Nano-FET Gate Electrode Work Function Tuning for Threshold Voltage
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, challenges arise in maintaining performance and efficiency, particularly in the integration and manufacturing of nano-FETs, where achieving optimal threshold voltages and device performance is hindered by the limitations of current gate electrode materials and processes.
Innovation Solution
The formation of gate electrodes with work function tuning layers, specifically using materials like Zr, Hf, Nb, or Ta, which lower the work function value and shift the effective work function to improve n-type device performance, combined with a method that includes forming and patterning these layers to enhance the threshold voltages of nano-FETs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional gate electrode materials are used in nano-FETs, then manufacturing is simpler, but threshold voltage control and device performance deteriorate
Solution Approach 1:
The gate electrode is segmented into multiple functional layers: a base gate electrode layer and an additional work function tuning layer. This segmentation allows independent optimization of each layer's function - the base layer provides structural foundation while the tuning layer specifically controls work function and threshold voltage, thereby improving threshold voltage control without overwhelming complexity
Solution Approach 2:
The gate electrode structure uses composite materials by combining conventional gate electrode materials with work function tuning materials. This composite approach enables the structure to simultaneously possess the structural properties of the base material and the electrical work function properties of the tuning material, achieving improved threshold voltage control while maintaining manufacturing feasibility
2Productivity
If feature size is reduced to increase integration density, then more components fit in given area, but maintaining performance and threshold voltage becomes more difficult
Solution Approach 1:
The work function tuning layer is applied locally and selectively to the gate electrode structure, providing localized work function adjustment exactly where needed in the miniaturized device. This local quality approach ensures that threshold voltage control is maintained at the nanoscale without requiring proportional scaling of the entire manufacturing complexity
Solution Approach 2:
The invention changes the work function parameter of the gate electrode by adding a tuning layer with specific material properties. This parameter change enables precise threshold voltage control in scaled-down devices, allowing integration density to increase while maintaining the electrical performance characteristics needed for proper device operation
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 approach improves the threshold voltages of n-type devices by effectively tuning the work function, leading to enhanced performance and integration capabilities in nano-FETs, applicable to various transistor types including nano-FETs, FinFETs, and planar FETs.
Implementation Method 1
The formation of gate electrodes with work function tuning layers, specifically using materials like Zr, Hf, Nb, or Ta, which lower the work function value and shift the effective work function to improve n-type device performance
Data Source
AI summary
An embodiment includes a device having nanostructures on a substrate, the nanostructures including a channel region. The device also includes a gate dielectric layer wrapping around each of the nanostructures. The device also includes a first work function tuning layer on the gate dielectric layer, the first work function tuning layer including a first n-type work function metal, aluminum, and carbon, the first n-type work function metal having a work function value less than titanium. The device also includes a glue layer on the first work function tuning layer. The device also includes and a fill layer on the glue layer.