Low-frequency (1/f) noise behavior of locally stressed HfO/sub 2//TiN gate-stack pMOSFETs

The low-frequency noise behavior of locally strained pMOSFETs with a 7HfO/sub 2//TiN gate stack is reported. Different ways of compressive-strain engineering have been compared: a Si/sub 3/N/sub 4/ cap layer, SiGe source/drain (S/D) regions, or the combination of both. It is shown that the use of a cap layer does not degrade the 1/f noise magnitude, while an increase of this parameter is found for SiGe S/D devices. This increase is ascribed to the creation of additional traps in the high-k oxide by the SiGe S/D processing. The effect appears to be independent of the germanium content in the range studied (15%-25%). Another conclusion is that no direct correlation has been observed here between the applied stress and the noise magnitude.