AVS 45th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS2-MoA

Paper PS2-MoA9
Ultrahigh Frequency vs. Inductively-Coupled Chlorine Plasmas: Comparisons of Cl and Cl@sub 2@ Concentrations and Electron Temperatures Measured by Trace Rare Gases Optical Emission Spectroscopy

Monday, November 2, 1998, 4:40 pm, Room 318/319/320

Session: Diagnostics I
Presenter: V.M. Donnelly, Bell Laboratories, Lucent Technologies
Authors: V.M. Donnelly, Bell Laboratories, Lucent Technologies
M.V. Malyshev*, Bell Laboratories, Lucent Technologies
S. Samukawa, NEC Corporation, Japan
Correspondent: Click to Email
Using trace rare gas optical emission spectroscopy, Cl and Cl @sub 2@ number densities (n@sub Cl@ and n@sub Cl2@) and electron temperatures (T@sub e@) were measured for two source configurations of high-density chlorine plasmas. In one configuration, the reactor was outfitted with a spoke antenna, operated at a resonant ultrahigh frequency (UHF) of 500 MHz. Alternatively, the same reactor was configured with a single loop, inductively coupled plasma (ICP) source operated at a radio frequency of 13.56 MHz. Optical emission from trace amounts (1% each) of rare gases added to the main Cl@sub 2@ feed gas were recorded as a function of power and pressure, during slow etching of the SiO@sub 2@-coated Si wafer. Modeling was used to derive T@sub e@ from these data. Additional emission from Cl@sub 2@ (at 305.0 nm) and Cl (numerous lines between 700 and 900 nm), normalized to the appropriate emission from the rare gases (i.e. actinometry) was used to obtain n@sub Cl@ and n@sub Cl2@. In the ICP, T@sub e@ decreased monotonically from 5.5 to 1.2 eV as a function of increasing pressure between 1 and 20 mTorr. Conversely, with the UHF configuration, T@sub e@ was 3.3 eV, independent of pressure between 1 and 7 mTorr, and then decreased to 1.7 eV as pressure was increased to 27 mTorr. At the same input power (1000W), both sources resulted in electron densities of 1 x 10@super 11@cm@super -3@ at 3.5 mTorr, yet the UHF plasma was much less dissociated (30%) than the ICP (70%). This is attributed to differences in the electron energy distributions in the two plasmas, especially at low pressure, caused by differences in energy transfer from the E-field to the electrons, through collisions with the gas. @FootnoteText@ *Also at Princeton University