ADVANCED SOURCE AND DRAIN CONTACT ENGINEERING FOR GERMANIUM-TIN AND SILICON-GERMANIUM TRANSISTORS

Abstract

Conventional Si transistors have reached fundamental limitations with the evolution of technology nodes. New channel materials, such as GeSn, and SiGe are of high promise for future p-channel transistors. Besides, a sub-1e-9 ohm-cm^2 specific contact resistivity is required in future to alleviate the impact of high contact resistance. Firstly, LTLM with the capability of eliminating parasitic metal resistance was experimentally verified on Ni/p-GeSn and Ti/p-GeSn contacts. Then, a contact resistivity down to 3.2e-10 ohm-cm^2 was extracted on in-situ B and Ga co-doped SiGe with an active doping concentration of 1.2e21 cm^-3 using LTLM after annealing. It is also found that Ga plays a vital role in achieving thermally stabled contacts. At last, as-deposited Ti/p-SiGe contact with contact resistivity of 5.1e-10 ohm-cm^2 was fabricated on the B-doped SiGe substrate with active doping of 2.5e21 cm^-3. The growth technique was successfully demonstrated on 300 mm wafers and highly scaled 3D structures.