Optimized metal etch process to enable the use of aluminum plugs

A method of making a semiconductor device having aluminum alloy lines over aluminum alloy plugs without forming plug recesses comprising:

• forming a first metal layer on a substrate;
• forming a dielectric layer over the first metal layer;
• defining a via in the dielectric layer of sufficient depth to expose the first metal layer;
• depositing a barrier layer substantially conforming to the via;
• forming an aluminum alloy plug in the via and;
• forming a second metal layer over the aluminum alloy plug;
• etching the second metal layer with a first etch chemistry;
• changing to a second etch chemistry, wherein the etch rates of the second metal layer, the exposed dielectric layer, and the barrier layer, as provided by the second etch chemistry are approximately equal;
• and
• over etching the second metal layer using the second etch chemistry.

A method of making a semiconductor device having aluminum alloy lines over aluminum alloy plugs without forming plug recesses comprising:

• forming a first metal layer;
• forming a dielectric layer over the first metal layer;
• defining a via in the dielectric layer of sufficient depth to expose the first metal layer;
• forming an aluminum alloy plug in the via;
• forming a second metal layer;
• etching the second metal layer with a first etch chemistry selected from the group of HCl, Cl2 and BCl3;
• changing the etch chemistry to a second etch chemistry by selecting the etch chemistry from the group of SF6 and CF4, CHF3, C2F6, wherein the etch rates of the second metal layer and the exposed dielectric layer, as provided by the second etch chemistry are approximately equal;
• and
• over-etching the second metal layer with the second etch chemistry such that a portion of the aluminum plug not covered by the second metal layer is etched substantially flush with the surrounding dielectric.

A method of etching a semiconductor device having aluminum alloy lines over aluminum alloy plugs surrounded by a dielectric layer and electrically coupled to a lower level metal layer, comprising:

• placing one or more wafers inside a plasma etch reactor chamber;
• reducing the chamber pressure until vacuum is achieved;
• performing a bulk etch of the aluminum alloy lines and aluminum alloy plugs;
• performing an endpoint etch of the aluminum alloy lines and aluminum;
• performing a residue etch of the aluminum alloy lines and aluminum plugs;
• performing an over-etch of the aluminum alloy lines and aluminum alloy plugs wherein the etch rates of the aluminum alloy lines and the dielectric layer, as provided by the over etch are approximately equal;
• and
• breaking vacuum so that wafers can be removed from the plasma etch reactor chamber.

A method of etching a semiconductor device having aluminum alloy lines over aluminum alloy plugs surrounded by a dielectric layer and a barrier layer and electrically coupled to a lower level metal layer, comprising:

• placing one or more wafers inside a plasma etch reactor chamber;
• reducing the chamber pressure until vacuum is achieved;
• performing a bulk etch of the aluminum alloy lines and aluminum alloy plugs;
• performing an endpoint etch of the aluminum alloy lines and aluminum;
• performing a residue etch of the aluminum alloy lines and aluminum plugs;
• performing an over etch of the aluminum alloy lines and aluminum alloy plugs wherein the etch rates of the aluminum alloy lines, the dielectric layer and the barrier layer, as provided by the over etch are approximately equal;
• and
• breaking vacuum so that wafers can be removed from the plasma etch reactor chamber.

A method of etching a semiconductor device after the formation of aluminum alloy lines over aluminum alloy plugs coupled to a lower level metal layer without forming plug recesses comprising:

• placing one or more wafers inside a plasma etch reactor chamber;
• reducing the chamber pressure until vacuum is achieved;
• introducing BCl3 and Cl2 at a flow rate of about 30 to 40 sccm for each species and maintaining chamber pressure to a range about 9 to 12 mT for about 30 seconds;
• performing a TiN and AlCu bulk etch for about 20 to 28 seconds at an RF-Top Power between 300 and 415 watts and an RF-Bottom Power between 85 to 115 watts;
• performing an AlCu endpoint etch for about 42 to 58 seconds at an RF Top Power between 300 and 415 watts and an RF Bottom Power between 190 to 260 watts until a trigger value of indicating AlCu clearing is reached;
• changing the BCl3 and Cl2 flow rates to a range 43 to 58 sccm and to a range of 25 to 35 sccm, respectively and performing a copper residue etch for about 3 to 7 seconds;
• introducing SF6 at a flow rate of 17 to 23 sccm and performing a Ti+ 1:1:1 over-etch for about 43 to 58 seconds;
• and
• shutting off the flow of etchant gases and allowing chamber to pump down to-vacuum;
• and
• breaking vacuum so that wafers can be removed from the plasma etch reactor chamber.