Inductively Coupled Plasmas are so called because the RF electric field is induced in the plasma by an external antenna. ICPs have two main advantages: 1) no internal electrodes are needed as in capacitively coupled systems, and 2) no dc magnetic field is required as in ECR reactors. These benefits make ICPs probably the most common of plasma tools. These devices come in many different configurations, categorized in Fig. 10. In the simplest form, the antenna consists of one or several turns of water-cooled tubing wrapped around a ceramic cylinder, which forms the sidewall of the plasma chamber. Fig. 2 shows two commercial reactor of this type. The spiral coil acts like an electromagnet, creating an RF magnetic field inside the chamber. This field, in turn generates an RF electric field by Faraday’s Law: $$ \nabla \times E = {{ - dB} \mathord{\left/ {\vphantom {{ - dB} {dt \equiv }}} \right. \kern-\nulldelimiterspace} {dt \equiv }}\dot B, $$ (3) B-dot being a term we will use to refer to the RF magnetic field. This field is perpendicular to the antenna current, but the E-field is more or less parallel to the antenna current and opposite to it. Thus, with a slinky-shaped antenna, the E-field in the plasma would be in the azimuthal direction.