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.
The effects of the process parameters on the low-temperature Si homoepitaxial growth in an ultrahigh-vacuum electron-cyclotron-resonance chemical-vapor-deposition (UHV-ECRCVD) system are examined by reflection high-energy electron diffraction and transmission electron microscopy (TEM). The substrate dc bias during plasma deposition drastically changes the crystal structure from polycrystalline silicon at negative bias to single crystalline at positive bias. The defect production during plasma deposition is mainly caused by the energetic ions impinging on the Si substrate, and it can be effectively suppressed by the proper control of the process parameters in the direction of minimizing the ion energy. The positive substrate dc bias is a prerequisite for better crystallinity of low-temperature Si, but additionally the other process parameters such as microwave power, distance of the ECR layer from the substrate, SiH4 partial pressure, and total pressure should be definitely optimized to obtain dislocation-free Si epilayers. Dislocation-free Si epilayers are successfully grown at 560 °C at the positive dc bias greater than +10 V with the optimal control of the other process parameters. At temperatures below 470 °C, a high density of defects in the Si epilayers is observed by plan-view TEM, and the growth of the single-crystalline silicon is possible even without substrate heating but with a high density of defects. It is concluded that the substrate dc bias is a critical process parameter and the other process parameters do play a small but significant role as well in determining the crystallinity of the Si epilayers grown by UHV-ECRCVD.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.