基于空心电极增强的容性耦合射频等离子体特性

In order to improve the plasma density, hollow electrode is used to replace plate electrode in capacitive coupled radio frequency(RF) discharge. The plasma characteristics of this RF hollow electrode discharge are studied experimentally. Langmuir probe was used to diagnose the effects of electrode gap, hole diameter and hole depth on plasma electron density. The self-bias voltages under different discharge parameters were compared. The results show that, when the hole diameter d equals 20 mm, the electrode gap L equals 3 cm, the hole depth h equals 3 mm, and p is in the range of 50~300 Pa, the plasma electron density obtained outside the hole is the highest, about 10¹⁷~10¹⁸ m^-3. At the same time, the self-bias voltage about the hollow electrode is also completely consistent with the 'area ratio' rule of sheath voltage distribution under different discharge parameters, the sheath voltage at the small electrode area is higher. The coupling of RF oscillating heating and hollow cathode effect can produce plasma with good stability, high ionization rate, and high density. Geometric parameters and self-bias voltage have important influences on obtaining high density plasma.