Nanomagnetic devices are highly energy efficient and non-volatile. Because of these two attributes, they are potential replacements to many currently used information processing technologies, and they have already been implemented in many different applications. This dissertation covers a study of nanomagnetic devices and their applications in various technologies for information processing – from simulating and analyzing the mechanisms behind the operation of the devices, to experimental investigations encompassing magnetic film growth for device components to nanomagnetic device fabrication and measurement of their performance. Theoretical sections of this dissertation include simulation-based modeling of perpendicular magnetic anisotropy magnetic tunnel junctions (p-MTJ) and low energy barrier nanomagnets (LBM) – both important devices for magnetic device-based information processing. First, we propose and analyze a precessionally switched p-MTJ based memory cell where data is written without any on-chip magnetic field that dissipates energy as low as 7.1 fJ. Next, probabilistic (p-) bits implemented with low energy barrier nanomagnets (LBMs) are also analyzed through simulations, and plots show that the probability curves are not affected much by reasonable variations in either thickness or lateral dimensions of the magnetic layers. Experimental sections of this dissertation comprise device fabrication aspects from the basics of material deposition to the application-based demonstration of an extreme sub-wavelength electromagnetic antenna. Magnetic tunnel junctions for memory cells and low barrier nanomagnets for probabilistic computing, in particular, require ultrathin ferromagnetic layers of uniform thickness, and non-uniform growth or variations in layer thickness can cause failures or other problems. Considerable attention was focused on developing methodologies for uniform thin film growth. Lastly, micro- and nano-fabrication methods are used to build an extreme sub-wavelength electromagnetic antenna implemented with an array of magnetostrictive nanomagnets elastically coupled to a piezoelectric substrate. The 50 pW signal measured from the approximately 250,000-nanomagnet antenna sample was 10 dB above the noise floor.

This thesis describes an experimental study and modeling of the current-transconductance dependence of the ALD1106, ALD1107, and CD4007 arrays. The study tests the hypothesis that the I-gm dependence of these 7.8 µm to 10 µm MOSFETs conforms to the Advanced Compact Model (ACM). Results from performed measurements, however, do not support this expectation. Despite the relatively large length, both ALD1106 and ALD1107 show sufficiently pronounced ‘short-channel’ effects to render the ACM inadequate. As a byproduct of this effort, we confirmed the modified ACM equation. With an m factor of approximately 0.6, it captures the I-gm dependence with sub-28% maximum error and sub-10% average error. The paper also introduces several formulas and procedures for I-gm model extraction and tuning. These are not specific to the ALD transistor family and can apply to MOSFETs with different physical size and electrical performance.

A millimeter-wave (W-Band) down-converter for Phased Focal Plane Arrays (PFPAs) has been designed and fabricated using the IBM Silicon-Germanium (SiGe) BiCMOS 8HP process technology. The radio frequency (RF) input range of the down-converter chip is from 70 95GHz. The intermediate frequency (IF) range is from 5 30GHz. The local oscillator (LO) frequency is fixed at 65GHz. The down-converter chip has been designed to achieve a conversion gain greater than 20dB, a noise figure (NF) below 10dB and input return loss greater than 10dB. The chip also has novel LO circuitry facilitating LO feed-through among down-converters chips in parallel. This wide bandwidth down-converter will be part of millimeter-wave PFPA receiver designed and fabricated in collaboration with the University of Massachusetts-Amherst Department of Astronomy. This PFPA receiver will be installed on Green Bank Telescope (GMT) / Large millimeter wave telescope (LMT) in Q2 of 2014. This project is collaboration between the University of Massachusetts-Amherst (UMass), Brigham Young University (BYU) and National Radio Astronomy Observatory (NRAO). To the best of the author’s knowledge, this is first wide bandwidth down-converter at W-band to achieve this high gain and low noise figure among Si/SiGe based systems.

Optical Proximity Correction (OPC) is a part of a family of techniques called Resolution Enhancement Techniques (RET). These techniques are employed to increase the resolution of a lithography system and improve the quality of the printed pattern. The fidelity of the pattern is degraded due to the disparity between the wavelength of light used in optical lithography, and the required size of printed features. In order to improve the aerial image, the mask is modified. This process is called OPC, OPC is an iterative process where a mask shape is modified to decrease the disparity between the required and printed shapes. After each modification the chip is simulated again to quantify the effect of the change in the mask. Thus, lithography simulation is an integral part of OPC and a fast lithography simulator will definitely decrease the time required to perform OPC on an entire chip. A lithography simulator which uses wavelets to compute the aerial image has previously been developed. In this thesis I extensively modify this simulator in order to execute it on a Graphics Processing Unit (GPU). This leads to a lithography simulator that is considerably faster than other lithography simulators and when used in OPC will lead to drastically decreased runtimes. The other work presented in the proposal is a fast OPC tool which allows us to perform OPC on circuits faster than other tools. We further focus our attention on metrics like runtime, edge placement error and shot size and present schemes to improve these metrics.

Carbon nanotubes (CNTs) are promising nanomaterials for high frequency applications due to their unique physical characteristics. CNTs have a low heat capacity, low intrinsic capacitance, and incredibly fast thermal time constants. They can also exhibit ballistic transport at low bias, for both phonons and electrons, as evident by their fairly long mean free paths. However, despite the great potential they present, the RF behavior of these nanostructures is not completely understood. In order to explore this high frequency regime we studied the microwave (MW) and terahertz (THz) response of individual and bundled single wall nanotube based devices. This thesis is an experimental study which attempts to understand the high frequency characteristics of metallic single walled carbon nanotubes, and to develop an ultra-fast and sensitive direct THz detector. First, the appropriate high frequency detector background is introduced. CNTs previously measured behavior draws similarities to two types of detectors: diode and bolometer. Therefore, our CNT devices are geared towards those designs. Second the fabrication process of devices is reviewed. UV lithography is used to pattern THz coupling log periodic antennas, on top of which CNTs are deposited by using a dielectrophoretic process. Third, the fabricated devices are tested at DC, MW, and THz frequencies. All of these measurements are done as a function of temperature, power, and frequency. Finally, the physical processes that give rise to the diode and bolometric detections at MW and THz detection at different temperatures and under different bias regimes (i.e. low and high) are explained.

Modern semiconductor manufacturing requires photolithographic printing of subillumination wavelength features in photoresist via electromagnetic energy scattered by complicated photomask designs. This results in aerial images which are subject to constructive and destructive wave interference, as well as electromagnetic resonances in the photomask features. This thesis proposes a 3-D full-wave frequency domain nonconformal Octree mesh based Finite Element Method (OFEM) electromagnetic scattering solver in combination with Fourier Optics to accurately simulate the entire projection photolithography system, from illumination source to final image intensity in the photoresist layer. A rapid 1-irregular octree based geometry model mesher is developed and shown to perform remarkably well compared to a tetrahedral mesher. A special set of nonconformal 1st and 2nd order hierarchal OFEM basis functions is presented, and 1st order numerical results show good performance compared to tetrahedral FEM. Optical and modern photomask phenomenology is examined, including optical proximity correction (OPC) with thick PEC metal layer, and chromeless phase inversion (PI) masks.

Metasurfaces are arrays of subwavelength meta-atoms that shape waves in a compact and planar form factor. During recent years, metasurfaces have gained a lot of attention due to their compact form factor, easy integration with other devices, multi functionality and straightforward fabrication using conventional CMOS techniques. To provide and evaluate an efficient metasurface, an optimized design, high resolution fabrication and accurate measurement is required. Analysis and design of metasurfaces require accurate methods for modeling their interactions with waves. Conventional modeling techniques assume that metasurfaces are locally periodic structures excited by plane waves, restricting their applicability to gradually varying metasurfaces that are illuminated with plane waves. In this work, we will first provide a novel technique that enables the development of accurate and general models for 1D metasurfaces. This approach can be easily extended to 2D metasurfaces. Due to the remarkable importance of accurate characterization of metasurfaces, we will provide a rigorous method to characterize 1D metasurfaces. Finally, we will provide an accurate approach to fabricate and characterize 2D metasrufaces.

Gold wire bonding typically uses 60 KHz ultrasonic frequency. Studies have been reported that increasing ultrasonic frequency from 60KHz to 120KHz can decrease bonding time, lower bonding temperature, and/or improve the bondability of Au metalized organic substrates. This thesis presents a systematic study of the effects of 120 KHz ultrasonic frequency on the reliability of fine pitch gold wire bonding. Two wire sizes, 25.4 and 17.8 μm in diameter (1.0 and 0.7 mil, respectively) were used. The gold wires were bonded to metalized pads over organic substrates with five different metallization. The studies were carried out using a thermosonic ball bonder that is able to easily switch from ultrasonic frequency from 60 KHz to 120 KHz by changing the ultrasonic transducer and the ultrasonic generator. Bonding parameters were optimized through design of experiment methodology for four different cases: 60 KHz with 25.4 μm wire, 60 KHz with 17.8 μm wire, 120 KHz with 25.4 μm wire, and 120 KHz with 17.8 μm wire. The integrity of wire bonds was evaluated by the wire pull and the ball bond shear tests. With the optimized bonding parameters, over 2,250 bonds were made for each frequency and wire size. The samples were then divided into three groups. The first group was subjected to temperature cycling from -55°C to +125°C with one hour per cycle for up to 1000 cycles. The second group was subject to thermal aging at 125°C for up to 1000 hours. The third group was subject to humidity at 85°C/85% relative humidity (RH) for up to 1000 hours. The bond integrity was evaluated through the wire pull and the ball shear tests immediately after bonding, and after each 150, 300, 500, and 1000 hours time interval in the reliability tests. The pull and shear data are then analyzed to compare the wire bond performance between different ultrasonic frequencies.

As the transistor count per chip in computer microprocessors surpasses one billion, the semiconductor industry has become more and more concerned with meeting processor’s power requirements. This poses a design challenge for the power supply module, especially when the processor operates at low voltage range. For example, the electrical requirement for the newest Intel microprocessors has exceeded 100A with an input voltage of approximately 1V. To overcome this problem, multiphase DC-to-DC converters encased in a voltage regulator module (VRM) have become the standard means of supplying power to computer microprocessor. This study proposes a new topology for the multiphase DC-to-DC converter for powering microprocessors. The new topology accepts 12 V input, and outputs a steady state voltage of 1 V with a maximum output current of 40 A. The proposed topology aims to improve the input and output characteristics of the basic multiphase “buck” converter, along with an improved efficiency, line regulation, and load regulation. To explore the feasibility of such a topology, open-loop computer simulation and closed-loop hardware tests were performed. On open-loop simulation, OrCad pspice was used to verify design calculations and evaluate its performance. Then the closed-loop hardware prototype was tested to compare the circuit performance with those values obtained from simulation. The result shows the proposed topology improvement of efficiency, board size, output ripple, and regulations.

In the last 15 years, an immense amount of research has gone into developing high efficiency Gallium Nitride based light emitting diodes (LED). These devices have become increasingly popular in LED displays and solid state lighting. Due to the large difference in refractive index between GaN and Air, a significant amount of light reflects at the boundary and does not escape the device. This drawback decreases external quantum efficiency (EQE) by minimizing light extraction. Scientists and engineers continue to develop creative solutions to enhance light extraction. Some solutions include surface roughening, patterned sapphire substrates, and reflective layers. This study proposes to increase external quantum efficiency and optimize light extraction efficiency of several LED structures using finite difference time domain analysis (FDTD). The structures under investigation include GaN based LEDs with nanoscale top gratings, patterned sapphire substrates in combination with SiO2 nanorod arrays, and reflective surfaces below and above the sapphire substrate. First, we optimize GaN based nanoscale top gratings and increase light extraction by 17.8%. Next, we simulate ITO based top gratings and enhance light extraction by 40%. Third, we optimize patterned sapphire substrate period and width and the vertical position of a SiO2 nanorod array. We achieve as high as 51.8% improvement in light extraction. Finally, we increase light extraction by 160% with the use of a silver reflection layer.