In this article Si substrates protected by Shipley 1827 and Au masks are sputtered with electrosprayed nanodroplets to produce microscale structures. Silicon is used as a benchmark to assess the effect of the physical sputtering of nanodroplets on more interesting chemically inert materials such as SiC and GaN.
The use of Shipley 1827 as a patterning mask provides a virtually infinite etching selectivity between substrate and photoresist at the cost of non-perpendicular wall profiles and debris redeposition. After 60 minutes of processing the target at a sputtering rate of 244 nm/min, a fraction of the sputtered material deposits back on the substrate forming a protective layer that stops any further sputtering.
In a second set of experiments the selectivity between Si and Au to be used as a potential mask is studied. The maximum selectivity is 64.17, and is obtained at an etching rate of 385 nm/min. An increase of the etching rate produces a sharp drop on the selectivity between Au and Si.