Dual-Dopant Source/Drain Regions for Abrupt Junctions
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving improved junction abruptness and reduced source/drain contact resistance due to diffusion issues and drain-induced barrier lowering (DIBL) in advanced process nodes.
Innovation Solution
Implanting two different types of dopants into the source/drain region, where the first dopants have a lower formation enthalpy than the second dopants, forming more stable bonds with vacancies and reducing diffusion, thereby allowing for a higher concentration of the second dopants and improving junction abruptness and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single dopant type is used in source/drain regions, then the doping process is simple, but junction abruptness is poor and contact resistance is high
Solution Approach 1:
The dopant profile is segmented into multiple regions with different dopant types: first dopants (e.g., arsenic) are implanted in the lower portion of the source/drain region, while second dopants (e.g., phosphorus) are implanted in the upper portion. This segmentation creates distinct dopant zones that improve junction abruptness at the semiconductor fin interface while maintaining higher dopant concentration where needed for low contact resistance.
Solution Approach 2:
Different dopant types are applied to different locations within the source/drain region based on local requirements. The first dopants with lower formation enthalpy are placed in the lower region where they form stable bonds with vacancies and improve junction characteristics, while the second dopants are placed in the upper region to provide high carrier concentration for low contact resistance. This local differentiation optimizes both junction abruptness and contact properties.
2Reliability
If high concentration of dopants is used to reduce contact resistance, then contact resistance decreases, but dopant diffusion increases and junction abruptness deteriorates
Solution Approach 1:
The high concentration dopants (second dopants) are segmented into the upper portion of the source/drain region, separated from the junction interface by the first dopant layer. This allows the upper region to have high dopant concentration for low contact resistance while the lower region near the junction maintains abruptness through the first dopant's lower diffusion characteristics.
Solution Approach 2:
The first dopants act as an intermediary layer between the semiconductor fin and the high concentration second dopants. The first dopants with lower formation enthalpy form stable bonds that reduce vacancy-mediated diffusion, thereby preventing the second dopants from diffusing into the channel region and degrading junction abruptness, while still allowing high overall dopant concentration for low contact resistance.
3Manufacturing precision
If conventional single dopant implantation is used, then the process is straightforward, but short channel control is insufficient due to DIBL effects
Solution Approach 1:
The doping profile is segmented to create a non-uniform dopant distribution that optimizes short channel control. First dopants are concentrated in the lower region near the junction to suppress drain-induced barrier lowering (DIBL) effects, while second dopants are concentrated in the upper region. This segmented profile provides better electrostatic control than uniform doping.
Solution Approach 2:
The doping parameters are changed spatially within the source/drain region. The first dopants have lower formation enthalpy and are implanted at specific energies to achieve desired depth distribution, while the second dopants are implanted at different energies and concentrations. These parameter variations create an optimized doping profile that improves short channel control while managing the complexity through systematic parameter control.
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
The dual dopant approach enhances junction abruptness and reduces diffusion, leading to lower source/drain contact resistance and improved short channel control in semiconductor devices.
Implementation Method 1
The first dopants may have a lower formation enthalpy than the second dopants. For example, the first dopants may comprise arsenic, carbon, antimony, or the like, and the second dopants may comprise phosphorus, or the like. 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
Various embodiments include implanting two different types of dopants into a source/drain region for improved junction abruptness (e.g., reduced leakage current) and reduced source/drain contact resistance. In an embodiment method, 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.