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Bipolar Transistor Substrate Contacts

IP.com Disclosure Number: IPCOM000051086D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Bhatia, HS: AUTHOR [+2]

Abstract

It is desirable to establish a substrate contact from the device surface for high density integrated circuits. The substrate contact may be made through the recessed silicon dioxide isolation, as shown in the drawing. This is accomplished by etching a hole through the silicon dioxide isolation region 10 using lithography and reactive ion etching to form the substantially vertical walls of the hole. The hole extends to the P/ / junction isolation region 9. A 2 x 2 micrometer hole would require a silicon dioxide isolation area of about 5 x 8 micrometers or more. Polysilicon layer 11 is then deposited to a suitable thickness, about 3000-5000 A, which is either P/+/ in situ doped or ion implanted to increase the layer's conductivity.

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Bipolar Transistor Substrate Contacts

It is desirable to establish a substrate contact from the device surface for high density integrated circuits. The substrate contact may be made through the recessed silicon dioxide isolation, as shown in the drawing. This is accomplished by etching a hole through the silicon dioxide isolation region 10 using lithography and reactive ion etching to form the substantially vertical walls of the hole. The hole extends to the P/ / junction isolation region 9. A 2 x 2 micrometer hole would require a silicon dioxide isolation area of about 5 x 8 micrometers or more. Polysilicon layer 11 is then deposited to a suitable thickness, about 3000-5000 A, which is either P/+/ in situ doped or ion implanted to increase the layer's conductivity.

The polysilicon is defined by thermal oxidation layer 12, lithography and reactive ion etching such that an area remains at the surface for metal contact
13. This process avoids planarity problems. A stipulation is necessary in the ground rules of any chip layout that no metal lines are to be placed over the hole.

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