Low-temperature silicon homoepitaxy by ultrahigh vacuum electron cyclotron resonance chemical vapor deposition

High quality silicon homoepitaxial layers are successfully grown at 560°C by ultrahigh vacuum electron cyclotron resonance chemical vapor deposition (UHV-ECRCVD) using a SiH₄/H₂ plasma. The effects of substrate dc bias on the in situ hydrogen plasma clean and the subsequent silicon epitaxial growth are examined by the reflection high-energy electron diffraction (RHEED), secondary ion mass spectroscopy (SIMS), and cross-section transmission electron microscopy (XTEM). It is observed that the substrate dc bias plays a significant role in obtaining a damage-free, clean Si substrate prior to epitaxial growth. Severe damage in the Si surface is observed by XTEM, though RHEED shows a streaky pattern, when the substrate is electrically floating, but the damage can be suppressed with +10 V dc bias to the substrate. Substrate dc bias during plasma deposition drastically changes the crystal structure from polycrystalline at -50 V to high quality epitaxial silicon at substrate biases greater than +50 V. Precise control of the ion energy during in situ cleaning and plasma deposition is very important in low-temperature Si epitaxy by UHV-ECRCVD and it is possible by proper control of the substrate dc bias.