Study Of Novel Schottky Barrier Contact Systems

As the critical dimension of modern complementary metal-oxide-semiconductor devices is continuously scaling, the urgent demand for low contact resistivity with Si as well as the emerging of new source/drain structures requires the Schottky barriers of silicide contacts on Si to be very low. Rare earth (RE) silicides with the lowest known work function (WF) were proved to have very low Schottky barrier height (SBH) on N-type silicon substrate, thus were widely focused. In the mean time, as the possible near-future application of High-k gate insulator and Schottky barrier source/drain MOSFET (SB-MOS), Silicon-Germanium (SiGe) devices have also become hot issues. In this dissertation, researches on the reliability of the admittance method for the extraction of SBH were carried out. The SBH modification mechanism of NiSi with Ytterbium (Yb) addition was analysed, and the solid-state reaction between RE metal (Yb & Er) and poly-SiGe was also carefully investigatedThe reliability of admittance measurement for the SBH extraction was investigated. The output characteristic and the admittance of the Schottky barrier diode was obtained by numeric simulation, and the SBHs extracted by both admittance and the conventional I-V fitting were compared. The I-V method becomes futile with moderately lower barrier heights (0.2-0.4eV), while the admittance method remains reliable. Admittance measurement has blunt reaction to the applied testing frequency and AC bias voltage based on experimental results, thus has better application comparing I-V fitting for SBH extraction.The influence of Yb addition on Ni silicidation was investigated. Ni(Yb) film was deposited on Si(001) substrate by co-sputtering and silicidation was performed by rapid thermal annealing (RTA). Sheet resistance of the silicide films were measured by four-point probe. X-ray diffraction and micro-Raman spectroscopy were employed to identify the silicide phases. The redistribution of Yb after RTA was characterized by Rutherford backscattering spectrometry and Auger electron spectroscopy. The influence of Yb addition on the SBH of the silicide/Si diode was examined by current-voltage measurement. The experimental results reveal that addition of Yb can suppress the formation of the high resistivity Ni₂Si phase but the formation of low resistivity NiSi phase remains unaffected. Furthermore, most of the Yb atoms accumulate to the surface layer and only a small amount of Yb atoms pile up at the silicide/Si(001) interface. It is believed that accumulation of a small amount Yb at the silicide/Si(001) interface results in the SBH reduction observed from the Ni(Yb)Si/Si diode.Research on solid-state reaction of RE metal (Yb & Er) and poly-SiGe was carried out. Poly-SiGe was fabricated by ion-beam sputtering and the subsequent rapid thermal annealing. P-type and N-type poly-SiGe were achieved by boron and phosphorus diffusion at different temperature respectively. The solid-state reaction between RE and poly-SiGe was characterized by X-ray diffraction with and without anti-oxidation cap layer. The redistribution of Yb, Si and Ge were measure by depth profiled XPS.