Transition Metal Nitride Gate Electrodes for Work Function Tuning
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Solution Overview
Problem
Advanced node semiconductor applications face challenges with doped polysilicon gate electrodes due to non-ideal effective work function and gate depletion, which become complex and impractical as device geometries reduce, necessitating an alternative material like transition metal nitride with tunable properties.
Innovation Solution
Atomic layer deposition (ALD) methods using a transition metal precursor and an alkyl-hydrazine precursor to form transition metal nitride films, such as titanium nitride, with controlled crystallographic orientation and increased carbon and hydrogen content, enabling modulation of effective work function and film thickness for improved semiconductor device performance.
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 transition 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 problem.
Solution Approach 2:
The patent employs composite gate electrode structures combining transition metal nitride with other materials to achieve both ideal conductivity and work function characteristics. The composite structure allows tuning of electrical properties to simultaneously satisfy conductivity requirements and eliminate gate depletion effects.
2Ease of manufacture
If doped polysilicon gate material is used, then device fabrication is simplified, but non-ideal effective work function results for both NMOS and PMOS
Solution Approach 1:
The patent changes the work function parameter by substituting doped polysilicon with transition metal nitride, which provides inherently better work function characteristics for both NMOS and PMOS devices. This material change eliminates the need for complex threshold voltage adjustment implantation while maintaining fabrication simplicity.
3Reliability
If threshold voltage adjustment implantation is used to correct non-ideal work function, then work function compatibility improves, but device complexity increases as geometries reduce
Solution Approach 1:
The patent extracts the work function adjustment function from the fabrication process by using transition metal nitride material with inherent ideal work function characteristics. This eliminates the need for separate threshold voltage adjustment implantation steps, thereby reducing process complexity while maintaining work function compatibility.
4Manufacturing precision
If ALD process with known precursors is used to deposit transition metal nitride, then film formation is achieved, but electronic and crystallographic properties modification is limited
Solution Approach 1:
The patent changes the chemical parameters of the ALD process by introducing new precursor formulations and reaction conditions. These parameter changes enable precise control over the electronic and crystallographic properties of the deposited transition metal nitride films, achieving predominant (200) orientation and desired work function values.
Solution Approach 2:
The patent utilizes phase transition control during the ALD process to achieve specific crystallographic orientations. By controlling deposition temperature and precursor delivery parameters, the process promotes formation of the desired (200) oriented phase with optimal electronic properties for gate electrode applications.
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 ALD process forms transition metal nitride films with a predominant (200) crystallographic orientation and increased atomic percentages of carbon and hydrogen, resulting in enhanced effective work function and reduced thickness, addressing non-ideal work function issues in NMOS and PMOS devices, and enabling more practical threshold voltage adjustments.
Implementation Method 1
contacting the substrate with a first vapor phase reactant comprising a transition metal precursor and contacting the substrate with a second vapor phase reactant comprising an alkyl-hydrazine precursor
Implementation Method 2
Atomic layer deposition (ALD) methods using a transition metal precursor and an alkyl-hydrazine precursor to form transition metal nitride films
Data Source
AI summary
Methods for forming a transition metal nitride film on a substrate by atomic layer deposition and related semiconductor device structures are provided. In some embodiments, methods may include contacting a substrate with a first vapor phase reactant comprising a transition metal precursor and contacting the substrate with a second vapor phase reactant comprising an alkyl-hydrazine precursor. In some embodiments, related semiconductor device structures may include a PMOS transistor gate structure, the PMOS transistor gate structure including a transition metal nitride film and a gate dielectric between the transition nitride film and a semiconductor body. The transition metal nitride film includes a predominant (200) crystallographic orientation.