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Polysilicon as a Diffusion Source for Subcollector Formation

IP.com Disclosure Number: IPCOM000052173D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Abbas, SA: AUTHOR [+3]

Abstract

The subcollector of a bipolar transistor can be formed by using a consumable polycrystalline silicon layer acting as the diffusion source. This method allows the subsequent growth of high quality epitaxial silicon. The fact that the dopant is totally ion-implanted in the polycrystalline silicon layer limits the damage to that subcollector region. This means that the surface of the silicon in the subcollector region is essentially defect-free, and the silicon epitaxy grown has better quality.

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Polysilicon as a Diffusion Source for Subcollector Formation

The subcollector of a bipolar transistor can be formed by using a consumable polycrystalline silicon layer acting as the diffusion source. This method allows the subsequent growth of high quality epitaxial silicon. The fact that the dopant is totally ion-implanted in the polycrystalline silicon layer limits the damage to that subcollector region. This means that the surface of the silicon in the subcollector region is essentially defect-free, and the silicon epitaxy grown has better quality.

There are a number of alternatives for implementing this method. One such method is as follows: 1. Grow on a P-silicon substrate a layer of silicon dioxide.
2. Define windows in the silicon dioxide layer for the subcollector. 3. Deposit a layer of polysilicon in the range of 1000 Angstroms, thermally oxidize the surface to about 200 to 500 Angstroms of silicon dioxide, and blanket ion implant the layer with As or B with such energy that the dopant is contained in the polysilicon. The dose will be in the range of 10/16/- 10/17/. 4. Thermally drive-in and reoxidize the surface to consume the polysilicon layer totally and turn it into silicon dioxide. Simultaneously the dopant is driven into the silicon substrate to form the subcollector. 5. Define the Pisolation regions, diffuse using BBr and also drive-in to form the channel stop regions. 6. Remove all silicon dioxide. The substrate is now ready for epitaxial silicon...