CFET Source/Drain Doping With Upper-Layer Recrystallization Control
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Solution Overview
Problem
As the minimum feature sizes in semiconductor devices are reduced, challenges arise in maintaining device performance and manufacturing ease due to thermal-induced relaxation of source/drain regions.
Innovation Solution
The formation of complementary field-effect transistors (CFETs) with a lower nanostructure-FET and an upper nanostructure-FET, where the upper source/drain region is formed by implanting dopants that amorphize a portion, followed by a rapid thermal process to recrystallize and activate the dopants, while keeping the lower source/drain region below a relaxation temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rapid thermal process is used to activate dopants in the upper source/drain region, then device performance is improved through dopant activation, but thermally-induced relaxation of the lower source/drain region occurs
Solution Approach 1:
The patent applies different thermal treatments to different regions: the upper source/drain region undergoes rapid thermal processing for dopant activation, while the lower source/drain region is maintained below relaxation temperature. This spatial differentiation of thermal quality allows dopant activation where needed without causing relaxation in regions where it would be harmful.
Solution Approach 2:
The CFET structure is segmented into upper and lower nanostructure-FETs with independent source/drain regions. This segmentation allows independent thermal processing of each region's source/drain, enabling the upper region to receive high-temperature treatment while the lower region remains protected from relaxation effects.
2Productivity
If minimum feature sizes are reduced to increase integration density, then more components can be integrated into a given area, but thermal management and manufacturing precision become more difficult
Solution Approach 1:
The patent transitions from planar transistor integration to three-dimensional vertically-stacked CFET architecture. By stacking upper and lower nanostructure-FETs vertically, integration density is dramatically increased without further reducing lateral feature sizes, thereby avoiding the manufacturing precision and thermal management challenges associated with miniaturization.
Solution Approach 2:
The device is segmented into independently processable upper and lower source/drain regions, allowing separate thermal treatment and dopant activation. This segmentation enables precise control over each region's properties even in the compact stacked geometry, maintaining manufacturing precision despite high integration density.
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 improves device performance by activating dopants in the upper source/drain region without causing thermally-induced relaxation of the lower source/drain region, thereby enhancing both performance and manufacturing ease of the completed CFETs.
Implementation Method 1
followed by a rapid thermal process to recrystallize and activate the dopants
Implementation Method 2
implanting dopants that amorphize a portion
Data Source
AI summary
A method includes forming first nanostructures over a substrate, then forming second nanostructures over the plurality of first nanostructures. A first source/drain region is epitaxially grown adjacent the first nanostructures, and a second source/drain region is epitaxially grown over the first source/drain region and adjacent the second nanostructures. An implantation process is performed to implant impurities into the second source/drain region, wherein the implantation process forms an amorphous region within the second source/drain region. At least one rapid thermal process is performed on the second source/drain region, wherein performing each rapid thermal process recrystallizes a portion of the amorphous region.