Multi-Body Thickness Transistor Fin Segmentation
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Solution Overview
Problem
Tri-gate transistors with thinner fins exhibit improved short-channel effects but suffer from increased external resistance, leading to reduced drive current, which complicates the balance between conductivity and leakage current.
Innovation Solution
A multi-body-thickness field-effect transistor (MBT-FET) design is introduced, featuring a wide top section and narrow sections, where a high dielectric constant dielectric layer and gate electrode are deposited on all sides of the fin, effectively combining the advantages of wide and narrow fin devices to enhance gate control and reduce external resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fin thickness is reduced to improve short-channel effects, then the sub-threshold gradient steepens and drain induced barrier lowering is reduced, but the external resistance increases and drive current decreases
Solution Approach 1:
The transistor structure is segmented into multiple regions with different fin thicknesses: a first region with a first fin thickness and a second region with a second fin thickness. This segmentation allows different portions of the transistor to optimize for different functions - one region for short-channel effect control and another for drive current
Solution Approach 2:
Different regions of the transistor are given different local properties through varying fin thickness. The first region has a first fin thickness optimized for one performance characteristic while the second region has a second fin thickness optimized for another characteristic, allowing simultaneous optimization of conflicting parameters
2Object-generated harmful factors
If the fin thickness is reduced to achieve full depletion and steeper sub-threshold gradients, then off-state leakage current is reduced, but the external resistance increases significantly
Solution Approach 1:
The transistor is divided into segments with different fin thicknesses to separately address leakage control and resistance reduction. One segment uses thin fin for low leakage while another segment uses thick fin for low resistance
Solution Approach 2:
Different regions have different fin thickness properties tailored to their specific functional requirements - thin fin regions for leakage control and thick fin regions for resistance management
Data Source
AI summary
A multi-body thickness (MBT) field effect transistor (FET) comprises a silicon body formed on a substrate. The silicon body may comprise a wide section and a narrow section between the wide section and the substrate. The silicon body may comprise more than one pair of a wide section and a narrow section, each pair being located at a different height of the silicon body. The silicon body is surrounded by a gate material on three sides. The substrate may be a bulk silicon substrate or a silicon-on-insulator (SOI) substrate. The MBT-FET combines the advantages of a wide fin device and a narrow fin device.