Nickel Alloys (nipt, Nial, Niy) Silicide By Solid State Reaction With Si Schottky Contact Characteristics Of Study

As the development of complementary metal-oxide-semiconductor (CMOS) technology, the gate process has evolved from poly-silicon to poly silicide and then self align silicide, and NiSi seems to be the most promising candidate material concerning silicon consumption, thermal budget and resistivity. To achieve adjustable work function for NiSi used in the gate, nickel based alloy silicides were researched recently. Here we present our research on Ni-Pt, Ni-Al, and Ni-Al alloy reaction with silicon and Schottky barrier property, including:(1). Study of Ni-Si reaction with a thin Pt interfacial layer. 2nm Pt and 20nm Ni were sequentially sputtered on n-Si(100) substrates and annealed afterwards for silicidation. Four point probe and XRD were used to detect the phases formed and current-voltage (I-V) measurements were used to extract Schottky barrier height and its variation in different temperatures. It's revealed that such a 2nm Pt layer significantly improved the thermal stability of NiSi after high temperature annealing. A double Gaussian distribution can well explain the distribution of barrier height and the apparent barrier height variation on temperature. Also the barrier height rise near 0.3eV on n Si for 500℃annealing samples.(2). Study of Ni-Si with a 10nm Al layer in different position. XRD and FPP were used for phase detection and IV for Schottky barrier height extraction. No Ni-Al or Al-Si compounds were detected in any samples and the Al layer retarded the formation of NiSi in low temperature annealing. The Al was also detected as the dominant diffusion species in the Ni-Al system, and no Al founded in the interfacial layer after fully silicidation, no significant Schottky barrier height modulation founded.(3). Study of Ni-Si reaction with different amount of Y. Ni/Y/Ni structure was sputtered on p-Si(100) substrate with a Ti(20nm)/TiN(40nm) capping layer. FPP and XRD revealed that such capping layer can effectively protect the formed silicide and be easily etched for H₂SO₄ and H₂O₂ mixture solution. The addition of Y doesn't effect the formation of NiSi, and the Y accumulated in the top of the formed NiSi layer, no Y existed in the interfacial layer. No significant Schottky barrier height modulation detected for both Y account samples.