Substrate Effects on the Epitaxial Growth of AlN Thin Films Using Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Desposition

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Abstract
Highly c-axis oriented AlN films were fabricated on various substrates by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) at a substrate temperature of 500°C. The degree of c-axis orientation depends sensitively on the substrate: the standard deviations σ of AlN(0002) rocking curve peaks are 4.9°, 4.8°, 4.3°, 4.0° and 1.5° on SiO2, Si3N4, Si(100), Si(111) and α-Al2O3(0001) substrates, respectively. The amorphous interfacial silicon oxide layer on Si substrate has an important effect on the degree of c-axis orientation and in-plane alignment of the AlN film. The AlN films prepared by ECR PECVD have much lower surface roughness (R RMS=1.1–1.9 nm) than the sputter-deposited films (R RMS=3.0–9.0 nm), which offers lower propagation loss in SAW devices.