A. Cagri Ulusoy

Packaging a

This paper, for the first time, presents successful integration of a W-band antenna with an organically flip-chip packaged silicon-germanium (SiGe) low-noise amplifier (LNA). The successful integration requires an optimized flip-chip interconnect. The interconnect performance was optimized by modeling and characterizing the flip-chip transition on a low-loss liquid crystal polymer organic substrate. When the loss of coplanar waveguide (CPW) lines is included, an insertion loss of 0.6 dB per flip-chip-interconnect is measured. If the loss of CPW lines is de-embedded, 0.25 dB of insertion loss is observed. This kind of low-loss flip-chip interconnect is essential for good performance of W-band modules. The module, which we present in this paper, consists of an end-fire Yagi-Uda antenna integrated with an SiGe BiCMOS LNA. The module is 3 mm × 1.9 mm and consumes only 19.2 mW of dc power. We present passive and active E- and H-plane radiation pattern measurements at 87, 90, and 94 GHz. Passive and active antennas both showed a 10-dB bandwidth of 10 GHz. The peak gain of passive and active antennas was 5.2 dBi at 90 GHz and 21.2 dBi at 93 GHz, respectively. The measurements match well with the simulated results.

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A single-pole double-throw switch, utilizing double-shunt, deep-saturated HBTs is implemented in a 0.13 μm SiGe BiCMOS technology, occupying 0.36 mm2 of IC area. A superior switch performance is identified when HBTs are operated in saturation regime, and state of the art performance is achieved at D-band frequencies from 96 to 163 GHz. Measurements show a minimum insertion loss of 2.6 dB at 120 and 150 GHz, a highest isolation of 29 dB at 120 GHz and an input 1 dB compression point of 17 dBm at 94 GHz, outperforming similar implementations in deep-scaled CMOS technologies.

-Band Integrated Module With an Optimized Flip-Chip Interconnect on an Organic Substrate

In this paper, for the first time, characterization of planar transmission lines on organic Liquid Crystal Polymer (LCP) substrate in D-Band is presented. Via-less conductor backed co-planar wave guide (CB-CPW) and microstrip lines are designed, fabricated and measured on 2 mil organic LCP substrate. Line-reflect-reflect-match (LRRM) calibration technique was used to measure the fabricated lines, whereas in order to accurately extract line loss and to characterize the substrate, a thru-reflect-line (TRL) calibration was performed. The results have shown excellent RF performance of LCP in the D-band, while the microstrip line exhibits a loss of 0.1755 dB/mm at 110 GHz, with a monotonous increase to 0.331dB/mm at 170 GHz. An almost constant (~2.6) effective dielectric constant is also reported within the whole measurement band.

A Low-Loss and High Isolation D-Band SPDT Switch Utilizing Deep-Saturated SiGe HBTs

A W-band power amplifier with Class-E tuning in a 0.13 μm SiGe BiCMOS technology is presented. Voltage swing beyond BVCBO is enabled by the cascode topology, low upper base resistance, and minimally overlapping current-voltage waveforms. At 93 GHz with 4.0 V bias, the peak power-added efficiency and saturated output power are measured to be 40.4% and 17.7 dBm, respectively. With the bias increased to 5.2 V, the peak power-added efficiency and saturated output power at 93 GHz are measured to be 37.6% and 19.3 dBm, respectively.

D-Band characterization of co-planar wave guide and microstrip transmission lines on liquid crystal polymer

Liquid crystal polymer is a promising substrate for mm-wave packaging. In this work, we present the characterization of liquid crystal polymer from 110 GHz to 170 GHz. The microstrip ring resonator method is used for the relative permittivity and loss tangent extraction at mm-wave frequencies. The effect of radiation loss in the extraction of loss tangent is analyzed through full electromagnetic 3D models to verify that radiation loss can be neglected for the particular geometry under study. The Monte Carlo uncertainty analysis is used to analyze the uncertainty of the method taking into account the uncertainty of each measurement involved in the characterization. Using a frequency dispersive model for the effective permittivity for the microstrip, the relative permittivity of LCP is extracted to be 3.17 and the loss tangent varies from 0.0055 to 0.009. This work is the first to characterize the liquid crystal polymer in D-band.

A Class-E Tuned W-Band SiGe Power Amplifier With 40.4% Power-Added Efficiency at 93 GHz

The design of a radiation-efficient D-band end-fire on-chip antenna utilizing a localized back-side etching (LBE) technique, as well as an antenna-in-package (AiP) on a low-cost organic substrate, is presented. Quasi-Yagi-Uda antennas are chosen for end-fire radiation because of their compact size. The on-chip antenna is realized in the back-end of the line (BEOL) process of a 130-nm SiGe BiCMOS technology, whereas the in-package antenna is realized in liquid crystal polymer (LCP) technology for comparison. The on-chip antenna design is optimized to meet both process reliability specifications and radiation performance, and corresponding design guidelines are provided. The fabricated on-chip antennas show the state-of-the-art performance with a peak gain of 4.7 dBi, simulated radiation efficiency of 82%, and measured radiation efficiency of 72%-76% using the gain/directivity (G/D) and wheeler-cap methods at 143 GHz. The antenna demonstrates a 3-dB gain bandwidth of more than 30 GHz and 10-dB impedance bandwidth greater than 20 GHz (14% impedance bandwidth). The measurements of the on-package end-fire antenna showed very comparable results with a peak measured gain of 6 dBi and a simulated and measured radiation efficiency of 92% and 86% at 143 GHz. These results demonstrate that highly efficient on-chip end-fire antenna implementation is possible in standard commercially available BiCMOS process.

Characterization of liquid crystal polymer from 110 GHz to 170 GHz

Gallium nitride (GaN) technology has emerged as a frontrunner for high power electronics applications. By performing a survey of wire-bond and flip-chip-packaged GaN HEMTs on either AlN (a ceramic with high thermal conductivity) or LCP (an organic polymer with low thermal conductivity), the thermal and electrical limits of each package are established. Flip-chip packaging has the benefit of improving the bandwidth of a hybrid PA. Dies that were wire-bonded on AlN showed best performance, and were able to dissipate more than 6 W of power while remaining below the maximum operating junction temperature. On the other hand, flip-chipped devices on LCP were severely limited by thermal effects, even at a 10% duty cycle. This study motivates the need for advanced packaging techniques, such as integrated microfluidics or backside heat-sinking, in order to make LCP a viable material for high-power applications.

A D-Band Micromachined End-Fire Antenna in 130-nm SiGe BiCMOS Technology

An ultra-wideband PA using a single GaN die with resistive and reactive matching is fabricated and measured. The design includes series and shunt elements at the gate for stability and gain compensation, and uses two different substrates to obtain optimum Z 0 ranges for the matching networks. CW measurements at 31 dBm source power show 27-48% PAE and 35.1-37.4 dBm output power from 1.0 to 11.5 GHz (168% relative bandwidth). These results demonstrate multi-watt output power and high PAE over a decade bandwidth, achieving the best results in this frequency range for a hybrid implementation.

A feasibility study of flip-chip packaged gallium nitride HEMTs on organic substrates for wideband RF amplifier applications

This paper, for the first time, presents the characterization of a very wide-band flip-chip interconnect from DC to 170 GHz on a liquid crystal polymer substrate. The performance is optimized by modeling the structure in a 3-D electromagnetic simulation software. To mitigate the influence of the capacitive effect caused by the flip-chip overlap section, high impedance inductive sections are used. The measured return loss is more than 10 dB, while the insertion loss is less than 0.9 dB/mm for the transmission line and the interconnect across the entire frequency range. The measurements correlate well with simulated results.

A Reactively Matched 1.0–11.5 GHz Hybrid Packaged GaN High Power Amplifier

In this paper, the authors present an embedded, low-cost packaging technique for high power gallium nitride devices. The package is based on flip-chip bonding to achieve a reduced parasitic inductance, easing the design for wideband amplifiers. The backside of the gallium nitride devices is connected to a heat sink by a second flip-chip process to improve thermal management. When realized on a low-cost organic substrate material with poor thermal characteristics, measurement results show that the proposed packaging technique can still achieve performance levels comparable to devices packaged on expensive, high thermal conductivity substrate materials, such as aluminum nitride. These results demonstrate a low-cost, high-performance and near-hermetically sealed packaging solution for gallium nitride devices.