| Title |
VI Sensor for Plasma Diagnostics |
| Authors |
박민상(Min-Sang Park) ; 정성현(Sung-Hyeon Jung) ; 이호준(Ho-Jun LEE) |
| DOI |
https://doi.org/10.5370/KIEE.2023.72.8.929 |
| Keywords |
RF; Plasma; Voltage and Current probe(VI Sensor); Faraday Shield; 3D-EM simulation; Gain; Phase |
| Abstract |
To achieve efficient power delivery, an impedance matching system is deployed between the power source and load consumption in the plasma chamber, maximizing power transfer efficiency. Plasma impedance varies depending on process conditions, necessitating precise measurements. One measurement method is the VI Sensor, which measures voltage using a capacitive component in a ring-shaped metal and current using an inductive component through a pickup coil. Electromagnetic wave simulation was used to obtain results, and the impedance of the load on the measurement side was modified (matched, capacitive, inductive) to reflect the changing plasma impedance under different process conditions. Originally, changing the load impedance would result in the same voltage characteristics, but the current gain and phase differ. This is because the induced electric power due to mutual inductance between the sensor coil and RF transmission line is measured, along with the capacitive component. Faraday shield structures were introduced to eliminate capacitive coupling between the RF transmission line and the sensor body, resulting in improved gain characteristics for both the original VI Sensor (-44~-40 dB) and the Faraday shield structure (-43~-41 dB) at 60 MHz, when the load impedance was changed. |