PDF (double-sided) - Physics Department, UCSB - University of ...

5.9 Top Wiring Layer – Part III
Since the insulator removal is the last etch step in the process, the above
mentioned shorting straps can now be removed. Due to the described charging
effect, they cannot be removed with the usual ICP etch. Instead, the lithography
is followed by a wet etch in which the sample is submerged into Transene-A, a
chemical that etches aluminum without creating a charge. The etch is followed
by the usual photo-resist strip.
5.10 Dicing
The main advantage of clean-room fabrication is that the stepper used during
photo-lithography can very quickly shoot almost 100 copies of our 0.25” × 0.25”
qubit design onto the 3” diameter wafer for each step. In all other fabrication
steps these 100 devices are processed in parallel at no extra effort. The only thing
left to do at the end is to cut the wafer into the desired dies. This is done on a
dicing saw which consists of a 200 µm-thick blade spinning at 30, 000 rpm that is
forced through the wafer. Since sapphire is the second hardest material known to
man, the blades cut with embedded particles made out of diamond, the hardest
material known to man. Before this, the wafer is protected with a fresh coat of
photo-resist. Once this coat is removed, the fabrication is complete.
103