IGBT Diode Guard Ring Segmentation for Reverse Recovery
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Solution Overview
Problem
The existing semiconductor devices with IGBT and diode regions on the same substrate face limitations in peak recovery current due to local current concentration at the boundary between the diode and guard ring, which restricts the diode's reverse recovery performance.
Innovation Solution
The semiconductor device incorporates a guard ring with the same potential as the anode layer, positioned such that the ratio of the minimum distance between the cathode layer and the guard ring to the substrate thickness (L/d) is greater than or equal to 1.5, reducing carrier injection from the guard ring and minimizing hole accumulation, thereby suppressing local current concentration and enhancing peak recovery current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the guard ring is electrically connected to the base layer to enhance breakdown voltage, then the breakdown voltage is improved, but local current concentration occurs at the boundary between the diode and guard ring, reducing peak recovery current
Solution Approach 1:
The guard ring is divided into two segments: an inner guard ring electrically connected to the base layer for breakdown voltage enhancement, and an outer guard ring electrically connected to the anode layer for reducing hole accumulation. This segmentation allows each guard ring segment to perform its specific function independently, resolving the contradiction between breakdown voltage and peak recovery current.
Solution Approach 2:
The outer guard ring acts as an intermediary structure between the diode region and the peripheral region. By being electrically connected to the anode layer, it mediates the electric field distribution and prevents excessive hole accumulation at the diode boundary, thereby improving peak recovery current without compromising breakdown voltage.
2Ease of operation
If holes are supplied from the guard ring to the drift layer during forward bias, then the conducting state is maintained, but excessive hole accumulation occurs in the drift layer, causing current concentration during reverse recovery
Solution Approach 1:
Different regions of the guard ring are assigned different electrical connections to achieve local quality optimization. The inner guard ring (connected to base layer) maintains forward conduction by supplying holes, while the outer guard ring (connected to anode layer) prevents excessive hole accumulation by providing an alternative hole sink, thus resolving the contradiction between forward conduction and reverse recovery 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
This configuration ensures dominant carrier conduction between the anode and cathode layers, reducing the flow of holes into the anode layer during reverse bias, thus increasing the peak recovery current of the diode and preventing current concentration.
Implementation Method 1
holes supplied from the base layer and the guard ring, and electrons supplied from the cathode layer are accumulated in the drift layer
Implementation Method 2
The guard rings are provided for enhancing the breakdown voltage of the semiconductor device by extending depletion layers formed from the base layer and the anode layer in a direction along the surface of the substrate to reduce the electric field strength when high voltage is applied to the IGBT regions
Implementation Method 3
holes supplied from the anode layer (base layer) and electrons supplied from the cathode layer couple to each other in the drift layer, or reach opposite layers so that forward current flows
Data Source
AI summary
A semiconductor device has a semiconductor substrate including an IGBT region operating as an IGBT provided by an emitter layer, a base layer, a drift layer and a collector layer, and a diode region operating as a diode and provided by an anode layer, the drift layer and a cathode layer. The semiconductor substrate further includes a guard ring of a second conduction type, provided in a surface layer of the drift layer in a peripheral region surrounding a device region where the IGBT region and the diode region are adjacent to each other. The cathode layer and the guard ring are positioned such as to satisfy L/d≥1.5, where L is a minimum value of a distance between the cathode layer and the guard ring as projected to a plane parallel to a surface of the semiconductor substrate, and d is a thickness of the semiconductor substrate.