Narrow Features in Metals at the Interfaces Between Different Etch Resists

The ability to create structures on length scales below 100 nm easily is a challenging feat. We report here a facile technique for the fabrication of such structures in gold (Au) with feature sizes smaller than 50 nm, utilizing two families of Au etch resists in conjunction. The first resist family consists of self-assembled monolayers (SAMs) of alkane thiols on Au, which provides substantial resistance against cyanide etch solutions. The second class consists of metals deposited on the surface of Au, which also provides similar resistance of the Au film to CN etchants but are not conducive for the formation of SAMs. Selective etching is initiated at the interface between these resists, proceeds into the Au layer and results in narrow trenches in Au not previously possible. Our protocol allows for the sequential removal of the different resists and thus permits the creation of Au surfaces with well-defined sub-50-nm etch patterns.