanthanum) for voltage adjustment. This segmentation allows each layer to independently fulfill its specific function, enabling precise threshold voltage control while maintaining device performance.
Solution Approach 2:
The threshold voltage control layer is positioned specifically between the high-k dielectric and the semiconductor substrate, creating a localized region with tailored electrical properties. This local quality modification allows threshold voltage control without affecting other device characteristics, resolving the contradiction between speed and voltage control precision.
2Manufacturing precision
If a threshold voltage control layer is added to improve threshold voltage control, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The threshold voltage control function is merged into the existing gate dielectric stack rather than being implemented as a separate external control mechanism. The control layer is integrated between the high-k dielectric and substrate, combining multiple functions (insulation, capacitance, and voltage control) into a unified structure, thereby reducing overall device complexity while maintaining precise voltage control.
Solution Approach 2:
The high-k dielectric layer serves multiple functions: providing electrical insulation, maintaining capacitive coupling for device speed, and working in conjunction with the threshold voltage control layer to enable precise voltage adjustment. This multi-functionality reduces the need for additional separate components, simplifying the overall device structure.
3Manufacturing precision
If precise thickness control is achieved to reduce equivalent oxide thickness, then manufacturing precision is improved, but gate leakage current increases
Solution Approach 1:
The gate dielectric employs a composite material structure combining silicon oxide (interfacial layer), high-k dielectric material (for capacitance), and a threshold voltage control layer containing scandium, yttrium, or lanthanum. This composite structure achieves low equivalent oxide thickness for precise control while the high-k material and control layer work together to suppress gate leakage current through their combined electrical properties.
Solution Approach 2:
The threshold voltage control layer acts as an intermediary between the high-k dielectric and the semiconductor substrate. This intermediate layer with specific electrical properties (scandium, yttrium, or lanthanum compounds) mediates the electrical interaction, enabling precise threshold voltage control and thickness management while preventing direct contact between the high-k dielectric and substrate that would cause 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 method allows for effective reduction of power consumption in integrated circuits by accurately shifting the threshold voltage, maintaining low impurity content and minimal equivalent oxide thickness, while providing excellent thickness control and reduced gate leakage current.
Implementation Method 1
The cyclical deposition process can include one or more of an atomic layer deposition process and a cyclical chemical vapor deposition process
Implementation Method 2
The cyclical deposition process can include one or more of an atomic layer deposition process and a cyclical chemical vapor deposition process
Implementation Method 3
In some cases, a reactant can be exposed to a plasma to form activated reactant species, e.g. radicals and/or ions
Data Source
AI summary
Methods and systems for depositing threshold voltage shifting layers onto a surface of a substrate and structures and devices formed using the methods are disclosed. An exemplary method includes using a cyclical deposition process, depositing a threshold voltage shifting layer onto a surface of the substrate.