Np-Au Precursor Alloy Fabrication

From LPDwiki

Day before sputtering

Sample Preparation

1. Prepare a large petri-dish with a tex-wipe bottom for temporary storage of the cleaned glass slides.

2. Piranha clean 12 mm diameter glass slides (Ted-Pella) in a 3:1 dilution of H2SO4 and H2O2 for 15 minutes.

3. After cleaning, move sample (in boats) to DI water.

4. Individually (with tweezers) rinse off each sample and dry individually under nitrogen flow.

5. Place the clean glass slide in the previously prepared petri-dish.

6. Repeat until enough glass slides have been cleaned to fill up the number of empty stencil spots.

Preparing PDMS Stencil

1. PDMS stencil can be laser cut using the a pulsed cutting laser according to an AutoCAD file.

  • Optional: If the PDMS stencil is old or has excessive dust on it please clean it by peeling off both protective layers and immersing in 70% EtOH for ~5 minutes and then drying under nitrogen flow.

2. Place this stencil in a clean petri-dish with a text-wipe on the bottom (it will stick to the dish if you do not do this!).

Sample Mounting

1. Carefully place glass slides directly over all the holes in the PDMS stencil (try to make the centered as much as possible).

2. Upon placing the slide on much of it should adhere, but press on it a few times lightly with the tweezer flat side to ensure the slides are adhered.

3. Once all slides have been mounted to the PDMS stencil carefully flip it over and place it in a clean petri-dish.

4. If ready to deposit you can then tape this stencil to a large wafer (used for sputtering) with kapton tape (should be some in the lockers).

5. If not ready to deposit parafilm the edge of the petri-dish and place in a safe dry place.

Sputter Preparation

Note: You need the appropriate training for this section.

1. Vent the main chamber of the sputter.

2. Replace the targets:

  • Ag in Gun 2
  • Au in Gun 3
  • Cr in Gun 5

3. Vacuum out the chamber just to pick up any loose flakes of metal.

4. Pump down the sputter.

5. Run a test (by running the recipe you plan on running) and make sure that none of the guns are shorting. This is a very very important step and sometimes you will have to vent/remount targets upwards of three times but you do not want to have a short during your actual deposition!

6. After the guns have been tested, let the main chamber pump down overnight (this is not 100% necessary but both Pallavi and I had better results with this method).

Day of Sputtering

Wafer Preparation

1. Mount everything for the deposition to an 8-inch wafer (should be some in the bench right next to the sputter) using a small amount of kapton tape. You do not need much.

2. Load the sample into the chamber.


1. Run the recipe that you want to use.

2. All my recipes have a presputter step which involves the Cr gun being on with the shutter closed. This is only necessary if you have opened the main chamber recently. Usually for the first deposition I do the presputter and then skip it for all subsequent depositions.

3. Write down all the wattage, voltage, and amperage of each gun throughout the process.

4. If a short does occur, do not panic and press a stop button. This will lock the whole system and you will not be able to do anything. (Even the stop button on the computer screen will do this!!). Instead just skip all the steps until the recipe is done. You will then have to vent and remount the targets.

5. Once you are done with depositions, please vent and remove all the targets. Also do not forget to change the values in the program so the next person knows the targets were taken out. Then pump back down the chamber (do not disable the device until it has completed the recipe.

Pulling Samples from PDMS Stencil

1. This process should be done delicately because the glass slides break very easily. I find it best to use two tweezers and pull up on the PDMS with one while using the other to hold down the glass slide. Make sure that you move the tweezer holding the sample down to as close as the PDMS as possible while you do this (if you keep it on the edge the glass will crack).

2. I personally like to dismount all the samples at once because if you wait too long the bond between the PDMS and glass will get too strong and it will be impossible not to crack the samples.

3. After samples are dismounted you can go through the typical dealloying procedure to finish the fabrication.

  • Note: I like saving the PDMS stencil in case we ever need alloy coated PDMS. You do not need to do this but it is nice not to waste stuff until you know for sure you will not need it.