Chrome mask fabrication on Al2O3 substrate for new generation devices based on AlGaN/GaN heterostructure

The goal of the conducted work was to fabricate chrome masks on Al2O3 substrates, which could be successfully applied to UV and DUV lithography. The technique is based on electron beam lithography and wet chrome etching in an ceric ammonium nitrate solution. The main advantage of the proposed fabrication method is a major decrease in exposition time due to more effective usage of electron energy. We will demonstrate the use of low electron energy exposition methods with PMMA/MA resist with applied doses of a few μC/cm2. To the best of the author’s knowledge, sapphire substrates have not been previously used in photomasks fabrication. So far, full photomasks sets based on Al2O3 substrates have been manufactured and applied to fabricate the pilot series of acoustic transducers in the AlGaN/GaN heterostructure for piezotronics applications.