Metallic Gate Strain Engineering for Charge Carrier Mobility
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Solution Overview
Problem
Conventional techniques for fabricating metal-gate semiconductor devices often fail to simultaneously induce both tensilely strained and compressively strained channels, and require a large number of processing steps and metallic materials.
Innovation Solution
The integration of semiconductor devices with gates that include three or fewer metallic materials, where a same metallic material is shared between the gates of both NFET and PFET, or where the gates have different metallic materials, to achieve both tensilely strained and compressively strained channels, utilizing work-function layers to modulate stress applied to the channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional techniques are used to fabricate metal-gate semiconductor devices, then both tensilely strained and compressively strained channels can be achieved, but a large number of processing steps and metallic materials are required
Solution Approach 1:
The patent applies universality by using a single metallic gate material that can serve multiple functions: inducing tensile strain in NFET channels, inducing compressive strain in PFET channels, and providing work function modulation. This is achieved by controlling the deposition conditions and thickness of the metallic layer, allowing one material to replace what would traditionally require multiple different materials and processing steps.
Solution Approach 2:
The patent employs parameter changes by modifying the physical and chemical properties of the metallic gate material through controlled deposition parameters (temperature, pressure, thickness). By changing these parameters, the same metallic material can induce different types of strain (tensile or compressive) depending on the specific device region, thereby reducing the number of materials needed while maintaining strain control capability.
2Adaptability or versatility
If different metallic materials are used for NFET and PFET gates, then both tensilely strained and compressively strained channels can be achieved, but the device complexity increases
Solution Approach 1:
The patent uses a universal metallic gate material that can induce both tensile and compressive strain through controlled deposition. This single material replaces what would traditionally require two or more different metallic materials, thereby reducing device complexity while maintaining the ability to control strain in both NFET and PFET devices.
Solution Approach 2:
The patent merges the functions of multiple metallic materials into a single metallic layer. By combining the strain-inducing capability and work function modulation into one material system, the patent reduces the number of components and simplifies the device structure while achieving the same functional outcomes.
3Adaptability or versatility
If implantation techniques are used to form strained channels, then both tensilely strained and compressively strained regions can be created, but very low temperatures are required during fabrication
Solution Approach 1:
The patent replaces the mechanical implantation process with a deposition-based approach. Instead of physically implanting atoms at low temperatures, the patent uses controlled deposition of metallic materials that naturally induce strain through lattice mismatch. This substitution eliminates the need for very low temperature processing while achieving the same strain formation capability.
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 allows for the efficient fabrication of integrated circuits with both tensilely strained and compressively strained channels using a reduced number of processing steps and metallic materials, enhancing charge carrier mobility and improving device performance.
Implementation Method 1
Strain may be induced in a silicon substrate by growing the silicon substrate on top of another crystalline substrate with a different lattice. For example, tensile strain may be induced by growing a silicon substrate on top of silicon-germanium (SiGe), which has a larger lattice than silicon and therefore applies tensile stress to the silicon lattice.
Implementation Method 2
Strain may be induced in a silicon substrate by growing the silicon substrate on top of another crystalline substrate with a different lattice.
Data Source
AI summary
Methods and devices for enhancing mobility of charge carriers. An integrated circuit may include semiconductor devices of two types. The first type of device may include a metallic gate and a channel strained in a first manner. The second type of device may include a metallic gate and a channel strained in a second manner. The gates may include, collectively, three or fewer metallic materials. The gates may share a same metallic material. A method of forming the semiconductor devices on an integrated circuit may include depositing first and second metallic layers in first and second regions of the integrated circuit corresponding to the first and second gates, respectively.