High-Performance InAs-On-Insulator n-MOSFETs With Ni-InGaAs S/D Realized by Contact Resistance Reduction Technology

We have systematically analyzed the components of source/drain (S/D) resistance (RSD) in InGaAs n-MOSFETs with Ni-InGaAs metal S/D. It is found that Ni-InGaAs has a low resistivity of ~250 μΩ·cm in a thickness of Ni-InGaAs (TNi-InGaAs) of down to ~4 nm. Contact resistance between the contact pads and Ni-InGaAs (RC) is found to be the most dominant component of RSDin control InGaAs MOSFETs, because of the existence of Ni oxides. By developing a surface cleaning process using NH4OH and H2plasma for Ni-InGaAs surfaces, we have reduced RCdown to 11 Ω·μm without any accompanying drawbacks. Also, the increase in the channel indium (In) content has provided further RSDreduction. Employing these RSDreduction technologies, we present 20-nm-channel length (Lch) InAs-on-insulator n-MOSFETs on Si substrates with Ni-InGaAs metal S/D. The devices provide a high maximum ON-current (ION) and maximum transconductance (Gm) of 2.38 mA/μm and 1.95 mS/μm at drain voltage (VD) of 0.5 V. This high performance is attributable to the low RSDrealized by the surface cleaning process of Ni-InGaAs surfaces before the contact pad formation as well as the increase in the In content in the channel layer. Furthermore, it is found that the interface resistance (Rinterface) between Ni-InGaAs and InGaAs channels can be reduced down to 50 Ω·μm by increasing the In content in the channel layers.