Study of ion charging effect to improve reactive-ion-etching profile of PbSe grating structures

The fabrication of narrow-slot Lead-Selenide (PbSe) gratings is critical for advancing mid-infrared (MIR) device technologies, for applications in spectroscopy, thermal imaging, and environmental monitoring. The primary challenge to achieve this goal is the increased irregularity and reactive ion etching (RIE) lag in etched profiles as slot width decreases. This research highlights the charging effect, attributed to accumulated charge on non-conductive photoresist, as the main cause of these irregularities. Introducing a conductive copper layer neutralizes this charge, enabling successful etching of gratings with significantly improved profiles and slot widths down to 0.7 μm. This solution, offering improved MIR device sensitivity and resolution, and opening new avenues for scientific and practical applications in fields ranging from security to healthcare.