Diode Guard Ring Cathode Impurity Region Current Concentration
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Solution Overview
Problem
Conventional semiconductor devices experience current concentration and breakdown issues at the outer peripheral end portion of the anode due to carrier accumulation under the guard ring, leading to reduced switching speed and increased power consumption during reverse recovery.
Innovation Solution
A semiconductor device with a cathode-side impurity region of the second conductivity type is formed opposite to the guard ring, reducing the volume of the n-type region under the guard ring and thereby decreasing carrier accumulation, which suppresses current concentration and enhances breakdown tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a guard ring is formed to surround the anode at a distance from the end of the anode, then the electric field on the outer peripheral end portion of the anode is alleviated, but carriers are accumulated in the drift layer region under the guard ring, causing current concentration and breakdown issues
Solution Approach 1:
The patent introduces a cathode-side impurity region of second conductivity type in the drift layer at a position opposite to the guard ring. This creates a localized region with different electrical properties (opposite conductivity type) to prevent carrier accumulation specifically in the area under the guard ring, thereby eliminating current concentration at the anode's outer peripheral end while maintaining the guard ring's electric field alleviation effect
Solution Approach 2:
The cathode-side impurity region acts as an intermediary structure between the guard ring and the drift layer. It mediates the carrier flow by providing recombination centers that prevent carriers from accumulating under the guard ring and flowing to the anode's outer peripheral end, thus resolving the harmful current concentration effect
2Power
If carriers are accumulated in the drift layer under the guard ring, then the diode can maintain adequate current conduction, but during reverse recovery large current and large voltage are applied causing heat generation and high power consumption
Solution Approach 1:
The cathode-side impurity region is locally introduced at the position opposite to the guard ring in the drift layer. This localized modification reduces carrier accumulation specifically in that region while maintaining adequate current conduction capability in other areas of the drift layer, thereby reducing reverse recovery power loss without sacrificing forward conduction performance
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 current concentration and improves breakdown tolerance by decreasing carrier flow to the outer peripheral end portion of the anode, leading to faster switching and reduced power consumption during reverse recovery.
Implementation Method 1
In the ON state of the diode, carriers are diffused and accumulated not only in a region of the drift layer that is located immediately under the anode but also a region of the drift layer that is located immediately under the guard ring
Data Source
AI summary
A semiconductor device is provided. On one main surface side of an n-type semiconductor substrate, a p-type diffusion region to serve as an anode of a diode is formed. A guard ring formed of a p-type diffusion region is formed to surround the anode. On the other main surface side, an n-type ultrahigh-concentration impurity layer and an n-type high-concentration impurity layer to serve as a cathode are formed. In a guard-ring opposed region located in the cathode and opposite to the guard ring, a cathode-side p-type diffusion region is formed. Accordingly, concentration of the electric current on an outer peripheral end portion of the anode is suppressed.