Vacuum microelectronics

Proceedings of the 6th International Vacuum Microelectronics Conference, Newport, R.I., 1993. 

I. L. Grigorishin, G. I. Efremov, N. I. Mukhurov, and P. E. Protas, in Proceedings of the 7th International Vacuum Microelectronics Conference (IVMC 94), 4-7 July 1994, Revue Le Vide, les Couches Minces , Grenoble, France, Suppl. No. 271 (1994)308. 

OTTO Z. ZHOU is an associate professor of materials science and physics and the director of the North Carolina Center for Nanoscale Materials at the University of North Carolina at Chapel HiU. His research is focused on synthesis and solid state properties of nanoscale materials and their energy-storage, vacuum microelectronics, and nano-composite applications. He is the founding director of the North Carolina Center for Nanoscale Materials, which has 15 associated... 

Brodie I, Spindt CA. Vacuum microelectronics. Adv Electron El Phys 1992 83 1-106. 

Thus, ultrasharp tips with nanometer-scale radii of curvature (10 to 20 nm) are used as field-emitting structures, i.e., cold cathodes" in vacuum microelectronics. They also used as a point source of electrons for electron microscope guns. An ultrasharp tip (Figure 14) is one to several atoms wide at its apex, and is used as a source of coherently emitted electrons for holographic studies [35] [37]. Cells with extracting electrodes ("Spindt triodes") are also made by this technique [36]. 

C. A. Spindt, H. E. Holland, A. Rosengreen, and I. Brodie, Field emitter arrays for vacuum microelectronics, IEEE Trans. Electron Dev., 38.2355-2363 (1991). 

PR Schwoebel, I Brodie. Surface-science aspects of vacuum microelectronics. J Vac Sci Technol B 13 1391, 1995. 

Du Pont called this new lubricant material Krytox (64,65) and initially it had such extraordinary properties that it sold for 200/kg ( 187kg ca 1993). Krytox was and is used ia most of the vacuum pumps and diffusion oil pumps for the microelectronics iadustry ia this country and ia Japan because it produces no hydrocarbon (or fluorocarbon) vapor contamination. It has also found important appHcations ia the lubrication of computer tapes and ia other data processiag appHcations as weU as military and space appHcations. 

Thin films of metals, alloys and compounds of a few micrometres diickness, which play an important part in microelectronics, can be prepared by die condensation of atomic species on an inert substrate from a gaseous phase. The source of die atoms is, in die simplest circumstances, a sample of die collision-free evaporated beam originating from an elemental substance, or a number of elementary substances, which is formed in vacuum. The condensing surface is selected and held at a pre-determined temperature, so as to affect die crystallographic form of die condensate. If diis surface is at room teiiiperamre, a polycrystalline film is usually formed. As die temperature of die surface is increased die deposit crystal size increases, and can be made practically monocrystalline at elevated temperatures. The degree of crystallinity which has been achieved can be determined by electron diffraction, while odier properties such as surface morphology and dislocation sttiicmre can be established by electron microscopy. 

The invention of the germanium transistor in 1947 [I, 2] marked the birth of modem microelectronics, a revolution that has profoundly influenced our current way of life. This early device was actually a bipolar transistor, a structure that is mainly used nowadays in amplifiers. However, logical circuits, and particularly microprocessors, preferentially use field-effect transistors (FETs), the concept of which was first proposed by Lilicnficld in 1930 [3], but was not used as a practical application until 1960 [4]. In a FET, the current flowing between two electrodes is controlled by the voltage applied to a third electrode. This operating mode recalls that of the vacuum triode, which was the building block of earlier radio and TV sets, and of the first electronic computers. 

Electroless deposition as we know it today has had many applications, e.g., in corrosion prevention [5-8], and electronics [9]. Although it yields a limited number of metals and alloys compared to electrodeposition, materials with unique properties, such as Ni-P (corrosion resistance) and Co-P (magnetic properties), are readily obtained by electroless deposition. It is in principle easier to obtain coatings of uniform thickness and composition using the electroless process, since one does not have the current density uniformity problem of electrodeposition. However, as we shall see, the practitioner of electroless deposition needs to be aware of the actions of solution additives and dissolved O2 gas on deposition kinetics, which affect deposit thickness and composition uniformity. Nevertheless, electroless deposition is experiencing increased interest in microelectronics, in part due to the need to replace expensive vacuum metallization methods with less expensive and selective deposition methods. The need to find creative deposition methods in the emerging field of nanofabrication is generating much interest in electroless deposition, at the present time more so as a useful process however, than as a subject of serious research. 

The advent of a new class of materials systems based on nanoscale particles dispersed or suspended in carrier and/or binders has captured the attention of the microelectronics technical community. These materials provide the opportunity to use inexpensive solution processing equipment versus expensive vacuum deposition equipment commonly used in the microelectronics manufacturing industry. Experts in the microelectronics industry have suggested that over the course of the next live years, the industry will experience a paradigm shift in manufacturing and, more importantly, will enjoy revenue streams created from never-before-seen products based on printed electronics. 

Perfluoropolyethers emerged on the market in the early 1970s. The first perfluoropolyether was the homopolymer of hexafluoropropylene oxide produced by DuPont, which has the structure [—CF2CF(CF3)0—] and this new lubricant material was called Krytox.31,32 Krytox was and is used in most of the vacuum pumps and diffusion oil pumps for the microelectronics industry because it does not produce any hydrocarbon or fluorocarbon vapor contamination. It also has important applications in the lubrication of computer tapes and in other data processing as well as military and space applications. 

Excimer lasers are of great importance for UV and vacuum UV (VUV) spectroscopy and photochemistry. They are also found in a wide range of applications. For example, they are used in micromachine medical devices, including refractive surgery, in photo-lithography for the microelectronics industry, for material processing, as optical pump sources for other type of lasers (dyes), and so on. More details about excimer lasers can be found in Rodhes (1979). 

Vacuum evaporation is a widely used technology for deposition of a wide variety of materials, particularly in the coatings and electronics industries. A complete discussion of this technique may be found in the classic text by Holland entitled Vacuum Deposition of Thin Films [56]. The subject is also treated in numerous texts on microelectronics [5]. Discussion here focuses on metal deposition, since this is the case most commonly encountered in the preparation of film electrodes. 

While these polymeric materials hold promise for low-cost electronics and simplified device processing, they still suffer from lower performance than conventional inorganic semiconductors. As the development of these novel materials continues, an alternative technology incorporating patterning schemes such as inkjet printing and conventional vacuum deposited thin films, may provide the required overlap of performance with low-cost fabrication of microelectronic circuits on large-area platforms. 

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