Can E. Korman

Flexible packaging of solid-state integrated circuit chips with elastomeric microfluidics

A flexible technology is proposed to integrate smart electronics and microfluidics all embedded in an elastomer package. The microfluidic channels are used to deliver both liquid samples and liquid metals to the integrated circuits (ICs). The liquid metals are used to realize electrical interconnects to the IC chip. This avoids the traditional IC packaging challenges, such as wire-bonding and flip-chip bonding, which are not compatible with current microfluidic technologies. As a demonstration we integrated a CMOS magnetic sensor chip and associate microfluidic channels on a polydimethylsiloxane (PDMS) substrate that allows precise delivery of small liquid samples to the sensor. Furthermore, the packaged system is fully functional under bending curvature radius of one centimetre and uniaxial strain of 15%. The flexible integration of solid-state ICs with microfluidics enables compact flexible electronic and lab-on-a-chip systems, which hold great potential for wearable health monitoring, point-of-care diagnostics and environmental sensing among many other applications.

Noise in MEMS

This review provides a comprehensive survey of noise research in MEMS. Some background on noise and on MEMS is provided. We review noise production mechanisms, and highlight work on the theory and modeling of noise in MEMS. Then noise measurements in the specific types of MEMS are reviewed. Inertial MEMS (accelerometers and angular rate sensors), pressure and acoustic sensors, optical MEMS, RF MEMS, surface acoustic wave devices, flow sensors, and chemical and biological MEMS, as well as data storage devices and magnetic MEMS, are reviewed. We indicate opportunities for additional experimental and computational research on noise in MEMS.

Measurement of noise characteristics of MEMS accelerometers

Microelectromechanical systems (MEMS) are devices that have static or movable components with dimensions on the scale of a micrometer. One particular device that is widely used commercially is the MEMS accelerometer. Such accelerometers typically contain some movable micro beams that measure acceleration in one or two orthogonal directions. Major markets for MEMS accelerometers are automobile airbag triggers, earthquake detection circuits and health care. MEMS accelerometers have advantages over conventional accelerometers because they are smaller, lighter and cheaper. Since MEMS accelerometers are used in many systems, the noise characteristics of these devices are very important. The noise characteristics will influence the performance of the accelerometers especially when operating at lower g conditions. In this work, we report on the noise characteristics and special measurement techniques for Analog Devices ADXL202, ADXL 105 and ADXL 190 accelerometers.

Scaling and data collapse in magnetic viscosity

This article presents experimental evidence for scaling and data collapse in magnetic viscosity. It is demonstrated that, by using appropriate scaling, the “bell-shaped” viscosity coefficient curves observed for different temperatures collapse onto one universal curve. This data collapse reveals a self-similar structure of the viscosity coefficient as a function of two variables: magnetic field and temperature.

Review of Preisach type models driven by stochastic inputs as a model for after-effect

Abstract The article reviews a novel approach to the modeling of after-effect phenomena in hysteretic systems. The after-effect model is based on Preisach-type models driven by stochastic inputs. Random thermal perturbations which result in the gradual loss of memory in hysteretic systems are modeled by discrete and continuous-time stochastic processes. The important properties of the after-effect model are summarized and compared with the traditional thermal activation-type models and with some known experimental facts.

A physics-based semiconductor noise model suitable for efficient numerical implementation

A semiconductor device noise model in the framework of semiclassical transport and Paulis exclusion principle is presented. Terminal current noise is modeled as a direct consequence of electron scattering taking place inside the device at the microscopic level. The approach directly connects electron scattering rates of semiclassical transport theory with the current spectral density at the device terminals. It is shown that the spectral density of steady-state current fluctuations can be obtained from the transient solution of the Boltzmann transport equation with special initial conditions. This formulation is inherently suitable for deterministic solution techniques, for instance, the computationally efficient spherical harmonics method. Approximating the instantaneous value of the occupation number by the occupation probability, this model is able to account for Paulis principle and at the same time describe the behavior of the electron ensemble in terms of independent entities. As a practical demonstration, the model is employed to compute the current noise spectral density due to generation recombination and acoustic and optical phonon scattering for bulk n-type silicon material. Additionally, in order to add more physical insight and to verify results, the model is also employed to compute the low-frequency current spectral density as a function of the electric field and temperature, respectively. The results show good agreement with low-frequency noise measurements reported in literature.

Integrated CMOS surface acoustic wave gas sensor: design and characteristics

The development of inexpensive and miniaturized Surface Acoustics Wave (SAW) gas sensors that are highly selective and sensitive is described. These sensors are implemented with micro-electro-mechanical systems (MEMS) in CMOS technology. IDT equivalent circuit and model for SAW delay line is introduced. Simulation results are included for characterization and design of the sensor. In this paper we will describe the design and post-processing steps to implement SAW device in CMOS technology. Design parameters of this device were obtained using modeling equivalent circuit to characterize sensor. Two approaches were used in the design of the SAW gas sensor that will be discussed. A CMOS chip was fabricated using MOSIS. Thin film ZnO was grown on Silicon based die and its characterizations is presented.

Investigation of the threshold voltage of MOSFETs with position- and potential-dependent interface trap distributions using a fixed-point iteration method

Simulation results are presented for a MOSFET with position- and energy- (potential-) dependent interface trap distributions that may be typical for devices subjected to interface-trap-producing processes such as hot-electron degradation. The interface-trap distribution is modeled as a Gaussian peak at a given position along the channel, and the energy dependence is derived from C-V measurements from an MOS capacitor exposed to ionizing radiation. A novel fixed-point technique is used to solve the two-dimensional boundary-value problem. The technique is shown to be globally convergent for arbitrary distributions of interface traps. A comparison of the convergence properties of the Newton and fixed-point methods is presented, and it is shown that for some important cases the Newton technique fails to converge while the fixed-point technique converges with a geometric convergence rate. >

CMOS integrated gas sensor chip using SAW technology

The development of inexpensive and miniaturized SAW gas sensors that are highly selective and sensitive is introduced. These sensors are implemented with micro-electro-mechanical systems (MEMS) in CMOS technology. Since the sensors are fabricated on a silicon substrate, additional signal processing circuitry can easily be integrated into the chip thereby readily providing functions such as multiplexing and analog-to-digital conversion that are needed for integration into a network.

Circular MAGFET Design and SNR Optimization for Magnetic Bead Detection

A novel circular CMOS MAGFET (Magnetic Field Effect Transistor) design is introduced and a novel device geometry design methodology is proposed to optimize the magnetic particle detection sensitivity of such devices. In order to optimize the signal to noise ratio, it was determined that the geometry of the MAGFET is required to have specific ratios, where its sector angle θ and its inner and outer radii <i>r</i>₁ and <i>r</i>₂ are optimized when θ/<i>ln</i>(<i>r</i>₂/<i>r</i>₁) = 1.3 . Compared to the more traditional rectangular MAGFET, the circular MAGFET has compatible SNR peak performance with rectangular MAGET. However, when the size of the MAGFET is scaled down in order to detect smaller magnetic particles, the proposed circular MAGFET has more robust SNR performance, design flexibility and tolerance to processing variations.