Characteristics of polysilicon contacted shallow junction diodeformed with a stacked-amorphous-silicon film

A high-performance shallow junction diode formed with a stacked-amorphous-silicon (SAS) film is presented. Since the boundaries of stacked silicon layers and the poly/mono silicon interface act as a diffusion barrier for implanted dopants, the junction depth of SAS emitter contacted diode is about 500 Å shallower than that of the as-deposited polysilicon emitter contacted diode. The fabricated SAS emitter contacted diodes exhibited a very low reverse leakage current (⩽1 nA/cm² at -5 V) and a forward ideality factor m ≈1.001 over seven decades on a log scale. The reverse I-V characteristics were found to be nearly independent of the reverse voltage from room temperature to 200°C, and it was also found that the leakage current was due almost completely to the diffusion current. The plots of the diode leakage current versus the perimeter to area ratio showed that the periphery-generation current contributed little to the total leakage. The processing temperature for the SAS emitter contacted p⁺-n diode can be as low as 600°C