Experimental Investigations Of Pulse-modulated Radio Frequency Ar/D₂ And Ar/H₂ Inductively Coupled Plasmas

In microelectronic etching process,inductively coupled plasma?ICP?source is one of the most used high-density plasma sources.As the integration of semiconductor chips increases and the critical dimension?CD?of device shrinks,the requirements of the etching process become more and more stringent.To challenge these requirements,the pulse-modulated radio frequency plasmas were proposed.The reason is during the pulse-off periods in pulse-modulated radio frequency plasmas,the negative ions would diffuse to the substrate,and then neutralize the positive ions accumulated on the trenches,in this way,the plasma induced damage would be weaken.Moreover,D₂,H₂,Ar/D₂ and Ar/H₂ plasmas are used widely.In detail,Ar/H₂ plasmas are always applied to graphene deposition,transistor doping,and the control of hydrocarbon surface properties.H₂ plasmas are generally used in microelectronic processes,such as the surface cleaning,etching,oxide removal,film deposition,However,D₂ and H₂ plasmas have important applications in neutral beam heating in nuclear fusion devices.Therefore,the pulse-modulated radio frequency D₂,H₂,Ar/D₂ and Ar/H₂ ICPs are investigated in this paper.Using commercial Langmuir probes,the temporal evolution of electron density,effective electron temperature,and electron energy distribution function?EEDF?is experimentally measured under different discharge conditions in the discharge center.The experimental results show that the temporal evolution of the electron density and temperature in D₂,H₂,Ar/D₂ and Ar/H₂ ICPs is similar over a pulse period.For the time-resolved electron density,when the pulse is switched on,the electron density rises rapidly until it arrives at the value in the steady state.When the pulse is turned off,the electron density increases to a maximum within a short time.After that,it decreases rapidly and then decays slowly.As for the effective electron temperature,when the pulse is switched on,it increases rapidly to a maximum value,and then decreases to a constant value.After that,it almost keeps constant.When the pulse is turned off,the effective electron temperature rises and then drops to a minimum,subsequently,it almost keeps constant.In addition,in pulse-modulated radio frequency D₂ and H₂ ICPs,during the steady state,the electron density almost increases linearly with the power increasing,however,as the pressure increases,the electron density increases firstly and then decreases.The effective electron temperature changes little with the power increasing but decreases directly with the pressure increasing.In Ar/D₂ and Ar/H₂ ICP,as the Ar content increases,the electron density increases slowly and then rises rapidly.Meanwhile,the trends of the electron temperature with the Ar content are similar to the electron density.However,in continuous wave Ar/D₂ plasmas,with the increase of Ar ratio,the electron density increases,but the electron temperature decreases.