Silicon Seed Layer Suppresses {111} Facets in SiGe Epitaxial Growth
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Solution Overview
Problem
Fully strained channels in CMOS devices can develop defects like {111} facets during SiGe epitaxial growth, which act as scattering centers and offset mobility benefits, particularly in p-type field effect transistors.
Innovation Solution
A fabrication method that includes forming a carbon-doped region, growing a silicon epitaxial layer, creating a recess, and using a silicon seed layer to suppress the formation of {111} facets during SiGe epitaxial growth, ensuring a fully strained channel region with improved carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiGe epitaxial growth is performed to form a fully strained channel, then carrier mobility is improved, but {111} facets form as defects that act as scattering centers and offset the mobility benefits
Solution Approach 1:
A silicon seed layer is formed on the carbon-doped region before SiGe epitaxial growth. This preliminary layer suppresses the formation of {111} facets during subsequent SiGe growth, preventing the harmful defects from forming in the first place while maintaining the strain-induced carrier mobility improvement
Solution Approach 2:
The silicon seed layer acts as an intermediary between the carbon-doped region and the SiGe epitaxial layer. It mediates the epitaxial growth process by providing a template that prevents {111} facet formation, allowing the SiGe layer to grow without defects while preserving the fully strained channel structure
2Productivity
If channel length is scaled down to improve device density, then drive current enhancement is maintained through strain, but defect formation becomes more significant and offsets mobility benefits
Solution Approach 1:
The silicon seed layer is formed before SiGe epitaxial growth to prevent {111} facet formation. This preliminary protective layer ensures that even in scaled devices where defects have greater impact, the fully strained channel maintains its carrier mobility improvement without being compromised by scattering centers
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 method effectively suppresses the formation of {111} facets, enhancing carrier mobility and reducing channel resistance in CMOS devices, thereby maintaining strain-induced drive current enhancements even with scaled channel lengths.
Implementation Method 1
forming a second epitaxial layer in the recess, where forming the second epitaxial layer includes: forming a seed layer in the recess and forming the second epitaxial layer on the seed layer to fill the recess
Data Source
AI summary
The present disclosure describes an exemplary fabrication method of a p-type fully strained channel that can suppress the formation of {111} facets during a silicon germanium epitaxial growth. The exemplary method includes the formation of silicon epitaxial layer on a top, carbon-doped region of an n-type region. A recess is formed in the silicon epitaxial layer via etching, where the recess exposes the top, carbon-doped region of the n-type region. A silicon seed layer is grown in the recess, and a silicon germanium layer is subsequently epitaxially grown on the silicon seed layer to fill the recess. The silicon seed layer can suppress the formation of growth defects such as, for example, {111} facets, during the silicon germanium epitaxial layer growth.