Fine-tuning of the interface in high-quality epitaxial silicon films deposited by plasma-enhanced chemical vapor deposition at 200 °C

High-quality epitaxial silicon thin films have been deposited by plasma-enhanced chemical vapor deposition (PECVD) at 200 degrees C in a standard radiofrequency (RF) PECVD reactor. We optimized a silicon tetrafluoride (SiF4) plasma to clean the surface of <100> crystalline silicon wafers and without breaking vacuum, an epitaxial silicon film was grown from SiF4, hydrogen (H-2), and argon (Ar) gas mixtures. We demonstrate that the H-2/SiF4 flow rate ratio is a key parameter to grow high-quality epitaxial silicon films. Moreover, by changing this ratio, we can fine-tune the composition of the interface between the crystalline silicon (c-Si) wafer and the epitaxial film. In this way, at low values of the H-2/SiF4 flow rate ratio, an abrupt interface is achieved. On the contrary, by increasing this ratio we can obtain a porous and fragile interface layer, composed of hydrogen-rich microcavities, which allows the transfer of the epitaxial film to foreign substrates.