Real-Time Plasma Density Measurement using a Capacitance Measurement Sensor Embedded in an Electrostatic Chuck

In plasma processes used for semiconductors and displays, the need for plasma diagnostics is increasing to enable accurate process control. Therefore, a diagnostic method that can be applied to actual process gases and monitor plasma conditions without perturbing the plasma is essential. Currently, diagnostic tools such as the Langmuir probe are employed to measure plasma density in the semiconductor industry. However, these techniques have limitations in their applicability to reactive process gases and in their restricted diagnostic regions. In addition, since the probe is directly exposed to the plasma, issues such as contamination and corrosion can lead to measurement errors. Moreover, such direct contact can interfere with the plasma, making it difficult to maintain stable processing conditions.

In this study, a coplanar electrode sensor embedded within the electrostatic chuck was utilized to prevent contamination and corrosion. The sensor was embedded inside the chuck to enable plasma monitoring and real-time plasma density measurement. The results were compared and analyzed against those obtained using a single Langmuir probe (SLP) and optical emission spectroscopy (OES). Experiments were conducted by varying the applied power of a capacitively coupled plasma (CCP) source using a 13.56 MHz RF generator.