Electrical characterization of Ar-ion-bombardment-induced damage in Au/Si and PtSi/Si Schottky barrier contacts

Au/Si and PtSi/Si Schottky contacts were prepared on n-Si(100) substrates which had been previously subjected to an Ar ion bombardment with well defined energies ranging from 100 eV to 1.5 keV. Samples were investigated by current-voltage (I-V) measurements, ballistic electron emission microscopy (BEEM) and deep-level transient: spectroscopy (DLTS). Both I-V and BEEM results show that the effective Schottky barrier height (SBH) decreases with increasing Ar ion energy. The lowering of the barrier height is attributed to the bombardment-induced donor-like defects with relatively high densities near the silicon surface, DLTS spectra show the presence of defect levels both in the form of discrete energy levels and as a continuum of states. The oxygen-vacancy pair located at 0.16 eV below the conduction band is the dominant defect for the samples bombarded by 100 and 200 eV Ar ions and its peak signal intensity is similar for the two energies. For 300 eV or higher-energy ion-bombarded samples, other defects develop and become dominant. Their peak signal intensities increase monotonically with Ar ion energy. The variation of the DLTS spectra is in qualitative agreement with the tendency of effective SBH lowering for increasing energy of the bombarding Ar ions.