Compared with conventional DGA (dissolved gas analysis) method for on-line monitoring of power transformers, FBG (fiber Bragg grating) hydrogen sensor represents marked advantages over immunity to electromagnetic field, time-saving, and convenience to defect location. Thus, a novel FBG hydrogen sensor based on Pd/Ag (Palladium/Silver) along with polyimide composite film to measure dissolved hydrogen concentration in large power transformers is proposed in this article. With the help of Pd/Ag composite coating, the enhanced performance on mechanical strength and sensitivity is demonstrated, moreover, the response time and sensitivity influenced by oil temperature are solved by correction lines. Sensitivity measurement and temperature calibration of the specific hydrogen sensor have been done respectively in the lab. And experiment results show a high sensitivity of 0.055 pm/(μl/l) with instant response time about 0.4 h under the typical operating temperature of power transformers, which proves a potential utilization inside power transformers to monitor the health status by detecting the dissolved hydrogen concentration.

We have fabricated very thin TiO 2 film (T eq ∼20Å) by RTP oxidation of sputtered Ti in NO ambient on nitrogen passivated Si substrates. The leakage current is about two orders magnitude lower than SiO 2 of identical T eq . Results show that NO passivation layer prior to sputtering is critical in reducing the leakage current. XPS results show that the temperature RTP NO oxidation of sputtered Ti is very important for achieving high quality TiO 2 films. high oxidation temperature an SiO 2 layer is formed at the interface between TiO 2 and Si and the leakage current is approaching to that of SiO 2 .

A design-of-experiments methodology was implemented to assess the commercial equipment viability to fabricate the high-K dielectrics Ta 2 O 5 , TiO 2 and BST (70/30 and 50/50 compositions) for use as gate dielectrics. The high-K dielectrics were annealed in 100% or 10% O 2 for different times and temperatures in conjunction with a previously prepared NH 3 nitrided or 14 N implanted silicon surface. Five metal electrode configurations—Ta, TaN, W, WN and TiN—were concurrently examined. Three additional silicon surface configurations were explored in conjunction with a more in-depth set of time and temperature anneals for Ta 2 O 5 . Electrical characterization of capacitors fabricated with the above high-K gate dielectrics, as well as SIMS and TEM analysis, indicate that the post high-K deposition annealing temperature was the most significant variable impacting the leakage current density, although there was minimal influence on the capacitance. Further studies are required, however, to clarify the physical mechanisms underlying the electrical data presented.

Electrical performance of in-situ steam generated (ISSG) oxide nitrided using remote plasma nitridation (RPN) has been evaluated. An equivalent oxide thickness (EOT) of 1.6 nm with gate leakage current around 5×10−3 A/cm2 (at −1.5V) has been achieved. The leakage current of remote plasma nitrided ISSG oxide is lower than that of ISSG only, where more than one order of magnitude leakage current reduction (at the same EOT) has been achieved for some RPN conditions. Moreover, it is observed that the extent to which the RPN process conditions modify device parameters such as EOT, flatband voltage (VFB), and time-to-breakdown (tbd) increases with decreasing ISSG thickness. The thinner ISSG oxides appear to be more susceptible to plasma damage and accumulation of positively charged nitrogen atoms at the oxide/Si interface. Therefore, RPN processes that use lower temperature and shorter time are preferred for very thin oxides. The nitrogen content and profile in the samples evaluated using SIMS analysis, indicate that RPN offers higher nitrogen content and better nitrogen profile compared to conventional nitrogen incorporation methods such as NO annealing [1].

Large leakage-current reduction of ultrathin SiO(2) due to enhanced phonon-energy coupling has generated extensive interest, and also doubts about its authenticity. It was suggested by researchers in the industry that both current-voltage (I-V) and capacitance-voltage (C-V) curves of the same devices fabricated using a lithographic method can prove its validation. We developed a bilayer resist lithographic method to fabricate Ni-gate metal-oxide-semiconductor capacitors to validate this effect. Experimental I-V and C-V curves, together with C-V curves simulated using the Berkeley Quantum simulator, demonstrate that large leakage-current reduction (similar to 300x) can be reliably and reproducibly achieved on industrial SiON wafers after proper rapid thermal processing. (C) 2008 The Electrochemical Society.

Good accuracy in depth profile analyses of nitrogen in ultrathin oxynitride films is desirable for process development and routine process monitoring. Low energy SIMS is one of the techniques that has found success in the accurate characterization of thin oxynitride films. This work investigated the artifacts in a typical depth profile analysis of nitrogen with the current SIMS technique and the ways to improve the accuracy by selecting optimal analytical conditions. It was demonstrated that surface roughness developed rapidly in a SiO 2 /Si stack when it was bombarded with an O 2 + beam at 250 eV and angle of incidence from 70 to 79° . The roughness caused distortion in the measured depth profiles of nitrogen and the major component elements. However, the above roughness and the distortion in the depth profiles can be eliminated by using a 250 eV O 2 + beam at an angle of incidence above 80° . Depth profile analyses with a 250 eV 83° O 2 + beam exhibited minimal surface roughening and insignificant variation in the secondary ion yield of SiN − from SiO 2 bulk to the SiO 2 /Si interface, facilitating an accurate analysis of nitrogen distribution in a SiO 2 /Si stack. In addition, depth profiles of the major component elements such as 18 O − and 28 Si − delivered clear information on the location of the SiO 2 /Si interface. Using the new approach, we compared nitrogen distribution in thin SiNO films with the decoupled‐plasma nitridation (DPN) at various powers. Copyright © 2008 John Wiley & Sons, Ltd.

A generalized reliability model of BTI is presented where it is shown that gate stacks with similar interfacial layer lie on the same NBTI vs. E-field universal curve and those with similar bulk layer lie on the same PBTI vs. E-field universal curve. From these universal curves, an optimal gate stack can be derived for which NBTI=PBTI

This work investigated optimal conditions for SIMS analyses of HfO2/Si and TiN/HfO2 interfaces as well as nitrogen distributions in HfO2 films. It was demonstrated that SIMS profiling from the back side of wafers was desirable to eliminate artificial tails of Hf+ and Ti+ as often observed during profiling from the front side. The data suggested good thermal stability of the interfaces in this study. Meanwhile, accurate characterization of shallow nitrogen in HfO2 was achieved by using a low energy O2+ beam at oblique incidence and detecting 30NO− secondary ions. It was revealed that nitrogen was mainly incorporated into the top part of the HfO2 films through plasma nitridation and could be released rapidly during post nitridation anneal at a high temperature.

The mechanism for decoupled plasma nitridation of silicon dioxide thin films is investigated using experimental measurements of nitrogen depth profile and integrated plasma equipment–surface physics modeling. Results show that neutral N atoms and N2+ ions are the primary agents responsible for dielectric film nitridation. N atoms adsorb at the dielectric surface and diffuse into the bulk film. N2+ ions are deposited in an ion-implantation like manner and broaden the nitrogen profile considerably. The surface nitrogen concentration can be enhanced by increasing the plasma source power. Nitrogen diffusion coefficient in the dielectric film decreases with increasing film thickness.