Questions regarding sputtering machines, their magnetrons, and etch process

[Mike_In_Plano]

Hello,

Years back, I used to work with a sputtering machine, but I never really understud some of the activities within the machine.
One of the things that puzzled me was why the target was to be eroded, while the surrounding metal structure that held it in place and formed the lid, was not. I could see that the targets were eroded in the center and in a concentric ring. Are these the areas for the poles of the magnet?

The other thing that puzzled me was etching. The substrate didn't seem to have anything magical about it that it would suddenly start loosing material. There was an electrical switch on the machine and a different gas source, that was manually switched. There was a shutter that covered the target, which I presume was to prevent plating the target with material from the substrate? But what as to what was really going on, I'm clueless.

Finally, I guess I'm curious about the impedance that the target typically represents. We had 250 watt RF source, and it went into a matching network on the back of the sputtering chamber. It took a bit of jiggling about of the load / resonance at the transmitter to get a good plasma in the chamber, and typically, the "sweet spot" would shift a little between firing and optimal matching.

Anyway, I know these are a lot of specific questions, but the machine always was of great interest to me, and none of the documentation was very detailed. It would make me a happier man to have some of these mysteries resolved.

Thanks,

Mike

 

[Mapes]

Chapman's Glow Discharge Processes is a classic in this area. Very understandably written, with all the fundamental background that never makes it into the manuals. Also very good: Vossen and Kern's Thin Film Processes and Campbell's The Science and Engineering of Microelectronic Fabrication. I think you'd get a kick out of reading some of these, since you have practical experience.

 

[Mike_In_Plano]

Thanks for the reference.
However, the book is fairly expensive, and not to be found in my local libraries. Does anyone have a cheaper suggestion. Particularly regarding the etch process. This question has bugged me from day one. Do they apply a - voltage to the substrate to encourage stripping?

Mike