Technology Roadmaps on the Ballistic Transport in Straln Engineered Nanoscale CMO0S Devices

As device channel length continues to scale beyond 90nm, carrier transport in the ballistic regime becomes critically important. In this paper, the strain engineering and its correlation to the I_ON current enhancement of CMOS devices in the ballistic regime has been examined. It was characterized by two parameters, the ballistic transport efficiency and the injection velocity. Experimental verifications on very high mobility n- and p-MOSFET channel/substrate orientations with various strains have been made. For nMOSFETs, it shows that uniaxial tensile-stress using CESL is more efficient in current enhancement than the biaxial stress with bulk strained-SiGe technique. For the pMOSFETs, compressive stress using uniaxial or biaxial has been evaluated for various structures. It was found that both ballistic efficiency and the injection velocity can be enhanced in a specific pMOS structure with appropriate combination of CESL and biaxial strain. The technology roadmaps have then been established from advanced 65 nm CMOS devices. These results provide a guideline for designing high performance strained technology for CMOS devices in the sub-100 nm regime.