Anti-corrosion etch process for etching metal interconnections e

Details Anti-corrosion etch process for etching metal interconnections e Anti-corrosion etch process for etching metal interconnections e

1996-07-17

1998-07-07

Everhart, Caridad

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

438688, 438720, 438725, H01L 2131

Patent

active

057768323

ABSTRACT:
A method for anti-corrosion etching of metal interconnections, comprised in part of an aluminum layer, is achieved. The metal lines form self-aligned contacts (SAC) in contact openings in a polysilicon/metal dielectric (PMD) layer to a patterned underlying polysilicon layer. The method involves performing an oxygen ashing step in the same etching chamber immediately after etching the aluminum lines in a halogen gas, such as BCl.sub.3 and Cl.sub.2. This method using oxygen ashing avoids the use of the more traditional passivation gases CHF.sub.3 and CF.sub.4 which can overetch the polysilicon exposed in the SAC process that would cause electrical opens. And further, it avoids the formation of a polymer residue which is difficult to remove. The oxygen treatment reduces the Cl.sub.2 on the sidewalls of the Al lines, and also removes portions of the photoresist mask material containing Cl.sub.2. It is also easier to remove the remaining photoresist in a solvent stripping process. SEM measurements of the etch bias of the photoresist critical dimension also indicate the formation of a redeposition on the Al sidewalls which further protects the Al from corrosion when the wafers are removed from the etch chamber and are exposed to moisture.

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S. Wolf, Silicon Processing for the VLSI Era: vol. 2 (1990) Lattice Press, Calif. pp. 124-131.

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