Development of High Accuracy VI Sensor

Plasma plays a crucial role in the etching and deposition process of semiconductor fabrication. The decrease in size of the equipment used in the process results in problems such as arcing and leakage. As a result, accurate measurement of the load impedance of RF plasma is a critical factor for stabilizing the process, enhancing equipment efficiency, and ensuring tool-to-tool matching in semiconductor equipment. Presently, most VI sensors are categorized into voltage sensors, which rely on displacement current due to capacitive coupling between the RF electrode and voltage measuring electrode, and current sensors, which are based on the mutual inductance between the RF electrode and the sensor coil. The existing VI sensors are challenged by the capacitive coupling component, which is induced in the current sensor in the form of a coil. This is due to the variability of its value based on the load impedance and frequency, causing the phase angle of the plasma load impedance in semiconductor equipment to impact the error of the current sensor. In this study, we present a method of measuring voltage and current using a single sensor, rather than the previously separated two sensors, through the utilization of a single toroidal coil. Additionally, the study outlines a method for eliminating the capacitive coupling component, induced in the current sensor, via equivalent circuit analysis.