AVS 52nd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuM

Paper PS-TuM3
Angular Dependence of Si@sub 3@N@sub 4@ Etch Rates and the Etch Selectivity of SiO@sub 2@ to Si@sub 3@N@sub 4@ at Different Bias Voltages in a High Density C@sub 4@F@sub 8@ Plasma

Tuesday, November 1, 2005, 9:00 am, Room 304

Session: Plasma Surface Interactions I
Presenter: J.-K. Lee, Seoul National University, South Korea
Authors: J.-K. Lee, Seoul National University, South Korea
J.-H. Min, Seoul National University, South Korea
S.H. Moon, Seoul National University, South Korea
Correspondent: Click to Email
The dependence of Si@sub 3@N@sub 4@ etch rates and the etch selectivity of SiO@sub 2@ to Si@sub 3@N@sub 4@ on the ion-incident angle was studied at different bias voltages in a high density C@sub 4@F@sub 8@ plasma. A Faraday cage and specially designed substrate holders were used to accurately control the angle of ions incident on the substrate surface. The normalized etch yield (NEY), defined as the etch yield normalized to one obtained on a horizontal surface, was unaffected by the bias voltage in Si@sub 3@N@sub 4@ etching but increased with the bias voltage in SiO@sub 2@ etching, in the range of -100 V ~ -300 V. The NEY changed characteristically, showing a maximum, with the ion-incident angle in the etching of both substrates. In Si@sub 3@N@sub 4@ etching, the maximum NEY of 1.7 was obtained at 70° in the above bias voltage range. However, the increase in the NEY with the ion-incident angle was smaller for SiO@sub 2@ than for Si@sub 3@N@sub 4@ and, consequently, the etch selectivity of SiO@sub 2@ to Si@sub 3@N@sub 4@ decreased with the ion-incident angle. The etch selectivity decreased with the ion-incident angle to smaller extents at high bias voltages because the NEY of SiO@sub 2@ was high under this condition. To understand the characteristic changes in the NEY for different substrates, we estimated the thickness of a steady-state fluorocarbon (CF@sub x@) film formed on the substrates. The thickness of a film on Si@sub 3@N@sub 4@ changed with the ion-incident angle, showing a minimum at 70°, and the film thickness was reduced at high angles to smaller extents on SiO@sub 2@ than on Si@sub 3@N@sub 4@. These results indicate that the NEY can be correlated with the thickness of a steady-state CF@sub x@ film formed on the substrate surfaces.