Diagnostic of surface wave plasma for oxide etching in comparison with inductive RF plasma

Surface wave plasma (SWP) and inductively coupled plasma (ICP) reactors are high plasma density, unmagnetized sources that show promise for use in nex t-generation etching processes. We compare the 2.45 GHz SWP with the 13.56 MHz ICP in terms of the radical composition in C4F8/Ar discharges and the e lectron energy distribution function (EEDF). A comparison of the two plasma s was carefully made in an identical plasma vessel at the same wall tempera ture where an antenna coupler on a quartz plate was changed from an expande d waveguide for SWP to a loop coil for ICP. Reactive species measurement at the same electron density under the same gas conditions showed marked diff erences. First, the dissociation degree of C4F8 at the same electron densit y is higher in TCP than in SWP. Second, neutral radical densities (CF3, CF2 ) at the same electron density are several times higher in SWP than in ICP, and ICP has a high F radical density. Third, as regards ionic composition, ICP contains more Ar+ and less fluorocarbon ions (CmFn+), while large mole cular ions (C2F4+, C3F3+, C3F5+) exist in SWP. In conclusion, ICP is more d issociative than SWP at the same electron density. This result is tentative ly attributed to the difference in the EEDFs of the two plasmas, since opti cal emission spectroscopy of Ar I suggests 1.5-2 times mon high-energy (> 1 4 eV) electrons in ICP than in SWP.