Browse Prior Art Database

Transistor Design for Integrated Circuits

IP.com Disclosure Number: IPCOM000075352D
Original Publication Date: 1971-Sep-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Baker, TH: AUTHOR [+3]

Abstract

In planar integrated circuits wherein the surface metallurgy contacts the emitter regions through contact holes in the silicon dioxide passivation layer over the integrated circuit surface, there is a possibility that the metallurgy deposited in the contact hole will not completely fill the hole. Such a structure is shown in Fig. 1 comprising an emitter 10 surrounded by base region 11. The surface of the substrate is covered by silicon dioxide layer 12 having contact hole 13 formed therein. Surface metallurgy 14 is deposited within contact hole 13 to make the emitter contact.

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Transistor Design for Integrated Circuits

In planar integrated circuits wherein the surface metallurgy contacts the emitter regions through contact holes in the silicon dioxide passivation layer over the integrated circuit surface, there is a possibility that the metallurgy deposited in the contact hole will not completely fill the hole. Such a structure is shown in Fig. 1 comprising an emitter 10 surrounded by base region 11. The surface of the substrate is covered by silicon dioxide layer 12 having contact hole 13 formed therein. Surface metallurgy 14 is deposited within contact hole 13 to make the emitter contact.

While the surface metallurgy 14 overlaps shoulder 15 of the silicon dioxide layer, it fails to overlap shoulder 16 due to a less than perfect alignment during fabrication. Where such a failure occurs, the contact will usually be sufficiently adequate so that the integrated circuit chip will pass all functional tests. However, during the life-time of the device in an operational environment, e.g. a computer, there is a tendency for electromigration of the metal 17 to undercut shoulder 16, and to eventually short-out the emitter base junction 18.

This problem is solved by insuring that there is a sufficient overlap in the contact metallurgy to provide that even when there is a misalignment of such contact metallurgy within acceptable tolerances, there will be no such exposure. Fig. 2 shows such a structure wherein contact metallurgy 14 is sufficiently...