Graded Boron Epitaxial Source-Drain for Semiconductor Off Current Reduction
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Solution Overview
Problem
Current semiconductor devices face challenges in reducing off current and junction capacitance due to the limitations of boron concentration gradients in epitaxial layers, which affect the mobility of charge carriers and device performance.
Innovation Solution
The semiconductor device incorporates a first epitaxial layer with a lower boron concentration and a second epitaxial layer with a higher boron concentration, strategically positioned within a trench, to optimize the depth and stress characteristics of the source/drain region, thereby enhancing mobility and reducing off current and junction capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single epitaxial layer with uniform boron concentration is used, then the manufacturing process is simple, but the off current and junction capacitance cannot be effectively reduced
Solution Approach 1:
The epitaxial layer is divided into multiple distinct layers (first epitaxial layer with lower boron concentration and second epitaxial layer with higher boron concentration) to create a graded concentration profile. This segmentation allows different regions to serve different functions: the lower concentration region reduces off current while the higher concentration region manages junction capacitance, resolving the contradiction between reliability improvement and device complexity.
Solution Approach 2:
Different boron concentrations are applied to different spatial regions within the epitaxial structure. The first epitaxial layer has a lower boron concentration optimized for reducing off current in specific regions, while the second epitaxial layer has a higher boron concentration optimized for controlling junction capacitance in other regions. This local quality variation enables simultaneous optimization of multiple performance parameters without requiring a completely complex multi-layer structure.
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 effectively reduces off current and junction capacitance, allowing for increased depth of the source/drain region and improved carrier mobility, leading to enhanced operating characteristics of the semiconductor device.
Implementation Method 1
a first epitaxial layer filling a portion of the first trench, wherein a thickness of the first epitaxial layer becomes thinner closer to a sidewall of the first trench; and a second epitaxial layer filling the first trench on the first epitaxial layer, wherein a boron concentration of the second epitaxial layer is greater than a boron concentration of the first epitaxial layer
Data Source
AI summary
A semiconductor device including a first fin protruding on a substrate and extending in a first direction; a first gate electrode on the first fin, the first gate electrode intersecting the first fin; a first trench formed within the first fin at a side of the first gate electrode; a first epitaxial layer filling a portion of the first trench, wherein a thickness of the first epitaxial layer becomes thinner closer to a sidewall of the first trench; and a second epitaxial layer filling the first trench on the first epitaxial layer, wherein a boron concentration of the second epitaxial layer is greater than a boron concentration of the first epitaxial layer.