Story
October 16, 2023
Monolithic microwave built-in circuits (MMICs) fabricated utilizing compound semiconductors are a essential element of a mess of RF [radio-frequency] methods. For business wi-fi functions, gallium arsenide (GaAs)-based energy amplifiers are ubiquitous within the smartphone market, whereas gallium nitride (GaN) merchandise service wi-fi base stations, SATCOM terminals, and are a core enabler of 5G methods.
Protection methods for radar, missile seekers, digital warfare (EW), and communications depend upon monolithic microwave built-in circuits (MMIC) merchandise to acquire efficiency that’s not achievable with silicon-based electronics alone. With the intention to obtain demanding efficiency necessities, the protection trade leverages superior gadgets based mostly on excessive electron mobility transistors (HEMTs). These gadgets supply one of the best mixture of high-frequency operation, low noise, excessive linearity, and excessive output energy density of any semiconductor expertise.
GaAs [gallium arsenide] HEMT merchandise emerged within the Eighties and Nineteen Nineties, and at the moment are properly established in RF methods, whereas GaN [gallium nitride] HEMTs are a more recent expertise whose use is quickly increasing. Designers could need to contemplate GaN as a result of the transistors produce roughly 5 occasions the ability density than the incumbent GaAs gadgets. (Determine 1.)
[Figure 1 ǀ GaN [gallium nitride] transistors produce roughly 5 occasions the ability density in contrast with GaAs [gallium arsenide] gadgets.]
This side of GaN now signifies that solid-state energy amplifiers (SSPAs) based mostly on GaN MMICs are changing legacy touring wave tube amplifiers in lots of radar and EW methods. Each GaAs and GaN applied sciences are pushing in direction of superior course of nodes with larger working frequencies and better efficiencies in an effort to obtain higher efficiency and allow dominance over a broader vary of the RF spectrum.
The BAE Programs Microelectronics Middle (MEC) is a U.S. Division of Protection (DoD) trusted foundry situated in Nashua, New Hampshire, devoted to producing customized GaAs and GaN circuits. The 70,000-square-foot MEC facility consists of the wafer foundry, on-wafer RF testing, wafer dicing, inspection, put up processing, microwave module prototyping facility, and manufacturing manufacturing unit for microwave energy amplifier modules that use GaN MMICs.
One distinctive side of the foundry is the 6-inch wafer line, which provides larger product yield and decrease chip price in comparison with the trade customary 4-inch wafer diameter. The MEC’s 6-inch wafer processing line has been operating manufacturing GaAs processes since 2004, and BAE Programs’ first six-inch GaN MMIC was reported in 2014.
In testing, 6-inch GaN wafer processes demonstrated excessive yield, and glorious efficiency and reliability, with an MTTF [mean time to failure] of greater than 107 hours at 200 °C channel temperature.
In progress on the MEC is a “Foundry Modernization Initiative,” a multiyear project so as to add wafer capability to the ability, enabling it to maintain tempo with the rising demand inside the DoD and trade for superior RF MMIC elements.
The workhorse manufacturing GaN course of in the present day is a 180 nm “no area plate” expertise that targets broadband EW functions as much as 20 GHz. In 2018, the corporate signed a cooperative settlement with Air Pressure Analysis Laboratory (AFRL) to switch a complicated, high-performance 140 nm GaN course of developed by AFRL’s analysis fabrication facility to BAE’s production-focused foundry. This new course of with shorter gate size and enahnced transistor efficiency targets functions at mm-wave frequencies as much as 50 GHz.
By means of this “lab-to-fab” collaboration mannequin, BAE Programs was efficiently capable of transition the method, and show state-of-the-art efficiency on the 6-inch manufacturing line. The 140 nm GaN expertise – which will probably be totally certified for manufacturing in 2023 – represents the DoD’s solely 6-inch course of at this superior expertise node.
Much more superior GaAs and GaN MMIC applied sciences are on the horizon: BAE Programs’ R&D group, FAST Labs, acts as a trusted companion with authorities R&D organizations and continues to drive in direction of higher-performance course of nodes. The subsequent GaAs expertise has a 70 nm gate size and targets low-noise functions as much as 100 GHz the place low noise determine, excessive linearity, and low DC energy consumption are essential efficiency parameters.
This expertise is the shortest gate size GaAs pseudomorphic HEMT course of in the marketplace, and is a wonderful various to InP [indium phosphide] HEMT applied sciences due to the low manufacturing price on 6-inch wafer diameter. BAE Programs has already delivered prototype portions of chips utilizing this course of, and it’s scheduled to be totally certified by 2024.
The subsequent GaN expertise underneath growth is a 90 nm HEMT course of that leverages superior course of options together with T-gates and low-resistance ohmic contacts fabricated utilizing n+ GaN regrowth by molecular beam epitaxy (MBE). This course of primarily targets energy amplifier functions at W-band frequencies (75 to 110 GHz); W-band frequencies embody an area minima within the atmospheric absorption spectra, so it’s anticipated that this portion of the electromagnetic spectrum will probably be exploited by radars, missile seekers, SAR [synthetic aperture radar] imaging, E-band radio, and 6G functions.
The proliferation of RF elements at this frequency band within the close to time period will drive the DoD to hunt entry to one of the best high-frequency GaN expertise in an effort to keep dominance over the electromagnetic spectrum. Along with high-frequency energy amplifiers, 90 nm GaN additionally is beneficial as an ultrahigh linearity mm wave LNA [low-noise amplifier] or inside a monolithic, mm wave transceiver chip.
Dr. David F. Brown is at present the product lead at BAE Programs Inc. for RF MMIC and solid-state amplifier applied sciences.
BAE Programs https://www.baesystems.com/en/dwelling
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