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Self Aligning Subcollector and Isolation Regions in a Semiconductor

IP.com Disclosure Number: IPCOM000089504D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Lee, CH: AUTHOR

Abstract

The present self-aligned isolation technique eliminates problems due to the misalignment of the isolation region with the subcollector, and thereby improves device characteristics and yield. In Fig. 1, a mask comprising a first insulating layer 4, which is preferably silicon dioxide, is formed on substrate 2. The thickness of the initial oxide is advantageously around 3000 Angstroms. In the next step (Fig. 2), screen oxide layer 5 is formed atop the entire substrate, after which photoresist layer 8 is exposed and developed to expose the subcollector region. Subcollector 7 is then formed by ion implantation of arsenic through screen oxide 5.

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Self Aligning Subcollector and Isolation Regions in a Semiconductor

The present self-aligned isolation technique eliminates problems due to the misalignment of the isolation region with the subcollector, and thereby improves device characteristics and yield. In Fig. 1, a mask comprising a first insulating layer 4, which is preferably silicon dioxide, is formed on substrate 2. The thickness of the initial oxide is advantageously around 3000 Angstroms. In the next step (Fig. 2), screen oxide layer 5 is formed atop the entire substrate, after which photoresist layer 8 is exposed and developed to expose the subcollector region. Subcollector 7 is then formed by ion implantation of arsenic through screen oxide 5.

As shown in Fig. 3, photoresist layer 8 is removed and subcollector 7 is driven-in by a standard heating step which causes the reoxidation of the initial mask 4 and screen oxide 5. Typically, the thickness of oxide layer 4 is now around 6000 Angstroms, the thickness of layer 5 is around 3600 Angstroms, and the thickness of oxide layer 9 is around 1900 Angstroms.

In the next step (Fig. 4), the substrate is subjected to a dip etch, which is sufficient to remove completely oxide layer 9, leaving oxide layers 4 and 5 substantially unaffected. P+ isolation diffusion 10 is then made through the openings. Alternatively, another photoresist mask could be applied, and an isolation implant step accomplished.

This process insures the proper spacing of the subcollector an...