FinFET With In-Situ Doped Source And Drain Regions
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Solution Overview
Problem
Conventional planar FETs have reached scaling limits, necessitating the development of unconventional geometries like finFETs to continue performance improvements in semiconductor devices, which requires innovative methods for forming fin structures with precise doping and channel replacement to achieve optimal performance.
Innovation Solution
The method involves forming fin structures from in-situ doped semiconductor layers on a substrate, creating a sacrificial gate structure, removing it to expose the channel, and replacing the sacrificial channel with a functional channel region, while forming epitaxial merge structures on the source and drain regions to achieve uniform and abrupt doping profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional planar FET scaling is continued, then device dimensions are reduced, but device performance improvements reach fundamental limits
Solution Approach 1:
The patent transitions from planar FET geometry to finFET geometry, utilizing a vertical fin structure that extends into the third dimension. This dimensional change allows the gate to control current through multiple surfaces (top and sidewalls), effectively increasing the channel area without increasing the planar footprint, thus overcoming the scaling limits of conventional planar devices
2Quantity of substance
If in-situ doped semiconductor layers are used to form fin structures, then dopant concentration is increased, but doping uniformity and junction abruptness must be maintained
Solution Approach 1:
The patent segments the fin structure into distinct doped regions (source and drain) separated by an undoped channel region. This segmentation is achieved by selectively removing portions of the in-situ doped layer to create sacrificial channel portions, which are then replaced with undoped material. This allows high dopant concentration in source/drain regions while maintaining abrupt junctions and undoped channel for optimal carrier control
Solution Approach 2:
The patent applies different doping qualities to different regions of the fin structure. The source and drain regions have high dopant concentration from the in-situ doped layer, while the channel region is made undoped by replacing the sacrificial channel portion. This local differentiation of doping quality enables simultaneous optimization of source/drain conductivity and channel carrier control
3Reliability
If sacrificial channel portion is removed and replaced with functional channel region, then channel control is improved, but process complexity increases
Solution Approach 1:
The patent incorporates doping into the initial epitaxial growth of the fin structure using in-situ doped semiconductor layers. This preliminary doping action occurs before the fin structure is fully formed and before the sacrificial channel removal process. By pre-doping the source and drain regions during epitaxial growth, the patent eliminates the need for subsequent high-temperature doping steps that would be required after sacrificial channel removal, thereby reducing overall process complexity while maintaining improved channel 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
This approach enables the formation of FinFETs with high dopant concentration and low defect density in the source and drain regions, resulting in a very abrupt junction with the channel, enhancing device performance by optimizing doping and reducing diffusion tails.
Implementation Method 1
forming fin structures from an in-situ doped semiconductor layer that is present on a semiconductor substrate
Implementation Method 2
Epitaxial merge structures may then be formed on the source and drain region portions of the fin structures
Data Source
AI summary
A method of forming a semiconductor device that includes forming an in-situ doped semiconductor material on a semiconductor substrate, and forming fin structures from the in-situ doped semiconductor material. A sacrificial channel portion of the fin structures may be removed, wherein a source region and a drain region portion of the fin structures of the in-situ doped semiconductor material remain. The sacrificial channel portion of the fin structure may then be replaced with a functional channel region.