US 6,310,365 B1Granted

Surface voltage sustaining structure for semiconductor devices having floating voltage terminal

AssigneeUniversity of Electronic Science and Technology

InventorXingbi Chen

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Abstract

A surface voltage sustaining structure for semiconductor device which includes at least one high-side high-voltage device, comprises at least two surface voltage sustaining regions, wherein a first surface voltage sustaining region is for sustaining a voltage drop from a high voltage terminal of the high-side high-voltage device to a floating voltage terminal of the high-side high-voltage device, and a second surface voltage sustaining region is for sustaining a voltage drop from said high voltage terminal or from said floating voltage terminal to the substrate. The potential of the floating-voltage terminal of the high-side high-voltage device can vary (float) from the potential of the substrate up to the potential of the high voltage terminal. By means of the present invention, not only a high-side high-voltage device but also a low-side high-voltage device with a high voltage terminal having potential being the same as the floating voltage terminal and a low voltage terminal having potential being the same as the potential of the substrate, and integrated circuit devices with common terminals having a potential being the same as the floating voltage terminal, as well as integrated circuit devices with common terminals having a potential being the same as the substrate can be implemented simultaneously on a single chip without using dielectric isolation technique or p-n junction isolation technique. The technique of the present invention is technologically compatible to the CMOS or BiCMOS technique.

A surface voltage sustaining structure for semiconductor device which comprises a substrate of first conductivity type, a heavily doped region of second conductivity type formed on said substrate, and one or more high-voltage terminals and one or more floating voltage terminals, wherein said surface voltage sustaining structure comprises:

a first surface voltage sustaining region for sustaining a voltage drop from one of said high-voltage terminals to one of said floating voltage terminals, including part of said heavily doped region of second conductivity type under the high-voltage terminal and several zones of first conductivity type formed in said heavily doped region of second conductivity type apart from said high-voltage terminal and having doping density increasing gradually or stepwisely as increasing of a distance to the high-voltage terminal, wherein said floating voltage terminal is located at one having largest doping density of said zones of the first conductivity type;
and
a second surface voltage sustaining region for sustaining a voltage drop from said high-voltage terminal or floating voltage terminal to the substrate, including part of said heavily doped region of second conductivity type surrounding said first surface voltage sustaining region and several zones of second conductivity type in said heavily doped region of the second conductivity type, of which the effective density of ionized impurities of the second conductivity type reduces gradually or stepwisely as increasing of a distance to said high-voltage terminal or said floating voltage terminal, wherein said effective density of ionized impurities means a value obtained in the manner that when a voltage applied across the high voltage terminal and the substrate or across the floating voltage terminal and the substrate is close to the breakdown voltage, the total number of the effective ionized impurities of the second conductivity type in a surface area having a lateral dimension smaller than Wpp divides by said surface area, wherein Wpp is a depletion width of an one-sided abrupt plane junction made by the same substrate under its breakdown voltage.

Abstract

Claims20