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Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) have been produced by several vendors for commercial applications. SiC-MOSFET reliability was assessed using bias-temperature instability (BTI) and time-dependent dielectric breakdown (TDDB) characteristics. Here, we compared two planar SiC-MOSFET samples (A and B) from different vendors. The samples exhibited significantly different positive and negative BTI, time-dependent gate-current, TDDB lifetime statistics, and temperature dependence. These differences suggest NO (nitric oxide)-annealing variations.

Positive bias temperature instability (PBTI) is one of the crucial issues in SiC-MOSFETs’ introduction to automotive applications. We have investigated PBTI of commercially available SiC-MOSFETs under gate-switching operation to consider real power circuits operation. The use of negative gate off-voltage (Vgs(OFF)~-5 V) is shown to suppress Vth shift (ΔVth) under 100 kHz gate-switching operation. This gate voltage corresponds to the flat band condition, under which the electrons trapped by the near-interfacial traps are effectively detrapped through the interface states around the conduction band edge.

By using a nitric oxide (NO) selective electrode system,N0 produced during the oxidation of human hemoglobin by nitrite was monitored. When 160 μm oxyhemoglobin (in heme) was reacted with 500 μm nitrite, NO was generated quickly at the initial lag phase of the oxidation of oxyhemoglobin by nitrite and decreased gradually during the second burst phase of the reaction, while the oxidation of oxyhemoglobin by nitrite proceeded in a sig-moidal manner including the initial lag phase and second burst phase. The maximal amount of NO produced under this conidition was estimated to be 48 μm . According to the increase of nitrite concentrations added, the amounts of NO produced at the initial phase increased, being in good accordance with the increased rate of the oxidation of oxyhemoglobin. These results strongly suggest the critical role of NO in the oxidation mechanism of oxyhemoglobin by nitrite.

We have performed a detailed analysis of crystal defects in high-performance p-channel metal--oxide--semiconductor field-effect transistors (pMOSFETs) with embedded SiGe source/drain (S/D), using low-angle annular dark field (ADF) scanning transmission electron microscopy (STEM) and electron tomography. We achieved successful results in three-dimensional visualization of crystal defects for the first time. Consequently, we have discussed about the three-dimensional physical geometric relationship between crystal defects and device architecture. This approach is sure to contribute to the development of advanced complementary metal--oxide--semiconductor (CMOS) devices using strained silicon technology.

SiC-MOSFETs have been markedly developed, and the main issues remaining are high-temperature stability and gate-oxide integrity. In this paper, we report special features of I ds-V gs and I g-V gs characteristics of commercially available SiC-MOSFETs during high-gate-voltage and high-temperature stress. Moreover, we introduce simple analytical models that reveal the effects of the trapped charges on the characteristics. Interface states around the conduction-band edge are suggested to be the key mechanisms of Fowler-Nordheim stress degradation (FN degradation) as well as negative bias temperature instability (NBTI), which affects both mobility and carrier density. Hole trapping is also important in FN degradation as well as NBTI. Near-interfacial electron trapping and detrapping found in positive bias temperature instability (PBTI) is also observed in FN degradation. A continuous I g increase during FN stress, which is the most specific to SiC-MOSFETs, is related to the observation that near-interfacial electron trapping has little effect on FN tunneling.

The feasibility of applying binary optical elements (BOEs) to stepper projection optics has been investigated. To obtain a large-scale element with high precision, a novel pattern stitching technique is introduced into fabrication processes which use a stepper for pattern exposures. The influence of mask alignment errors is theoretically studied to confirm that BOEs fabricated with current lithographic tools show sufficiently high performance to be used as stepper lens elements. The influence of uneven transmittance through BOEs and the behavior of spurious order diffraction beams are also examined to estimate the imaging performance degradation caused by inserting such an element into a projection lens. Then, we fabricate a BOE with an effective diameter of 120 mm, and build a projection lens which has a numerical aperture of 0.475 and operates with an exposure wavelength of 248.2 nm. As a result, a pattern size of 0.22 µm is successfully delineated with an 0.8 µm depth of focus, which is comparative to the performance of all-refractive lenses with the same specifications.

In-depth observation of a Si1-xGexheterostructure grown by the molecular beam epitaxy (MBE) method was carried out using electron-excited soft X-ray emission spectroscopy (SXES) nondestructively. Si-L2,3emission band spectra showed a clear modification between those for Si1-xGexalloys and the one for single-crystal Si. The difference in the spectral shape was utilized for the nondestructive study of a Si-Ge heterocontact system in combination with the energy dependence of the X-ray production depth of an energetic electron in a solid.

New heterostructures of modulation-doped p-Si0.5Ge0.5/Ge/Si1-XsGeXsare fabricated using molecular beam epitaxy. The strain in the Ge channel layer can be precisely controlled by changing the composition of the Si1-XsGeXsbuffer layer. As a result, a large energy discontinuity (0.22 eV) in the valence band is realized. This leads to the realization of a high hole mobility (4500 cm2/V ·s) at 77 K.

Ultra-shallow and abrupt boron (B) profiles in Si are achieved by molecular beam epitaxy, and the thermal stability of these profiles is closely examined. Oxidation-enhanced diffusion of a B-?-doped Si layer is observed at 700-850° C. However, broadening of the ?-doped layer during gate oxidation can be minimized by wet O2oxidation owing to the shorter oxidation time than that of dry O2. The sheet resistance of heavily ?-doped layers with ultra-shallow junctions is 1 k? /sq which is almost constant even after thermal annealing. This value is about 1/10 of the reported value obtained by solid-phase diffusion from boron-silicated glass film, in which solid solubility limits the maximum carrier concentration.

The influence of strain on the electrical properties of the Ge channel in a modulation-doped p-Si0.5Ge0.5/Ge/Si1-xGexheterostructure is studied in relation to the Si mole fraction (1-x) and the thickness of the Si1-xGexbuffer layer. In the range of 1-x?0.25, the hole concentration and mobility increase with strain in the Ge channel. However, in the range of 1-x>0.25, they decrease with strain due to the large number of threading dislocations. It is also found that hole concentration and mobility increase with buffer layer thickness. As a result, a very high mobility of 7600 cm2·V-1·s-1at 77 K is obtained at a Si mole fraction of 0.25 and buffer layer thickness of 1 µm.