Search

Al-induced crystallization of an amorphous Si (a-Si) thin film in a polycrystalline Al/native SiO2/a-Si structure has been investigated on an atomic level using cross-sectional high-resolution transmission electron microscopy. A 7-nm polycrystalline Al layer was thermally deposited onto a 50-nm a-Si thin film, deposited by low-pressure chemical vapor deposition and covered with a 2.2-nm layer of native SiO2. The a-Si thin film in this structure was partially crystallized at 250°Cand completely crystallized at 500°C after 30 min. Lattice fringes of Si(111) were observed in the original Al layer and interfacial native SiO2layer after the annealing process. From the above results, it was concluded that Al-induced crystallization of the a-Si thin film occurred by interdiffusion of Al and Si atoms through the native oxide layer even though the 2.2-nm native SiO2layer was not removed completely at the Al/a-Si interface. A possible model, that can be used to explain the Al-induced crystallization phenomena by taking into account the changes that take place within or near the native SiO2layer during the annealing process, was proposed.

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 ? 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 ?-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 (RRMS=1.1-1.9 nm) than the sputter-deposited films (RRMS=3.0-9.0 nm), which offers lower propagation loss in SAW devices.