Gate-Fin Field Effect Transistors for Surface Breakdown Control
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Solution Overview
Problem
Field effect transistors often suffer from surface breakdown voltage due to complex extended low doped drain (LDD) structures, which increase process complexity and cost.
Innovation Solution
A semiconductor structure with a shallow trench isolation structure and a field effect transistor featuring line trenches, a channel region, a gate dielectric contacting all surfaces of the trenches, a gate electrode with planar and fin portions, and source and drain regions laterally spaced by the channel region, along with a method of forming these components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex extended low doped drain (LDD) structures are used to improve surface breakdown characteristics, then surface breakdown voltage is improved, but process complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the essential function of the complex LDD structure (surface breakdown protection) and implements it through a simplified gate electrode fin structure that protrudes into the trench. This removes the need for complex extended LDD structures while maintaining the surface breakdown characteristics through the gate fin geometry and positioning.
Solution Approach 2:
Instead of using extended LDD structures to protect the surface, the patent inverts the approach by using the gate electrode fin protruding into the trench to provide the breakdown protection. The gate fin structure, rather than the drain extension, becomes the primary element for controlling surface breakdown characteristics.
2Reliability
If complex extended low doped drain (LDD) structures are used to improve surface breakdown characteristics, then surface breakdown voltage is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the need for complex extended LDD structures and their associated manufacturing steps. The gate electrode fin structure alone provides the necessary surface breakdown protection, eliminating the need for separate LDD extension processes and reducing overall manufacturing complexity and cost.
Solution Approach 2:
The patent combines the gate electrode structure with the breakdown protection function. The gate electrode fin protruding into the trench serves dual purposes: controlling the channel and providing surface breakdown protection, thereby eliminating the need for separate LDD structures and reducing manufacturing steps.
3Reliability
If line trenches with gate dielectric contacting all surfaces are used, then surface breakdown characteristics are improved, but device structure complexity increases
Solution Approach 1:
The patent applies gate dielectric material selectively to contact all surfaces of the line trench where it is most needed for breakdown protection. The gate electrode fin protrudes into the trench with gate dielectric coating on its surfaces, providing localized breakdown protection exactly where the electric field is most concentrated, rather than uniformly throughout the entire device structure.
Data Source
AI summary
A field effect transistor includes at least one line trench extending downward from a top surface of a channel region which laterally surrounds or underlies the at least one line trench, a gate dielectric contacting all surfaces of the at least one line trench and including a planar gate dielectric portion that extends over an entirety of a top surface of the channel region, a gate electrode, a source region, and a drain region.