Improvement of Thermal Stability of Ni Germanide Using a Ni–Pt(1%) Alloy on Ge-on-Si Substrate for Nanoscale Ge MOSFETs

In this paper, thermally stable Ni germanide using a Ni-Pt(1%) alloy and TiN capping layer is proposed for high-performance Ge MOSFETs. The proposed Ni-Pt(1%) alloy structure exhibits low-temperature germanidation with a wide temperature window for rapid thermal processing. Moreover, sheet resistance is stable and the germanide interface shows less agglomeration despite high-temperature postgermanidation anneal up to 550 ^??C for 30 min. In addition, the surface of the Ni-Pt(1%) alloy structure is smoother than that of a pure Ni structure both before and after the postgermanidation anneal. Only the NiGe phase and no other phases such as Pt_xGe_y and Ni_xPt_1-xGe_y can be observed in X-ray diffraction results, but X-ray photoelectron spectroscopy shows that PtGe is formed during the postgermanidation anneal. The larger Pt atomic radius is believed to inhibit the diffusion of Ni into the Si substrate, thereby improving the thermal stability of the NiGe. The higher melting point of PtGe is also believed to improve thermal stability. Therefore, this proposed Ni-Pt(1%) alloy could be promising for high-mobility Ge MOSFET applications.