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Integrated circuits (ICs) are generally classified as digital (e.g. a microprocessor) or analog (e.g. an operational amplifier). Mixed-signal ICs are chips that contain both digital and analog circuits on a single semiconductor die. Mixed-signal ICs also process both analog and digital signals together. For example, an analog-to-digital converter is a mixed-signal circuit.
Mixed-signal circuits or systems are typically cost-effective solutions for building any modern consumer electronics applications. An analog-mixed-signal system-on-a-chip (AMS-SoC) can be a combination of analog circuits, digital circuits, intrinsic mixed-signal circuits (like ADC), and embedded software. This category of chip has grown dramatically with the increased use of 5G cell phones and other portable technologies. In real-life applications mixed-signal designs are everywhere, for example, smart mobile phones.
Mixed-signal ICs are more difficult to design and manufacture than analog-only or digital-only integrated circuits. For example, an efficient mixed-signal IC would have its digital and analog components share a common power supply. However, analog and digital components have very different power needs and consumption characteristics that make this a non-trivial goal in chip design.
CMOS technology is usually optimal for digital performance and scaling while bipolar transistors are usually optimal for analog performance, yet until the last decade it has been difficult to either combine these cost-effectively or to design both analog and digital in a single technology without serious performance compromises. The advent of technologies like high performance CMOS, BiCMOS, CMOS SOI and SiGe have removed many of the compromises that previously had to be made.
The DoD has capability demands that far exceed the requirements of the commercial world in terms of speed, fidelity, capacity, and precision. These characteristics directly impact the performance and differentiation on essentially all DoD electronic systems in advanced RF sensors and high capacity communications.
Recognizing that the DoD has performance demands that far exceed the capabilities of the commercial world in terms of speed, fidelity, capacity, and precision, DARPA created the Technologies for Mixed mode Ultra Scaled Integrated Circuits (T-MUSIC) program to enable disruptive radio frequency (RF) mixed-mode technologies by developing high performance RF analog electronics integrated with advanced digital electronics on the same wafer.
To create unique and differentiated domestic manufacturing capabilities, potential areas of exploration in ERI Phase II include the integration of photonics and radiofrequency (RF) components directly into advanced circuits and semiconductor manufacturing processes. DARPA announced the Photonics in the Package for Extreme Scalability (PIPES) and Technologies for Mixed-mode Ultra Scaled Integrated Circuits (T-MUSIC) within this area.
Defense Advanced Research Projects Agency (DARPA) announced the Electronics Resurgence Initiative (ERI), in June 2017, a five-year, upwards of $1.5B investment in the future of domestic, U.S. Government (USG), and Department of Defense (DoD) electronic systems. ERI recognizes and addresses long-foreseen obstacles to Moore’s Law – the transistor scaling trend that has allowed for 50 years of rapid progress in electronics.
To address these issues, ERI kicked off a major investment that draws on the contributions of several ongoing DARPA programs and creates new, long-term technology investments. Through novel research and development (R&D) in semiconductor materials and integration, architectures, and designs, ERI programs will promote circuit specialization as a complement to transistor scaling. The success of these efforts will depend on constructively enmeshing the technology needs and capabilities of the defense enterprise with the commercial and manufacturing realities of the electronics industry.
Technologies for Mixed-mode Ultra Scaled Integrated Circuits (T-MUSIC) program
The Microsystems Technology Office at DARPA seeks innovative proposals to develop integrated, ultra-broadband, mixed-mode electronics with embedded advanced digital CMOS (Complementary Metal-Oxide-Semiconductor) electronics in a U.S. domestic foundry fabrication platform.
RF mixed-mode electronics form the critical frontend interface used to convert analog wireless signals to a digital representation and vice versa. Frontend performance directly impacts overall system capabilities such as the detection sensitivity, range, signal discrimination, and operating frequency coverage. These system parameters impact virtually all DoD electronic systems including communications, radar, signals intelligence (SIGINT), and electronic warfare (EW).
Current commercial RF mixed-mode systems on a chip (SoCs) are implemented on a digital CMOS platform for wireless applications, which operate at low microwave bands. The capability to operate at higher frequency with larger signal bandwidth and higher resolution is currently constrained by the performance of the existing CMOS technology platforms.
Following the trend of Moore’s Law over the past five decades, digital CMOS scaling has focused on increasing integration density to process high computing workloads in a single chip. This successful scaling has been achieved by reducing the size and power consumption of the underlying transistors. However, scaled digital CMOS transistors can no longer support the high switching speed and voltage required to convert fast analog signals in fine resolution over a large dynamic range and wide operating frequency.
The resulting technology bottlenecks restrict many DoD applications in operating frequencies, signaling bandwidth, fidelity, detection sensitivity, and energy efficiency. To fully advance the RF mixed-mode interface, new innovations in integrated microelectronics are needed to move beyond the traditional progression of Moore’s Law scaling in digital CMOS technologies.
To integrate mixed mode electronics into advanced onshore semiconductor manufacturing processes in ERI Phase II, the Technologies for Mixed mode Ultra Scaled Integrated Circuits (TMUSIC) program will advance the underlying technology for RF transistors and circuits in CMOS and SiGe that has been left behind by traditional digital CMOS scaling.
T-MUSIC will also provide an advantage for US-based foundries as leading suppliers of commercial wireless system-on-a-chip (SoC) integrated circuits. T-MUSIC will provide the foundation for enduring U.S. leadership in mixed-mode electronics technology by further developing next generation THz (terahertz) mixed-mode devices designed for integration with an advanced CMOS fabrication platform. This is expected to greatly enhance Department of Defense (DoD) capabilities in advanced RF sensors and high capacity communications.
This advanced analog radio frequency (RF) mixed-mode electronics platform would provide ultra-wide instantaneous bandwidth, higher spur-free dynamic range (SFDR), and finer data converter resolution with more effective number of bits (ENOB) than the current state of the art.
Through the T-MUSIC program, DARPA seeks to: 1) advance RF and mixed-mode devices to support ultra wide RF frontends from HF to 100 GHz; 2) integrate those devices with high density digital CMOS electronics at the wafer scale to enable embedded digital intelligence; 3) develop and explore ultra-high resolution broadband mixed-mode circuit building blocks for DoD-relevant applications; 4) explore innovative device topologies and materials to implement THz devices in an advanced digital CMOS fabrication platform; and 5) establish a domestic ecosystem that facilitates enduring DoD access to differentiated capabilities for high performance RF mixed-mode SoCs.
Improvements in key transistor performance parameters such as current-gain and maximum power-gain cutoff frequencies (fT and fmax) as well as intrinsic noise produce measurable performance enhancement at the SoC and system level. T-MUSIC seeks proposals to integrate high frequency, low noise electronics, such as heterojunction bipolar transistors (HBTs), with high density CMOS onto a wafer. Such an effort would leverage prior investments in digital CMOS processes and tool sets in U.S. onshore foundries. For example, by aggressively scaling in the lateral and vertical dimensions in SiGe HBTs, speed can be increased to over 500 GHz of fT. Furthermore, the speed and RF performance of co-integrated digital CMOS could be concurrently enhanced using silicon-on-insulator (SOI) structures to reduce interconnect parasitics and RF leakage.
The incorporation of embedded digital CMOS electronics, with an end goal of an advanced 22 nm or smaller processes, will result in highly integrated digital processing and intelligence on one chip to provide differentiating capabilities for DoD systems. T-MUSIC foundry performers will provide multiple project wafers (MPWs) with engineering process design kits (PDKs) to circuit design partners to identify optimal device topologies for critical RF mixed-mode circuit functions for future DoD applications.
Program Structure
The T-MUSIC program is a four-year effort beginning in FY19 and ending in FY23. It will have an 18-month Phase 1, 18-month Phase 2, and 12-month Phase 3. The program will have three technical areas (TA-1A, TA-1B and TA-2) that will run concurrently. The program seeks to develop wafer-scale technology on a silicon CMOS-based foundry platform.
TA-1A: Ultra-broadband Mixed-Mode Foundry Technology
The TA-1A technical area will develop advanced mixed-mode technologies with high speed low noise RF analog transistors co-integrated at wafer scale with embedded advanced digital CMOS electronics (≤ 22 nm) on the same wafer in a U.S. onshore foundry.
TA-1B: Ultra-broadband Mixed-Mode Building Blocks
TA-1B is a design-focused technical area that is tightly coupled with TA-1A. TA-1B will implement advanced broadband RF mixed-mode building blocks while assisting with the codevelopment of the TA-1A foundry technologies through iterative engineering multi-project wafer (MPW) runs provided by the TA-1A team(s). The goal of this partnership is to align the TA-1A process technology with emerging and best-practice design techniques to provide superior performance of TA-1B mixed-mode building blocks for DoD-relevant applications. The advanced mixed-mode IP designs will establish the foundation of a mixed-mode IP library repository for the DoD user community
TA-2: Advanced THz Mixed-Mode Devices
TA-2 has a more fundamental focus in which new types of RF mixed-mode transistors will be explored to demonstrate transistor fT up to 1 THz in a scalable CMOS platform.
Through TA-2, T-MUSIC also seeks foundational breakthrough research in ultra-broadband transistors well beyond the near-term advances in foundry technologies. The program will demonstrate THz transistors with novel device topologies and materials by exploiting advanced nano-scale digital CMOS processing platforms. Simulations of these highly scaled devices indicate THz transistor speed can be attained using processes in an advanced silicon CMOS platform. The scalability in integration density and circuit performance of the THz devices shall be demonstrated in high speed digital divider circuits at input frequency up to 400 GHz by the end of the program. TA-2 teams will perform independent research and development and, as such, ACAs with other T-MUSIC teams will not be required.
DARPA Awards
The first phase of the T-MUSIC project involved BAE Systems, and four other research teams led by Raytheon Technologies Corp.; University of California-Los Angeles; University of California-San Diego; and University of Utah.
The five circuit design teams worked close with two foundry partners selected to support the development of advanced mixed-mode technologies in U.S. onshore CMOS foundries. The foundry partners are Global Foundries in Santa Clara, Calif., and Tower Semiconductor in Migdal HaEmek, Israel.
DARPA Selects BAE Systems to Build Powerful Next-Generation Advanced Electronics
BAE Systems was awarded a contract from the Defense Advanced Research Projects Agency (DARPA) to develop the next generation of mixed-signal electronics that could enable new Department of Defense (DoD) applications including high capacity, robust communications, radars, and precision sensors, and lead to solutions that enhance situational awareness and survivability for the warfighter.
The next-generation capabilities that could be made possible with this program include a combination of wide spectral coverage, high resolution, large dynamic range, and high information processing bandwidth. These capabilities, which can cut through the electronic signal clutter, provide leap-forward performance that is mission critical as services rely on electronic sensors in highly congested environments. The new developments could be integrated into electronic warfare, communications, precision munitions, and intelligence, surveillance and reconnaissance platforms.
“T-MUSIC will incorporate analog and digital signals on a single chip for high-performance data converters and digital processing and intelligence,” said Chris Rappa, product line director for Radio Frequency, Electronic Warfare, and Advanced Electronics at BAE Systems’ FAST Labs. “The advanced electronics we are developing under the T-MUSIC program could create the foundation for greatly enhanced Department of Defense capabilities in advanced RF sensors and high capacity communications.”
As part of the $8 million contract, BAE Systems FAST Labs™ research and development team – working closely with program foundries – will design and develop wafer-scale technology on a silicon foundry platform that can enable U.S.-based production of next-generation DoD electronics.
The T-MUSIC contract adds to BAE Systems’ advanced electronics portfolio and is based on many years of investment on various programs with the Air Force Research Lab (AFRL), U.S. Army, and DARPA, including DARPA’s CONverged Collaborative Elements for RF Task Operations (CONCERTO) and DARPA’s Radio Frequency Field Programmable Gate Arrays (RF-FPGA) programs.
T-MUSIC Second phase
In April 2022, Officials of the U.S. Defense Advanced Research Projects Agency (DARPA in Arlington, Va., awarded a $5 million contract to the BAE Systems Electronic Systems segment in Nashua, N.H., to start the second phase of the Technologies for Mixed-mode Ultra Scaled Integrated Circuits (T-MUSIC) program.
The second phase will refine enabling technologies for RF mixed-mode technologies by integrating RF analog electronics with digital electronics on the same wafer for future military communications, radar, and electronic warfare (EW) applications.
T-MUSIC technology could enable wide spectral coverage, high resolution, large dynamic range, and high information processing bandwidth. These capabilities can cut through electronic signal clutter.
A third group of researchers have explored foundational breakthroughs in ultra-broadband transistors, pushing well beyond current near-term advances in foundry technology. Research teams from the University of California-Los Angeles and University of California-Berkeley looked at new types of RF mixed-mode transistors to demonstrate transistor-switching speed to 1 GHz in scalable CMOS.
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