pMOSFET performance of high Ge content (∼50%) biaxial compressive strained SiGe heterostructure channel pMOSFETs is characterized, and performance between 〈 110 〉 and 〈 100 〉 channel orientations on a (001) substrate is compared for physical channel lengths down to ∼80 nm. Temperature-dependent mobility and velocity are characterized for both channel directions. First, it is shown that high Ge content SiGe-based channels can deliver drive current enhancement over unstrained Si below sub-100-nm channel lengths. Second, it is found that, with a higher Ge content SiGe channel under biaxial compressive strain, there is a difference of drive current between 〈 110 〉 and〈 100 〉 channel directions, and the difference increases when temperature is lowered and/or when channel length is scaled down. An external series resistance difference is detected between two channel directions, although it appears to be insufficient to explain all the direction-dependent drive current difference. Channel transport behavior in different channel orientations can be clearly observed with low external source/drain (S/D) series resistance achieved with a millisecond S/D dopant activation anneal process while controlling the thermal budget. Two possibilities have been investigated to understand channel-direction-dependent performance: possible differences in effects of device processing impact between two channel directions and anisotropic transport effects from an anisotropic hole band structure, particularly under biaxial compressive strain in a SiGe channel pseudomorphically grown on a Si substrate.
Bibliographical noteFunding Information:
Manuscript received July 14, 2010; revised December 22, 2010; accepted January 4, 2011. Date of publication February 17, 2011; date of current version March 23, 2011. This work was supported in part by the Defense Advanced Research Projects Agency under Contract HR0011-08-1-0050. The review of this paper was arranged by Editor J. C. S. Woo.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering