The Characteristics Of Capacitively Coupled Discharge Driven By Direct Current Combined With Dual Frequency Sources

Ultralarge-scale integration circuit industry is moving fast towards production of larger size wafer with higher integration level and narrower etching line width. Large area uniform plasma sources which can supply high etching rate, high etching selectivity, high anisotropy and low dielectric damage come into being. Direct current combined with dual frequency capacitively coupled sources generated by adding an extra direct current bias source to the traditional dual frequency CCP is just one of them. Therefore, it’s essential to investigate physical properties in capacitively coupled plasma driven by dc-enhanced dual frequency source to achieve better optimization of the manufacturing technique.In this paper, we develop a1-dimensional PIC/MCC model by the following steps:initiate charged particles, re-assign charges with cloud-in-cell method, solve Poisson equation using chase method and move particles with frog-leap technique, deal with collisions among particles using Monte Carlo. By using the PIC/MCC model, we perform the numerical simulation of discharge properties in CCP driven by the hybrid dc/df for the mixture gas of Ar and O2.By comparing distribution profile of each plasma parameter between the condition with dc source and without dc source, results are listed as follows:the application of dc source can produce dc sheath and alter the spatial-temporal distribution of gas ionization rate greatly. For example, it may decrease the ionization rate in the first half low frequency period, but increase the ionization rate in the second half If period. Overall, the average ionization rate and charged particles density are enhanced. It can also forward the maximum electron energy to100eV+dc (eV). This result coincides with the result in Diomede’s paper. Electron temperature in the sheath adjacent to dc source and the number of electrons with high energy is increased. Besides, it can propel more charged particles to wafer. Especially, it can raise the ratio of electron to ion fluxes from-0.997to-1.741. This will contribute to suppressing the surface charging effect in etching process. Furthermore, in the voltage range of0V to-300V we adopt in this paper, we find that the average ionization rate, density of charged particles, electron temperature in dc sheath and charged particles fluxes flowing to the lower electrode all increase with the increasing voltage.Through the simulation on distribution of each plasma parameter under the circumstances of different mixture ratios of Ar and O2, we conclude that with the increase of oxygen proportion, plasma electron density, charged particle fluxes and charge ratio will decrease. Meanwhile, electron temperature is lowered, too. The decreasing trends of the plasma parameters mentioned above under the circumstance of discharging with-200V dc source are lower than that under the circumstance of discharging without additional dc source.