Focused ion beam lithography using Al 2O 3 resist

Abstract

Fabrication technique of the x-ray mask using focused ion beams (FIBs) and rf-sputtered Al 2O 3 as an ion-beam resist is described. For deposition of Al 2O 3, the substrate temperature and the magnetic field strength near the target surface are optimized (380 °C and 9 mT), so that the etch rate ration in 100-°C H 3PO 4 of the as-deposited Al 2O 3 to the ion bombarded area at the dose of 2.8x10 14 cm -2 is increased, and the contrast ratio (γ value) is enhanced up to about 1.5. The sensitivity is about 1x10 14 cm -2. The 200-nm wide grooves are fabricated in 500-nm thick WN x layers using Al 2O 3 patterned with 50-keV Ga + FIB as a dry etching mask. The x-ray mask is fabricated using this technique, and the pattern transfer into PMMA is successfully carried out with synchroton radiation.