Vanadium Nitride Gate Electrode Deposition for High Work Function CMOS
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Solution Overview
Problem
Conventional gate electrode materials in CMOS devices, such as doped polysilicon, face challenges with carrier depletion and non-ideal effective work function, particularly in advanced node applications, necessitating the need for alternative materials with higher work function values.
Innovation Solution
A method of forming a vanadium nitride layer using a thermal cyclical deposition process, involving vanadium halide precursors and nitrogen reactants, which does not utilize plasma-activated species, to create a gate electrode structure with high work function values suitable for CMOS and other applications.
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 the gate electrode exhibits carrier depletion and non-ideal effective work function in advanced node applications
Solution Approach 1:
The patent changes the material parameter from doped polysilicon to vanadium nitride, which has inherently higher work function values (4.5-5.5 eV) compared to doped polysilicon. This material substitution eliminates carrier depletion issues while providing ideal effective work function for both NMOS and PMOS devices without requiring threshold voltage adjustment implantation processes.
Solution Approach 2:
The patent employs vanadium nitride as a composite material that combines the benefits of high work function (similar to titanium nitride or platinum) with improved manufacturability through thermal cyclical deposition processes, creating a gate electrode material that satisfies both electrical performance and fabrication requirements.
2Reliability
If titanium nitride layer is used to improve effective work function, then the work function becomes more ideal for CMOS applications, but the work function value may be too low for PMOS regions requiring higher work function values
Solution Approach 1:
The patent utilizes vanadium nitride which provides a broader and higher work function range (4.5-5.5 eV) compared to titanium nitride. This allows optimization for both NMOS and PMOS devices within the same material system, eliminating the need for different gate electrode materials or additional threshold voltage adjustment processes.
3Productivity
If plasma-activated species are used in deposition process, then the deposition rate may be improved, but the process complexity and potential damage to device structures increases
Solution Approach 1:
The patent replaces plasma-activated deposition with thermal cyclical deposition processes. This substitution eliminates the need for plasma generation equipment and associated process complexity while maintaining controlled deposition of vanadium nitride layers through sequential exposure to vanadium halide precursors and nitrogen reactants.
Solution Approach 2:
The thermal cyclical deposition process uses self-limiting surface reactions where vanadium halide precursors and nitrogen reactants automatically form monolayers on the substrate surface without requiring external plasma activation. The process inherently controls deposition rate and film quality through temperature and reactant exposure time parameters.
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 nitride layer exhibits high work function values, improving device performance by reducing carrier depletion and providing an ideal effective work function, making it suitable for advanced node applications and other electrode/capacitor uses.
Implementation Method 1
depositing a layer comprising vanadium nitride onto a surface of the substrate using a cyclical deposition process. The cyclical deposition process can include providing a vanadium halide precursor to the reaction chamber and providing a nitrogen reactant to the reaction chamber
Implementation Method 2
exemplary vanadium nitride layers can be formed using a thermal cyclical deposition process—without using a plasma or plasma-activated species
Data Source
AI summary
Methods and systems for depositing vanadium nitride layers onto a surface of the substrate and structures and devices formed using the methods are disclosed. An exemplary method includes using a cyclical deposition process, depositing a vanadium nitride layer onto a surface of the substrate. The cyclical deposition process can include providing a vanadium halide precursor to the reaction chamber and separately providing a nitrogen reactant to the reaction chamber. The cyclical deposition process may desirably be a thermal cyclical deposition process.