Temperature controlled oven for low noise measurement systems [forelectromigration characterization]

Low-frequency noise (LFN) measurements are often applied to the characterization of electron devices. When such measurements have to be performed on electronic components maintained at a given temperature, the thermal stability of the oven which is used for this purpose becomes a major concern, because of the high sensitivity of electron devices to temperature fluctuations (TF's). In this paper, we present the realization of a high-stability temperature-controlled oven, purposely designed for the characterization of electromigration in metal interconnections of integrated circuits by means of low-frequency noise measurements. The prototype which has been realized demonstrates that the contribution of the thermal fluctuations of the oven to the background noise of the measurement system is negligible down to frequencies as low as 10 mHz in the entire range of operating temperatures (25-250°C)     

Low-frequency noise measurements on semiconductor devices using aprobe station

We report a measurement technique that would allow the mapping of the low-frequency noise characteristics of devices across a wafer. We show that we can reliably measure the noise by using a probe station. We also show that the sensitivity of the setup is not limited by the probes     

Thermal-mechanical-noise-based CMUT characterization and sensing

When capacitive micromachined ultrasonic transducers (CMUTs) are monolithically integrated with custom-designed low-noise electronics, the output noise of the system can be dominated by the CMUT thermal-mechanical noise both in air and in immersion even for devices with low capacitance. Because the thermal-mechanical noise can be related to the electrical admittance of the CMUTs, this provides an effective means of device characterization. This approach yields a novel method to test the functionality and uniformity of CMUT arrays and the integrated electronics when a direct connection to CMUT array element terminals is not available. Because these measurements can be performed in air at the wafer level, the approach is suitable for batch manufacturing and testing. We demonstrate this method on the elements of an 800-μm-diameter CMUT-on-CMOS array designed for intravascular imaging in the 10 to 20 MHz range. Noise measurements in air show the expected resonance behavior and spring softening effects. Noise measurements in immersion for the same array provide useful information on both the acoustic cross talk and radiation properties of the CMUT array elements. The good agreement between a CMUT model based on finite difference and boundary element methods and the noise measurements validates the model and indicates that the output noise is indeed dominated by thermal-mechanical noise. The measurement method can be exploited to implement CMUT-based passive sensors to measure immersion medium properties, or other parameters affecting the electro-mechanics of the CMUT structure.     

Ultra low-noise preamplifier for low-frequency noise measurementsin electron devices

The design and realization of an ultra-low-noise, high-input-impedance amplifier for low-frequency noise measurements in electronic devices is presented. Special care is devoted to the solution of typical problems encountered in the design of low-noise low-frequency equipment, such as power supply noise and temperature fluctuations. The ultra-low-noise preamplifier has a bandwidth of over seven decades with a low-frequency roll-off of 4 mHz. The noise characteristics obtained are sensibly better than those of commercial preamplifiers commonly adopted in low-frequency noise measurements. The application of this preamplifier to the realization of standard 1/f^γ noise generators is presented     

Ultralow-noise PC-Based measurement system for the characterizationof the metallizations of integrated circuits

The design, realization, and test of a multichannel ultralow-noise data acquisition system are described in this paper. The instrument, controlled by a personal computer (PC), has been specifically designed for performing low-frequency noise measurements on interconnect lines of an integrated circuits. A specifically designed ultralow-noise preamplifier has been realized and an optical link has been used for connecting the front-end of the instrument with the PC in order to minimize the effects of electromagnetic interferences. An overall background noise some orders of magnitude below that of preexisting instrumentation has been obtained. In particular, the power spectral density of the equivalent input voltage noise was 1.5, 3, 10 nV/(Hz)^1/2 at 1, 0.1, and 0.01 Hz, respectively     

Ultra low-noise current sources

The solid state DC current sources available on the market are not suitable for applications in low noise measurement systems because of the high level of low-frequency noise introduced in the measurement chain. The most important cause of low-frequency noise in such instruments is the solid state device used as a voltage reference (usually a Zener diode). This problem has been solved, in the instrument described in this paper, by using a new circuit topology in which the solid-state voltage reference has been substituted by a low-noise battery. The instrument, capable of supplying a current as high as 100 mA, is characterized by a low-frequency noise level some orders of magnitude lower than that of similar commercial instrumentation     

Update: a protein microbolometer for focal plane arrays

 The current infrared microbolometer technology using vanadium oxide material is not quite as sensitive as a cooled platinum silicide or cooled mercury cadmium telluride or indium antimonide array. The performance factor of the present IR bolometer needs to be improved by at least an order of magnitude to make a bolometric IR device comparable to the cooled detector arrays. I recently reported [1] that thin films of globular proteins such as cytochrome c exhibit a high temperature coefficient of resistance (TCR) value of about 10% as compared with a value of 2.0 to 2.5% normally observed in VOx films. The measurements that were initially reported were taken two weeks after the thin films had been prepared. The measurement of the TCR values presented in this report were taken within three days of the films being prepared. These TCR values are very high, approximately 35% for temperatures between 25 and 60°C, and they have a sheet resistance around 1 to 2 Ω/cm² with a current of 1 mA. The values of TCR were very uniform over the wafer surface, but the values varied slightly from wafer to wafer. It appears that a cytochrome c monolayer on metal oxide semiconductor (CMOS) electronics could generate miniaturized, uncooled IR detector arrays that would be suitable for military and commercial applications that require very high performance and low-power drain. With these high TCR values, biological uncooled devices will have the potential for long-range thermal imaging applications comparable to cooled detectors. I have also examined the sheet resistance of the protein layer with an increase in the bias current near ambient temperature. I found that the sheet resistance of cytochrome c rapidly goes towards the negative values as the bias current is increased. On the other hand, TCR characteristics remained unchanged with an increase in bias current. This is a very interesting phenomenon that has never been reported in biomolecules. I am making further explorations into the electrical properties of many proteins for possible device applications. Received: 8 February 1999/Reviewed and accepted: 9 February 1999     

The Future of Microelectromechanical systems (MEMS)

Abstract:  MEMS-based products produced in 2005 had a value of $8bn, 40% of which was sensors. The balance was for products that included micromachined features, such as ink jet print heads, catheters and RF IC chips with embedded inductors. Growth projections follow a hockey stick curve, with the value of products rising to $40bn in 2015 and $200bn in 2025! Growth to date has come from a combination of technology displacement, as exemplified by automotive pressure sensors and airbag accelerometers and new products, such as miniaturised guidance systems for military applications and wireless tire pressure sensors. Much of the growth in MEMS business is expected to come from products that are in the early stages of development or yet to be invented. Some of these devices include disposable chips for performing assays on blood and tissue samples, which are now performed in hospital laboratories, integrated optical switching and processing chips, and various RF communication and remote sensing products.The key to enabling the projected 25-fold growth in MEMS products is development of appropriate technologies for integrating multiple devices with electronics on a single chip. At present, there are two approaches to integrating MEMS devices with electronics. Either the MEMS device is fabricated in polysilicon, as part of the CMOS wafer fabrication sequence or a discrete MEMS device is packaged with a separate ASIC chip. Neither of these approaches is entirely satisfactory, though, for building the high-value, system-on-chip products that are envisioned. It is this author's opinion that a combination of self-assembly techniques in conjunction with wafer stacking, offer a viable path to realizing ubiquitous, complex MEMS systems.     

Study of the kink effect in AlInAs/GaInAs/InP composite channel HFETs

A detailed study is presented on AlInAs/InGaAs/InP composite channels. These devices combine the advantages of high mobility at low voltages and high electric field operations thanks to the use of a composite channel formed by a thin InGaAs layer and a doped InP subchannel. Due to the very low gate leakage currents, it has been possible to precisely study the impact ionization contributions as a function of the temperature. Surprisingly, it is not possible from our measurements to correlate the kink effect observed in the devices with the impact ionization phenomenon. Therefore, a detailed study of the AlInAs deep traps, and the deep levels detected in the devices has been performed using DLTS, CTS, drain lag, and low frequency noise measurements. The observation of the kink effect in our HFETs has been clearly connected to an electron trap located in the AlInAs layers. In order to confirm this result, the optical properties of this deep trap have been studied by I–V measurements under optical excitation for HFETs, and by DLOS on bulk AlInAs. Our measurements show that the same defect is observed in AlInAs and in the HFETs and that it is possible to suppress the kink effect by an optical ionization of this electron trap. Finally, our electro-optical study shows the direct correlation between deep traps in the AlInAs barrier layers and the kink effect in these devices.     

轨道交通地下站台低频结构噪声预测及其传播特性研究

该研究在对地下车站站台噪声现场试验及分析的基础上,通过对站台结构的精细化模拟,建立适用于站台结构振动辐射噪声分析的声场有限元模型,对轨道交通列车荷载作用下站台内低频结构噪声进行预测,分析了站台空间内低频结构噪声的声场分布特性,并从声模态的角度揭示了低频噪声传播机理。研究结果表明:地下站台低频噪声在50 Hz~85 Hz内存在显著峰值,主要来源于站台板的结构振动;低频结构噪声在站台不同平面位置的声压级水平表现出显著波动性,声压级大小在68.6 dB~80.4 dB,波动范围为12 dB;站台声腔敏感共振频率对低频结构噪声的影响显著,会显著放大车站低频结构噪声,改变声腔的高度可有效改善低频结构噪声对乘客的影响。     

Low-frequency current fluctuations in individual semiconducting single-wall carbon nanotubes

We present a systematic study on low-frequency current fluctuations of nanodevices consisting of one single semiconducting nanotube, which exhibit significant 1/f-type noise. By examining devices with different switching mechanisms, carrier types (electrons vs holes), and channel lengths, we show that the 1/f fluctuation level in semiconducting nanotubes is correlated to the total number of transport carriers present in the system. However, the 1/f noise level per carrier is not larger than that of most bulk conventional semiconductors, e.g., Si. The pronounced noise level observed in nanotube devices simply reflects on the small number of carriers involved in transport. These results not only provide the basis to quantify the noise behavior in a one-dimensional transport system but also suggest a valuable way to characterize low-dimensional nanostructures based on the 1/f fluctuation phenomenon.     

Ultralow-noise programmable voltage source

To avoid introducing additional noise sources while making low-frequency noise measurements, batteries are normally used instead of electronic power supplies. This paper presents an alternative solution by describing the design, construction, and testing of an ultralow-noise voltage source. Such a power supply can be computer controlled and has a typical noise level two orders of magnitude below that of similar commercial instruments. Some typical values of the spectral density of the voltage fluctuations at its output are: (10^-12, 10^-15, 10^-16) V²/Hz at (0.01, 0.1, and 1) Hz, respectively. These noise performances are almost independent of the supplied current, with a degradation of less than 3 dB up to 400 mA. A special algorithm for digital-to-analog conversion, using passive devices with 1% tolerance, ensures a resolution of 2.5 mV and an accuracy better than ±1.5 mV over the entire output range from 0 to 8 V     

A compact self-shielding prober for accurate measurement ofon-wafer electron devices

A compact self-shielding prober is proposed for measuring low-current-voltage characteristics of on-wafer electron devices. In the prober, a wafer and a wafer stage are set in a very small shielded region mostly enclosed by a plane top-board, a wafer-stage shield, and a sidewall shielding ring. A current of less than a picoampere can easily be measured without any shielding box. A prober designed to observe all devices on 4-in wafers can be as small as 27 cm×27 cm×12 cm. High-speed input/output waveforms of on-wafer large scale integrated circuits (LSIs) observed with this prober are as clear as those of packaged LSIs observed directly     

KTV包间低频噪声控制

KTV包间内的噪声污染主要在低频63 Hz～125 Hz,噪声级一般可以超过105 dB,其噪声源边界排放噪声也超出了相应的限值,针对KTV包间的噪声污染,介绍了目前比较成熟的噪声处理方案。首先KTV包间内的墙壁、顶棚、门和地板隔声处理;其次是介绍包间采取的吸声材料和广泛应用的吸声结构;包间音箱设备的隔振处理;包间内减少声波的泄露;以及新型局域共振声子晶体的理论及应用。     

Tracking Control of a Nanopositioner Using Complementary Sensors

Piezoelectric tube actuators are widely used in atomic force and scanning tunneling microscopy (STM) for nanoscale positioning. There has been a consistent effort to increase the scan speed of these actuators using feedback control techniques. A feedback controller requires a measurement of the scanner's deflection, which is often provided by a capacitive sensor. Such measurements are corrupted by sensor noise, typically in the order of 20 pm/ radicHz rms. Over a bandwidth of 10 kHz, this translates into an rms noise of 2 nm, clearly inadequate for applications that require subnanometer positioning accuracy, e.g., STM. In this paper, we illustrate how the strain voltage induced in a free electrode of the scanner can be used as an additional displacement signal. The noise level corresponding to the strain signal is about three orders of magnitude less than that of a capacitive sensor, making it an ideal choice for nanopositioning applications. However, it cannot be used for dc and low-frequency measurements. A two-sensor-based controller is designed to use the capacitive sensor signal at low frequencies, and the strain displacement signal at high frequencies. By limiting the capacitive sensor feedback loop bandwidth to less than 100 Hz, the rms value of the noise is reduced to well below 1 nm. For almost the same noise level, the two-sensor-based control structure achieves a closed-loop bandwidth of more than three times that of the single-sensor-based controller.     

40 t锅炉低频消声器的设计

40 t燃气锅炉的低频噪声在频率63 Hz及12 5Hz尤为突出,是影响环境噪声达标的关键成分。通过对吸声材料声学特性的调研,根据相关纤维材料在上述低频段的声学基本常数[γ]和Z c;分析不同流阻率的多孔材料层背衬刚壁时,相关低频吸声系数的变化。同时按燃气锅炉排烟消声器的流阻要求,进而对阻性消声器的构造开展综合研究,设计一种内置整流体的圆筒状消声器。声学测量表明：5 m长、φ 2.4 m外径、通道直径φ 1.6 m内置整流体0.6 m的圆筒状排烟消声器,在31.5到250 Hz低频段有10～16 dB的降噪量,解决锅炉运转时低频噪声超标问题,使当地环境噪声达标。     

Finishing of AT-cut quartz crystal wafer with nanometric thickness uniformity by pulse-modulated atmospheric pressure plasma etching

Quartz resonator is a very important device to generate a clock frequency for information and telecommunication system. Improvement of the productivity of the quartz resonator is always required because a huge amount of the resonator is demanded for installing to various electronic devices. Resonance frequency of the quartz resonator is decided by the thickness of the quartz crystal wafer. Therefore, it is necessary to uniform the thickness distribution of the wafer with nanometric level. We have proposed the improvement technique of the thickness distribution of the quartz crystal wafer by numerically controlled correction using atmospheric pressure plasma which is non-contact and chemical removal technique. Heating effects of the quartz wafer in the removal rate and the correction accuracy were investigated. The heating of the substrate and compensate of the scanning speed of the worktable according to the variation of the surface temperature enabled an increase of 50% in the etching rate and 10-nanometric-level accuracy in the correction of the thickness distribution of the quartz wafer, respectively.     

Method for Realizing the Possibilities of the Dulkyn Low-Frequency Gravitational-Wave Detector

A system is proposed for self-compensating low-frequency noise in the Dulkyn pentagonal laser-interferometer low-frequency gravitational-wave detector. For a signal-to-noise ratio at the output of the optical part of the scheme of no better than 10^–7, the system makes it possible to operate in real time after roughly 25 periods of a detected gravitational-wave signal. With the orbital motion of the Earth this will make it possible to implement an antenna (a response of the detector to gravitational radiation) having an artificial aperture and a radiation pattern width of a few minutes of arc.     

1/f noise of electrolytic capacitors as a reliability indicator

The electrical noise of capacitors and the relationship between typical imperfections in capacitors and their excess noise are described. It was assumed that a noisy capacitor is a poor-quality one. Investigations were aimed at the determination of a correlation between the inherent noise of capacitors and their reliability (time to failure) and also at the determination of an indicator to predict reliability. Investigations (noise measurements and reliability tests) were carried out on two samples of aluminium electrolytic capacitors. The method of reliability prediction for electrolytic capacitors based on their low-frequency noise is described. For reliability prediction the noise intensity G at a frequency of 2 Hz was used as a reliability indicator. It was found that the evaluated correlation coefficients between the noise parameter G and the time to failure, t, are statistically significant. It is concluded that it is possible to predict the lifetime of aluminium electrolytic capacitors on the basis of their 1/f noise. © 1998 John Wiley & Sons, Ltd.     

Selective gas sensing with a single pristine graphene transistor

We show that vapors of different chemicals produce distinguishably different effects on the low-frequency noise spectra of graphene. It was found in a systematic study that some gases change the electrical resistance of graphene devices without changing their low-frequency noise spectra while other gases modify the noise spectra by inducing Lorentzian components with distinctive features. The characteristic frequency f(c) of the Lorentzian noise bulges in graphene devices is different for different chemicals and varies from f(c) = 10-20 Hz to f(c) = 1300-1600 Hz for tetrahydrofuran and chloroform vapors, respectively. The obtained results indicate that the low-frequency noise in combination with other sensing parameters can allow one to achieve the selective gas sensing with a single pristine graphene transistor. Our method of gas sensing with graphene does not require graphene surface functionalization or fabrication of an array of the devices with each tuned to a certain chemical.