Fabrication of 340-GHz Folded Waveguides Using KMPR Photoresist

This letter presents the fabrication of 340-GHz copper folded waveguides (FWGs) using the UV-LIGA method. During the process, KMPR photoresist was employed instead of SU-8 due to its easy removability after electroforming. KMPR patterns with a sidewall height of 300
$\mu\hbox{m}$
and a trench width of 100
$\mu\hbox{m}$
were achieved repeatedly under one single-spin deposition and optimized processing conditions, such as UV exposure dose and KMPR bake temperature and time. The dimensional accuracies of the wide side (500
$\mu\hbox{m}$
) and narrow side (100
$\mu\hbox{m}$
) of the copper FWGs were found to be
$\leqslant \hbox{6}$
and
$\leqslant \hbox{2}\ \mu\hbox{m}$
, respectively, and the sidewall surface roughness was about 44 nm, with a profile of about 90
$^{\circ}$
.