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Preferential Lateral Chemical Etching in Reactive Ion Etching of Aluminum and Aluminum Alloys. Reactive ion etching of Al and its alloys in CCI,/Ar plasmas produces vertical etch profiles and residue-free etch regions. However, under certain conditions, preferential lateral chemical etching occurs, which produces pits in the surface of the metal along the edges of the lands. The lateral etching is due to a thermally activated process and is related to the structure of the films. The extent of attack can be reduced by annealing the films at 450ยฐC before etching. Aluminum4opper films deposited onto heated substrates are more susceptible to attack than those evaporated at lower temp. This apparent contradiction has not been resolved. The effects of etching temp., plasma parameters and film structure are discussed. Scavenging of the responsible species by additions of H or 0 to plasma is not successful.-AA P.M. Schaible, and G.C. Schwartz. J. Vac. Sci. Techno/., Mar.-Apr. 1979, 16, (2). 377-380, [in English].
80-0885
The Use of Titanium in the Aerogpace Industry. The aerospace industry uses, due to generally high stresses in materials, besides several grades of commercially pure Ti, mainly Ti alloys of the a and a + p types.
Beta type Ti alloys have not gained real importance so far. While commercially pure Ti finds application, preferably as formed sheet parts, Ti alloys are used as sheets only to a smaller extent. Their most important fields are plates up to -100 m m thick, forged and rolled rings, all for machining, hubs, fasteners and die forgings for which producers of semifinished products supply bar stock in the size range from 15 to 3 5 0 m m dia. Precision castings are not yet of much importance in the aerospace industry.