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Improved Reliability for Al Cu Si Overlay Films

IP.com Disclosure Number: IPCOM000089048D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Reith, TM: AUTHOR

Abstract

In order to control Al-Si alloy penetration in shallow junction structures, Si is added to Al to pre-satisfy the solid solubility requirement. It is the practice in the art to deposit the Si as an overlay on the Al-Cu metallization. This method is not the most effective way of putting Si in Al-Cu, however, as Si must diffuse vertically through the Al-Cu land to the contact hole vicinity before it can act as an effective penetration suppressor.

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Improved Reliability for Al Cu Si Overlay Films

In order to control Al-Si alloy penetration in shallow junction structures, Si is added to Al to pre-satisfy the solid solubility requirement. It is the practice in the art to deposit the Si as an overlay on the Al-Cu metallization. This method is not the most effective way of putting Si in Al-Cu, however, as Si must diffuse vertically through the Al-Cu land to the contact hole vicinity before it can act as an effective penetration suppressor.

With chemically cleaned Si contacts, therefore, one has two competing processes: The Si overlay film must move through the Al-Cu film close to the bottom interface before the Al reduces the 10-20 angstroms of SiO(2) in the contact hole or else Si from the bulk wafer will begin diffusing up out of the contact. Because Si diffuses readily through Al at temperatures < 400 degrees C, but Al will not quickly reduce SiO(2) (Al SiO(2) ---> Al(2)O(3) Si) below 400 degrees C, by the time the native SiO(2) is reduced, significant amounts of Si (from the overlay) are close to the contact in most instances. However, if the heat-up time to sintering temperature is rapid, or if a small amount of Al(2)O(3) is present between the Al film and the Si overlay, sufficient Si from the overlay may not diffuse down to the contact before the native SiO(2) is reduced. A thin Al(2)O(3) layer between the Al and Si overlay can occur readily, even if vacuum is not broken between the two, if the substrates are hot, there is significant H(2)O vapor in the residual gas, or a long pause occurs betwe...