New Study on Experimental and Theoretical Mobility Sorts for Crystal Planes and Orientations of Small-Sized Uniaxial Strained Si NMOS Channel

摘要

The uniaxial stress can enhance the electronic mobility through changing the band-structure of silicon. When the uniaxial stress is applied to silicon, the stress intensity of NMOS channel in different crystal planes and orientations is different, which leads the inversion layer mobility of small-sized uniaxial strained Si NMOS channel would be closely related to the crystal planes and crystal orientations. So that, the crystal planes and crystal orientations of the channel should be chosen reasonably when optimally design the strained NMOS. At present, there are some theoretical sort models for the inversion layer mobility of uniaxial strained and unstrained Si NMOS channel according to the crystal plane and crystal orientation, however, they are all scattered and lack of comprehensive comparison on experiment. In manufacturing process of device, because the channel coefficient of stiffness is aeolotropism but the process of covering the SiN stress film is fixed. Therefore, the stress intensity of small-sized uniaxial strained Si NMOS channel in different crystal planes and orientations is different under the same process, which leads the theoretical sorting model for the inversion layer mobility of uniaxial strained and unstrained Si NMOS channel according to the crystal plane and crystal orientation invalid. To solve this problem, in this paper the small-sized uniaxial strained Si NMOS and unstrained Si NMOS with different crystal planes and orientations were fabricated by 40 nm process of Chinese Academy of Sciences. The experimental sorting results for the inversion layer mobility of Si NMOS channel according to the crystal plane and crystal orientation was obtained by the device transfer characteristic test. Considered the process factors, the related conclusions about the inversion layer mobility of small-sized uniaxial strained Si NMOS channel according to the crystal planes and crystal orientations are more suitable to guide the actual device manufacturing than the theoretical sorting results. At the same time, the relevant analysis methods can also provide important technical reference for the solution of other strained MOS in different materials.