The Improved Self-assembled Monolayer of Octadecyltrichlorosilane as Positive Resist for Patterning Silicon Surface by Metastable Helium Atom Beam Lithography

We utilized a beam of helium atoms in a metastable excited state to expose an improved ultrathin self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) acted as positive resist grown directly on silicon wafer substrate. The metastable helium beam incident on the samples was patterned with a mask, which was placed in gentle contact with the substrate surface. A three-step wet-chemical etching process was successfully developed to transfer mask patterns into the underlying silicon substrate. Only positive patterns were fabricated on silicon surface by using the improved positive resist and controlling of the exposure dosage and the etching time. The sizes of positive patterns on silicon were successfully decreased from micrometer scale to 100 nm.