Formation of Epitaxial Heavy-doped Silicon Films by PECVD Method

Abstract

Plasma-enhanced CVD (PECVD) epitaxy at 200 °C was used to deposit heavy doped n-type silicon films. Post-annealing by rapid thermal processing was applied to improve the properties of the epitaxial layer. By analyzing the Raman spectra and the imaginary part of the dielectric constant spectra of the samples, it was found that high-quality heavy-doped epitaxial n-type silicon layer can be obtained by optimizing the parameters of the PECVD depositing process. Reducing the electrodes distance of the PECVD had a great effect on the crystallzation of the epitaxialed n-type silicon films. Sillicon films with high-crystallization were obtained with the electrodes distance of 18 mm. Post-annealing process can improve the crystallization and reduce the resistance of the epitaxial films. In our research, it was found that the sheet resistance (R□) of the post-annealed films with thickness of about 50 nm has a simple relationship with RPH3/SiH4 (ratio of the flow rate of PH3 and SiH4) of the PECVD processing: R□=-184-125 lg(RPH3/SiH4). In the end, high-quality epitaxial n-type silicon film was obtained with R□ of 15 Ω/□ and thickness of ~50 nm.