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A gate-last process for fabricating HfSiON/TaN n-channel metal-oxide-semiconductor-field-effect transistors (NMOSFETs) is presented. In the process, a HfSiON gate dielectric with an equivalent oxide thickness of 10 Å was prepared by a simple physical vapor deposition method. Poly-Si was deposited on the HfSiON gate dielectric as a dummy gate. After the source/drain formation, the poly-Si dummy gate was removed by tetramethylammonium hydroxide (TMAH) wet-etching and replaced by a TaN metal gate. Because the metal gate was formed after the ion-implant doping activation process, the effects of the high temperature process on the metal gate were avoided. The fabricated device exhibits good electrical characteristics, including good driving ability and excellent sub-threshold characteristics. The device's gate length is 73 nm, the driving current is 117 μA/μm under power supply voltages of VGS = VDS = 1.5 V and the off-state current is only 4.4 nA/μm. The lower effective work function of TaN on HfSiON gives the device a suitable threshold voltage (∼ 0.24 V) for high performance NMOSFETs. The device's excellent performance indicates that this novel gate-last process is practical for fabricating high performance MOSFETs. [ABSTRACT FROM AUTHOR]

Chaos game representation (CGR) is proposed as a scale-independent representation for DNA sequences and provides information about the statistical distribution of oligonucleotides in a DNA sequence. CGR images of DNA sequences represent some kinds of fractal patterns, but the common multifractal analysis based on the box counting method cannot deal with CGR images perfectly. Here, the wavelet transform modulus maxima (WTMM) method is applied to the multifractal analysis of CGR images. The results show that the scale-invariance range of CGR edge images can be extended to three orders of magnitude, and complete singularity spectra can be calculated. Spectrum parameters such as the singularity spectrum span are extracted to describe the statistical character of DNA sequences. Compared with the singularity spectrum span, exon sequences with a minimal spectrum span have the most uniform fractal structure. Also, the singularity spectrum parameters are related to oligonucleotide length, sequence component and species, thereby providing a method of studying the length polymorphism of repeat oligonucleotides. [ABSTRACT FROM AUTHOR]

In this paper, we make use of the auxiliary equation and the expanded mapping methods to find the new exact periodic solutions for (2+1)-dimensional dispersive long wave equations in mathematical physics, which are expressed by Jacobi elliptic functions, and obtain some new solitary wave solutions (m - 1). This method can also be used to explore new periodic wave solutions for other nonlinear evolution equations. [ABSTRACT FROM AUTHOR]