Abid Iqbal

RF sputtering of polycrystalline (100), (002), and (101) oriented AlN on an epitaxial 3C-SiC (100) on Si(100) substrate

In this paper, the RF sputtering of polycrystalline AlN thin film on epitaxial 3C-SiC(100) on Si(100) substrate is presented. The effect of nitrogen concentration, deposition temperature and sputtering pressure are studied. These parameters are optimized to improve the crystal quality and deposition rate. Nitrogen concentration was varied from 40% to 100%, and it was found that the maximum deposition rate was observed at 40%. The RF bias power on substrate was also varied from 100 to 400 W, and it was observed that the deposition rate increases proportionally. The process temperature was varied from 200 to 400 °C to see the effect on the crystal quality and deposition rate; it was found that temperature variation does not yield significant shifts. This paper is able to demonstrate a successful RF sputtering of a polycrystalline AlN (100), (101), and (002) on epitaxial 3C-SiC(100) using RF power supply of 550 W.

DC sputtering of highly c-axis AlN films on top of 3C-SiC (111)-on-Si (111) substrates under various N2 concentrations

This article reports on the direct current sputtering of AlN thin films on top of a cubic-silicon carbide (111) on silicon (111) substrates. The authors varied the nitrogen (N2) concentrations, while keeping other process parameters fixed at the power of 1200 W, the substrate temperature of 350 °C, the target to substrate distance of 20 cm, and the sputtering pressure of 2 mT. The total N2/Ar gas flow is 50  sccm, and the poison mode starts at 40%. The x-ray diffraction results show that the AlN films are highly oriented along the (002) orientation at various N2 concentrations. The values of the three parameters support this observation, namely, (1) the extracted full width at half maximum (FWHM) of (002) diffraction peaks with the median of 0.28° and the standard deviation of 0.012°, (2) the area of AlN (002) under the curve is between 92% and 97%, and (3) the grain sizes are between 30.11 and 32.3 nm. The omega scan rocking curve of two samples at 40% and 80% N2 concentrations depicts good quality AlN (...

Behavioral modeling of a monolithically integrated three-axis capacitive accelerometer based on the MetalMUMPs process:

In this paper we present behavioral modeling of a monolithically integrated three-axis capacitive accelerometer using the standard MetalMUMPs process. The behavioral modeling is done in order to verify the design with respect to structural and electrostatic performance of the designed three-axis capacitive accelerometer. The proposed accelerometer is 3.2 mm × 3.5 mm in size, designed for sensing the acceleration of 25g in three axes. The mechanical noise floor for in-plane (x and y) and out-of-plane (z) axes is 0.291, 0.316, and 2.84 µg/√ (Hz), respectively. The total sense capacitance along the x, y, and z axes is 68.5 fF, 100 fF, and 6.19 pF, respectively. Sensitivity of 2.568 fF/g, 4 fF/g, and 0.252 pF/g is obtained for in-plane (x and y) and out-of-plane (z) axes, respectively. The resonance frequency for the designed accelerometer is 800 and 2500 Hz for in-plane and out-of-plane axes, respectively. The results obtained by behavioral modeling are compared with the analytical results, which are approximately the same.

The sputtering of AlN films on top of on- and off-axis 3C-SiC (111)/Si (111) substrates at various substrate temperatures

AlN thin films have been sputtered on top of the on-axis and 4° off-axis 3C-SiC (111)/Si (111) substrates at various substrate temperatures. The grazing angle incident XRD scans show that all films have major peak at (002) plane and minor peaks at (101) and (102) planes. The AlN films are further characterized in terms of the FWHM of the rocking curve, surface morphology and deposition rate. We observed that the increasing substrate temperature improve the crystal quality of the AlN (002) films, but it has minimal impact on the surface roughness and deposition rate. We also extracted the values for the bi-axial stress, the grain size and the piezoelectric coefficient. Overall, the off-axis 3C-SiC/Si (111) substrates provide a better template for the sputtering of AlN (002) films in term of better crystal quality, lower surface roughness and lower bi-axial stress.

RF Sputtering, Post-Annealing Treatment and Characterizations of ZnO (002) Thin Films on 3C-SiC (111)/Si (111) Substrates

We report on the radio frequency (RF) sputtering of c-axis oriented ZnO thin films on top of epitaxial 3C-SiC-on-Si (111) substrates, which were then subjected to post-annealing treatment at 400, 600 and 800 °C. Grazing incident X-ray Diffraction (XRD) data show that the Full Width Half Maximum (FWHM) values for O2/Ar ratios between 30% and 60% are consistent, with a mean of 0.325° and a standard deviation of 0.03°. This is largely attributed to the smaller lattice mismatch of 5% between the ZnO (002) and SiC (111) films. The quality of the ZnO films deteriorated at the post-annealing treatment of 800 °C, as demonstrated by the increasing value of FWHM diffraction peaks, the reducing value of the peak intensity, the reducing percentage of (002) oriented area under the curve, and the increasing value of biaxial stress. We propose a simple growth model to explain the result.

Design Optimization and Finite Element Analysis of 3C-SiC Bio-Sensors Based on Dogbone Resonator

This paper presents the optimized design and Finite Element Analysis (FEA) of a bio sensor based on cubic silicon carbide (3C-SiC) for pathogen detection. Silicon Carbide is chosen due to its excellent material properties and chemical stability compared to silicon in varying environmental conditions. The desired resonance frequency is optimized using matlab and the finite element analysis is carried out using COMSOL and Intellisuite software’s. The effect of the residual stress on the desired mode of resonant frequency and the fabrication feasibility of the proposed resonator fabrication are studied using FEA analysis. The mathematical modeling of thermally actuation and piezoresistive sensing for the design resonator bio sensors are illuminated. The close agreement between the analytical model and finite element analysis verify the design of proposed bio sensors.

Reactive Sputtering of Aluminum Nitride (002) Thin Films for Piezoelectric Applications: A Review

We summarize the recipes and describe the role of sputtering parameters in producing highly c-axis Aluminum Nitride (AlN) films for piezoelectric applications. The information is collated from the analysis of around 80 journal articles that sputtered this film on variety of substrate materials, processes and equipment. This review will be a good starting point to catch up with the state-of-the-arts research on the reactive sputtering of AlN (002) thin film, as well as its evolving list of piezoelectric applications such as energy harvesters.

Comparison of seven cantilever designs for piezoelectric energy harvester based On Mo/AlN/3C-SiC

This paper compares the performances of seven different cantilever designs (straight beam, straight-tapered beam, T beam, U beam, V beam, V-T beam and Y beam) to be employed as a piezoelectric energy harvester. All cantilever structures employs the same materials i.e. Aluminium Nitride as piezo layer, Cubic Silicon Carbide as structural layer and Molybdenum as proof mass and electrical electrodes. We use the same thicknesses for these layers for all structures. Their performances are compared in term of resonant frequency, maximum displacement, open-circuit voltage and stress. The results reveal that V-T shaped cantilever beam energy harvester emerges as the overall winner.

MEMS 3-DoF gyroscope design, modeling and simulation through equivalent circuit lumped parameter model

Pre-fabrication, behavioural and performance analysis with computer aided design (CAD) tools is a common and fabrication cost effective practice. In light of this we present a simulation methodology for a dual-mass oscillator based 3 Degree of Freedom (3-DoF) MEMS gyroscope. 3-DoF Gyroscope is modeled through lumped parameter models using equivalent circuit elements. These equivalent circuits consist of elementary components which are counterpart of their respective mechanical components, used to design and fabricate 3-DoF MEMS gyroscope. Complete designing of equivalent circuit model, mathematical modeling and simulation are being presented in this paper. Behaviors of the equivalent lumped models derived for the proposed device design are simulated in MEMSPRO T-SPICE software. Simulations are carried out with the design specifications following design rules of the MetalMUMPS fabrication process. Drive mass resonant frequencies simulated by this technique are 1.59 kHz and 2.05 kHz respectively, which are ...

Design optimization and finite element analysis of AlN/3C-SiC piezoelectric bio-sensors

In this paper we present the design and simulation of a bio-sensor for pathogens detection based on AlN/3C-SiC/Si piezoelectric cantilever. Cubic silicon carbide (3C-SiC) is chosen as the base layer due to its excellent material properties and chemical inertness over silicon in harsh environmental conditions. Aluminum nitride (AlN) is selected as piezoelectric active layer due to its similar thermal expansion coefficient with silicon carbide to reduce thermal stress. The desired resonant frequency of 157.16 KHz is optimized using Matlab and the finite element analysis is carried out using COMSOL software to verify the shift in the resonant frequency due to the added mass of the bacteria. The surface functionalizations of the SiC as biosensor, as well as the fabrication recipes are also proposed.