Yanling Shi

Notice of Violation of IEEE Publication Principles Ka-band distributed MEMS phase shifters on silicon using AlSi suspended membrane

This paper presents the design, fabrication, and testing of distributed MEMS phase shifters for Ka-band communication systems. The phase shift can be obtained by changing MEMS bridge capacitors located periodically over the transmission line. Simulation results of phase shifters with various structural parameters are analyzed to develop the optimized designs. The phase shifters are fabricated on the high-resistivity silicon substrate, using suspended AlSi bridge membrane. The measured results demonstrate a phase shift of 286° at 36 GHz with the actuation voltage of 25 V, and a return loss better than 10 dB over 0–40 GHz band. In addition, lifetimes of 3 × 106 cycles have been achieved for the fabricated phase shifter with all MEMS bridges held to be valid. It shows that AlSi alloy has a nice compromise between strength and resilience.

Optimization of BSIM3 I-V Model for Double Diffused Drain HV MOSFET

This paper presents a technique for modeling double diffused drain high-voltage MOSFET devices (DDD HV MOSFET). I-V measurements have been made by Agilent ICCAP. Based on the difference between DDD HV MOSFET and normal low voltage MOSFET devices (LV MOSFET), the Rd dependency of Vgs is discussed and equations of Rd and delta (the effective Vds parameter) in the BSIM3v3 model have been optimized. Three parameters are added: Prwg2 which is gate bias quadric coefficient of Rdsw and delta1, delta2 which are gate bias coefficients of delta. The optimization has been made on SPICE BSIM3v3 model using SPICE macro model. The contrast between I-V simulated data of optimized HV MOSFET model and the measured data has been made after parameters extraction. They fit very well

Laser cooling performance of Yb3+-doped LuLiF4 crystal

When pumped with a 10 W 1020 nm fiber laser, a temperature drop of 60.4 K from room temperature of a crystal in the vacuum is observed by utilizing the differential luminescence thermometry measurement method. The crystal is doped with 5wt.%Yb 3+ : LuLiF4 and has a size of 3×3×5 mm3. The cooling power and the cooling efficiency of sample is estimated to be ~50.6 mW and ~2.53%, respectively, at the 232.6 K temperature.

Laser cooling of 5 mol. % Yb3+ : LuLiF4 crystal in air

Abstract. We report the laser cooling performance of 5 mol. % Yb3+:LuLiF4 crystal in air. Both end faces of the crystal with a size of 3×3×5u2009u2009mm3 are cut by Brewster angles. A temperature drop of 11 K (from room temperature) of the sample, pumped by a 3-W/1020-nm CW fiber laser, is observed by a thermal camera. The cooling power and efficiency of the sample are estimated to be ∼14.5u2009u2009mW and ∼1.9%, respectively. Our experiment results show the prospect of this crystal with laser cooling and its potential applications in earth-based optical refrigeration devices.

Forward to cryogenic temperature: laser cooling of Yb: LuLiF crystal

The high quality Yb-doped fluoride crystals have broad prospects for optical refrigeration. We have laser cooled the Yb:LuLiF crystal to a temperature below the limit of current thermoelectric coolers (~180 K). The 5% Yb:LuLiF crystal sample has a geometry of 2 mm×2 mm×5 mm and was supported by two fibers of 200 μm in diameter. They were placed in a ~2×10-4 Pa vacuum chamber with an environment temperature of ~294.5 K. The 1019 nm CW laser of power 38.7 W was adopted to irradiate the sample. The temperature of the sample was measured utilizing the DLT methods. After 20 minutes of laser irradiation, the 5% Yb:LuLiF crystal sample was cooled down to ~182.4 K. By further optimizing experimental conditions and increasing the doped Yb concentration, the Yb:LuLiF crystal might be optically cooled below the cryogenic temperature of 123K in the near future.

A novel structure of non-planar RF spiral inductor based on silicon

In this paper, a novel structure of non-planar inductor based on silicon is presented. The simulation plot of the magnetic distribution reveals that magnetic field reaches its maximum intensity near the inner turns of planar inductor, so it is necessary to deal with the peak value of the magnetic field in the centre of the inductor which causes great substrate loss. An extra layer of silicon dioxide under central several turns of the inductor is proposed in this novel design, and then the inductor becomes non-planar. The simulation results show this method can increase the peak Q factor by nearly 10%

Numerical analysis of pull-in voltage in contact MEMS switch with double actuated electrodes

This paper presents the numerical analysis of pull-in voltage for a contact MEMS switch with a couple of electrodes. The lumped-model for double actuated coupled parallel-plate actuators is applied to describe the pull-in phenomenon. And based on the pull-in analysis results, some optimizing approaches are developed to lower the pull-in voltage for a contact MEMS switch.

Improved microwave performance on low-resistivity Si substrates by introducing an oxidized porous Si interlayer

We propose the use of oxidized porous silicon as a low-loss substrate for the microwave devices. The oxidization of porous silicon is expected to increase the resistivity of Si surface layer and to reduce its effective dielectric loss, which would leads to a significant reduction of the nature loss of low-resisitivity (low-R) Si substrates under the microwave operation. In the present study, a significant improved microwave performance on low-R Si substrates has been demonstrated by measuring the microwave characteristics of coplanar waveguides fabricated on the Si substrates with thick oxidized porous surface layers.

Design and fabrication of micromachined microwave transmission lines

Microwave transmission lines have been designed and fabricated by the CMOS technology on Si substrates with low and high resistivities. First, We analyzed the characteristic impedance of the microwave coplanar waveguides (CPW) with a new similarity method in FEM, which is especially useful for research of the problems about the nonuniform and irregular region, such as the case of micromachined microwave coplanar waveguide. By using this method, we calculated the characteristic impedance of MEMS waveguide and analyzed the change with its different dimensions. Then the samples with characteristic impedances of 120(Omega) and 50(Omega) were fabricated through the surface micromachining and bulk micromachining. Measurements have been performed at frequencies from 1 to 40GHz. The insert loss of transmission-line showed great improvement after the structures were suspended. At 30GHz, the insert loss was about 7dB/cm, reduced by more than 10dB/cm compared with without suspended. To compare with the transmission lines on the low-resistivity silicon (low-R Si), we also fabricated the transmission lines directly on the high-resistivity Si substrate (high-R Si), the insert loss was only 1-4dB/cm at the frequencies from 1 to 40GHz.

Stress relaxation of the micromachined coplanar waveguide

Micromachined microwave coplanar waveguides were fabricated in standard CMOS technology and the hybrid etch technology. The coplanar waveguides have been suspend from the silicon substrate and third insertion loss was greatly improved. When fabricating the micromachined structures on a (100) wafer, stress was relaxed because of the different thermal expansion coefficients between silicon and SiO2 dielectric. This caused this structures deformed. Among all etching pattern we had adopted, the etching orientation along the (100) line of the wafer obtained the smaller stress relaxation, but costing the longest etching time. ON the other hand, the space between the open areas for etching needs to be designed carefully to obtain the best mechanical and electrical properties.