| Radio frequency(RF)inductively coupled plasma(ICP)has been widely used in the semiconductor chip manufacturing processes because of the low pressure operation envirornment,high plasma density,simple configuration and so on.With the development of the microelectronics industry,one indispensable tendency is the increase of the wafer size and meanwhile the reduction of the etching linewidth,which triggers pursuit of high performance types of ICP sources.Motivated by these requirements,new types of ICP sources driven by multi-powers are proposed,such as the ICP reactor biased by a direct-current pulse power and dual-frequency dual-coil ICP source etc..The discharge mechanisms of these sources driven by multiple powers are rather complicated,as compared with the conventional ICPs.For controlling and optimizing the plasma processes,it is significant to study the effect of the source parameters on the discharge properties.Therefore,in this thesis,a two-dimensional fluid model is employed to systematically investigate the influence of the source parameters on the plasma characteristics,especially on the plasma uniformity,in a planar ICP reactor.A brief review about the classification of plasmas,the application of low temperature plasmas,as well as several typical RF plasma sources and their characteristics,is given in Chapter 1.In addition,a detailed description of the recent advances of the external parameter effect on the plasma uniformity in the ICP discharge is given.Finally,the contents of Chapters 2-6 are presented separately below.In Chapter 2,there is a thorough introduction to the two dimensional fluid model used in the numerical investigation,which consists of fluid module and electromagnetic module.In the fluid module,the plasma parameters,such as the particle density,the particle flux,the electron temperature,etc.,are obtained by solving the fluid equations.The temporal and spatial distributions of the electromagnetic field generated by the coil are given by the electromagnetic module.Besides,boundary conditions and numerical methods are also introduced.In Chapter 3,the influence of the pulsed direct-current bias power on the RF inductively coupled discharge properties is studied.The results show that the ion density,the inductive power density and the total ion flux at the substrate surface averaged over one pulse period increase with the bias voltage.When the pulse fr-equency of the bias power is high,the power-on time is too short for the plasma to achieve the steady state.As the pulse frequency becomes lower,the steady state can be achieved,and under this condition,the pulse frequency has no significant influence on the total ion flux.In addition,when the bias power is turned off,the ion density at the surface of the substrate first increases to a peak value,and then it decays,for all bias voltages and pulse frequencies investigated.The ICP discharge driven by dual-coil is investigated in chapter 4,and the working gas is argon.The results show that the azimuthal electric field near the inner coil becomes weaker with the decreasing inner coil frequency,whereas the azimuthal electric field near the outer coil is almost unchanged.Besides,the azimuthal electric field near the inner coil increases with the inner coil current.When the influence of the inner coil on the plasma is equivalent to that of the outer coil,the best plasma uniformity can be obtained.In Chapter 5,the effect of the outer coil current and the inner coil pulse duty cycle on the uniformity of an Ar/O2 plasma is investigated.The results show that when the outer coil current increases,the uniformity of the axial positive ion flux and O atom density at the substrate surface averaged over one pulse period becomes better.When the pulse duty cycle is equal to 50%,the best uniformity of positive ion flux is obtained.Besides,the radial uniformity of the O atom density becomes worse with the increase of duty cycle.Finally,the main conclusions of this thesis and the prospects for future work are given in chapter 6. |
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