CFET Gate Dielectric Supercritical Radical Treatment at Low Thermal Budget
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Solution Overview
Problem
The fabrication of complementary field-effect transistors (CFETs) with vertically stacked n-type and p-type FETs faces challenges in achieving precise lithography, material selection for optimal electronic properties, and maintaining processing margins in features sizes, alignment, thermal budget, and gate structure quality.
Innovation Solution
The method involves treating the gate dielectric material of CFET devices using a supercritical fluid with radicals such as hydrogen, deuterium, oxygen, or fluorine at ultralow temperatures (less than 200°C or 100°C) to improve gate stack quality without exceeding the thermal budget of existing FETs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal annealing is used to improve gate dielectric quality, then gate stack quality is improved, but already formed FETs are damaged due to excessive temperature
Solution Approach 1:
The patent changes the fundamental parameter of the treatment process from thermal to chemical by using radical-containing supercritical fluids. This allows gate dielectric quality improvement through chemical reactions (hydrogenation, fluorination, etc.) rather than thermal annealing, enabling treatment at temperatures below 200°C that do not damage already formed FETs while still achieving desired dielectric properties
Solution Approach 2:
The patent introduces radical-containing supercritical fluids as intermediary substances to transfer the desired chemical modifications to the gate dielectric. These radicals (H, F, O, etc.) act as mediators that can selectively react with the dielectric material to improve quality without requiring high temperatures that would harm the FET structure
2Manufacturing precision
If conventional processing is used to form gate structures, then manufacturing simplicity is maintained, but gate dielectric quality and threshold voltage control are insufficient
Solution Approach 1:
The patent employs multiple radical-containing supercritical fluids with different chemical compositions (hydrogen, fluorine, oxygen radicals) to selectively modify different aspects of gate dielectric quality. This parameter variation in chemical composition enables precise control over dielectric properties such as threshold voltage, mobility, and quality without requiring complex multi-step processing
Solution Approach 2:
The patent applies radical treatment continuously during the gate dielectric formation process rather than using discrete separate steps. The supercritical fluid radicals continuously interact with the dielectric material during deposition and formation, ensuring uniform quality improvement throughout the gate structure without interrupting the manufacturing flow
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 allows for the formation of high-quality gate stacks in CFET devices with reduced defects, improved electrical performance, and increased threshold voltage, while avoiding thermal annealing impacts on already formed FETs.
Implementation Method 1
performing a radical treatment on the gate dielectric layer in a supercritical fluid
Implementation Method 2
treating the gate dielectric material of CFET devices using a supercritical fluid with radicals such as hydrogen, deuterium, oxygen, or fluorine
Data Source
AI summary
The present disclosure provides a method that includes providing a semiconductor structure having a bottom channel region and a top channel region over the bottom channel region; forming a gate dielectric layer over and wrapping around top channels in the top channel region; performing a radical treatment on the dielectric layer in a supercritical fluid; and forming a metal gate electrode on the dielectric layer.