Channel Strain Measurement in 32-nm-Node Complementary Metal--Oxide--Semiconductor Field-Effect Transistor by Raman Spectroscopy

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We performed a strain analysis of a 32-nm-node microprocessing unit by Raman spectroscopy in conjunction with transmission electron microscopy. The channel surface was exposed by chemical etching and mechanical polishing for Raman spectroscopy. Some defects and Ge concentration variation were observed in embedded SiGe of a p-channel metal--oxide--semiconductor field-effect transistor (pMOSFET). Uniform defects lying at the same angle were observed in the source and drain regions of an n-channel MOSFET (nMOSFET). From the Raman measurement, the Raman peak from strained Si in the pMOSFET shifted toward a higher frequency at approximately 7.5 cm-1, which corresponds to -3.75 GPa (compressive) under the assumption of uniaxial stress along the channel direction. On the other hand, the Raman peak shift from strained Si in the nMOSFET was -1.7 cm-1 corresponding to 0.85 GPa (tensile) under the assumption of uniaxial stress. From the nanobeam diffraction measurements, the compressive strain at the channel edge was larger than that at the channel center in the pMOSFET. On the other hand, the tensile strain in the nMOSFET was induced uniformly in the channel region. We think that understanding and control of channel strain introduction are indispensable in the state-of-the-art complementary MOSFET technology.
2012-04-25