Investigation of Device Characteristics on the Mechanical Film Stress of Contact Etch Stop Layer in Nano-Scale CMOSFET

In this paper, the dependence of MOSFET performance on the channel stress is characterized in depth. The tensile and compressive stresses are applied to CMOSFET using a nitride film which is used for the contact etch stop layer (CESL). Drain current of NMOS and PMOS is increased by inducing tensile and compressive stress, respectively, due to the increased mobility as well known. In case of NMOS with tensile stress, both decrease of the back scattering ratio () and increase of the thermal injection velocity () contribute the increase of mobility. It is also shown that the decrease of the is due to the decrease of the mean free path (). On the other hand, the mobility improvement of PMOS with compressive stress is analyzed to be only due to the so increased because the back scattering ratio is increased by the compressive stress. Therefore it was confirmed that the device performance has a strong dependency on the channel back scattering of the inversion layer and thermal injection velocity at the source side and NMOS and PMOS have different dependency on them.