Bi-portioned Junction for FinFET Contact Resistance and Shorting
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Solution Overview
Problem
In FinFET semiconductor structures, there is a trade-off between forming a good contact with low contact resistance and preventing device shorting due to high dopant levels in the source/drain region, which can diffuse under the gate spacer during extension formation anneal.
Innovation Solution
A bi-portioned junction is formed with a higher dopant concentration in the inner portion for low contact resistance and a lower dopant concentration in the outer portion to prevent shorting, achieved by epitaxial growth and selective doping, allowing for a controlled diffusion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high dopant level is used in the source/drain region, then contact resistance is reduced, but device shorting occurs due to dopant diffusion under the gate spacer
Solution Approach 1:
The source/drain region is segmented into two distinct portions with different dopant concentrations: an inner portion adjacent to the channel region with lower dopant concentration to prevent diffusion and shorting, and an outer portion extending toward the contact with higher dopant concentration to reduce contact resistance. This segmentation allows each portion to fulfill its specific function without compromising the other.
Solution Approach 2:
Different dopant concentrations are applied to different spatial locations within the source/drain region. The inner portion near the channel has lower dopant concentration (e.g., 1E19 to 1E20 atoms/cm³) to minimize diffusion, while the outer portion near the contact has higher dopant concentration (e.g., 1E20 to 1E21 atoms/cm³) to improve electrical contact. This local differentiation optimizes both shorting prevention and contact resistance.
2Reliability
If a high dopant level is used in the source/drain region, then a good contact is formed, but the abruptness of the junction is reduced due to diffusion
Solution Approach 1:
The source/drain region is divided into inner and outer portions with distinct dopant concentrations. The inner portion maintains lower doping levels that prevent excessive diffusion, preserving junction abruptness at the critical channel interface, while the outer portion uses higher doping levels optimized for contact quality without affecting the junction profile at the channel boundary.
Solution Approach 2:
The dopant concentration profile is locally optimized: the inner portion adjacent to the channel region maintains lower concentration to preserve abrupt junction characteristics, while the outer portion has higher concentration tailored for low-resistance contact. This local quality differentiation allows simultaneous achievement of abrupt junctions and good contacts.
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 maintains a high dopant level in the source/drain regions for improved contact resistance while minimizing the risk of device shorting, enabling effective junction formation between the channel and source/drain regions.
Implementation Method 1
forming an inner junction portion upon the recessed semiconductor substrate, and forming an outer junction portion upon the recessed semiconductor substrate
Implementation Method 2
the more abrupt the junction then better. A high dopant level in the SD region is typically desirable to form a good contact with and to achieve a low contact resistance between the SD region and a SD contact. Unfortunately the high dopant level close to the gate may lead to high diffusion of dopant under the gate spacer during extension formation anneal
Data Source
AI summary
A semiconductor structure, such as a FinFET, etc., includes a bi-portioned junction. The bi-portioned junction includes a doped outer portion and a doped inner portion. The dopant concentration of the outer portion is less than the dopant concentration of the inner portion. An electrical connection is formed by diffusion of the dopants within outer portion into a channel region and diffusion of the dopants within the outer portion into the inner region. A low contact resistance is achieved by a contact electrically contacting the relatively higher doped inner portion while device shorting is limited by the relatively lower doped outer portion.