  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.
