U-Shaped Thin Film Transistors for Enhanced Gate Control
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Solution Overview
Problem
Conventional thin film transistors face challenges in scaling down to smaller dimensions due to limitations in subthreshold swing and variability in fabrication processes, making it difficult to extend their performance into the 10 nm or sub-10 nm range, necessitating new methodologies or technologies for future technology nodes.
Innovation Solution
The implementation of non-planar thin film transistors with U-shaped features and increased channel length or width, which enhance gate control and performance by using semiconducting oxide materials and advanced architectures such as U-gate devices and vertical transistors, allowing for better channel control and reduced leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional thin film transistors are scaled down to smaller dimensions, then increased device density is achieved, but subthreshold swing performance deteriorates and variability increases
Solution Approach 1:
The patent transitions from planar 2D transistor structures to three-dimensional U-shaped and vertical transistor architectures. This dimensional change allows the channel to extend vertically and wrap around the gate, effectively increasing the channel length and gate control without increasing the lateral footprint, thereby achieving higher device density while maintaining or improving subthreshold swing performance through enhanced gate electrostatic control
Solution Approach 2:
The transistor channel is segmented into multiple sections wrapped around the gate structure, creating a U-shaped or vertical configuration. This segmentation allows each section to be independently controlled by the gate, improving the overall gate control and reducing variability in the channel properties, which directly addresses the subthreshold swing performance issue while enabling higher density
2Reliability
If multi-gate transistor structures are implemented, then gate control is improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent merges the channel sections into a unified U-shaped or vertical structure that wraps around a single gate electrode. This combining approach achieves multi-gate control functionality without requiring multiple separate gates, thereby improving gate control while avoiding the complexity of coordinating multiple independent gate structures. The single continuous gate provides uniform electrostatic control over all channel sections
Solution Approach 2:
Instead of adding multiple lateral gates in the planar direction, the patent uses vertical stacking and wrapping to achieve multi-gate control. The channel extends in the vertical dimension and wraps around the gate, providing control from multiple directions (top, bottom, and sidewalls) using a single gate structure, thus improving gate control without proportionally increasing device complexity
3Productivity
If feature dimensions are reduced to extend into 10 nm or sub-10 nm range, then increased device capacity is achieved, but fabrication process variability becomes unmanageable
Solution Approach 1:
The patent changes the geometric parameters of the transistor structure from planar to three-dimensional U-shaped and vertical configurations. This parameter change in structure geometry allows the device to achieve higher capacity through increased effective channel length and width without requiring proportional reduction in all dimensions, thereby maintaining manufacturability and reducing fabrication variability while still enabling scaling to advanced technology nodes
Data Source
AI summary
Thin film transistors having U-shaped features are described. In an example, integrated circuit structure including a gate electrode above a substrate, the gate electrode having a trench therein. A channel material layer is over the gate electrode and in the trench, the channel material layer conformal with the trench. A first source or drain contact is coupled to the channel material layer at a first end of the channel material layer outside of the trench. A second source or drain contact is coupled to the channel material layer at a second end of the channel material layer outside of the trench.