High dose rate effects in silicon by plasma source ion implantation

An investigation of high dose rate effects in silicon subsurface morphology has been performed. The unique capability of plasma source ion implantatio n to operate in the high current/low energy regime, where the near-surface structure can be effectively controlled, has been studied. At an ion energy of similar to 40 keV and an estimated dose of 1 x 10(15) cm(-2) Ar ions we re implanted at various instantaneous dose rates (0.75-8.3 mA/cm(2)) and tw o different pulse widths (25-50 mu s) into 2 in. diam silicon wafers at a c onstant repetition rate of 10 Hz. The irradiation damage to the wafers' str uctures was characterized by Rutherford backscattering spectrometry (RBS) a nd transmission electron microscopy (TEM). A visual observation indicated a morphization of the silicon at 0.75 mA/cm(2) but not at 8.3 mA/cm(2). The t ransition from the crystalline-to-amorphous phase was confirmed by TEM elec tron diffraction studies. RES data, however, indicated there was a large di screpancy in the total dose retained between the high dose rate (8.3 mA/cm2 ) and the low dose rate (0.75 mA/cm2). Two simulation methods for the subst rate temperature profile have been compared to predict the profile. A compa rison of the fraction of irradiation damage from the RES data indicated tha t the substrate heating effects are more dominant then the dose rate effect s. Improved methods of cooling the wafer are presently being investigated. (C) 1999 American Vacuum Society. [S0734-211X(99)05302-0].