Reliable observation of large leakage-current reduction of thin Si O ₂ induced by phonon-energy-coupling enhancement: Problems and solution

The problems encountered in the observation of large leakage-current reduction of thin Si O₂ due to enhanced phonon-energy coupling were thoroughly analyzed. A lithographic method based on bilayer resists (SU-8 and Shipley S1813) and an organic developer (SU-8 developer) was developed to fabricate Ni-gate metal-oxide-semiconductor (MOS) capacitors. After development, an undercut profile of the bilayer resists was clearly demonstrated. A key step, thorough deionized water rinse after a quick isopropyl alcohol rinse during resist patterning, is critical to obtain well-defined Ni electrodes reproducibly. Experimental current-voltage and capacitance-voltage (C-V) curves of the Ni-gate MOS capacitors, together with the C-V curves simulated using the Berkeley Quantum simulator, demonstrate that a large leakage-current reduction (∼100×) can be reliably and reproducibly achieved on thin Si O ₂ (∼23 Å) after proper rapid thermal processing.