EFFECTS OF PROCESS PARAMETERS ON LOW-TEMPERATURE SILICON HOMOEPITAXY BY ULTRAHIGH-VACUUM ELECTRON-CYCLOTRON-RESONANCE CHEMICAL-VAPOR-DEPOSITION

The effects of the process parameters on the low-temperature Si homoep itaxial growth in an ultrahigh-vacuum electron-cyclotron-resonance che mical-vapor-deposition (UHV-ECRCVD) system are examined by reflection high-energy electron diffraction and transmission electron microscopy (TEM). The substrate de bias during plasma deposition drastically chan ges the crystal structure from polycrystalline silicon at negative bia s 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 i on energy. The positive substrate de bias is a prerequisite for better crystallinity of low-temperature Si, but additionally the other proce ss parameters such as microwave power, distance of the ECR layer from the substrate, SiH4 partial pressure, and total pressure should be def initely optimized to obtain dislocation-free Si epilayers. Dislocation -free Si epilayers are successfully grown at 560 degrees C at the posi tive de bias greater than +10 V with the optimal control of the other process parameters. At temperatures below 470 degrees C, a high densit y of defects in the Si epilayers is observed by plan-view TEM, and the growth of the single-crystalline silicon is possible even without sub strate heating but with a high density of defects. It is concluded tha t the substrate de bias is a critical process parameter and the other process parameters do play a small but significant role as well in det ermining the crystallinity of the Si epilayers grown by UHV-ECRCVD. (C ) 1995 American Institute of Physics.