FinFET Threshold Voltage Control via Annealing
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Solution Overview
Problem
Existing methods for fabricating semiconductor devices face challenges in forming robust processes for achieving different threshold voltages, which is crucial for advanced IC processing and manufacturing as the industry scales down to smaller geometries and more complex circuits.
Innovation Solution
The method involves forming a semiconductor device using a FinFET structure where different threshold voltages are achieved by performing an annealing process or thermal oxidation to change the composition of specific channel regions, allowing for the formation of high-k/metal gates with distinct threshold voltages without the need for implantation or work function metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If implantation or work function metal layers are used to achieve different threshold voltages, then threshold voltage differentiation is possible, but the fabrication process becomes more complex and less robust
Solution Approach 1:
The patent extracts and removes the gate stack from the FinFET structure to expose the fin feature, then performs annealing to change the composition of the fin feature in situ. This eliminates the need for implantation or work function metal layers, simplifying the process while achieving different threshold voltages through composition modification of the existing fin material.
Solution Approach 2:
The patent changes the composition parameter of the fin feature through thermal annealing, transforming the material composition from a first composition to a second composition. This parameter change enables different threshold voltages to be achieved in different regions without adding complex fabrication steps, as the composition gradient is created through controlled thermal diffusion.
2Ease of manufacture
If annealing process is used to change composition of channel regions, then different threshold voltages are achieved with simpler process, but precise control of composition change is challenging
Solution Approach 1:
The patent performs preliminary actions by forming the gate stack before removal, and by preparing the FinFET structure with specific fin features before annealing. The gate stack removal exposes the fin feature in a controlled manner, and the preliminary structure preparation ensures that subsequent annealing produces the desired composition gradient with appropriate precision.
Solution Approach 2:
The patent employs feedback mechanisms through the annealing process parameters and timing to control the composition change. By monitoring and adjusting the annealing conditions, the process achieves precise control over the composition gradient formation, ensuring manufacturing precision while maintaining ease of manufacture.
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 enables robust and flexible formation of different threshold voltages, improving process control and simplifying the fabrication process by ensuring self-aligned composition changes in channel regions, thus addressing the limitations of existing methods.
Implementation Method 1
performing an annealing process to change a composition of a fin feature from a first composition to a second composition
Implementation Method 2
performing an annealing process or thermal oxidation to change the composition of specific channel regions
Data Source
AI summary
A method for fabricating a semiconductor device includes forming a first gate stack over a first fin feature and second gate stack over a second fin feature, removing the first gate stack to form a first gate trench that exposes the first fin structure, removing the second gate stack to form a second gate trench that exposes the second fin feature, performing an annealing process to change a composition of a portion of the first fin feature and forming a first high-k/metal gate (HK/MG) within the first gate trench over the portion of the first fin feature and a second HK/MG within the second gate trench over the second fin feature. Therefore the first HK/MG is formed with a first threshold voltage and the second HK/MG is formed with a second threshold voltage, which is different than the first threshold voltage.