Abstract: In a CF₄/Ar inductively coupled plasma, the relationships between SiO₂ etching rates and the ion incident angles were investigated, where the ion incident angle controlled by using a Faraday cage. The RF bias voltage applied on the SiO₂ substrate range from -20 V to -300 V. Two different cases of normalized etching rate （NER） are observed in the bias voltage region. When the magnitudeof the bias voltage is smaller than 100 V, the NER changes following a cosine curve with respect to thesubstrate surface angle θ. When the magnitude of the bias voltage is larger than 100 V, the NER deviates to higher values from those given by a cosine curve at ion angles between 15° and 60°, andthen quickly decreases at angles higher than 60° until a net deposition is observed at angles near 90o.Etching of SiO₂ at ion angles below 60° are determined by the ion energy transferred to the surface, which affects the SiO₂ etching rate and the rate of removal of a fluorocarbon polymer film formed on the substrate surface simultaneously.