Surface-Doped GAAFET Channels for Precise Threshold Voltage Tuning
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Solution Overview
Problem
Current semiconductor technologies face challenges in effectively modulating threshold voltage in transistors, particularly in gate-all-around field effect transistors (GAAFETs), which is crucial for controlling the on-state or off-state of the device, as existing methods often require invasive process changes or material alterations.
Innovation Solution
The introduction of dopants into nano-structured layers adjacent to the channels in GAAFETs, followed by an annealing process to drive dopants into the channels, creating a graduated dopant concentration profile, and replacing the depleted doped layers with a gate-all-around structure to achieve radial control of current in surface-doped channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional threshold voltage modulation methods are used in GAAFETs, then the device structure remains simple, but the threshold voltage control precision is insufficient
Solution Approach 1:
The patent applies local quality by introducing dopants specifically into nano-structured layers adjacent to the channel regions, creating a graduated dopant concentration profile that is highest at the channel interface and decreases toward the bulk. This localized doping approach enables precise threshold voltage control without requiring complex modifications to the entire device structure, as the dopant concentration is tailored specifically where it is most effective for electric field modulation.
Solution Approach 2:
The patent utilizes parameter changes by varying the dopant concentration gradient in the nano-structured layers through controlled annealing processes. By adjusting annealing temperature and duration, the dopant diffusion depth and concentration profile can be precisely controlled, enabling continuous tuning of the threshold voltage parameter without changing the fundamental device architecture.
2Measurement precision
If invasive process changes or material alterations are made to modulate threshold voltage, then threshold voltage control is achieved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating dopants into the nano-structured layers during the epitaxial growth or stacking process, before the final device assembly. The dopants are pre-positioned in the nano-structured layers adjacent to the channels, and subsequent annealing simply activates the dopant diffusion into the channel regions. This approach avoids invasive post-fabrication modifications and integrates threshold voltage control into the standard manufacturing flow.
3Measurement precision
If dopant concentration is uniformly distributed in channels, then the manufacturing process is simple, but the threshold voltage tuning precision is reduced
Solution Approach 1:
The patent applies preliminary action by pre-positioning dopants in the nano-structured layers during the stacking or epitaxial growth process, creating a reservoir of dopants that will diffuse into the channel regions during subsequent annealing. This preliminary placement enables precise control of the final dopant concentration profile through controlled diffusion, achieving graduated concentration gradients without requiring complex real-time doping processes.
Solution Approach 2:
The patent utilizes parameter changes by controlling the annealing temperature and duration to precisely regulate dopant diffusion depth and concentration. By varying these thermal parameters, the dopant concentration gradient can be tuned to achieve the desired threshold voltage, transforming a simple thermal process into a precise doping control mechanism.
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 precise tuning of the threshold voltage, enhancing control over the conduction properties of GAAFETs without altering work function metals, thereby improving the device's performance and efficiency.
Implementation Method 1
annealing the nano-sheet structure to drive dopants from the sacrificial doped layers into the channel layers to form doped channel layers having dopant gradients
Data Source
AI summary
GAAFET threshold voltages are tuned by introducing dopants into a channel region. In a GAAFET that has a stacked channel structure, dopants can be introduced into multiple channels by first doping nano-structured layers adjacent to the channels. Then, by an anneal operation, dopants can be driven, from surfaces of the doped layers into the channels, to achieve a graduated dopant concentration profile. Following the anneal operation and after the dopants are diffused into the channels, depleted doped layers can be replaced with a gate structure to provide radial control of current in the surface-doped channels.