AVS 45th International Symposium
    Plasma Science and Technology Division Tuesday Sessions
       Session PS2-TuM

Paper PS2-TuM8
Effect of Ion Bombarding Energies in Silicon Dioxide Etching

Tuesday, November 3, 1998, 10:40 am, Room 318/319/320

Session: Oxide Etching
Presenter: Y. Hikosaka, Association of Super-Advanced Electronics Technologies (ASET), Japan
Authors: Y. Hikosaka, Association of Super-Advanced Electronics Technologies (ASET), Japan
H. Hayashi, Association of Super-Advanced Electronics Technologies (ASET), Japan
K. Kinoshita, Association of Super-Advanced Electronics Technologies (ASET), Japan
S. Noda, Association of Super-Advanced Electronics Technologies (ASET), Japan
H. Tshuboi, ULVAC Ltd., Japan
M. Endo, ULVAC Ltd., Japan
N. Mizutani, ULVAC Ltd., Japan
Y. Nagata, ULVAC Ltd., Japan
M. Sekine, ASET, Japan
Correspondent: Click to Email
Ion energy is one of the key parameters in the fabrication of high-aspect-ratio contact holes. Ions incident to the wafer have both high- and low-energy components that depend on the bias frequency and the ion transit time across the rf sheath. However, the relationship between ion energies and etching characteristics such as rate, selectivity, profile and RIE-lag have not been well understood. Our goal is to clarify the role of high- and low-energy ions in SiO@sub 2@ etching. We used a planar-type NLD plasma source operating at 13.56 MHz. An rf-floating ion energy analyzer with a mass spectrometer was equipped inside the rf-biased electrode to measure IEDs (ion energy distributions) and ion fluxes at the rf-driven electrode. First, IED measurements were made for Ar/C@sub 4@F@sub 8@/O@sub 2@ plasma at rf biases of 2 and 13.56 MHz. The CF@sub 1@@super +@ ion is the dominant species for both bias frequencies. The ion energies of CF@sub 1@@super +@ were distributed from 89 to 715 eV at 2 MHz, wider than at 13.56 MHz. Next, we measured SiO@sub 2@ etch rates, self-bias voltages and IEDs as a function of bias rf power for both frequencies. We found that the etch rates were defined by the energy and flux of ions mainly at the higher peak region of the IED, whereas the each energy-splitting width of the IEDs and the self-bias voltage at 2 MHz were different from those at 13.56 MHz. Next, we estimated the energy dependence of the etch yield under actual etching condition, using the obtained IEDs and etch rates. We found that the etch yield of SiO@sub 2@ increased monotonically with increase in ion energy and tended to saturate at a value of 1.5 molecules/ion at energy levels exceeding 800 eV. This energy dependence of the etch yield led to a 65 % contribution of high-energy ions to the etch rate. @FootnoteText@ This work was supported by NEDO.