Recently I have done ITO thin film deposition by magnetron dc sputtering. But we didnot get proper deposition.we did not get transparent film and the resistance in order of few kilo ohms.can you please suggest me how to deposit proper ITO caoating on glass substrate?
We use a pulsed DC power supply, but your issues may be due to many things.
1) How thick is the film? A couple hundred angstroms should give you a continuous layer. Over 1000 A and you will start losing transparency. Thicker the film, the more opaque.
2) Increasing the deposition temperature on our tool will lower the resistivity.
3) The lower the oxygen content; the more uniform, but the less transparent and more metallic the film will be.
4) ITO deposited at room temp and not annealed will slowly oxidize over time, changing the conductivity.
5) I was told that ITO is very sensitive to other materials in the chamber and can be easily poisoned. We have a dedicated sputter tool for ITO.
Hi Aaron
Thank you so much for your Detailed response. I am wondering how ITO can become poisoned and which material can make poison ?
Can you please give some more information on this?
Our ITO sputtering tool only has one gun and we asked the tool's manufacturer about using other targets in the same gun (TiO2 to be exact). They recommended that we purchase another set of chamber shields and shutter for other targets. I was not sure if they meant other gases or other materials ruining the ITO. I have noticed that frequently cleaning the "ITO only" shields is also good for the films.
The deposited films in your picture seem to be quite thick. Thickness should not be a problem. Try to anneal them in a reducing gas like Nitrogen, or cracked ammonia, or even oxygen at temperatures less than 300 deg C. You will turn them into highly transparent films. I found cracked ammonia to be the best long ago. If you want to achieve insitu a good transparent, try to regulate the Ar to O2 ratio carefully.
Thank you so much Sreenivas sir. Sir Here we are using ITO sputter target to deposit ITO film . I am not sending any oxygen to inside the chamber.Do we need to send the oxygen also ?
For which wavelength you are looking its transparency? You might have different parameters for wavelengths?
Normally oxide ITO targets are relatively expensive in comparison to In/Sn metallic alloy targets. ITO oxide target it self will begin to loose oxygen upon repeated sputtering runs. Initially they are whitish, and slowly they become brown or greyish. I have used mostly In/Sn metallic alloy targets, and did reactive sputtering in Ar+O2 sputtering gas, and later post annealed he films.
Yes a little bit of oxygen (5 to 10%) will improve the transparency a lot, while using oxide ITO targets.
There is a classic review paper paper by Prof. K. L. Chopra, IIT delhi on transparent conducting oxides published in Thin solid films. You should consult this paper, which reviews various deposition conditions with oxide targets.
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