Trench MOS Gate Structure for IGBT Diode Integration
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Solution Overview
Problem
Inverter devices with integrated IGBT and diode regions on a single semiconductor substrate face issues with normal bipolar operation due to electron carrier flow interruptions, leading to deteriorated diode output properties and increased ON voltage.
Innovation Solution
The semiconductor device incorporates a trench MOS gate structure with separate gate electrodes and insulating films to isolate the IGBT and diode regions, allowing for independent voltage control and preventing snapback by cutting off the connection between the drift layer and channel layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the IGBT and diode are disposed on the same substrate to integrate functions, then device complexity is reduced and productivity is improved, but the diode output properties deteriorate and snapback occurs due to electron carrier flow interruption
Solution Approach 1:
The gate electrode is divided into a first gate electrode in the IGBT region and a second gate electrode in the diode region, which are electrically isolated from each other. This segmentation allows independent control of the IGBT and diode regions, preventing electron carrier flow interruption from affecting diode operation while maintaining the integrated structure on a single substrate.
2Ease of operation
If a positive bias voltage is applied to the gate electrode to operate the IGBT, then the IGBT function is achieved, but electron carriers flow into the diode region interrupting bipolar operation and causing snapback
Solution Approach 1:
The gate electrode is segmented into first and second gate electrodes that are electrically isolated. The first gate electrode controls the IGBT region while the second gate electrode controls the diode region, allowing the IGBT to operate with positive bias voltage without causing electron carrier flow that would interrupt bipolar operation in the diode region.
Solution Approach 2:
An insulating film is introduced as an intermediary between the first gate electrode and the second gate electrode, and between the first gate electrode and the drift layer in the diode region. This insulating film prevents harmful electron carrier flow while allowing the IGBT to operate normally with positive bias voltage applied to the first gate electrode.
3Reliability
If the insulating film is formed to isolate the IGBT region from the diode region, then snapback is prevented and diode characteristics are improved, but manufacturing precision requirements increase
Solution Approach 1:
The gate electrode is segmented into first and second gate electrodes with an insulating film between them. The insulating film is formed in a controlled manner during the manufacturing process, isolating the IGBT and diode regions electrically while using standard fabrication techniques to manage precision requirements.
Solution Approach 2:
The insulating film serves as an intermediary layer that provides electrical isolation between the IGBT and diode regions. By positioning the insulating film strategically between the first gate electrode and the second gate electrode, and between the first gate electrode and the drift layer, reliable diode characteristics are achieved while the film can be formed using conventional semiconductor manufacturing processes.
Data Source
AI summary
A semiconductor device includes an IGBT region extending from a front surface to a rear surface of a semiconductor substrate including a first conductive type drift layer, and a diode region lying adjacent to the IGBT region. The IGBT region includes a second conductive type base layer on a side facing the front surface and a first trench portion penetrating the base layer. The first trench portion includes a first gate electrode, a second gate electrode provided directly below the first gate electrode, and an insulating film provided on a side surface of the first gate electrode, between the first gate electrode and the second gate electrode and in a position to contact the second gate electrode. The diode region includes a second conductive type anode layer and a second trench portion including a dummy gate electrode on the side facing the front surface.