Search

Channel strain analysis in damascene-gate p-metal-oxide-semiconductor field effect transistors (pMOSFETs) with a compressive stress liner and embedded SiGe after the dummy gate removal was studied using micro-Raman spectroscopy with a UV laser (λ=363.8 nm) and a quasiline excitation source. Using a quasiline excitation source, we obtained spatial and energy information simultaneously with a high spatial resolution in the one-dimensional strain profile. For Lgate>210 nm samples, we performed laser exposure for 10 min to measure the channel strain. However, the channel strain for Lgate<210 nm samples was impossible to evaluate due to the limitation of the spatial resolution. Therefore, we increased the laser exposure time to 40 min for Lgate<210 nm samples. Super invar metal with an extremely low thermal coefficient was installed in the monochromator, which achieved a very long measurement. Finally, we found an extremely large stress of -2.4 GPa in the channel of Lgate=30 nm samples. These results demonstrated good agreement with a stress simulation. We found that the large stress in the channel significantly enhanced the drivability in the damascene-gate pMOSFET. [ABSTRACT FROM AUTHOR]

An experimental study of mobility and velocity enhancement effects is reported for highly strained short-channel p-channel field-effect transistors (pFETs) using a damascene-gate process on Si (100) and (110) substrates. The relationship between the mobility and the saturation velocity of hole under a compressive stress over -2.0 GPa is discussed. The local channel stress of -2.4 GPa is successfully measured with ultraviolet- Raman spectroscopy for the 30-nm-gate-length device with top-cut compressive-stress SiN liner and embedded SiGe. Mobility and saturation-velocity enhancements of (100) substrate are larger than those of (110) under the high channel stress. In consequence, the saturation current on (100) is larger than that on (110) for the pFETs with higher channel stress and shorter gate length. Moreover, the large enhancement rate of saturation velocity to mobility by the uniaxial stress suggests high injection velocity for the pFETs with the stressors since the high channel stress is induced near the potential peak of the source by using the damascene-gate technology. [ABSTRACT FROM AUTHOR]

A damascene-gate process enhances the drivability in the shorter gate length region, as compared to a conventional gate-first process for pFETs with compressive stress SiN liners and embedded source/drain SiGe. The origin of the gate length effect for damascene-gate pFETs is studied by using UV-Raman spectroscopy and stress simulation. Moreover, the relationship between channel strain and channel width is analyzed, and the enhancement effect of the drivability on channel width is demonstrated. It is found that channel strain is considerably enhanced with the narrower channel width and shorter gate length by the process combination of the damascene gate and stress enhancement techniques. Owing to the enhancement effects of both channel width and gate length, a high drive current of 1090 µA/µm at Vds = Vgs = --1.0 V and Ioff = 100 nA/µm is achieved for the damascene-gate pFET with 0.3-µm channel width and 40-nm gate length. [ABSTRACT FROM AUTHOR]

We evaluated the stress in a thin strained-Si film on relaxed SiGe on a surface-oxidized Si substrate using surface enhanced Raman scattering (SERS). The strained-Si peak was enhanced by the SERS technique. However, the strained-Si peak shifted toward a higher wavenumber while the peaks from the Si substrate were unchanged. We performed Raman measurement under the optical geometry in LO and TO phonon active conditions. From these measurements, it was clarified that the peak shift was attributed to the TO phonon peak that appeared, which was caused by the excitation of the z polar component in the near-field light. [ABSTRACT FROM AUTHOR]

Raman spectroscopy is a practical evaluation technique for the quantum effect of phonons in a microcrystalline structure. It is very sensitive to fluctuations of crystalline potential or localized atomic geometry. Phonon confinement is observed as a broadening and desymmetrization of the Raman spectrum. However, Raman spectra also include information on crystal quality, strain, and thermal influence caused by the excitation source. Because these factors have an effect similar to that of phonon confinement on spectra, distinction of the factors is essential for accurate evaluation of the phonon confinement effect. The influence of these effects in the utrathin-film silicon-on-insulator (SOI) was investigated by Raman spectroscopy. Marked broadening and desymmetrization of Raman spectra were confirmed for the SOIs with thickness less than 5 nm. The crystalline quality and strain in the SOI layer were investigated by X-ray diffraction. We developed a precise simulation technique for phonon confinement with consideration of thermal and strain effects. By comparing the simulation with the results of Raman spectroscopy, an exact evaluation of phonon confinement effects in utrathin-film SOI was achieved. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We have succeeded in the strain analysis beyond the spatial resolution in conventional Raman measurements, which can be achieved by selecting the strain-induced measurement area by an opaque material. Tungsten (W) film deposited by electron beam (EB)-assisted deposition was used for the opaque material in this study. The EB-W film has the properties of a relatively high absorption coefficient and a low density. These features give rise to shading of the excitation light without stress induction into Si. As a result, the wave number shift of 0.86 cm-1 was obtained in the Si substrate with 100-nm-wide space SiN pattern, whose value was higher than that obtained in conventional Raman measurements, 0.3–0.4 cm-1. Furthermore, the spatial resolution of Raman spectroscopy with the W film deposition was better than that of Raman spectroscopy with an immersion lens. We can say that the methodology is a promising candidate to measure strain in fine structures. [ABSTRACT FROM AUTHOR]

We demonstrate the results of strain (stress) evaluation obtained from electron backscattering pattern (EBSP) measurement for samples of a strained Si-on-insulator (SSOI) and a Si substrate with a patterned SiN film. Two-dimensional stress distributions were obtained in 40×40 µm2 areas of the SSOI. The biaxial stress state was also obtained in the SSOI. Furthermore, clear cross-hatch contrast was observed, especially in the distribution of shear stress Sxy, in contrast to with the other distributions of normal stress Sxx and Syy. One- and two-dimensional stress distributions in the Si substrate with the patterned SiN film were also obtained from EBSP measurement. Moreover, the results were compared with those of UV-Raman measurement and edge force model calculation, and were found to have a good correlation with each other. EBSP measurement was used to measure the complicated biaxial stress including the shear stress in a sample with a 150-nm-wide space pattern. We can conclude that EBSP measurement is a useful method for precisely measuring stress with high spatial resolution. [ABSTRACT FROM AUTHOR]

It is expected to be necessary to measure the stress tensors in Si because the stress field in the channels of metal–oxide–semiconductor field-effect transistors is remarkably complicated. Raman spectroscopy enables us to evaluate the stress precisely, nondestructively, and with relatively high spatial resolution, although its standard implementation fails to resolve the stress tensor. The goal of this study is to establish a procedure for measuring an unknown plane-stress state. In this study, the anisotropic biaxial stress in Si induced by a SiN film was evaluated by Raman spectroscopy with an immersion objective lens with a high numerical aperture. [ABSTRACT FROM AUTHOR]

Hard X-ray photoelectron spectroscopy (HAX-PES) was performed at SPring-8, and has enabled us to study the bulk properties of SiN films deposited by microwave plasma-enhanced chemical vapor deposition and deeply buried SiN/SiO2 interfaces, owing to the large inelastic mean free path of a photoelectron with a high kinetic energy. The defect states in the SiN films were examined by HAX-PES in order to verify the charge-trapping mechanism in a silicon–oxide–nitride–oxide–silicon flash memory device. X-ray reflectometry (XRR) was also performed at SPring-8. There is a complementary relationship between photoelectron spectroscopy and XRR. This methodology is proposed in this paper as a powerful tool for examining material properties. The detailed depth profile analysis of the chemical states in the SiN films obtained by angle-resolved HAX-PES also helped us to examine the charge-trapping mechanism. [ABSTRACT FROM AUTHOR]

Strain induction was studied on a sample that had a dummy gate tetraethyl orthosilicate–silicon dioxide (TEOS–SiO2) and SiN film by UV-Raman spectroscopy with high spatial and high wave-number resolution. The UV laser penetrated through the dummy gate that was transparent to UV light, which enabled us to evaluate strain in the channel of the metal–oxide–semiconductor field-effect transistor (MOSFET) model. Furthermore, we compared stress profiles obtained by finite element (FE) calculations with those obtained by UV-Raman measurements. There was a difference between the stress profiles in the line-and-space pattern sample and in the dummy-gate sample; large compressive (tensile) strains were concentrated at the channel edges in the dummy-gate sample with the compressive (tensile) stress liner, although both tensile and compressive strains existed at the channel edge in the line-and-space pattern sample. The results from UV-Raman spectroscopy were consistent with those obtained by the FE calculation. [ABSTRACT FROM AUTHOR]