Wafer bonding with patterned adhesive layers has been used
previously by a number of investigators; the topic has been
recently reviewed in [39]. The most common method in MEMS
fabrication is to spin coat a liquid polymer adhesive on a wafer.
However, due to presence of paraffin patterns on one of the COC
wafers, this conventional approach could not be used. Thus,
stamping was used to selectively deposit UV-cured adhesive
to the bonding surfaces of COC. A similar stamping approach
has been used previously to bond silicon [40], and recently to
bond glass wafers [41,42]. However, due to the hydrophobic
nature of COC, UV-cured adhesive did not spread and tended to form beads. A quick oxygen plasma treatment (50W, 30 s,
25 sccm) was used to make COC surface hydrophilic, permitting
the UV-cured adhesive to deposit evenly on the surface. The
COC substrate with microfluidic channel was also treated with
oxygen plasma to enhance adhesive transfer.