Abstract:Fourier transform infrared (FT-IR) spectra were measured for thermal oxides with different electrical properties grown on 4H-SiC substrates. The peak frequency of the transverse optical (TO) phonon mode was blue-shifted by 5 cm as the oxide-layer thickness decreased to 3 nm. The blue shift of the TO mode indicates interfacial compressive stress in the oxide. Comparison of data for the oxide on a SiC substrate with that for similar oxides on a Si substrate implies that the peak shift of the TO mode at the SiO/S… Show more
“…Hirai and Kita 25 measured FT-IR spectra for thermal oxides on 4H-SiC (0001) Si and C faces and reported that the peak frequency of TO phonons remains nearly constant for thicker oxides (5–30 nm thick); this result is only slightly different from that reported by the authors, which agrees well with that reported by Seki et al. 26 In an extant study, 6 using a two-plate model comprising a thin SiO 2 layer on a 4H-SiC epitaxial layer, the authors suggested that the observed blueshift could be ascribed to a compressive stress of approximately 0.44 GPa induced across the SiO 2 –SiC interface. Figure 6.Change in TO-phonon frequency for samples 1 and 2 as a function of oxide-layer thickness.…”
Section: Resultssupporting
confidence: 87%
“…Based on stress characterization of SiC MOSFETs by Raman spectroscopy, 5 it can be concluded that the observed blueshift is a result of the compressive stress induced across the SiO 2 -4H-SiC interface owing to differences in thermal expansion and elastic moduli of SiO 2 and the SiC substrate. Hirai and Kita 25 measured FT-IR spectra for thermal oxides on 4H-SiC (0001) Si and C faces and reported that the peak frequency of TO phonons remains nearly constant for thicker oxides (5-30 nm thick); this result is only slightly different from that reported by the authors, which agrees well with that reported by Seki et al 26 In an extant study, 6 using a two-plate model comprising a thin SiO 2 layer on a 4H-SiC epitaxial layer, the authors suggested that the observed blueshift could be ascribed to a compressive stress of approximately 0.44 GPa induced across the SiO 2 -SiC interface.…”
Section: Resultssupporting
confidence: 72%
“…A large redshift of the TO phonon in FT-IR spectra can be observed near the SiO 2 –Si interface. 26, 27…”
Section: Resultsmentioning
confidence: 99%
“…A large redshift of the TO phonon in FT-IR spectra can be observed near the SiO 2 -Si interface. 26,27 (4) From an equilibrium standpoint between compressive and tensile stresses, a relatively small tensile stress of the order of 50 MPa (obtained using SNORM) was observed at a position located within the SiC epitaxial layer nearly 250 nm away from the interface between SiO 2 and epitaxial SiC layer.…”
Stresses induced in the silicon carbide (SiC) epitaxial layer near the interface between thermal silicon oxide and 4H-SiC epitaxial substrate were measured using a near-field optical Raman microscope equipped with a hollow pyramid probe (aperture size: approximately 250 nm). The E2 phonon was observed to undergo a 0.17 cm−1 redshift owing to reduction in oxide-layer thickness from 300 nm to 0 nm; this result was compared against that obtained using a standard Raman microprobe sans the pyramidal probe. The result indicates that the epitaxial layer near the SiO2–4H-SiC interface was maintained under a constant tensile stress of the order of 50 MPa. This agrees well with the result obtained using the finite element method (FEM). Based on results obtained using the said Raman microprobe and Fourier transform infrared (FT-IR) measurements, use of an inhomogeneity formation model at the SiO2–4H-SiC interface has been proposed in this study.
“…Hirai and Kita 25 measured FT-IR spectra for thermal oxides on 4H-SiC (0001) Si and C faces and reported that the peak frequency of TO phonons remains nearly constant for thicker oxides (5–30 nm thick); this result is only slightly different from that reported by the authors, which agrees well with that reported by Seki et al. 26 In an extant study, 6 using a two-plate model comprising a thin SiO 2 layer on a 4H-SiC epitaxial layer, the authors suggested that the observed blueshift could be ascribed to a compressive stress of approximately 0.44 GPa induced across the SiO 2 –SiC interface. Figure 6.Change in TO-phonon frequency for samples 1 and 2 as a function of oxide-layer thickness.…”
Section: Resultssupporting
confidence: 87%
“…Based on stress characterization of SiC MOSFETs by Raman spectroscopy, 5 it can be concluded that the observed blueshift is a result of the compressive stress induced across the SiO 2 -4H-SiC interface owing to differences in thermal expansion and elastic moduli of SiO 2 and the SiC substrate. Hirai and Kita 25 measured FT-IR spectra for thermal oxides on 4H-SiC (0001) Si and C faces and reported that the peak frequency of TO phonons remains nearly constant for thicker oxides (5-30 nm thick); this result is only slightly different from that reported by the authors, which agrees well with that reported by Seki et al 26 In an extant study, 6 using a two-plate model comprising a thin SiO 2 layer on a 4H-SiC epitaxial layer, the authors suggested that the observed blueshift could be ascribed to a compressive stress of approximately 0.44 GPa induced across the SiO 2 -SiC interface.…”
Section: Resultssupporting
confidence: 72%
“…A large redshift of the TO phonon in FT-IR spectra can be observed near the SiO 2 –Si interface. 26, 27…”
Section: Resultsmentioning
confidence: 99%
“…A large redshift of the TO phonon in FT-IR spectra can be observed near the SiO 2 -Si interface. 26,27 (4) From an equilibrium standpoint between compressive and tensile stresses, a relatively small tensile stress of the order of 50 MPa (obtained using SNORM) was observed at a position located within the SiC epitaxial layer nearly 250 nm away from the interface between SiO 2 and epitaxial SiC layer.…”
Stresses induced in the silicon carbide (SiC) epitaxial layer near the interface between thermal silicon oxide and 4H-SiC epitaxial substrate were measured using a near-field optical Raman microscope equipped with a hollow pyramid probe (aperture size: approximately 250 nm). The E2 phonon was observed to undergo a 0.17 cm−1 redshift owing to reduction in oxide-layer thickness from 300 nm to 0 nm; this result was compared against that obtained using a standard Raman microprobe sans the pyramidal probe. The result indicates that the epitaxial layer near the SiO2–4H-SiC interface was maintained under a constant tensile stress of the order of 50 MPa. This agrees well with the result obtained using the finite element method (FEM). Based on results obtained using the said Raman microprobe and Fourier transform infrared (FT-IR) measurements, use of an inhomogeneity formation model at the SiO2–4H-SiC interface has been proposed in this study.
“…The cause of the issue of a low channel mobility can be attributed to the formation of the thin carbon layer, presence of dangling bonds, and interface roughness. Under such circumstances, various kinds of studies on the relation between the device performance and physical properties have been conducted, and the development of analytical techniques has also been considered to be of importance.…”
To examine precise depth profiles at the interface of SiO2/SiC, a high resolution that can detect slight discrepancies in the distribution is needed. In this study, an experimental method to achieve a high resolution of less than 1 nm was developed by using dual‐beam time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS). The analysis was preceded by the following three steps: (1) determination of the optimal analytical conditions of the analysis beam (Bi+) and sputtering beam (Cs+), (2) verification of the etching methods to thin the SiO2 layer, and (3) confirmation of the benefits of the low‐energy sputtering beam directed toward SiO2/SiC samples. By using the secondary ion intensity peak‐to‐valley ratio of BN− and BO− of a sample with delta‐doped boron multilayers, the appropriate Bi+/Cs+ condition for a high depth resolution was determined for each energy level of the sputtering beam. Upon verification of the etching methods to thin the SiO2 layer, slight discrepancies were found between samples that were obtained with different etching methods. The difference in the roughness values of the etched surfaces was proactively utilized for the performance confirmation of the low‐energy sputtering beam by means of precise observation of the profiles at the SiO2/SiC interface. The use of a Cs beam with a low energy between 0.25 and 0.5 keV enabled the detection of slight discrepancies in the roughness of less than 1 nm between samples. The aforementioned method has the potential to accurately detect discrepancies in the intrinsic distribution at the SiO2/SiC interface among samples.
Vibrational spectroscopy is used to study a very wide range of sample types, from organic materials to inorganic materials, and can be carried out from a simple identification test to an in‐depth, full‐spectrum, qualitative, and quantitative analysis. Samples are examined either in bulk or in microscopic amounts over a wide range of temperatures and physical states such as gases, liquids, latexes, powders, films, fibers, and organic tissues. Vibrational spectroscopy has many applications, for example characterization of orientation, crystallinity, or chemical bonding structure of a molecule, and provides solution to a host of important and challenging analytical problems. Especially, infrared (IR) and Raman spectroscopy are complementary techniques, and both techniques are usually required to completely measure the vibrational modes of a molecule, a solid or in a solution. Although some vibrational modes may be active in both IR and Raman, both spectroscopies arise from different mechanisms and different selection rules. Generally, IR spectroscopy is the most effective at asymmetric vibrations of polar groups, whereas Raman spectroscopy is the most effective at symmetric vibrations of nonpolar groups. In this article, some applications for semiconductors, using IR and Raman spectroscopy, are introduced.
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