New experimental discovery of channel crystal plane and orientation selection for small-sized uniaxial strained Si PMOS

Abstract

The inversion layer mobility of small-sized uniaxial strained Si p-channel metal oxide semiconductor (PMOS) channel is closely related to the crystal plane and crystal orientation. When optimally designing the strained PMOS, the crystal plane and crystal orientation of the channel should be chosen reasonably. At present, there is a theoretical sort model for the inversion layer mobility of Si PMOS channel at 1.5 GPa stress according to the crystal plane and crystal orientation. However, in the actual manufacturing process of device, the process of covering the SiN stress film is fixed, because the channel coefficient of stiffness is aeolotropic. So, the stress intensities of strained PMOS in different crystal planes and orientation channels are different, which causes the theoretical sort model for the inversion layer mobility to be invalid. To solve this problem, the small-sized uniaxial strained Si PMOS and unstrained Si PMOS with different crystal planes and orientations are fabricated by 40 nm technological process of Chinese Academy of Sciences. The result for the inversion layer mobility of Si PMOS channel according to the crystal plane and crystal orientation is obtained by the device transfer characteristic test. Considering the process implementation factors, the relevant conclusion about the inversion layer mobility of small-sized uniaxial strained Si PMOS channel according to the crystal plane and crystal orientation is more suitable to guide the actual device manufacturing than the theoretical sort result predicted in the literature. At the same time, the relevant analysis method can also provide important technical reference for the solution of other strained material MOS.