Diagnosis of the Argon Plasma in a PECVD Coating Machine

A Langmuir probe plasma diagnostic system was developed to measure the plasma parameters in a PECVD vacuum coating machine. The plasma was a capacitively coupled plasma (CCP) driven by a radio-frequency (RF) power supply. To avoid the disturbance of radio-frequency field on the Langmuir probe measurement, a passive compensation method was applied. This method allowed the 'dc' component to be passed and measured in the probe circuit. It was found that the electron temperature in the range from 2.7 eV to 6.4 eV decreased with the increase in RF power. The measured plasma density ranged from 8 x 1016 m-3 to 0.85 x 1015 m-3 and increased with the increase in RF power. (low temperature plasma)