Etching a substrate: processes – Nongaseous phase etching of substrate – Etching inorganic substrate
Reexamination Certificate
2006-01-23
2010-10-12
Ahmed, Shamim (Department: 1713)
Etching a substrate: processes
Nongaseous phase etching of substrate
Etching inorganic substrate
C216S083000, C216S103000, C438S745000, C438S753000
Reexamination Certificate
active
07811464
ABSTRACT:
There is provided a preferential etching method wherein a preferential etchant which contains at least a hydrofluoric acid whose composition by volume falls within the range of 0.02 to 0.1, a nitric acid whose composition by volume falls within the range of 0.5 to 0.6, an acetic acid whose composition by volume falls within the range of 0.2 to 0.25, and water is used to etch a silicon single crystal substrate whose electrical resistivity is less than 10 mΩ·cm at a rate higher than 0.1 μm/min, thereby eliciting BMDs on a surface of the silicon single crystal substrate. As a result, the preferential etching method that can evaluate and utilize characteristics of crystal defects, especially BMDs in an ultralow-resistance silicon single crystal substrate whose electrical resistivity is less than 10 mΩ·cm, which cannot be readily detected by conventional techniques, by performing preferential etching using a chromeless etchant containing no harmful chrome can be provided.
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Ahmed Shamim
Oliff & Berridg,e PLC
Shin-Etsu Handotai & Co., Ltd.
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