Source/Drain Epitaxial Structure for Leakage Control in GAA Semiconductors
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Solution Overview
Problem
Existing semiconductor devices face challenges in effectively controlling short channel effects and minimizing leakage currents, particularly due to the diffusion of impurities from the source/drain regions into the gate structures.
Innovation Solution
The semiconductor device incorporates a source/drain pattern with a first epitaxial region doped with antimony or bismuth, a second epitaxial region doped with arsenic, and a third epitaxial region doped with phosphorus, where the first epitaxial region has a thickness that increases and decreases away from the gate structures, thereby controlling impurity diffusion and reducing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional source/drain pattern with uniform impurity doping is used, then the manufacturing process is simple, but leakage currents increase due to impurity diffusion into gate structures
Solution Approach 1:
The source/drain pattern is segmented into multiple epitaxial regions (first, second, and third epitaxial regions) with different impurity concentrations and compositions. This segmentation creates a gradient structure where impurity concentration decreases from bottom to top, effectively blocking impurity diffusion into gate structures while maintaining electrical functionality.
Solution Approach 2:
Different regions of the source/drain pattern are assigned different local qualities through selective impurity doping. The first epitaxial region near the gate has heavy doping with low-diffusion impurities (Sb or Bi) to block diffusion, while upper regions have lighter doping to maintain conductivity, creating optimal local properties for each functional requirement.
2Reliability
If heavy metal impurities (Sb, Bi) are used in the first epitaxial region, then impurity diffusion is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The first epitaxial region with heavy metal impurities (Sb or Bi) is formed in advance during the epitaxial growth process, before subsequent doping steps. This preliminary formation of the diffusion barrier layer ensures that the low-diffusion impurities are already in place to prevent later impurity migration, reducing the need for precise control of subsequent processing steps.
Solution Approach 2:
The source/drain structure uses composite material composition with multiple types of impurities distributed across different epitaxial regions. The combination of heavy metals (Sb, Bi) in the first region with lighter impurities in upper regions creates a composite doping profile that leverages the low diffusion coefficient of heavy metals while maintaining overall electrical performance.
3Reliability
If the thickness of the bottom part of the first epitaxial region is increased, then the path length for impurity diffusion is increased, but the device area increases
Solution Approach 1:
The solution extends from a two-dimensional uniform doping approach to a three-dimensional graded doping structure. By varying impurity concentration and composition through the vertical dimension (creating multiple epitaxial regions with different properties), the patent achieves extended diffusion path length without proportionally increasing the horizontal device area.
Solution Approach 2:
The impurity concentration and type are changed as a function of position through the epitaxial regions. The first epitaxial region uses high concentrations of low-diffusion impurities (Sb, Bi), while upper regions use lower concentrations of more mobile impurities, creating a parameter gradient that blocks diffusion without requiring excessive physical thickness.
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 configuration enhances the control of short channel effects and minimizes leakage currents by increasing the path length for impurity diffusion and utilizing heavy metals with lower diffusion coefficients, thereby improving the reliability and performance of the semiconductor device.
Implementation Method 1
controlling impurity diffusion and reducing leakage currents
Implementation Method 2
a thickness of the bottom part of the first epitaxial region increases and decreases away from the gate structures in the second direction
Data Source
AI summary
A semiconductor includes an active pattern with a lower pattern and sheet patterns spaced apart from the lower pattern in a first direction, a source/drain pattern on the lower pattern, the source/drain pattern being in contact with the sheet patterns, and gate structures on opposite sides of the source/drain pattern, the gate structures being spaced apart from each other along a second direction and including gate electrodes that surround the sheet patterns, wherein the source/drain pattern includes a first epitaxial region having at least one of antimony and bismuth, the first epitaxial region having a bottom part in contact with the lower pattern, but not with the sheet patterns, and a thickness of the bottom part increasing and decreasing away from the gate structures in the second direction, and a second epitaxial region on the first epitaxial region, the second epitaxial region including phosphorus.