Novel intrinsic and extrinsic engineering for high-performance high-density self-aligned InGaAs MOSFETs: Precise channel thickness control and sub-40-nm metal contacts

We have fabricated self-aligned tight-pitch InGaAs Quantum-well MOSFETs (QW-MOSFETs) with scaled channel thickness (t_c) and metal contact length (L_c) by a novel fabrication process that features precise dimensional control. Impact of t_c scaling on transport, resistance and short channel effects (SCE) has been studied. A thick channel is favorable for transport, and a mobility of 8800 cm²/V·s is obtained with t_c=11 nm at N_s=2.6×10¹² cm^-2. Also, a record g_m,max of 3.1 mS/μm and R_on of 190 Ω·μm are obtained in MOSFETs with t_c=9 nm and gate length L_g=80 nm. In contrast, a thin channel is beneficial for SCE control. In a device with t_c=4 nm and L_g=80 nm, S is 111 mV/dec at V_ds= 0.5 V. For the first time, working front-end device structures with 40 nm long contacts and gate-to-gate pitch of 150 nm are demonstrated. A new method to study the resistance properties of nanoscale contacts is proposed. We derive a specific contact resistivity between the Mo contact metal and the n⁺ InGaAs cap of ρ=(8±2)×10^-9 Ω·cm². We also infer a metal-to-channel resistance of 70 Ω·μm for 40 nm long contacts.