Dual-Dopant Source/Drain Regions for Low-Diffusion Fin Junctions
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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, which affect the integration density and performance of semiconductor devices.
Innovation Solution
The implementation of a dual-dopant implantation process, where first dopants with lower formation enthalpy (such as arsenic or antimony) are implanted into the source/drain regions followed by second dopants (like phosphorous dimer) to form more stable bonds with vacancies, reducing diffusion and enhancing junction abruptness and contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional 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 implantation steps, each introducing a different dopant species (e.g., phosphorous, arsenic, antimony) with specific concentration profiles. This segmentation allows precise control over the dopant distribution, achieving abrupt junctions by combining the advantages of different dopants rather than relying on a single dopant implantation step.
Solution Approach 2:
The invention changes multiple parameters simultaneously including dopant species type, implantation energy, implantation dose, and thermal processing conditions. By optimizing these parameters in combination, the process achieves reduced diffusion while maintaining abrupt junction profiles, resolving the contradiction between manufacturing precision and process complexity.
2Reliability
If dopant concentration is increased to reduce contact resistance, then contact resistance decreases, but diffusion increases
Solution Approach 1:
The invention uses composite dopant profiles combining multiple dopant species (e.g., phosphorous-arsenic or phosphorous-antimony combinations) in the source/drain regions. This composite approach allows the first dopant to provide high concentration for low contact resistance while the second dopant with lower diffusion coefficient stabilizes the profile and reduces unwanted diffusion, thus achieving both low contact resistance and compositional stability.
Solution Approach 2:
The second dopant acts as an intermediary that modifies the diffusion behavior of the first dopant. By introducing a dopant with different diffusion characteristics, the invention controls and reduces the overall diffusion while maintaining the beneficial low contact resistance properties, effectively mediating between conflicting requirements.
3Productivity
If feature size is reduced to improve integration density, then more components fit in given area, but DIBL effects worsen
Solution Approach 1:
The invention applies different dopant concentrations and species locally within the source/drain regions adjacent to the channel. By creating locally optimized dopant profiles with abrupt transitions at the channel interface, the invention improves short channel control and reduces DIBL effects in scaled devices, allowing higher integration density without sacrificing device reliability.
Solution Approach 2:
The dopant implantation and thermal processing steps are performed as preliminary actions before final device assembly and operation. By pre-establishing the optimal dopant profiles and junction characteristics in advance, the invention prepares the device structure to resist DIBL effects and maintain good short channel control even when feature sizes are reduced for higher 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 results in improved junction abruptness, reduced diffusion of dopants, and lower source/drain contact resistance, effectively addressing the challenges of DIBL and enhancing device performance, including reduced leakage current and improved short channel control.
Implementation Method 1
implanting first impurities into the source/drain region; after implanting the first impurities, implanting second impurities into the source/drain region
Implementation Method 2
after implanting the second impurities, annealing the source/drain region
Implementation Method 3
The first dopants may have a lower formation enthalpy than the second dopants... the first dopants are more attracted to and form more stable bonds with vacancies in the source/drain region... By reducing diffusion of the second dopant
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.