Nanosheet Threshold Voltage Uniformity via Local Work Function Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices face challenges in achieving uniform threshold voltage as they scale to smaller dimensions, particularly in nanosheet devices, where variations in threshold voltage between inner and outer sheets lead to performance inconsistencies.
Innovation Solution
A method involving the formation of a conductive barrier surrounding a nanosheet, with a first and second work function conducting layer, where the second work function metal is used to compensate for threshold voltage offset between regions, ensuring uniform threshold voltage across the nanosheet structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If nanosheet devices are scaled to smaller dimensions to increase device density, then area efficiency and drive current are improved, but threshold voltage uniformity deteriorates due to variations between inner and outer sheets
Solution Approach 1:
The patent applies local quality by forming a second work function conducting layer selectively over the second region (outer sheets) of the conducting layer. This creates different work function characteristics in different regions: the first region (inner sheets) retains the first work function conducting layer, while the second region (outer sheets) has the second work function conducting layer. This local differentiation compensates for threshold voltage offsets between inner and outer nanosheets, achieving uniform threshold voltage across the device while maintaining the high-density stacked nanosheet structure.
2Manufacturing precision
If work function conducting layers are formed to adjust threshold voltage, then threshold voltage uniformity is improved, but device complexity increases due to additional layers and regions
Solution Approach 1:
The patent segments the conducting layer into two distinct regions: a first region overlying inner nanosheets and a second region overlying outer nanosheets. This segmentation allows independent work function adjustment for different nanosheet groups. The conducting layer is divided such that the first work function conducting layer is formed over the first region and the second work function conducting layer is formed over the second region, enabling targeted threshold voltage compensation without requiring complete restructuring of the device.
Solution Approach 2:
The patent implements local quality by applying different work function conducting layers to different regions of the device. The second work function conducting layer is specifically formed over the second region (outer sheets) to compensate for threshold voltage offsets, while the first region (inner sheets) maintains its original work function conducting layer. This localized approach achieves threshold voltage uniformity without unnecessarily complicating the entire device structure.
Data Source
AI summary
A method is presented for forming a nanosheet structure having a uniform threshold voltage (Vt). The method includes forming a conductive barrier surrounding a nanosheet, forming a first work function conducting layer over the conductive barrier layer, and forming a conducting layer adjacent the first work function conducting layer, the conducting layer defining a first region and a second region. The method further includes forming a second work function conducting layer over the second region of the conducting layer to compensate for threshold voltage offset between the first and second regions of the conducting layer.