High-resistivity Silicon Substrate Research Articles

Millimeter-wave antenna designs for 60 GHz applications: SoC and SiP approaches

Antenna on chip (AoC) and antenna in package (AiP) solutions for millimeter-wave (mmWave) applications and their characterization are presented in this paper. Antenna integration on low resistivity (LR) and high resistivity (HR) silicon substrate are expected. And, in a packaging approach, the combination of antenna on silicon with a material, which has the effect of a “lens”, allowing increasing gain is presented. In a second part, to satisfy beamforming capabilities, a hybrid integration of the antenna on silicon and glass substrates is proposed.

Coplanar Waveguides on High-Resistivity Silicon Substrates With Attenuation Constant Lower Than 1 dB/mm for Microwave and Millimeter-Wave Bands

Coplanar waveguides (CPWs) with extremely low loss have been successfully developed on high-resistivity silicon (HR-Si) substrates as interposers of multichip modules for microwave and millimeter-wave bands. The attenuation constant of these CPWs on HR-Si is less than 1 dB/mm for frequencies up to 100 GHz, which is comparable with that of CPWs on semi-insulating compound semiconductor substrates. Conventional CPW structures show a larger attenuation constant due to the effects of the low-resistivity layer generated at the interface between the insulating layer of SiN and the HR-Si substrate, which has been detected through both experimental investigations and numerical calculations. A CPW structure that suppresses the effects of the low-resistivity layer is presented in this paper. The fabrication process is rather simple and can be smoothly integrated in conventional semiconductor device fabrication processes.

A Nanocrystalline Silicon Surface-Passivation Layer on an HR-Si Substrate for RFICs

In this letter, a thin nanocrystalline silicon (nc-Si) layer grown by hot-wire chemical vapor deposition is used as a surface-passivation layer (SPL). The transmission loss αTL of coplanar waveguide lines on an oxide-coated high-resistivity silicon substrate with a 100-nm-thick nc-Si SPL is less than 1.05 dB/cm at frequencies up to 20 GHz. Furthermore, we found that the very thin nc-Si SPL is also greatly effective for reducing crosstalk noise and further enhancing the isolation characteristics of electrical circuits. Therefore, an nc-Si SPL is capable of providing good surface passivation for RF IC applications.

Comb-drive GaN micro-mirror on a GaN-on-silicon platform

We report here a double-sided process for the fabrication of a comb-drive GaN micro-mirror on a GaN-on-silicon platform. A silicon substrate is first patterned from the backside and removed by deep reactive ion etching, resulting in totally suspended GaN slabs. GaN microstructures including the torsion bars, movable combs and mirror plate are then defined on a freestanding GaN slab by the backside alignment technique and generated by fast atom beam etching with Cl2 gas. Although the fabricated comb-drive GaN micro-mirrors are deflected by the residual stress in GaN thin films, they can operate on a high resistivity silicon substrate without introducing any additional isolation layer. The optical rotation angles are experimentally characterized in the rotation experiments. This work opens the possibility of producing GaN optical micro-electro-mechanical-system (MEMS) devices on a GaN-on-silicon platform.

Comprehensive Study on the Bias-Dependent Equivalent-Circuit Elements Affected by PECVD SiN Passivation in AlGaN/GaN HEMTs

In this paper, a comprehensive study on the effect of plasma-enhanced chemical-vapor-deposited SiN surface passivation on the bias-dependent small-signal equivalent-circuit elements is carried out for AlGaN/GaN high-electron mobility transistors on a high-resistivity silicon substrate. The direct-current and small-signal performance of the device was found to be improved by surface passivation. The small-signal equivalent-circuit parameters at various gate and drain biases were extracted, and the physical mechanisms of their bias-dependent behaviors before and after passivation are discussed in detail.

Nanocrystalline silicon thickness dependence of transmission characteristics of CPWs on surface-passivated high-resistivity silicon substrates

A nanocrystalline silicon (nc-Si) layer was used as a surface-passivation layer (SPL) on a high-resistivity silicon (HR-Si) substrate. The transmission loss (αTL) of coplanar waveguide (CPW) lines on oxide/SPL/HR-Si substrates with an nc-Si SPL of 100, 200, and 400 nm was measured and analysed. The experimental results demonstrate that the thicker nc-Si SPL provides better passivation effect and the αTL can be down to 0.69 dB/cm. The equivalent series resistance and shunt conductance were extracted to investigate the dependence of αTL on the SPL thickness. The cross-talk effect of CPWs on oxide/SPL/HR-Si substrates was also studied.

Beyond 100 GHz AlN/GaN HEMTs on silicon substrate

A report is presented on high-speed 100 nm AlN/GaN high-electron-mobility transistors (HEMTs) grown on (111) high-resistive silicon substrate. The device delivers an extrinsic peak transconductance gm=530 mS/mm, a maximum current of 1.74 A/mm, and current gain and maximum oscillation cutoff frequencies of ft=103 GHz and fmax=162 GHz, which represent the highest cutoff frequencies for AlN/GaN HEMTs on silicon substrate. The results show the outstanding potential of this material system grown on silicon for low-cost high-power millimetre-wave applications.

ELECTROTHERMAL EFFECTS IN HIGH DENSITY THROUGH SILICON VIA (TSV) ARRAYS

Electrothermal effects in various through silicon via (TSV) arrays are investigated in this paper. An equivalent lumped-element circuit model of a TSV pair is derived. The temperature-dependent TSV capacitance, silicon substrate capacitance and conductance are examined for low-, medium-, and high-resistivity silicon substrates, respectively. The partial-element equivalent-circuit (PEEC) method is employed for calculating per-unit-length (p.u.l.) resistance, inductance, insertion loss and characteristic impedances of copper and polycrystalline silicon (poly-Si) TSV arrays, and their frequencyand temperature-dependent characteristics are treated rigorously. The modified time-domain finite-element method (TD-FEM), in the presence of a set of periodic differential-mode voltage pulses, is also employed for studying transient electrothermal responses of 4and 5-TSV arrays made of different materials, with their maximum temperatures and thermal crosstalk characterized thoroughly.

Impact of Crosstalk into High Resistivity Silicon Substrate on the RF Performance of SOI MOSFET

Crosstalk propagation through silicon substrate is a serious limiting factor on the performance of the RF devices and circuits. In this work, substrate crosstalk into high resistivity silicon substrate is experimentally analyzed and the impact on the RF behavior of silicon-on-insulator (SOI) MOS transistors is discussed. The injection of a 10 V peak-to-peak single tone noise signal at a frequency of 3 MHz ( fnoise) generates two sideband tones of −56 dBm separated by fnoise from the RF output signal of a partially depleted SOI MOSFET at 1 GHz and 4.1 dBm. The efficiency of the introduction of a trap-rich polysilicon layer located underneath the buried oxide (BOX) of the high resistivity (HR) SOI wafer in the reduction of the sideband noise tones is demonstrated. An equivalent circuit to model and analyze the generation of these sideband noise tones is proposed.

Transmittance investigation on capacitive mesh on thick dielectric substrates as output windows for optically pumped terahertz lasers

This paper reports that an output window for optically pumped terahertz (THz) laser has been fabricated by depositing a capacitive nickel-mesh on a thick high-resistivity silicon substrate (approximating to 5 mm thick). Unlike the conventional process of depositing a gold film approximating to 100 nm on negative photoresist using electron-beam evaporation, a nickel film approximating to 1.5 μm thick is directly deposited on the clean surface of dielectric substrate using magnetron sputtering and then a positive photoresist is spun onto the nickel metal surface at 6000 r for 60 s. A transmittance spectrum of the output window in a certain frequency range (say, from zero to 1 THz) has been obtained by using THz time domain spectroscopy. Moreover a transmittance spectrum simulated numerically has also been estimated with respect to the output window using the transmission-line model (TLM) containing attenuation component from dielectric substrate. The simulation results show that the TLM can explain well the experimental curve in a certain frequency range from zero to 1 THz. Thus it is demonstrated that the improved optical component can be efficiently used as both output coupler and output window for optically pumped THz lasers.

New CMOS-Compatible Micromachined Embedded Coplanar Waveguide

This paper proposes a new robust micromachined embedded coplanar waveguide (CPW). The central and ground plates are partially bent and overlapped within the trench, and due to tight coupling of the E -field between the overlapped plates, the micromachined embedded CPW line is capable of a wide range characteristic impedance (17.9-92.3 Ω), in a compact size. Furthermore, the area in which the E -field radiates into the substrate of the micromachined embedded CPW is quite narrow compared to conventional CPWs, and therefore, the dielectric loss of the micromachined embedded CPW can be effectively suppressed. Compared with conventional CPW lines, the embedded CPW lines have shown a marked reduction in loss, especially in the low-impedance range. The micromachined embedded CPW lines on the high-resistivity silicon substrate (ρs = 15 000 Ω · cm) achieve a measured loss as low as 0.81 dB/cm at 50 GHz. Moreover, the fabrication process of the micromachined embedded CPW line is compatible with the CMOS process. These features make micromachined embedded CPW a promising transmission line for RF integrated circuit application.

Study on the Temperature Dependence of the Microwave-Noise Characteristics in AlGaN/GaN HEMTs

In this brief, we present a detailed study on the temperature dependence of the microwave noise characteristics in AlGaN/GaN high-electron mobility transistors on high-resistivity silicon substrate. The temperature-dependent microwave noise parameters of AlGaN/GaN HEMT on Si were measured over a wide temperature range of -50°C-200°C. The physical mechanisms of the temperature behavior for the overall noise figure ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NF</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ) and internal noise sources coefficients ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> , <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> , and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> ) were analyzed and discussed in detail.

Impact of neutron irradiation on the RF properties of oxidized high-resistivity silicon substrates with and without a trap-rich passivation layer

This work investigates the influence of high-energy neutrons on oxidized high-resistivity silicon substrates (HR-Si). Two oxide thicknesses as well as the presence of a trap-rich passivation layer are considered. The impact of neutron irradiation is directly related to the competition between the generation of interface traps added to the mobility and carrier lifetime degradation, which are beneficial to reduce parasitic surface conduction (PCS) into the Si substrate similarly to the passivation layer, and accumulation of radiation-induced positive charges in oxide, which would unfortunately increase PSC. It is shown that under neutron irradiation, RF losses are strongly reduced in the case of thin oxide ( t ox = 50 nm), while substrates with a polysilicon passivation layer are almost insensitive to the neutron irradiation.

Improved Linearity for Low-Noise Applications in 0.25-$ \mu\hbox{m}$ GaN MISHEMTs Using ALD $\hbox{Al}_{2}\hbox{O}_{3}$ as Gate Dielectric

Improved device linearity for low-noise applications has been demonstrated in 0.25-μm AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) using atomic-layer-deposited (ALD) Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as gate dielectric. The measured dc transconductance, microwave small signal, and noise performance feature less dependence on drain current as compared to conventional Schottky-gate AlGaN/GaN HEMTs. Two-tone intermodulation measurement shows that the MISHEMT has a higher value of third-order intercept (IP3). The improved device linearity suggests that the ALD Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /AlGaN/GaN MISHEMT on high-resistivity silicon substrate is promising for high-linearity low-noise amplifier applications.

A system for characterization of DEPFET silicon pixel matrices and test beam results

The DEPFET pixel detector offers first stage in-pixel amplification by incorporating a field effect transistor in the high resistivity silicon substrate. In this concept, a very small input capacitance can be realized thus allowing for low noise measurements. This makes DEPFET sensors a favorable technology for tracking in particle physics. Therefore a system with a DEPFET pixel matrix was developed to test DEPFET performance for an application as a vertex detector for the Belle II experiment. The system features a current based, row-wise readout of a DEPFET pixel matrix with a designated readout chip, steering chips for matrix control, a FPGA based data acquisition board, and a dedicated software package. The system was successfully operated in both test beam and lab environment. In 2009 new DEPFET matrices have been characterized in a 120 GeV pion beam at the CERN SPS. The current status of the DEPFET system and test beam results are presented.

Development of different K-band MEMS phase shifter designs for satellite COTM terminals

This work presents the design, manufacturing, and testing of three 5-bit K-band Micro-Electro-Mechanical-Systems (MEMS) phase shifters based on similar architectures (combination of switched line and loaded line) but employing different MEMS switch typologies (cantilevers and air bridges) and RF junctions (SP2T and SP4T). All devices have been monolithically manufactured on 200 µm thick high resistivity silicon substrate (4″) by using the Fondazione Bruno Kessler (FBK) RF MEMS process. The performance of the different devices has been compared in order to identify the best configuration to be implemented in electronically steerable phased array antennas for satellite COTM (communication on the move) terminals. Excellent performances were measured for the dielectric-free pad RF MEMS switches as well as the single bits constituting the phase shifter. The three 5-bit devices show return losses better than 15 dB for all states, with average insertion loss of 3.5 dB for the clamped–clamped, SP2T-based design, 2.2 dB for the cantilever, SP2T-based device and 2.1 dB for the cantilever, SP4 T-based design. A low-cost Surface Mountable Technology (SMT) one-level package has been developed as well to allow the phase shifter integration into phased array antennas by using automatic surface mounting techniques. The design and simulation of the SMT package are also presented together with its measured RF performance.

A 1.35 mJ ammonia Fabry–Perot cavity terahertz pulsed laser with metallic capacitive-mesh input and output couplers

An efficient ammonia Fabry–Perot (F–P) cavity terahertz (THz) laser has been studied experimentally in this article. The input and output couplers also served as sealed windows fabricated by depositing nickel capacitive metallic meshes on ZnSe and high-resistivity silicon substrates have been constructed as a F–P oscillator. Using the THz laser, the properties related to THz pulsed laser such as beam profile, delay, the minimum pump intensity, THz lasing threshold and THz atmospheric transmission have been investigated. Further, the factors such as pump intensity and gas pressure influencing the efficiency of THz laser have also been discussed. Finally, the highest output pulse energies of 1.35 mJ at 90 μ m operating at 1.09 kPa ammonia pressure pumped by a 402 mJ TEA CO 2 laser with 9R (16) line have been generated, and photon conversion efficiencies of 6.5% have been achieved.

Theoretical Design of a Wedged Output Coupler Coated by Capacitive Strip-Grating for Optically Pumped Terahertz Lasers

An output coupler for optically pumped terahertz laser consisting of capacitive strip-grating and wedged high-resistivity silicon substrate is designed theoretically and its transmittance performance is also discussed. The etalon effects frequently occurring in previous experiments are effectively suppressed, and thus a flat and accurate transmittance spectrum is obtained in a narrow wavenumber interval of 2 cm−1 near a particular center wavenumber. Furthermore the transmittance sensitivity to the slight shift of substrate thickness is also completely eliminated. The wedged output coupler is easy to fabricate and its substrate may be used repeatedly to meet various transmittance requirements.

An integrated compact coplanar waveguide high‐pass filter implemented on high resistivity silicon substrate

AbstractIn this article, the fabrication of a compact and high performance semi‐lumped coplanar waveguide high‐pass filter (CPW‐HPF) implemented on high resistivity silicon (HRS) substrate is proposed.The design procedure and the equivalent circuit of the proposed semi‐lumped CPW‐HPF is discussed. The filter structure is simple, and the performances are fairly good. This designed filter at cutoff frequency fc of 21.6 GHz has very good measured characteristics including a balance passband of S21 of −0.5 ± 0.3 dB and a sharp band edge rejection. Experimental results of the fabricated filter show a good agreement with the predicted results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1150–1153, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25116

Dielectric microwave characterizations of (Ba,Sr)TiO3 film deposited on high resistivity silicon substrate: Analysis by two-dimensional tangential finite element method

( Ba , Sr ) TiO 3 (BST) thin films were deposited on high resistivity silicon substrates by in situ rf magnetron sputtering. A buffer layer was used to improve the cristallinity of the films, the composition was fixed to Ba/Sr=30/70. The relative permittivity and the losses were measured up to 60 GHz using coplanar strip lines. The dispersion of the permittivity and the losses has been determined with a home made numerical code based on finite elements: ELFI. We show that, with the measurements of the scattering parameters coupled with ELFI, it is possible to know the BST complex permittivity over a very broad frequency band. The BST films deposited by in situ (700 °C) present excellent properties between 1 to 60 GHz. The relative permittivity is in the order of 270 and the losses are very small 0.09 at 60 GHz. These structures BST/silicon high resistivity show good potentialities for devices microwaves applications which need future integration in a silicon environment.