STMicroelectronics

About: STMicroelectronics is a company organization based out in Geneva, Switzerland. It is known for research contribution in the topics: Signal & Transistor. The organization has 17172 authors who have published 29543 publications receiving 300766 citations. The organization is also known as: SGS-Thomson & STM.

All-Around SiN Stressor for High and Homogeneous Tensile Strain in Germanium Microdisk Cavities

Abstract: emitter into an effi cient emitter-like III–V semiconductors. There is no need a priori to reach the direct-band gap regime to demonstrate a Ge laser source. The fi rst Ge laser demonstration was obtained with a weak tensile strain around 0.25% resulting from the difference of thermal dilation coeffi cients between Ge and the silicon substrate. [ 10,11 ] This tensile strain amplitude is not suffi cient as evidenced by the 300 kA cm −2 threshold announced for an electrically pumped laser, [ 11 ] a value too high for realistic integration purposes. Enhancing tensile strain transfer into Ge optical cavities is thus requested in order to signifi cantly decrease the lasing threshold, and different approaches have been proposed in the literature. [ 12–14 ] High level strain transfers have been evidenced using strained silicon nitride (SiNH referred to as SiN in the following) layers as stressor layers. [ 15–20 ] The use of stressor layers is widely investigated since it relies on a complementary metal oxide semiconductor (CMOS)-compatible process. There are however some trade-offs in strain engineering as evidenced by the link between strain amplitude and cavity volumes, i.e., achieving high tensile strain in large structures being challenging. In this perspective, microdisks are very interesting compact structures as one can expect to transfer high tensile strain and to obtain low lasing threshold due to whispering gallery mode confi nement. [ 21,22 ] A 1% biaxial strain transfer on the top of a Ge microdisk using strained SiN deposition has been recently demonstrated. [ 20 ] One of the drawbacks of this recent demonstration is the spatial inhomogeneity of the transferred strain. This limitation can be lifted by using an all-around stressor method in a similar way that a gate all-around design provides more fl exibility to tailor the properties of advanced CMOS transistors. [ 23 ]

Automatic Mode Matching in MEMS Vibrating Gyroscopes Using Extremum-Seeking Control

Abstract: In order to enhance the sensitivity and to reduce the readout circuit complexity of any angular velocity microsensor (vibrating gyroscope), it is crucial to reduce the frequency mismatch of its resonant modes of vibration. Achieving a good matching accuracy during fabrication is rather difficult because of tolerances and process variations that detrimentally affect the manufacturing precision. Moreover, even assuming to achieve a good frequency matching through fabrication or postfabrication calibration, it is very likely that parametric variations induced by the external environment during the normal operation of the device disrupt any initial tuning. For these reasons, in this paper, an alternative way to accomplish the frequency-matching condition is suggested, which exploits a real-time adjusting mechanism based on an automatic mode-matching control loop. In particular, this paper describes the details of an adaptive controller capable of automatically matching the resonant frequencies of the two main modes of vibration of a single-axis vibrating microgyroscope, under the provision that there is an underlying mechanism through which the frequency mismatch can be controlled by adjusting a suitable tunable parameter. The controller is designed by considering the requirement of reducing its complexity, so that it can be easily implemented on cheap sensors. Owing to a key observation that allows the recast of the frequency-matching problem as a maximization problem, the proposed mode-matching controller is actually designed as a standard perturbation-based extremum-seeking controller, which can be implemented by using few analog electronic components. The proposed solution has been tested on the LISY300AL yaw-rate microelectromechanical system gyroscope manufactured by STMicroelectronics, showing that a mode matching of nearly 1 Hz or less can be easily attained.

Scan design and secure chip [secure IC testing]

Abstract: Testing a secure system is often considered as a severe bottleneck. While testability requires an increase in both observability and controllability, secure chips are designed with the reverse in mind, limiting access to chip content and on-chip controllability functions. As a result, using usual design for testability (DfT) techniques when designing secure ICs may seriously decrease the level of security provided by the chip. This dilemma is even more severe as secure applications need well-tested hardware to ensure that the programmed operations are correctly executed. In this paper, a security analysis of the scan technique is performed. This analysis aims at pointing out the security vulnerability induced by using such a DfT technique. A solution securing the scan is finally proposed.

TEC-Tree: A Low-Cost, Parallelizable Tree for Efficient Defense Against Memory Replay Attacks

Abstract: Replay attacks are often the most costly attacks to thwart when dealing with off-chip memory integrity. With a trusted System-on-Chip, the existing countermeasures against replay require a large amount of on-chip memory to provide tamper-proof storage for metadata such as hash values or nonces. Tree-based strategies can be deployed to reduce this unacceptable overhead; for example, the well-known Merkle tree technique decreases this overhead to a single hash value. However, it comes at the cost of performance-killing characteristics for embedded systems --- e.g. non-parallelizable hash computations on tree updates. In this paper, we propose an alternative solution: the Tamper-Evident Counter Tree (TEC-Tree). It allows for tamper-evident off-chip storage of the nonces involved in a replay countermeasure; TEC-Tree parallelizes the computations involved in both the authentication and tree update processes. Moreover, because our tree relies on block encryption, it provides data confidentiality at no extra cost. TEC-Tree is a deployable solution for memory integrity, with low performance hit and hardware cost.

Radiation effects on floating-gate memory cells

Abstract: We have addressed the problem of threshold voltage (V/sub TH/) variation in flash memory cells after heavy-ion irradiation by using specially designed array structures and test instruments. After irradiation, low V/sub TH/ tails appear in V/sub TH/ distributions, growing with ion linear energy transfer (LET) and fluence. In particular, high LET ions, such as iodine used in this paper, can produce a bit flip. Since the existing models cannot account for large charge losses from the floating gate, we propose a new mechanism, based on the excess of positive charge produced by a single ion, temporarily lowering the tunnel oxide barrier (positive charge assisted leakage current) and enhancing the tunneling current. This mechanism fully explains the experimental data we present.