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A PROCESS FOR FABRICATING LOW VOLTAGE/DEEP JUNCTION ZENERS AND RECTIFIERS

IP.com Disclosure Number: IPCOM000006044D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Nov-28
Document File: 1 page(s) / 44K

Publishing Venue

Motorola

Related People

Mark Schoenberg: AUTHOR

Abstract

Two boron ion implantations into a heavily doped phosphorous substrate are used to obtain both a deep junction and an extremely steep junction gradient in addition to a very high boron surface concentration. The first ion implantation step together with the appropriate diffusion cycle sets the junction to approximately 75% of its final depth. The second ion implantation step combined with the appropriate diffusion cycle overlaps the first diffused profile and allows one to steepen the junction gradient in addition to enhancing the surface concentration. It was found that up to three times the historic junction depth was achieved while maintaining the required junction steepness. This technique is extremely valuable in reducing vulnerability to surface defects generated in fabrication.

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MOTOROLA INC. Technical Developments Volume 12 April 1991

A PROCESS FOR FABRICATING LOW VOLTAGE/DEEP JUNCTION ZENERS AND RECTIFIERS

by Mark Schoenberg

  Two boron ion implantations into a heavily doped phosphorous substrate are used to obtain both a deep junction and an extremely steep junction gradient in addition to a very high boron surface concentration. The first ion implantation step together with the appropriate diffusion cycle sets the junction to approximately 75% of its final depth. The second ion implantation step combined with the appropriate diffusion cycle overlaps the first diffused profile and allows one to steepen the junction gradient in addition

to enhancing the surface concentration. It was found that up to three times the historic junction depth was achieved while maintaining the required junction steepness. This technique is extremely valuable in reducing vulnerability to surface defects generated in fabrication.

  Figure 1 gives the boron dopant profile after the first ion implantation step and first drive-in. Figure 2 gives the final boron dopant profile after the second ion implantation step and second drive-in.

DOPANTCONCENTRATlON

SILICON

SURFACE .

P+ REGION

DEPTH IN SILICON

N+ SUBSTRATE

ILE AFTFR FIRST

WPANTCONCENTRATION

I

PC REGION I

S'L'CoN LJ+ SUBSTRATE

DOPANT PROF,, F AFTFR SECOND ION IMPLANTATlONAND DRIVE-IN

0 Motorola, 1°C. ,991 15

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