Pushpapraj Singh

Gate-All-Around Junctionless Nanowire MOSFET With Improved Low-Frequency Noise Behavior

We present n-type gate-all-around (GAA) junctionless nanowire field-effect transistor (JL-NWFET) along with low-frequency noise (LFN) with respect to channel doping and the gate bias voltage. Irrespective of doping level in the channel, which is the same as that of source/drain, the JL-NWFET shows approximately five orders of magnitude lower spectral noise than the inversion-mode counterpart. LFN in JL-NWFET is also found less sensitive to gate bias voltage and to the frequency. The superior LFN behavior in GAA JL-NWFET is attributed to the conduction of carriers inside the uniformly doped nanowire channel. JL-NWFET-based sensing elements can thus be suitable in physical transducers to maximize the detection limits.

Tantalum-Nitride Antifuse Electromechanical OTP for Embedded Memory Applications

Embedded nonvolatile memory (NVM) integrated in the back-end of line processes are of high interest, particularly for rugged environments (high temperature/radiation or vibration). This letter demonstrates the use of tantalum nitride microbeams as antifuse one-time programmable (OTP) NVM. It needs a single mask process and can be integrated above an integrated circuit. Typical fusing current is 1 mA, operating voltage is 4 V, and the measured contact resistance is <;2 kQ. A hybrid one-transistor/one microbeam/bit memory array is proposed for back-end compatible and low-cost OTP NVM integration.

Gate-bias-controlled sensitivity and SNR enhancement in a nanowire FET pressure sensor

This work demonstrates a nanoelectromechanical pressure sensor based on a nanowire field-effect transistor (NWFET) sensing element. We report that the sensitivity of the pressure sensor can be enhanced up to four times when NWFET operates in subthreshold mode instead of inversion mode. The sensitivity enhancement is attributed to carrier confinement inside the nanowire channel which is obtained by gate bias tuning. In particular, the pressure sensitivity enhances from 0.019 to 0.079 (mA/A)/mmHg by changing the NWFET gate bias from 0.2 V (inversion region) to −0.2 V (subthreshold region). The low-frequency noise characteristics show the significant reduction in drain current noise for NWFET when biased in the subthreshold region, enhancing the signal-to-noise ratio (SNR) from 2 × 106 (inversion region) to 2.4 × 109 (subthreshold region). The result shows that the NWFET-based pressure sensor operates at a low bias with higher piezoresistance and can be used to measure low pressures with a high SNR.

Tunable piezoresistance and noise in gate-all-around nanowire field-effect-transistor

The piezoresistance and noise of n-type gate-all-around nanowire field-effect-transistor (NWFET) is investigated as a function of gate bias. With narrow gate bias span of 0.6 V near threshold region, the piezoresistive coefficient of NWFET enhances up to seven times from 29 × 10−11 Pa−1 to 207 × 10−11 Pa−1 under compressive and tensile strain conditions. Results reveal that the low frequency noise is reduced when operated in subthreshold region. The higher piezoresistive coefficient and reduced noise improve the sensor resolution (minimum detectable strain) by sixteen times. NWFET operates at low bias with higher piezoresistance and signal-to-noise ratio and offers promising applications in strain sensors.

A monolithic 9 degree of freedom (DOF) capacitive inertial MEMS platform

A monolithic 9 degree of freedom capacitive inertial MEMS platform is presented in this paper. This platform for the first time integrates 3 axis gyroscopes, accelerometers, and Lorentz Force magnetometers together on the same chip without using any magnetic materials. This reduces the assembly cost, and fully eliminates the need of magnetic material processing and axis misalignment calibration. The fabricated sensors, vacuum packaged (vacuum ~100mTorr) at wafer level with epi-polysilicon through silicon interposer (TSI) wafer using eutectic bonding, performed within 10% of the simulation results.

All metal nanoelectromechanical switch working at 300 °C for rugged electronics applications.

An all metal based electrostatic nanoelectromechanical switch has been fabricated using a one mask process. High temperature cycling behavior is demonstrated in a vacuum chamber at 300 °C for more than 28 hours. The compelling results indicate that the design is promising for the realization of rugged electronics with three-dimensional integration.

A Cantilever-Based NEM Nonvolatile Memory Utilizing Electrostatic Actuation and Vibrational Deactuation for High-Temperature Operation

This paper proposes a cantilever-based nanoelectromechanical (NEM) nonvolatile memory (NVM) with a novel write scheme for reliable memory operation at very high-operating temperature (up to 300 °C) in rugged electronics. The memory bit (0/1) is formed by the opening/closing of a cantilever beam. Permanent retention is obtained by adhesive force between two smooth surfaces in contact, eliminating leakage observed in all types of storage-layer-based NVMs. This allows the proposed NEM memory structure to be implemented using a simple bilayer design and easily integrated with the CMOS platform with leakage of 144 pA, which is significantly less compared with SRAM. The experimental analysis of vibrational reset is reported for the first time in this paper. An array structure using the proposed NEM memory device and CMOS devices is presented. Each bit cell consists of one NEM memory device and one nMOS transistor for realizing full random-access operation.

Piezoresistive Sensing Performance of Junctionless Nanowire FET

This letter investigates junctionless nanowire field-effect transistor (NWFET) (JL-NWFET) parameters such as piezoresistance and low-frequency noise (LFN) with respect to channel doping and gate bias. The JL-NWFET is piezoresistive, and its gauge factor (GF ) is increased from 24 to 47 by reducing the channel doping ten times from 6.7 × 1019 to 6.7 × 1018 cm-3. Significant variations of GF and LFN are observed when the JL-NWFET is operated from subthreshold to on-state regime, and resolution (minimum detectable strain) is improved four times compared to inversion-mode NWFET. The simple fabrication and superior resolution formulate JL-NWFET as a promising sensing element for miniaturized nanoelectromechanical sensors.

Molecular adhesion controlled microelectromechanical memory device for harsh environment data storage

This work demonstrates a cantilever based electrostatic microelectromechanical system device operating as a memory element. Volatile and non-volatile functions are engineered by manipulating molecular adhesion force through contact dimples and restoring force using the cantilever design. For non-volatile RESET operation, a method of detaching the cantilever with 3 V pulsating DC signal at 1 MHz is proposed. SET/RESET cycles are performed up to 103 times at 300 °C without any performance degradation. A writing speed of up to 0.94 μs is achieved, which is faster than conventional high temperature flash memories. With demonstrated attributes, the fabricated device offers excellent potential for harsh environment data storage applications.

Design, Fabrication and Characterization of Ultra Miniature Piezoresistive Pressure Sensors for Medical Implants

Pressure sensors using MEMS technology have been advanced due to their low cost, small size and high sensitivity, which is an advantage for biomedical applications. In this paper,silicon nanowire was proposed to be used as the piezoresistors due to the high sensitivity [1][2].The sensors were designed, and characterized for the use of medical devices for pressure monitoring. The pressure sensor size is 2mm x 2mm with embedded SiNWs of 90nm x150nm been fabricated. Additionally, the sensitivity of 0.0024 Pa-1 pressure sensor has been demonstrated.