Source/Drain Doping Profile for Lower FinFET Contact Resistance
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Solution Overview
Problem
As integrated circuits shrink, the small silicide regions and contact areas between contact plugs and silicide regions lead to increased contact resistance, particularly in Fin Field-Effect Transistors (FinFETs) where fins are narrow, resulting in higher resistance.
Innovation Solution
Implanting a dopant such as gallium into the source/drain regions with a profile that has a platform concentration near the surface, reducing contact resistance by creating a consistent dopant concentration that decreases gradually into the region, and forming conductive features like contacts and silicide regions to enhance conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the integrated circuit is downsized to increase integration density, then the device size is reduced and productivity is improved, but the contact area between contact plugs and silicide regions becomes smaller and contact resistance increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform dopant concentration profile within the source/drain region. Specifically, a first dopant concentration is introduced at the interface with the conductive feature, which is higher than the second dopant concentration in the bulk of the source/drain region. This localized high-concentration dopant region improves contact resistance at the critical interface area without affecting the overall device dimensions, thus resolving the contradiction between downsizing and maintaining contact quality.
Solution Approach 2:
The patent changes the dopant concentration parameter by introducing a gradient profile rather than a uniform distribution. The first dopant concentration at the conductive feature interface is specifically engineered to be higher than the second dopant concentration in the source/drain region. This parameter change optimizes the electrical properties at the contact interface while maintaining the downsized device geometry, addressing the contact resistance issue without sacrificing integration density.
2Area of moving object
If the fin width is reduced to increase transistor density, then the device size is reduced, but the contact area between contacts and fins becomes very small leading to higher resistance
Solution Approach 1:
The patent addresses the narrow fin contact area by implementing local quality enhancement through a concentrated dopant region. A first dopant concentration is introduced specifically at the fin-contact interface area, creating a high-concentration zone that compensates for the reduced contact area. This localized dopant enhancement improves contact resistance without requiring larger fin dimensions, thus maintaining high transistor density while resolving the contact resistance problem.
3Ease of manufacture
If a uniform dopant concentration is used in source/drain regions, then the manufacturing process is simple, but the contact resistance cannot be effectively reduced
Solution Approach 1:
The patent resolves the contradiction between manufacturing simplicity and contact resistance reduction by implementing local quality through a two-concentration dopant profile. The process introduces a first dopant concentration at the conductive feature interface and a second, lower dopant concentration in the bulk source/drain region. This can be achieved through selective doping techniques such as ion implantation with appropriate masking or in-situ doping during selective epitaxial growth, maintaining reasonable manufacturing complexity while effectively reducing contact resistance.
Solution Approach 2:
The patent applies preliminary action by pre-establishing the dopant concentration gradient before final device assembly. The higher first dopant concentration is introduced at the contact interface region in advance, creating an optimized electrical profile that prepares the structure for subsequent processing steps. This preliminary dopant distribution ensures low contact resistance is achieved without requiring complex post-processing adjustments.
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 effectively reduces contact resistance by maintaining a high dopant concentration at the surface and within the source/drain regions, improving the electrical connectivity and performance of FinFETs and other semiconductor devices.
Implementation Method 1
Implanting a dopant such as gallium into the source/drain regions with a profile that has a platform concentration near the surface
Data Source
AI summary
The present disclosure relates generally to doping for conductive features in a semiconductor device. In an example, a structure includes an active region of a transistor. The active region includes a source/drain region, and the source/drain region is defined at least in part by a first dopant having a first dopant concentration. The source/drain region further includes a second dopant with a concentration profile having a consistent concentration from a surface of the source/drain region into a depth of the source/drain region. The consistent concentration is greater than the first dopant concentration. The structure further includes a conductive feature contacting the source/drain region at the surface of the source/drain region.