Micromachining techniques at terahertz frequencies

摘要

Abstract: In this paper we have characterized the refractive indexed and absorption coefficient of negative photoresist NANO XP SU-8 from 0.1-1.6 THz using THz time-domain spectroscopy. Over the measured frequency range it was found that the refractive index is a relatively flat function of frequency, decreasing from 1.8 to 1.7. The value of absorption coefficient is seen to increase in a line fashion over the given frequency range, being 25 cm$+$MIN@1$/ at 1 THz. From this data we have extracted functions of dielectric constant and dielectric loss tangent versus frequency, quantities which will be of use for future THz circuit design. In addition to these measurements, we have demonstrated two novel applications of SU-8. First, we have fabricated membrane-like features by using a multi-exposure photolithographic technique on a single layer of SU-8, and second we have utilized a thin layer of SU-8 as a patternable adhesion layer as part of a semiconductor epitaxial lift-off process designed to transfer III-V semiconductor epitaxial layers onto lower loss host substrates. !12