FET Guard Ring Layout for Moisture-Induced Short Circuit Prevention
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Solution Overview
Problem
Field effect transistors experience short circuits due to ion migration of metals in conductive bonding materials, particularly in humid environments, leading to defective operation and reduced moisture resistance.
Innovation Solution
Incorporating a gate guard and drain guard made of metal, electrically connected to the back metal film, with the drain guard in a non-conductive state relative to the gate, source, and drain electrodes, to reduce electric fields and prevent dendrite growth, thereby enhancing moisture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal conductive bonding materials are used to connect the back metal film to the base member, then electrical conductivity is improved, but ion migration occurs in humid environments causing short circuits and reduced reliability
Solution Approach 1:
The patent introduces a guard ring structure as an intermediary element between the metal conductive bonding material and the gate electrode. This guard ring acts as a protective barrier that intercepts and redirects electric fields, preventing ion migration from the conductive bonding material from reaching the gate electrode and causing short circuits. The guard ring is electrically connected to a lower potential node, creating a potential barrier that stops ion migration while maintaining the electrical conductivity function of the original bonding material.
Solution Approach 2:
The guard ring is positioned and electrically connected in advance to create a counteracting electric field that opposes the harmful ion migration process. By establishing this protective electric field configuration before ion migration can occur, the system preemptively prevents the harmful effect rather than reacting to it after damage occurs.
2Reliability
If guard ring structures are added to prevent ion migration, then reliability is improved, but device complexity increases
Solution Approach 1:
The guard ring structure is merged with the existing conductive bonding material and electrical connection architecture. Rather than adding a completely separate protective system, the guard ring is integrated into the current device structure, sharing space and functional pathways with existing components. This reduces the overall complexity increase compared to adding entirely separate protective structures.
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 reduces the likelihood of short circuits and improves the moisture resistance of field effect transistors by minimizing ion migration and dendrite formation, ensuring reliable operation even in humid conditions.
Implementation Method 1
a metal film on the back surface and electrically connected to the gate guard. The drain guard is in a non-conductive state with respect to the metal film, the gate electrode, the source electrode, and the drain electrode
Data Source
AI summary
A field effect transistor includes: a semiconductor region including a first inactive region, an active region, and a second inactive region arranged side by side in a first direction; a gate electrode, a source electrode, and a drain electrode on the active region; a gate pad on the first inactive region; a gate guard on and in contact with the semiconductor region, the gate guard being apart from the gate pad and located between an edge on the first inactive region side of the semiconductor region and the gate pad; a drain pad on the second inactive region; a drain guard on and in contact with the semiconductor region, the drain guard being apart from the drain pad and located between an edge on the second inactive region side of the semiconductor region and the drain pad; and a metal film electrically connected to the gate guard.