Two-dimensional ion flux distributions in inductively coupled plasmas: Effect of adding electronegative gases to Ar

Kim, Tae Won; Aydil, Eray S.

doi:10.1063/1.1517733

Cited by 6 publications

(8 citation statements)

References 29 publications

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“…The data shown in Fig. 7 were extracted from 2-D ion flux distributions in Ar, Cl and SF discharges published previously [24]. Calculated ion flux distributions are in good agreement with the measured ion flux profiles indicating that the model and scaling method using the relative magnitudes of electron impact cross sections captures the changes in the ion flux uniformity in pristine Cl and SF discharges.…”

Section: Ion Flux Distribution In CL and Sf Dischargessupporting

confidence: 53%

“…the skin depth in an Ar discharge maintained at 10 mtorr and 200-W rf power is taken to be [10], [29] cm and the skin depths in other discharges and conditions are scaled inversely with the square root of the spatially averaged charge density determined from the ion flux probe array [24]. In strongly electronegative discharges, ion density may not equal the electron density and in these cases our method would underestimate the skin depth.…”

Section: A Model Assumptions and Equationsmentioning

confidence: 99%

“…The experiments were conducted in a high-density inductively coupled plasma (ICP) etching reactor described previously in detail [22]- [24]. Briefly, radio frequency (rf) power at 13.56 MHz is inductively coupled to the plasma using a planar spiral coil seated on a quartz window at the top of the vacuum chamber.…”

Section: A Inductively Coupled Plasma Etching Reactormentioning

confidence: 99%

“…A 2-D array of planar Langmuir probes built on a 200-mm-diameter wafer was used to determine spatial distribution of ion flux impinging on the wafer surface [23], [24]. Briefly, this array consists of twenty-two 8-mm-diameter circular probes patterned on a polyimid board using conventional printed circuit board fabrication techniques.…”

Section: B On-wafer Ion Flux Probe Arraymentioning

confidence: 99%

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Experimental and theoretical study of two-dimensional ion flux uniformity at the wafer plane in inductively coupled plasmas

Kim

Aydil

2003

IEEE Trans. Plasma Sci.

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A two-dimensional array of planar Langmuir probes manufactured on a 200-mm-diameter silicon wafer was used to measure the spatial distribution of ion flux impinging on the wafer surface in various discharges of electropositive (Ar) and electronegative (SF 6 and Cl 2 ) gases maintained in an inductively coupled plasma etching reactor with a planar spiral coil. In conjunction with the experiments, a two-dimensional fluid model of the plasma was developed to capture the dependence of the ion flux uniformity on plasma operating parameters and reactor geometry through a set of dimensionless numbers which are the ratios of various time and length scales intrinsic to the discharge. These dimensionless ratios include reactor dimensions, the skin depth, the electron energy relaxation length, ion diffusion length, and ionization and attachment rates. The model provides a simple framework within which the spatial variation of ion flux in inductively coupled plasmas can be understood. The approach captures the dependence of ion flux uniformity on plasma operating variables such as pressure and feed gas composition.Index Terms-Chlorine plasma, discharge modeling, electronegative discharge, inductively coupled plasma, ion flux probe, langmuir probe, plasma etching, plasma uniformity, sulfur hexafluoride plasma.

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Section: Ion Flux Distribution In CL and Sf Dischargessupporting

confidence: 53%

Section: A Model Assumptions and Equationsmentioning

confidence: 99%

Section: A Inductively Coupled Plasma Etching Reactormentioning

confidence: 99%

Section: B On-wafer Ion Flux Probe Arraymentioning

confidence: 99%

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Experimental and theoretical study of two-dimensional ion flux uniformity at the wafer plane in inductively coupled plasmas

Kim

Aydil

2003

IEEE Trans. Plasma Sci.

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“…Many of the inductively coupled plasma ͑ICP͒ systems used for etching and deposition have discrete nozzles or single sided asymmetric pumping. 6,7 These systems were designed assuming that at low pressure, transport is diffusion dominated and so the gas sources and sinks appear as volume averages. As such, their asymmetries should not adversely affect the uniformity of reactants to the substrate.…”

Section: Introductionmentioning

confidence: 99%

Pulsed plasmas as a method to improve uniformity during materials processing

Subramonium

Kushner

2004

Journal of Applied Physics

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Continuous wave operation of inductively coupled plasma ͑ICP͒ reactors as used for materials processing and which have geometrical or flow asymmetries may produce asymmetric species densities, temperatures, and fluxes. Flow asymmetries that produce nonuniformities in plasma conductivity initiate a positive feedback loop. In this feedback loop, asymmetries in conductivity are reinforced by the resulting nonuniform power deposition, which causes electron impact ionization to also be nonuniform. In this article, we discuss results from a computational investigation of long-term transients during pulsed operation of ICPs and their consequences on side-to-side asymmetries in plasma properties. During pulsed operation, diffusion of charged species during the afterglow between pulses smoothens these asymmetries prior to the next power pulse. The power deposition during subsequent pulses is more symmetric and this reduces the positive feedback. The improvement in uniformity afforded by pulsing is determined by the intrapulse plasma dynamics, and so is a function of the pulse repetition frequency, duty cycle, and feedstock gas. Improvements in the azimuthal uniformity of reactant densities were obtained in Ar and Cl 2 plasmas in an asymmetrically pumped reactor using pulsed power. As dissociative attachment dominates in the afterglow of Cl 2 pulsed plasmas, it provides a more uniform sink for electrons compared to ambipolar diffusion and different systematic behavior is obtained compared to argon.

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Pulsed inductively coupled plasmas as a method to recoup uniformity: Three-dimensional modeling study

Subramonium

Kushner

2004

Applied Physics Letters

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High plasma density sources such as inductively plasmas (ICPs) are commonly used for microelectronics fabrication. Design constraints often result in systems which have asymmetric gas pumping which can in turn produce azimuthal nonuniformities in plasma properties. These asymmetries are reinforced by a positive feedback between nonuniformities in conductivity and power deposition. In this letter, we discuss computational results from a three-dimensional model for pulsed operation of ICPs sustained in argon as a means to recoup azimuthal symmetry of plasma properties which may result from asymmetric pumping. We found that azimuthally asymmetric plasma properties produced by continuous operation gradually become more uniform during pulsed operation due to the interruption of the positive feedback and allowing interpulse diffusion to smooth asymmetries.High plasma density sources, such as inductively coupled plasmas (ICPs) are commonly used for microelectronics fabrication. 1-5 Due to design constraints, ICP systems often have discrete nozzles or single-sided pumping. 6,7 Previous experimental 7,8 and computational investigations 9,10 of ICP reactors showed that asymmetric pumping may result in azimuthally asymmetric species densities and fluxes which ultimately translate to, for example, nonuniform etch or deposition yields. These geometric and flow asymmetries become more critical as wafer sizes increase. 11 Flow-induced nonuniformities in densities can feedback and intensify through the plasma conductivity. Feedback through the nonuniform conductivity makes the power deposition nonuniform, which in turn results in nonuniform electron impact ionization sources and plasma conductivity. Thus, the nonuniform power deposition reinforces the flowinduced asymmetries. Pulsed operation of ICPs may be a means to recoup azimuthal uniformity by breaking this positive feedback and mediating asymmetries by diffusion during the afterglow following power pulses. These processes provide a more azimuthally uniform set of initial conditions for the subsequent power pulses. In this letter, we discuss results from a three-dimensional (3D) computational investigation of pulsed ICPs.The model employed in this investigation is a moderately parallel implementation of the 3D Hybrid Plasma Equipment Model (HPEM3D). 10 The plasma transport and numerical algorithms used in HPEM3D are extensively discussed in Ref. 12. The parallel hybrid model employs "task parallelism" to simultaneously execute different modules of the HPEM3D on three processors of a symmetric multiprocessor computer having shared memory. As such, the model is the 3D analogue of the two-dimensional parallel model described in Ref. 13. The modules executed in parallel are the electromagnetics module, the electron energy transport module and the fluid kinetics module. Plasma properties from these modules are frequently exchanged in shared memory without interrupting the time evolving calculation being performed in other modules.Pulsed operation of ICPs was recently reviewed in...

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Two-dimensional ion flux distributions in inductively coupled plasmas: Effect of adding electronegative gases to Ar

Cited by 6 publications

References 29 publications

Experimental and theoretical study of two-dimensional ion flux uniformity at the wafer plane in inductively coupled plasmas

Experimental and theoretical study of two-dimensional ion flux uniformity at the wafer plane in inductively coupled plasmas

Pulsed plasmas as a method to improve uniformity during materials processing

Pulsed inductively coupled plasmas as a method to recoup uniformity: Three-dimensional modeling study

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