Forksheet GAA Transistor Structure for Nanosheet Gate Control
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Solution Overview
Problem
As semiconductor devices shrink, there is a need for improved processing and manufacturing techniques to enhance device density and performance, particularly in transistors with nanosheet channels, where existing methods struggle to achieve effective gate control and scalability.
Innovation Solution
The development of gate all-around (GAA) transistors with a fork-like gate structure, where nanosheet channels are surrounded by a gate electrode on at least three surfaces, and a high-k dielectric layer is laterally recessed to allow greater extension of the gate electrode, enabling better control over the channels and increased device density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional transistor structures are used, then manufacturing processes are simpler, but device density and gate control are insufficient
Solution Approach 1:
The patent transitions from planar gate control to three-dimensional gate-all-around control by wrapping the gate electrode around the nanosheet channel on all sides. This dimensional change enables superior electrostatic control and threshold voltage modulation while maintaining compatibility with existing fabrication processes through sequential gate formation steps.
Solution Approach 2:
The gate electrode is nested around the nanosheet channel in a concentric arrangement, with the gate completely surrounding the channel structure. This nested configuration provides maximum gate control over the channel while allowing the structure to be formed through layered deposition and patterning processes.
2Productivity
If device size is reduced to increase density, then more devices fit per chip area, but processing and manufacturing become more difficult
Solution Approach 1:
The transistor structure is segmented into distinct functional layers including the nanosheet channel, high-k dielectric, and gate electrode, each formed through separate fabrication steps. This segmentation allows independent optimization of each component while maintaining overall device density through vertical stacking rather than lateral expansion.
Solution Approach 2:
The patent employs high-k dielectric materials with superior electrical properties compared to conventional low-k materials. This parameter change in dielectric constant enables effective gate control at reduced device dimensions, allowing increased device density without sacrificing manufacturing feasibility through established material deposition techniques.
3Manufacturing precision
If nanosheet channels are used, then device density and carrier mobility improve, but gate control becomes more challenging
Solution Approach 1:
The transistor employs a composite structure combining nanosheet semiconductor channels with high-k dielectric gate insulation. This composite material approach leverages the high carrier mobility of nanosheets while the high-k dielectric provides enhanced electric field control, together achieving superior gate control that neither material could provide alone.
Solution Approach 2:
The gate electrode completely surrounds the nanosheet channel in three dimensions, transitioning from two-dimensional planar control to three-dimensional wraparound control. This dimensional enhancement provides superior electrostatic control over the nanosheet channel, effectively managing the challenges of controlling current in ultra-thin channel structures.
Data Source
AI summary
A semiconductor device structure, along with methods of forming such, are described. The structure includes a dielectric feature comprising a first dielectric layer and a second dielectric layer, the first dielectric layer has a first sidewall and a second sidewall opposing the first sidewall, and the second dielectric layer is in contact with at least a portion of the first sidewall and at least a portion of the second sidewall. The structure also includes a first semiconductor layer adjacent the first sidewall, wherein the first semiconductor layer is in contact with the second dielectric layer. The structure further includes a first gate electrode layer surrounding at least three surfaces of the first semiconductor layer, wherein the first gate electrode layer has a surface facing the second dielectric layer, and the surface extends over a plane defined by an interface between the second dielectric layer and the first semiconductor layer.