Silicide-Embedded Source/Drain Structure for Low Contact Resistance
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Solution Overview
Problem
Existing semiconductor devices face challenges in scaling down while maintaining efficient electrical performance due to high contact resistance and strain management in the channel region, which affects electron and hole mobility.
Innovation Solution
A semiconductor device with a silicide-embedded stressor source and drain structure, where a silicide layer is shaped as a pocket profile extending into the source/drain region to reduce contact resistance while maintaining strain in the channel region, using epitaxially grown layers with graded germanium concentration to induce mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact area is enlarged to reduce contact resistance, then contact resistance decreases, but the strain in the channel region is released
Solution Approach 1:
The silicide layer is selectively formed only in specific regions of the source/drain structure (at the interface with the barrier layer and in the semiconductor substrate) while leaving other regions free of silicide. This local differentiation allows contact resistance to be reduced at contact points while maintaining strain in the channel region where silicide is absent.
Solution Approach 2:
The source/drain region is divided into multiple functional zones: a barrier layer region, a silicide layer region, and a strain-maintaining region. The silicide layer itself is segmented into different portions with different functions - one portion for reducing contact resistance at the interface, another for maintaining electrical conductivity, while avoiding the channel region to preserve strain.
2Volume of moving object
If device size is reduced for scaling, then device density increases, but electron and hole mobility deteriorates
Solution Approach 1:
The invention changes the material composition parameter by introducing a graded germanium concentration in the semiconductor layer. The germanium concentration varies from a first value at the interface with the barrier layer to a second value at the top surface, creating a composition gradient that maintains carrier mobility even as device dimensions are reduced for scaling.
Solution Approach 2:
The source/drain structure uses a composite material system consisting of a barrier layer, a semiconductor layer with graded germanium concentration, and a silicide layer. This composite structure combines the advantages of different materials - the barrier layer provides mechanical support, the graded semiconductor layer maintains strain and mobility, and the silicide layer provides low contact resistance.
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 design significantly reduces contact resistance and maintains strain in the channel region, leading to increased carrier mobility and drive current, thereby enhancing device performance.
Implementation Method 1
a silicide layer in the stressor layer. The silicide layer extends from a top surface of the raised source/drain region and ends below the interface by a predetermined depth
Implementation Method 2
using epitaxially grown layers with graded germanium concentration to induce mechanical stress
Implementation Method 3
Different types of strain, including expansive strain, uniaxial tensile strain, and compressive strain, have been introduced into channel regions of various types of transistors in order to determine their effect on electron and/or hole mobility
Data Source
AI summary
A semiconductor device includes a gate structure located on a substrate; and a raised source/drain region adjacent to the gate structure. An interface is between the gate structure and the substrate. The raised source/drain region includes a stressor layer providing strain to a channel under the gate structure; and a silicide layer in the stressor layer. The silicide layer extends from a top surface of the raised source/drain region and ends below the interface by a predetermined depth. The predetermined depth allows the stressor layer to maintain the strain of the channel.