**2.4 Etching processing and pattern transferring**

After exposure, the samples with latent patterns in SAM were taken out from the vacuum chamber and rapidly dipped into an etching solution in which a magnetic bar was used for stirring, and were etched for 5~60min at room temperature in an aqueous solution of 0.1M KOH, rinsed by deionized water, and then dried in air. By this single step KOH etching process, the latent image formed in SAM by He\*-MAB passing through a stencil was directly transferred into the underlaying Si substrate (as described in (VI) and (VII) in Scheme 1).

For the wet etching of Si substrate in KOH solution, the anisotropy of etching rate of silicon have been studied in detail over the passed 20 years. Especially, in the case of the photolithography in MEMS and IC industry, the anisotropy of etching rate of silicon has been investigated completely, and the anisotropy can induce obvious differences of the spatial resolution of patterning of Si along different crystal orientation. The etching rates for the silicon wafer in the KOH solution are known to depend strongly on its orientation (Si+2OH⎯+2H2O→SiO2(OH)22 <sup>⎯</sup>+2H2(g); etching ratio: {110}>{100}>>{111}) [33]. In our experiments, the anisotropic etching process of silicon occurred in the same way, and strongly affected the patterning results including edge step resolution. The sharpest step edge resolution was only 41nm with 1 pixel and the average step edge resolution was around 100 nm.
