A simple balanced magnetron should do the job.

Definitely Ar/O2 gas ratio needs to be controlled carefully and the flow rates should remain stable all throughout the sputtering process.

Flow rate must be monitored by continuously by gas flow meters.

There is a huge amount of reported literature on ITO films.

Before suggesting some good papers, it will be nice to know the following:

1) Diameter of your target

2) Do you prefer rf diode or rf magnetron type electrode.

3) Whether you wish to use an oxide target, or a metallic In/Sn metallic alloy target and do reactive sputtering in AR-O2 atmosphere.

Thanks a lot for your answer.

The deposition machine is a linear one with a rotary target of a length of round about 600mm. Typically we´re using ceramic targets and can choose between several compositions (90/10, 95/5, 97/3). To influence stoichiometry we can add oxygen to the argon. Additonally we have a hydrogen line.

To answer your questions:

1) Length 600mm, Outer diameter 150mm

2) We use RF-Magnetron sputtering

3) We use ceramic oxide targets

Experimenting with different magnetrons and target compositions we asked ourself, which combination should be the most promising one to obtain best compromise between electrical conductivity and optical transparency for solar cell applications.

Do you think that the most balanced type of magnetron is the best magnetron for ITO deposition? Is the ion bombardement of the substrate the only reason why balanced ones do a better job for ITO deposition than unbalanced ones? And can you recommend a comprehensive paper dealing with the influence of the magnetron and different atmosphere compositions for ITO deposition?

Best regards,

Ronald

Unbalanced magnetron creates some bombardment and heating on the

films being deposited, hence not a very comfortable idea.

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Please confirm are you planning a production machine with a large sputter target, which will be used regularly on every day. or

planning a simple research laboratory machine with 4inch to 6 inch diameter targets

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I could not understand your target electrode dimensions, on which you are mounting your sputtering target.

You mention (i) Length (600mm), and (ii) outer diameter 150 mm.

I can't figure out the shape of your target with such dimensions.

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600mm means 60 cm, which means 24 inches, this is a huge size.

a) Well if you have a rectangular target you will have length and breadth.

b) and if you have a circular target then you have only Diameter.

c) Besides the dimensions, the other factor is the thickness of the target.

kindly clarify the dimension and shape correctly.

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Please clarify the shape of the target electrode, on your machine, and

are you putting a rectangular /circular target, and what are their dimensions

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I presume you are probably talking about a production machine.

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a) Oxide targets are very costly whatever their size. (4") onwards.

they are sintered ceramics. Need a good bonding for cooling efficiency.

Moreover magnetron sputtering (circular) will create circular tracks

of non stoichiometry on the target surface, and target area will not be utilized economically and efficiently. The larger the dimensions of the target, the more severe are the problems with oxide targets.

b) Comparatively metallic alloy In/Sn with 90/10 or 80/20 compositional ratio are better off, and last for a very very long time.

c) Instead of magnetron , normal rf diode configuration will sputter all over the target surface, and will utilise the target surface area more economically.

Whereas a magnetron electrode will create an undesirable track on both oxide and metallic targets, their surface will become undeven, and will create problems with thickness uniformity in the deposited films at a later stage.

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I will send you some papers, and my own work during my Ph.D. in 1984), Presently trying to collect their soft copies, and will share them with you in a day or two.

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Prof. K. Sreenivas

Dear Mr. Ronald Korn,

enclosing two papers for you.

1) A very good old review on transparent conductors, which covers a lot of work done long ago by sputtering and other techniques written

by Prof. K. L. Chopra.

2) The other paper is my own, where I have developed very high quality ITO thin films using a In/Sn metallic alloy target. or course, I deposited the films first, and then annealed them in cracked ammonia, and achieved very high transparent, and very low sheet resistance. 30 years ago soon after finishing my Ph.D., if I had money I could have started industrial production., sosmehow it never happened. But I still have a strong hope that the process I developed is perfectly suitable for developing transparent conducting thin films on an industrial scale.

As a sputtering expert, frankly I don't like using oxide targets, I always believe in metallic, or metallic alloy targets and do reactive sputtering, and this offer much better control, a longer life for the target, and high quality films.

The two papers I have enclosed have a lot of information.

K. Sreenivas

Dear Mr. Sreenivas,

you´re right. On long term, there will be a large sputtering machine for ITO layers with rotary targets. Actually we are doing experiments on a smaller machine with a rotary target of the above mentioned dimensions of approx. 600mm in length and 150mm in diameter. The whole target is water cooled. Therefore, there are no problems with the bonding, but annealing the layers after deposition is due to possible impacts on the cell structure and the additional production step not very preferable for large scale production. For rotary targets the utilization of the target is very good. Due to the fact, that rotary targets are in permanent rotation, the racetrack does not create some grooves on the target. Nearly the whole target, except the ends below the turning points, can be used very homogenously.

Thank you very much for your efforts in answering my questions and sending the two publications. I will read them in detail in the next days and will come back to you, if there there will be upcoming questions.

Thanks a lot and best regards,

Ronald