Guard Ring Field Plate Structure for Galvanic Corrosion Control
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Solution Overview
Problem
Semiconductor devices with termination structures suffer from galvanic corrosion due to dissimilar metals in hot and humid environments, particularly when the barrier metal layer protrudes from the field electrode, leading to reliability issues and increased corrosion risk.
Innovation Solution
A semiconductor device with a guard ring structure featuring a laminated metal layer configuration where the second metal, with a lower standard potential, covers at least 90% of the first metal's surface area, reducing the corrosion risk by minimizing the contact area ratio between dissimilar metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a barrier metal layer protrudes from both sides of the field electrode to reduce termination structure size, then the device size is reduced, but galvanic corrosion occurs between dissimilar metals in hot and humid environments
Solution Approach 1:
A third metal layer with intermediate standard potential is introduced between the barrier metal layer (high potential) and the field electrode (low potential). This intermediary layer acts as a mediator that breaks the direct galvanic couple between dissimilar metals, significantly reducing the galvanic corrosion current while maintaining the compact termination structure design.
Solution Approach 2:
The field electrode is constructed as a multi-layer composite structure comprising a barrier metal layer, an intermediate metal layer, and a base metal layer. This composite structure combines materials with different standard potentials in a controlled sequence, creating a gradient that reduces galvanic corrosion while maintaining electrical functionality and compact dimensions.
2Strength
If dissimilar metals are used in the termination structure to achieve higher withstand voltage, then the electrical performance is improved, but galvanic corrosion is accelerated due to large area ratio of high potential metal
Solution Approach 1:
The intermediate metal layer is strategically positioned only in the regions where galvanic corrosion is most severe - specifically where the barrier metal layer contacts the environment or other metals. This localized application of the intermediary material effectively reduces galvanic corrosion current in critical areas while maintaining the overall high withstand voltage capability of the termination structure.
Solution Approach 2:
The intermediate metal layer serves as a protective mediator that physically separates the high potential barrier metal from the low potential base metal, preventing direct galvanic interaction. This intermediary layer reduces the galvanic corrosion rate by providing a less aggressive electrochemical environment for the base metal while preserving the electrical field distribution needed for high withstand voltage.
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 solution effectively prevents corrosion and enhances the reliability and service life of semiconductor devices and power conversion systems by stabilizing the electric field and shielding against moisture and external charges.
Implementation Method 1
a problem of galvanic corrosion has been found in which dissimilar metals become local batteries and corrode under a hot and humid environment when a part of the barrier metal layer protrudes from both sides of the field electrode
Data Source
AI summary
A termination structure in which a semiconductor active region is surrounded with a guard ring and capable of preventing corrosion of a metal layer connected to the guard ring includes: an active region and a guard ring region surrounding the active region. A guard ring is formed on the semiconductor substrate, and an interlayer insulating film is formed on the semiconductor substrate so as to cover the guard ring. A field plate is disposed on the interlayer insulating film and is electrically connected to the guard ring via a contact penetrating the interlayer insulating film. A protective film covers the field plate, which has a laminated structure including a first metal in contact with the guard ring and a second metal which is disposed in contact with the first metal and has a lower standard potential than the first metal.