IGBT Emitter Sense Layout for Short-Circuit Current Suppression
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Solution Overview
Problem
Conventional power semiconductor devices using IGBTs face reliability issues due to potential distribution in the emitter electrode, leading to increased main current during short circuits, which can cause thermal breakdown.
Innovation Solution
The semiconductor device incorporates a surface electrode with an insulating film having an opening region, a chip bonding material with a matching surface shape, and a sense pad connected by a sense wiring, where the control reference potential is derived from the surface electrode, and the device includes an ineffective region below the sense pad to reduce current flow in remote regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If potential from outer peripheral region of emitter electrode is used as emitter potential for controlling IGBT, then gate voltage control is achieved, but main current increases during short circuit due to potential distribution, causing thermal breakdown
Solution Approach 1:
The emitter electrode is divided into two distinct regions: a wiring connection region in the central portion for main current flow, and an outer peripheral region for obtaining control reference potential. This segmentation allows the control reference potential to be obtained from a region that does not experience significant potential drops during high current flow, thereby preventing main current increase and thermal breakdown while maintaining proper gate voltage control.
2Reliability
If emitter electrode has minute resistance component, then electrical connection is achieved, but potential distribution occurs in emitter electrode plane when current flows
Solution Approach 1:
Different regions of the emitter electrode are assigned different functions based on their local characteristics. The central wiring connection region is optimized for low resistance and high current carrying capacity, while the outer peripheral region is optimized for providing a stable reference potential. This local quality differentiation allows the system to tolerate the minute resistance of the emitter electrode without suffering from harmful potential distribution effects.
3Power
If large current flows through IGBT during short circuit, then main current increases, but IGBT chip may be thermally broken
Solution Approach 1:
The outer peripheral region of the emitter electrode acts as an intermediary for obtaining the control reference potential. By deriving the reference potential from this region rather than from the central wiring connection region, the control system is isolated from the harmful potential drops that occur during high current flow. This intermediary approach allows the IGBT to handle large currents during short circuits without experiencing the thermal breakdown that would result from uncontrolled main current increase.
Data Source
AI summary
The semiconductor device according to the present disclosure has features (1) to (3) below. The feature (1) is that “a lower surface of an on-chip bonding material has a shape matching a surface shape of a main current wiring connection region in plan view”. The feature (2) is that “an emitter sense wiring is directly connected to a side surface of the main current wiring connection region”. The feature (3) is that “an IGBT chip has an ineffective region in which the IGBT does not function in a region below an emitter sense pad and the emitter sense wiring”.