The dual cylindrical inductively coupled plasma source,compared to the conventional structure of inductively coupled plasma source,can significantly improve the uniformity of plasma.It has an enhanced potential for ap...The dual cylindrical inductively coupled plasma source,compared to the conventional structure of inductively coupled plasma source,can significantly improve the uniformity of plasma.It has an enhanced potential for application in processes,such as etching and ashing.A uniform plasma can be obtained by allowing the remote plasma from the upper chamber modulate the main plasma generated in the lower chamber.In this study,a fluid model was employed to investigate a dual cylindrical inductively coupled Ar/O_(2)discharge.The effects of external parameters on electron density,electron temperature,O atomic density,and plasma uniformity in the main chamber were studied,and the reasons were analyzed.The results of this study show that remote power can control the plasma uniformity and increase the plasma density in the main chamber.As the remote power increased,plasma uniformity improved initially and then deteriorated.The main power affected the plasma density at the edge of the main chamber and can modulate the plasma density in the main chamber.The gas pressure affected both the uniformity and density of the plasma.As the gas pressure increased,the plasma uniformity deteriorated,but the free radical density improved.展开更多
The effects of coil and dielectric window structures on the plasma distribution are examined in a cylindrically symmetric planar inductively coupled plasma(ICP).A two-dimensional(2 D)fluid model is employed to investi...The effects of coil and dielectric window structures on the plasma distribution are examined in a cylindrically symmetric planar inductively coupled plasma(ICP).A two-dimensional(2 D)fluid model is employed to investigate the design issues of ICP source for etching.When the gradient coil structure is applied at 400 W and 20 mTorr,the ionization rate caused by the power deposition decreases at the reactor center as compared to that in a reactor with a planar coil above the planar dielectric window,and a rather uniform plasma is obtained.However,for the vertical coil geometry,all the coils move to the position of the outermost coil,and the peaks of the power deposition and ionization rate appear at the radial edge of the substrate.In this case,the plasma density is characterized by an edge-high profile.Further,it is observed that the plasma uniformity is improved by increasing the source power under a gas pressure of 20 mTorr and becomes better when the gas pressure increases to 30 mTorr with the source power being fixed at400 W in the gradient coil configuration,but the uniformity of plasma worsens with the rising source power or pressure due to the strong localization in the vertical coil geometry.Moreover,when the discharge is sustained in a reactor with a stepped dielectric window at r=0.135 m,the best plasma uniformity is obtained at 400 W and 20 m Torr because the ionization rate is enhanced at the outermost coil,and the dielectric window at r=0.135 m blocks the diffusion of plasma towards the axis.In addition,higher source power and lower gas pressure produce more uniform plasma for the designs with a stepped window near the symmetry axis.When the dielectric window is stepped at r=0.135 m,the non-uniformity of plasma initially decreases and then increases with the increase in source power or gas pressure.When the dielectric window is stepped at the radial edge of the chamber,the plasma uniformity is improved by increasing the source power and gas pressure due to the enhanced ionization at the larger radius caused by the severe localization.展开更多
In the design of negative hydrogen ion sources,a magnetic filter field of tens of Gauss at the expansion region is essential to reduce the electron temperature,which usually results in a magnetic field of around 10 Ga...In the design of negative hydrogen ion sources,a magnetic filter field of tens of Gauss at the expansion region is essential to reduce the electron temperature,which usually results in a magnetic field of around 10 Gauss in the driver region,destabilizing the discharge.The magnetic shield technique is proposed in this work to reduce the magnetic field in the driver region and improve the discharge characteristics.In this paper,a three-dimensional fluid model is developed within COMSOL to study the influence of the magnetic shield on the generation and transport of plasmas in the negative hydrogen ion source.It is found that when the magnetic shield material is applied at the interface of the expansion region and the driver region,the electron density can be effectively increased.For instance,the maximum of the electron density is 6.7×10^(17)m^(-3)in the case without the magnetic shield,and the value increases to 9.4×10^(17)m^(-3)when the magnetic shield is introduced.展开更多
In this paper,Maxwell equations are coupled with a radially localized global model and an analytical sheath model to investigate the electromagnetic effects under various frequencies and electron powers in large-area ...In this paper,Maxwell equations are coupled with a radially localized global model and an analytical sheath model to investigate the electromagnetic effects under various frequencies and electron powers in large-area very high frequency symmetric capacitive argon discharges.Simulation results indicate that both the vacuum wavelength and the sheath width decrease with frequency,leading to the reduced surface wavelength.As a result,the standing wave effect becomes pronounced,causing the fact that the radial profiles of the electron density,radio frequency voltage,and sheath width shift from uniform over center-high to multiple-node.When the frequency is close to or higher than the series resonance frequency,the surface waves cannot propagate to the radial center because of the significant radial damping.Due to the lack of power deposition near the radial center,the electron density is nearly zero there,i.e.the stop band effect.As power increases,the higher electron density leads to the decrease of the skin depth.Therefore,the importance of the skin effect gradually exceeds that of the standing wave effect,giving rise to the transition from the center-high to edge-high electron density profiles.The method proposed in this work could help to predict the plasma distribution under different discharge conditions in a few minutes,which is of significant importance in optimizing the plasma processing.展开更多
A radio-frequency(RF) inductively coupled negative hydrogen ion source(NHIS) has been adopted in the China Fusion Engineering Test Reactor(CFETR) to generate negative hydrogen ions.By incorporating the level-lumping m...A radio-frequency(RF) inductively coupled negative hydrogen ion source(NHIS) has been adopted in the China Fusion Engineering Test Reactor(CFETR) to generate negative hydrogen ions.By incorporating the level-lumping method into a three-dimensional fluid model,the volume production and transportation of H^(-) in the NHIS,which consists of a cylindrical driver region and a rectangular expansion chamber,are investigated self-consistently at a large input power(40 k W) and different pressures(0.3–2.0 Pa).The results indicate that with the increase of pressure,the H^(-) density at the bottom of the expansion region first increases and then decreases.In addition,the effect of the magnetic filter is examined.It is noteworthy that a significant increase in the H^(-) density is observed when the magnetic filter is introduced.As the permanent magnets move towards the driver region,the H^(-) density decreases monotonically and the asymmetry is enhanced.This study contributes to the understanding of H-distribution under various conditions and facilitates the optimization of volume production of negative hydrogen ions in the NHIS.展开更多
In this work,a two-dimensional hybrid model,which consists of a bulk fluid module,a sheath module and an ion Monte-Carlo module,is developed to investigate the modulation of ion energy and angular distributions at dif...In this work,a two-dimensional hybrid model,which consists of a bulk fluid module,a sheath module and an ion Monte-Carlo module,is developed to investigate the modulation of ion energy and angular distributions at different radial positions in a biased argon inductively coupled plasma.The results indicate that when the bias voltage amplitude increases or the bias frequency decreases,the ion energy peak separation width becomes wider.Besides,the widths of the ion energy peaks at the edge of the substrate are smaller than those at the center due to the lower plasma density there,indicating the nonuniformity of the ion energy distribution function(IEDF)along the radial direction.As the pressure increases from 1 to 10 Pa,the discrepancy of the IEDFs at different radial positions becomes more obvious,i.e.the IEDF at the radial edge is characterized by multiple low energy peaks.When a dual frequency bias source is applied,the IEDF exhibits three or four peaks,and it could be modulated efficiently by the relative phase between the two bias frequencies.The results obtained in this work could help to improve the radial uniformity of the IEDF and thus the etching process.展开更多
基金financially supported by National Natural Science Foundation of China(Nos.12075049 and 11935005)。
文摘The dual cylindrical inductively coupled plasma source,compared to the conventional structure of inductively coupled plasma source,can significantly improve the uniformity of plasma.It has an enhanced potential for application in processes,such as etching and ashing.A uniform plasma can be obtained by allowing the remote plasma from the upper chamber modulate the main plasma generated in the lower chamber.In this study,a fluid model was employed to investigate a dual cylindrical inductively coupled Ar/O_(2)discharge.The effects of external parameters on electron density,electron temperature,O atomic density,and plasma uniformity in the main chamber were studied,and the reasons were analyzed.The results of this study show that remote power can control the plasma uniformity and increase the plasma density in the main chamber.As the remote power increased,plasma uniformity improved initially and then deteriorated.The main power affected the plasma density at the edge of the main chamber and can modulate the plasma density in the main chamber.The gas pressure affected both the uniformity and density of the plasma.As the gas pressure increased,the plasma uniformity deteriorated,but the free radical density improved.
基金supported by National Natural Science Foundation of China(Nos.11905307 and 11875101)the Fundamental Research Funds for the Central Universities(No.DUT21LAB110)the China Scholarship Council。
文摘The effects of coil and dielectric window structures on the plasma distribution are examined in a cylindrically symmetric planar inductively coupled plasma(ICP).A two-dimensional(2 D)fluid model is employed to investigate the design issues of ICP source for etching.When the gradient coil structure is applied at 400 W and 20 mTorr,the ionization rate caused by the power deposition decreases at the reactor center as compared to that in a reactor with a planar coil above the planar dielectric window,and a rather uniform plasma is obtained.However,for the vertical coil geometry,all the coils move to the position of the outermost coil,and the peaks of the power deposition and ionization rate appear at the radial edge of the substrate.In this case,the plasma density is characterized by an edge-high profile.Further,it is observed that the plasma uniformity is improved by increasing the source power under a gas pressure of 20 mTorr and becomes better when the gas pressure increases to 30 mTorr with the source power being fixed at400 W in the gradient coil configuration,but the uniformity of plasma worsens with the rising source power or pressure due to the strong localization in the vertical coil geometry.Moreover,when the discharge is sustained in a reactor with a stepped dielectric window at r=0.135 m,the best plasma uniformity is obtained at 400 W and 20 m Torr because the ionization rate is enhanced at the outermost coil,and the dielectric window at r=0.135 m blocks the diffusion of plasma towards the axis.In addition,higher source power and lower gas pressure produce more uniform plasma for the designs with a stepped window near the symmetry axis.When the dielectric window is stepped at r=0.135 m,the non-uniformity of plasma initially decreases and then increases with the increase in source power or gas pressure.When the dielectric window is stepped at the radial edge of the chamber,the plasma uniformity is improved by increasing the source power and gas pressure due to the enhanced ionization at the larger radius caused by the severe localization.
基金supported by the National Key R&D Program of China(No.2017YFE0300106)National Natural Science Foundation of China(No.12075049)the Fundamental Research Funds for the Central Universities(Nos.DUT20LAB201 and DUT21LAB110)。
文摘In the design of negative hydrogen ion sources,a magnetic filter field of tens of Gauss at the expansion region is essential to reduce the electron temperature,which usually results in a magnetic field of around 10 Gauss in the driver region,destabilizing the discharge.The magnetic shield technique is proposed in this work to reduce the magnetic field in the driver region and improve the discharge characteristics.In this paper,a three-dimensional fluid model is developed within COMSOL to study the influence of the magnetic shield on the generation and transport of plasmas in the negative hydrogen ion source.It is found that when the magnetic shield material is applied at the interface of the expansion region and the driver region,the electron density can be effectively increased.For instance,the maximum of the electron density is 6.7×10^(17)m^(-3)in the case without the magnetic shield,and the value increases to 9.4×10^(17)m^(-3)when the magnetic shield is introduced.
基金supported by National Natural Science Foundation of China(NSFC)(Nos.11935005,11875101,12020101005,12005035)the Natural Science Foundation of Liaoning Province(No.2020-MS-114)+2 种基金the China Postdoctoral Science Foundation(No.2020M670741)the Fundamental Research Funds for the Central Universities(No.DUT20LAB201)financial support from the China Scholarship Council。
文摘In this paper,Maxwell equations are coupled with a radially localized global model and an analytical sheath model to investigate the electromagnetic effects under various frequencies and electron powers in large-area very high frequency symmetric capacitive argon discharges.Simulation results indicate that both the vacuum wavelength and the sheath width decrease with frequency,leading to the reduced surface wavelength.As a result,the standing wave effect becomes pronounced,causing the fact that the radial profiles of the electron density,radio frequency voltage,and sheath width shift from uniform over center-high to multiple-node.When the frequency is close to or higher than the series resonance frequency,the surface waves cannot propagate to the radial center because of the significant radial damping.Due to the lack of power deposition near the radial center,the electron density is nearly zero there,i.e.the stop band effect.As power increases,the higher electron density leads to the decrease of the skin depth.Therefore,the importance of the skin effect gradually exceeds that of the standing wave effect,giving rise to the transition from the center-high to edge-high electron density profiles.The method proposed in this work could help to predict the plasma distribution under different discharge conditions in a few minutes,which is of significant importance in optimizing the plasma processing.
基金supported by the National Key R&D Program of China (No. 2017YFE0300106)National Natural Science Foundation of China (Nos. 11935005 and 12075049)the Fundamental Research Funds for the Central Universities(Nos. DUT21TD104 and DUT21LAB110)。
文摘A radio-frequency(RF) inductively coupled negative hydrogen ion source(NHIS) has been adopted in the China Fusion Engineering Test Reactor(CFETR) to generate negative hydrogen ions.By incorporating the level-lumping method into a three-dimensional fluid model,the volume production and transportation of H^(-) in the NHIS,which consists of a cylindrical driver region and a rectangular expansion chamber,are investigated self-consistently at a large input power(40 k W) and different pressures(0.3–2.0 Pa).The results indicate that with the increase of pressure,the H^(-) density at the bottom of the expansion region first increases and then decreases.In addition,the effect of the magnetic filter is examined.It is noteworthy that a significant increase in the H^(-) density is observed when the magnetic filter is introduced.As the permanent magnets move towards the driver region,the H^(-) density decreases monotonically and the asymmetry is enhanced.This study contributes to the understanding of H-distribution under various conditions and facilitates the optimization of volume production of negative hydrogen ions in the NHIS.
基金financially supported by National Natural Science Foundation of China(Nos.11935005 and 11875101)the Fundamental Research Funds for the Central Universities(No.DUT21LAB110)。
文摘In this work,a two-dimensional hybrid model,which consists of a bulk fluid module,a sheath module and an ion Monte-Carlo module,is developed to investigate the modulation of ion energy and angular distributions at different radial positions in a biased argon inductively coupled plasma.The results indicate that when the bias voltage amplitude increases or the bias frequency decreases,the ion energy peak separation width becomes wider.Besides,the widths of the ion energy peaks at the edge of the substrate are smaller than those at the center due to the lower plasma density there,indicating the nonuniformity of the ion energy distribution function(IEDF)along the radial direction.As the pressure increases from 1 to 10 Pa,the discrepancy of the IEDFs at different radial positions becomes more obvious,i.e.the IEDF at the radial edge is characterized by multiple low energy peaks.When a dual frequency bias source is applied,the IEDF exhibits three or four peaks,and it could be modulated efficiently by the relative phase between the two bias frequencies.The results obtained in this work could help to improve the radial uniformity of the IEDF and thus the etching process.
