GAA Nanosheet Nitride Isolation for Gate-to-Substrate Leakage
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Solution Overview
Problem
In semiconductor devices, particularly Gate-All-Around (GAA) FETs, there is a challenge in preventing unintended electrical connections between the gate structure and the silicon substrate due to over-etching of Shallow Trench Isolation (STI) regions, leading to capacitive interference and leakage currents, which degrades device performance.
Innovation Solution
The implementation of a cap or sidewall spacer, made from dielectric materials like nitride-based compounds, is used to isolate the gate structure from the silicon layer, preventing electrical contact and reducing capacitive interference by limiting the gate metal's contact with the silicon substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Shallow Trench Isolation (STI) regions are etched to improve device isolation, then electrical isolation between adjacent devices is improved, but over-etching causes the gate structure to contact the silicon substrate, creating unintended electrical connections and capacitive interference
Solution Approach 1:
A nitride-based dielectric liner is deposited as an intermediary layer between the gate structure and the silicon substrate. This liner acts as a mediator that prevents direct electrical contact while allowing the STI etching process to proceed effectively for device isolation.
Solution Approach 2:
The nitride-based dielectric liner is deposited in advance before the STI etching process. This preliminary action ensures that the protective barrier is already in place to prevent over-etching from causing gate-to-substrate contact, while still allowing proper device isolation to be achieved.
2Object-affected harmful factors
If the gate structure is isolated from the silicon substrate using a cap or sidewall spacer, then capacitive interference is reduced, but device complexity increases due to additional structures
Solution Approach 1:
The nitride-based dielectric liner serves multiple functions simultaneously: it provides electrical isolation to reduce capacitive interference, acts as a protective barrier during etching processes, and can serve as a foundation for subsequent device structures. This multi-functionality reduces the need for separate isolation structures.
Solution Approach 2:
The nitride-based dielectric liner is self-forming through deposition processes and automatically provides the necessary isolation function without requiring additional complex isolation structures. The liner serves itself as both the isolation mechanism and the protective barrier.
Data Source
AI summary
One or more embodiments includes a semiconductor device. The semiconductor device includes: a first Gate-All-Around (GAA) field-effect transistor (FET) disposed on a silicon layer; and a second GAA FET disposed on the silicon layer adjacent to the first GAA FET. The semiconductor device also includes: an isolation layer disposed within the silicon layer between a first bottom dielectric isolation (BDI) layer of the first GAA FET and a second BDI layer of the second GAA FET; and a gate structure disposed proximate the first GAA FET and the second GAA FET, wherein at least one of a cap or a sidewall spacer isolates the gate structure from the silicon layer.