United States Patent 4,180,439
December 25, 1979

Anodic Etching Method for the Detection of Electrically Active Defects in Silicon
John L. Deines
Michael R. Poponiak
Robert O. Schwenker

Filed July 25, 1977
Image of US PATENT 4,180,439

Abstract of the Disclosure

Electrically active defects, i.e., current-carrying defects or leakage paths in silicon crystals, are detected by an anodization process. The process selectively etches the crystal surface only where the electrically active defects are located when the anodization parameters are properly selected. Selected surface portions of the silicon structure are exposed to a hydrofluoric acid solution which is maintained at a negative potential with respect to the silicon structure. When the potential difference is set to a proper value, etch pits are formed in the sruface of the silicon only at those locations overlying electrically active defects which impact device yield. The defects are observed and counted to provide a basis to predict yield of desired semi-conductor devices to be formed later in the silicon structure.
Figure descriptions: cover graphic

    an out-of-scale enlargement of a portion of the silicon wafer in the apparatus employed in the performance of the method of the present invention.

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National Museum of American History
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