Asymmetric X-junction thermooptic switches based on fluorinatedpolymer waveguides

Thermooptic 2×2 switches based on low-loss fluorinated polymer waveguides have been demonstrated. For the waveguide possessing a low-loss around the 1.55-μm wavelength, crosslinkable fluorinated poly(arylene ethers) (FPAE) is developed as a core material and perfluorocyclobutane (PFCB) is used as a cladding material. To enhance the fabrication tolerance and to achieve a low switching power, asymmetric X-junctions with a Mach-Zehnder interferometer are exploited for the polymeric waveguide switches. An inverted rib waveguide structure is fabricated by filling up the etched groove on a lower cladding with the core polymer. The switch exhibits a crosstalk of less than -20 dB, a switching power of 10 mW, and an insertion loss of 4.5 dB     

A comparison of two micromachined inductors (bar- and meander-type)for fully integrated boost DC/DC power converters

Two micromachined integrated inductors (bar- and meander-type) are realized on a silicon wafer by using modified, IC-compatible, multilevel metallization techniques. Efforts are made to minimize both the coil resistance and the magnetic reluctance by using thick electroplated conductors, cores, and vias. In the bar-type inductor, a 25-μm thick nickel-iron permalloy magnetic core bar is wrapped with 30-μm thick multilevel copper conductor lines. For an inductor size of 4 mm×1.0 mm×110 μm thickness having 33 turns of multilevel coils, the achieved specific inductance is approximately 30 nH/mm² at 1 MHz. In the meander-type inductor, the roles of conductor wire and magnetic core are switched, i.e., a magnetic core is wrapped around a conductor wire. This inductor size is 4 mm×1.0 mm×130 μm and consists of 30 turns of a 35-μm thick nickel-iron permalloy magnetic core around a 10-μm thick sputtered aluminum conductor lines. A specific inductance of 35 nH/mm² is achieved at a frequency of 1 MHz. Using these two inductors, switched DC/DC boost converters are demonstrated in a hybrid fashion. The obtained maximum output voltage is approximately double an input voltage of 3 V at switching frequencies of 300 kHz and a duty cycle of 50% for both inductors, demonstrating the usefulness of these integrated planar inductors     

Thermally robust Ta2O5 capacitor for the256-Mbit DRAM

The thermal degradation of the Ta₂ O₅ capacitor during BPSG reflow has been studied. The cause of deterioration of Ta₂O₅ with the TiN top electrode was found to be the oxidation of TiN. By placing a poly-Si layer between TiN and BPSG to suppress oxidation, the low leakage current level was maintained after BPSG reflow at 850°C. The Ta₂O₅ capacitor with the TiN/poly-Si top electrode was integrated into 256-Mbit DRAM cells and excellent leakage current characteristics were obtained     

Integrated optical high-voltage sensor based on a polymeric Y-branch digital optical switch

An integrated optical high-voltage sensor is realized by fabricating a Y-branch digital optical switch in an electrooptic polymer. The measurement of ac high voltage is accomplished by using the linear transfer characteristics of the switch at zero bias voltage. Furthermore, the logarithmic ratio between the optical powers of two output ports may be used to remove the noise caused by the power fluctuations of a light source. The polymeric high-voltage sensor requires no electrical dc biases and no voltage dividers. It is also wavelength insensitive and fabrication-tolerant due to its use of mode evolution effects instead of interference. The measured sensing voltage range is as large as ac 500-V peak-to-peak.     

A novel phase noise reduction technique in oscillators usingdefected ground structure

A new technique to reduce the phase noise in microwave oscillators is developed using the resonant characteristic of the defected ground structure (DGS). Two kinds of oscillators have been designed and measured for the examination of the reduction of phase noise by the DGS. The first adopts the DGS section under the microstrip line at the gate circuit, while the second has only the conventional microstrip line. Measurement shows reduced phase noise by 10-15 dB in the oscillator with the DGS compared to the conventional one     

A compact-size microstrip spiral resonator and its application to microwave oscillator

This letter presents a compact size microstrip spiral resonator and its application to a low phase noise oscillator. This resonator has stopband characteristics to be used in the series feedback oscillator topology. The whole circuit area of the proposed resonator is within 1/10 wavelength, which results in the reduction of the circuit area and cost. A 10-GHz oscillator incorporated with this resonator was designed, fabricated and measured. It shows low phase noise performance of -95.4-dBc/Hz at 100 kHz offset.     

用于先进PCB制造工艺的叠层封装

在20世纪90年代,球栅阵列封装(BGA)和芯片尺寸封装(CSP)在封装材料和加工工艺方面达到了极限。这2种技术如同20世纪80年代的表面安装器件(SMD)和70年代通孔安装器件(THD)一样,在电学、机械、热性能、尺寸、质量和可靠性方面达到最大值。目前,三维封装正在成为用于未来采用的先进印制板(PCB)制造工艺的下一个阶段。它们可以分为圆片级封装、芯片级封装、和封装面。叠层封装(PoP)是一种封装面叠层封装类型的三维封装技术[15]。     

A 12-b, 10-MHz, 250-mW CMOS A/D converter

A 12-b, 10-MHz, 250-mW, four-stage analog-to-digital converter (ADC) was implemented using a 0.8-μm p-well CMOS technology. The ADC based on a digitally calibrated multiplying digital-to-analog converter (MDAC) selectively employs a binary-weighted capacitor array in the front-end stage and a unit-capacitor array in the remaining back-end stages to obtain 12 b level linearity while maintaining high yield. All the analog and digital circuit functional blocks are fully integrated on a single chip, which occupies a die area of 15 mm² (4.2 mm×3.6 mm). Measured differential nonlinearity (DNL) and integral nonlinearity (INL) of the prototype are less than ±0.8 LSB and ±1.8 LSB, respectively     

Binary blends of nylons with ethylene vinyl alcohol copolymers: Morphological,thermal, rheological,and mechanical behavior

Binary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH-62) and 71 (EVOH-71) mole percent vinyl alcohols, with nylons (nylon-6, nylon-6/12, and nylon-12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH-62/nylon-6 and EVOH-71/nylon-6 blends showed homogeneous phase morphologies in the nylon-6-rich region, and fine phase separations (c.a. 2 × 10^?7 m) in the EVOH-rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH-71/nylon-6/12 and EVOH-71 /nylon-12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanical property drop were also observed.     

Improvement of the cell performance in the ZnS/Cu(In,Ga)Se2 solar cells by the sputter deposition of a bilayer ZnO : Al film

ZnS is a candidate to replace CdS as the buffer layer in Cu(In,Ga)Se₂ (CIGS) solar cells for Cd‐free commercial product. However, the resistance of ZnS is too large, and the photoconductivity is too small. Therefore, the thickness of the ZnS should be as thin as possible. However, a CIGS solar cell with a very thin ZnS buffer layer is vulnerable to the sputtering power of the ZnO : Al window layer deposition because of plasma damage. To improve the efficiency of CIGS solar cells with a chemical‐bath‐deposited ZnS buffer layer, the effect of the plasma damage by the sputter deposition of the ZnO : Al window layer should be understood. We have found that the efficiency of a CIGS solar cell consistently decreases with an increase in the sputtering power for the ZnO : Al window layer deposition onto the ZnS buffer layer because of plasma damage. To protect the ZnS/CIGS interface, a bilayer ZnO : Al film was developed. It consists of a 50‐nm‐thick ZnO : Al plasma protection layer deposited at a sputtering power of 50 W and a 100‐nm‐thick ZnO : Al conducting layer deposited at a sputtering power of 200 W. The introduction of a 50‐nm‐thick ZnO : Al layer deposited at 50 W prevented plasma damage by sputtering, resulting in a high open‐circuit voltage, a large fill factor, and shunt resistance. The ZnS/CIGS solar cell with the bilayer ZnO : Al film yielded a cell efficiency of 14.68%. Therefore, the application of bilayer ZnO : Al film to the window layer is suitable for CIGS solar cells with a ZnS buffer layer. Copyright © 2012 John Wiley & Sons, Ltd.