The dielectric film is sputtered, such as a SiO2 diffusion isolation layer before the ITO film is plated on 

the glass. 

The SiO2 film is sputtered by radio frequency. 

Usually, when the ions in the glow discharge hit the cathode during sputtering, they will neutralized the 

electrons of the cathode, 

and the sputtering phenomenon can continue. 

However, if the target itself is not conductive, there is no electron neutralization and positive charge 

accumulates on the target, 

which will cause the replacement of DC power supply and the pause of the ion impact phenomenon.