Low-temperature growth of silicon-boron layer as solid diffusion source for polysilicon contacted p/sup +/-n shallow junction

A new material, Si-B, is proposed as a solid diffusion source for fabrication of poly-Si contacted p/sup +/-n shallow junctions. The junction depth of the Si-B source diode has been measured and compared with that of a BF/sub 2//sup +/-implanted poly-Si source diode. It was found that the Si-B source diode had a much shallower junction and was less sensitive to thermal budget than the BF/sub 2//sup +/ source diode. This was attributed to the smaller surface concentration and diffusivity of boron in the silicon in Si-B source diodes. Regarding electrical characteristics of diodes with a junction depth over 500 /spl Aring/, a forward ideality factor of better than 1.01 over 8 decades and a reverse-current density lower than 0.5 nA/cm/sup 2/ at -5 V were obtained. As the junction depth shrank to 300 /spl Aring/, the ideality factor and reverse current density of diodes increased slightly to 1.05 and 1.16 nA/cm/sup 2/, respectively. These results demonstrated that a uniform ultrashallow p/sup +/-n junction can be obtained by using a thin Si-B layer as a diffusion source.