LOW-TEMPERATURE SILICON HOMOEPITAXY BY ULTRAHIGH-VACUUM ELECTRON-CYCLOTRON-RESONANCE CHEMICAL-VAPOR-DEPOSITION

High quality silicon homoepitaxial layers are successfully grown at 56 0-degrees-C by ultrahigh vacuum electron cyclotron resonance chemical vapor deposition (UHV-ECRCVD) using a SiH4/H-2 plasma. The effects of substrate dc bias on the in situ hydrogen plasma clean and the subsequ ent silicon epitaxial growth are examined by the reflection high-energ y electron diffraction (RHEED), secondary ion mass spectroscopy (SIMS) , and cross-section transmission electron microscopy (X-TEM). It is ob served that the substrate dc bias plays a significant role in obtainin g a damage-free, clean Si substrate prior to epitaxial growth. Severe damage in the Si surface is observed by XTEM, though RHEED shows a str eaky pattern, when the substrate is electrically floating, but the dam age can be suppressed with +10 V dc bias to the substrate. Substrate d c bias during plasma deposition drastically changes the crystal struct ure from polycrystalline at -50 V to high quality epitaxial silicon at substrate biases greater than +50 V. Precise control of the ion energ y during in situ cleaning and plasma deposition is very important in l ow-temperature Si epitaxy by UHV-ECRCVD and it is possible by proper c ontrol of the substrate dc bias.