Effects of gas composition, focus ring and blocking capacitor on capacitively coupled RF Ar/H2plasmas

The capacitively coupled discharges in Ar/H 2 mixtures operating at a RF frequency of 13.56 MHz and the total gas pressure of 100 Pa are investigated by means of a two-dimensional fluid model, in which a blocking capacitor is serially connected to the power electrode. The gas mixtures of Ar with 0–10% H 2 and the blocking capacitors of 1 and 100 nF are taken into account. The applied voltage is 200 V and the gas temperature is considered to be 300 K. The density profiles of all the plasma species in the discharges are obtained. Results show that the plasma discharge is concentrated over the focus ring, not being in the center of the reactor. A large potential difference and a high capacitive power deposition appear at the surface area between the substrate and focus ring. With the addition of small amount of H 2 to Ar, the electron density markedly decreases. It is found that the reductions of the metastable excited argon density and the metastable pooling ionization rate due to the addition of H 2 are the main reason that causes the electron density decrease. The self DC-bias generated by the blocking capacitor is examined.