2.45-GHz microwave plasma sources using solidstate microwave generators. Collisional-type plasma source

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1 Journal of Microwave Power and Electromagnetic Energy ISSN: (Print) (Online) Journal homepage: GHz microwave plasma sources using solidstate microwave generators. Collisional-type plasma source Louis Latrasse, Marilena Radoiu, Juslan Lo & Philippe Guillot To cite this article: Louis Latrasse, Marilena Radoiu, Juslan Lo & Philippe Guillot (2017): 2.45-GHz microwave plasma sources using solid-state microwave generators. Collisional-type plasma source, Journal of Microwave Power and Electromagnetic Energy, DOI: / To link to this article: Published online: 09 Mar Submit your article to this journal Article views: 8 View related articles Full Terms & Conditions of access and use can be found at Download by: [ ] Date: 17 March 2017, At: 02:34

2 JOURNAL OF MICROWAVE POWER AND ELECTROMAGNETIC ENERGY, RESEARCH ARTICLE 2.45-GHz microwave plasma sources using solid-state microwave generators. Collisional-type plasma source Louis Latrasse a, Marilena Radoiu a, Juslan Lo b and Philippe Guillot b a Sairem SAS, Neyron, France; b Plasma Diagnostic Research Team, CUFR Jean François Champollion, Albi, France ABSTRACT The availability of high power solid-state microwave generators opens new directions in plasma generation with applications in industrial plasma processing at low pressure. The optimization of the plasma production line, i.e. from the microwave generator to the plasma source, is a requisite to enable the scaling-up while ensuring a robust control of the equipment. In addition to the electron cyclotron resonance (ECR) coaxial microwave plasma source previously reported, a collisional plasma source was developed for processing at Pa. Similar to the ECR plasma source, the results of measurements performed with the collisional plasma source demonstrate that plasma density and uniformity are highly dependent on the microwave power, the reactor pressure and the distance to and between plasma sources. It was demonstrated that the collisional plasma source can attain very high plasma densities, i.e. >10 12 cm 3 in argon and >10 11 cm 3 in molecular gases like O 2, N 2, air, H 2, making it suitable for high deposition rate plasma-enhanced chemical vapour deposition or for high density production of reactive species. A comparison of the two microwave plasma sources is given for the main plasma parameters; the choice of one plasma source over the other depends on the intended process/operating pressure. ARTICLE HISTORY Received 29 October 2016 Accepted 7 February 2017 KEYWORDS Microwave plasma; collisional plasma; solid-state microwave generator; plasma source; Langmuir probe; optical emission spectroscopy 1. Introduction The advantages of microwave plasma in the context of industrial processing (thin film deposition, diamond deposition, etc.) are already known (Moisan & Pelletier 2006). Industrial demand for large scale plasma surface processing requires for plasma sources with increased performance in terms of control, density and uniformity over a wide area of operation. In this context, it was demonstrated that systems based on multiple plasma sources consisting of power dividers fed by magnetron-based generators do not allow for a good control of the microwave power distributed to each plasma source. As already discussed in our previous paper (Latrasse et al., 2017), the recent development of high power solid-state (transistor) microwave generators enables the development of a different CONTACT Louis Latrasse 2017 International Microwave Power Institute llatrasse@sairem.com

3 2 L. LATRASSE ET AL. concept of matched plasma sources that should make it easier to comply with present industrial requirements. When required to operate at very low pressure, Pa, and due to the fact that electron cyclotron resonance (ECR) heating mechanisms are very efficient within this pressure range, especially designed ECR microwave plasma sources operated by either magnetrons (Bechu et al. 2009; Latrasse et al. 2013) or by solid-state generators (Latrasse et al. 2017) have demonstrated to attain very high and uniform plasma densities >10 11 cm 3 in Ar, O 2,N 2 and air. However, when the operating pressure increases the ECR heating mechanism decreases up to its cancellation (when collision frequency n = angular frequency v 0 ) (Moisan & Pelletier 2006). Therefore, at low operating pressures, plasma applications are limited to processes that require high ion assistance, e.g. plasma-based ion implantation, anisotropic etching or sputtering (Bechu et al. 2004). Processes at higher pressure that require high concentration of reactive species such as plasma-enhanced chemical vapour deposition with high deposition rates or isotropic etching (e.g. resist stripping) call for the development of uniform plasmas in the collisional regime. Contrary to the ECR mechanism that is well suited when the electron collision frequency is small compared to the angular frequency of the applied electric field, in the collisional regime the energy gained by the electrons is mainly the one imparted during collisions. Without magnetic field, the work of an electron on a full period of the applied microwave field is zero. Consequently the maximum transfer efficiency is obtained for n = v 0, when an electron has the highest chance to gain maximum energy of the electric field while having maximum probability to have a collision on the period of the wave. At low pressure, when n << v 0, the duration between two collisions is high, meaning that the probability to gain maximum energy of the electric field is high but the probability to have a collision is low. At high pressure, when n >> v 0, the probability to gain maximum energy of the electric field is low due to high collision frequency but the probability to have a collision during a period of the wave is high. In practice, the ideal condition is obtained at mbar pressures, mbar ( Pa), depending on the gas but it is generally preferable to work at slightly lower pressure to favour the diffusion of plasma species and increase the penetration depth of the electromagnetic wave in the plasma. The obtained plasmas are generally overdense (n > n c ); it can be assumed that plasma is produced by the microwave electric field delivered at the dielectric plasma interface and thus imposed on the plasma. The electric field can be assumed strongly attenuated over a characteristic length equal to the skin depth: sffiffiffiffiffiffiffiffiffiffiffi 2 d ¼ (1) svm 0 where m 0 is the vacuum permeability and s is the conductivity s ¼ v pee 0 n þ iv (2) The skin depth is» few millimetres in our conditions; typically d» mm for plasma density at the interface with the dielectric n» cm 3 and f 0 = 2.45 GHz. The complete absence of radiative power outside the reactor, particularly through the Pyrex window, supports this hypothesis.

4 JOURNAL OF MICROWAVE POWER AND ELECTROMAGNETIC ENERGY 3 Figure 1. (a) Collisional-type microwave plasma source; (b) multisource reactor consisting of 8 off plasma sources. Photo in nitrogen, total microwave power 1600 W, 10 Pa. The solution proposed in this paper is a new elementary plasma source operating in the collisional regime, without magnets, able to produce a sheet of high density and uniform plasma in the Pa pressure range. By design, the plasma source avoids power-loss within the source and can be easily matched overwide operating conditions (Latrasse et al. 2012). 2. Experimental The coaxial antenna based on collisional heating Figure 1(a), was designed to be selfadapted once the plasma ignited and to avoid power-loss within the structure, to sustain plasmas from 10 2 mbar up to 1 mbar and to reach plasma densities from to cm 3 at 10 cm from the source depending on the gas in multisource configuration Figure 1(b). The experimental set-up used in this study consists of a multisource plasma reactor within which max. 9 off plasma sources were installed; each plasma source was connected to its own microwave solid-state generator, max. microwave (MW) power 200 W, which produces a wave with variable frequency from 2.43 to 2.47 GHz (100 MHz step) Figure 2. This set-up allows to control both the transmitted microwave power to each plasma source by 1 W increment and the process parameters. Microwave plasma parameters were measured with a Langmuir probe placed at two heights, d = 85 and 160 mm, from the plasma sources; a step motor moves the probe linearly in direction z from position 0 to 500 mm to enable the evaluation of spatial resolved plasma parameters, i.e. plasma density, electron temperature and uniformity. In parallel, the plasma optical emission was channelled through a 200 mm fibre optic and measured with a spectrometer in the nm range. The optical fibre was always placed at 85 mm from the plasma source plane. 3. Results and discussion 3.1. Plasma density and optical emission lines A total of 9 off plasma sources have been distributed inside the multisource reactor in a 3 3 square lattice matrix configuration, lattice mesh 82.5 mm. Each plasma source was

5 4 L. LATRASSE ET AL. Figure 2. Schematic of the multiple collisional plasma reactor. operated at 200 W microwave (MW) power, i.e W total power; the plasma density was measured at d = 85 and 160 mm. This set-up has been used for the measurements of argon, oxygen and nitrogen plasma Argon plasma The variation of the plasma density as a function of the pressure in argon for 9 off plasma sources is shown in Figure 3(a) for d = 85 and 160 mm. Plasma density reaches cm 3 at 5 Pa, d = 85 mm and 1800 W total microwave power; plasma density decreases above 5 Pa. At fixed pressure, for example 4 Pa Figure 3(b), the plasma density increases linearly with the microwave power at both d = 85 and 160 mm: from to cm 3 when the power increases from 450 to 1800 W at d = 85 mm. The intensity of electron excitation of the 750 nm lines of argon is presented in Figure 3 (c). The variation of the intensity follows the variation of the plasma density Oxygen plasma The variation of the plasma density as a function of the oxygen pressure for 9 off plasma sources is plotted in Figure 4(a). It can be seen that at 5 Pa the maximum plasma density reaches cm 3 at d = 85 mm and cm 3 at d = 160 mm. The density reaches a plateau between 6 and 11 Pa, showing that despite the pressure increase and diffusion distance decrease, the plasma density remains stable. This is an indication of more charged particles in the proximity of the plasma sources, in the absorption zone of the electric field. Consequently, working at higher pressure can potentially be very interesting at lower distance from the plasma source plane. As shown in Figure 4(b), at 5 Pa constant pressure, the plasma density increases linearly with the microwave power whatever the distance from the sources.

6 JOURNAL OF MICROWAVE POWER AND ELECTROMAGNETIC ENERGY 5 Figure 3. (a) Argon plasma density vs. pressure, d = 85 and 160 mm, 1800 W; (b) argon plasma density vs. MW power at d = 85 and 160 mm, 4 Pa; (c) argon intensity line 750 nm vs. pressure; 1800 W.

7 6 L. LATRASSE ET AL. Figure 4. (a) Oxygen plasma density vs. pressure, d = 85 and 160 mm, 1800 W; (b) oxygen plasma density vs. MW power at d = 85 and 160 mm; 5 Pa; (c) oxygen intensity lines 777 and 844 nm vs. pressure, 1800 W.

8 JOURNAL OF MICROWAVE POWER AND ELECTROMAGNETIC ENERGY 7 The variation of the electron excitation intensity of the 777 mm and 844 nm lines of oxygen is presented in Figure 4(c). This plot shows that both lines follow the variation of the plasma density Nitrogen plasma The variation of the nitrogen plasma density measured as a function of the pressure is represented in Figure 5(a) at d = 85 and 160 mm; the total microwave power was 1800 W. The maximum plasma density reaches cm 3 at d = 85 mm and cm 3 at d = 160 mm at 5 Pa. As shown in Figure 5(b), the plasma density increases linearly with the microwave power at 5 Pa whatever the distance d. The intensity of electron excitation of the 337, 357 and 390 nm lines of nitrogen is presented in Figure 5(c). The intensity variation of all the lines follows the variation of the plasma density. As for oxygen, a plateau can be observed between 7 and 12 Pa, reflecting an increase in the creation of both excited and charged particles in the absorption zone of the electric field, compensated by the reduced diffusion at higher pressure. Working at higher pressure can also be very interesting at shorter distance from the source s plane Plasma uniformity In this section, the collisional plasma sources were distributed in different configurations schematically represented for each measurement: plasma sources used for the measurement are coloured in red and their relative position to the Langmuir probe is represented. Measurements were performed with 4 off to 9 off plasma sources at distances from the source plane of 85 and 160 mm in several gases matrix configuration 4 off plasma sources were distributed in 2 2 matrix configuration. Each source is supplied with 200 W microwave power, i.e. 800 W total microwave power. Measurements in argon were performed at d = 85 and160 mm for lattice mesh a = 116 and 165 mm as shown in Figure 6. For easier understanding the results are also summarized in Table 1. Figure 6 and Table 1 show that lattice mesh a = 116 mm allows to reach high plasma density and good uniformity at low distance d from the source and over a small area diameter. When the distance from the source plane increases to 160 mm the uniformity decreases due to species that diffuse to the centre of the matrix. Increasing the lattice mesh to a = 165 mm leads to lesser uniformity close to the source plane but increased uniformity at higher distance from the source plane, i.e. 1.6% over 200 mm area diameter at d = 160 mm. To summarize, the increase of the lattice mesh decreases the maximum plasma density but increases the plasma uniformity over higher diameters at higher distance from the source plane; the decrease of the lattice mesh allows to reach very high and uniform plasma density close to the source plane but over reduced diameters. The two peaks obtained at a = 165 mm and d = 85 mm are due to the fact that the lattice mesh is much higher than the distance d. For a = 116 mm, these peaks are not visible at d = 85 mm but they appear at a shorter distance from the source. We can also conclude that the smaller the lattice mesh the closer to the source s plane the processing must be performed in order

9 8 L. LATRASSE ET AL. Figure 5. (a) Nitrogen plasma density vs. pressure; d = 85 and 160 mm, 1800 W; (b) nitrogen plasma density vs. MW power at d = 85 and 160 mm; 5 Pa; (c) intensity of 337, 357 and 390 nm nitrogen lines vs. pressure, 1800 W.

10 JOURNAL OF MICROWAVE POWER AND ELECTROMAGNETIC ENERGY 9 Figure 6. Argon plasma density at d = 85 and 160 mm for lattice mesh a = 116 and a = 165 mm. Table 1. Argon plasma distribution uniformity for 4 collisional plasma sources in matrix configuration; d = 85 mm and d = 160 mm, 5 Pa, 200 W / source, lattice mesh a = 116 mm and 165 mm. 4 off plasma sources Lattice mesh a = 116 mm Lattice mesh a = 165 mm 200 W/source d =85mm d = 160 mm d =85mm d = 160 mm Uniformity (%) Diameter (mm) to increase both the plasma uniformity and its diameter. Good uniformity starts to be obtained at a distance from the source plane lower than the lattice mesh, d << a. By extrapolation, uniform plasma can be obtained without any scale limitation: with a high number of plasma sources, high density and uniform plasma can be obtained close to the source plane. With a low number of plasma sources and increased lattice mesh, uniform but low density plasma can be obtained at higher distance from the source plane. As an example, to extrapolate the above results to 8 off plasma sources, we plotted the sum of the density profiles previously obtained at fixed distance d = 85 and 160 mm for a = 116 and165 mm Figure 7. Uniformity of 3% can be obtained over 170 mm area diameter at d = 85 mm with cm 3 plasma density. On the same surface, 6% uniformity is obtained at d = 160 mm or 3% uniformity over 120 mm area diameter. This supports our earlier conclusion that increasing the number of plasma sources and their distribution compactness lead to increased plasma uniformity and uniformity diameter matrix configuration The argon plasma density obtained with 9 off plasma sources is plotted in Figure 8 at d = 85 and 160 mm, 5 Pa and 1800 W total microwave power. The plasma density reaches cm 3 at d = 85 mm. As expected, due to the high distribution compactness, the obtained plasma uniformity over large area diameters is low. For example, at d = 85 mm the plasma uniformity is 1.95%, 120 mm diameter and at d = 160 mm the plasma uniformity is 3.5%, 120 mm diameter. For easier understanding, the results for argon, nitrogen and oxygen are summarized in Table 2. For all tested gases with the plasma sources

11 10 L. LATRASSE ET AL. Figure 7. Argon plasma density for an extrapolation of 8 off plasma sources; 5 Pa, 1600 W. Figure 8. Argon plasma density profile at d = 85 and 160 mm from the source. distributed in 3 3 matrix configuration; we can conclude that higher plasma uniformity and higher uniformity diameter can be obtained closer to the source plane where the influence of two consecutive plasma sources is diminished. Recent results (Antonin, Latrasse, et al. 2015; Antonin, Taylor, et al. 2015) have shown that uniform deposition of nanocrystalline diamond on 4 00 diameter can be obtained in H 2 CH 4 at d =50mmfromsource plane using solely 4 off collisional sources in matrix configuration and lattice mesh a = 8cm. Table 2. Distribution uniformity obtained with 9 off collisional plasma sources in 3 3 matrix configuration in argon, oxygen, nitrogen at d = 85 and 160 mm, 5 Pa, 200 W/source. 9 off plasma sources d =85mm d = 160 mm 200 W/source Argon Oxygen Nitrogen Argon Oxygen Nitrogen Uniformity (%) Diameter (mm) Note: To increase the plasma distribution uniformity is necessary to decrease the charged species production in the centre of the matrix; to evaluate this possibility the circular network configuration has been further investigated.

12 JOURNAL OF MICROWAVE POWER AND ELECTROMAGNETIC ENERGY Circular network configuration For the evaluation of plasma density and uniformity in a circular network, 8 off collisional plasma sources were tested. The microwave power supplied to each source is 200 W, pressure 5 Pa. The radius of the circular configuration is mm (247 mm diameter). The plasma density profiles are plotted in Figure 9(a) (d) for argon, oxygen, nitrogen and air. Argon plasma uniformity of 4% at d = 85 mm and 5% at d = 160 mm over 250 mm area diameter was obtained. Similarly, oxygen plasma uniformity of 1.65% at d = 85 mm and 1.8% at d = 160 mm over 250 mm area diameter was measured. Nitrogen plasma uniformity of 1.9% at d = 85 mm and 2.8% at d = 160 mm was obtained while in air, the uniformity was 2.25% at d = 85 mm and 2.5% at d = 160 mm. Results for all tested gases are summarized in Table 3. Whatever the measured gas, at d = 160 mm, the uniformity is lower than 1% at diameters >200 mm. The uniformity of the plasma density is better at d = 160 mm than at d = 85 mm but over lower diameter. However, for a constant 250 mm diameter, the uniformity is better at d = 85 mm than at d = 160 mm. Similar to ECR-plasma source measurements, in the collisional plasma source case, the higher the distance of processing from the source plane the higher the influence of diffusion of the created species by the distant sources and consequently, the higher the diffusion in the centre which increases the edge effects and reduces the uniformity diameter. In other words, increasing the distance from the source plane, due to the same diffusion effect, allows for smoother density profiles and increased uniformity even if the resulted uniformity diameter is smaller. Distribution uniformity from 1% to 5% was obtained whatever the gas over mm diameter areas without any specific optimization. Nevertheless, at d = 85 mm the uniformity can be easily improved by adding a plasma source in the centre of the configuration. If this additional source is supplied with lower microwave power than the peripheral plasma sources it will allow to fill the small lack of plasma density in the centre of the plasma chamber. 4. Comparison ECR vs. collisional The maximum plasma density obtained with 9 off ECR plasma sources and 9 off collisional plasma sources in Ar, O 2 and N 2 at d = 85 and 160 mm is plotted in Figure 10. For better comparison, the ratio between plasma densities obtained with both sources is also plotted. The microwave power was 1800 W and the pressure regime was chosen to obtain the highest plasma density. At the same power, in argon at d = 85 mm, the matrix using ECR plasma sources allows to obtain cm 3 while the collisional configuration reaches» cm 3, i.e. more than seven times higher density than ECR. This can be explained taking into consideration the operating pressure for both sources,»0.5 1 Pa for the ECR plasma source and»5 Pa for the collisional plasma source. In molecular gases, an important part of the energy is used for the dissociation of molecules, explaining the ratio of»2 for oxygen and nitrogen. For the same operating conditions, i.e. the conditions that allow to obtain the highest plasma density, the maximum intensity line obtained with 9 off ECR sources and 9 off collisional sources in Ar, O 2 and N 2 at d =85mm Figure 11. The ratio of collisional/ ECR intensity for each line is plotted in the same figure. The chosen lines are 750 nm in

13 12 L. LATRASSE ET AL. Figure 9. Plasma uniformity vs. distance and diameter. (a) argon; (b) oxygen; (c) nitrogen; (d) air.

14 JOURNAL OF MICROWAVE POWER AND ELECTROMAGNETIC ENERGY 13 Table 3. Distribution uniformity for 8 off collisional plasma sources in circular configuration in argon, oxygen, nitrogen and air at d = 85 and 160 mm, 5 Pa, 200 W/source. 8 off plasma sources d =85mm d = 160 mm 200 W/source Argon Oxygen Nitrogen Air Argon Oxygen Nitrogen Air Uniformity (%) a 1.8 a 2.8 a 2.5 a Diameter (mm) Note: a <1% at 200 mm diameter. Figure 10. Comparative results of plasma density obtained at full microwave power in Ar, O 2 and N 2 for ECR plasma source and collisional plasma source; collisional source/ecr source plasma density ratio. Ar, 777 nm in O 2 and 337 nm in N 2. As expected, the collisional source shows higher intensity whatever the gas; the ratio between sources varies from 2 in O 2 to 4 in Ar. Table 4 summarizes the obtained results. ECR plasma source attains densities >10 11 cm 3 whatever the gas (Ar, O 2,N 2 and air) at d = 85 mm while the collisional plasma source attains densities >10 12 cm 3 in argon and densities >10 11 cm 3 in molecular gases, O 2,N 2, air and H 2. The plasma density and Figure 11. Comparative results of maximum intensity line obtained in Ar, O 2 and N 2 for ECR source and collisional source; collisional source/ecr source intensity ratio.

15 14 L. LATRASSE ET AL. Table 4. Comparative results of ECR and collisional plasma sources. Plasma source type Operating pressure range (Pa) Min. MW power to sustain plasma Max. plasma density cm 3 9 sources, 1800 W, d =85 mm (W) Ar O 2 N 2 Air Electron temperature (ev) Plasma uniformity, 8 sources in circular network ECR <4%, 200 mm area diameter, d = 85and 160 mm Collisional > <3%, 240 mm area diameter, d = 85and 160 mm <1%, 200 mm area diameter, d = 160 mm the measured intensity line with the collisional plasma source are both higher than those of the ECR source. However, the ECR plasma source is more flexible in operation especially that the obtained plasmas can be sustained with just a few watts and are easier to breakdown. Moreover, the ECR source allows to work at lower pressure, with higher electron temperature meaning higher particle energy and, in case of deposition processes, better layer adherence to the substrate. Even if the collisional source shows good tuning for wider operating conditions, the ECR source is more efficient on the whole pressure and power range. 5. Conclusions It has been proved that multiple ECR or collisional microwave plasma sources can be distributed together in the same reactor in connection with industrial plasma scalingup requirements to obtain high uniformity plasma over wide processing areas. In this design each plasma source is connected to its own microwave solid-state generator, which allows to produce a forward wave with variable frequency ( MHz, 100 MHz increment) enabling an automatic adjustment loop of the reflected power created occasionally by changes in the operating conditions. Measurements with Langmuir probe and optical emission spectroscopy showed that parameters like plasma density and uniformity are highly dependent on the microwave power dissipated by the plasma, reactor pressure and the network distribution of the plasma sources within the reactor. In circular network configuration, the ECR source has slightly less plasma uniformity than the collisional source due to the fact that the ECR source operates at lower pressure where the diffusion of species is higher. In this configuration, better plasma uniformity is attainable if the multisource ECR reactor is operated either at lower microwavepowerorifthedistancebetweentwo consecutive sources is increased. In compact matrix configuration, the plasma uniformity area diameter is higher at closer position to the source plane because the diffusion of the consecutive sources is limited. The adequate distance from the source plane also depends on the matrix compactness. Lower lattice mesh allows to work closer to the source plane; when the lattice mesh is high compared to the distance from the source plane, multiple peaks corresponding to the position of the plasma sources are noticeable on the density profiles.

16 JOURNAL OF MICROWAVE POWER AND ELECTROMAGNETIC ENERGY 15 Finally, results proved that both sources allow to produce large, uniform and high density plasma without scale limitation, whatever the lattice mesh and the dimension of the treated surface. The choice of the matrix depends on the intended application. For the same surface, high number of sources will lead to good uniformity and high density due to both the number of plasma sources and their better ionization efficiency close to the source plane. A higher lattice mesh will allow to have uniform and less dense plasma at higher distance from the source plane while using lower number of plasma sources. Moreover, plasma uniformity can be continuously optimized due to flexibility of the control and the disposition of each plasma source either by adding locally a plasma source to fill a local lack of density or by regulating the transmitted power to the outer plasma sources to limit edge effects. Disclosure statement No potential conflict of interest was reported by the authors. Funding This work has been funded in the framework of the project Plasma Airborne molecular contamination Ultra Desorption (PAUD), supported by OSEO [contract number I W]. Notes on contributors Louis Latrasse has a masters degree in Engineering (Material Science, Institut National Polytechnique de Grenoble, 2003) and a PhD in Physics and Nanophysics (Universite Joseph Fourier de Grenoble, 2006). He worked several years on ECR Ion Source design for particles accelerators. Since 2010 he is Sairem s Plasma Specialist in the R&D department. He is the designer of innovative micro-wave plasma sources: low pressure coaxial plasma sources for large scale processing, surface wave plasma sources, resonant cavity for diamond deposition. He also performs microwave modelling and plasma characterization, general microwave modeling of cavities, tunnels, applicators, for the whole company. Recent development in plasma: ECR coaxial plasma source Aura-Wave. High pressure coaxial plasma source Hi-Wave and a new industrial surface wave compact plasma source S-Wave. Dr Latrasse is also a member of the European Physical Society. Marilena Radoiu, Chartered Chemist (CChem) and Member of the Royal Society of Chemistry (MRSC), received her MSc. in Organic Technological Chemistry from the Polytechnic University of Bucharest in 1993 and her PhD. in Radiochemistry and Nuclear Chemistry from the same university in She has extensive work experience in different international academic and industrial environments. She has worked for 20 years in Romania, Canada, the UK and France in the development of microwave-assisted technologies with applications in chemical synthesis, biomass extraction, plasma etc. Her work has included engineering and development of novel industrial and scientific standard and custom products, such as Zenith Etch and Sirius6000 (microwave plasma reactors for semiconductor gas cleaning) and MiniFlow 200 and Minilabotron 2000 (microwave assisted laboratory equipment). He is also a member of several professional associations, including the Association for Microwave Power, Education and Research in Europe (AMPERE). For more details, Juslan Lo received his Master s Degree in Electrical Engineering and Automation from the Institut National Polytechnique of Toulouse in 2008 and PhD. in Plasma Physics and Engineering from Universite de Toulouse III in His main interests include interactions between plasma

17 16 L. LATRASSE ET AL. discharges, electromagnetic waves and biological substrate. During his PhD., he took interest in reconfigurable plasma-based photonic crystals and metamaterials, specially within microwave range frequencies. He joined INU Champollion in 2012 where he currently holds the position of Associate Professor. He started working on plasma usage for decontamination and medical purposes. Philippe Guillot is Full Professor in electronics and physics at Champollion University (France) since 2006, after 12 years as Associated Professor at the Toulouse University (France). He created in 2006 the plasma research group at Champollion University. He has co-authored more than 50 scientific papers and three patents. He has supervised 10 Ph.D Thesis and had in charge many academic and industrial projects. He has expertise on development, characterization and improvement of plasma sources, from power supply to plasma emissions, using electrical diagnostics, optical spectrometry and mass spectrometry, for glow discharge applications and industrial processes. ORCID Marilena Radoiu References Antonin O, Latrasse L, Taylor AA, Michler J, Raynaud P, Rats D, Nelis T A novel microwave source for collisional plasma for nano-crystalline diamond (NCD) deposition. Paper presented at: International Conference on Phenomena in Ionized Gases; Iasi, Romania. Antonin O, Taylor AA, Michler J, Raynaud P, Rats D, Latrasse L, Nelis T Nanocrystalline diamond film deposition by matrix elementary plasma sources. Paper presented at: Diamond and Carbon Materials; Bad Homburg, Germany. Bechu S, Bes A, Lacoste A, Pelletier J Device and method for producing and/or confining a plasma. Patent WO 2,010,049,456. CNRS. Bechu S, Maulat O, Arnal Y, Vempaire D, Lacoste A, Pelletier J Multi-dipolar plasmas for plasma-based ion implantation and plasma-based ion implantation and deposition. Surf Coat Technol. 186: Latrasse L, Radoiu M, Jacomino J-M, Grandemenge A Facility for microwave treatment of a load. Patent WO 2,012,146,870. Sairem SAS. Latrasse L, Radoiu M, Jacomino J-M, Depagneux B Design of an ECR coaxial microwave plasma source AURA-WAVE using solid state microwave generator. Paper presented at: 14th International Conference on Microwave and High Frequency Heating; Nottingham, UK. Latrasse L, Radoiu M, Lo J, Guillot P GHz microwave plasma sources using solid state microwave generators. ECR-type plasma source. J Microw Power Electromagn Energy. 50: Moisan M, Pelletier J Physique des plasmas collisionnels [Physics of collisional plasmas]. Grenoble: EDP Sciences. Chapter 4, Introduction a la Physique des decharges HF; p