Comparative study of Si precipitation in silicon-rich oxide films

Two techniques often used in semiconductor industry, namely, low-pressure chemical vapour deposition (LPCVD) and plasma enhanced chemical vapour deposition (PECVD), were used to deposit silicon-rich oxide layers. Thermal treatments have been performed to promote Si precipitation. The composition of the layers was monitored by X-ray photoelectron spectroscopy showing significant nitrogen content (∼8%) only in PECVD layers. The formation of Si nanoclusters has been evidenced by Raman spectroscopy and photoluminescence measurements. LPCVD layers revealed a precipitation even in the as deposited films, and a phase separation was achieved at 1100∘C, while the clusters remain amorphous for PECVD grown films. Electron images of the films revealed an average size of the Si clusters of 3-5 nm with a density around 5×1017cm-3. The optimum temperature for a strong near-infrared emission from Si precipitates was found around 1100∘C for LPCVD and 1250∘C for PECVD layers.