Lab Notes for FAFO Semiconductor Processes

Notes from experimenting with our equipment to slowly build up process knowledge for the various semiconductor steps.

Check the FAFO Semiconductor Processes project page for an overview.

This page is a lab notebook. It documents the work done in the lab and our thoughts, theories, and findings related to it. Everything you read here is work in progress and not final results. We believe it is best to have our lab notes out in the open, because it gives more detailed insight into what worked for us and what didn't. Of course you can also use this page to follow our progress!

Experimented with our coating process a bit more by attempting to chrome a piece of toilet paper. We scientifically mounted it on a JEOL sample stub and then attached it to an aluminum foil holder with copper tape:

For coating, we used new process parameters to see how well it works out.

Parameters: DC sputtering, 100W, Cr target, 10SCCM Ar, 2.6×10-2mbar, 30 seconds.

Coating worked great, here is the result:

Viewed it under the SEM. Here are a few shots we got:

Experiments with DC sputter deposition on our Edwards AUTO 306 Coating System of Cr in 'plasma process' mode and with MFC (mass flow controller).

Flow rerouted through mass flow controller (Ar line moved from needle valve to Ar MFC). Controlled over DE9 port by providing +/-15V and a 0-10V control signal. 10V == 100SCCM.

Process parameters:

1. Time: 1min to 4 min.
2. Power: 100W to 150W.
3. Ar pressure 2-5 * 10^-2 mbar.
4. Distance: ~30mm from lower part of holder to upper part of RF (!) sputter head.

Best results so far: (good balance between plasma size and speed) 1-2 min, 100W, 2.6 * 10^-2 mbar (~10SCCM). Higher Ar pressures limited plasma size considerably.

Process used:

1. Insert sample, press 'process' or 'cycle'.
2. Wait for machine to reach 5*10^-5 or lower.
3. Press 'process' and 'hold' shortly after. Ensure hold LED is blinking. Machine will display 0*10^-4 mbar as that's the lower bound of the (pirani?) gauge in process mode.
4. Open MFC to 10SCCM (1V on control line). Pressure should rise to 2.6*10^-2 mbar.
5. Reset the DC PSU interlock on the rack panel. INTLK on DC PSU should light on indicating the PSU is ready to start.
6. Start DC PSU at 100W. Wait for plasma to turn blue. Purge (with plasma off) for a few minutes first if line had air in it and plasma is continuously red/pink.
7. Swing sample into plasma, start 1 minute timer.
8. Stop DC PSU, close MFC. Pressure should drop back down to the 10^-4 - 10^-5 mbar regime.
9. Vent.

Tests were performed on Al foil with parameters written down. Test pieces are in the SEM sample box.

Consistency yet to be measured.

To be documented: Titanium Evap

Just for fun, placed a completely unprepared 3d-printed PETG part into the evap coater and coated it in aluminum: