Polycrystalline aluminum has been widely used in integrated circuits because of its high conductivity, patternability, good adherence and bondability, low cost, easy availability and ease of deposition. However, polycrystalline aluminum has poor electromigration resistance and intermixes with silicon at temperatures above 400.degree. C. To solve these problems, small amounts of copper and silicon are added into the polycrystalline aluminum. The copper, however, makes the metal alloy difficult to plasma etch. The silicon can precipitate and thus increase the electrical resistance of the metal path.
USPTO Backgrounds
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