Chromium films

Optical Lithography. Optical Hthography uses visible or ultraviolet light as the exposure media, and is the dominant Hthographic process used for patterning IC wafers. The linewidth limit is near 0.4 p.m, although some narrower features may be possible (34). The masks typically are made from patterned, opaque chromium films on glass. 

Cobalt—chromium films (20 at. % Cr) exhibiting strong perpendicular anisotropy, ie, hexagonal i -axis normal to the substrate surface, have been studied (53). Fifty nanometer films are composed of columnar crystaUites and the domain size was found to be a few stmctural columns in diameter. Magnetization reversal was shown to occur by domain rotation in thick films. Thinner (ca 10-nm thick) films do not show the columnar crystaUite... 

The resist has been used as a mask in wet etching and in lift-off processes, and more recently in etching chromium films in a chlorine-oxygen-helium plasma. In the latter, the etch rates have ranged from 4 to 5.5nm/min at lOOW power in a barrel type reactor. Chromium etches at about 6.5nm/min under these conditions. The etch rate of the resist appears to be independent of the degree to which it has been cured before exposure, so the sensitive form described here is just as effective a mask as the highly cross-linked resists described earlier, at least in the chromium etching process. 

Belertser et al (1988) have observed that the electrical resistivity of amorphous chromium films at liquid-helium temperatures jumps from a value (10 3 O cm) characteristic of a poor metal by a factor 103, when the hydrogen content is increased sufficiently to increase the lattice constant by 10%. The transition is not abrupt, and is thought by these authors to be of Anderson type. They claim that it is the first time such a transition has been observed in a solid, and that it is similar to that in expanded mercury vapour (Section 4). 

The electrodeposition of chromium in a mixture of choline chloride and chromium(III) chloride hexahydrate has been reported recently [39]. A dark green, viscous liquid is obtained by mixing choline chloride with chromium(III) chloride hexahydrate and the physical properties of this deep eutectic solvent are characteristic of an ionic liquid. The eutectic composition is found to be 1 2 choline chloride/chromium chloride. From this ionic liquid chromium can be electrode-posited efficiently to yield a crack-free deposit [39]. Addition of LiCl to the choline chloride-CrCl3-6H20 liquid was found to allow the deposition of nanocrystalline black chromium films [40], The use of this ionic liquid might offer an environmentally friendly process for electrodeposition of chromium instead of the current chromic acid-based baths. However, some efforts are still necessary to get shining... 

The use of static SIMS for the characterization of surfaces of polypropylene (PP), PTFE and a PMDA-ODA type poly-imide is described. Interfaces between evaporated copper or chromium films onto PTFE and polyimide were also analyzed. Some of the polymer substrates were modified by ion beams, corona discharge in air or plasma treatments in air, At and H2. It is demonstrated that SIMS is highly complementary to XPS for the analysis of such modified surfaces, in that effects such as crosslinking, unsaturation and formation of low-molecular weight material at surfaces can be detected. 

Chromium has been investigated as a coating for steel cans. The thickness of the chromium film is determined by dissolving a sample of a can in acid and oxidizing the resulting Cr3+ to Cr2072- with the peroxydisulfate ion ... 

It has been shown that hardness of fine grain chromium films and coatings produced by physical evaporation, hollow cathode discharge and magnetron sputtering may reach the values of 15000 - 26000 MPa that is more 9-10 times higher in comparison with cast chromium [1-3],... 

It can be seen from Fig.3 that chromium films differ from molybdenum films in the mechanical behavior essentially. So, unloading curve for chromium at depth about 330 nm shows displacement discontinuity that, as is known, testifies to phase transition in silicon under loading (a metal phase of high pressure Si II [6]). On unloading curve for molybdenum the phase transition in silicon is not fixed. Besides average contact pressure in molybdenum film is lower, than in a chromium film more than in 2 times and this distinction increases with reduction of depth of contact. 

A major problem in automotive vehicles is corrosion control, particularly in the northern areas of the country where salts are used to melt road ice. Protection of exposed steel from corrosion is accomplished by electroplating with copper-nickel-chromium films, particularly on trim and finish moldings. Electrophoretic painting of body panels is used industry-wide, and electrogalvanizing to protect steel under paint is soon to become a standard practice for all vehicles. Electrochemical accelerated tests for the integrity of coatings and for the determination of the concentration of coolants are used extensively. 

Physically, the adhesion of a thin metallic film on the substrate may not be strong, but the adhesion can be enhanced using an intermediate metallic film. For instance, the deposition of a platinum or gold thin film on a silicon substrate is often accomplished by first depositing a thin layer of titanium or chromium. The titanium or chromium film enhances the adhesion of the platinum or gold film onto the substrate. However, electrochemically, these titanium or chromium layers may participate in sensing element reactions. This may yield unexpected results, and careful examination of the electrode reaction(s) and experimental results is needed. 

Figure 16.4 Typical chemical etching steps in microfabrication processing step 1, deposition of chrome, gold metallic films, and photoresist film step 2, application of mask under UV light to polymerize the photoresist film step 3, chemical removal of unpolymerized photoresist step 4, chemical etching of unprotected gold film step 5, chemical etching of unprotected chromium film step 6, chemical removal of photoresist film.

The information available on the CO-chromium system is extremely sparse. Wagener (3J) reported that on evaporated chromium films the... 

Chromium films can be deposited by the pyrolysis of chromium hexacarbonyl ... 

Table 13.3 Optical characteristics of chromium films at different lithographic wavelengths. ...

See, for example, Chromium etchants applications notes, Cyanetek Corp., Fremont, CA [cited in H.J. Levinson, Principles of Lithography, 2nd ed., p. 261, SPIE Press, Bellingham, WA (2005)]. B.J. Curtis, H.R. Brunner, andM. Ebnoether, Plasma processing of thin chromium films for photo masks, J. Electrochem. Soc. 130(11), 2242 2249 (1983). 

Hwang, C., Laughlin, D. E., Mitchell, P. V., Layadi, A., Mountfield, K., Snyder, J. E. Artman, J. O. (1986). TME investigation of cobalt-chromium film microstructure. Journal of Magnetism and Magnetic Materials, 54-57,1676-8. 

In order to study in detail the mechanism of formation of a structure and phase composition of chromium film deposited under the nitrogen ion bombardment, the electron microscopic analysis of the objects whose thickness is <60 nm should be done. A precondition for the analysis of the grain... 

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