Simultaneous RHEED / AES study of Si film growth on Si(111) and sapphire (11̄02) surfaces

Abstract

Epitaxial growth of Si thin films deposited on the Si(111)-7 × 7 and sapphire (11̄02)-2 × 1 substrate surfaces are studied by using a new combined system at substrate temperatures ranging from 30 to 1100°C. The role of simultaneous measurement of chemical composition of the surface by Auger electron spectroscopy and residual gas analysis by quadrupole mass spectrometry during observation of RHEED patterns is illustrated. The 7×7 structure of the Si(111) fades with increasing thickness of deposited film. The integral order spots corresponding to the Si bulk structure become streaky and change into broad spots after a film of 150 Å thickness is deposited at a substrate temperature of 800°C. The fact that partially ionized vapor deposition (PIVD) prefers epitxial growth is also demonstrated, whereas the ion concentration ratio and ion energy are only 0.5% and 100 eV respectively. The RHEED pattern corresponding to the 2 × 1 structure of atomically clean sapphire (11̄02) surface disappears after deposition of up to 10 Å at a substrate temperature of 30°C. However, it remains unchanged, at least for films of thickness up to 100 Å, when deposition is made at a substrate temperature of 1100°C, and the mass peaks of m e 27(Al +) and 44(SiO +) increase markedly. A postulated reaction mechanism between Al 2O 3 and impinging Si is discussed.