Oscilador CMOS controlado por temperatura

TCC(graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Engenharia Eletrônica.Neste projeto, é desenvolvido um oscilador controlado por temperatura com baixa dependência da tensão de alimentação. Para isso, uma fonte de corrente proporcional à temperatura absoluta (PTAT) foi projetada para alimentar um oscilador em anel. Como resultado, a frequência de oscilação é aproximadamente PTAT. Além disso, um circuito para inicializar a fonte de corrente em um curto período de tempo, um deslocador de nível para maior excursão do sinal oscilatório e, finalmente, um buffer para transferir o sinal oscilatório a uma sonda para medições foram projetados. Ferramentas da Cadence foram empregadas para o leiaute e extração de capacitâncias e resistências parasitas, visando a uma possível integração na tecnologia CMOS 0.18 μm. A frequência de oscilação é de 1 MHz a 40 °C, com sensibilidade à temperatura de 4000 ppm/°C e erro máximo de ±0.3 °C na faixa de 0 a 80 °C. O oscilador consome aproximadamente 1 μA (sem considerar o buffer), apresenta sensibilidade à fonte de alimentação de 1000 ppm/V para uma tensão de alimentação entre 1.6 V e 2 V. A área total é de 1500 μm².In this project, a temperature-controlled oscillator with a low frequency dependence on the power supply voltage is developed. For this, a proportional to absolute temperature (PTAT) current source was designed to feed a current-starved ring oscillator. As a result, the oscillation frequency is approximately PTAT. Additionally, a circuit for starting up the current source in a short period of time, a level shifter for increased excursion of the oscillatory signal and, finally, a buffer for carrying the oscillatory signal to a probe for measurements were designed. Cadence tools were employed for the layout and extraction of parasitic capacitances and resistances, aiming at a possible integration in 0.18 μm CMOS technology. The oscillation frequency is 1 MHz at 40 °C, with temperature sensitivity of 4000 ppm/°C and maximum error of ±0.3 °C in the range of 0 to 80 °C. The oscillator consumes approximately 1 μA (not considering the buffer), presents supply sensitivity of 1000 ppm/V for a supply voltage between 1.6 V to 2 V and a total area of 1500 μm²

High Aspect-ratio Biomimetic Hair-like Microstructure Arrays for MEMS Multi-Transducer Platform

Many emerging applications of sensing microsystems in health care, environment, security and transportation systems require improved sensitivity and selectivity, redundancy, robustness, increased dynamic range, as well as small size, low power and low cost. Providing all of these features in a system consisting of one sensor is not practical or possible. Micro electro mechanical microsystems (MEMS) that combine a large sensor array with signal processing circuits could provide these features. To build such multi-transducer microsystems we get inspiration from “hair”, a structure frequently used in nature. Hair is a simple yet elegant structure that offers many attractive features such as large length to cross-sectional area ratio, large exposed surface area, ability to include different sensing materials, and ability to interact with surrounding media in sophisticated ways. In this thesis, we have developed a microfabrication technology to build 3D biomimetic hair structures for MEMS multi-transducer platform. Direct integration with CMOS will enable signal processing of dense arrays of 100s or 1000s of MEMS transducers within a small chip area. We have developed a new device structure that mimics biological hair. It includes a vertical spring, a proof-mass atop the spring, and high aspect-ratio narrow electrostatic gaps to adjacent electrodes for sensing and actuation. Based on this structure, we have developed three generations of 3D high aspect-ratio, small-footprint, low-noise accelerometers. Arrays of both high-sensitivity capacitive and threshold accelerometers are designed and tested, and they demonstrate extended full-scale detection range and frequency bandwidth. The first-generation capacitive hair accelerometer arrays are based on Silicon-on-Glass (SOG) process utilizing 500 µm thick silicon, achieving a highest sensor density of ~100 sensors/mm2 connected in parallel. Minimum capacitive gap is 5 μm with device height of 400 μm and spring length of 300 μm. A custom-designed Bosch deep-reactive-etching (DRIE) process is developed to etch ultra-deep (> 500 µm) ultra-high aspect-ratio (UHAR) features (AR > 40) with straight sidewalls and reduced undercut across a wide range of feature sizes. A two-gap dry-release process is developed for the second-generation capacitive hair accelerometers. Due to the large device height at full wafer thickness of 1 mm and UHAR capacitive transduction gaps at 2 µm that extend > 200 µm, the accelerometer achieves sub-µg resolution (< 1µg/√Hz) and high sensitivity (1pF/g/mm2), having an area smaller than any previous precision accelerometers with similar performance. Each sensor chip consists of devices with various design parameter to cover a wide range. Bonding with metal interlayers at < 400 °C allows direct integration of these devices on top of CMOS circuits. The third-generation digital threshold hair accelerometer takes advantage of large aspect-ratio of the hair structure and UHAR DRIE structures to provide low noise (< 600 ng/√Hz per mm2 footprint proof-mass due to small contact area) and low power threshold acceleration detection. 16-element (4-bit) and 32-element (5-bit) arrays of threshold devices (total chip area being < 1 cm2) with evenly-spaced threshold gap dimensions from 1 µm to 4 µm as well as with hair spring cross-sectional area from 102 µm to 302 µm are designed to suit specific g-ranges from < 100 mg to 50 g. This hair sensor and sensor array technology is suited for forming MEMS transducer arrays with circuits, including high performance IMUs as well as miniaturized detectors and actuators that require high temporal and spatial resolution, analogous to high-density CMOS imagers.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/143975/1/yemin_1.pd

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

Wide Bandgap Based Devices

Emerging wide bandgap (WBG) semiconductors hold the potential to advance the global industry in the same way that, more than 50 years ago, the invention of the silicon (Si) chip enabled the modern computer era. SiC- and GaN-based devices are starting to become more commercially available. Smaller, faster, and more efficient than their counterpart Si-based components, these WBG devices also offer greater expected reliability in tougher operating conditions. Furthermore, in this frame, a new class of microelectronic-grade semiconducting materials that have an even larger bandgap than the previously established wide bandgap semiconductors, such as GaN and SiC, have been created, and are thus referred to as “ultra-wide bandgap” materials. These materials, which include AlGaN, AlN, diamond, Ga2O3, and BN, offer theoretically superior properties, including a higher critical breakdown field, higher temperature operation, and potentially higher radiation tolerance. These attributes, in turn, make it possible to use revolutionary new devices for extreme environments, such as high-efficiency power transistors, because of the improved Baliga figure of merit, ultra-high voltage pulsed power switches, high-efficiency UV-LEDs, and electronics. This Special Issue aims to collect high quality research papers, short communications, and review articles that focus on wide bandgap device design, fabrication, and advanced characterization. The Special Issue will also publish selected papers from the 43rd Workshop on Compound Semiconductor Devices and Integrated Circuits, held in France (WOCSDICE 2019), which brings together scientists and engineers working in the area of III–V, and other compound semiconductor devices and integrated circuits

Development of a monolithic near-field optomechanical system

In the same year as Einstein's annus mirabilis, English engineer and physicist John Flemming patented the first rectifying diode, which he called the "Flemming valve". Einstein's work on the photoelectric effect would change our understanding of the nature of light - a pivotal moment in the development of quantum theory. Flemming's diode would transform our world as well, often pointed to as the beginning of modern electronics. These ideas, born in the same moment, have remained entwined. Quantum theory has been fundamental to transistor development, and that, in turn, led to the computer revolution and accompanying development of silicon manufacturing. The theoretical and technological gifts these ideas have accumulated over the past hundred years are now laid to bare in the field of cavity optomechanics. The silicon technology that owes its very existence to quantum theory is now leveraged to test the limitations of theory and perhaps to exploit quantum resources for a new class of sensors. Micro-, and even nano-scale, optical cavities are coupled to commensurately miniaturized mechanical oscillators, where strong radiation pressure mediated interactions between their corresponding modes can be realized. The fluctuating position of a mechanical element is imprinted on the phase of light circulating within the cavity, while the varying amplitude of the light alters its momentum. Quantum fluctuations are imprinted on the mechanical element by light within the cavity, establishing correlations between its phase and amplitude. Utilizing the optomechanical system developed in this thesis work we are able to observe the signature of these induced correlations, even in the presence of thermal noise at room-temperature. Moreover, we demonstrate the principle by which correlations can be used to cancel measurement back-action, producing a quantum-enhanced sensitivity to external forces. The system in question is also demonstrated to achieve an imprecision more than three orders of magnitude below that at the standard quantum, at room-temperature, which is unprecedented. A strong radiation pressure interaction between a micron-scale mechanical element and an optical cavity has been achieved by taking advantage of many of the powerful tools developed in the context of building modern computers. Using transistor technology in this new context we engineer an optomechanical system that exhibits an exceptionally large contribution of back-action relative to thermal noise. In addition to observing this back-action signature at ambient temperatures, the large interaction strength is applied to the task of laser cooling with a measurement-based feedback scheme. In this framework, we demonstrate the ability to reduce the thermal occupation of a cryogenically cooled mechanical mode by an additional three orders of magnitude, to a mean occupancy of just 5.3 phonons

Neutralisation of myoelectric interference from recorded nerve signals using models of the electrode impedance

Any form of paralysis due to spinal cord injury or other medical condition, can have a significant impact on the quality and life expectancy of an individual. Advances in medicine and surgery have offered solutions that can improve the condition of a patient, however, most of the times an individual’s life does not dramatically improve. Implanted neuroprosthetic devices can partially restore the lost functionalities by means of functional electrical stimulation techniques. This involves applying patterns of electrical current pulses to innervate the neural pathways between the brain and the affected muscles/organs, while recording of neural information from peripheral nerves can be used as feedback to improve performance. Recording naturally occurring nerve signals via implanted electrodes attached to tripolar amplifier configurations is an approach that has been successfully used for obtaining desired information in non-acute preparations since the mid-70s. The neural signal (i.e. ENG), which can be exploited as feedback to another system (e.g. a stimulator), or simply extracted for further processing, is then intrinsically more reliable in comparison to signals obtained by artificial sensors. Sadly, neural recording of this type can be greatly compromised by myoelectric (i.e. EMG) interference, which is present at the neural interface and registered by the recording amplifier. Although current amplifier configurations reduce myoelectric interference this is suboptimal and therefore there is room for improvement. The main difficulty exists in the frequency-dependence of the electrode-tissue interface impedance which is complex. The simplistic Quasi-Tripole amplifier configuration does not allow for the complete removal of interference but it is the most power efficient because it uses only one instrumentation amplifier. Conversely, the True-Tripole and its developed automatic counterpart the Adaptive-Tripole, although minimise interference and provide means of compensating for the electrode asymmetries and changes that occur to the neural interface (e.g. due to tissue growth), they do not remove interference completely as the insignificant electrode impedance is still important. Additionally, removing interference apart from being dependent on the frequency of the interfering source, it is also subject to its proximity and orientation with respect to the recording electrodes, as this affects the field. Hence neutralisation with those two configurations, in reality, is not achieved in the entire bandwidth of the neural signal in the interfering spectrum. As both are less power efficient than the Quasi-Tripole an alternative configuration offering better performance in terms of interference neutralisation (i.e. frequency-independent, insensitive to the external interference fields) and, if possible, consume less power, is considered highly attractive. The motivation of this work is based on the following fact: as there are models that can mimic the frequency response of metal electrodes it should be possible, by constructing a network of an equivalent arrangement to the impedance of electrodes, to fit the characteristic neutralisation impedance – the impedance needed to balance a recording tripole – and ideally require no adjustment for removing interference. The validity of this postulation is proven in a series of in-vitro preparations using a modified version of the Quasi-Tripole made out of discrete circuit components where an impedance is placed at either side of the outer electrodes for balancing the recording arrangement. Various models were used in place of that impedance. In particular, representing the neutralisation impedance as a parallel RC reduced interference by a factor of 10 at all frequencies in the bandwidth of the neural signal while removed it completely at a spot frequency. Conversely, modelling the effect of the constant phase angle impedance of highly polarisable electrodes using a 20 stages non-uniform RC ladder network resulted in the minimisation of interference without the initial requirement of continuous adjustment. It is demonstrated that with a model that does not perfectly fit the impedance profile of a monopolar electrochemical cell an average reduction in interference of about 100 times is achieved, with the cell arranged as a Wheatstone bridge that can be balanced in the ENG band