Influence Of Background Gas Transport Process On Discharge Mechanism In Radio Frequency Inductively Coupled Plasma

With the advantage of operating at low gas pressure and high plasma density,inductively coupled plasma(ICP)source have been widely used in the plasma processing.As the feature scale in integrated circuits becomes smaller,the demands on the etch process become increasingly stringent[1,2].Controlling the production and transport of neutral species is crucial for etch process,as they can significantly influence the bulk plasma properties and then surface process under certain circumstances.To the influence of the three fields of background gas including convective velocity,pressure and temperature on the plasma,we use the ICP and SPF interfaces of COMSOL commercial software.The pure convection effect is considered by choosing incompressible laminar flow in SPF interface to calculate background gas,and the background gas density in ICP is constant.The convection and pressure effect is considered by choosing compressible laminar flow in SPF interface to describe background gas,and the background gas density in ICP is calculate by the pressure in SPF interface through idea gas equation.With the gas inlet nozzle located around the dielectric disk and the pumping port around the chamber floor edge,a traditional ICP reactor is used in the simulation.The gas heating effect is omitted and a fixed room temperature is used for the background gas.These effects will be considered in future work.Due to the low velocity value of convective field,the effect of pure convection on Ar ICP is mainly obvious on meta stable Ar atom(abbreviated as Ars).The convection has direct influence on Ars atoms and indirect influence on electrons.Concisely speaking,convection destroys the conventional symmetrical spatial distribution of Ars density profile and forms an imbalanced one by three mechanisms,i.e.,(1)suppressing Ars diffusion to the wall on the upper chamber periphery,(2)prolonging Ars density profile near the down chamber border,(3)generating new radial diffusion loss area near the nozzle.This novel Ars density profile alters the traditional neutral radial diffusion scheme on the wall,and accordingly Ars atoms loss on the wall is reduced and the Ars atoms density is increased.The increased Ars atoms density results in high electron density and temperature by means of the multi step ionization process and its low threshold energy.To identify the influence of pressure field,we calculate convective field considering both pressure and velocity field of background gas,and compare with the same inlet velocity magnitude case.With the condition of velocity field only,Ars number density is affectedsignificantly near the wall.Whereas,with the mix of pressure,this is not the main affect.By analyzing the Ar number density and multi-ionization rate,the valley of Ar moves from the central to the place under coil.So as the peak value of Ars.At the same time,with the increase of multi-ionization rate,the peak value of electron density and the consumption of Ars are increasing accordingly.As comparing with the increase of excitation rate,the consumption is more significant,hence the peak value of Ars density is decreasing.Owing to the changing trend is influenced by the place of coils,we compared the results at different place of coils including moving left and right.And we find the peak value of Ars number density reducing more significantly when move the coils left.