Simulation Study Of Hydrogen Discharge Ion Source Plasma And Its Induced Ion Characteristics

Inductively Coupled Plasmas（ICPs）are capable of generating high plasma densities at low RF voltages,have a wide range of air pressures,a stable operating space in terms of power,and can be independently controlled in terms of ion energy while avoiding electrode contamination.Therefore,ICP is widely used in plasma etching,ultra-large scale integrated circuit fabrication,thin film deposition,etc.The ion flux and ion energy in ICP influence the etching efficiency in microelectronic processes and the ion angle influences the anisotropic distribution in the etching process.Moreover,the ion energy can drive the reaction on the material surface,affecting the reaction rate and polymer formation,which plays an important role in the selectivity of etching.In this paper,the effects of external parameters such as bias voltage,RF power,operating air pressure and different chamber structures on the ion energy distributions（IEDs）and ion angular distributions（IADs）are investigated through the development of a two-dimensional hybrid model of the plasma,which provides theoretical support and equipment optimisation solutions for process Theoretical support and equipment optimisation solutions are provided for process development.A columnar ICP hybrid model was developed using multi-physics field finite element simulation software,and the electron density and temperature radial distributions obtained from the model were compared with experimental results to verify that the results were in good agreement.The coupled,,charged particle tracking module was also used for the specific analysis of IEDs and IADs under DC bias voltage conditions.The results show that the IEDs show single and double peaks influenced by theτ_i（ion crossing sheath time）/τ_rf（RF period）ratio,and their half-height width variation is negatively correlated withτ_i/τ_rf.The increased DC bias voltage and RF power lead to an increase in sheath pressure drop and a decrease in the potential difference between the centre and the edge of the chamber,resulting in a decrease in the ion deflection angle and the half-height width of the IADs.Increased operating air pressure causes increased particle collisions,resulting in an increase in the half-height width of the IADs.The two-dimensional Ar/H₂hybrid gas mixture axisymmetric hybrid model and the whole model were established,and the ionic characteristics of the two models under different discharge parameters were compared and analyzed.The results show that the radial distribution of electron density in the whole model is larger than that of the axisymmetric model,and the electron temperature is just the opposite.Sinceτ_i is greater thanτ_rf in the model,and the IEDs are unimodal structures,their half-height and width changes correspond toτ_i/τ_rf,and under certain discharge conditions,the whole model can produce narrower IEDs.Moreover,under the same discharge conditions,the whole model has a smaller radial potential difference and a more symmetrical radial horizontal potential,and the released ions are more symmetrical and have smaller deflection angles in the axial direction of the ion release point,and the half-height and width of the whole model IADs are smaller than those of the axisymmetric model as a whole.The effect of RF bias amplitude,frequency and operating air pressure on the IEDs was investigated by applying a DC bias and superimposing an RF bias voltage to a columnar ICP hybrid model containing hydrogen vibrational excited states and negative hydrogen ion related discharge reactions.The results show that the IEDs all form a bimodal structure.As the amplitude of the RF bias voltage increases,the frequency decreases and the operating air pressure increases,τ_i/τ_rf gradually decreases,resulting in a gradual increase in the double-peak spacingΔE of the IEDs.As the frequency of the RF bias voltage increases,the plasma potential to which the ions are subjected after release is slightly different,making the process of decreasingΔE end up with a smaller change in the position of the high energy peak of the IEDs than the low energy peak.In turn,the increased operating air pressure causes the IEDs to move in an overall lower energy direction,H₂and H₂⁺have a larger collision cross-section,resulting in a significant drop in the peak value of H₂⁺’s IEDs.