Study On Atomic Layer Etching Of Si In Ar/Cl₂ Inductively Coupled Plasmas Driven By Tailored Bias Voltage Waveforms

The continuously shrinkage of critical dimension in microelectronics fabrication leadsmore stringent requirements for technology,which demands more accurate control of trench profile evolution,even achieving the atomic-layer precision.Plasma etching has remarkable advantage in comparison to traditional wet etching,such as good anisotropy,high selectivity and high etch rate.Plasma atomic layer etching(PALE)has atomic-layer resolution,can achieve the mono-layer etching of materials.In etching process,the ion energy and angular distributions(IEADs)bombarding onto substrate play a critical role so that to control IEADs flexibly is very important.Tailored bias voltage waveform is an effective method to modulate the IEADs,and then improve the trench profile evolution.In this paper,a multiscale model,which coupled reactive chamber model,hybrid sheath model and trench model,is used to study the effect of different discharge parameters and different bias voltage waveformson the atomic layer etching of Si in Ar/Cl2 inductively coupled plasmas.The commercial solver CFD-ACE+ is used to simulate the ICP discharges in reactive chamber,and obtain the densities and fluxes of ions and neutrals under different pressures and powers.The hybrid sheath model including fluid model and Monte Carlo model uses the densities of ions and neutrals obtained from CFD-ACE+ as boundary conditions.The fluid model gives the spatial-temporal variables such as potential on substrate and sheath thickness,and the Monte Carlo model takes the collisions between ions and neutrals into account tocalculate the ion energy and angular distributions arriving at the substrate.Finally,the trench model uses the fluxes of ions and neutrals obtained from CFD-ACE+ and the IEADs as boundary conditions to simulate the trench profile evolution.Results show that different discharge parameters,such as pressure and power,influence the trench profile evolution with different bias voltage waveforms synergistically.Tailored bias voltage bias waveforms can provide nearly monoenergetic ion energy distributions,and then get higher anisotropic trench profile.