United States Patent 3,497,407
February 24, 1970

Etching Of Semiconductor Coatings Of SiO2
Ronald P. Esch
William A. Plliskin

Filed December 28, 1966
Image of US PATENT 3,497,407

Abstract of the Disclosure

An etchant solution of monobasic ammonium phosphate (NH4H2PO4) and ammonium fluoride (NH4F) to enable a controlled cleanup etching of oxides from the surfaces of diffused regions in semiconductor devices masked by a composite layer of an oxide film overlaid with a diffusant-formed glassy coating. The solution produces a controlled etch wherein the etch rates of the diffusant-formed glass to the oxide is kept at a minimum. The solution is intrinsically buffered by the components to maintain a high pH, i.e. a very nearly neutral solution which is slightly acidic.
Figure descriptions: cover graphic

  • Figures 1A to 1E are sectional views representing a portion of an array of semiconductor devices during various steps and the manufacturing thereof.
  • Figure 2 is a generalized etch-rate plot superimposed over a cross-section of a semiconductor device sequentially coated with an oxide layer and a diffusant-formed glassy layer.

 Citations [54]:
3,107,188 10,1963 Hancock 3,322,611 12/1965 Haenichen
National Museum of American History
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