RC-IGBT Diode Trench Structure for Wider Reverse Recovery SOA
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Solution Overview
Problem
In RC-IGBTs with a split gate structure, the concentration of the electric field at the trench bottom portion leads to a narrow reverse recovery safe operation area (RRSOA), increasing the likelihood of breakage during recovery operations.
Innovation Solution
The semiconductor device design includes a deeper anode layer in the diode region compared to the diode trenches, which relaxes the electric field at the trench bottom, improving the RRSOA by covering and protecting the trench bottom portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the trench bottom portion is in contact with the drift layer, then the device structure is simple, but the electric field concentrates on the trench bottom portion causing narrow RRSOA and breakage risk
Solution Approach 1:
The patent introduces a new dimensional element by extending the anode layer deeper than the diode trenches, creating a three-dimensional protective structure. This depth dimension allows the anode layer to cover the trench bottom portion without increasing planar complexity, effectively resolving the electric field concentration issue while maintaining structural simplicity.
Solution Approach 2:
The anode layer serves as an intermediary protective element between the diode trenches and the drift layer. By positioning the anode layer to extend deeper than the trenches, it acts as a mediator that redistributes the electric field and protects the trench bottom portion, preventing direct contact between the trench and drift layer while avoiding complex structural modifications.
2Reliability
If the anode layer depth is increased to cover the trench bottom, then the electric field is relaxed and RRSOA is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by forming the anode layer with greater depth than the diode trenches during the initial fabrication sequence. This preliminary depth adjustment is performed before final device assembly, allowing the protective coverage to be established in advance. The anode layer is formed to extend through the drift layer, preemptively preventing electric field concentration issues without requiring post-manufacturing modifications.
Data Source
AI summary
An IGBT region and a diode region are provided on a semiconductor substrate. The IGBT region includes a plurality of active trenches penetrating through the base layer and the emitter layer from the first principal surface, a gate electrode provided inside the active trenches via a gate insulating film, and an implanted electrode provided inside the active trenches via the gate insulating film and positioned on the second principal surface side of the gate electrode. The diode region includes an anode layer of the second conductive type provided on the first principal surface side of the drift layer, a plurality of diode trenches provided from the first principal surface to the anode layer, and a diode electrode provided inside the diode trenches via a diode insulating film. A depth of the anode layer is deeper than a depth of the diode trenches.