FinFET Work Function Gradient for Threshold Voltage Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The shrinking scale of semiconductor devices, particularly in finFETs, limits the space for work function metal layers, leading to voltage fluctuation and instability due to the lack of sufficient space for voltage regulation.
Innovation Solution
A work function metal layer with a gradient concentration is introduced, where the concentration of the work function material increases from a first value to a peak and then decreases, providing stability and minimizing threshold voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the device scale is shrunk to increase functional density, then productivity and production efficiency are improved, but the space for work function metal layer is reduced leading to voltage fluctuation
Solution Approach 1:
The patent applies local quality by creating a work function metal layer with non-uniform concentration distribution. The layer has a first concentration in a first region and a second concentration in a second region, where the concentrations differ. This gradient concentration profile allows different regions of the same layer to have different electrical properties, enabling voltage regulation and stability in scaled-down devices without requiring additional space for separate control layers.
2Length of moving object
If the work function metal layer thickness is reduced to fit smaller device dimensions, then device scaling is achieved, but threshold voltage control becomes difficult leading to fluctuations
Solution Approach 1:
The patent changes the concentration parameter of the work function metal layer to achieve better threshold voltage control. Instead of relying solely on thickness control, the invention varies the concentration of the work function metal from one region to another within the same layer. This parameter change allows for fine-tuned threshold voltage adjustment even in thin layers, maintaining manufacturing precision while enabling device scaling.
Data Source
AI summary
A semiconductor device includes a semiconductor substrate having a channel region. A gate dielectric layer is over the channel region of the semiconductor substrate. A work function metal layer is over the gate dielectric layer, wherein along a direction from a first boundary of the work function metal layer to a second boundary of the work function metal layer, a concentration of a work function material in the work function metal layer increases from a first value to a peak value and then decreases from the peak value to a second value, wherein the second value is greater than the first value. A gate electrode is over the work function metal layer.