NMOS N-Metal Carbide Films for Low-Resistivity Work Function Control
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Solution Overview
Problem
The challenge of maintaining low resistivity and achieving NMOS band edge in transistor materials becomes difficult with conventional titanium aluminum carbide (TiAlC) N-metal schemes, leading to high resistivity and leakage issues as device sizes shrink, especially in advanced transistor technologies like FinFET and GAA devices.
Innovation Solution
The use of binary and ternary metal carbide films and metal silicide films as N-metal regions, which are deposited on a high-κ dielectric layer, providing low resistivity and improved device performance without the need for a high-k capping layer, and are formed using methods like ALD to prevent oxidation and diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional titanium aluminum carbide (TiAlC) N-metal schemes are used to increase the percentage of aluminum to boost work function, then the work function is improved, but the resistivity increases and device reliability deteriorates
Solution Approach 1:
The patent changes the material composition parameters by using binary metal carbides (TiC, TaC, HfC, ZrC) and metal silicides instead of conventional TiAlC ternary compounds. This parameter change allows achieving the desired work function (4.0-4.7 eV) without the resistivity penalties associated with high aluminum content, thereby resolving the contradiction between work function control and device reliability
Solution Approach 2:
The patent employs composite material strategies by combining metal carbide films with high-κ dielectric layers, and optionally with titanium nitride barrier layers. This composite structure achieves both low resistivity (through the metal carbide/silicide) and appropriate work function (through the combination with high-κ dielectric), while preventing the harmful effects of oxidation and diffusion that would otherwise compromise device reliability
2Productivity
If device dimensions are shrunk to increase functional density, then the number of devices per chip area is improved, but control of device structure dimensions becomes difficult and performance degradation occurs
Solution Approach 1:
The patent addresses dimension control challenges in scaled devices by precisely controlling the thickness of metal carbide films (5-20 nm) and high-κ dielectric layers (10-50 nm). These controlled thin-film parameters enable maintaining consistent work function and electrical characteristics even as device dimensions shrink, thereby supporting increased functional density without sacrificing manufacturing precision
Solution Approach 2:
The patent applies preliminary protective actions by depositing metal carbide films before high-κ dielectric layers, and optionally incorporating titanium nitride barrier layers, to prevent oxidation and diffusion that would otherwise be exacerbated by device scaling. This preliminary protection ensures dimension stability and performance consistency in scaled devices
3Reliability
If high Al content is used in N-metal to achieve desired work function, then the work function is improved, but leakage increases and scaling becomes more challenging
Solution Approach 1:
The patent fundamentally changes the material system from aluminum-based TiAlC compounds to binary metal carbides (TiC, TaC, HfC, ZrC) and metal silicides. This parameter change achieves the desired work function range (4.0-4.7 eV) through intrinsic material properties rather than high aluminum content, thereby eliminating the leakage problems associated with high-Al N-metals while maintaining precise work function tuning capability
Solution Approach 2:
The patent replaces the conventional TiAlC system with alternative metal carbide and silicide materials that provide comparable or superior electrical characteristics without the harmful side effects. These alternative materials serve as effective substitutes that achieve the same functional goals (work function control) without the leakage penalties of high-aluminum content
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 achieves low resistivity and improved reliability in NMOS transistors, enhancing device performance and reducing the risk of leakage, while maintaining the required band edge work function.
Implementation Method 1
formed using methods like ALD to prevent oxidation and diffusion
Data Source
AI summary
Provided are semiconductor devices, e.g., transistors, and methods of manufacturing semiconductor devices which achieve NMOS band edge with low resistivity and having improved device performance and reliability. Provided are materials that can be used as effective N-metal films for transistors. Instead of conventional titanium aluminum carbide (TiAlC) based N-metal films, provided are binary/ternary metal carbide films and metal silicide films that may be used as N-metal films with no/minimal high-k (HK) capping layer required.