Vanadium and Indium Gate Layers for CMOS Work Function Tuning
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Solution Overview
Problem
Conventional gate electrode materials in CMOS devices, such as doped polysilicon, face challenges with gate depletion and non-ideal effective work function, especially in advanced node applications, necessitating improved materials for threshold voltage adjustment and other applications like diffusion barriers and etch stop layers.
Innovation Solution
The use of vanadium and/or indium layers formed through cyclical deposition processes, including vanadium halides, oxyhalides, and indium precursors, with reactants like oxygen, nitrogen, and sulfur, to create layers suitable for gate electrodes, etch stop layers, and diffusion barriers, providing improved work function and threshold voltage adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If doped polysilicon is used as gate electrode material, then the device can be manufactured with conventional processes, but gate depletion occurs and effective work function is non-ideal
Solution Approach 1:
The patent uses a composite material structure consisting of a titanium nitride layer combined with a vanadium or indium layer. The titanium nitride provides a base work function, while the vanadium or indium layer adjusts the effective work function to ideal values for both NMOS and PMOS devices. This composite structure eliminates gate depletion issues while achieving the desired electrical characteristics without requiring threshold voltage adjustment implantation.
2Reliability
If titanium nitride layer is used to improve effective work function, then work function is improved, but higher work function values desired in PMOS regions cannot be achieved
Solution Approach 1:
The patent changes the material parameter by introducing vanadium or indium layers with specific electronic properties. These materials have different work functions and can be precisely controlled in thickness to adjust the effective work function. By varying the thickness and composition of the vanadium or indium layer, the effective work function can be tuned to achieve higher values for PMOS regions or lower values for NMOS regions, providing the necessary adaptability across different device types.
3Productivity
If device geometries are reduced in advanced node applications, then device density and speed improve, but threshold voltage adjustment implantation becomes increasingly complex and impractical
Solution Approach 1:
The patent replaces the mechanical/chemical process of threshold voltage adjustment implantation with a physical deposition process. Instead of using ion implantation to adjust threshold voltage, the invention uses atomic layer deposition or chemical vapor deposition to form vanadium or indium layers that inherently provide the desired threshold voltage adjustment through their work function properties. This substitution eliminates the complexity of implantation processes in scaled devices while maintaining the ability to control device electrical characteristics.
4Manufacturing precision
If vanadium or indium layers are deposited using cyclical deposition processes, then precise thickness control and uniformity are achieved, but multiple deposition steps are required
Solution Approach 1:
The patent employs periodic action through cyclical deposition processes such as atomic layer deposition. The deposition occurs in repeated cycles where precursors are alternately introduced, reacted, and purged. Each cycle deposits a controlled amount of material, and by repeating the cycle multiple times, the desired layer thickness is achieved with precise control. The periodic nature of the process ensures uniformity across the substrate while maintaining excellent thickness control through the self-limiting chemistry of each deposition cycle.
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 vanadium and indium layers offer enhanced performance by reducing gate depletion and achieving ideal effective work functions, facilitating precise thickness control and uniformity, suitable for advanced CMOS devices and other semiconductor applications.
Implementation Method 1
depositing a vanadium or indium layer onto a surface of the substrate. The cyclical deposition process can include (e.g., sequentially and separately) providing a vanadium and/or indium precursor to the reaction chamber and providing a reactant to the reaction chamber
Data Source
AI summary
Methods and systems for depositing vanadium and/or indium layers onto a surface of a substrate and structures and devices formed using the methods are disclosed. An exemplary method includes using a cyclical deposition process, depositing a vanadium and/or indium layer onto the surface of the substrate. The cyclical deposition process can include providing a vanadium and/or indium precursor to the reaction chamber and separately providing a reactant to the reaction chamber. The cyclical deposition process may desirably be a thermal cyclical deposition process. Exemplary structures can include field effect transistor structures, such as gate all around structures. The vanadium and/or indium layers can be used, for example, as barrier layers or liners, as work function layers, as dipole shifter layers, or the like.