Scalable fabrication of hemispherical solid immersion lenses in silicon carbide through grayscale hard-mask lithography

TL;DR

This paper presents a scalable, CMOS-compatible method for fabricating high-aspect-ratio hemispherical solid immersion lenses in silicon carbide using grayscale lithography and hard-mask techniques, offering a low-cost alternative to focused ion beam milling.

Contribution

It introduces a novel fabrication protocol combining grayscale lithography and hard-mask techniques for creating hemispherical lenses in silicon carbide, scalable and compatible with industrial processes.

Findings

Lenses of 5 μm radius successfully fabricated in silicon carbide.

The process is highly scalable and compatible with CMOS technology.

Device aspect ratios can be tuned post-patterning by controlling etch chemistry.

Abstract

Grayscale lithography allows the creation of micrometer-scale features with spatially-controlled height in a process that is fully compatible with standard lithography. Here, solid immersion lenses are demonstrated in silicon carbide using a novel fabrication protocol combining grayscale lithography and hard-mask techniques to allow nearly hemispherical lenses of 5 $\mu$m radius to be etched into the substrate. The technique is highly scalable and compatible with CMOS technology, and device aspect ratios can be tuned after resist patterning by controlling the chemistry of the subsequent dry etch. These results provide a low-cost, high-throughput and industrially-relevant alternative to focused ion beam milling for the creation of high-aspect-ratio, rounded microstructures.