Semiconductor Edge Termination for Breakdown Voltage
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Solution Overview
Problem
Existing power semiconductor devices with high breakdown voltage suffer from decreased current density and increased forward voltage drop during the recovery operation from ON to OFF state, leading to thermal destruction and oscillation issues due to carrier accumulation in the edge termination region.
Innovation Solution
The semiconductor device incorporates a diode active region and an edge termination region with specific conductivity type regions and impurity concentrations, including a p-type region with higher impurity concentration and a buffer layer, to manage carrier lifetime and reduce current density in the edge termination region, thereby increasing breakdown voltage and suppressing oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a p-type diffusion region is formed on the cathode side to reduce current concentration in the OFF state, then breakdown voltage increases, but current density in the forward direction decreases
Solution Approach 1:
The patent applies local quality by forming a p-type diffusion region specifically in the edge termination region (peripheral area) while keeping the main diode active region free of such structures. This localized approach allows the edge region to have different electrical characteristics (higher breakdown voltage) without affecting the current-carrying capability of the central active region, thus resolving the contradiction between improving breakdown voltage and maintaining current density.
2Productivity
If carriers are accumulated in the drift layer during ON state, then forward current increases, but voltage rise and drop during recovery operation increases
Solution Approach 1:
The patent extracts the problematic carrier accumulation effect from the main active region by introducing a dedicated edge termination region with different properties. The p-type diffusion region in the edge area creates a depletion layer that prevents excessive carrier accumulation at the periphery during recovery, thereby removing the source of voltage oscillation while preserving the necessary carrier dynamics in the central active region for high forward current.
3Strength
If the volume of the n-type region on the cathode side is decreased to reduce current concentration, then breakdown voltage increases, but the safe operating area during recovery decreases
Solution Approach 1:
The patent segments the diode structure into two distinct functional zones: the diode active region for current conduction and the edge termination region for voltage withstanding. By separating these functions spatially, the device can simultaneously achieve high breakdown voltage (through the engineered edge region) and maintain a large safe operating area (through the intact active region), resolving the contradiction between these two performance parameters.
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 ensures stable current flow through the diode active region while preventing thermal destruction and oscillation, expanding the safe operating area during recovery operations by optimizing carrier recombination and reducing forward voltage drop.
Implementation Method 1
The drift region in the third region is greater in number of crystal defects per unit volume than the drift region in the first region in order that the drift region in the third region is shorter in carrier lifetime than the drift region in the first region
Data Source
AI summary
A semiconductor device includes a semiconductor substrate having a diode active region and an edge termination region adjacent to each other, a first region of a first conductivity type in the diode active region, a second region of a second conductivity type, a third region of the first conductivity type in the edge termination region, and a fourth region of the second conductivity type. The first region and the third region share a drift region of the first conductivity type. The first region and the third region share a fifth region of the first conductivity type. The drift region in the third region is greater in number of crystal defects per unit volume than the drift region in the first region in order that the drift region in the third region is shorter in carrier lifetime than the drift region in the first region.