I am depositing thin films of Co using RF sputtering (magnetron) system. The deposition pressure is 7 x 10-3 mbar and RF power is 80 W at 20 sccm Argon flow. Earlier I was getting a sheet resistance around 400 ohms for a 4 nm thin film but now after almost 1 month, the 4 nm film resistance is coming around 1k ohm and there is no FMR signal is coming. I have changed the gas cylinder and tried to check the the possible things to look for.
Now I want to work on power and deposition pressure. Can anyone please help me how these parameters effect the film quality and magnetic behavior of Cobalt.
Thanks
Best Regards
Pinki
Dear Pnnki,
Following info seem to be relevant and helpful:
https://www.researchgate.net/publication/224547620_Magnetic_and_structural_properties_of_rf-sputtered_CoFe_and_CoCr_multilayers
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https://www.semicore.com/news/92-what-is-rf-sputtering
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Magnetic anisotropy and electrical property of CoZrTaB thin films deposited by oblique sputtering
https://aip.scitation.org/doi/10.1063/9.0000234
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The erosion of the target with usage is often a problem in thin film deposition. Can you try changing the deposition time, to see if can recover the previous values for resistivity and magnetic? If the film is thinner because of lower dep rate , this can explain the degradation of results.
Thank you Susana Cardoso for the answer. Yes, I also thought of this reason and did thickness calculations and the rate is almost the same as before with a slight variation of 0.1-0.3 nm.
Also, I have changed the targets, in starting I used a Co target with a 3-inch diameter and 2 mm thickness. For this target earlier I was getting the resistance around 400 ohms as I mentioned before. But when the problem started, I changed the target to 3 inch and 2-inch diameter with 0.2 thickness. But I am unable to solve the issue.
I hope this information can help you understand the problem in a better way.
Thanks
Pinki
Dear Pinki,
There should be no problem when depositing a magnetic element. What they have to find is the right power for the conditions of their target. For this I recommend that you analyze the maximum operating power according to the thickness of the target and the material. Then they can vary a range less than 10% of that power to find the appropriate parameters. Additionally, is very important considerer the pression of the chamber, because the Cobalt is avid for oxygen, therefore small layers of cobalt oxide can be generated in the upper layer of the target and it is necessary to continuously clean the target before making deposits to avoid obtaining cobalt oxide films that can increase the resistance of the films. A more detailed idea of the operation of the magnetron can be seen in the book THIN FILM MATERIALS TECHNOLOGY Sputtering of Compound Materials by Kiyotaka Wasa, Makoto Kitabatake, and Hideaki Adachi.
I also recommend that you look at other articles where they manufacture with your material to give you an idea of the powers they use.
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