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.
We consider an optical system in which the optical vortex moves inside the focused Gaussian beam. The vortex movement is due to the vortex lens inserted in front of the focusing objective. We gradually shift the vortex lens along the x-axis which is perpendicular to the axis of laser beam propagation (z-axis). This causes that in the image plane vortex moves along a straight line but the line inclination depends on the position of the observation plane. There is a characteristic position of the observation plane, in which the vortex trajectory is perpendicular to the vortex plate shift. We call this plane a critical plane. The critical plane is sensitive to small phase variations which can be introduce by a transparent sample. We propose a way of retrieving the phase profile (at the critical plane) of such a beam. Our procedure is based on the Fourier transform phase demodulation method. We also investigate how the system reacts to the known phase variations introduced into the critical plane.
Paper presents research on the sub-micron gate, AlGaN /GaN HEMT type transistors, fabrication by e-beam lithography
and lift-off technique. The impact of the electron beam on the resists layer and the substrate was analyzed by MC method
in Casino v3.2 software. The influence of technological process parameters on the metal structures resolution and quality
for paths 100 nm, 300 nm and 500 nm wide and 20 μm long was studied. Qualitative simulation correspondences to the
conducted experiments were obtained.
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