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.

• 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.

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3,107,188  10,1963  Hancock
3,322,611  12/1965  Haenichen