Etching progressive

Now slowly advance the carbon fiber electrode so that the carbon fiber tip is etched progressively back toward die glass. Stop when the final length of protruding carbon fiber is about SO pm. 

A progressive etching technique (39,40), combined with x-ray diffraction analysis, revealed the presence of a number of a polytypes within a single crystal of sihcon carbide. Work using lattice imaging techniques via transmission electron microscopy has shown that a-siUcon carbide formed by transformation from the P-phase (cubic) can consist of a number of the a polytypes in a syntactic array (41). 

Surface features can also be revealed by etching, which permits identification of points of intersection of line dislocations with the surface, and this is valuable in determining the role of these imperfections in chemical processes [45,214] and, in particular, nucleus formation. Smaller topographical details can be rendered visible by the evaporation of a thin (<0.5 nm) film of gold onto the surface [215,216]. Heights and depths of surface features can be determined by interferometry [203—205]. Microcinematography has also been used [217] to record the progress of solid phase reactions. 

Cleaning SCF s such as CO2 can be used to clean and degrease quartz rods utihzed to produce optical fibers, products employed in the fabrication of printed-circuit boards, oily chips from machining operations, precision bearings in military applications, and so on. Research is in progress for removing residues in etch/ash processes in m icroelectronics. 

Figure 22. Series of mass spectra showing progression of the etching reaction of aluminum anions with oxygen. Note that magic number clusters corresponding to electron shell closings for 40 and 70 electrons (AI13 and AI23) appear as the terminal product species of reactions with oxygen at flow rates of (a) 0.0, (b) 7.5, and (c) 100.0 standard cubic centimeters per minute (seem). Taken with permission from ref. 92.

The past five years have witnessed significant progress in the understanding and control of plasma etch processes. Nevertheless, much of the fundamental chemistry and physics occurring in these reactive atmospheres remains ill-understood, or indeed unknown. The following sections assimilate the information currently available on dry etch processes, and present a framework within which plasma etching can be viewed. 

Ion implantation appears as the only feasible method to accomplish selective area doping of SiC in planar device technology. As described in this chapter, substantial progress has been made during recent years but several fundamental issues and technology barriers remain before the implantation process is fully developed and can be truly implemented in SiC device processing. Eor instance, mesa-etched p n-diodes... 

In recent progress, calixarene resists have been prominent [105]. Hexaacetate p-methylcalix[6]arene was demonstrated to work as a high-resolution negative resist. This resist also shows high etch resistance. Calixarene resist has an advantage in its molecular size (about 1 nm). Liquid crystal resists and inorganic resists show high resolution [106]. These resists are suitable for the fabrication of nanostructures. However, the resist sensitivities are lower than those of chemically amplified resists, even PMMA. 

---