SiGe Linear Active Regions for Complementary MISFET Strain
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Solution Overview
Problem
Current semiconductor technologies face challenges in achieving high mobility for both p- and n-channel MISFETs on the same substrate, particularly due to difficulties in producing uniaxial strain channels with optimal current direction and surface orientation, which limits the construction of complementary MISFETs.
Innovation Solution
A semiconductor device is developed with a (110) surface of Si1-xGex, featuring n-channel and p-channel MISFETs with uniaxial tensile and compressive strain respectively, formed using selective epitaxial growth methods to create linear active regions with (311) or (111) facets, allowing for improved lattice relaxation and strain alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If Fin structure is produced on (100) surface using elastic uniaxial stress relaxation, then uniaxial strain channel is obtained, but it is difficult to produce both p- and n-channel MISFETs on the same substrate
Solution Approach 1:
The patent changes the surface orientation parameter from conventional (100) to (110), and modifies the strain application method from elastic stress relaxation to plastic deformation during selective epitaxial growth. This enables uniaxial strain in the <110> direction that is compatible with both p- and n-channel MISFETs on the same substrate, resolving the contradiction between achieving uniaxial strain and constructing complementary devices.
2Speed
If channel direction is taken in <−110> direction with high mobility, then carrier mobility is improved, but it is difficult to achieve high mobility for both p- and n-channel types on the same (100) substrate
Solution Approach 1:
The patent introduces asymmetric strain conditions by forming SiGe layers with different germanium compositions (x and y where x≠y) on opposite sides of the channel. This asymmetric composition distribution creates uniaxial strain in the <110> direction that simultaneously enhances electron mobility in n-channel and hole mobility in p-channel MISFETs, enabling both types to achieve high mobility on the same substrate.
3Manufacturing precision
If selective epitaxial growth is used to form linear semiconductor region with facets, then lattice relaxation and strain alignment are improved, but manufacturing process complexity increases
Solution Approach 1:
The patent applies local quality by creating distinct regions with different SiGe compositions (first SiGe layer with composition x, second SiGe layer with composition y) on either side of the channel region. The selective epitaxial growth is performed locally in specific areas to form linear semiconductor regions with controlled facets, achieving precise lattice relaxation and strain alignment while maintaining overall process feasibility through localized rather than global complexity.
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 enables the formation of complementary MISFETs with high mobility channels on the same substrate, optimizing current direction and reducing lattice defects, thereby enhancing drive current and carrier mobility.
Implementation Method 1
forming, by a selective epitaxial growth method, a linear semiconductor region on the (110) surface
Implementation Method 2
providing uniaxial strain in a <−100> direction of the linear semiconductor region
Data Source
AI summary
A semiconductor device includes a semiconductor substrate having, on a surface thereof, a (110) surface of Si1-xGex (0.25≦̸x≦̸0.90), and n-channel and p-channel MISFETs formed on the (110) surface, each MISFET having a source region, a channel region and a drain region. Each MISFET has a linear active region which is longer in a [−110] direction than in a [001] direction and which has a facet of a (311) or (111) surface, the source region, the channel region and the drain region are formed in this order or in reverse order in the [−110] direction of the linear active region, the channel region of the n-channel MISFET is formed of Si and having uniaxial tensile strain in the [−110] direction, and the channel region of the p-channel MISFET being formed of Si1-yGey (x<y≦̸1) and having uniaxial compressive strain in the [−110] direction.