Reduction of local mechanical stress in a transistor using Si ₃N₄/SiO_xN_y, contact ESL

We have investigated the influence of a contact etch-stop layer (ESL) on the local mechanical stress in a deep sub-micrometer complementary metal oxide semiconductor (CMOS) field-effect transistor using convergent-beam electron diffraction with nanoscale resolution. By introducing a thin buffer layer of SiO_xN_y underneath the Si₃N₄ contact ESL, we have shown that the compressive channel strain can be effectively mitigated, resulting in higher electron mobility and drive current in n-channel metal oxide semiconductor field-effect transistors, without undue impact on the electrical performance of p-channel transistors. Hence, the Si₃N ₄/SiO_xN_y film stack is a promising alternative for contact ESL to enable high-performance CMOS devices.