3D numerical simulation of gas heating effects in a magnetron sputter deposition system

Ekpe, Samuel D.; Dew, S. K.

doi:10.1088/0022-3727/39/7/012

Cited by 20 publications

(14 citation statements)

References 25 publications

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“…This claim has been experimentally confirmed by Rossnagel, 2 who reports a maximum gas reduction of 85% at 3 kW input power and by the simulations reported in Ref. 3.…”

Section: Introductionsupporting

confidence: 63%

“…They include the combination of an experimental and global energy balance modeling, 2 a non-selfconsistent Monte Carlo ͑MC͒ simulation, 5 a theoretical approach, 6 and a non-self-consistent, fluid heat flow calculation. 3 Only the last work is not one dimensional. The main uncertainties in these papers are the estimated ͑as-sumed͒ number of collisions, both in the volume and at the cathode, as well as their spatial distribution.…”

Section: Introductionmentioning

confidence: 99%

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Calculation of gas heating in a dc sputter magnetron

Kolev

Bogaerts

2008

Journal of Applied Physics

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The effect of gas heating in laboratory sputter magnetrons is investigated by means of numerical modeling. The model is two-dimensional in the coordinate space and three-dimensional in the velocity space based on the particle-in-cell-Monte Carlo collisions technique. It is expanded in a way that allows the inclusion of the neutral plasma particles ͑fast gas atoms and sputtered atoms͒, which makes it possible to calculate the gas temperature and its influence on the discharge behavior in a completely self-consistent way. The results of the model are compared to experimental measurements and to other existing simulation results. The results show that gas heating is pressure dependent ͑rising with the increase in the gas pressure͒ and should be taken into consideration at pressures above 10 mTorr.

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“…This claim has been experimentally confirmed by Rossnagel, 2 who reports a maximum gas reduction of 85% at 3 kW input power and by the simulations reported in Ref. 3.…”

Section: Introductionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Calculation of gas heating in a dc sputter magnetron

Kolev

Bogaerts

2008

Journal of Applied Physics

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“…It is obvious that increasing the pressure results in the diminution of the mean free path of Cu atoms in argon, thus favoring their diffusion to the chamber sidewalls and reducing the flux of Cu atoms to the substrate. But an enhancement of the plasma density with increasing pressure has been observed experimentally 12,13 , or predicted theoretically 37 , which consequently should increase the ion flux to the target and thus the sputtering rate of the copper. Unfortunately, using a Langmuir probe, we have not been able to carry out reliable electron density measurements in this magnetized plasma to ascertain this fact but we believe that this hypothesis should be correct.…”

Section: -Deposition Ratementioning

confidence: 92%

“…This behavior is attributed to the enhancement of the plasma density with both argon pressure and magnetron discharge power. So, the ground state Cu atoms are efficiently excite to the 2 D 5/2 metastable state, the electron temperature in the range of 1.5 -4.5 eV 12,13,15,37 being high enough for an efficient excitation of the 2 D 5/2 state, whose threshold is 1.39 eV 35 . Moreover, with the 2.2 x 10 11 cm -3 density of Cu ( 2 S 1/2 ) atoms measured at the highest pressure and power used in this work (14 µbar and 200 W), the mean free path of 324.7 nm photons is about 5 cm, much smaller than the about 20 cm plasma dimensions.…”

mentioning

confidence: 99%

Measured density of copper atoms in the ground and metastable states in argon magnetron discharge correlated with the deposition rate

Naghshara¹,

Sobhanian²,

Khorram³

et al. 2010

J. Phys. D: Appl. Phys.

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Abstract:In a dc-magnetron discharge with argon feed gas, densities of copper atoms in the ground state Cu( 2 S 1/2 ) and metastable state Cu*( 2 D 5/2 ) were measured by resonance absorption technique, using a commercial hollow cathode lamp as light source. The operating conditions were 0.3 -14 µbar argon pressure and 10 -200 W magnetron discharge power. The deposition rate of copper in a substrate positioned at 18 cm from the target was also measured with a quartz microbalance. The gas temperature, in the range of 300 to 380 K, was deduced from the emission spectral profile of N 2 (C 3 Π u − B 3 Π g ) 0-0 band at 337 nm when trace of nitrogen was added to the argon feed gas. The isotope-shifts and hyperfine structures of electronic states of Cu have been taken into account to deduce the emission and absorption line profiles, and hence for the determination of atoms densities from the measured absorption rates. To prevent error in evaluation of Cu density, attributed to the line profile distortion by autoabsorption inside the lamp, the lamp current was limited to 5 mA. Density of Cu( 2 S 1/2 ) atoms and deposition rate both increased with the enhanced magnetron discharge power but at fixed power the copper density augmented with argon pressure whereas the deposition rate followed the opposite trend. Whatever the gas pressure, the density of Cu*( 2 D 5/2 ) metastable atoms remained below the detection limit of 1 x 10 10 cm -3 for magnetron discharge powers below 50 W and hence increased much rapidly than the density of Cu( 2 S 1/2 ) atoms, over passing this later at some discharge power, whose value decreases with increasing argon pressure. This behavior is believed to result from the enhancement of plasma density with increasing discharge power and argon pressure, which would increase the excitation rate of copper into metastable states. At fixed pressure, the deposition rate followed the same trend than the total density of copper atoms in the ground and metastable states. Two important conclusions of this work are: i) copper atoms sputtered from the target under ion bombardment are almost all in the ground state Cu( 2 S 1/2 ) and hence in the plasma volume they can be excited into the metastable states; ii) all atoms in the long-lived ground and metastable states contributes to the deposition of copper layer on the substrate.a Corresponding author ; E-mail : nader.sadeghi@ujf-grenoble.fr 2 1-IntroductionMagnetron discharges are widely used for thin film deposition in surface treatment 1, 2 , magnetic and superconducting devices 3 , semiconductor industry 4 and in surface coating engineering of materials under low temperature conditions 5,6 . In these systems, the magnetic field, usually produced by placing permanent magnets behind the cathode, confines the plasma in the near cathode region, reducing the electron loss to the sidewalls. By increasing the ionization rate near the cathode, which is also the target to be sputtered, its confinement helps to maintain the plasma at much lower buffer gas pressure than...

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“…Within the plasma region, the collisions between the NPs and the energetic electrons and Ar + species acts as a source of heat, slowing down the cooling rate of the NPs. [36] When the NPs exit this region, their temperature decreases very sharply. Secondly, it is worth noting that the formed NPs travel with the gas flow in the nanocluster source, and thus the velocity of the NPs is proportional to the gas flow rate.…”

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confidence: 99%

Direct Gas‐Phase Synthesis of Heterostructured Nanoparticles through Phase Separation and Surface Segregation

Wang

2008

Advanced Materials

111

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Heterostructured nanoparticles (NPs) offer great opportunities for applications in areas such as biomedicine, renewable energy, information processing, and data storage by virtue of their embedded multiple functionalities and enhanced magnetic, [1,2] optical, [3] and catalytic performance [4] arising from the interactions of the individual components within the NPs.To understand the fundamental nature of these interactions, as well as to utilize them more efficiently, it is imperative to develop synthesis methods to prepare heterostructured NPs with high-quality interfaces and surfaces. Several heterostructures have been synthesized by the seed-growth approach using wet chemical methods, [5][6][7][8][9] sometimes followed by a chemical vapor deposition (CVD) process. [10,11] However, solution-based approaches make it difficult to obtain contamination-free interfaces and surfaces. Moreover, the integration of solution-synthesized NPs into vacuum-based micro-and nanoelectronics fabrication processes has been remarkably challenging. On the other hand, gas-phase techniques have the intrinsic merit of producing a clean interface and surface, yet only a few attempts have been made to produce heterostructured NPs [12][13][14] other than the widely reported core/shell NPs consisting of metal cores surrounded by an oxide shell of the same metal.[1] Here, we demonstrate that binary metallic (Au-Co and Ag-Fe) NPs with distinctively different heterostructures at the single-particle level can be prepared directly in the gas phase via phase separation and surface segregation. This synthesis approach is ultra high vacuum (UHV) compatible, and yields high quality interfaces and surfaces; the synthesized NPs can also be made water soluble [15] and functionalized for further chemical processing. This approach can also be extended to various other material systems such as alloys and semiconductors. [13] In this work, we have selected a combination of ferromagnetic elements (Co or Fe) and noble metals (Au or Ag) as the model system. Several characteristic properties make this system a good starting point for the synthesis of heterostructured NPs. For instance, at room temperature Co and Au do not alloy and readily phase separate in the bulk form or clusters of more than several hundred atoms. [16,17] The ferromagnetic elements have a smaller atomic size than the noble metals. Consequently, the mismatch in atomic size causes the strain energy to increase when the atoms are mixed as compared to the lower energy segregated state.[18] The ferromagnetic elements generally have a higher surface energy than the noble metals (Co (111) 3.23 J m -2 , Au (111) 1.61 J m -2 ), [19] which makes it more preferable for the noble metals to be present at the surface and leads the system towards surface segregation. Numerical simulations of binary metal NPs also suggest that noble metals are energetically favored to be present at the surface as compared to transition metals. [18,20] Though the combination of phase separation and large differences in s...

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3D numerical simulation of gas heating effects in a magnetron sputter deposition system

Cited by 20 publications

References 25 publications

Calculation of gas heating in a dc sputter magnetron

Calculation of gas heating in a dc sputter magnetron

Measured density of copper atoms in the ground and metastable states in argon magnetron discharge correlated with the deposition rate

Direct Gas‐Phase Synthesis of Heterostructured Nanoparticles through Phase Separation and Surface Segregation

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