2次元PIC-MCCシミュレーションによるCF4プラズマモデリング

抄録

We investigated the ion densities generated in CF₄ plasma, and developed a practical reaction model of CF₄ using PIC-MCC (Particle-in-Cell Monte Carlo Collision). A Langmuir probe and the quadrupole mass-spectra analyzer HAL EQP300 were connected to a 6-inch-size capacitively coupled plasma reactor for measuring the plasma parameter and the ion densities.
We measured the ion densities in CF4 plasma under the following conditions: RF power range from 50 to 150W, CF₄ gas flow rate 50 seem, and pressure range from 6.7 to 20Pa. In CF₄ plasma, CF₃⁺, CF₂⁺, CF⁺ were generated in the ratio of 1.0: 0.06: 0.04, which indicates CF₃⁺ is dominant. In our CF₄ plasma model, the generations of CF₃⁺ and CF₃ are considered mainly. We also justified our model by calculating the rate equation on CF₄ plasma.
The experimental results and simulation results show good agreements in the electron density, electron temperature, and plasma potential. In CF₄ plasma, as RF power increases, the densities of CF₃⁺ and CF₃ become larger. Simulation results indicate this dependency on RF power. Furthermore, we measured SiO2 etching rates at wafer center and wafer edge to estimate the ion spatial distribution. The distribution of etching rate is similar to CF₃⁺ ion flux distribution calculated from PIC-MCC simulation.
Plasma parameter, the dependency on FR power and pressure, and ion distribution are predicated in our practical plasma model of CF₄