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Eliminating Si(3)N(4) for Emitter Masking

IP.com Disclosure Number: IPCOM000083379D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Barson, F: AUTHOR

Abstract

The use of silicon nitride (Si(3)N(4)) in present emitter fabrication process is efficient of space in permitting base slot and emitter openings to be defined by a single mask, thus eliminating the need for alignment tolerance as would be required with separate masks for base and emitter. However, this is a process complication.

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Eliminating Si(3)N(4) for Emitter Masking

The use of silicon nitride (Si(3)N(4)) in present emitter fabrication process is efficient of space in permitting base slot and emitter openings to be defined by a single mask, thus eliminating the need for alignment tolerance as would be required with separate masks for base and emitter. However, this is a process complication.

In the present process, it is shown that the same geometries and alignment advantage can be had without the need for Si(3)N(4), by using oxides of suitable thicknesses and the same masks as are presently used with silicon nitride.

Following base diffusion, regrow a base oxide 5 thermally, but thicker than in the present process (about 3000 angstroms). No Si(3)N(4) is deposited. Open all contact holes (base slot and emitter) using the mask now used for etching these holes in the Si(3)N(4) layer. This produces the structure of Fig. 1.

Deposit by chemical vapor deposition, or regrow thermally, a relatively thin doped SiO(2) film 6, sufficient to mask the arsenic emitter diffusion. This might be approximately 1000 angstroms thick. There now exists sufficient difference in oxide thickness between that regrown in the base contact and emitter slots, over the adjacent base reoxidation, to mask with an oversize emitter photoresist pattern 7 and open the emitter slot 8 alone without removing the thicker oxide at its perimeter, as shown in Fig. 2.

The Nemitter is next diffused as usual, following photoresist...