FinFET Gate Electrode Masking for Decoupled Doping
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Solution Overview
Problem
Conventional FinFET structures face challenges in introducing dopant concentration into source/drain regions without altering the gate electrode's doping and work function, leading to coupled gate and source/drain doping processes.
Innovation Solution
A semiconductor structure and method where the gate electrode is masked during the dopant introduction process for source/drain region formation, using sidewall and cap spacers to prevent dopant introduction into the gate electrode, thereby decoupling gate doping from source/drain doping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dopant concentration is introduced into source/drain regions using angled ion implantation or gas phase diffusion doping, then source/drain regions are successfully formed, but the gate electrode is also exposed to the doping process which alters its doping and work function
Solution Approach 1:
The gate electrode structure is segmented into multiple components: the gate electrode itself, a first dielectric layer covering it, and a second dielectric layer covering the first dielectric layer. This segmentation creates distinct regions that allow selective doping - the source/drain regions can be doped while the gate electrode remains protected by the dielectric layers, preventing unwanted dopant accumulation in the gate and maintaining stable work function.
Solution Approach 2:
The first and second dielectric layers act as intermediary protective barriers between the doping process and the gate electrode. These dielectric layers are strategically positioned to block dopant diffusion into the gate electrode during source/drain doping processes, while still allowing the doping process to proceed effectively for the source/drain regions.
2Productivity
If gate electrode doping is coupled with source/drain doping process, then fabrication steps are reduced, but independent control of gate work function and threshold voltage is lost
Solution Approach 1:
By segmenting the gate electrode structure with protective dielectric layers, the patent enables independent control of gate and source/drain doping. The gate electrode can be pre-doped to a specific concentration before source/drain doping occurs, and the dielectric layers prevent further dopant accumulation during source/drain processing. This segmentation provides the versatility to independently optimize gate work function and threshold voltage while maintaining efficient fabrication through sequential but independent doping steps.
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 independent doping of source/drain regions and gate electrodes, enabling flexible selection of threshold voltage and improving the reliability of FinFET performance by preventing dopant introduction into the gate electrode during source/drain doping.
Implementation Method 1
The sidewall spacer and the cap spacer operate to mask the gate electrode when, for example, the first and second ends of the first feature, which flank the central channel region, are doped to form source/drain regions
Implementation Method 2
The dopant concentration may be introduced into the fin by angled ion implantation or by gas phase diffusion doping
Implementation Method 3
The dopant concentration may be introduced into the fin by angled ion implantation or by gas phase diffusion doping
Data Source
AI summary
Semiconductor structures in which the gate electrode of a FinFET is masked from the process introducing dopant into the fin body of the FinFET to form source/drain regions and methods of fabricating such semiconductor structures. The gate doping, and hence the work function of the gate electrode, is advantageously isolated from the process that dopes the fin body to form the source/drain regions. The sidewalls of the gate electrode are covered by sidewall spacers that are formed on the gate electrode but not on the sidewall of the fin body.