Microelectronics processes, plasma

Figure 3-8 Raman microprobe spectrum of fluorinated hydrocarbon contaminant on silicon wafer that had been polished and plasma-etched (lower) and Raman spectrum of polytetrafluoro-ethylene (upper). Laser, 135 mW at 514.5 nm. Slits, 300 jon. Time, 0.5 s per data point. (Reproduced with permission from Adar, F., in Microelectronics Processing Inorganic Materials Characterization (L. A. Casper, ed.), ACS Symposium Series Vol. 295, pp. 230-239. American Chemical Society, Washington, D.C., 1986. Copyright 1986 American Chemical Society.)...

Reif. R.. Plasma enhanced chemical vapor deposition of thin films for microelectronics processing. In Handbook of Plasma Processing Technology Fundamentals, Etching, Deposition, and Surface Interactions, (Rossnagel, S. M., Cuomo, J. J., and Westwood, W. D., Noyes, Eds.), Park Ridge, NJ, 1990. 

J. Houskova, K.N. Ho, M.K. Balazs, "Characterization of Components in Plasma Phosphorus Doped Oxides", ACS Symposium on Materials Characterization in Microelectronics Processing (ACS National Meeting), St. Louis, 1984. 

Microelectronics, including plasma and electrochemical surface processing... 

For thin-film metallization, a thin metallic film is first deposited onto the surface of the substrate. The deposition can be accomplished by thermal evaporation, electronic-beam- or plasma-assisted sputtering, or ion-beam coating techniques, all standard microelectronic processes. A silicon wafer is the most commonly used substrate for thin-film sensor fabrication. Other substrate materials such as glass, quartz, and alumina can also be used. The adhesion of the thin metallic film to the substrate can be enhanced by using a selected metallic film. For example, the formation of gold film on silicon can be enhanced by first depositing a thin layer of chromium onto the substrate. This procedure is also a common practice in microelectronic processing. However, as noted above, this thin chromium layer may unintentionally participate in the electrode reaction. 

In addition to the chemical etching method described above, other etching methods such as chemical anisotropic etching, and reactive plasma etching, may also be used to define the geometric configuration of the sensor element. These etching techniques are also established microelectronic processes and are extensively described elsewhere [6]. 

Plasmas are used in three major microelectronics processes sputtering, plasma enhanced chemical vapor deposition (PECVD), and plasma etching. In each, the plasma is used as a source of ions and/or reactive neutrals and is sustained in a reactor so as to control the flux of neutrals and ions to a surface. The typical ranges of properties for a glow discharge used in microelectronic fabrication are as shown in Table I. 

In microelectronic fabrication processes, plasma etching is used to create the patterns of silicon-based thin films (sil-... 

In plasma-assisted CVD, an electrostatically or electromagnetically induced plasma discharge is carried out in a low pressure system. The result is that the process may be operated at a considerably lower temperature. This has been employed in the deposition of SiOj and Si3N4 in the production of heat-sensitive microelectronic circuits. 

In thin film processes for microelectronic applications, we deal almost exclusively with glow discharges. These plasmas are characterized by pressures in the range of 50 mTorr to 5 Torr, electron densities between 10 and 10 cm , and average electron energies between 1 and 10 eV (such ener-... 

Other CVD Processes. CVD also finds extensive use in the production of protective coatings (44,45) and in the manufacture of optical fibers (46-48). Whereas the important question in the deposition of protective coatings is analogous to that in microelectronics (i.e., the deposition of a coherent, uniform film), the fabrication of optical fibers by CVD is fundamentally different. This process involves gas-phase nucleation and transport of the aerosol particles to the fiber surface by thermophoresis (49, 50). Heating the deposited particle layer consolidates it into the fiber structure. Often, a thermal plasma is used to enhance the thermophoretic transport of the particles to the fiber walls (48, 51). The gas-phase nucleation is detrimental to other CVD processes in which thin, uniform solid films are desired. 

Another promising area for polymer development, as alluded to by Tirrell [5], is microelectronics. Plasma polymerization can be used to produce a polymeric coating directly on a substrate changing the composition of the gas feed allows a wide variation in the chemical composition of the surface produced [32], The same technique can also be used to modify surfaces for other applications, such as to improve the blood compatibility of biomaterials. The essential processes occurring in a plasma—mass transfer and reaction kinetics—have long been the domain of chemical engineers. 

Lifetime depth profiles will be useful for the detection of inhomogeneous pore size distributions and in tracking impurities. For microelectronic device fabrication it is crucial that subsequent processing steps do not alter the deposited porous layers. The case presented above of oxygen plasma treatment is just one example. A lifetime depth profile could provide direct evidence for the changes in pore sizes discussed in the work on HSSQ samples and oxygen plasma treatment [22]. Gidley et al have carried out similar depth profiles [74]. 

Fluorine-based plasmas are currently employed in microelectronics industry for etching processes of metal (W), semiconductors (Si, Ge), or dielectrics (Si02, Si3N4). Mechanistic studies have shown that the key parameters of the plasma-surface inter-... 

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