A study of fluorine implant in the formation of low leakage P+/N junction in BiCMOS technologies

As device and technologies gets shrink, ion implantation becomes very critical and important process. Fluorine is one of the dopant that is widely been studied by many researchers. One of the common defects introduced by ion implantation is End-of-Range Range (EOR) that is usually situated in the depletion region of the junction, causing a leakage current. In this paper, we reveal the effect of fluorine to the improvement of pn-junction leakage current. In previous studies, the effect of fluorine has been studied in the form of boron fluoride, BF₂ and in some works, fluorine was implanted separately to the boron, B. However in this study, F-BF₂ is used instead of F-B or BF₂ only. The purpose of the fluorine implant prior to the BF₂ is to suppress the Negative Bias Threshold Instability (NBTI) effect of this device. Besides, fluorine implant also served as pre-amorphization of the S/D implant.