11 Device side deep silicon etch

a. AMI clean followed by Nordson March PX-250 asher to clear organic material
from device side of wafer.
b. Attach wafer to handle wafer. Handle wafer should have aluminum oxide or
silicon oxide deposited to prevent etching into them.
i. Piranha/AMI clean handle wafer
ii. Use quartz wafer with kapton tape at three points on edge of wafer to
ensure device wafer and quartz wafer do not make contact. Tape quartz
wafer to device wafer with device wafer back side exposed.
iii. Spin AZ 5209E onto back side of device wafer with quartz wafer
interfacing with the chuck. Can use manual spinner, 500 RPM for 5 s
and 800 RPM for 30 s. Immediately detach device wafer from quartz
wafer and place onto handle wafer.
iv. Secure two wafers by pressing down with tweezers along perimeter and
using clean wipe and something with large surface area to gently press
them together.
v. Bake at around 100 ⁰C for 1 min.
c. Plasma-Therm: VERSALINE DSE Cycles consist of loops through steps 3-5. Run 200 cycles of recipe in each
segment with 5 min of delay time in between. Etch a total of 800 cycles.
Notes: After each O2 clean, chamber is hot and should be allowed to cool prior
to first etching segment. Backside helium pressure and flow must be at
reasonable values or else it is indication of thermal issues. With two wafers
being clamped the backside helium pressure set point may need to be adjusted.
d. Soak device wafer in acetone or Remover PG if stubborn until separated from
handle wafer.
e. Spin on protective PR layer using AZ 5209E recipe on device side and dice
wafer into 16 smaller pieces using dicing saw.
f. AMI clean followed by Nordson March PX-250 asher for piece to be etched.
g. Clean handle wafer followed by a dehydration bake.
h. AZ 5209E recipe on handle wafer.
i. Attach device wafer piece onto center area of handle wafer. Clean all PR around
the piece.
j. Plasma-Therm: VERSALINE DSE
Same recipe as before. 50 cycles each segment with 3-5 min of delay in between
each. Etch until total cycles reach 1600, including cycles etched as whole wafer.
k. Soak in acetone/Remover PG until piece is separated from handle wafer.