Nonuniformities of native oxides on Si(001) surfaces formed during wet chemical cleaning

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Abstract
We studied the uniformity of native oxide formed on Si(001) surfaces during wet chemical cleaning. Uniformity was determined by surface morphology at the initial stage of photoexcited fluorine etching. Since photoexcited fluorine etches Si 40 times faster than it etches Si oxide, it highlights Si native oxides on a Si surface making them observable by scanning tunneling microscopy or atomic force microscopy. Boiling in a HCl‐H2O2‐H2O (1:1:4) solution formed 30–70‐nm islands of oxides. The regions between the islands were not oxidized. Boiling in NH4OH‐H2O2‐H2O (1:1.4:4) also formed oxide islands 30–70 nm in diameter, but the interisland regions were slightly oxidized. Boiling in a HNO3 solution resulted in a native oxide with pinholes at a density of 5×109 cm−2