Performance and reliability investigation of (110) and (100) sidewall oriented MugFETs

Summary form only given. In order to continue technology scaling to meet future performance needs, multi-gate field effect transistors (MugFETs), are currently under investigation. MugFETs can be fabricated on silicon-on-insulator (SOI), and they are especially attractive because their three-dimensional structure enables excellent immunity to short channel effects, without significant changes to conventional CMOS fabrication techniques. One MugFET design of interest is known as the FinFET, where a hard mask is placed on the top surface of a fin structure to decouple it from the sidewall device operation (fig. 1). FinFETs can be fabricated with either the (110) sidewall surface or (100) sidewall where the crystal orientation of the fin sidewalls can have an impact on mobility and thereby provide a mobility boost based on orientation (fig. 1) [1,2]. In planar CMOS technologies, orientation dependent mobility enhancement has been demonstrated through the use of hybrid orientation technology (HOT) [3,4]. Here, hole (h⁺) mobility (μ_eff) increases significantly when the channel orientation changed from Si(100) to Si(110). However, the electron (e^-) mobility is severely degraded with the same orientation change. Therefore, there arises a need for HOT to take advantage of h⁺ μ_eff on Si(110) and e^- μ_eff on Si(100). Our work demonstrates that the nMOS FinFET devices actually are not as severely degraded as planar nMOS, thereby mitigating the need to have orientation dependent CMOS FinFETs for μ_eff enhancement (fig. 2) [5]. However, a correlation of long channel mobility to short channel performance is necessary to confirm similar performance characteristics (fig. 3). Moreover, the implications of sidewall surface orientation on reliability issues such as hot carriers [6,7] and bias temperature instability [8,9] also need to be addressed. The surface orienta- ion or fin structure may be more susceptible to degradation during stress. Possible causes include: Si interface bonds available for bond breakage [10] in the (110) plane, or structural properties that impact reliability differently than planar devices. In this work, we evaluate the dependence of FinFET sidewall orientation on performance (i.e., mobility and I_on/I_off) and reliability, where hot carrier injection and BTI are evaluated.