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

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 observ...

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Published inJapanese Journal of Applied Physics Vol. 51; no. 4; pp. 04DA04 - 04DA04-5
Main Authors Takei, Munehisa, Hashiguchi, Hiroki, Yamaguchi, Takuya, Kosemura, Daisuke, Nagata, Kohki, Ogura, Atsushi
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.04.2012
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Summary: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.
Bibliography:TEM images of commercially available 32-nm-gate-length (a) pMOSFETs and (b) nMOSFETs. White circles indicate defects. APM etching rate of (a) TiN and (b) SiO 2 for gate electrode gate and dielectric under Hf-based high-$k$ what, respectively. TEM images of pMOSFET after channel surface exposure by APM etching for Raman measurement. The right figure is a closeup view. EDX images around channel for (a) pMOSFETs and (b) nMOSFETs. (c) Close-up view of Ge in pMOSFET S/D regions. The dashed red line is the boundary of Ge concentration. (1) and (2) areas were high- and low-Ge-concentration areas relative to each other, respectively. Schematic experiment diagram of Raman measurement for fine-MOSFETs. The green circle area indicates the beam spot of the UV laser. Raman spectra obtained from (a) pMOSFET and (b) nMOSFET regions. The blue and red dashed lines are fitting results of the Si-sub and strained-Si components. NBD maps in channel regions of (a, c) pMOSFETs and (b, d) nMOSFETs. (a) and (b) are the lateral strains along the channel direction. (c) and (d) are the vertical strains. The white circle in (a) indicates the channel edge region. The lateral and vertical strains in the pMOSFETs were obtained from the (220) and (002) diffractions, respectively. Those in the nMOSFETs were obtained from the (440) and (006) diffractions, respectively.
ISSN:0021-4922
1347-4065
DOI:10.1143/JJAP.51.04DA04