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Stable Zener Diode

IP.com Disclosure Number: IPCOM000086723D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Stephens, GB: AUTHOR

Abstract

The instability of surface states is known to cause drift in the reverse voltage-current characteristic of Zener diodes. A horizontal layout of the diode which minimizes the junction periphery intersecting the surface has been found to reduce such drift. An ion implant which lowers the surface concentration near the surface also aids in reducing drift.

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Stable Zener Diode

The instability of surface states is known to cause drift in the reverse voltage-current characteristic of Zener diodes. A horizontal layout of the diode which minimizes the junction periphery intersecting the surface has been found to reduce such drift. An ion implant which lowers the surface concentration near the surface also aids in reducing drift.

A horizontal layout for a Zener diode is shown in Figs. 1A and 1B. An N-type substrate 10 includes an N+ diffusion region 12 and a P region 14, a portion of which underlies the region 12. The region 14 also includes a channel section 16 which connects the Zener junction 18 to the substrate surface. An oxide layer 20 overlies the substrate 10 and includes appropriate openings 22 for electrical contact to the regions 12 and 14.

The predominant reverse current in the layout will be in an area "B" of Fig. 1A. The reverse current will not be affected by changes in surface state in the channel region 16. The area "B" can be made large with respect to the channel region 16 such that higher current Zeners can be made without increasing the surface area of the junction, with a resulting depletion region at the surface.

Fig. 2 shows possible diffusion profiles for regions 12 and 14.

By use of an ion implant the P region in channel 16 can be made to have a surface concentration lower than that below the surface since point "B" is the highest concentration intercept of the regions 12 and 14, the Zener breakd...