MOSFET Source/Drain Ge Gradient for Lower Contact Resistance
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Solution Overview
Problem
As semiconductor devices trend towards higher integration and smaller sizes, reducing contact resistance while maintaining electrical characteristics is a challenge, particularly in three-dimensional MOSFET structures.
Innovation Solution
A semiconductor device with a source/drain region doped with germanium, featuring a shallow doping region with a high concentration of germanium that gradually decreases from the surface towards the substrate, combined with an epitaxial region, to optimize contact resistance and electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size of MOSFET is decreased to achieve higher integration, then device density increases, but contact resistance increases and electrical characteristics deteriorate
Solution Approach 1:
The patent applies local quality by creating a shallow doping region with high germanium concentration specifically at the upper portion of the source/drain region where the contact structure interfaces. This localized high Ge concentration (95-100 at%) reduces contact resistance at the critical contact interface without requiring uniform doping throughout the entire source/drain region, thereby maintaining low contact resistance while preserving the miniaturized device structure for high integration density.
Solution Approach 2:
The patent changes the germanium concentration parameter vertically within the source/drain region, creating a gradient from high concentration (95-100 at%) at the upper surface to lower concentration towards the substrate. This parameter variation optimizes the electrical characteristics by providing high carrier concentration at the contact interface for low resistance while maintaining the physical dimensions required for high device density integration.
2Reliability
If germanium concentration is increased in the source/drain region to reduce contact resistance, then contact resistance decreases, but manufacturing complexity increases
Solution Approach 1:
The patent segments the source/drain region into two distinct zones: a shallow doping region at the upper portion with high germanium concentration (95-100 at%) and a bulk region below with lower germanium concentration. This segmentation allows the high Ge concentration to be confined only where needed for contact resistance reduction, simplifying the overall doping structure compared to uniform high-concentration doping throughout the entire source/drain region.
Solution Approach 2:
The patent applies partial action by doping germanium excessively (95-100 at%) only in the shallow upper region (depth of 2-6 nm) where contact resistance is critical, rather than applying moderate doping uniformly throughout the entire source/drain region. This partial excessive doping achieves the contact resistance reduction goal with simpler process control than attempting uniform optimization.
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
The approach effectively reduces contact resistance and maintains or improves electrical characteristics by strategically doping germanium in the source/drain region, enhancing the performance of semiconductor devices with three-dimensional structures.
Implementation Method 1
a shallow doping region that is doped with germanium (Ge) and is in an upper region including an upper surface of the source/drain region
Implementation Method 2
an epitaxial region below the shallow doping region
Data Source
AI summary
A semiconductor device includes an active region on a substrate, a gate structure on the substrate and intersecting the active region, a source/drain region on the active region on both sides of the gate structure and including silicon (Si), and a contact structure on the source/drain region. The source/drain region includes a shallow doping region doped with germanium (Ge) and is in an upper region including an upper surface of the source/drain region. A concentration of germanium (Ge) in the shallow doping region gradually decreases from the upper surface of the source/drain region toward an upper surface of the substrate in a direction that is perpendicular to an upper surface of the substrate.