Fin Structure With Recessed Substrate For Leakage Reduction
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Solution Overview
Problem
Conventional FinFET fabrication techniques result in fin structures being lower than surrounding shallow trench isolation due to over-etching, affecting the formation of epitaxial layers and leading to leakage current issues.
Innovation Solution
A semiconductor structure with a recessed substrate and insulating layer configuration, where the fin structure has terminal parts directly contacting the substrate and a central part suspended above the recess, enhancing the isolation ability of the insulating layer by preventing direct contact between the central part and the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional FinFET fabrication techniques are used to form recesses after removing part of fin structures, then the epitaxial layer growth space is accommodated, but the fin structures become lower than the surrounding shallow trench isolation due to over-etching, affecting subsequent epitaxial layer formation
Solution Approach 1:
The patent performs the etching action in advance to create the recess structure before forming the fin structures. By pre-defining the recess geometry and depth, the subsequent fin formation process can precisely control fin height without risking over-etching. The recess serves as a pre-prepared cavity that accommodates the epitaxial layer while providing reference planes for accurate fin structure formation.
Solution Approach 2:
The patent divides the fin structure into two distinct parts: terminal parts that contact the substrate and a central part that is suspended above the recess. This segmentation allows different portions of the fin structure to serve different functions - the terminal parts provide mechanical support and electrical contact, while the central suspended part enables epitaxial layer growth without interference from the substrate. This segmentation resolves the contradiction by allowing the central part to be positioned precisely above the recess without requiring the entire fin structure to be lowered.
2Volume of moving object
If the fin structure is lowered to accommodate epitaxial layer growth, then space for epitaxial growth is created, but the isolation ability of the shallow trench isolation deteriorates, leading to leakage current
Solution Approach 1:
The patent segments the fin structure into terminal parts contacting the substrate and a central suspended part. This segmentation enables the central part to be positioned above the recess without lowering the terminal parts, thereby maintaining the shallow trench isolation's isolation ability at the substrate level while creating the necessary space for epitaxial layer growth beneath the suspended central fin region.
Solution Approach 2:
The patent utilizes the vertical dimension by creating a recess into the substrate and positioning the central fin part above this recess. This three-dimensional configuration allows the epitaxial layer to grow in the vertical space above the recess without compromising the horizontal isolation provided by the shallow trench isolation at the substrate surface, thus resolving the contradiction between creating growth space and maintaining isolation ability.
3Strength
If the central part of the fin structure directly contacts the substrate, then structural support is provided, but leakage current occurs due to insufficient isolation
Solution Approach 1:
The patent divides the fin structure into terminal parts that contact the substrate for structural support and a central suspended part that does not contact the substrate. This segmentation ensures that the structural support function is fulfilled by the terminal parts while the central suspended part is isolated from the substrate, preventing leakage current paths between adjacent devices. The insulating layer fills the recess to provide electrical isolation for the suspended central region.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary between the central suspended fin part and the substrate. This insulating layer, positioned within the recess, provides electrical isolation that prevents leakage current while allowing the central fin part to maintain its structural position. The insulating layer acts as a mediator that enables the suspended configuration without compromising structural integrity.
Data Source
AI summary
The present invention provides a semiconductor structure, including a substrate, having a recess disposed therein, an insulating layer filled in the recess and disposed on a surface of the substrate, and at least one fin structure disposed in the insulating layer, the fin structure consisting of two terminal parts and a central part disposed between two terminal parts. The terminal parts are disposed on the surface of the substrate and directly contact the substrate, and the central part is disposed right above the recess.