Sputter coater

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Revision as of 14:31, 26 October 2012 by Teti (talk | contribs) (Changing the target metal)

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The sputter coater is a realtively easy and straightforward machine to use. However some basic training must be provided before you use it. The appropriate person to contact is Teti Stratoudaki or Richard Smith. Among the various technical points that you need to know to operate the sputter coater you must also be made aware of the basic good manners that you need to demonstrate. This is a shared facility and any misconduct has effect on all the Fab Lab users.

Important information regarding the ID tag system

An ID tag is required to run the sputter coater. If you are new in the lab and you need to use the sputterer please contact Teti Stratoudaki or Richard Smith who can issue a tag for you. The tag must be left on the tag reader, on top of the sputter coater, while the sputtering is taking place. The tag reader of the sputter coater is linked to the computer (sofa), next to the sputterer. In the unlikely event that the computer needs to be restarted, the software that controls the sputter coater needs to be restarted as well:

  • cd /sputterer
  • sudo ./run_sputterer_access_control

You will have to provide the password for the computer (sofa) and the sputterer should then be back in working order.

Thickness calibration

To calibrate the sputter coater FTM coat to a nominal thickness then pass the sample to Rod Dykeman who'll scratch the coating and measure it using a Tallystep.

If the coating is too hard (eg ITO) then you'll have to mask out some areas using photoresist and lift off to provide an edge. This might be possible using some dabs of photoresist rather than a spin-coated layer and mask exposure.

Changing the target metal

If you need to change the target metal sources you need to understand the use of spacers. There are two kinds of spacers: the circular aluminium backing plates and the "batman" shaped spacers.

The backing plates are placed underneath the targets and their function is to bring the two targets to the same level. In the case that one of the targets is thicker than the other, one or more of these backing plates are placed underneath the thinner target.

The "batman" shaped spacers are used to maintain a gap of 1.5mm between the inside of the assembly shield (that is the top "binocular" shaped part of the target assembly) and the front face of the targets. The manufacturer has assumed a standard target thickness of 0.3mm and in this case no spacers need to be used. However, most of the targets that we have in the lab are thicker than 0.3mm and spacers are needed. Each of these spacers is 1mm thick and they are fitted in pairs (one at the top and one at the bottom side of the target assembly).

This is an example of using the spacers: A silver target and a chrome target are required. The silver target is 1mm thick and the chrome target is 1.5mm thick. One of the backing plates is placed under the silver target to bring both targets on the same level. Now the sources stand at 1.5mm instead of the 0.3mm that the sputterer is designed for, a difference of (1.5-0.3=)1.2mm. To account for this, a pair of the "batman" shaped spacers (one on the top and one on the bottom) is placed under the final assembly shield. When using the ITO sample (very thick target), you need to use the thickest backing plate underneath the thin source and two of the "batman" shaped spacers.

A special note on the appropriate screws to be used when fixing the assembly: there are four cap screws that are used to fix the assembly shield in place. The plate on which they are fixed is at 0V potential and the target housing around it is at -1200V. It is very important that the screws do not touch the machine at the back. This is why there are two sets of screws: one to be used when one set or less of the "batman" shaped spacers is used (short screws) and one to be used when two sets or more are used (long screws). If you use the long screws when you should have used the short a) sputtering may not happen and b) you are damaging the threads of the screws and the plate on which they are fixed. Please make sure you know what you are doing!

Finally, after changing the targets, please do not forget to leave a note on the white board (right hand side facing the instrument) as to what targets are currently loaded!

Log book

Do not forget to fill in the sputter coater's log book (located next to the machine). It provides important information for the history and maintenance of the instrument as well as information for the sputtering conditions used by the previous users.