GAA Semiconductor Structure With Aligned Nanowires and Gate Control
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Solution Overview
Problem
The challenge in fabricating horizontal gate-all-around (GAA) transistors is the unsatisfactory nanowire formation using current methods, particularly with a single epitaxial process, which affects the scaling down of transistors and leads to short-channel effects like Drain-Induced Barrier Lowering and degradation of sub-threshold slope, compromising gate control and transistor performance.
Innovation Solution
A method for forming GAA transistors involves creating nanowires with aligned profiles and gate stacks using a combination of photolithography and etching processes, including the formation of semiconductor layers and fin elements, with controlled etching and epitaxial growth to achieve precise nanowire alignment and gate stack formation, reducing loading effects and improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gate length is scaled down to increase drive current, then transistor performance is improved, but short-channel effects worsen
Solution Approach 1:
The patent transitions from planar 2D gate control to three-dimensional gate-all-around structures that wrap around nanowire channels. This dimensional change provides superior gate control from all directions (top, bottom, and sidewalls) while maintaining scaled-down gate lengths, effectively suppressing short-channel effects like DIBL and sub-threshold slope degradation.
Solution Approach 2:
The gate structure is nested around the nanowire channel in a gate-all-around configuration, with the gate completely surrounding the channel region. This nested arrangement maximizes gate control over the channel while allowing aggressive scaling of gate length without compromising reliability.
2Ease of manufacture
If single epitaxial process is used for nanowire formation, then process simplicity is maintained, but nanowire formation quality deteriorates
Solution Approach 1:
The nanowire formation process is segmented into multiple distinct epitaxial growth stages rather than attempting single-step formation. Each stage targets specific nanowire characteristics (nucleation, vertical growth, diameter control), allowing precise control of nanowire morphology while maintaining epitaxial process advantages.
Solution Approach 2:
The patent performs preliminary nanowire nucleation and initial growth stages before final nanowire completion and device fabrication. This preliminary action establishes controlled nanowire foundations with proper orientation and diameter, enabling subsequent precise gate formation and device assembly.
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 enhances the alignment of nanowires and reduces loading effects during gate stack formation, thereby improving transistor performance by maintaining effective gate control and mitigating short-channel effects, allowing for more aggressive scaling while maintaining device reliability.
Implementation Method 1
fabrication of the HGAA transistors can be challenging. For example, nanowire formation of HGAA transistors by the current methods is not satisfactory in all respects, especially when using a single process, such as a single epitaxial process
Data Source
AI summary
A semiconductor device is provided. The semiconductor device includes a substrate and a semiconductor layer formed over the substrate. The semiconductor device further includes a first channel layer and a second channel layer and a first insulating structure interposing the first channel layer and the semiconductor layer and a second insulating structure interposing the first channel layer and the second channel layer. The semiconductor device further includes a gate stack abutting the first channel layer and the second channel layer, and the gate stack includes a first portion vertically sandwiched between the first channel layer and the semiconductor layer and a second portion vertically sandwiched between the first channel layer and the second channel layer.