Microwave IC Research Articles

Ferroelectric HfO2 Capacitors for Varactor Application in GHz

Capacitance extraction of ferroelectric HfO2 capacitors was characterized at a frequency of 1 GHz. By applying a bias voltage in the non-switching region of the ferroelectric HfO2 films, a varactor operation was confirmed. Introduction The ferroelectric HfO2 layer has attracted attraction in CMOS and memory applications due to its scaling ability and process compatibility. Generally, ferroelctric capacitors show increase in the capacitance near the coercive field. By setting a proper bias to the ferroelectric capacitors, they can work as varactors under non-switching mode. As there is an increasing demand on-chip varactors for monolithic microwave ICs (MMICs) [1,2]. In this research, we measured the capacitance of the ferroelectric HfO2 capacitors at high frequency and confirmed the capacitance control. Measruements were done under on-wafer probing system in the frequency range of 10 MHz to 1 GHz [3]. Experiments Figure 1 shows the schematic cross-section of ferroelectric HfO2 capacitors. A 1 mm plasma SiO2 layer was first deposited on a high-resistive Si wafer f. A 12-nm-thick 5 mol% Y-doped HfO2 film were deposteid by atomic layer deposition (ALD). The top and bottom electrode were both W deposited by sputtering and patterned by reactive ion etching (RIE). Annealing to transform the HfO2 layer into ferroelectric pahse was conducted at 500 oC. Metal contacts of Au/Ni/Ti were deposited by thermal evaporation. Results and discussions Capacitance-voltage measurement taken from LCR meter at 10 kHz is shown in fig. 2. After polling process, the capacitance can be tuned by 32 % by controlling the bais voltage in the non-switching region. The capacitance values under different bias voltage, extracted from the S-parameters of capacitors with proper calibration patterns, are shown in fig. 3. Although the capacitance tuning was narrow compared to those obtained by the LCR meter, the varactor operation was confirmd with ferroelectric HfO2 capacitors. Conclusion A varactor operation in ferroelectric HfO2 capacitor at 1 GHz was confirmed.

Accurate Temperature Estimation for Each Gate of GaN HEMT With n-Gate Fingers

An analytical approach based on the thermoelectrical analogy to calculate the maximum channel temperature of multifinger AlGaN/GaN HEMT transistor is presented. The model is capable of predicting the maximum channel temperature, including the impact of the nonlinearity of thermal conductivity for every single gate with excellent accuracy. The model remains invariant under device scaling up and down and gives an accurate estimation for any number of gate fingers. Furthermore, the temperature field fluctuation due to the interaction between gates and variation in the number of gate fingers can be easily identified by the model. The validity of the proposed approach has been testified by comparing the results with those from infrared spectroscopy and numerical simulations for different AlGaN/GaN HEMT transistors with a different number of gates. The significance of models is justified by its ability to evaluate the temperature of any gate finger with high accuracy. Such an ability is particularly highly important while optimizing the structure layout and cooling system for high-power AlGaN/GaN HEMT transistors. The model can serve as a powerful tool for power devices and microwave IC designers and can be easily incorporated into SPICE empirical or physical-based models.

Physicochemical Characteristics of Copper Microstrip Lines of Microwave ICs Passivated with Accelerated Argon Ions

It is found that there are difficulties in restoring the initial chemical activity of copper after passivation by means of ion-beam treatment. The physicochemical and electrical parameters of copper coatings passivated with accelerated medium-energy Ar ions, as well as the microwave characteristics of microstrip lines based on them, are investigated. The modes of ion-beam passivation leading to a significant increase in the chemical resistance of copper are ascertained. It is shown that depassivation of ion-passivated copper layers is possible in an oxygen plasma, in etching solutions with hydrofluoric acid, and by treatment with short ultraviolet radiation. Ion-beam passivation leaves the microwave characteristics of copper microstrip lines almost unchanged with an increase in their resistance to oxidation up to 100 times. The results suggest the possibility of using ion-beam passivation technology for the use of ion-passivated copper as an analog of gold in microwave microelectronic devices.

Монолитные СВЧ ИС миллиметрового диапазона на основе нитридных гетерострук-тур с интегрированными антенными элементами

Монолитные СВЧ ИС миллиметрового диапазона на основе нитридных гетерострук-тур с интегрированными антенными элементами

Temperature Effect on DC and Equivalent Circuit Parameters of 0.15- $\mu \text{m}$ Gate Length GaN/SiC HEMT for Microwave Applications

Thermal characterizations and modeling have been carried out on a $0.15~\mu \text{m} \,\, \times $ ( $4 \times 50$ ) $\mu \text{m}$ gate GaN-/SiC-based high-electron-mobility transistor varying the temperature from −40 °C to 150 °C and the frequency up to 50 GHz using on-wafer measurements. The thermal behavior of the dc parameters along with thermal resistance estimation and the equivalent circuit parameters along with cutoff and maximum frequencies were analyzed and reported using a single device. The temperature coefficients of these parameters were presented and deduced the influence of thermal effects on device parameters. These results are important for the circuit designer for future advancement and design optimizations of GaN-based monolithic microwave ICs.

Design of low power low phase noise negative resistance Ku‐band VCO using planar resonator pair

ABSTRACTNew negative resistance voltage‐controlled oscillator (VCO) at Ku‐band is designed. The proposed topology uses packaged NPN Silicon Germanium RF transistor and two parallel resonator structures connected to the device emitters. Novel active open ended planar structure is proposed as a resonator for the VCO. Resonator is analyzed in terms of required reflection coefficient and input impedance. Resonator's quality factor varies in between 159 and 235 as a function of tuning voltage. VCO microwave IC is fabricated on TMM10i soft substrate with 17.5μm Cr‐Cu‐Au metallization process. VCO can be tuned for 180MHz by varying resonators’ varactors from 0 to 22 V. Measured output power remains in between 4.2 and 8.06 dBm for the entire tuning range. Measured phase noise is −145 dBc/Hz at 1 MHz offset with 8 V tuning voltage. Normalized phase noise figure of merit for the VCO is −214.4 dBc/Hz. The circuit has low power consumption of 25.5 mW and high DC to RF conversion efficiency (ηDC‐RF). © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1938–1941, 2015

Air‐gapped microcoxial transmission line for ultrawide band microwave and millimeter wave ICS

AbstractWe present an air‐gapped microcoaxial transmission line fabricated on low resistivity silicon substrate (ρ = 10 Ω·cm). The transmission line is based on a damascene copper process and has demonstrated superior microwave properties of low attenuation (<0.02 dB/mm) and a low and constant effective permittivity (∼1.02) in the frequency range of 0.1–40 GHz. The fabrication process has a low thermal budget, and can be easily integrated with the advanced Cu back‐end‐of‐line CMOS to fabricate low‐loss and high quality factor microwave and millimeter wave passives for system‐on‐chip applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1462–1465, 2014

III-nitride microwave control devices and ICs

The growing complexity and functionality of modern microwave systems put increasing demands on the performance and reliability of RF control devices. Low channel sheet resistance in the on-state and small leakage currents in the off-state, extremely high breakdown voltages, chemical inertness and planar structure make III-nitride heterostructure-based devices uniquely suitable for the next-generation switching devices. The AlInN-based devices and devices using low-conducting layers for controlling surface field and surface charges are expected to further boost the performance. This paper presents a review of III-nitride control devices based on heterostructure field-effect transistors (HFETs), insulated gate HFETs (MISHFETs) and novel capacitively coupled contact and frequency configurable electronics technologies.

Smarter ICs

This article presented the possibilities of making microwave and mm-wave ICs more intelligent through a combination of established Si/SiGe BiCMOS technologies, which allow for complex ICs combining a multitude of high-speed analog and digital functions, and RFMEMS processing tightly integrated with the baseline BiCMOS technology. The addition of RFMEMS switches and integrated antennas enhanced by micromachining especially pays off at millimeter waves, where chip-to-board interconnects become increasingly cumbersome, and RFMEMS reconfiguration switches offer unparalleled low loss, high isolation, and high linearity.

GaN-based pin diodes for microwave switching IC applications

GaN-based pin diodes were fabricated and characterised for microwave switching IC applications. The fabricated GaN pin diode with a p-metal diameter of 50 µm demonstrated a 3.8 V turn-on voltage, a 370 V breakdown voltage and a power figure of merit value of 178.5 MW/cm2 with an on-state resistance of 29 Ω and an off-state capacitance of 47 fF. To the authors’ best knowledge, this result is the first RF characterisation of the GaN pin diode for microwave IC applications.

The effect of ionizing radiation on the characteristics of silicon-germanium microwave integrated circuits

The effect of ionizing radiation on the characteristics of silicon-germanium microwave ICs has been experimentally studied. Radiation tolerance criteria have been established and absolute tolerance levels of the SiGe ICs to dose and pulse ionizing radiation have been determined. Comparative analysis of the tolerance factors of the microwave ICs fabricated using different technologies is made.

Design of passive elements for monolithic silicon-germanium microwave ICs tolerant to ionizing radiation

Techniques for the design of passive elements for monolithic silicon-germanium microwave ICs, tolerant to ionizing radiation have been developed with regard to specific features of the design of microwave passive elements on conducting silicon substrates. A set of the elements for operation at frequencies up to 24 GHz has been designed and fabricated, which includes transmission lines, inductances, and symmetrical transformers for application in a user library for the silicon-germanium BiCMOS technology with design rules of 0.25 μm.

A wafer-level 3D packaging structure with Benzocyclobutene as a dielectric for multichip module fabrication

A new wafer-level 3D packaging structure with Benzocyclobutene (BCB) as interlayer dielectrics (ILDs) for multichip module fabrication is proposed for application in the Ku-band wave. The packaging structure consists of two layers of BCB films and three layers of metallized films, in which the monolithic microwave IC (MMIC), thin film resistors, striplines and microstrip lines are integrated. Wet etched cavities fabricated on the silicon substrate are used for mounting active and passive components. BCB layers cover the components and serve as ILDs for interconnections. Gold bumps are used as electric interconnections between different layers, which eliminates the need to prepare vias by costly dry etching and deposition processes. In order to get high-quality BCB films for the subsequent chemical mechanical planarization (CMP) and multilayer metallization processes, the BCB curing profile is optimized and the roughness of the BCB film after the CMP process is kept lower than 10 nm. The thermal, mechanical and electrical properties of the packaging structure are investigated. The thermal resistance can be controlled below 2 °C/W. The average shear strength of the gold bumps on the BCB surface is around 70 N/mm2. The performances of MMIC and interconnection structure at high frequencies are optimized and tested. The S-parameters curves of the packaged MMIC shift slightly showing perfect transmission character. The insertion loss change after the packaging process is less than 1 dB range at the operating frequency and the return loss is less than –8 dB from 10 to 15 GHz.

A wafer-scale packaging structure with monolithic microwave integrated circuits and passives embedded in a silicon substrate for multichip modules for radio frequency applications

A wafer-level packaging structure with chips and passive components embedded in a silicon substrate for multichip modules (MCM) is proposed for radio frequency (RF) applications. The packaging structure consists of two layers of benzocyclobutene (BCB) films and three layers of metalized films, in which the monolithic microwave ICs (MMICs), thin film resistors, striplines and microstrip lines are integrated. The low resistivity silicon wafer with etched cavities is used as a substrate. The BCB films serve as interlayer dielectrics (ILDs). Wirebonding gold bumps are used as electric interconnections between different layers, which eliminate the need of preparing vias by costly procedures including dry etching, metal sputtering and electroplating. The chemical mechanical planarization (CMP) is used to uncover the gold bumps, and the BCB curing profile is optimized to obtain the appropriate BCB film for CMP process. In this work, the thermal, mechanical, electrical as well as RF properties of the packaging structure are investigated. The packaging thermal resistance can be controlled below 2 °C W−1. The average shear strength of the gold bumps on the BCB surface is about 70 MPa. In addition, a Kelvin test structure is fabricated for resistance testing of the vertical vias. The performances of MMIC and interconnection structure at high frequency are simulated and tested. The testing results reveal that the slight shifting of S-parameter curves of the packaged MMIC indicates perfect transmission characteristics at high frequency. For the transition structure of transmission line, the experimental results are compatible with the simulation results. The insertion loss (S21) is below 0.4 dB from 0 to 40 GHz and the return loss (S11) is less than −20 dB from 0 to 40 GHz. For a low noise amplifier (LNA) chip, the S21 shifting caused by the packaging structure is below 0.5 dB, and S11 is less than −10 dB from 8 GHz to 14 GHz.

Study the influence of transmission line loss on the performance of matrix amplifiers

An analytical approach is presented to investigate the performance of matrix amplifiers containing both hetero-junction bipolar and high-electron-mobility transistors. An analytical relation for attenuation function of the central line of the matrix amplifier is developed which can be employed in the consideration of the influence of several parameters on the device performance. It is shown that this structure may have lower attenuation respect to the traditional HEMT_HEMT and HEMT_HBT matrix amplifiers. The proposed technique is applicable in improving the performance of Microwave and mm-wave ICs.

Microwave Dielectric Ceramics and Devices for Wireless Technologies

In this paper, several kinds of synthesis techniques were adopted; not only conventional solidstate reaction method but also solution synthesis techniques, including co-precipitation and hydrothermal synthesis, in addition to the gel-casting for complex shape of ceramic components and tape-casting of large scale thin plate for microwave IC. Different kinds of microwave ceramics were prepared, such as materials with low permittivity and high quality factor, moderate permittivity and good quality factor, and, high permittivity and reasonable quality factor, in addition to near zero of temperature coefficient of resonance frequency. Series of microwave devices were developed, for examples, dielectric resonators, dielectric filters, GPS antennas, communication connectors, and thin substrates for microwave IC.

ANALYSIS OF V TRANSMISSION LINES RESPONSE TO EXTERNAL ELECTROMAGNETIC FIELDS

In the present paper the response of V transmission line to electromagnetic illumination has been obtained. Also in order to determine the VTL frequency operation band for both TE and TM modes a Gaussian pulse source has been applied to the structure. The VTL structure has received considerable attention in high frequency and microwave IC packaging. The purpose of this study is to determine high frequency design considerations in order to reduce the effects of electromagnetic interference (EMI) on the VTL structure and maintain the desired performance. It was observed that the effect of incident EM waves on the V lines performance is considerably lower than conventional microstrips, however the V lines are more sensitive to sources at close proximity. In addition, although the V lines show lower dispersion at higher frequencies, their frequency operation band is limited by a resonance like behavior which is directly related to the V groove dimensions. The full wave analysis is carried out using the Yee-cell based 2 Dimensional Finite Difference Time Domain method (2D-FDTD), while enforcing a very stable and efficient mesh truncation technique.

Silver coplanar waveguides as the passive components of choice for microwave integrated circuits

High quality broadband passive components are needed for MMIC/MIC in silicon. Coplanar waveguides (CPW) provide an effective way to implement passives in microwave ICs. Silver “fat” wires in the back end interconnects, used for CPW fabrication, will reduce the bulk resistive loss in metallization to the lowest possible level, which is vital to minimize noise. Electromigration, electrochemical migration, and agglomeration issues are not a problem for silver microwave passive components, because of their coarse dimensions and the low current densities encountered in these structures. In this work Ag and Cu CPWs were designed, fabricated, and tested. Silver CPWs showed a 2–3Ω∕cm improvement in resistance over copper devices at 20GHz.

Quality factor and inductance in differential IC implementations

Monolithic inductors are widely used in microwave ICs and RFICs. Design considerations for inductors on low-resistivity substrates have been described. A /spl pi/-equivalent model, used to account for various loss mechanisms, can be helpful in understanding differences in the definition of L and Q for single-ended and differential structures that exist in the literature. Specific uses for the equations in this article have been outlined. The L and Q for an example monolithic, differential inductor were extracted from measured two-port S-parameters using equations for differential configurations on low-resistivity substrates.

Focused Ion Beam Applied to Non-Silicon Material: Cross Sectioning Microwave Devices

Abstract High-frequency devices such as monolithic microwave ICs (MMICs) are used in telecommunication devices as well as in satellites for earth imaging and radar applications. This article discusses the use of focused ion beam (FIB) cross sectioning and sample decoration techniques for analyzing MMICs and III-V materials.