Study on self-bias voltage induced on the substrate by r.f. bias power in a high density plasma

Abstract

Characteristics of the self-bias voltage induced on the substrate by a r.f. bias power in a high density helicon wave plasma were studied. The self-bias voltage induced on the wafer by r.f. bias of 300 kHz (less than the ion plasma frequency value) was directly measured with a Pt wafer using a high voltage probe. The self-bias voltage and the peak-to-peak voltage were influenced by both bias and source RF power in the high-density plasma. A new probe system was designed to trace these phenomena. It was found that these phenomena were related to the charging time of the blocking capacitor by the ion current. The role and effect of the negative ions on the etching process at low RF frequency are discussed. A method to apply the RF bias effectively without the influence of the source power was suggested for application in a real etching system.