Synergy of cold development and electron-beam exposure for Si nanotip patterning in quantum-electronic devices

We demonstrated an effective method for lithographic patterning of a fanout-shaped Si nanotip array with nanometer-scale feature size/pitch by using a combination of overdose exposure, cold development, and layout design. We optimized process conditions of electron-beam exposure onto poly(methyl methacrylate) resist and methyl isobutyl ketone development temperature (10 to −5 °C) to produce dense Si nanotips with large gradient fanout patterns. A circular array of Si nanotips with a minimum feature size/pitch of 15/30 nm with a high degree of pattern fidelity, uniformity, and reproducibility were demonstrated. Based on the platform of the Si fanout-shaped nanotip array, we have successfully produced an array of self-organized germanium quantum-dots/Si₃N₄ barriers, which are self-aligned with Si nanotips as coupling barriers or electrodes for implementing advanced quantum-electronic devices.