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Integrated Circuits having Reduced Parasitic Thyratron Effects

IP.com Disclosure Number: IPCOM000075358D
Original Publication Date: 1971-Sep-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Hadamard, GJ: AUTHOR

Abstract

In the manufacture of monolithic microcircuits in which a plurality of components including resistors are formed in electrically isolated pockets on the same semiconductor chip, four successive zones of opposite conductivity type exist which provide unwanted parasitic thyratron operations under certain biasing conditions. The biasing conditions giving rise to unwanted thyratron operations include those involved in the testing of the completed microcircuits. It is desirable, therefore, to suppress such parasitic effect so that accurate and reliable test data can be obtained on the desired microcircuit.

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Integrated Circuits having Reduced Parasitic Thyratron Effects

In the manufacture of monolithic microcircuits in which a plurality of components including resistors are formed in electrically isolated pockets on the same semiconductor chip, four successive zones of opposite conductivity type exist which provide unwanted parasitic thyratron operations under certain biasing conditions. The biasing conditions giving rise to unwanted thyratron operations include those involved in the testing of the completed microcircuits. It is desirable, therefore, to suppress such parasitic effect so that accurate and reliable test data can be obtained on the desired microcircuit.

Drawing A is a cross-sectional view of a portion of a typical microcircuit in which parasitic thyratron effect may be present. The device comprises a P- conductivity substrate 1 and an N epitaxial layer 2, which has been divided into electrically isolated pockets 20 and 21 by P+ isolation diffusion 3. A P diffusion 4 is made in one of the isolated pockets to form a resistor between ohmic contacts 5 and 6. Ohmic contacts 7 and 8 are placed in the other isolated pocket to form a second resistor having a buried N+ layer 9. An additional ohmic contact 10 is made to the N epitaxial layer in the first isolated pocket.

Buried layer 9, isolation wall 3, epitaxial layer 2 of pocket 21 and P diffusion 4 together constitute four successive layers of opposite conductivity type, which function as a thyratron under appropriate biasing conditions. Drawing B represents the functionally equivalen...