Semiconductor Device Withstand Voltage Shell Region Design
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Solution Overview
Problem
Conventional reverse blocking IGBTs face issues with lower reverse withstand voltage compared to forward withstand voltage, leading to increased reverse leakage current and oscillations in turnoff and reverse recovery waveforms, which can cause device breakdown.
Innovation Solution
A semiconductor device structure is introduced with a heavily doped shell region between the drift and base regions, and a lightly doped shell region between the collector and base regions, along with a breakdown withstanding region, to prevent depletion layer reach-through and reduce minority carrier injection, thereby improving both forward and reverse withstand voltages and suppressing waveform oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the depletion layer is allowed to expand freely, then the device can handle high voltages, but the depletion layer reaches through to the collector region causing instability
Solution Approach 1:
The shell region acts as an intermediary layer between the drift region and base region. This intermediate structure prevents the depletion layer from reaching through to the collector region by providing a buffer zone with controlled impurity concentration, thereby stabilizing the depletion layer position while maintaining high voltage handling capability.
2Power
If minority carrier injection is increased, then the ON-voltage characteristics improve, but the turnoff loss increases
Solution Approach 1:
The patent modifies the impurity concentration parameter in the shell region (average impurity amount of 8.0×10^11 cm^-2 or smaller) to optimize the balance between minority carrier injection and turnoff loss. By precisely controlling this parameter, the device achieves improved ON-voltage characteristics while minimizing turnoff energy loss.
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 proposed structure effectively enhances reverse and forward withstand voltages, prevents reach-through phenomena, and reduces oscillations in turnoff and reverse recovery waveforms, ensuring stable device operation.
Implementation Method 1
the first semiconductor region exhibiting a resistivity low enough to prevent expansion of a depletion layer expanding from the fifth semiconductor region
Implementation Method 2
Breakdown withstanding region 120 relaxes the electric field strength on the pn-junction constituting the semiconductor device and realizes the desired withstand voltages
Data Source
AI summary
A semiconductor device according to embodiments of the invention includes an n−-type drift region; a p-type base region formed selectively in the surface portion of the drift region; an n+-type emitter region and a p+-type body region, both formed selectively in the surface portion of base region; and an n-type shell region between the drift region and the base region, a shell region surrounding the entire region below base region. The shell region is doped more heavily than the drift region. The shell region contains an n-type impurity at an effective impurity amount of 8.0×1011 cm −2 or smaller. A drift region exhibits a resistivity low enough to prevent the depletion layer expanding from collector region, formed on the back surface of the drift region, toward a shell region from reaching the shell region.