The challenge for depositing paraffin was to deposit a uniform
film on a COC wafer before the molten paraffin solidified during
spin coating. When spin coating paraffin, heat is transferred by conduction through the spin chuck and convection in air due
to rotation. In our previous work [26], paraffin was deposited
on glass wafers 18mm in diameter and 170m in thickness.
Heat transfer from paraffin through thin glass to a bulky aluminum
spin chuck was rapid, resulting in spin coating times on
the order of several seconds—substantially shorter than traditionally
used when working with photoresist. In this work, COC
wafers are 1mm thick and do not transfer heat as rapidly (thermal
conductivity of COC at room temperature is approximately
0.16 W/mK [37] versus 1.35 W/mK for glass [38]).