Adjustable sidewall slopes by electron-beam exposure layout

Abstract

Resist sidewall slopes frequently need to be adjusted in micro-and nanofabrication. In this paper, the authors present a straightforward approach to adjust sidewall slopes by using electron beam lithography and applying a background dose in addition to the feature dose. The underlying effect is attributed to an inhomogeneous energy deposition along the resist depth, for which a threedimensional point spread function is necessary to correctly describe the energy deposition in the resist even for large acceleration voltages and thin resist films. This enables adjacent features with different positive or different negative slopes within a single lithographic step. Corresponding experimental results obtained with the two positive tone resists poly(methyl methacrylate) and ZEP520A are shown, and their opposed sidewall behavior is explained. Moreover, a customized contrast curve is discussed that can, in theory, be used to achieve resist profiles with positive and negative slopes for the same resist. Therefore, a full range tuning on the same substrate becomes feasible. V

Beyond grayscale lithography: inherently three-dimensional patterning by Talbot effect

“…The latter case is instead a maskless method, which brings the advantage in terms of versatility; however, it requires a longer setup time to calibrate the process parameters. Nevertheless, it has been demonstrated that accurate control of the thickness, sidewall angle, and shrinkage of the resist in maskless grayscale lithography is possible [10].…”

Shaping the Color and Angular Appearance of Plasmonic Metasurfaces with Tailored Disorder

“…8 Disorder due to fabrication errors influences the optical properties of photonic crystals, 9 and nanostructures produced using electron-beam lithography typically suffer from structural disorder due to alignment errors and the proximity effect. 10,11 On the other hand, exploiting the effects of structural disorder has also brought forward applications such as photon trapping and localization of surface plasmon polaritons 12−14 and on-chip spectrometry. 15,16 Most notably, disordered arrangements of nanostructures have been used to determine the far-field optical properties of metasurfaces, with applications in structural colors 17−20 and enhanced light collection in thin-film solar cells.…”

“…Disorder-induced light scattering has brought forward random lasers, disordered opaque media have been used as programmable optical circuits in combination with wavefront shaping, − and disorder-engineered metasurfaces have in turn been employed for wavefront shaping and high-resolution microscopy . Disorder due to fabrication errors influences the optical properties of photonic crystals, and nanostructures produced using electron-beam lithography typically suffer from structural disorder due to alignment errors and the proximity effect. , On the other hand, exploiting the effects of structural disorder has also brought forward applications such as photon trapping and localization of surface plasmon polaritons − and on-chip spectrometry. , Most notably, disordered arrangements of nanostructures have been used to determine the far-field optical properties of metasurfaces, with applications in structural colors − and enhanced light collection in thin-film solar cells. − Another application of tailored disorder in nanostructure arrangements is the suppression of grating modes to achieve an angle-independent response , or, in the opposite case, the realization of metasurfaces with a tailored, ultrahigh angular selectivity …”