I would like to measure the hardness of 2 nm thick TiN film on Si substrate. What is the procedure I should use to measure such ultrathin film? OR may be it would be better to measure it using AFM?
For so thin film, there is no choice but a local probe. Either ultrananoindentation or AFM. Ultrananoindentation should be preferred as it doesn't need calibration. The resolution on the displacement signal is as low as 0.003 nm and the resolution in load is 3nN, so suh mesurement should be possible. AFM will also do, but needs a calibration with a material having mechanical properties as close as possible to those you expect, otherwise the error can be significant. This can be a major problem. The best would be ultrananoindentation assisted with AFM, so that you can investigate the imprint as well.
Alain
For so thin film, there is no choice but a local probe. Either ultrananoindentation or AFM. Ultrananoindentation should be preferred as it doesn't need calibration. The resolution on the displacement signal is as low as 0.003 nm and the resolution in load is 3nN, so suh mesurement should be possible. AFM will also do, but needs a calibration with a material having mechanical properties as close as possible to those you expect, otherwise the error can be significant. This can be a major problem. The best would be ultrananoindentation assisted with AFM, so that you can investigate the imprint as well.
Alain
You can calculate the critical load of the film by using nano scratch providing the TiN film is robust enough to initially withstand a ramped small load. Nano scratch coupled with some microscopy will provide some information on the material properties of you top layer. You could also measure the coefficient of friction of the TiN.
when the measurement of thin layer 20 nm, the measurement is not accurate anymore as it will take into the consideration of the substrate beneath the thin film. As the measuring probe is seeing the substrate too at this level of thickness.
Thus, the thin film properties is estimated by going through some model or simulation. You might check out Hysitron, they use mathematical expression to estimate the thin film (2 - 5 nm) after feeding the model with the substrate properties. Below this, the properties is estimated by finite element simulation.
Cheun Jye Yow, Can you develop a bit more on the Hysitron model?. Maybe some link. Thank you.
Hystron TI950 has this feature. You would able to find the detail explanation on claim how they able to do it. Contact your local representative of hysitron and request the fundamental of the method. I have been briefed by strategic account manager. The model is development by with Harvard University and current has been licensing to one of the big microchip maker.
Aleksandr, what kind of information about film do you expect to get from the measurement of hardness? Such thin films usually have island structure, so local probe could't gave data about coating.
Yurij, Yurij, I`m going to deposit TiN thin film using atomic layer deposition (ALD), so this film expected to be conformal and compact. I would like to how hard such a thin film could be.
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