Browse Prior Art Database

Contact Hole Etching Process

IP.com Disclosure Number: IPCOM000037636D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Pearson, DJ: AUTHOR [+2]

Abstract

Contact holes of varying depths can be more reliably etched through a planarized passivation layer to submicron devices by depositing Low Temperature Oxide (LTO) and a magnesium oxide layer over the surfaces of the devices before the passivation layer is formed.

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Contact Hole Etching Process

Contact holes of varying depths can be more reliably etched through a planarized passivation layer to submicron devices by depositing Low Temperature Oxide (LTO) and a magnesium oxide layer over the surfaces of the devices before the passivation layer is formed.

Referring to the figure, the depth of contact holes 1 from source/drain 2 and holes 3 from recessed oxide areas 4 to the surface 5 of passivation layer 6 varies widely and makes severe demands on reactive ion etching. This criticality is relieved by forming LTO 7 at a thickness of 100 nm over the device followed by evaporated or sputtered layer 8 of magnesium oxide 100 nm thick before passivation insulator 6 is formed. Contact holes 1 and 3 are etched in the passivation insulator 6 by reactive ion etching using the magnesium oxide 8 as an etch stop. Thereafter, magnesium oxide 8 is selectively wet etched with ammonium oxalate solution. This does not reduce the thickness of layer 7, leaving it the same thickness over the silicide 4 and source or drain 2. Reactive ion etching of the LTO becomes simpler. Any undercutting of the magnesium oxide is refilled by subsequent chemical vapor deposition of tungsten plugs.

The magnesium oxide layer can be placed up to 300 nm from the polycide or source/drain without causing etching problems. At a greater distance, the electrical properties of the oxide become less important to the field threshold voltage.

Disclosed anonymously.

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