I made a simple lowcost sputter test setup. The purpose of this is to gain some knowledge and feeling of the methode and to know how to work with its parameters. My target is to deposite a shiny mirror metal layer on plastic objects. For now I do not use a magnetron sputter source. Instead of that, The setup is just made of a glass jar, base plate is target (cathode), ring magnet under target and a substrate in a metal clamp (anode) hanging 15mm above the target in the chamber. My plan is to procure professional material when I poses some the experience with the test setup.
So after several attempts, I succeed in sputtering a copper shiny mirror layer on plastic PET as substrates. The layers were also conductive. The plasma was quite stable. Altough, after a while it was not self sustained. So I increase the chamber pressure by adding Argon in the chamber to reignite the plasma and etc.. The working pressure is between 10E-2 and 10E-3 mbar.
After that I tried the same process for Aluminum. Unfortunately, while the sputter process, there was a lot of arcing between the anode and cathode. I adjusted the target substrate distance and cleaned the room with aceton. But still the arcing repeated in the next process. Also the arcing leads my turbo molecular pump to go in error.
So my question is, what could be the reason for such arcing between the anode and cathode for sputtering aluminum? Also the arcing does leave scars and some serious contamination on the target surface. A picture of the target surface is attached to this topic.
Looking forward to your feedback.
Any aluminium target doesn't consist of pure Al at its surface: there is a rather thick native aluminium-oxide (non-conductive) layer. Therefore, it is difficult to start a sputtering process. You need to remove such layer by sputtering first. To facilitate this, immedicately before closing the chamber, it is Always good to 'scar' the target surface, for instance with a screw driver. The scratching removes the native oxide layer in the scars, which act as points to start the sputter erosion process. Work with high pressure and low power initially until the native oxide layer is removed (this might take several hours). Once you have a stable plasma all over the racetrack (no arcing anymore), reduce the pressure and increase the power. Remark that you only get good metallic coatings in a sputtering process with a depositon pressure of some 1 - 4 µbar !
What was the courrent and voltage in case of copper and aluminium ? If you have some electric arc the must be some high higher voltage ... Maybe you are trying to reach some current setpoint which is not possible and voltage which leads to too high voltage. Is it realy Aluminum ? It does not look like aluminum for me anymore. .. Mybe some oxid or nitride which is not conductive so the voltage increased too much. Check condutivity of this target.
