Ting- Chang

Prevalence of Human Papillomavirus Genotypes in Northern Taiwanese Women

The prevalence of Human Papillomavirus (HPV) in the general population of northern Taiwan is described. A total of 343 consecutive cervical swabs from women visiting the medical center for routine gynecologic care were included. Cervical cell cytology was examined by the Papanicolaou (Pap) test, and a PCR‐based hybridization gene chip analysis was used to identify HPV genotypes. The HPV prevalence in the overall population was 32.4%. When divided into two groups according to cytology, 20.9% of women with normal cytology were HPV positive while 75.3% of women with abnormal cytology were HPV positive. Among positive samples, 68.5% were single type infections while 31.5% harbored multiple HPV types. A total of 32 types of HPV were identified; the leading five were HPV16 (5.8%), HPV58 (5.3%), HPV53 (4.1%), HPV52 (3.8%), and HPV18 (2.3%). Our results constitute baseline data and may provide important implications for future prophylactic programs. The relatively high prevalence of HPV 58, 53, and 52 among northern Taiwanese women has important implications for vaccine development. J. Med. Virol. 82:1739–1745, 2010.

Effect of Top Electrode Material on Resistive Switching Characteristics in MnO

a. Department of Electronics Engineering & Institute of Electronics, National Chiao Tung University, Hsin-Chu 300, Taiwan, R.O.C. b. Department of Physics and Institute of Electro-Optical Engineering, & Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung, 804, Taiwan, R.O.C. c. Green Energy & Environment Research Labs. , Industrial Technology Research Institute, Hsinchu 310, Taiwan, R.O.C. d. Department of Electrical Engineering & Institute of Electronic Engineering, National Tsing Hua University, Taiwan

The Impact of Active Layer Pre-Treatment on Bias Stress Stability of Sol-gel Derived Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistor

We have investigated the gate bias stress-induced instability on the electrical properties with different pre-treatments for sol-gel derived amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs). The device with illuminating and heating pretreatments under the positive/negative gate bias stress in vacuum had the smallest threshold voltage shift as the stress duration increased, while the device with oxygen gas pre-treatment exhibited an obvious variation. These electrical instabilities were ascribed to the charge trapping in the gate insulator and the oxygen/water adsorption on the active layer. It indicates that the specific pre-treatment for the a-IGZO film can improve the device stability. It also provides the important information for the subsequent passivation process concerning the pre-treatment of the active layer.

先進High-k/Metal Gate之金氧半場效電晶體 電性分析與可靠度研究

Many years of research and development has shown that one valid way to solve problems of gate leakage current is that replacing conventional SiO2 gate dielectric with high-k dielectric, especially with HfO2 gate dielectrics. HfO2 gate dielectrics have been implemented at the 32nm technology node and smaller. Nevertheless, many measurement techniques must be refined, especially charge pumping techniques playing an important role in inspection of defects. Consequently, the first part mainly focuses on abnormal traps measured by the charge pumping technique for 3nm HfO2 dielectric n-MOSFETs in high gate voltage. It can be verified the abnormal traps being high-k bulk shallow traps by fitting the discharge time formula and the related formula between tunneling time and distance. To further investigate the behavior of these additional traps contributing to charge pumping current, devices with different interlayer thicknesses and different N concentrations in the TixN1-x metal gate are compared. These comparisons show that abnormal traps appear only when channel electrons inject to high-k bulk shallow traps. Subsequently, by fitting discharge formula for different tfalling time, results show that electrons escape from high-k bulk shallow traps first to the channel and then to source and drain during tfalling time. This current cannot be measured by the charge pumping technique. Subsequent measurements of NT by charge pumping technique at tbase level reveal a remainder of electrons trapped in high-k bulk shallow traps. Combining with results above, gate current is tunneling-path dominated in low Vg, and Icp detects interface trap (Nit) and “geometrical component” of Icp (Ncp,gc). On the contrary, the gate current is dominated by the Frenkel-Poole mechanism in high Vg, and Icp measures Nit, Ncp,gc, and Nhkst (high-k bulk shallow trap). The second part exhibits the extra amount of NT contributes to charge pumping current in high voltage regime in p-channel MOSFETs. Via distinguish current and current fitting, it is confirmed that initial gate current is Frenkel-Poole mechanism. Via fitting discharge formula with different temperature and related formula between tunneling time and distance, dHfO2,trap can be calculated to be 13.2A ~ 16.2A. This result is versified that extra Icp traps is actually located in the high-k bulk shallow traps in p-channel MOSFETs. The third part shows abnormal negative threshold voltage shifts under positive bias stress in input/output TiN/HfO2 n-MOSFETs using fast I-V measurement. After nine cycles of stress and recovery, Vt almost completely recovers. This result demonstrates that this process is reversible. The fast I-V double sweep measurement with insignificant gate current indicates that electrons escape from high-k bulk traps to the metal gate in Vhigh level, leading to a decrease in Vt. On the contrary, electrons inject from the metal gate to high-k bulk traps in Vbase level, causing an increase in Vt. Through curve fitting, the charge/discharge process is confirmed via the tunneling mechanism due to -1 in value in the slope. In addition, the direction of Vt shift in input/output (I/O) device is contrary to that in the standard performance device since electrons escape from high-k bulk traps to metal gate by the tunneling mechanism in I/O device rather than channel electrons injecting to bulk traps, owing to the large interlayer thickness. According to these results, the charge/discharge effect is reduced with a decrease in pre-existing high-k bulk traps, such as employing Zr doping in HfO2 dielectric device. Finally, an anomalous gate current hump is observed after dynamic negative bias stress (NBS) and negative-bias temperature-instability (NBTI) in HfxZr1-xO2 and HfO2/metal gate p-channel metal-oxide-semiconductor field-effect transistors. This result is attributed to hole trapping in high-k bulk traps. Fitting gate current after dynamic NBS and NBTI indicates that JFrenkel-Poole changes to JTunneling when Vg E sio2, while JTunneling changes to JFrenkel-Poole when Vg > Vt due to the influence of E high-k < E sio2. These phenomena can be attributed to the fact that the electric field must follow the formula E high-k ehigh-k = Q + Esio2e sio2. Subsequently, from Zr-undoped and Zr-doped devices after dynamic NBS, we conclude that the gate current hump requires both sufficient hole trapping and larger initial gate current. Moreover, Zr-doped devices can ameliorate dynamic NBS and NBTI. These results obey the hump generation condition JTunneling << JFrenkel-Poole.

Effects of Post-Deposition Annealing Atmosphere and Duration on Sol-Gel Derived Amorphous Indium-Zinc-Oxide Thin Film Transistors

This work shows the effects of post-deposition annealing atmosphere and duration on the properties of sol-gel derived amorphous indium zinc oxide thin film transistors (a-IZO TFTs). Two different post-deposition annealing atmospheres, nitrogen and oxygen, were used in this study. Experimental results showed that the O2-annealed devices showed better electrical characteristics than the N2-annealed samples. Under O2-annealing, field effect mobility was enhanced to 1.47 cm 2 /V s, the threshold voltage increased to -4.61 V and the subthreshold swing improved to 0.86 V/dec. Also, the transfer characteristics of a-IZO TFTs improve with annealing time. X-ray photoelectron spectroscopy (XPS) analysis indicated that the chemical composition of the IZO film was modified by the oxygen annealing.

Effects of post-treatment for low-dielectric hydrogen silsesquioxane (HSQ)

Low density materials, such as hydrogen silsesquioxane (HSQ), can offer lower dielectric constants. With HSQ, a low value of K can be achieved if the density of Si-H bonding is maintained at a high level. However, the quality of HSQ films are degraded by the damage of oxygen plasma and hygroscopic behavior during photoresist stripping. In addition, the thermal stability of as-cured HSQ films are about 400 degrees Celsius. Both leakage current and dielectric constant of HSQ films rapidly increase with increasing annealing temperature. In this work, we have studied the use of hydrogen plasma to improve the quality of HSQ. The leakage current of HSQ decreases as the H2 plasma treatment time is increased. The role of hydrogen plasma is to passivate the surface of porous HSQ. In addition, the enhancement of the thermal stability of the HSQ film by fluorine ion implantation treatment was investigated. The implantation step can reduce the leakage current of HSQ with high annealing temperature.The enhancement of thermal stability of the HSQ film is due to the film densification by ion implantation treatment.