Dual Work Function Gate Stack for Precise Nano-FET Threshold Tuning
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, challenges arise in accurately tuning the threshold voltages of nano-FETs due to modifications in work function tuning layers, leading to inconsistencies in device performance.
Innovation Solution
The implementation of multiple work function tuning layers with a barrier layer that inhibits modification of the underlying work function layer during treatment, allowing for precise tuning of threshold voltages by using a fluorination or oxidation process on the upper work function tuning layer while protecting the lower layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single work function tuning layer is used, then the device structure is simple, but the threshold voltage tuning precision is insufficient
Solution Approach 1:
The work function tuning layer is segmented into multiple distinct layers (first work function tuning layer and second work function tuning layer), each with different materials and functions. This segmentation allows independent optimization of each layer's properties, enabling precise threshold voltage tuning while maintaining manageable structural complexity.
Solution Approach 2:
A barrier layer is introduced as an intermediary between the first and second work function tuning layers. This barrier layer prevents unwanted diffusion and modification of the first work function tuning layer during the fluorination or oxidation treatment of the second layer, thereby protecting the underlying layer while allowing precise tuning of the upper layer.
2Manufacturing precision
If fluorination or oxidation process is applied to tune work function, then threshold voltage tuning is achieved, but the underlying work function layer is unintentionally modified
Solution Approach 1:
The barrier layer serves as a protective intermediary that selectively prevents the fluorination or oxidation process from reaching and modifying the first work function tuning layer. This allows the second layer to be treated for precise threshold voltage tuning while the first layer's composition remains stable and unchanged.
Solution Approach 2:
The barrier layer is placed in advance between the two work function tuning layers to preemptively prevent unwanted chemical reactions. By establishing this protective barrier before the fluorination or oxidation process, the underlying layer is protected from modification that would otherwise occur during the tuning process.
3Productivity
If feature size is reduced to increase integration density, then more components fit in given area, but threshold voltage tuning consistency deteriorates
Solution Approach 1:
The multi-layer work function tuning structure with separate barrier layer allows each layer to be independently optimized for miniaturization. As feature sizes are reduced, each layer can be scaled and tuned independently, maintaining consistent threshold voltage control even at smaller dimensions where single-layer structures would lose precision.
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 enables more accurate tuning of threshold voltages, improving the performance and consistency of nano-FETs by preventing unwanted modifications to the underlying work function layer, thus enhancing the manufacturing process for advanced semiconductor nodes.
Implementation Method 1
a barrier layer on the first work function tuning layer. The barrier layer prevents modification of the first work function tuning layer during treatment of the second work function tuning layer
Implementation Method 2
using a fluorination or oxidation process on the upper work function tuning layer
Implementation Method 3
using a fluorination or oxidation process on the upper work function tuning layer
Data Source
AI summary
In an embodiment, a device includes: a channel region; a gate dielectric layer on the channel region; a first work function tuning layer on the gate dielectric layer, the first work function tuning layer including a n-type work function metal; a barrier layer on the first work function tuning layer; a second work function tuning layer on the barrier layer, the second work function tuning layer including a p-type work function metal, the p-type work function metal different from the n-type work function metal; and a fill layer on the second work function tuning layer.