For my tantalum pentoxide thin film integrated capacitors, I need to etch the tantalum and tantalum pentoxide layers with pure SF6 plasma. While etching these layers copper will also be exposed to the plasma. Does anyone know if the copper will be etched too (and if so at which etch rates) and if it reacts in a form so that the copper will no longer be conducting?
When etching tantalum and tantalum pentoxide layers with pure SF6 plasma, copper will also be exposed to the plasma. Copper is known to be etched by SF6 plasma, but the etch rate depends on various factors, such as plasma power, pressure, and gas flow rate. The etch rate of copper in SF6 plasma can range from 0.1 to 1.5 μm/min.
Copper can react with SF6 plasma to form copper fluoride (CuF2) and copper sulfide (CuS). Copper fluoride is an insulator and can prevent copper from conducting electricity. However, the formation of copper fluoride can be suppressed by adding oxygen to the SF6 plasma.
It is important to note that the etch rate of copper in SF6 plasma is much slower than that of tantalum and tantalum pentoxide. Therefore, it is possible to selectively etch tantalum and tantalum pentoxide without significantly etching copper by optimizing the etch conditions.
More at:
CP2014_Filipovic_5.pdf (tuwien.ac.at)
Use of Copper Mask in SF6/O2 Chemistry in PT-MTL | Stanford Nanofabrication Facility
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