MOSFET Work Function Modification via Gate Electrode Materials
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Solution Overview
Problem
Current semiconductor technologies face challenges in providing multiple threshold voltage offerings without degrading mobility or increasing threshold voltage variability, as traditional approaches rely on channel doping which is undesirable.
Innovation Solution
The use of a work function modifying material in combination with the gate electrode to achieve a work function different from the gate electrode alone, allowing for a wide range of threshold voltages by interdigitation of nFET and pFET gate work functions, enabling sharing of materials across both types of transistors without exclusive use of a single work function material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If channel doping is used to provide multiple threshold voltage offerings, then threshold voltage control is improved, but mobility degradation and threshold voltage variability increase
Solution Approach 1:
The patent changes the physical-chemical parameters of the gate electrode by depositing different work function materials (titanium nitride, tungsten, cobalt, platinum, ruthenium, palladium, nickel, aluminum) and adjusting their thicknesses to achieve multiple threshold voltage offerings without channel doping. This parameter change approach resolves the contradiction by providing threshold voltage control through gate electrode composition variation rather than channel doping.
Solution Approach 2:
The patent uses composite gate electrode structures combining multiple materials with different work functions (e.g., titanium nitride combined with tungsten, cobalt, platinum, ruthenium, palladium, nickel, or aluminum). These composite structures enable fine-tuned work function adjustment and multiple threshold voltage offerings while maintaining channel undoped, thereby avoiding mobility degradation and threshold voltage variability associated with traditional doping approaches.
2Reliability
If traditional work function materials are used exclusively for nFET or pFET, then transistor type optimization is improved, but material versatility and circuit design flexibility are reduced
Solution Approach 1:
The patent makes gate electrode materials universal by using the same set of work function materials (titanium nitride, tungsten, cobalt, platinum, ruthenium, palladium, nickel, aluminum) for both nFET and pFET devices. By adjusting material thickness combinations rather than using exclusive materials for each transistor type, the patent achieves both transistor type optimization and enhanced material versatility, allowing flexible circuit design with unified material processing.
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 method allows for multiple threshold voltage offerings without the need for channel doping, reducing mobility degradation and threshold voltage variability, thereby enhancing circuit design flexibility and granularity.
Implementation Method 1
depositing a work function modifying material on the gate dielectric disposed on the first channel region and the second channel region
Data Source
AI summary
A method of making a semiconductor device comprises forming a first channel region comprising a first channel region material and a second channel region comprising a second channel region material; disposing a gate dielectric on the first channel region and second channel region; depositing a work function modifying material on the gate dielectric; disposing a mask over the work function modifying material deposited on the gate dielectric disposed on the first channel region; removing the work function modifying material from the unmasked gate dielectric disposed on the second channel region; removing the mask from the work function modifying material deposited on the gate dielectric disposed on the first channel region; forming a first gate electrode on the work function modifying material deposited on the first channel region and forming a second gate electrode on the gate dielectric disposed on the second channel region.