Latch-up Free Power Transistor Structure
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Solution Overview
Problem
Insulated-gate bipolar transistors (IGBTs) are susceptible to latch-up, a condition that prevents the insulated gate from controlling current or turning the IGBT off, leading to malfunction and potential destruction due to the parasitic NPN bipolar junction transistor in their vertical structure.
Innovation Solution
The implementation of a latch-up free power transistor structure where the highly doped emitter diffusion region is omitted, replaced by an emitter electrode or emitter layer that makes direct physical contact with the conduction channel, eliminating the parasitic bipolar junction transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a highly doped emitter diffusion region is used in conventional IGBT structure, then good electrical contact and current injection are achieved, but parasitic bipolar junction transistor is formed causing latch-up
Solution Approach 1:
The patent extracts and removes the highly doped emitter diffusion region from the conventional IGBT structure. By taking out this specific component that causes parasitic bipolar junction formation, the latch-up problem is eliminated while maintaining the essential functionality of the device through alternative emitter electrode design.
Solution Approach 2:
The patent introduces an intermediary approach by using a lightly doped emitter region combined with a metal emitter electrode instead of direct highly doped diffusion contact. This intermediary structure prevents parasitic bipolar junction formation while still achieving the necessary electrical contact and current injection functions.
2Reliability
If emitter electrode makes direct contact with conduction channel, then parasitic bipolar junction transistor is eliminated, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by forming the lightly doped emitter region and positioning the emitter electrode structure before final assembly steps. This preliminary structuring establishes the correct geometric relationships and contact positions, reducing the precision demands on subsequent manufacturing operations.
Solution Approach 2:
The patent changes the doping parameter of the emitter region from highly doped to lightly doped, which fundamentally alters the electrical characteristics and eliminates parasitic bipolar junction formation. This parameter change allows for more tolerant manufacturing tolerances while maintaining device functionality.
Data Source
AI summary
There are disclosed herein various implementations of a latch-up free power transistor. Such a device includes an insulated gate situated adjacent to a conduction channel in the power transistor, an emitter electrode in direct physical contact with the conduction channel, and a collector electrode in electrical contact with the conduction channel. The power transistor also includes an emitter layer in contact with a surface of a semiconductor substrate adjacent the conduction channel.