IC Isolation Regions Using Si/SiGe Layers to Suppress Parasitic Channels
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Solution Overview
Problem
Gate-all-around (GAA) transistors face parasitic channel issues leading to elevated source-to-drain leakage due to the wide 'sub-fin' region, which is difficult to control, especially compared to fin-based transistors, and existing solutions require expensive silicon-on-insulator (SOI) substrates or increase manufacturing complexity.
Innovation Solution
The introduction of novel integrated circuit (IC) structures with insulating material regions between source/drain and channel regions, formed without using SOI substrates, to mitigate parasitic channel formation, utilizing alternating layers of silicon and silicon-germanium materials to create effective isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fin-based transistor structures are used, then parasitic channel control is easier, but device scaling and performance are limited
Solution Approach 1:
The patent transitions from two-dimensional fin-based transistor structures to three-dimensional gate-all-around structures that completely surround the channel. This dimensional change enables better electrostatic control of the channel region, effectively suppressing parasitic channels while allowing continued device scaling. The gate wraps around the channel in all directions, providing superior control compared to conventional planar or fin structures.
2Reliability
If gate-all-around transistor structures are used to improve performance and reduce leakage, then transistor performance is enhanced, but parasitic channel formation increases due to wide sub-fin regions
Solution Approach 1:
The patent extracts or removes the problematic wide sub-fin regions from the gate-all-around structure. By eliminating these excessive lateral extensions of the channel region, the formation of parasitic channels is prevented while maintaining the beneficial three-dimensional gate control. The channel is confined to the necessary dimensions without unnecessary lateral expansion that would create parasitic conduction paths.
Solution Approach 2:
The patent applies different dimensional characteristics to different regions of the transistor. The channel region maintains appropriate lateral dimensions for good electrostatic control, while the gate structure provides three-dimensional wrapping. This local optimization ensures that each region has the precise geometry needed for its function, preventing parasitic channels while maintaining high performance.
3Reliability
If silicon-on-insulator substrates are used to reduce parasitic channel formation, then parasitic channel control improves, but manufacturing cost increases
Solution Approach 1:
The patent makes the transistor structure itself provide the isolation function that would otherwise require expensive silicon-on-insulator substrates. Through careful geometric design of the gate-all-around structure and channel region, the device achieves inherent parasitic channel suppression through its own three-dimensional architecture, eliminating the need for costly specialized substrates.
Solution Approach 2:
The patent changes the geometric parameters of the transistor structure, specifically transitioning to three-dimensional gate wrapping with controlled channel dimensions. This parameter change in the device architecture replaces the need for parameter changes in the substrate material (i.e., using SOI), achieving the same parasitic channel control through structural geometry rather than material selection.
4Reliability
If isolation structures are added to mitigate parasitic channel formation, then parasitic channel control improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the channel isolation function with the gate structure itself. The three-dimensional gate-all-around configuration inherently provides the isolation needed to prevent parasitic channels, eliminating the need for separate isolation structures. The gate structure serves dual purposes: controlling the channel and providing lateral isolation, thereby reducing overall manufacturing complexity.
Data Source
AI summary
Disclosed herein are isolation regions in integrated circuit (IC) structures, as well as related methods and components. For example, in some embodiments, an IC component may include: a first region including silicon; a second region including alternating layers of a second material and a third material, wherein the second material includes silicon and germanium, the third material includes silicon, and individual ones of the layers in the second region has a thickness that is less than 3 nanometers; and a third region including alternating layers of the second material and the third material, wherein individual ones of the layers in the third region has a thickness that is greater than 3 nanometers, and the second region is between the first region and the third region.