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Oxide, Boron Isolation

IP.com Disclosure Number: IPCOM000079164D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Rakowski, DW: AUTHOR

Abstract

This is a method of creating close base-to-isolation spacing through the utilization of a combined oxide isolation and boron diffusion isolation.

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Oxide, Boron Isolation

This is a method of creating close base-to-isolation spacing through the utilization of a combined oxide isolation and boron diffusion isolation.

The technique comprises, as shown Fig. 1A, the placing of a suitable isolation mask 14 over an N-type epitaxial (EPI) layer 12 formed on a silicon body 10. The isolation is to be created in the epitaxial layer 12 and must penetrate the interface 11 between the layer 12 and the body 10. An opening 16 is formed in the mask 14 and part of the epitaxial layer 12 is etched away as shown at 18 in Fig. 1B.

Instead of etching 40 to 60% through the epitaxial area as done in the so- called isoplaner process, the EPI layer is etched 10 to 20% of the way through. The etched away area is then oxidized to form a thin reoxidation layer 20, 1500 to 2000 angstroms in thickness in the etched away area.

A block mask 22 is then provided over the entire device, as shown in Fig. 1C. The center of the etched area is exposed by etching an opening 21 in the layer 20, as shown in Fig. 1D. A boron diffusion 24 is made through the opening 21 into the underlying epitaxial layer 12. This boron diffusion 24, being P-type, isolates and penetrates through the interface 11 to the underlying substrate 10, as shown in Fig. 1E. Alternately, a shallow boron diffusion can be performed as shown in Fig. 1F.

Following the boron diffusion, a long oxidation is performed to create oxide layer 26, as shown in Fig. 1G, which is thick enough to...