Dual-Dopant Source/Drain Regions for Abrupt Junction Control
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving improved junction abruptness and reduced source/drain contact resistance in advanced process nodes, particularly due to diffusion issues and drain-induced barrier lowering (DIBL) effects.
Innovation Solution
Implanting two different types of dopants into the source/drain region, where the first dopants with lower formation enthalpy (such as arsenic or antimony) are used to reduce diffusion and form stable bonds with vacancies, followed by implantation of second dopants (like phosphorus dimer) to increase their concentration and improve junction abruptness and short channel control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If single dopant implantation is used, then the process is simple, but junction abruptness is poor and diffusion occurs
Solution Approach 1:
The dopant implantation process is segmented into multiple sequential steps: first implanting a preliminary dopant (arsenic or antimony) to reduce diffusion, then implanting the primary dopant (phosphorus) to achieve the desired concentration and junction profile. This segmentation allows each dopant to perform its specific function, resulting in improved junction abruptness while controlling the overall process complexity.
Solution Approach 2:
A preliminary dopant (arsenic or antimony) is implanted before the primary phosphorus dopant to reduce diffusion and form stable bonds with vacancies. This preliminary action creates a foundation that prevents excessive diffusion of the subsequent phosphorus implantation, enabling sharper junctions and better short channel control.
2Reliability
If high dopant concentration is achieved, then contact resistance is reduced, but diffusion increases and junction abruptness deteriorates
Solution Approach 1:
The preliminary dopant (arsenic or antimony) is implanted first to reduce diffusion and stabilize the crystal lattice by bonding with vacancies. This creates a protective effect that allows subsequent high-concentration phosphorus implantation without excessive diffusion, thereby achieving low contact resistance while maintaining junction abruptness.
Solution Approach 2:
The source/drain region contains a composite dopant structure with two different dopants (preliminary dopant and primary dopant) having different formation enthalpies. The preliminary dopant with lower formation enthalpy reduces diffusion, while the primary dopant with higher formation enthalpy provides high concentration for low contact resistance, creating a composite doping profile that achieves both goals simultaneously.
3Manufacturing precision
If dopant diffusion is reduced, then junction abruptness is improved, but dopant concentration in contact area decreases
Solution Approach 1:
The preliminary dopant is implanted first to reduce diffusion and stabilize the lattice. Then the primary dopant is implanted to achieve the required high concentration in the contact area. The preliminary action of diffusion reduction does not prevent the subsequent concentration buildup, as the two dopants work in sequence with different functions.
Solution Approach 2:
The composite dopant system uses two dopants with different formation enthalpies: the preliminary dopant (lower formation enthalpy) reduces diffusion and improves junction abruptness, while the primary dopant (higher formation enthalpy) achieves high concentration in the contact area for low resistance, thereby satisfying both requirements through material composition.
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 results in reduced leakage current, lower source/drain contact resistance, and enhanced short channel control, improving device performance by achieving a higher concentration of dopants in the contact area and providing a steeper junction.
Implementation Method 1
The first dopants may have a lower formation enthalpy than the second dopants. As a result of its lower formation enthalpy, the first dopants are more attracted to and form more stable bonds with vacancies in the source/drain region.
Implementation Method 2
first dopants are implanted into a source/drain region followed by an implantation of second dopants
Data Source
AI summary
A method includes forming a source/drain region in a semiconductor fin; after forming the source/drain region, implanting first impurities into the source/drain region; and after implanting the first impurities, implanting second impurities into the source/drain region. The first impurities have a lower formation enthalpy than the second impurities. The method further includes after implanting the second impurities, annealing the source/drain region.