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Contact Holes With Slotted Conductor for Eliminating Aluminum Spikes

IP.com Disclosure Number: IPCOM000043807D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Battjany, S: AUTHOR [+4]

Abstract

It is proposed that the design of the first metallization of chips be modified such that the contact holes are covered only partly with aluminum and the air can reach the aluminum and silicon surfaces for their passivation. Silicon oxide/silicon nitride double layers are being used on a large scale for passivating silicon wafer surfaces, because their isolating properties are superior to those of single layers. However, such double layers have the disadvantage that the undercut occurring during the wet etching of the contact holes may lead to the formation of a nitride overhang and a cavity in the bottom layer.

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Contact Holes With Slotted Conductor for Eliminating Aluminum Spikes

It is proposed that the design of the first metallization of chips be modified such that the contact holes are covered only partly with aluminum and the air can reach the aluminum and silicon surfaces for their passivation. Silicon oxide/silicon nitride double layers are being used on a large scale for passivating silicon wafer surfaces, because their isolating properties are superior to those of single layers. However, such double layers have the disadvantage that the undercut occurring during the wet etching of the contact holes may lead to the formation of a nitride overhang and a cavity in the bottom layer. As aluminum is deposited in a vacuum, the cavity sealed by the evaporated Al remains in a vacuum even after removal of the wafer from the evaporation system, and the surfaces of the cavity remain oxide-free and reactive (illustration, left-hand side), favoring the formation of Al spikes during the subsequent sintering step. At partly covered contact holes, in which the cavity is open underneath the nitride overhang, no Al spikes were formed. It is assumed that air and other process chemicals, which have access to all critical Al and silicon surfaces of such an embodiment, lead to the passivation of these surfaces, thus preventing the formation of Al spikes during sintering. Therefore, it would be favorable for all processes using contact holes etched through double layers to provide the c...