Hi, I am new in the field of thin film materials. I am currently trying to measure the sheet resistance of Ag thin film of about 10-50nm thickness by doing an evaporation deposition onto a substrate and measure it with a 4pin probe. I am using 1mA with 100V compliance.
(1)When Ag layer is deposited onto glass substrate, I am unable to get proper reading as resistance is too high(more than 450k Ohm/cmsquare). (2)When using silicon wafer as substrate, my result ranges from 10-50 Ohm/cmsquare across the sheets.
My questions are:
1. How does the substrate affect the measurement of the Ag thin film?
2. Any idea why the result I am getting when doing it on (2) has a big range? Is there anything I can do to improve the consistency of my reading?
Thank you.
Best Regards,
Edwin Ferbianto
Is important to answer few questions: What kind of equipment you used, How many measurements you done, All are the same? In terms of electrical measurements using 4-point probe the sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. The quality of your sample are also very important, as you could read signal from the substrate insted of your films. Based on the size of your samples I think- Nano-4P probe STM or Two-probe STM will be the best for experiments, especially at the atomic level.
Hi Ewa, thank you for your reply. I am using Keithley2400 to measure the resistance. The experiment is done for a few times and all indicated similar results. The quality of the sample should be quite good as when measured using ellipsometry, it shows quite an evenly distributed film thickness. I am just wondering if for my experiment (2), ie. when using wafer substrate, I could get a more consistent sheet resistance value.
Hi Edwin,
Using a 4 Point Probe (4PP) sometimes leads to uncontrollable and non-reproducible conditions that lead to highly unreliable measurements, as I previously mentioned, the contact resistance of your probes will depend on their intrinsic quality and on the quality of the contact (sharp or round endings/profile of the tip, force which you applied,...)you wrote that your films results shown quite an evenly distributed film thickness, just to double check-you did study of your possible porosity? I would advise you to check the probes quality, and if you did not check the porosity of your samples, also its worth to check your poore wafer sheet resistance.
Hi Ewa,
Thank you for your prompt reply. I will take a look on the setup of the probe and will try to change the rate of deposition on the next experiment to see how porosity affect the resistance. Meanwhile, I am wondering how the substrate will affect the resistance measured? From my glass/wafer experiment, it seems that the substrate affect the measurement a lot. Once again thanks for the help.
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