micro-porous lift-off TEOS
For this experiment, 3um diameter pores were created using SimPore’s mask. Reactive Ion Etching was used to form the pores in the SiN. Both 25nm and 150nm TEOS oxides were used. An SU8 Structure of 10um lines with 100um square windows was chosen. A sample was placed in 10:1 BOE w/ surfactant for various amounts of time, then imaged to determine the effect of the BOE, and to achieve lift-off.
The results:
25nm TEOS could not be lifted off, however the 150nm was able to be lifted off at 30,35, and 40 minutes in BOE.
Above: 20 minutes in BOE, 25nm TEOS
Below: 50 minutes in BOE, 25nm TEOS
Above: 45 minutes in BOE, 150nm TEOS at 2.5x mag.
Below (2): 45 minutes in BOE, 150nm TEOS at 20x
Below: Back side of 45min in BOE sample at 50x mag.
SU8 backside w/out uporous SiN:
Based on these results, I have generated the following theoretical side profile (see below). I believe the SU8 is adhering to the silicon substrate in the 25nm TEOS samples, but not in the 150nm due to the over etch during RIE.
In the pair of pictures labeled 45min BOE, 150 nm TEOS, why is the membrane wrinkled in one image, but flat in the other? Is one dry, one wet?
You should update the post with SiN thickness at the top.
In general – does it seem robust? How large were the membrane pieces that you created?