SiGe Source-Drain Layering for Uniform Siliciding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing method of manufacturing semiconductor devices using a silicon-germanium (SiGe) layer to apply stress to the channel region for enhanced carrier mobility faces instability in siliciding reactions, leading to non-uniform silicide layer formation and increased leakage current due to abnormal growth.
Innovation Solution
A method involving the sequential growth of a first SiGe layer with higher germanium concentration for stress application, followed by a second layer with lower germanium concentration or a silicon layer to stabilize the siliciding reaction and prevent abnormal growth, ensuring a uniform membrane-like silicide layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon-germanium (SiGe) layer is used to apply stress to the channel region, then carrier mobility is enhanced, but siliciding reaction becomes unstable leading to non-uniform silicide layer formation
Solution Approach 1:
The source/drain structure is segmented into multiple layers: a first SiGe layer (higher Ge concentration) for stress application and a second SiGe layer (lower Ge concentration) for stable silicide formation. This segmentation allows each layer to fulfill its specific function independently, resolving the contradiction between stress application and uniform silicide formation
Solution Approach 2:
Different regions of the source/drain structure are assigned different Ge concentrations: the first layer has higher Ge concentration (e.g., 10-30%) for stress application to the channel, while the second layer has lower Ge concentration (e.g., 0-10%) for stable silicide formation. This local quality differentiation enables simultaneous achievement of carrier mobility enhancement and uniform silicide layer formation
2Reliability
If a silicon-germanium (SiGe) layer is used to apply stress to the channel region, then carrier mobility is enhanced, but leakage current increases due to abnormal silicide layer growth
Solution Approach 1:
The source/drain structure is divided into functional layers: the first SiGe layer provides stress for carrier mobility enhancement, while the second SiGe layer with lower Ge concentration prevents abnormal silicide growth that causes leakage current. This segmentation isolates the stress function from the silicide formation issues
Solution Approach 2:
The second SiGe layer acts as an intermediary between the high-Ge first layer and the metal film, providing a controlled interface for silicide formation. This intermediary layer prevents direct interaction between the high-Ge region and metal that would cause abnormal growth and leakage current
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 stabilizes the siliciding reaction, forms a uniform silicide layer, reduces contact resistance, and suppresses leakage current, resulting in enhanced transistor characteristics.
Implementation Method 1
a first layer 21 including a silicon-germanium (SiGe) layer is epitaxially grown on the dug-down surface of the silicon substrate
Implementation Method 2
a heat treatment is conducted, whereby the surface side of the gate electrode 13 and the surface side of the silicon-germanium layer 17 are silicided, to form a silicide layer S including nickel silicide
Data Source
AI summary
First, in a first step, a gate electrode is formed over a silicon substrate, with a gate insulation film therebetween. Next, in a second step, etching with the gate electrode as a mask is conducted so as to dig down a surface layer of the silicon substrate. Subsequently, in a third step, a first layer including an SiGe layer is epitaxially grown on the dug-down surface of the silicon substrate. Next, in a fourth step, a second layer including an SiGe layer lower than the first layer in Ge concentration or including an Si layer is formed on the first layer. Thereafter, in a fifth step, at least the surface side of the second layer is silicided, to form a silicide layer.