Metal Carbide Gate Structures for MOSFET Work Function Tuning
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Solution Overview
Problem
As MOSFET devices are scaled down, replacing polysilicon with metal as a gate electrode material makes it difficult to tune the work function difference between the gate and channel, leading to challenges in modifying the threshold voltage, and traditional work-function layers are less conductive, resulting in performance losses.
Innovation Solution
The method involves forming metal carbide materials using multiple processes with different precursors to deposit discrete or mixed metal carbide layers, allowing for adjustment of the composition and properties of the metal carbide material to tune electrical properties such as work function and resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal replaces polysilicon as gate electrode material, then device performance is improved, but work function tuning becomes difficult
Solution Approach 1:
The gate electrode is segmented into multiple layers: a metal layer for high performance and a separate metal carbide work function layer for tuning capabilities. This segmentation allows each layer to fulfill its specific function independently, resolving the contradiction between performance and tunability.
Solution Approach 2:
The gate electrode uses a composite structure combining metal and metal carbide materials. The metal provides high conductivity and performance, while the metal carbide layer provides work function tuning capability, achieving both improved performance and retained adaptability.
2Adaptability or versatility
If traditional work-function layers are added to tune work function, then work function adjustment is achieved, but conductivity is reduced
Solution Approach 1:
The work function layer's conductivity is optimized by controlling its composition parameters (metal identity, carbide stoichiometry) and physical parameters (thickness). By adjusting these parameters, the layer achieves sufficient conductivity while maintaining work function tuning capability.
Solution Approach 2:
The work function layer uses composite metal carbide materials that combine metallic character (for conductivity) with carbide character (for work function control). This composite approach allows simultaneous achievement of both conductivity and work function adjustment.
3Manufacturing precision
If multiple deposition processes are used to form metal carbide layers, then composition control is improved, but manufacturing complexity increases
Solution Approach 1:
Multiple deposition processes (PVD, CVD, ALD) are merged into an integrated fabrication sequence, where each process deposits specific layers or compositions. This combining approach achieves precise composition control while managing overall manufacturing complexity through process integration.
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 manipulation of resistivity and work function of metal carbide structures, achieving desired performance by adjusting the composition and thickness of metal carbide layers, which is not achievable with typical metal carbide materials.
Implementation Method 1
The two or more processes can use, for example, at least one different precursor, to adjust the composition or properties of the metal carbide layer
Implementation Method 2
depositing a first metal carbide layer using a first precursor and a second precursor; and depositing a second metal carbide layer using a third precursor and a fourth precursor
Data Source
AI summary
Methods of forming thin-film structures including metal carbide material, and structures and devices including the metal carbide material are disclosed. Exemplary structures include metal carbide material formed using two or more different processes (e.g., two or more different precursors), which enables tuning of various metal carbide material properties, including resistivity, current leakage, and work function.