Wen-Hsi Lee

Effects of Glass Addition on Microwave Dielectric Properties of Zn0.95Mg0.05TiO3 + 0.25TiO2 Ceramics

The effects of Bi2O3 addition on the microwave dielectric properties and the microstructures of Zn0.95Mg0.05TiO3 + 0.25TiO2 with 1 wt% 3ZnO–B2O3 (ZnBO–ZMT) ceramics prepared by conventional solid-state routes have been investigated. In a preliminary study, it was shown that ZnBO–ZMT ceramics can be sintered to a theoretical density higher than 95% at 900°C. In this study, the effects of Bi2O3 additions of up to 10 wt% on the sintering characteristics of the ZnBO–ZMT ceramics was investigated at the sintering temperatures ranging from 860 to 960°C. Sintered ceramic samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). It was found that as the content of Bi2O3 increases, the density of the sintered ceramics increases, and the sintering temperature can be lowered to 880°C by adding 5 wt% Bi2O3. The ZnBO–ZMT ceramic with 5 wt% Bi2O3 addition sintered at 880°C exhibits the optimum dielectric properties: Q×f=4000 GHz, er=24.6, and τf=-14 ppm/°C. Unlike the ZnBO–ZMT ceramic without Bi2O3 addition sintered at above 920°C, the ceramics with Bi2O3 additions show no Zn2TiO4 existence at 960°C sintering. It is therefore demonstrated that the addition of Bi2O3 can suppress the formation of Zn2TiO4 in ZnBO–ZMT ceramics.

Microwave Dielectric Properties of Zn0.95Mg0.05TiO3 + 0.25TiO2 Ceramics with 3ZnO–B2O3 Addition

Boron oxide and zinc oxide (ZnBO) added to dielectric materials have attracted great attention recently because they enable the lowering of the firing temperature. The effects of ZnBO addition up to 2 wt% on the microstructure and microwave dielectric properties of zinc magnesium titanate Zn0.95Mg0.05TiO3 + 0.25TiO2 (ZMT) ceramics were investigated for sintering temperatures ranging from 860° to 940°C. It was found that small amount of added ZnBO (1 wt%) can significantly increase the density and improve the microwave dielectric properties of ZMT ceramics. Doped ZMT ceramics can be sintered to a density higher than 95% of the theoretical density at 900°C. A rutile second phase exists in the ZMT ceramics, and it increases with increasing amount of added ZnBO and sintering temperature. In addition, the Zn2TiO4 spinel phase was observed with a sintering temperature of 920°C. The measured dielectric properties of ZMT ceramics with 1 wt% ZnBO addition sintered at 900°C for 2 h were er=23.6, Q×f=30990 (at 7.75 GHz) and τf=-8 ppm/°C.

Low Temperature Sintering and Microwave Dielectric Properties of Ba2Ti9O20 Ceramics with 3ZnO–B2O3 Addition

Boron and zinc oxide (ZnBO) glass added in dielectric materials have drawn a great attention recently due to the low firing temperature. Microwave dielectric properties of the Ba2Ti9O20-based ceramics with ZnBO addition up to 3 wt% were investigated at the sintering temperatures ranging from 900 to 960°C. Effects of the ZnBO addition on the bulk density, microstructure, and dielectric properties of the Ba2Ti9O20-based ceramics at microwave frequency were elucidated. X-ray diffraction (XRD) results show the presence of five crystalline phases, Ba2Ti9O20, BaZr(BO3)2, BaTi3O7, BaZrO3 and Zn2SiO4 in the sintered ceramics, depending upon the amount of ZnBO addition. Optimum dielectric properties were obtained for the Ba2Ti9O20-based ceramic with 1 wt% ZnBO addition and sintered in air at 940°C for 2 h, having the dielectric properties: Q=1137 (Q×f=8300), er value=27.3, and τf=2.5 ppm/°C.

Bis-(3-sodiumsulfopropyl disulfide) Decomposition with Cathodic Current Flowing in a Copper-Electroplating Bath

The composition of the plating electrolyte is important in a copper (Cu) electroplating process. The consumption rate of bis(3-sodiumsulfopropyl disulfide) (SPS) has a strong correlation with the electroplating current density. The decomposition of SPS is relative to the electroplating charge and to the age of the Cu anode. The cathodic current density improves SPS breakdown, and it increases the generation of by-products resulting from SPS decomposition. The aged bath is examined using potentiodynamic polarization and electrochemical impedance spectroscopy. The aged bath helps increase cupric ion reduction because the concentration of cupric ions increases with time after Cu electroplating. The SPS species reacted with cuprous ions to produce the Cu-accelerator complex, which increased the depolarization effect.

Pulsed Electrodeposition of CuInSe2 Thin Films onto Mo-Glass Substrates

In this study, copper indium selenide (CIS) films were deposited by pulsed electrodeposition with multi potentials to control the atomic ratio of the CIS film and improve the deposition uniformity. It was found that smaller duty cycle and pulsed period enhanced the cathodic current due to ion replenishment. The results show that the Cu/In ratio was significantly influenced by reverse voltage of pulsed electrodeposition. The uniformity of the CIS films can be improved by proper reverse voltage. The deposition rate did not decrease in direct proportion to the duty cycle because the plating current was enhanced by the pulse effect. The pulsed deposited CIS film with optimized composition show smaller grain size, smoother microstructure, and less secondary phase than constant deposited film.

Characteristic of Organic Thin Film Transistor with a High-k Insulator of Nano-TiO2 and Polyimide Blend

The preparation of nanocomposite as gate dielectric film was carried out by blending polyimide and nano-TiO2 particle to enhance the capacitance of gate dielectric. When the concentration of the nano-TiO2 particle was less than 2 vol % and was well dispersed in polyimide slurry, a nanocomposite film with a homogeneous distribution of nano-TiO2 particles in polyimide and low roughness was obtained after curing at 200 °C, resulting in low leakage current density of the nanocomposite film and high on/off ratio of the organic thin film transistor (OTFT) device. A strong correlation between the morphology and electrical properties of the nanocomposite gate dielectric film is reflected in the OTFT device performance. Because capacitance of the gate dielectric film and proportion of thin film phase of the pentacene both increased when the pentacene was deposited on a nanocomposite gate dielectric film, the mobility and the threshold voltage of OTFT noticeably improved.

Galvanic Corrosion Between TaN x Barriers and Copper Seed

In semiconductor metallization processes, the galvanic corrosion of metals should be controlled to improve the process integrity. Refractory metals such as tantalum and tantalum nitride (TaN x ) are widely used as a barrier metal to prevent the copper (Cu) metal from diffusing into the dielectric layers. In this study, the galvanic effect between the Cu seed and the TaN x film, which is deposited with different nitrogen (N 2 ) gas flow rates was investigated using chemical mechanical polishing slurries. It was found that the galvanic corrosion of the TaN x films decreased whereas the galvanic corrosion of the Cu seed increased as the N 2 gas flow rate increased. The whole Cu corrosion rate was higher than that of the TaN x films because the intrinsic corrosion of the Cu seed dominated the overall Cu corrosion rate in the acidic slurry, but for the TaN x films the galvanic corrosion dominated. This study also proposed a model to reveal the galvanic effect between the Cu seed and various TaN x films.

Suppression Effect of Low-Concentration Bis-(3-sodiumsulfopropyl disulfide) on Copper Electroplating

Bis-(3-sodiumsulfopropyl disulfide) (SPS) is a well-known additive that promotes bottom-up filling in the copper (Cu) electroplating process. In the literature, SPS has been widely investigated and has proven to have an acceleration effect on Cu electroplating. However, our results show that low-concentration SPS (∼ 10 ppm) has a suppression effect on the Cu electroplating rate. The suppression behavior of low-concentration SPS is demonstrated using various electrochemical analyses, including the polarization curve, cyclic-voltammetry stripping, and electrochemistry-impedance spectroscopy (EIS). The equivalent circuit simulated from the EIS data shows that the mechanism of low-concentration SPS inhibiting the Cu electroplating rate is caused by an increase in the charge-transfer resistance. This suggests that when SPS concentration is too low, the formation of Cu(I)thiolate complexes is too low to accelerate the Cu electroplating rate while the added SPS still consumes energy from the system. The acceleration effect of SPS concentration on the Cu electroplating rate exists when SPS concentration is larger than ∼ 100 ppm.

Effect of Annealing on the Microstructure and Electrical Property of RuN Thin Films

Ruthenium (Ru) and ruthenium nitride (RuN) thin films have been investigated as candidates for barrier layers in copper (Cu) damascene processes. In order to study the thermal stability of the Ru and RuN films, the as-deposited films were annealed by rapid thermal annealing (RTA), and the film resistance was real-time measured by a four-point probe, which was embedded in the RTA tool. The X-ray diffraction data show that the grain size of Ru decreased with the increase of the nitrogen (N) content. The Ru phases gradually changed to the RuN phases, and the resistivity of the RuN films decreased with annealing time due to nitrogen effusion. Discontinuous RuN films were found when the annealing temperature was higher than 800°C and then caused a poor Cu diffusion barrier property. We also demonstrated that the Cu film could be directly electroplated on the RuN films with adequate adhesion.

Investigation of Galvanic Corrosion Between TaN x Barriers and Copper Seed by Electrochemical Impedance Spectroscopy

In this article, electrochemical impedance spectroscopy is used to characterize the mechanism of galvanic corrosion between copper Cu seeds and tantalum nitride TaNx barriers deposited with different N2 flow rates. By way of software simulating with EIS data, an equivalent circuit is built up to explain the corrosion behavior of the TaNx films’ relation to the Cu seeds in an acidic chemical-mechanical-polishing slurry. The equivalent circuit can respond to changes in resistance and capacitance elements of the Cu‐TaNx electrochemical system. It is found that the charge-transfer resistance of the TaNx galvanic corrosion increases with the N2 flow rate, whereas the resistance of a tantalum-oxide layer is opposite because increasing the N content of the TaNx films inhibits corrosion and oxidation of the Ta metals. The result is consistent with our previous investigation that the galvanic corrosion of the TaNx films to the Cu seeds is retarded by the N element C. C. Hung, Y. S. Wang, W. H. Lee, S. C. Chang, and