Molybdenum Nitride Gate Electrodes for Work Function Control
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Solution Overview
Problem
Conventional n-type doped polysilicon gate electrodes in MOS technology face challenges such as gate depletion and non-ideal effective work function, especially in advanced node applications, leading to complex threshold voltage adjustment implantation processes.
Innovation Solution
The use of a molybdenum nitride film formed by atomic layer deposition (ALD) as a gate electrode material, which involves contacting a substrate with a molybdenum halide precursor, a nitrogen precursor, and a reducing precursor in sequential ALD cycles to achieve a gate electrode structure with an effective work function greater than approximately 5.0 eV.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doped polysilicon is used as gate electrode material, then conductivity is achieved, but gate depletion occurs creating extra gate insulator thickness
Solution Approach 1:
The patent changes the material parameter from doped polysilicon to metal nitride, fundamentally altering the electrical properties to eliminate gate depletion while maintaining conductivity. This material substitution resolves the contradiction by providing a gate electrode that does not deplete carriers, thus avoiding the extra gate insulator thickness effect.
Solution Approach 2:
The gate electrode structure uses a composite approach with metal nitride as the primary conductive material, potentially combined with other layers or materials to achieve both ideal conductivity and zero gate depletion, thereby simultaneously satisfying both requirements.
2Ease of manufacture
If doped polysilicon is used as gate electrode material, then manufacturing simplicity is maintained, but effective work function is non-ideal for both NMOS and PMOS devices
Solution Approach 1:
The patent changes the material composition from polysilicon to metal nitride, which inherently provides the desired effective work function range for both NMOS and PMOS devices. This material parameter change eliminates the need for complex threshold voltage adjustment implantation processes, thereby maintaining manufacturing simplicity while improving electrical performance.
3Reliability
If threshold voltage adjustment implantation is used to correct non-ideal effective work function, then work function compatibility is improved, but process complexity increases significantly
Solution Approach 1:
The patent extracts and removes the need for threshold voltage adjustment implantation processes by selecting metal nitride as the gate electrode material. This material inherently provides the correct effective work function, eliminating the requirement for additional complex implantation steps to achieve work function compatibility.
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 molybdenum nitride film provides a gate electrode structure with improved effective work function and reduced electrical resistivity, addressing the limitations of doped polysilicon and simplifying threshold voltage adjustment processes in advanced node applications.
Implementation Method 1
contacting the substrate with a first vapor phase reactant comprising a molybdenum halide precursor
Implementation Method 2
contacting the substrate with a second vapor phase reactant comprising a nitrogen precursor selected from the group comprising ammonia (NH3), hydrazine (N2H4), triazane (N3H5), tertbutylhydrazine (C4H9N2H3), methylhydrazine (CH3NHNH2), and dimethylhydrazine ((CH3)2N2H2)
Implementation Method 3
contacting the substrate with a third vapor phase reactant comprising a reducing precursor selected from the group comprising hydrogen gas (H2), silane (SiH4), disilane (Si2H6), trisilane (Si3H8), tetrasilane (Si4H8), and acetylene (C2H2)
Data Source
AI summary
Methods for forming a semiconductor device structure are provided. The methods may include forming a molybdenum nitride film on a substrate by atomic layer deposition by contacting the substrate with a first vapor phase reactant comprising a molybdenum halide precursor, contacting the substrate with a second vapor phase reactant comprise a nitrogen precursor, and contacting the substrate with a third vapor phase reactant comprising a reducing precursor. The methods provided may also include forming a gate electrode structure comprising the molybdenum nitride film, the gate electrode structure having an effective work function greater than approximately 5.0 eV. Semiconductor device structures including molybdenum nitride films are also provided.