A. Arshak

Glucose monitoring using electromagnetic waves and microsensor with interdigitated electrodes

A microscale glucose sensor for biomedical applications was fabricated utilizing the enzyme glucose oxidase and the polymer poly(o-phenylenediamine). A solution containing the enzyme immobilized in the polymer was deposited on interdigitated microelectrodes to form sensor arrays. This was achieved using novel nanopatterning technology offered by BioForce NanoeNabler™. Samples containing different concentrations of glucose were applied to the sensor while the system was being monitored for variances in either current or conductance. The resulting changes in the electrical characteristics of the sensor monitored in real time were found to be proportional to the different concentrations of glucose applied. It is strongly believed that the size reduction of the sensor to a few microns described in this paper creates new opportunities in the areas of chemical and biological sensor development.

Negative resist image by dry etching: a novel surface imaging resist scheme

Top surface imaging (TSI) is an established technique that can be used to improve resolution in optical, ultraviolet and electron-beam lithography into the nanometer region. This paper describes a novel top surface imaging process, which incorporates ion-beam exposure, silylation and dry development, and can support nanometer resolution. The negative resist image by dry etching (NERIME) process is a TSI scheme for DNQ/novolak based resists and can result in either negative or positive resist image depending on the processing conditions. Results show that focused Ga+ ion-beam exposure with a dose in the range of 1-50 µC cm-2 at 30 keV can successfully prevent silylation of the resist, thus resulting in the formation of positive image after the dry etching. A negative image can be formed by using a second ion-beam exposure with a dose higher than 900 µC cm-2 at 30 keV to pattern lines into the original exposed resist area. The NERIME processed patterns down to 0.1 µm have been formed in Shipley SPR505A resist, and exhibit highly vertical sidewalls due to the ion-beam exposure and oxygen dry development. Results show that this novel TSI scheme could be successfully applied for fabrication of critical CMOS process steps, such as deep isolation trench formation and lithography over substantial topography.

Negative resist image by dry etching as a surface imaging process using focused ion beams

Focused ion beam (FIB) lithography has significant advantages over the electron beam counterpart in terms of resist sensitivity, backscattering, and proximity effects. However, combining the FIB lithography with top surface imaging (TSI) will extend its advantages by allowing anisotropic processing of thicker resist layers. This article reports the development of novel single layer lithography process by combining focused Ga+ ion beam (Ga+ FIB) lithography, silylation, and oxygen dry etching. The negative resist image by dry etching is a TSI scheme for DNQ/novolak based resists and can result in either positive or negative resist images depending on the extent of the ion beam exposure dose. Results show that the Ga+ ion beam dose in the range of 1–50 μC/cm2 at 30 keV can successfully prevent silylation of the resist, thus resulting in the formation of a positive image after the dry etching. A negative image can be formed by using a second Ga+ ion beam exposure with a dose higher than 900 μC/cm2 at 30 keV ...

Two-step modified NERIME process using combined focused ion beam lithography and plasma etching

Focused ion beams (FIB) have been widely used as a patterning lithography technique for advanced ICs and optical masks fabrication. FIB lithography has certain advantages over the direct-write electron beam lithography in terms of resist sensitivity, backscattering and proximity effects. However, combining the FIB exposure with both Top Surface Imaging (TSI) and dry etching will further extend its advantages towards anisotropic processing of thicker resist layers in comparison to those used by the conventional lithography processes. The newly developed NERIME (Negative Resist Image by Dry Etching) process combines these advantages by the incorporation of focused Ga+ ion beam (Ga+ FIB) exposure, near UV exposure, silylation and dry etching. The work described here follows our investigations into the NERIME process for nanostructure applications and outlines a simplified (two-step) process incorporating FIB exposure and oxygen dry development. The two-step modified NERIME process is a negative working TSI system for DNQ/novolak based resists. Results show that Ga+ ion beam dose higher than 800μC/cm2 at 30keV can modify the exposed resist areas as to withstand the subsequent oxygen plasma etching, thus giving formation of negative resist image. In this study, nanometer resist patterns as small as 30nm with high aspect ratio of up to 15 were successfully resolved due to the high resolution ion beam exposure and anisotropic dry development. The proposed two-step lithography scheme could be utilized for the fabrication of critical CMOS process steps, such as sub-100nm gate formations and lithography over substantial topography.

Gamma Radiation Sensing Using ZnO and SnO2 Thick Film Interdigitated Capacitors

A novel cost-effective real-time gamma radiation monitoring system based on metal oxide thick films was designed and tested. The changes in capacitances of ZnO and SnO2 thick film capacitors with interdigitated electrodes were monitored in real time under the influence of gamma radiation using miniaturized, low power, bi-directional wireless communication system. The capacitive interface circuitry was based on a Delta-sigma (SigmaDelta) modulator using switched capacitor (SC) circuit architecture with integrated on-chip temperature sensor. At the base station side, an frequency shift keying (FSK) receiver/transmitter is connected to another MCU unit, which send the received data or received instructions from a PC through a graphical user interface GUI. Industrial, scientific and medical (ISM) band RF (433 MHz) was used to achieve half duplex communication between the two sides. All the modules of the mixed signal system are integrated in a printed circuit board (PCB) of size 22.46times20.168 mm. The overall system supply voltage is 2.7 V maximum. 137Cs source with an activity of 370 kBq was used. An increase in the values of capacitance with radiation was recorded for both films to a certain dose level, determined by the material of sensitive layer.

Review of the potential of a wireless MEMS microsystem for biomedical applications

Purpose – Telemetry capsules have existed since the 1950s and were used to measure temperature, pH or pressure inside the gastrointestinal (GI) tract. It was hoped that these capsules would replace invasive techniques in the diagnosis of function disorders in the GI tract. However, problems such as signal loss and uncertainty of the pills position limited their use in a clinical setting. In this paper, a review of the capabilities of microelectromechanical systems (MEMS) for the fabrication of a wireless pressure sensor microsystem is presented.Design/methodology/approach – The circuit requirements and methods of data transfer are examined. The available fabrication methods for MEMS sensors are also discussed and examples of wireless sensors are given. Finally, the drawbacks of using this technology are examined.Findings – MEMS for use in wireless monitoring of pressure in the GI tract have been investigated. It has been shown that capacitive pressure sensors are particularly suitable for this purpose. Se...

Development Of PVDF Thick Film Interdigitated Capacitors For Pressure Measurement On Flexible Melinex Substrates

In this work, a PVDF thick film paste was deposited onto interdigitated electrodes to form a capacitor. Two different substrates, alumina and Melinex® were used. Capacitors, fabricated on alumina substrates were tested as strain gauges, and showed a high sensitivity with low hysteresis. Capacitors on Melinex® substrates were tested as pressure sensors by adhering them to planar and cylindrical surfaces and subjecting them to pressures up to 300 kPa. Their sensitivity and hysteresis during cycling were examined and compared. It was found that sensors on cylindrical surfaces showed a higher sensitivity, however the hysteresis was also increased. It is thought that this is due to instabilities in the polymer film, accentuated by stretching of the substrate.

/spl gamma/-radiation dosimeter using the optical and electrical properties of Al/S/CuPc/Al thin films

Thermally evaporated thin film pn-junctions with a metal/sulfur/copperphthalocyanine/ metal structure were fabricated and the effects of /spl gamma/-radiation on their optical and electrical properties were investigated for the purpose of dosimetry applications. The optical band gap showed slight changes in value when irradiated. The as-deposited and irradiated Al/S/CuPc/Al devices demonstrated Zener diode breakdown under reverse bias voltage and a space-charge-limited conduction mechanism under forward bias. The absorbance, the density of colour centre and Zener breakdown current exhibited a highly consistent linear response to /spl gamma/-radiation exposure. However, the best fit for the experimental data was obtained using the Zener breakdown current for /spl gamma/-ray dose assessment.

Effect of /spl gamma/-rays on the optical and electrical properties of copper-phthalocyanine thick films

Capacitive devices with Ag/CuPc/Ag sandwich structure were fabricated using screen-printing. The effects of /spl gamma/-radiation on their optical and electrical properties were investigated for the purpose of dosimetry applications. The energy values of the optical band gap showed irregular slight increase when the CuPc thick films were irradiated. The as-printed (unexposed to /spl gamma/-rays) and irradiated Ag/CuPc/Ag devices demonstrated a Schottky conduction mechanism. The absorbance and the capacitance of the CuPc thick films exhibited highly consistent linear response to the exposure of /spl gamma/-radiation.

SLITS simulator: modeling and simulation of e-beam/deep-ultraviolet exposure and silylation

The positive resist image by dry etching (PRIME) process is a high-resolution positive resist system incorporating deep-UV (DUV)/e- beam exposure, silylation (gas/liquid phase), and dry development. A new method to calculate the silylation profile in the PRIME process is presented. New software modules have been added to the 2-D simulator SLITS (simulation of lithography on topographic substrates) to simulate the silylation and dry-developed profiles in the PRIME process. The si- Iylation and dry-developed profiles for the PRIME process are simulated and compared to experimental results. Simulations were carried out for both e-beam and DUV exposures. Under e-beam exposure, the maxi- mum percentage error between the simulated and experimental results was 137.. Under DUV exposure, the silylation depth at the mask edge can be reduced by increasing the dose thus effectively controlling the resist linewidth. Subject terms: PRIME process; lithography modeling; nanolithography; silylation; dry development.