Papers

ICMCTF2000 Session G3: Hollow Cathode, Hybrid and Atmospheric Plasma Processing

Monday, April 10, 2000 1:30 PM in Room Town & Country

Monday Afternoon

Start	Invited?	Item
1:30 PM		G3-1 Ion Plating - Past, Present and Future D.M. Mattox (Management Plus, Inc.) Ion plating is an atomistic vacuum deposition process in which the depositing film is continuously or periodically bombarded by energetic atomic-sized inert or reactive particles which affect the growth and properties of the film. The source of depositing atoms can be from vacuum evaporation, sputtering, arc vaporization or from a chemical vapor precursor. Bombardment is generally either by ions accelerated from a plasma in the deposition chamber ("plasma-based" ion plating) or from an "ion gun" ("vacuum-based" ion plating). The stages of ion plating can be differentiated into surface preparation, nucleation and interface formation, and film growth. Ion plating was first described in the early 1960's and was initially used to enhance film adhesion and improve surface coverage. Later it was shown that controlled bombardment could be used to modify film properties such as density, morphology, index of refraction, and residual film stress. More recently the bombardment has been used to enhance chemical reactions in reactive and quasi-reactive deposition processes. Presently ionization and acceleration of the depositing film atoms ("film ions") is being used for "directed deposition" to improve filling of surface features in semiconductor processing. This paper will review the history of the development of the ion plating process and how it has affected thin film process technology. Potential developments using the ion plating concept will be discussed.
2:10 PM		G3-3 Radio Frequency Hollow Cathode Source for Large Area Cold Atmospheric Plasma Applications L. Bardos, H. Baránková (Uppsala University, Sweden) A new type of radio frequency (rf) large area non equilibrium ("cold") plasma sources operating at atmospheric gas pressures in an open reactor is presented. The source is based on specially designed rf electrode with the gas flowing through an inner microstructure integrated in the electrode. A cylindrical source of 35 mm in diameter with about 900 hollow cathodes forming an integrated open structure and a rectangular 120 x 20 mm² source of this type will be described. The necessary rf power for the source operation is only several tens of watts. Experimental tests show that the performance of both sources at atmospheric pressure is substantially better in comparison with single cylindrical rf hollow cathodes of less than 500 µm in diameter. The argon and neon plasmas generated between the main electrode and the substrate holder (electrically grounded counter electrode) are uniform and very stable. The optical emission spectroscopy study, the rf current, voltage and impedance measurements, as well as the substrate temperature tests reveal three different power dependent regimes of these plasma sources. Effects of plasma interactions with sample surfaces were studied on both temperature sensitive samples (paper, plastics) and high melting point materials (steel, silicon). The design of sources allows their direct scaling up and may bring a number of interesting applications in large area cold atmospheric plasma processing.
2:30 PM		G3-4 A New Spatially Tunable Plasma Source for Thin Film Processing D. Gibson, G. Chester, D. Yates (RTC Systems Ltd., United Kingdom) Ion or plasma assisted vacuum deposition processes are routinely used to modify microstructure of thin films, achieving enhanced film adhesion, durability, density, stoichiometry and stress control. Currently available plasmas or ion sources for assisted vacuum deposition have either fixed spatial distribution of the ion/plasma flux at the substrate plane, are engineered for ion/plasma overlap or positioned to provide best overlap with the evaporant fluxes. This paper will discuss modular construction, allowing for various hallow cathode configurations and output coil configurations. The paper will also discuss the performance of the spatially tunable plasma source. Data will be presented showing the coverage and spatial distribution of the new ion source.
2:50 PM		G3-5 Study of Deposition Rates in a Hollow Cathode Discharge V.H. Baggio-Scheid (Centro Técnico Aeroespacial, Brazil) The hollow cathode discharge is a source of metal atoms, which has been used to built lasers and in the processes of thin film depositions. In this discharge almost all the photons and metastable atoms, as well the ions, will impinge upon the cathode, increasing the efficiency of the secondary electron emission in this surface. In addition, each electron makes more ionizing and exciting collisions, thus improving the effectiveness of the discharge. In this way, there is a great increase in the current density and sputtering rate compared with the plane parallel glow discharge. However, for thin film deposition applications, a substrate must be inserted into the cathode, which disturbs the discharge. In this work we investigate the influence of ceramic and metallic substrates on the discharge characteristics of a copper hollow cathode discharge in argon. The discharge was operated at pressures between 0.8 and 2.0 mbar and current densities up to 7 mA cm^-2. The results concerning the thickness of the films as a function of the deposition time measured for different discharge parameters will be presented and discussed.
3:30 PM		G3-7 Hybridization of the Polymer Multi-Layer (PML) Deposition Process J.D. Affinito (Pacific Northwest National Laboratory) The Polymer Multi-Layer (PML) process for the flash evaporation, condensation, and radiation curing of reactive fluids has been modified. The radiation curing step has been eliminated. Polymerization is accomplished by passing the monomer gas through a glow discharge zone, under forced flow conditions, prior to condensation on the substrate. This hybrid process produces high rate deposition of solid films from high molecular weight/low vapor pressure liquid, or even solid, monomer precursors. The gas resulting from the flash evaporation of a liquid monomer mixture, or from a suspension of liquid monomer and insoluble solid particles, is used as the support medium for a glow discharge in a Plasma Polymerization/Plasma Enhanced Chemical Vapor Deposition-like (PECVD) process. Due to the high molecular weight/low vapor pressure nature of the precursors, the plasma of the flash evaporated gas cryo-condenses at extremely high rate on substrates at ambient, and higher, temperatures. Upon condensation the liquefied plasma immediately begins to polymerize to form a solid film due to the high concentration of radicals and ions contained in the liquid film. The process has been successfully implemented in a vacuum roll coating system in a roll-to-roll deposition process. Forced Flow conditions serve to reduce homogeneous reactions in the gas phase which, in turn, prevents particle formation in the gas phase. A variety of Polymer, and Polymer Composite, films have been deposited by this process ranging from 0.1 microns to 24 microns in thickness at web speeds as high as 96 linear meters per minute with excellent thickness uniformity. This new deposition process will be discussed along with some properties of the films fabricated with this new process.
4:10 PM		G3-9 Deposition of Diamond-like carbon Films by Hollow Cathode Multi-jet rf Plasma Source F. Genadij, J. Engemann, D. Korzec (University of Wuppertal, Germany) Diamond-like carbon films with low hydrogen content are deposited by a hollow cathode multi-jet rf plasma source described in detail elsewhere ¹. A plasma with ion concentrations of about 10¹¹cm^-3 is generated by a jet matrix plasma source (JeMPS) operated at 13.56 MHz with rf-power up to 1 kW. In a distance 6 cm downstream the plasma source a 13.56 MHz rf-biasable water-cooled substrate holder is positioned. For all deposition experiments in this work silicon wafer were used. Cleaning in argon plasma together with surface oxide reduction in a hydrogen plasma proved to be sufficient for good film adhesion to the substrate. The subsequent plasma enhanced chemical vapour deposition (PECVD) was done with Helium as carrier gas. Both methane or ethene served as a carbon source being introduced downstream between the JeMPS and substrate holder. Typical gas flows are 400 and 100 sccm, respectively. Total process pressure was set at 0.8 mbar and maintained by a Roots blower. To achieve reproducible results the flow optimized processing chamber was oxygen plasma cleaned after each deposition run. In a stationary mode room temperature deposition rates of 70 to 80 nm/min with methane as the carbon source were measured. With ethene the deposition rates are about a factor 4 higher. All films deposited were characterized by profilometry, micro-Raman spectroscopy, FTIR, ellypsometry measurements, scanning electron microscopy and microhardness tests. It was found that even in the stationary deposition mode used the film thickness variations across a 5 Si-wafer did not exceed +/- 3.5%. Highest deposition rates and best films qualities were obtained at an rf-induced dc-bias of 350 to 420 V. Under the same conditions the refractive index of the films deposited is between 2.2 and 2.4 with a Vickers microhardness of 30 GPa. ¹ D. Korzec, G. Fedosenko, A. Georg, J. Engemann (1999). Hybrid plasma system for diamond like carbon deposition, Asian European Plasma Surface Engineering Conference AEPSE99, Paper No. Thu-OA1.
4:30 PM		G3-10 Surface Functionilization on Polymers with Plasma in Vacuum and at Atmospheric Pressure W. Decker, A. Yializis, S. Pirazada (Sigma Technologies International, Inc.) Treatment of polymer surfaces in the vacuum using plasma has become an important issue for the improvement of coating processes. Recent development allows treating surfaces with a uniform plasma at atmospheric plasma as well, resulting in greatly improved treatment levels for coating, printing and laminating. Presented are two different techniques to treat polymer surfaces: A hollow cathode plasma generator with magnetic plasma enhancement for the vacuum, stable glow discharge plasma for the treatment at atmospheric pressure. Results of treatment of different polymer structures, like long lasting activation of PTFE, are presented. The new developments will guide a new way for surface treatment in the coating and converting industry.
4:50 PM		G3-11 Stable Parallel Operation of Microhollow Cathode Discharge Using the Closed Hollow Cathode H.K. Baik, H.I.P Park, J.H.N Noh (Yonsei University, Republic of Korea) Microhollow cathode discharge has attracted a considerable interest as light source, flat panel display, active media for gas lasers and detoxification of gaseous pollution because of its important properties such as high current densities and non-Maxwellian electron energy distribution functions.paragraphIn spite of these properties and wide applications, without the individual and distributed ballast, parallel operation has not been obtained due to the negative current-voltage characteristic of microhollow cathode discharge, which means an unstable glow discharge current characteristic. But it is essential to achieve the stable parallel operation of microhollow cathode discharge at pressure up to several hundred torr for the application of the flat panel display, light source, and large area processing. Therefore, in order to obtain the parallel operation at pressure up to several hundred torr, microhollow cathode discharge need to be individually or distributively ballasted. On the other hand, for large arrays with the thousands of individual ballast or a distributed ballast, it is very technically challenging and troublesome to control current.paragraphThe present study is mainly focused on the closed microhollow cathode to obtain the stable parallel operation of microhollow cathode discharge without the individual and/or distributed ballast. The resistive behavior of the closed cathode is also compared with that of the open cathode. An external ballast is used to limit current and to prevent glow to arc transition in the circuit.paragraphThe positive slope of the current-voltage characteristic at pressure up to several hundred torr was obtained using the closed microhollow cathode without the individual and/or distributed ballast. Stable parallel operation of microhollow cathode discharge was also achieved by using the closed microhollow cathode. From the present study, a possible mechanism for the positive slope obtained in the closed cathode geometry is suggested.