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Multicollector High Voltage Power Transistor Design

IP.com Disclosure Number: IPCOM000087390D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Jambotkar, CG: AUTHOR [+2]

Abstract

A device structure which leads to better second breakdown capability without sacrificing the current gain and the collector-emitter saturation voltage is shown in Fig. 1. This structure is formed by introducing a low resistivity N type epitaxial layer sandwiched between the N-collector and the N+ substrate regions. The resistivity and the thickness of this added layer are small compared to the N- collector region, such that the device "ON" characteristics are not affected substantially. During the turn-off condition, the collector depletion region can further extend to this N region, which lowers the critical electric field in the N- collector-N+ substrate junction region and, therefore, enhances the second breakdown voltage capability.

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Multicollector High Voltage Power Transistor Design

A device structure which leads to better second breakdown capability without sacrificing the current gain and the collector-emitter saturation voltage is shown in Fig. 1. This structure is formed by introducing a low resistivity N type epitaxial layer sandwiched between the N-collector and the N+ substrate regions. The resistivity and the thickness of this added layer are small compared to the N- collector region, such that the device "ON" characteristics are not affected substantially. During the turn-off condition, the collector depletion region can further extend to this N region, which lowers the critical electric field in the N- collector-N+ substrate junction region and, therefore, enhances the second breakdown voltage capability. As an example, a conventional N+ P N- N+ structure, with collector resistivity of 40 Omega-cm (approximately = 10/14 atoms/cc) and thickness of 50 Mu, yields a second breakdown voltage of about 500V. The addition of the sandwiched N layer, having resistivity 10 Omega-cm (approximately = 5x10/14/ atoms/cc) and thickness 15 Mu, yields a second breakdown voltage characteristic of 575V, a 15% increase. At the same time, at a given V(CE) (for example, V(CE) = 3V) the current gain experiences less than 4% reduction. Thus, the breakdown voltage improvement exceeds the current gain loss.

This N+ P N- N N+ structure offers a higher second breakdown voltage than the conventional N+ P N- N+...