High-resistivity Silicon Substrate Research Articles

Analytical Modeling of Multilayered Coplanar Waveguides Including Ferromagnetic Thin Films on Semiconductor Substrates

A review of analytical modeling for conventional coplanar waveguides (CPWs) is carried out. Thus, a refined model based on an electrical equivalent circuit with distributed elements is proposed to properly describe the frequency behavior of a multilayered CPW on a semiconductor substrate. Furthermore, inductors based on such CPWs using a ferromagnetic thin film are studied. Realizations are shown based on CMOS technology and RF measurements are presented. The analytical results are in agreement with the experimental data. Discussions include specific losses originating from the use of a high-resistivity silicon substrate and from the gyromagnetic resonance due to ferromagnetic thin films. These two contributions are accurately evaluated.

High Microwave-Noise Performance of AlGaN/GaN MISHEMTs on Silicon With $\hbox{Al}_{2}\hbox{O}_{3}$ Gate Insulator Grown by ALD

High microwave-noise performance is realized in AlGaN/GaN metal-insulator semiconductor high-electron mobility transistors (MISHEMTs) on high-resistivity silicon substrate 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 insulator. 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 with a 0.25- ¿m gate length shows excellent microwave small signal and noise performance. A high current-gain cutoff frequency <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fT</i> of 40 GHz and maximum oscillation frequency <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> of 76 GHz were achieved. At 10 GHz, the device exhibits low minimum-noise figure (NF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ) of 1.0 dB together with high associate gain ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ga</i> ) of 10.5 dB and low equivalent noise resistance ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Rn</i> ) of 29.2 ¿. This is believed to be the first report of a 0.25-¿m gate-length GaN MISHEMT on silicon with such microwave-noise performance. These results indicate that the AlGaN/GaN MISHEMT with 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> gate insulator on high-resistivity Si substrate is suitable for microwave low-noise applications.

Millimeter-wave GaN-based HEMT development at ETH-Zürich

We review the AlGaN/GaN high electron mobility transistor (HEMT) activities in the Millimeter-Wave Electronics Group at ETH-Zürich. Our group's main thrust in the AlGaN/GaN arena is the extension of device bandwidth to higher frequency bands. We demonstrated surprising performances for AlGaN/GaN HEMTs grown on high-resistivity (HR) silicon (111) substrates, and extended cutoff frequencies of 100 nm gate devices well into the millimeter (mm)-wave domain. Our results narrow the performance gap between GaN-on-SiC (or sapphire) and GaN-on-silicon and establish GaN-on-Si as a viable technology for low-cost mm-wave electronics. We here contrast the difference in behaviors observed in our laboratory between nominally identical devices built on high-resistivity silicon (HR-Si) and on sapphire substrates; we show high-speed devices with high-cutoff frequencies and breakdown voltages which combine fT,MAX × BV products as high as 5–10 THz V, and show AlGaN/GaN HEMTs with fT values exceeding 100 GHz on HR-Si. Although the bulk of our activities have so far focused on AlGaN/GaN HEMTs on HR-Si, our process produces excellent device performances when applied to GaN HEMTs on SiC as well: 100 nm gate transistors with fT &gt; 125 GHz have been realized at ETH-Zürich.

Low Specific On-Resistance AlGaN/AlN/GaN High Electron Mobility Transistors on High Resistivity Silicon Substrate

High performance undoped AlGaN/AlN/GaN high electron mobility transistors (HEMTs) on high resistivity Si were achieved by implementing an ohmic-recess contact by inductively coupled plasma etching using four layers of Ti/Al/Ni/Au metal. About a 17.5% increase in drain current density and a 12.5% increase in extrinsic transconductance were observed on ohmic-recess-etched HEMTs. This is due to the reduction in the parasitic resistance such as contact resistance, drain resistance, and source resistance of the device. The ohmic-recess-etched AlGaN/AlN/GaN HEMT with a gate–drain spacing exhibited the lowest specific on-resistance of with an off-state breakdown voltage of 194 V. The highest ever reported figure-of-merit has been achieved in the ohmic-recess-etched AlGaN/AlN/GaN HEMTs on silicon. Ohmic recess is useful for undoped AlGaN/AlN/GaN HEMTs to achieve low with high figure-of-merit.

An Efficient Photon Conversion Efficiency Ammonia Terahertz Cavity Laser

An efficient ammonia terahertz (THz) cavity laser is reported experimentally. Unlike the past design schemes such as hole couplers and freestanding mesh couplers, in our systems the input and output couplers are fabricated by depositing nickel capacitive metallic meshes on ZnSe and high-resistivity silicon substrates. Thus the couplers not only can be constructed as an F-P oscillator but also can be used as sealed windows that are easier to perform the adjustment of alignment with. To enhance THz laser output energy and photon conversion efficiency, the dominant factors such as pump intensity and gas pressure are investigated experimentally. Finally, a 1.35 mJ terahertz radiation of ammonia laser with 90 μm wavelength (3.33 THz) operating at 1.09 kPa pumped by a 402 mJ TEA CO2 laser with 9R (16) line is generated, and photon conversion efficiencies of 6.5% are achieved.

102-GHz AlInN/GaN HEMTs on Silicon With 2.5-W/mm Output Power at 10 GHz

Grown on a (111) high-resistivity silicon substrate, 0.1-mum gate AlInN/GaN high-electron mobility transistors (HEMTs) achieve a maximum current density of 1.3 A/mm, an extrinsic transconductance of 330 mS/mm, and a peak current gain cutoff frequency as high as fT = 102 GHz, which is the highest value reported so far for nitride-based devices on silicon substrates, as well as for any AlInN/GaN-based HEMT regardless of substrate type. Continuous-wave power measurements in class-A operation at 10 GHz with VDS = 15 V revealed a 19-dB linear gain, a maximum output power density of 2.5 W/mm with an ~23% power-added efficiency (PAE), and a 9-dB large-signal gain. At VDS = 8 V, the output power is 1 W/mm, and the peak PAE reaches 50%. Results demonstrate the interest of AlInN/GaN on silicon HEMT technology for low-cost millimeter-wave and high-power applications.

Improved Microwave Noise Performance by SiN Passivation in AlGaN/GaN HEMTs on Si

Effects of silicon nitride (SiN) surface passivation by plasma enhanced chemical vapor deposition (PECVD) on microwave noise characteristics of AlGaN/GaN HEMTs on high-resistivity silicon (HR-Si) substrate have been investigated. About 25% improvement in the minimum noise figure (NF min) (0.52 dB, from 2.03 dB to 1.51 dB) and 10% in the associate gain (G a) (1.0 dB, from 10.3 dB to 11.3 dB) were observed after passivation. The equivalent circuit parameters and noise source parameters (including channel noise coefficient (P), gate noise coefficient (R), and their correlation coefficient (C)) were extracted. P, R and C all increased after passivation and the increase of C contributes to the decrease of the noise figure. It was found that the improved microwave small signal and noise performance is mainly due to the increase of the intrinsic transconductance (g m0) and the decrease of the extrinsic source resistance (R s).

100 nm gate AlGaN/GaN HEMTs on silicon with f T =90 GHz

The realisation of 0.1 µm gate AlGaN/GaN high electron mobility transistors grown on high-resistivity silicon substrates is reported. A maximum current density of 750 mA/mm and an extrinsic transconductance of 225 mS/mm are achieved. The devices feature a record current gain cutoff frequency as high as fT=90 GHz, the highest value ever reported from a GaN-based device grown on a silicon substrate. The results demonstrate the great potential of GaN-on-silicon technology for low-cost millimetre-wave applications.

Electrical crosstalk in front-illuminated photodiode array with different guard ring designs for medical CT applications

Abstract This paper presents electrical crosstalk studies on front-illuminated photodiode arrays for medical computed tomography (CT) applications. Crosstalk is an important factor to the system noise and image quality. The electrical crosstalk depends on silicon substrate properties and photodiode structures. The photodiode samples employed in this paper are planar processed on high-resistivity n-type silicon substrate, resulting in a p+/n−/n+ diode structure. Two types of guard ring structures are designed and applied to the same geometry of two-dimensional photodiode arrays. One structure is an n guard ring in the gap area between pixels, and the other structure is an additional p+ guard ring around each pixel together with the n guard ring. A 10 μm light spot with wavelength of 525 nm is used to scan across the surface of the photodiode array in the electrical crosstalk measurements. The electrical currents of two neighbor pixels are measured and the results are compared between two guard ring designs. The design with the p+ guard ring structure gives better electrical crosstalk suppression. Moreover, the measurement results show much smaller influence on surrounding pixels with the p+ guard ring structure in the case of disconnected pixel. Besides the electrical crosstalk, the light sensitivity within the gap area is also discussed between two guard ring designs.

Monolithic pixel sensors in deep-submicron SOI technology with analog and digital pixels

This paper presents the design and test results of a prototype monolithic pixel sensor manufactured in deep-submicron fully depleted Silicon-On-Insulator (SOI) CMOS technology. In the SOI technology, a thin layer of integrated electronics is insulated from a (high-resistivity) silicon substrate by a buried oxide. Vias etched through the oxide allow to contact the substrate from the electronics layer, so that pixel implants can be created and a reverse bias can be applied. The prototype chip, manufactured in OKI 0.15 μ m SOI process, features both analog and digital pixels on a 10 μ m pitch. Results of tests performed with an infrared laser and 1.35 GeV electrons and a first assessment of the effect of ionising and non-ionising doses are discussed.

High-Performance 0.1-$\mu\hbox{m}$ Gate AlGaN/GaN HEMTs on Silicon With Low-Noise Figure at 20 GHz

The realization of high-performance 0.1-mum gate AlGaN/GaN high-electron mobility transistors (HEMTs) grown on high-resistivity silicon substrates is reported. Our devices feature cutoff frequencies as high as fT = 75 GHz and fMAX = 125 GHz, the highest values reported so far for AlGaN/GaN HEMTs on silicon. The microwave noise performance is competitive with results achieved on other substrate types, such as sapphire and silicon carbide, with a noise figure F = 1.2-1.3 dB and an associated gain Gass = 8.0-9.5 dB at 20 GHz. This performance demonstrates that GaN-on-silicon technology is a viable alternative for low-cost millimeter-wave applications.

RF Performance of a Commercial SOI Technology Transferred Onto a Passivated HR Silicon Substrate

In this paper, we investigate the impact of a passivation layer on the performance of a commercial high-resistivity (HR) SOI CMOS technology. The passivation layer consists of a 300-nm-thick polysilicon cover located directly below the buried oxide (BOX). Both passive and active devices are studied. It is demonstrated that substrate passivation completely suppresses substrate losses that are usually induced by parasitic surface conduction at the substrate/BOX interface in oxidized HR Si substrates. We also report no effect of the underlying polysilicon on the dc and RF behavior of MOSFETs devices. The results shown here strongly suggest that substrate passivation using polysilicon is a promising tool to eradicate substrate losses in HR SOI wafers, thereby increasing the performance of functional SOI logic and high-speed circuits.

High-performance PIN photodiodes on TMAH thinned silicon wafers

The electro-optical characteristics of PIN photodiodes fabricated on high-resistivity silicon substrates locally thinned by bulk micromachining techniques are discussed. Experimental results and numerical simulations demonstrate that devices fabricated by the proposed approach have leakage current, quantum efficiency and speed performance comparable to the best commercially available Si PIN photodiodes, with the additional advantage of possible back-side illumination, making them suitable for the implementation of two-dimensional arrays having a read-out electronic chip connected to the front-side.

Effect of a Guard-Ring on the Leakage Current in a Si-PIN X-Ray Detector for a Single Photon Counting Sensor

PIN diodes for digital X-ray detection as a single photon counting sensor were fabricated on a floating-zone (FZ) n-type (111), high resistivity (5-10 kΩcm) silicon substrates (500μm thickness). Its electrical properties such as the leakage current and the breakdown voltage were characterized. The size of pixels was 100μm×100μm. The p+ guard-ring was formed around the active area to reduce the leakage current. After the p+ active area and guard-ring were fabricated by the ion-implantation, the extrinsic-gettering on the wafer backside was performed to reduce the leakage current by n+ ion-implantation. PECVD oxide was deposited as an IMD layer on front side and then, metal lines were formed on both sides of wafers. The leakage current of detectors was significantly reduced with a guard-ring when compared with that without a guard ring. The leakage current showed the strong dependency on the gap distance between the active area and the guard ring. It was possible to achieve the leakage current lower than 0.2nA/cm2.

32‐GHz dual‐termination coupled CPW bandpass filter on HR‐SI

AbstractBandpass filter is an important device in portable communication and other RF systems. A dual‐termination coupled coplanar waveguide (CPW) bandpass filter (BPF) has been designed by HFSS. This dual‐termination coupled structure improves the coupling capacitances between the central metal and the matching transmission lines so that the insertion loss can be reduced. The filter has been fabricated on a high resistivity silicon substrate (ρ ≥ 1000 Ω cm) with 1 μm SiO2. It has −2.16‐dB low insertion loss at peak transmission of about 32 GHz. This filter shows good s‐parameter characteristics and it is attractive for RF ICs. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1705–1706, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23464

RF MEMS capacitive switch on semi-suspended CPW using low-loss high-resistivity silicon substrate

A high capacitive ratio RF MEMS switch, with low-actuation voltage is designed, fabricated and experimentally validated on high-resistivity silicon (HRS) substrate. Thanks to very good fabrication control of all steps and to the high dielectric constant of TiO2, a down/up capacitive ratio close to 200 is achieved with 8V pull-in. It is also demonstrated that, using a passivated-surface HRS and semi-suspended conductors on air, the microwave losses in the CPW line are as low as 0.1dB/mm at 20GHz. The reported RF MEMS shunt capacitor is expected to serve as core device for phase shifting applications in the 10–20GHz range, both for switching operations and as a variable capacitor in distributed MEMS transmission lines (DMTLs).

Surface Micromachined Microelectromechancial Ohmic Series Switch Using Thin-Film Piezoelectric Actuators

This paper presents results on a surface micromachined RF microelectromechanical switch that uses piezoelectric actuators. The switch uses solution chemistry-derived lead zirconate titanate thin films spun deposited onto a high-resistivity silicon substrate with coplanar waveguide transmission lines. Actuation voltages, applied via circuits independent of the RF circuitry, average less than 10 V, with switch operation demonstrated as low as 2 V. The series switch exhibits better than 20-dB isolation from dc up to 65 GHz and as large as 70 dB below 1 GHz. In the closed state, the switch has an insertion loss less than 1 dB up to 40 GHz, limited in this demonstration by substrate losses from the elastic layer used to stress control the piezoelectric actuators. Switching speeds for the different designs are in the range of 40-60 ms. Thermal sensitivity measurements show no change in isolation observed for temperatures up to 125degC. However, an increase in actuation voltage is required at elevated temperatures.

A Compact Semi-Lumped Coplanar Waveguide Low-Pass Filter Fabricated on High Resistivity Silicon Substrate

In this letter, the fabrication of a compact and high performance semi-lumped coplanar waveguide low-pass filter (CPW-LPF) on high resistivity silicon (HRS) substrate at millimeter wave is proposed. The design procedure and the equivalent circuit of the proposed semi-lumped CPW-LPF is discussed. The filter structure of is very simple but its performances is fairly good. This designed filter at cutoff frequency f c of 31 GHz has very good measured characteristics including the low insertion loss, sharp rejection and low group delay, due to the reduced substrate loss of HRS. Experimental results of the fabricated filter show a good agreement with the predicted results.

Performance improvement of a vibration-powered electromagnetic generator by reduced silicon surface roughness

This paper reports on a chemical polishing process suitable for p-type medium to high resistivity (17–33 Ωcm) silicon substrates. The chemical polishing process using an HNA solution of ratio 27:43:30 (hydrofluoric, fuming nitric, and acetic acids respectively). The process has been applied to the fabrication of a micromachined electromagnetic generator to reduce the sidewall surface roughness of the device after Deep Reactive Ion Etching (DRIE). The microgenerator converts external ambient vibration into electrical energy by electromagnetic transduction. Power output is limited by the maximum amplitude of movement which is in turn limited by the fracture strength of the etched silicon. By applying the polishing etch to the devices, the mechanical strength of the silicon structures increased from 2 N to 5.5 N (∼175% increase).

Shielded-Loop-Type Onchip Magnetic-Field Probe to Evaluate Radiated Emission From Thin-Film Noise Suppressor

A silicon integrated RF magnetic field probe has been designed and microfabricated using CMOS-silicon-on-insulator (SOI) technology with a 0.15-mum design rule on a high-resistivity silicon substrate. The size of the coil window was 180times180 mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Coil and electrodes were separated by a 530-mum-long stripline so as to avoid stray voltage induction at the electrode portion. This probe was applied to evaluate the radiated emission from a thin-film electromagnetic noise suppressor. It was clarified and shown that the field intensity was suppressed by 4.0 dB at the center of the signal line at 1 GHz