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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges 5 Educational Issues Many of the challenges discussed in previous sections are rooted in the interdisciplinary nature of plasma processing, and the difficulty that any individual, or group of individuals, has in acquiring the tools necessary to carry plasma process and reactor design from inception to fruition. It is clear that the educational background of professionals in plasma processing must be simultaneously narrow, to enable them to address challenges in their individual specialties, and broad, to enable them to address the interactions between processes. As in other high-technology undertakings, the skills required for a healthy plasma processing industry encompass virtually the entire range of technical, managerial, and support roles. One can loosely group these skills in the plasma processing industry as: Process science and engineering; Equipment design and product engineering; Test engineering, circuit design, system integration, and packaging; Equipment maintenance; Quality control; Management; and Sales It is clear that professionals in each of these categories require individual specialized skills. However, it is also clear that individuals in each category require some exposure, through formal education, to the science and technology that forms the basis of their industry. Because plasma processing is an interdisciplinary science, there are no readily available compendia that categorize scientists and engineers working in plasma processing. It was not possible for the panel to determine what company needs are for plasma processing personnel, as this is generally considered proprietary information. However, in informal polls and in discussions at the workshop, there was a clear consensus that few people working in the field have actually been trained in low-energy plasma science. Most professionals in the field have been trained as chemists, chemical engineers, physicists, plasma physicists, or electrical engineers. This situation is characteristic of the field of materials science in general (see Materials Science and Engineering for the 1990s, National Academy Press, Washington, D.C., 1989). There was a similar consensus that the number of high-quality students graduating with training in low-energy plasma science or plasma processing research is insufficient. The panel has estimated the numbers of professionals required to maintain a healthy U.S. plasma processing industry, considering both the market value of products directly produced by the industry and the observed trends in high-technology companies such as computer manufacturers, which have revenues of approximately $100,000 to $300,000 per worker. The current worldwide market directly in plasma processing is $1 billion (plus $800 million in plasma spraying) and will grow to $2 billion ($3.5 billion including spraying) by 1995 (see Figure 3.1), of which approximately half is in the United States. This suggests a need for 2,500 to 5,000 U.S. professionals with expertise in plasma processing. Assuming that at least 10 percent of these
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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges people are replaced annually by either normal attrition or additions for growth, the U.S. plasma processing industry needs at least 250 to 500 new professionals annually. The skills and educational level required by these people will be varied, but the majority of these needs can be satisfied by training on the B.S. and M.S. levels. However, faculty must be educated first before they can prepare undergraduates for careers in plasma processing. Maintaining world leadership in plasma processing requires a healthy educational infrastructure that produces both B.S./M.S. and Ph.D. graduates with the skills required to quickly contribute to the industry. If we do not prepare our faculty and students to meet the plasma processing needs of industry, the cost will be high. On-the-job training in high-technology industries requires an estimated 3 years before a new hire can be assigned full project responsibility. This time should be compared to the 6 to 9 months required for a well-trained, well-educated professional to master the same job. The cost to the national economy of on-the-job training in the plasma processing industry will be approximately $125 million to $250 million annually. Considering that this cost leverages a $1 billion to $2 billion plasma equipment industry, which in turn leverages a $17 billion to $38 billion microelectronics industry, the importance of adequately trained professionals cannot be overestimated. These costs to the national economy should be compared to the costs of improving the educational infrastructure to provide proper education and training. Five hundred new professionals per year means that 10 universities must each produce 50 graduates per year to work in the plasma processing industry. Providing annual university grants of $500,000 each to 10 universities for sustaining and promoting research and education in plasma processing seems a small price to pay when compared to savings from on-the-job training and the ripple effect that a strengthened electronics industry will have on the economy at large. The discussion in the remainder of this chapter focuses on educational needs for proper training of plasma processing professionals: the preparation researchers need to be able to contribute to the field; educational offerings for undergraduates, graduates, and professionals; and how the United States rates in the preparation of workers compared to Japan and the European Community. EDUCATIONAL REQUIREMENTS FOR UNDERGRADUATES In this discussion of key components of the curriculum for undergraduate scientists and engineers preparing to work in plasma processing, two major themes are emphasized. First, plasma processing is highly interdisciplinary. Undergraduate students must be encouraged to take courses from a variety of academic departments. Second, plasma processing is now a largely empirical science. To be successful in this field an undergraduate must obtain a working knowledge of the scientific method and proper laboratory training. To obtain the broad background needed to contribute in a technical role in the plasma processing industry, courses in the following areas are essential: Atomic and molecular physics, Chemistry and chemical kinetics, Computer science, Electromagnetic theory, Plasma and glow discharge physics, Condensed matter and materials science, and Processing and manufacturing technology.
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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges Laboratory Courses and the Scientific Method Students intending to specialize in plasma processing, as well as the general technical student, would benefit greatly if experiments in discharge plasmas were incorporated into existing intermediate and advanced undergraduate laboratory courses. For example, measuring electron densities using a Langmuir probe in a sealed mercury-vapor glow discharge tube is a straightforward and inexpensive experiment. The need for obtaining adequate laboratory experience on the undergraduate level affects most high-technology industries, and plasma processing in particular. Although great efforts have been made to provide this instructional infrastructure, the current situation with respect to laboratory courses is, in many cases, not satisfactory, and undergraduate laboratory experiences are inadequate. As a result, all technical undergraduate students suffer, particularly those who intend to specialize in plasma processing. Modern instructional laboratory courses are expensive to establish and maintain. In times of inadequate funding, discretionary resources are often allocated instead to other activities. As a result of plasma processing now being an empirical science, the undergraduate must obtain a working knowledge of the scientific method. Research in plasma processing is ''small'' science, and the scientific method is practiced in a very traditional fashion. A working knowledge of the traditional scientific method is not taught in formal courses; its practice can only be taught in well-conceived laboratory courses (either experimental or computational) or through research projects. The National Science Foundation (NSF) has recognized the importance of maintaining undergraduate laboratories and has started the Instrumentation and Laboratory Improvement Program to address the problem. This program could be strengthened by targeting specific high-priority areas of national importance, such as plasma processing. Additional programs funded by other agencies and foundations are also required to augment the efforts of the NSF, since its resources are limited and the need for improving the undergraduate infrastructure is great. Research Experiences and Cooperative Programs Research experiences for undergraduates help develop laboratory and computer skills and teach the scientific method. The NSF sponsors the Research Experience for Undergraduates Program, which provides funding for this purpose. The national laboratories and many corporate laboratories offer summer internship programs and cooperative programs. The Cooperative Education Association Inc. is doing an excellent job of developing, promoting, and implementing the concept of cooperative education. These programs are all valuable, but they should be strengthened to address high-priority areas such as plasma processing. This could be accomplished by cooperative funding of student internships between federal agencies and industry, which could also enable the smaller yet important equipment vendors to take part in these valuable programs. Cooperative programs during the summer for high school science teachers provide an important opportunity for introducing plasma technology into public school courses. Industries and universities could provide research opportunities for public school teachers in the same manner that these opportunities are made available for undergraduate students. U.S. GRADUATE EDUCATION To survey current curricula for graduate students preparing to work in the field of plasma processing, the panel examined course catalogues to determine how graduate programs are
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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges tailored to meet the needs of industry. Fourteen major universities and 76 departments where faculty are involved in plasma research were surveyed. In the panel's informal survey, 160 courses were identified as primarily plasma science courses. The panel's general conclusions from the survey were that (1) these institutions adequately cover subjects related to highly ionized, weakly collisional plasmas as found in fusion research; and (2) these institutions, with few exceptions, are not adequately covering concepts related to weakly ionized, highly collisional plasmas as found in plasma processing research. Most of the courses do cover important topics such as Debye screening, plasma frequency, single-particle motions in electric and magnetic fields, fluid models of plasmas, and kinetic theory. But, for the most part, graduate-level plasma science courses are not preparing students in the physical sciences and engineering to work in the field of plasma processing. Graduate-level courses are controlled by faculty interests, and deficiencies in plasma science curricula directly reflect the small number of academic research programs in plasma processing. Areas that are vital to a healthy education in plasma processing but that have received inadequate attention in most graduate curricula include the following: Fundamentals of electron collisions. Less than 10 percent of the courses surveyed cover fundamentals of electron-atom/molecule and ion-atom/molecule collisions. These types of collisions are dominant in weakly ionized plasmas. The fundamentals of Coulomb collisions, dominant in fusion plasmas, are discussed in a majority of the courses. Only one plasma course in the survey includes multistep ionization in its formal syllabus, although the topic is known to be more widely addressed. Electron impact processes involving excited states of atoms and molecules can dominate the ionization balance of both dc and rf discharges over a wide variety conditions, and exposure to these concepts is important to engineers and scientists working with low-temperature plasmas. Hydrodynamic approximation. Less than 5 percent of the courses surveyed cover the local field or hydrodynamic equilibrium approximation as a formal syllabus item, although the topic is known to be more widely taught. This is a fluid approximation in which electron and ion transport coefficients are parameterized in terms of the ratio of the electric field to gas density. This approximation is important because it is the starting point in modeling most plasma reactors, and most experimental data on electron transport coefficients are obtained using the local field approximation. Plasma reactor technology. Less than 10 percent of the courses surveyed cover fundamentals of direct-current, radio-frequency, and microwave plasma reactors. This is a serious deficiency since plasma reactor geometry and power coupling schemes are important factors in process design. Any professional working in plasma processing requires exposure to these concepts. Radiation transport. Less than 5 percent of the plasma courses surveyed cover radiation trapping and radiation transport. Optical transitions from excited levels to the ground level of atoms and molecules in discharges are often optically thick. Diagnosing low-pressure plasmas must take these effects into consideration. Power that is optically emitted and absorbed in high-pressure plasmas can sometimes play a dominant role in the power balance. Plasma chemistry and plasma technology. Less than 5 percent of the courses surveyed cover fundamentals of plasma chemistry or the collisional/radiative rate equation models that are used to describe plasma chemistry. There are, no doubt, other courses that offer this educational background. The fact that they are "hidden" from courses associated with plasmas is a weakness. Finally, only 5 to 10 percent of the courses surveyed cover fundamentals of etching and deposition.
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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges TEXTS AND COMPUTER-AIDED INSTRUCTION The content of graduate-level courses is at least partially influenced by the content of textbooks. Most introductory graduate-level courses in plasma science are taught from the texts that were written primarily for students intending to work in fusion research. In these texts there is rarely any mention of charged particle-neutral particle collisions, important concepts such as the local field approximation, or technologies such as etching or deposition. Many courses emphasizing collisional plasmas rely on material from classic older textbooks such as Basic Data of Plasma Physics (MIT Press, Cambridge, Mass., 1967) by S.C. Brown and Ionized Gases (Clarendon Press, Oxford, 1965) by A. von Engel. Unfortunately these texts are out of date and out of print. There are a number of Russian translation texts (e.g., Smirnov's Physics of Weakly Ionized Gases, B. M. Smirnov, translated by Oleg Glebov, MIR Press, Moscow, 1981, and Biberman's Kinetics of Nonequilibrium Low-Temperature Plasmas, L. M. Biberman, V. S. Vorobev, I. T. Iakubov, Consultants Bureau, New York, 1987, translation of the Russian Kinetica Neravnovesnofi Nizko-Temperaturnofi Plazmy ) that serve well as supplementary texts, but not as primary teaching tools. The lack of textbooks in collisional plasma science extends to plasma technology. The few existing graduate-level courses on plasma processing are taught primarily from notes. Although there is an excellent series of monographs on plasma processing currently being published (Plasma-Materials Interactions, edited by O. Auciello and D. L. Flamm, Plasma-Surface Interactions and Processing of Materials: Proceedings of the NATO Advanced Study Institute on Plasma-Surface Interactions and Processing of Materials, Alicante, Spain, Kluwer Academic Publishers, Dordrecht, Boston, 1990), these books were not intended to be used as texts. The lack of textbooks in the field is highlighted by the continued use of older monographs for instructional purposes. Glow Discharge Processes (Wiley, New York, 1980) by Brian Chapman first appeared in 1980 and is commonly used for undergraduate and graduate courses. Although it is an excellent introduction to the field, more current offerings are needed. Computer-aided instruction, now often used in first-year physics and chemistry courses, is not commonly associated with upper-level undergraduate and graduate courses. The Plasma Simulation Group at the University of California at Berkeley has developed user-friendly, portable programs, capable of being run on personal computers for use in computer-aided instruction. More programs of this type could be offered in teaching plasma-surface interactions such as profile evolution during etching and deposition. FACULTY DEVELOPMENT The lack of graduate courses and programs in plasma processing is directly attributable to a lack of trained faculty, which in turn relates to the inadequacy of research funding. This need can be partly satisfied by improving ties between universities, national laboratories, and industries. "Co-ops" for faculty in industry and national laboratories, and visiting academic appointments for industrial researchers, would greatly aid in cross-training of these individuals. These programs should be directly supported by both industry and government. CONTINUING EDUCATION Because plasma processing is interdisciplinary and is rapidly expanding in the industrial sector, scientists and engineers trained in other disciplines are continually entering the field. It is also the norm for new hires to have no formal training in plasma processing. Given these conditions, continuing education is vitally important.
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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges Most large industrial research laboratories active in plasma processing have established in-house continuing education courses for their employees. The majority of continuing education opportunities, though, are offered by third parties: consultants and professional societies. The Materials Research Society (MRS) and the American Vacuum Society (AVS) are the primary coordinators of postgraduate short courses in plasma processing. These organizations offer at least seven courses directly related to plasma processing, and at least an additional eight with a portion of their content addressing plasma processing. Courses are also offered by the Society of Photo-Optical Instrumentation Engineers (SPIE) and the Electrochemical Society (ECS). Students from more than 280 companies have taken the MRS and AVS short courses directly addressing plasma processing during the past 6 years. This list encompasses virtually all major companies active in plasma processing. A surprising number of university employees or students have also attended these courses, attesting to the lack of those courses on their home campuses. FOREIGN EDUCATIONAL OFFERINGS To objectively assess the status of U.S. educational offerings in plasma processing, it is important to make comparisons with those in foreign countries. One indication of the importance that foreign competitors place on plasma processing is their commitment to relevant educational programs. A comprehensive study of the education in plasma processing offered by foreign universities is beyond the scope of this report. However, the panel informally surveyed foreign researchers active in plasma processing, soliciting information on degree programs, course offerings, cooperative programs, and postgraduate education. More than 60 researchers in 12 countries were queried, and more than 50 percent responded. Additional input was obtained from panel members touring foreign laboratories (principally in Japan) and from published descriptions of national programs (again, principally in Japan). The responses varied in detail, but some provided extensive summaries of educational offerings in plasma processing in their countries. Universities in Eastern Europe with a long, rich history of research in collisional plasmas are now focusing on plasma processing. Although cooperation between universities and government laboratories is greater in Eastern Europe than in the United States, coordination of that research is no better. Below, the panel highlights educational programs in Japan and France, on which the most information was obtained. Japan According to the panel's informal survey, course offerings in plasma processing and collisional plasmas at universities in Japan are generally comparable with those in the United States. They vary widely from campus to campus, primarily relying on the interest of individual faculty to sponsor courses. There are, however, notable exceptions. Keio University has three undergraduate and two graduate courses, with a combined enrollment of more than 120, directly related to collisional, low-energy plasmas. Tokyo Institute of Technology has an annual enrollment of 40 to 70 students in courses directly related to plasma processing, while the University of Tokyo has undergraduate and graduate courses in plasma processing. Similarly, Hokkaido University has three undergraduate courses and two graduate courses in topics related to low-energy, collisional plasmas. Kyushu University has a required course in gaseous electronics for electrical engineering undergraduates and an optional plasma engineering course, in addition to a graduate course that is oriented more toward fusion. By contrast, this panel is
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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges aware of no required courses in plasma technology at undergraduate institutions in the United States. It is interesting to note that many courses relating to collisional plasmas in Japan trace their origins to gas laser technology. In a national program sponsored by the Ministry of Education, Science, and Culture (MESC), a commitment was made to develop gas laser technologies for materials processing. This commitment spawned courses in high-voltage engineering, plasma engineering of lasers, and applied electron physics. The plasma processing community has benefited from all of them. Like universities in the United States, Japanese universities do not have formal degree programs in plasma processing, but rather fold plasma processing into existing degree programs. Opinions expressed on the availability and suitability of texts on plasma processing were quite varied, leading the panel to conclude that there are no universally accepted texts for use in these courses. France The results of the panel's informal survey indicate that French graduate education in plasma processing operates much like that in the United States. In general, plasma processing researchers are scattered among many departments. There are, however, many degree programs in France, either in place or pending, that specialize in nonfusion and nonspace plasmas. The majority of them are classified as Diplome d'Etudes Approfondie (DEA). These are sometimes temporary degree programs that are approved by the Ministry of Research and Technology and associated with a particular university or CNRS facility. There are typically 20 students in each program. The degree programs, equivalent to an M.S. degree in the United States, consist of an academic year of course work. At the end of the year, students are required to complete a short research project (duration of approximately 3 months) either at the university, at a CNRS facility, or in industry (public or private). A final oral presentation is reviewed by both university and industrial representatives. Some of the DEA programs having direct application to plasma processing are listed below. Université Pads VI—Génie des Procedes et Chemie Applique: This program of study deals with plasma-surface interactions and rf discharge reactors. Université Pads VI—Electrotechnique: Plasma engineering with emphasis on atmospheric pressure plasmas (switches, corona discharges, arcs). Université Pads Sud—DEA de Physique des Gas et des Plasmas: This program has fairly comprehensive course work on basic collisional plasma physics, plasma-surface interactions, plasma diagnostics, modeling, plasma chemistry, and laboratory practices. It is closely aligned with CNRS. Université Paul Sabatier, Toulouse—Génie des Procedes Plasmas: This program, begun in the fall of 1991, will specialize in collisional plasmas and will include basic courses in plasma physics, macroscopic properties of discharges in gases, plasma diagnostics and principles, discharge lasers, and plasma processing. An existing degree program (Diplome d'Etudes Approfondie de Physique des Plasmas) specializes in plasmas but prior to 1990 did not emphasize plasma processing applications. Université Nantes: There are DEA programs in both materials science and in electronics. Although not specializing in plasma processing, they have a high level of course content in the area. The pertinent topics include plasma materials interactions and plasma modeling. There are other DEA and degree programs emphasizing materials processing at Université Pads XI at Orsay, Université de Orleans, and Université de Limoges.
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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges A goal of the CNRS-sponsored Groupe de Recherche Coordonne (GRECO) 57 is to disseminate "fundamental knowledge" in plasma processing to researchers in other institutions or industry by organizing open meetings and summer schools. Two books (in French) have been published following such summer schools: Reactivite dans les plasmas: Applications aux lasers et au traitement de surface (Reactivity in Plasmas: Applications to Lasers and Surface Treatment; A.M. Pointu and A. Ricard, eds., Les Editions de Physique, 1982) and Interactions plasmas froids materiaux (Interactions of Cold Plasmas with Materials; GRECO 57 du CNRS, Les Editions de Physique, 1987). These texts have been very well received by students in introductory courses on plasma processing. A summer school held in parallel with the 8th Colloque International sur les Procedes Plasmas (CIP 91) will result in publication of a new text, Depot et gravure chimique par plasma (Plasma Chemical Deposition and Etching; GRECO 57 du CNRS and Société Francaise du Vide, 1991). FINDINGS AND CONCLUSIONS The United States is not adequately preparing for the rapid growth of plasma processing in materials processing applications. As a result, on-the-job training will be necessary to remain competitive. However, such training is inherently costly when compared to investment in the educational infrastructure. Worse, the time lost in on-the-job training may result in missing market windows for new products and may present economic obstacles that can be difficult or impossible to overcome. Although undergraduate curricula at universities in the United States generally include the necessary lecture courses to prepare students to work in the field of plasma processing, survey and introductory courses in plasma science and technology are lacking. Survey courses are particularly necessary to acquaint nontechnical students with the basics of high-technology industries such as plasma processing. Progress toward these goals can be made by incorporating the physics of collisional plasmas into existing and improved laboratories, and general science courses. Because of the interdisciplinary nature of plasma processing, the available courses are scattered throughout many departments. Although the benefits of establishing undergraduate degree programs in plasma science are not clear, it is clear that undergraduates would benefit greatly from interdepartmental non-degree programs that serve to advise and direct students toward these courses. The most serious needs in undergraduate education are properly trained and educated teachers and professors as well as adequate, modern teaching laboratories. Internships in industry for faculty interested in learning about plasma processing do not exist. Proper training in the traditional scientific method, as provided in laboratory classes, is a necessary component of plasma processing undergraduate education but is not emphasized sufficiently. The Instrumentation and Laboratory Improvement Program sponsored by the NSF has been only partly successful in fulfilling these needs. Industrial cooperative programs, internships, and research experiences for undergraduates through industrial cooperative programs or internships are essential for high-quality technical education. Graduate curricula are, for the most part, not offering adequate exposure to the science of weakly ionized, highly collisional plasmas. The panel's survey of current curricula shows that only a few U.S. universities have formal course work in this science. Since specialty graduate courses are taught by professors who are actively conducting research in those areas, the lack of courses is a direct result of there being little funding for graduate research in plasma processing and low-energy plasmas. The lack of good texts on collisional plasmas and plasma processing is a serious problem, although modern texts do exist in French, Japanese, and Russian. English translations are mostly unavailable.
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Plasma Processing of Materials: Scientific Opportunities and Technological Challenges The level of support for plasma processing at U.S. universities is not adequate to attract the quality and quantity of graduate students needed by the U.S. plasma processing community. Federal support could provide an important incentive to forge the necessary industry-university links. Education in plasma processing in the United States lags behind that of our principal competitors in the field: Japan and Western Europe. The U.S. educational infrastructure in plasma processing lacks focus, coordination, and funding when compared to the infrastructures in both Japan and France. There are no formal graduate degree programs in plasma processing in the United States. It is clear that formulating and maintaining degree programs not only motivates the development of new courses and textbooks, but is also a more visible vehicle for attracting students to the field. Continuing education offerings and short courses play a valuable role in training newcomers to the field and supplementing the education of specialists. Since short courses and in-house offerings are very much market driven, they both respond to and reflect the needs of the community. They also represent a valuable source of educational materials, as the notes from many of these courses serve as introductory texts. The fact that university personnel are regularly attending short courses reflects a lack of and need for similar offerings in universities.
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