SOI Body Contact Structures for Floating Body Effect Control
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Solution Overview
Problem
Silicon-on-insulator (SOI) integrated circuits face floating body effects, leading to issues like the 'kink' effect, abnormal threshold slope, low drain breakdown voltage, and noise overshoot, due to the lack of electrical connection to a specified reference potential, which affects transistor performance.
Innovation Solution
The implementation of body contact structures in SOI integrated circuits, where a gate structure is formed directly over shallow trench isolation structures, reducing gate resistance and stabilizing the body potential, and contact plugs are formed to connect the body contact region, source/drain regions, and gate structure, thereby eliminating floating body effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If SOI transistor body is dielectrically encapsulated to reduce parasitic capacitance, then switching speed is improved, but floating body effects occur causing kink effect and abnormal threshold slope
Solution Approach 1:
A body contact structure is introduced as an intermediary element between the isolated body and the substrate. This mediator provides a controlled electrical connection path that eliminates floating body effects while preserving the beneficial electrical isolation properties of the SOI structure.
Solution Approach 2:
The body contact structure is segmented into multiple components including contact openings through the insulating layer, contact regions in the body, and conductive pathways. This segmentation allows selective electrical connection at specific locations without compromising the overall isolation architecture.
2Reliability
If body contact structures are added to eliminate floating body effects, then transistor performance stability is improved, but device complexity increases
Solution Approach 1:
The body contact structure is merged with existing fabrication processes and features. Contact openings are formed using the same lithography and etching steps as other circuit features, and the contact regions are created during standard doping processes, thereby integrating the solution into the existing device architecture.
Solution Approach 2:
The body contact structure serves multiple functions simultaneously: it provides electrical connection to stabilize body potential, acts as a doping region for threshold voltage control, and can serve as a contact point for external biasing. This multi-functionality reduces the need for separate structures.
3Reliability
If gate structure is formed directly over shallow trench isolation structures, then gate resistance is reduced, but manufacturing precision requirements increase
Solution Approach 1:
Shallow trench isolation structures are formed preliminarily before gate fabrication. These pre-formed isolation structures serve as alignment references and define the precise locations where gates will be positioned, thereby simplifying subsequent alignment steps and reducing precision requirements.
Solution Approach 2:
The shallow trench isolation structures automatically define the gate positions through their geometric arrangement. The gate formation process utilizes the existing isolation structure geometry as a self-aligning template, eliminating the need for separate alignment procedures and reducing manufacturing precision requirements.
Data Source
AI summary
Silicon-on-insulator integrated circuits including body contact structures and methods for fabricating the same are disclosed. A method for fabricating a silicon-on-insulator integrated circuit includes filling a plurality of first and second shallow isolation trenches with an insulating material to form plurality of first and second shallow trench isolation (STI) structures, and forming a gate structure over the semiconductor layer that includes a first portion disposed over and parallel to at least two of the plurality of second STI structures and a second portion disposed in between the at least two of the plurality of second STI structures. The method further includes forming contact plugs to a body contact region of the semiconductor layer. The body contact region comprises a portion of the semiconductor layer between at least one of the plurality of first STI structures and at least one of the plurality of second STI structures.