Microfabrication
Mcirofabrication is both technique and art.
In Feb. 2020, Dr. Neal Hall showed Xiaoyu around MER's cleanroom. Told the stories about how to use microfabrication to build MEMS sensors. At that time, Xiaoyu was triggered by this kind of interdisplincniry work. The tour of the cleanroom is one of the major reasons that Xiaoyu rejected PSU and went to UT.
In Dec. 2020, Xiaoyu was first trained by Yoonho to do sputter, photolithography, and lift-off. Xiaoyu appreciated Yoonho's and Anna's help.
In the summer of 2021, Xiaoyu individually built CMUTs in MER's cleanroom. Although the CMUTs weren't successful, Xiaoyu learned and experienced fab a lot.
During the spring of 2023, Xiaoyu restarts the MEMS fab. Have a bunch of feelings and thoughts. Write them down for future reference.
-- 04/05/2023 Xiaoyu Niu
Adding Materials
Al2O3
ALD Banerjee (ALDCambridge Nano Tech Savannah TM 200) manual
Al2O3 one side deposition with carrier wafer and clamps
Al2O3 one side deposition with tapMRL Furnace
Before slide the wafer out you need some time to cool it down.
1 - 5 wafers: minimum 15 minutes cool down
6 - 12 wafers: minimum 20 minutes cool down
>13 wafers: minimum 25 minutes cool downMRL POCl3 furnace
recipe: POCL840 C for 30 minutes usually faults once before working properlyMRL Annealing Furnace (doped)
recipe: 850 Ann for 40 minutes
Patterning
Reducing Materials
tools
Silicon
Photoresist
Oxford 80 RIE etcher
Piranha clean - remove organic debris
Spin Rinse Dryer (SRD)
After Piranha clean, usually use this tool to dry wafers. The default recipe is "recipe 6", which takes a couple of minutes. If the setting is not this recipe, press "recipe" button to switch to this recipe.
Manaul: this tool is easy to use. (1) Load your wafers (2) Press "start" (3) Wait a few minutes
Al2O3
SiO2
BOE etch - etch SiO2 and Si3N4
C14, C16 Hoods are allowed to do this process. Yoonho prefers H14 to run this process.
KOH etch Hood is not allowed to do this process.
Etch rate = 90 nm/min
Plasma dry etch
oxford 80: DK has the recipe with about 30 nm / min rate.
Others:
Measurements
Packaging Devices
Others
recycle empty bottle
Acid empty bottle
(1) Wear Personal Protective Equipment (PPE) to transfer the bottles from hoods to thermal service aisle.
(2) Wear PPE, load the bottle to the rinse foundation, and open rinse valve for 5 seconds. Close the water valve. Pull up the bottle. This process is taken into account one-time rinse. Do this rinse process for 3 times.
(3) label the bottle. Please contact Ricardo if you found the label is run out of.Non-acid empty bottle
Leave in the recycle bin.
recycle wipes
Wipes used in both solvent hood and furnace should be recycled in solvent hood if they are relatively clean. Otherwise, Ricardo may restrict your access.
Resources
FNT cleanroom FBS (reserve system)
Xiaoyu's black wafer box
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7 SOI wafer taken from #38 box
doping test. Finish two N-doping processes.
8 SSP wafer taken from #48 box
doping test. Finish two N-doping processes.
9 Geophotonic dummy SSP wafer
top is covered by PR. PR is patterned.
10 Geophotonic wafer with SiN waveguides
top patterning is finished. PR is stripped.
bottom is patterned and covered by ~220 nm Al2O3 and SU8.
next step: dice the wafer
next step: backside DSE
11 Geophotonic dummy SSP wafer
top and bottom are covered by SU8. PRs are patterned.
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23 SSP dummy wafer 170 um dia CMUTs
24 SOI wafer taken from #38 box for 170 um dia CMUTs without doping process
25 SOI wafer taken from #38 box for 170 um dia CMUTs with doping process