Damage-free cleaning of Si(001) using glancing-angle ion bombardment

The effects of glancing-angle argon ion bombardment on air-contaminated Si(001) surfaces were studied. Bombarding at substrate temperature Ts=730 °C, impingement angle φ=3–15° relative to the surface plane, ion energy E=1 keV and dose D=3×1015 ions cm−2 gave high-quality reflection high energy electron diffraction (RHEED) patterns and contaminant-free surfaces as observed by ion scattering spectroscopy. Atomic force microscopy images showed roughness value ⩽0.5 nm under these conditions, but the roughness increased and RHEED patterns became spotty for higher doses or energies. Secco etching of samples bombarded at Ts=730 °C showed etch pits with a density of 106–107 cm−2 that increased with increasing D and E. Room-temperature bombardment with E=1 keV, D=3×1015 ions cm−2 and φ=3°, followed by a 730 °C anneal, yielded a lowest roughness value of 0.2 nm. Secco etching showed no resolvable pits, indicating a dislocation density <4×104 cm−2.