The thermal oxidation of silicon single crystal producer stacking faults lying on the plane.
111
What happens during thermal oxidation. Growing SiO2 on silicon consumes silicon at the Si–SiO2 interface. The oxide occupies more volume than the silicon it replaces, and the reaction is not perfectly efficient, so a supply of excess silicon self-interstitials is injected into the crystal beneath the growing oxide.
How the fault is formed. These excess interstitials become supersaturated and condense on nucleation sites (surface damage, impurity precipitates, implantation damage). Condensing interstitials form an extra half-plane of silicon atoms inserted into the lattice — an extrinsic stacking fault, bounded by a Frank partial dislocation. Faults produced this way are called oxidation-induced stacking faults (OSFs).
Why the {111} plane. Silicon has the diamond-cubic structure, whose stacking sequence (ABCABC…) is defined along the <111> direction; the {111} planes are the close-packed planes of the lattice. Inserting or removing a plane of atoms therefore costs the least energy on {111}, so that family has the lowest stacking-fault energy and is the natural habit plane for the fault. The bounding partial dislocations likewise lie in {111}. This holds regardless of the wafer surface orientation — on a (100) wafer the faults simply appear inclined to the surface.
Why it matters. Stacking faults are decorated by metallic impurities and act as generation–recombination centres, so they raise junction leakage current and degrade oxide breakdown and retention. They are suppressed by high-temperature annealing in an inert or slightly reducing ambient (which re-dissolves the interstitials), by adding chlorine (HCl/TCA) to the oxidation ambient, and by intrinsic gettering that draws impurities away from the active device region.
Hence, oxidation-induced stacking faults in single-crystal silicon lie on the {111} plane.
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