Measuring device and method of obtaining thickness of sheath

A method of obtaining a thickness of a sheath, the method comprising:

• (a) placing a measuring device on a substrate support in a chamber of a plasma processing apparatus, the measuring device including:
• a substrate disposed on the substrate support of the plasma processing apparatus,
• a transmission circuit provided in the substrate, and configured to generate a microwave,
• a transmitting antenna provided in the substrate, and configured to transmit the microwave generated by the transmission circuit as a transmission wave,
• at least one receiving antenna provided in the substrate, and configured to receive a reflected wave of the transmission wave by plasma above the substrate support as at least one reception wave,
• a reception demodulation circuit provided in the substrate, and configured to generate at least one signal that reflects the thickness of the sheath between the substrate and the plasma, from the at least one reception wave, and
• a calculator provided in the substrate, and configured to obtain the thickness from the at least one signal;
• (b) generating plasma in the chamber of the plasma processing apparatus;
• and
• (c) while the plasma is generated in the chamber, obtaining the thickness from the at least one signal in the calculator of the measuring device placed on the substrate support.