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Study of Plasma and Ion Beam Sputtering Processes Journal of Physical Science and Application 5 (2) (2015) 128-142 doi: 10.17265/2159-5348/2015.02.007 D DAVID PUBLISHING Study of Plasma and Ion Beam Sputtering Processes M.M.Abdelrahman Accelerators and Ion Sources Department, Nuclear Research Center, Atomic Energy Authority, 13759 Inchas, Atomic Energy, Cairo, Egypt Abstract: The effects of plasma (ions, electrons) and other energetic particles are now widely used for substrate cleaning as well as to assist and control thin film growth and various applications. In this work, historical review of the plasma and its various types are given and described. Different types of gas discharge and plasma production are also discussed in detail. Furthermore, technique of ion beam extraction from a plasma source for sputtering process by using a suitable electrode is carefully studied and given. In further consequence, a general review about the physics and mechanism of sputtering processes is studied. Different types of sputtering techniques are investigated and clarified. Theoretical treatment for determination of sputtering yield for low and high atomic species elements as a function of energy from 100 to 5,000 eV are studied and discussed. Finally, various applications of plasma-and-ion beam sputtering will also be mentioned and discussed. Key words: Plasma, ion sputtering, gas mixing, electron injection. 1. Introduction multicharged ions was given a strong input by studies in connection with fusion research, to deepen our The plasma is the fourth state of the matter, fundamental understanding of the mechanisms of the following the solid, liquid and gaseous states. As the involved collision processes. Accurate knowledge of temperature of the substance increased, the material total electron capture cross sections helps in changes firstly from solid to liquid, then liquid to gas explaining and solving problems in the field of fusion and finally from gas to plasma [1]. In general, there research, astrophysics and laboratory plasma. The are three different kinds of these individual particles more demanding the applications of the plasma that make up the plasma, they are ions, electrons and sources, the more the plasma source has to be neutral particles. Plasma exists in nature as in the sun, carefully designed and optimised to get optimum stars and in the ionosphere and on the earth in performance. High performance of plasma sources transient forms such as lighting. Man made plasmas represents in having ionization efficiency, maximum such as fluorescent lamps, neon signs and high voltage current, high charge state, size and cost taking into sparks industrially, plasmas are used in various forms account the limits of power and the radiation as in semi-conductor processing, material environment. In general, the plasma (ion) source is the modifications and synthesis and other purposes. The main component of any accelerator, from which development of PS (plasma sources) received a strong originates the beam of ions or electrons. Hence, its push from plasma centers all over the world, due to specifications should be carefully considered to adapt the fact that the advancement range of these sources is the expected application. In its basic operation (for strongly increased by the charge state of the plasma ions), a gas is ionized, usually by subjecting it to an sources. Moreover, the plasma sources are useful for electric discharge, and the positively charged ions are basic investigations in atomic physics, surface physics extracted by acceleration towards a negative electrode and related areas. The low energy atomic physics with at a potential of negative potential. The characteristics of the ion source determine to a great extent the Corresponding author: M.M.Abdelrahman. E-mail: [email protected]. performance of the accelerating system. The selection Study of Plasma and Ion Beam Sputtering Processes 129 of an ion source for a particular application should be kind or another. Industrially, plasmas are used in made with due consideration of factors such as species various forms for semiconductor processing, lighting, and intensity capability, beam quality (emittance and materials modification and synthesis and other brightness), ionization efficiency, reliability ,ease of purposes. operation, maintenance, and source lifetime. No truly 1.2 Applications of Plasma Sources universal source exists that will meet all applications requirements. In this work, historical review of the Applications of plasma sources from providing plasma and its various types are given and described. beams of hundreds of amperes for fusion, Different types of gas discharge and plasma nano-amperes for microprobe trace analysis, broad production are also discussed in detail. Furthermore, beams for ion implantation, space thrusters, industrial technique of ion beam extraction from a plasma polymerisation, food sterilisation, to medical, military source for sputtering process by using a suitable and accelerator applications. PIG ion sources have electrode is carefully studied and given. In a found widespread applications in the injectors of the furthermore consequence, a general review about the large particle accelerators used for nuclear and physics and mechanism of sputtering processes is high-energy physics research. The Freeman ion source studied. Different types of sputtering techniques are is widely used in the commercially available ion investigated and clarified. Theoretical treatment for implantation equipment. Laser ion sources, where determination of sputtering yield with low and high very high energy fluxes that can be delivered onto atomic species elements as a function of incident solid targets using a high power pulsed laser can be energy from 100 to 5000 ev are studied. Finally, used to produce dense pulsed plasma with a high various applications of plasma-and-ion beam fraction of highly stripped ion species. In the EBIS sputtering will also be mentioned and discussed. (electron beam ion source), the ions are contained within a high-energy electron beam in a strong 1.1 General Considerations on Plasma Sources magnetic field and in a very high vacuum, for a Plasma is resulted from ionization of neutral gases sufficiently long time for very high charge state ions generally equal numbers of positive and negative to be produced. This ion source is particularly suitable charge carriers. Such plasma is characterized by for particle accelerator injection, especially heavy ion quasi-neutral. When blood is cleared of its various synchrotrons as well as to basic atomic physics. ECR constituents, there remains a transparent liquid which ion sources have the advantage for using as high was named plasma (gely). By comparison to this charge state ion injectors for nuclear physics, particle definition, Irving Langmuir [2] first used this term accelerators especially cyclotrons. Microwave ion “plasma” in 1927 and won Noble prize for this sources used for the filamentless production of high discovery. Plasmas exist in nature in those current beams for high dose ion implantation into environments where the temperature is adequately semiconductors. The excellent performance of the high, such as in the sun, stars and in the ionosphere Freeman ion source is the ion implantation and and on the earth in transient forms such as lighting. industrial applications, especially for semiconductor Man-made plasmas have become commonplace and purposes. Penning ion sources are found to be more are part of the modern world in forms such as successful than other sources for many types of fluorescent lamps, neon signs and high voltage sparks. accelerators. RF ion sources have been used in plasma Laboratory plasmas can be created in a wide variety of and reactive ion beam etching and ion beam doping. ways, most commonly as electrical discharges of one Also, they are widely employed by the semiconductor 130 Study of Plasma and Ion Beam Sputtering Processes industry. Today, ion sources are considered the main the source lifetime, the source size, the power component of the particle accelerator system. Particle efficiency and the ease of maintenance. Fig. 2 accelerators are widely used in nearly every field of illustrates the main parameters for different types of physics from elementary particles to solid state ion sources. physics. They also considered an essential part in 1.4 Gas Discharge Processes many other areas of researches as chemistry, biology, etc (Fig. 1) [3]. Industrial applications cover a wide Ionization is a process in which an atom loses one range as ion implantation in the semiconductor or more of its electrons to another atom. The process industry, indeed, the modification of surface of ionization occurs in nature as a result of properties of many materials. Applications of interactions of photons, electrons, or ions with matter. accelerators in medicine have found wide areas as The most essential setup in every ionization process is isotope production in view diagnostics or treatment, or for therapy with gamma rays and more recently, with neutrons and heavy charged particles. 1.3 Main Parameters of Plasma Sources Different applications of plasma sources require somewhat different sets of certain performance characteristics. Ion sources are characterized by the following parameters [4]: (1) The type of ion species that can be produced by the source. (2) The ability of producing ions of different elements for their applications in particle accelerators, atomic physics, etc. (3) The extracted ion current. (4) The
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