SiGe Source/Drain Structure for Strained Channel Mobility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor technology, the increased volume of the source/drain (S/D) region to reduce parasitic resistance and contact resistance leads to a decrease in induced strain in the transistor's channel, degrading performance and speed, as it penetrates through the high mobility material layer and underlying substrate.
Innovation Solution
A method and structure where the S/D region is epitaxially grown with a higher germanium atomic concentration than the channel layer, ensuring it does not penetrate through the channel layer, thus maintaining the strain and enhancing mobility, involving a p-type S/D region with a SiGe layer that protrudes into the epitaxially-grown channel layer without cutting through it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the volume of the source/drain region is increased to reduce parasitic resistance and contact resistance, then resistance is reduced, but the induced strain in the transistor's channel decreases, degrading performance and speed
Solution Approach 1:
The source/drain region is designed with a non-uniform composition gradient, where the germanium concentration varies spatially from the surface to the bulk. This local quality variation allows the S/D region to provide strain to the channel while maintaining low resistance, as the higher germanium concentration near the channel interface enhances strain effects without requiring excessive overall volume that would penetrate and degrade the channel layer.
Solution Approach 2:
The invention changes the compositional parameters of the source/drain region by introducing a graded germanium concentration profile. Instead of a uniform composition, the germanium atomic percentage increases from the bulk toward the channel interface, which modifies the physical properties to simultaneously achieve low resistance and effective strain induction without channel penetration.
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 maintains the induced strain in the transistor's channel, boosting channel mobility and performance while reducing resistance, thereby improving the speed and reliability of the transistor.
Implementation Method 1
A method and structure where the S/D region is epitaxially grown with a higher germanium atomic concentration than the channel layer
Implementation Method 2
ensuring it does not penetrate through the channel layer, thus maintaining the strain and enhancing mobility
Data Source
AI summary
The present disclosure describes a semiconductor structure and a method for forming the same. The method can include forming a fin structure over a substrate. The fin structure can include a channel layer and a buffer layer between the channel layer and the substrate. The method can further include forming a recess structure in the channel layer. The recess structure can include a bottom surface over the buffer layer. The method can further include forming a first epitaxial layer over the bottom surface of the recess structure. The first epitaxial layer can include a first atomic concentration of germanium. The method can further include forming a second epitaxial layer over the first epitaxial layer. The second epitaxial layer can include a second atomic concentration of germanium greater than the first atomic concentration of germanium.