In magnetron sputtering, the voltage determines the energy of the positive ions bombarding the target surface. I assume that the voltage is about -400 to -500 V in your system. If you check text books on sputtering, you will see that the sputter yield will only slightly vary when the voltage (or rather the ion energy) is increased from -400 to -500 V (corresponding to 400 - 500 eV for the typically single charged ions in DC sputtering). Thus, in DC magnetron sputtering, the voltage has only a minor effect on the sputtering rate.

In contrast, the current determines the number of ions bombarding the target surface. It is thus directly proportional to the sputtering rate. This is also the reason why most people operate DC magnetrons in current or power controlled mode.

However, things might change completely during reactive sputtering, in particular when growing less conductive oxide films. If that is the case, please check the voltage versus time behavior. If voltage increases with time, this might be an indication for target poisoning. To avoid this, you need to carefully adjust and control sputtering power/current and reactive gas flow.

Dear Jose,

The deposition rate of the magnetron sputtering is linearly proportional to the applied power if the rest of the process parameters (Ar pressure, temperature, target to substrate distance, etc.) are kept constant.

Dear Christian Mitterer ,

Thanks for the great reply.

Yes.. The voltage is close to 410 V in my deposition. I am depositing oxide films of zinc using the DC magnetron sputtering. Since it is a reactive sputtering, I can observe target poisoning.

In constant power mode, the voltage goes up during deposition and proportionally the current comes down. I was worried about its influence on the deposition rate and the film property as I have to deposit really thicker films. I am using an old system where there is no crystal monitor to observe the deposition rate..!!

Best,

Jose

Dear Milko Angelov ,

Thanks a lot for your reply.

I am currently doing the deposition at constant power mode and all the other parameters are kept constant. But due to target poisoning, the voltage is increasing during longer depositions. This causes the current to come down. I was worried about this.

Best,

Jose

Dear Jose,

In case of reactive sputtering to can achieve constant deposition rate you must control the oxygen flow such a way to keep constant discharge voltage also during the sputtering in power constant mode. The second thing, which will help you, is use of MF pulsed DC power supply instead of straight DC.

Best regards,

Milko