No abstract

A novel CMOS device architecture called silicon on nothing (SON) is proposed, which allows extremely thin (in the order of a few nanometers) buried dielectrics and silicon films to be fabricated with high resolution and uniformity guarantied by epitaxial process. The SON process allows the buried dielectric (which may be an oxide but also an air gap) to be fabricated locally in dedicated parts of the chip, which may present advantages in terms of cost and facility of system-on-chip integration. The SON stack itself is physically confined to the under-gate-plus-spacer area of a device, thus enabling extremely shallow and highly doped extensions, while leaving the HDD (highly doped drain) junctions comfortably deep. Therefore, SON embodies the ideal device architecture taking the best elements from both bulk and SOI and getting rid of their drawbacks. According to simulation results, SON enables excellent Ion/Ioff trade-off, suppressed self-heating, low S/D series resistance, close to ideal subthreshold slope, and high immunity to SCE and DIBL down to ultimate device dimensions of 30 to 50 nm.

No abstract

Piezoelectric Energy Harvesters (PEH) are usually used to convert mechanical energy (vibration, shocks) into electrical energy, in order to supply energy-autonomous sensor nodes in industrial, biomedical or domotic applications. Non-linear extraction strategies such as Synchronous Electrical Charge Extraction (SECE) [1-2], energy investing [3] or Synchronized Switch Harvesting on Inductor (SSHI) [4] have been developed to maximize the extracted energy from harmonic excitations.However, in most of today's applications, vibrations are not periodic and mechanical shocks occur at unpredictable rates [4].SSHI interfaces naturally seemed to be the most appropriate candidate for harvesting shocks as they exhibit outstanding performance in periodic excitations [4]. However, the SSHI strategy presents inherent weaknesses while harvesting shocks, since the invested energy stored in the piezoelectric capacitance cannot be recovered.In this work, we propose a self-starting, battery-less, 0.55mm 2 integrated energy harvesting interface based on SECE strategy which has been optimized to work under shock stimulus. Due to the sporadic nature of mechanical shocks which imply long periods of inactivity and brief energy peaks, the interface's average consumption is optimized by minimizing the quiescent power. A dedicated energy saving sequencing has thus been designed, reducing the static current to 30nA and enabling energy to be extracted with only one single 8µJ shock occurring every 100s. Our SECE-based circuit features a shock FoM 1.6x greater than previous SSHI-based interfaces [4].The proposed system depicted in Fig.1 is made of a negative voltage converter rectifying the PEH output voltage, and a SECE power path controlled by a sequenced circuit. The sequencing is divided in 4 phases and the associated time diagrams are illustrated in Fig.2. During the sleeping mode T1, all blocks except the shock detection (SD) are turned off. During the starting phase, the energy is stored in CASIC through a cold-start path, increasing VASIC. This will progressively turn on the SD.Next, when stress applied to the piezoelectric material leads to an increase in VREC, the SD checks if the electrical energy

No abstract

This paper introduces a new semi-flexible device able to turn thermal gradients into electricity by using a curved bimetal coupled to an electret-based converter. In fact, a two-steps conversion is carried out: (i) a curved bimetal turns the thermal gradient into a mechanical oscillation that is then (ii) converted into electricity thanks to an electrostatic converter using electrets in Teflon®. The semi-flexible and low cost design of these new energy converters pave the way to mass production over large areas of thermal energy harvesters. Raw output powers up to 13.46µW per device were reached on a hot source at 60°C and forced convection. Then, a DC-to-DC flyback converter has been sized to turn the energy harvesters' raw output powers into a viable supply source for an electronic circuit (DC@3V). At the end, 10µW of directly usable output power were reached with 3 devices, which is compatible with Wireless Sensor Networks powering applications.

This paper presents a fully integrated, self-starting shock-optimized Synchronous Electric Charge Extraction (SECE) interface for piezoelectric harvesters (PEHs). After introducing a model of the electromechanical system under shocks, we prove that the SECE is the most appropriate electrical interface to maximize the harvested energy from our PEH. The proposed interface is then presented, both at system-and transistor-levels. Thanks to a dedicated sequencing, its quiescent current is as low as 30nA. This makes the proposed interface efficient even under time-spaced shocks occurring at sporadic and unpredictable rates. The circuit is for instance able to maintain its self-powered operation while harvesting very small shocks of happening every 100 seconds. Our chip was fabricated in CMOS 40nm technology, and occupies a 0.55mm 2 core area. The measured maximum electrical efficiency under shocks reaches 91%. Under shocks, the harvested energy by the proposed shock-optimized SECE interface is 4.2 times higher than using a standard energy harvesting circuit, leading to the best shock FoM among prior art.

No abstract