IEEE International Solid-State Circuits Conference

The discovery of ferroelectricity in oxides that are compatible with modern semiconductor manufacturing processes, such as hafnium oxide, has led to a re-emergence of the ferroelectric field-effect transistor in advanced microelectronics. A ferroelectric field-effect transistor combines a ferroelectric material with a semiconductor in a transistor structure. In doing so, it merges logic and memory functionalities at the single-device level, delivering some of the most pressing hardware-level demands for emerging computing paradigms. Here, we examine the potential of the ferroelectric field-effect transistor technologies in current embedded non-volatile memory applications and future in-memory, biomimetic and alternative computing models. We highlight the material- and device-level challenges involved in high-volume manufacturing in advanced technology nodes (≤10 nm), which are reminiscent of those encountered in the early days of high-K-metal-gate transistor development. We argue that the ferroelectric field-effect transistors can be a key hardware component in the future of computing, providing a new approach to electronics that we term ferroelectronics. This Perspective examines the use of ferroelectric field-effect transistor technologies in current embedded non-volatile memory applications and future in-memory, biomimetic and alternative computing models, arguing that the devices will be a key component in the development of data-centric computing.

The future of ferroelectric field-effect transistor technology

Energy harvesting has been widely investigated as a promising method of providing power for ultra-low-power applications. Such energy sources include solar energy, radio-frequency (RF) radiation, piezoelectricity, thermal gradients, etc. However, the power supplied by these sources is highly unreliable and dependent upon ambient environment factors. Hence, it is necessary to develop specialized systems that are tolerant to this power variation, and also capable of making forward progress on the computation tasks. The simulation platform in this paper is calibrated using measured results from a fabricated nonvolatile processor and used to explore the design space for a nonvolatile processor with different architectures, different input power sources, and policies for maximizing forward progress.

Architecture exploration for ambient energy harvesting nonvolatile processors

This expanded and thoroughly revised edition of Thomas H. Lee's acclaimed guide to the design of gigahertz RF integrated circuits features a completely new chapter on the principles of wireless systems. The chapters on low-noise amplifiers, oscillators and phase noise have been significantly expanded as well. The chapter on architectures now contains several examples of complete chip designs that bring together all the various theoretical and practical elements involved in producing a prototype chip. First Edition Hb (1998): 0-521-63061-4 First Edition Pb (1998); 0-521-63922-0

The Design of CMOS Radio-Frequency Integrated Circuits: RF CIRCUITS THROUGH THE AGES

Energy harvesters are being used to power autonomous systems, but their output power is variable and intermittent. To sustain computation, these systems integrate batteries or supercapacitors to smooth out rapid changes in harvester output. Energy storage devices require time for charging and increase the size, mass, and cost of systems. The field of transient computing moves away from this approach, by powering the system directly from the harvester output. To prevent an application from having to restart computation after a power outage, approaches such as Hibernus allow these systems to hibernate when supply failure is imminent. When the supply reaches the operating threshold, the last saved state is restored and the operation is continued from the point it was interrupted. This paper proposes Hibernus++ to intelligently adapt the hibernate and restore thresholds in response to source dynamics and system load properties. Specifically, capabilities are built into the system to autonomously characterize the hardware platform and its performance during hibernation in order to set the hibernation threshold at a point which minimizes wasted energy and maximizes computation time. Similarly, the system auto-calibrates the restore threshold depending on the balance of energy supply and consumption in order to maximize computation time. Hibernus++ is validated both theoretically and experimentally on microcontroller hardware using both synthesized and real energy harvesters. Results show that Hibernus++ provides an average 16% reduction in energy consumption and an improvement of 17% in application execution time over state-of-the-art approaches.

/pdf/hibernus-a-self-calibrating-and-adaptive-system-for-4xi0hmahws.pdf

Hibernus++: A Self-Calibrating and Adaptive System for Transiently-Powered Embedded Devices

Nonvolatile processors offer a number of desirable properties including instant on/off, zero standby power and resilience to power failures. This paper presents a fabricated nonvolatile processor based on ferroelectric flip-flops. These flipflops are used in a distributed fashion and are able to maintain system states without any power supply indefinitely. An efficient controller is employed to achieve parallel reads and writes to the flip-flops. A reconfigurable voltage detection system is designed for automatic system backup during power failures. Measurement results show that this nonvolatile processor can operate continuously even under power failures occurring at 20 KHz. It can backup system states within 7μs and restore them within 3 μs. Such capabilities will provide a new level of support to chip-level fine-grained power management and energy harvesting applications.

A 3us wake-up time nonvolatile processor based on ferroelectric flip-flops

For implantable devices, miniaturization is a key design consideration, which facilitates keyhole surgery and relieves the surgical pain. Wireless power transfer is a commonly used way for implants, and a high power transfer efficiency (PTE) could help to minimize or even remove the battery inside the human body. Conventionally, the required power is delivered transcutaneously to a medical implant by inductive coupling or capacitive coupling, but the PTE is extremely low when targeting at a very small implant through a thick tissue layer. In this paper, we propose a new technique by utilizing the body tissue as the power transfer channel, where a pair of medical electrodes are attached on the body surface to supply power to a miniaturized implant with a differential input. The PTE is remarkably improved by the current loop through the body tissue without violating the IEEE specific absorption rate standard. Measurement results show that the tissue-channel technique achieves 0.39% PTE for a 1-mm-sized implant locating 5 cm deep inside the tissue.

A Tissue-Channel Transcutaneous Power Transfer Technique for Implantable Devices

This paper presents a low-power fast-settling phase-locked loop (PLL) frequency synthesizer working at 172–174 GHz for a 100 kb/s Gaussian frequency shift keying (GFSK) based transceiver suitable for wireless sensor network (WSN) applications We propose several new techniques for lowering the power consumption in the frequency synthesizer Resistor-based electro-static discharge protection (ESD-P) and automatic frequency calibration (AFC) are introduced to the bond-wire voltage-controlled oscillator (VCO) to deal with the inaccuracy of bond-wire inductors and uncertain parasitics A multi-stage power-scaling scheme is developed for classical phase-switching prescaler A dynamic-bandwidth scheme is proposed to speed up the settling time and improve the energy efficiency in a time-division WSN system Implemented in 018 $\mu{\hbox {m}}$ CMOS technology, the measurement results show that the PLL consumes 106 mW under 18 V supply voltage and settles within 18 $\mu{\hbox {s}}$ including the AFC process The phase noise is $-$ 898 dBc/Hz@10 kHz and $-$ 1193 dBc/Hz@1 MHz under receiving (Rx) mode; from receiving (Rx) state to transmitting (Tx) state, the out-band fractional- $N$ phase noise is increased by 27 dB, whereas the in-band noise is lowered by 21 dB

A Low-Power Fast-Settling Bond-Wire Frequency Synthesizer With a Dynamic-Bandwidth Scheme

Flexible electronics are compatible with film substrates that are soft and stretchable, resulting in conformal integration with human body. Integrated with various sensors and communication ICs, wearable flexible electronics are able to effectively track human vital signs without affecting the body activities. Such a wearable flexible system contains a sensor, a front-end amplifier (FEA), an analog-to-digital converter (ADC), a micro-controller unit (MCU), a radio, a power management unit (PMU), where the radio is the design bottleneck due to its high power consumption. Different from conventional wireless communications, body channel communication (BCC) uses the human body surface as the signal transmission medium resulting in less signal loss and low power consumption. However, there are some design challenges in BCC, including body channel model, backward loss, variable contact impedance, stringent spectral mask, crystalless design, body antenna effect, etc. In this paper, we conduct a survey on BCC transceiver, and analyze its potential role and challenges in wearable flexible electronics.

The Role and Challenges of Body Channel Communication in Wearable Flexible Electronics

In wireless body area network, capacitive-coupling body channel communication (CC-BCC) has the potential to attain better energy efficiency over conventional wireless communication schemes. The CC-BCC scheme utilizes the human body as the forward signal transmission medium, reducing the path loss in wireless body-centric communications. However, the backward path is formed by the coupling capacitance between the ground electrodes (GEs) of transmitter (Tx) and receiver (Rx), which increases the path loss and results in a body posture dependent backward impedance. Conventional methods use a fixed inductor to resonate with the backward capacitor to compensate the path loss, while it's not effective in compensating the variable backward impedance induced by the body movements. In this paper, we propose a self-adaptive capacitive compensation (SACC) technique to address such a problem. A backward distance detector is introduced to estimate the distance between two GEs of Tx and Rx, and a backward capacitance model is built to calculate the backward capacitance. The calculated backward capacitance at varying body posture is compensated by a digitally controlled tunable inductor (DCTI). The proposed SACC technique is validated by a prototype CC-BCC system, and measurements are taken on human subjects. The measurement results show that 9dB–16 dB channel enhancement can be achieved at a backward path distance of 1 cm-10 cm.

Bo Zhao

Papers

A 3us wake-up time nonvolatile processor based on ferroelectric flip-flops

A Tissue-Channel Transcutaneous Power Transfer Technique for Implantable Devices

A Low-Power Fast-Settling Bond-Wire Frequency Synthesizer With a Dynamic-Bandwidth Scheme

The Role and Challenges of Body Channel Communication in Wearable Flexible Electronics

A Self-Adaptive Capacitive Compensation Technique for Body Channel Communication