Schottky Isolated NMOS Guard Ring for Latch-Up Prevention
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Solution Overview
Problem
Integrated circuits face latch-up conditions due to undesirable crosstalk between devices, which can lead to uncontrolled current draw and potential permanent damage, particularly in CMOS-based circuits where parasitic NPN transistors can be activated unintentionally.
Innovation Solution
Incorporating a Schottky junction in the guard ring structure around semiconductor devices to prevent latch-up by generating a Schottky diode that switches into forward or reverse mode depending on the supply voltage, reducing parasitic NPN safe operating area failures and terminating PNPN paths, thereby isolating devices effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional guard rings are used to prevent latch-up, then device isolation is improved, but power consumption increases
Solution Approach 1:
The patent changes the electrical parameters of the guard ring by incorporating Schottky junctions, which have different voltage-current characteristics compared to conventional PN junctions. This allows the guard ring to operate with lower power consumption while maintaining latch-up prevention functionality.
Solution Approach 2:
The guard ring structure combines different materials forming Schottky junctions (metal-semiconductor interfaces) with the semiconductor substrate, creating a composite structure that achieves both isolation and reduced power consumption through the unique properties of Schottky barriers.
2Reliability
If guard ring size is increased to improve isolation, then latch-up prevention is improved, but device area increases
Solution Approach 1:
By changing the electrical parameters through Schottky junctions, the patent achieves effective isolation with smaller physical dimensions, as the Schottky barriers provide strong potential barriers that prevent parasitic current flow more efficiently per unit area.
Solution Approach 2:
The invention extracts and utilizes the specific properties of Schottky junctions (high barrier height, low leakage current) to achieve isolation functionality with reduced material and space, removing the need for large conventional guard ring structures.
3Reliability
If conventional guard rings are used, then parasitic current collection is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the guard ring isolation function with Schottky junction formation, combining multiple functions into a single integrated structure that collects parasitic currents while maintaining simplicity in the overall device architecture.
Solution Approach 2:
By utilizing standard Schottky contact formation processes already present in semiconductor manufacturing, the patent achieves improved parasitic current collection without adding significant manufacturing steps or complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The Schottky junction guard ring structure effectively prevents latch-up failures, reduces power consumption by 50% during normal operation, and allows for rule sizing without process changes, enhancing the safe operating area of NMOS transistors.
Implementation Method 1
Incorporating a Schottky junction in the guard ring structure around semiconductor devices to prevent latch-up by generating a Schottky diode that switches into forward or reverse mode depending on the supply voltage
Implementation Method 2
terminating PNPN paths, thereby isolating devices effectively
Data Source
AI summary
An integrated circuit structure includes a substrate, a semiconductor device supported by the substrate, and a guard ring structure disposed around the semiconductor device, the guard ring structure forming a Schottky junction. In an embodiment, the Schottky junction is formed from a p-type metal contact and an n-type guard ring. In an embodiment, the guard ring structure is electrically coupled to a positive or negative supply voltage.