A 310/spl deg//3.6-dB K-band phaseshifter using paraelectric BST thin films

Ferro- and para-electric BaSrTiO/sub 3/ (/spl epsiv//sub r//spl sim/350 and tg/spl delta//spl sim/5/spl times/10/sup -2/ at 0V) thin films were deposited by low-cost sol-gel techniques. Subsequently, the films were used for fabricating coplanar waveguide phaseshifters using tunable finger-shaped capacitors. A 310/spl deg/ phaseshift was obtained at 30GHz and 35V of tuning voltage with 3.6dB of insertion loss yielding a figure of merit of 85/spl deg//dB.     

Fabrication of niobium titanium nitride thin films with high superconducting transition temperatures and short penetration lengths

We report a systematic study of the superconducting and normal state properties of reactively sputtered Nb/sub 0.62/Ti/sub 0.38/N thin films deposited on thermally oxidized Si wafers. The superconducting transition temperature (T/sub c/) was found to increase from 12 K for films prepared on unheated substrates to over 16 K for films prepared on substrates maintained at 450/spl deg/C. A Nb buffer layer was found to improve T/sub c/ by /spl sim/0.5 K for growths at lower substrate temperatures. The films fabricated at 450/spl deg/C have an amply smooth surface (1.5/spl plusmn/0.25 nm root mean square roughness), a sufficiently high T/sub c/, and sufficiently small penetration depth (200/spl plusmn/20 nm at 10 K) to be useful as ground planes and electrodes for current-generation 10 K rapid single-flux quantum circuit technology.     

Distributed MEMS analog phase shifter with enhanced tuning

The design, fabrication, and measurement of a tunable microwave phase shifter is described. The phase shifter combines two techniques: a distributed capacitance transmission line phase shifter, and a large tuning range radio frequency (RF) microelectromechanical system (MEMS) capacitor. The resulting device is a large bandwidth, continuously tunable, low-loss phase shifter, with state-of-the-art performance. Measurements indicate analog tuning of 170/spl deg/ phase shift per dB loss is possible at 40 GHz, with a 538/spl deg/ phase shift per centimeter. The structure is realized with high-Q MEMS varactors, capable of tuning C/sub max//C/sub min/= 3.4. To our knowledge, this presents the lowest loss analog millimeter wave phase shifter performance to date.     

Fabrication of PRTs and analysis of characteristics

Platinum thin films have been prepared on Al/sub 2/O/sub 3/ substrates by DC magnetron sputtering. Platinum resistance thermometers have been fabricated and their characteristics analysed. We used a UV laser (wavelength 355 nm) to adjust the Pt thin films temperature sensors to 100 /spl Omega/ at 0/spl deg/C. As result of setting the Pt resistors to the target value of 109.73 /spl Omega/ at 25/spl deg/C, 82.3% of total resistors had a tolerance within /spl plusmn/0.03 /spl Omega/ and 17.7% were within /spl plusmn/0.06 /spl Omega/ of A-class tolerance according to DIN EN 60751. The PRTs which were fabricated in this research had excellent characteristics such as high accuracy, long-term stability, wide temperature range, good linearity, good repeatability and rapid response time.     

A 5-6-GHz bipolar quadrature-phase Generator

A wide-band fully monolithic quadrature-phase generator is implemented. It consists of a bipolar frequency doubler with differential outputs and a regenerative divider with 5 mV/sub rms/ maximum sensitivity. Measured residual phase noise is 相似文献   

A low-power 5-70-MHz seventh-order log-domain filter with programmable boost, group delay, and gain for hard disk drive applications

A seventh-order 0.05/spl deg/ equiripple linear-phase continuous-time filter employing log-domain-based instantaneous companding was designed and integrated in a mature bipolar process. The amount of boost (up to 13 dB) and group-delay adjustment (/spl plusmn/30%) are digitally programmable. The dc gain is controllable up to 10 dB, and the -3-dB frequency (f/sub c/) is tunable from 5 to 70 MHz. The output swing for 1% total harmonic distortion is higher than 100 mV/sub pp/, with a 1.5-V supply. The filter consumes very low power (5-13 mW for f/sub c/=70 MHz) compared to conventional implementations (e.g., 120 mW for f/sub c/=100MHz ).     

Effect of Mg doping on the superconducting properties of Cu/sub 1-x/Tl/sub x/Ba/sub 2/Ca/sub 3-y/Mg/sub y/Cu/sub 4/O/sub 12-/spl delta//

Superconducting properties of Cu/sub 1-x/Tl/sub x/Ba/sub 2/Ca/sub 3-y/Mg/sub y/Cu/sub 4/O/sub 12-/spl delta// (Cu/sub 1-x/Tl/sub x/Mg/sub y/-1234) material have been studied in the composition range y=0,1.5,2.25. The zero resistivity critical temperature [T/sub c/(R=0)] was found to increase with the increased concentration of Mg in the unit cell; for y=1.5 [T/sub c/(R=0)]=131 K was achieved which is hitherto highest in Cu/sub 1-x/Tl/sub x/-based superconductors. The X-ray diffraction analyses have shown the formation of a predominant single phase of Cu/sub 0.5/Tl/sub 0.5/Ba/sub 2/Ca/sub 3-y/Mg/sub y/Cu/sub 4/O/sub 12-/spl delta// superconductor with an inclusion of impurity phase. It is observed from the convex shape of the resistivity versus temperature measurements that our as-prepared material was in the region of carrier over-doping, and the number of carriers was optimized by postannealing experiments in air at 400/spl deg/C, 500/spl deg/C, and 600/spl deg/C. The T/sub c/(R=0) was found to increase with postannealing and the best postannealing temperature was found to be 600/spl deg/C. The mechanism of increased T/sub c/(R=0) is understood by carrying out infrared absorption measurements. It was observed through softening of Cu(2)-O/sub A/-Tl apical oxygen mode that improved interplane coupling was a possible source of enhancement of T/sub c/(R=0) to 131 K.     

Composite right/left handed transmission line phase shifter using ferroelectric varactors

A composite right/left handed (CRLH) transmission line (TL) phase shifter, using ferroelectric (Ba/sub 0.25/Sr/sub 0.75/TiO/sub 3/) varactors as tunable element, is presented for the first time. It is theoretically and experimentally demonstrated how the unique features of CRLH TLs, enables a differential phase shift with flat frequency dependence around the center frequency. The experimental prototype is a coplanar design integrated on a high resistive Si substrate. It includes four CRLH T-unit cells and has a physical length of 3850/spl mu/m. The ferroelectric varactors are realized in parallel plate version. Under 15-V dc bias applied over each varactor, the differential phase shift is flat around 17GHz and has an absolute value of 50/spl deg/.     

Low-Temperature Materials and Thin Film Transistors for Flexible Electronics

This paper addresses the low-temperature deposition processes and electronic properties of silicon based thin film semiconductors and dielectrics to enable the fabrication of mechanically flexible electronic devices on plastic substrates. Device quality amorphous hydrogenated silicon (a-Si:H), nanocrystalline silicon (nc-Si), and amorphous silicon nitride (a-SiN/sub x/) films and thin film transistors (TFTs) were made using existing industrial plasma deposition equipment at the process temperatures as low as 75/spl deg/C and 120/spl deg/C. The a-Si:H TFTs fabricated at 120/spl deg/C demonstrate performance similar to their high-temperature counterparts, including the field effect mobility (/spl mu//sub FE/) of 0.8 cm/sup 2/V/sup -1/s/sup -1/, the threshold voltage (V/sub T/) of 4.5 V, and the subthreshold slope of 0.5 V/dec, and can be used in active matrix (AM) displays including organic light emitting diode (OLED) displays. The a-Si:H TFTs fabricated at 75/spl deg/C exhibit /spl mu//sub FE/ of 0.6 cm/sup 2/V/sup -1/s/sup -1/, and V/sub T/ of 4 V. It is shown that further improvement in TFT performance can be achieved by using n/sup +/ nc-Si contact layers and plasma treatments of the interface between the gate dielectric and the channel layer. The results demonstrate that with appropriate process optimization, the large area thin film Si technology suits well the fabrication of electronic devices on low-cost plastic substrates.     

Anodic Oxidation of Si in Oxygen/Chlorine Plasma

By adding a few percent of chlorine to oxygen plasma, the anodization rate of Si was enhanced; for example, the rate was doubled for oxygen containing 3-percent chlorine. With a chlorine concentration of 1.5 percent, the density of trap states at the Si-SiO/sub 2/ interface was reduced from 7 X 10/sup 11//cm/sup 2//spl dot/eV to 5 X 10/sup 11//cm/sup 2/ /spl dot/eV at the midgap of Si; after annealing at 800/spl deg/C in argon for 60 min, it was reduced to 8 X 10/sup 10//cm/sup 2//spl dot/eV, and did not return to the original value after heating the specimen to 800/spl deg/C. The density and capture cross section of traps in plasma-anodic oxide were also measured using the constant-current avalanche-injection method. The number of electron traps with small cross sections in plasma-anodic SiO/sub 2/ films was reduced by annealing them at 800/spl deg/C in argon, but SiO/sub 2/ films which were anodized in oxygen/chlorine plasma showed an increase of trap density under the same annealing condition.     

Reliability investigation of 0.07-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel

The authors have investigated the reliability performance of G-band (183 GHz) monolithic microwave integrated circuit (MMIC) amplifiers fabricated using 0.07-/spl mu/m T-gate InGaAs-InAlAs-InP HEMTs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel on 3-in wafers. Life test was performed at two temperatures (T/sub 1/ = 200 /spl deg/C and T/sub 2/ = 215 /spl deg/C), and the amplifiers were stressed at V/sub ds/ of 1 V and I/sub ds/ of 250 mA/mm in a N/sub 2/ ambient. The activation energy is as high as 1.7 eV, achieving a projected median-time-to-failure (MTTF) /spl ap/ 2 /spl times/ 10/sup 6/ h at a junction temperature of 125 /spl deg/C. MTTF was determined by 2-temperature constant current stress using /spl Delta/G/sub mp/ = -20% as the failure criteria. The difference of reliability performance between 0.07-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel and 0.1-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with In/sub 0.6/Ga/sub 0.4/As channel is also discussed. The achieved high-reliability result demonstrates a robust 0.07-/spl mu/m pseudomorphic InGaAs-InAlAs-InP HEMT MMICs production technology for G-band applications.     

Arbitrary dual-band components using composite right/left-handed transmission lines

Arbitrary dual-band microstrip components using composite right/left-handed (CRLH) transmission lines (TLs) are presented. Theory, synthesis procedure, and implementation of the dual-band quarter-wave (/spl lambda//4) CRLH TL are presented. Arbitrary dual-band operation is achieved by the frequency offset and the phase slope of the CRLH TL. The frequency ratio of the two operating frequencies can be a noninteger. The dual-band /spl lambda//4 open/short-circuit stub, dual-band branch-line coupler (BLC), and dual-band rat-race coupler (RRC) are also demonstrated. The performances of these dual-band components are demonstrated by both simulated and measured results. Insertion loss is larger than 23 dB for the shunt /spl lambda//4 CRLH TL open-circuit stub and less than 0.25 dB for the shunt /spl lambda//4 CRLH TL short-circuit stub at each passband. The dual-band BLC exhibits S/sub 21/ and S/sub 31/ larger than -4.034 dB, return losses larger than 17 dB, isolations larger than 13 dB, phase differences 90/spl deg//spl plusmn/1.5/spl deg/, and gain imbalance less than 0.5 dB at each passband. The dual-band RRC exhibits S/sub 21/ and S/sub 31/ larger than -4.126 dB, return losses larger than 12 dB, isolations larger than 30 dB, phase difference 180/spl deg//spl plusmn/4/spl deg/, and gain imbalance less than 0.2 dB at each passband.     

Room-temperature self-organised In/sub 0.5/Ga/sub 0.5/As quantum dot laser on silicon

The first room-temperature operation of In/sub 0.5/Ga/sub 0.5/As quantum dot lasers grown directly on Si substrates with a thin (/spl les/2 /spl mu/m) GaAs buffer layer is reported. The devices are characterised by J/sub th//spl sim/1500 A/cm/sup 2/, output power >50 mW, and large T/sub 0/ (244 K) and constant output slope efficiency (/spl ges/0.3 W/A) in the temperature range 5-95/spl deg/C.     

BC high-/spl kappa//metal gate Ge/C alloy pMOSFETs fabricated directly on Si (100) substrates

Buried-channel (BC) high-/spl kappa//metal gate pMOSFETs were fabricated on Ge/sub 1-x/C/sub x/ layers for the first time. Ge/sub 1-x/C/sub x/ was grown directly on Si (100) by ultrahigh-vacuum chemical vapor deposition using methylgermane (CH/sub 3/GeH/sub 3/) and germane (GeH/sub 4/) precursors at 450/spl deg/C and 5 mtorr. High-quality films were achieved with a very low root-mean-square roughness of 3 /spl Aring/ measured by atomic force microscopy. The carbon (C) content in the Ge/sub 1-x/C/sub x/ layer was approximately 1 at.% as measured by secondary ion mass spectrometry. Ge/sub 1-x/C/sub x/ BC pMOSFETs with an effective oxide thickness of 1.9 nm and a gate length of 10 /spl mu/m exhibited high saturation drain current of 10.8 /spl mu/A//spl mu/m for a gate voltage overdrive of -1.0 V. Compared to Si control devices, the BC pMOSFETs showed 2/spl times/ enhancement in the saturation drain current and 1.6/spl times/ enhancement in the transconductance. The I/sub on//I/sub off/ ratio was greater than 5/spl times/10/sup 4/. The improved drain current represented an effective hole mobility enhancement of 1.5/spl times/ over the universal mobility curve for Si.     

A 5-6-GHz polyphase filter with tunable I/Q phase balance

A tunable polyphase filter with integrated input and output buffers was designed and fabricated in a 0.4 /spl mu/m SiGe BiCMOS technology with a 5-6-GHz bandwidth. Series tunable capacitors (varactors) provide phase tunability for the differential quadrature outputs of the polyphase filter. The tunable phase can be used to improve image rejection in Weaver or Hartley architectures, or mitigate in-phase and quadrature (I/Q) phase error in direct conversion or low-IF receivers. The die area of the fabricated circuit with pads is 920 /spl mu/m/spl times/ 755 /spl mu/m. Based on measurements, approximately 15/spl deg/ of I/Q phase imbalance can be tuned out using the fabricated polyphase filter, proving the concept of tunable phase. To the authors' knowledge, this is the first reported tunable I/Q balance polyphase network.     

Effect of CVD-SiO/sub 2/ film on reliability of GaAs MESFET with Ti/Pt/Au gate metal

The effect of CVD-SiO/sub 2/ films on the reliability of GaAs MESFET with Ti/Pt/Au gate metal was investigated. It was found that the mean time to failure (MTTF) of MESFET with 350/spl deg/C-depositied SiO/sub 2/ was only about one-seventh of that of the ones with 440/spl deg/C-SiO/sub 2/. It was also found that, in the storage test at 300/spl deg/C for 24 hours, diffusion of Pt into GaAs was accelerated when the SiO/sub 2/ deposition temperature was lower than 380/spl deg/C. FT-IR spectra indicated that the lower deposition temperature leads to a higher concentration of the residual hydrogen in SiO/sub 2/. Thermal differential spectrometry (TDS) demonstrated that hydrogen in SiO/sub 2/ could migrate even below 300/spl deg/C. In conclusion, the residual hydrogen in SiO/sub 2/ causes the degradation phenomena.     

Au/Si基片上沉积Bi_(1.5)Zn_(1.0)Nb_(1.5)O_7薄膜介电性能的研究

采用磁控溅射法在Au/Si基片上制备了铌酸锌铋BZN(Bi1.5Zn1.0Nb1.5O7)薄膜。在基片温度200℃、本底真空1×10-3Pa条件下,BZN靶溅射0.5h,作为自缓冲层;然后在400℃下溅射1.5h,薄膜总厚度为200nm,650℃原位真空退火1h。XRD分析显示该薄膜为〈222〉单一取向,结晶良好;AFM扫描显示表面平整;测试表明不同频率下薄膜的性能没有大的改变。实验证明,选用电阻率较小的Au电极材料有利于器件性能的提高,实验得到介电常数可调率约20%、损耗为0.002~0.004。     

Broadband 180/spl deg/ bit phase shifter using a /spl lambda//2 coupled line and parallel /spl lambda//8 stubs

In this paper, a broadband 180/spl deg/ bit phase shifter using a new switched-network was presented. The new network is composed of a /spl lambda//2 coupled line and parallel /spl lambda//8 open and short stubs, which are shunted at the edge points of a coupled line, respectively. According to a desired phase shift, it provides a controllable phase dispersive characteristic by the proper determination of Z/sub m/,Z/sub s/, and R values. The 180/spl deg/ bit phase shifter operated at 3 GHz was fabricated and experimented using design graphs which provide the required Z/sub m/,Z/sub s/ values, and I/O match and phase bandwidths. The experimental performances showed broadband characteristics.     

Polycrystalline silicon thin-film transistors fabricated by defect reduction methods

Fabrication of n-channel polycrystalline silicon thin-film transistors (poly-Si TFTs) at a low temperature is reported. 13.56 MHz-oxygen plasma at a 100 W, 130 Pa at 250/spl deg/C for 5 min, and heat treatment at 260/spl deg/C with 1.3/spl times/10/sup 6/-Pa-H/sub 2/O vapor for 3 h were applied to reduction of the density of defect states in 25-nm-thick silicon films crystallized by irradiation of a 30 ns-pulsed XeCl excimer laser. Defect reduction was numerically analyzed. Those treatments resulted in a high carrier mobility of 830 cm/sup 2//Vs and a low threshold voltage of 1.5 V at a laser crystallization energy density of 285 mJ/cm/sup 2/.     

Tapered distributed analogue tunable phase shifter with low insertion and return loss

Some improvements for distributed Schottky diode tunable phase shifters are carried out. First, near- and far-end sections are tapered to improve return loss. Then, to reduce device length, and the number of varactors, inductances are added in series with the varactors, leading to an improved C/sub max//C/sub min/ ratio. For a 360/spl deg/ tunable phase shifter working at 1 GHz, insertion losses are limited to 2.4 dB maximum. Return loss is better than 20 dB. The tapered sections allow a wide working frequency range, typically from 800 to 1200 MHz with the same characteristics: around 2.4 dB insertion losses, 20 dB return loss.