Designing Framework For The Computer Aided Design Of Silicon Carbide JFET Circuits In BLEO Environments

Abstract: circuit design and testing are two essential processes to synthesis of an efficient and reliable circuit. Real-time testing of a circuit through circuit fabrication and development is an expensive and a risky procedure whereas testing the circuit by modelling and simulating is more efficient and inexpensive. Silicon-based semiconductors are the basic components of any modern day electronic devices, and their usage has dominated the marketplace. But these conventional cmos devices cannot exist in an environment consisting of harsh radiation, high temperature and many other environmental conditions, such as venus or mars. However, 6h-sic jfets, which are basic logic gate integrated circuits, have significantly potential for persistent operation in these environmental conditions. On the basis of the temperature effects of 6h-sic jfet\u27s compared to conventional cmos jfet\u27s, we choose to develop the framework for a computer aided design of silicon carbide jfet circuits in beyond low earth orbit (bleo) environments. Our framework will help test the modern and emerging nanotechnologies for the temperature dependence of sic electronics and sensors in harsh environments. Framework along with the integrated circuit design and the simulations for the sic electronic circuit are the desired results for this project

Semiconductor Device Modeling and Simulation for Electronic Circuit Design

This chapter covers different methods of semiconductor device modeling for electronic circuit simulation. It presents a discussion on physics-based analytical modeling approach to predict device operation at specific conditions such as applied bias (e.g., voltages and currents); environment (e.g., temperature, noise); and physical characteristics (e.g., geometry, doping levels). However, formulation of device model involves trade-off between accuracy and computational speed and for most practical operation such as for SPICE-based circuit simulator, empirical modeling approach is often preferred. Thus, this chapter also covers empirical modeling approaches to predict device operation by implementing mathematically fitted equations. In addition, it includes numerical device modeling approaches, which involve numerical device simulation using different types of commercial computer-based tools. Numerical models are used as virtual environment for device optimization under different conditions and the results can be used to validate the simulation models for other operating conditions

Single Event Transients in Linear Integrated Circuits

On November 5, 2001, a processor reset occurred on board the Microwave Anisotropy Probe (MAP), a NASA mission to measure the anisotropy of the microwave radiation left over from the Big Bang. The reset caused the spacecraft to enter a safehold mode from which it took several days to recover. Were that to happen regularly, the entire mission would be compromised, so it was important to find the cause of the reset and, if possible, to mitigate it. NASA assembled a team of engineers that included experts in radiation effects to tackle the problem. The first clue was the observation that the processor reset occurred during a solar event characterized by large increases in the proton and heavy ion fluxes emitted by the sun. To the radiation effects engineers on the team, this strongly suggested that particle radiation might be the culprit, particularly when it was discovered that the reset circuit contained three voltage comparators (LM139). Previous testing revealed that large voltage transients, or glitches appeared at the output of the LM139 when it was exposed to a beam of heavy ions [NI96]. The function of the reset circuit was to monitor the supply voltage and to issue a reset command to the processor should the voltage fall below a reference of 2.5 V [PO02]. Eventually, the team of engineers concluded that ionizing particle radiation from the solar event produced a negative voltage transient on the output of one of the LM139s sufficiently large to reset the processor on MAP. Fortunately, as of the end of 2004, only two such resets have occurred. The reset on MAP was not the first malfunction on a spacecraft attributed to a transient. That occurred shortly after the launch of NASA s TOPEX/Poseidon satellite in 1992. It was suspected, and later confirmed, that an anomaly in the Earth Sensor was caused by a transient in an operational amplifier (OP-15) [KO93]. Over the next few years, problems on TDRS, CASSINI, [PR02] SOHO [HA99,HA01] and TERRA were also attributed to transients. In some cases, such events produced resets by falsely triggering circuits designed to protect against over- voltage or over-current. On at least three occasions, transients caused satellites to switch into "safe mode" in which most of the systems on board the satellites were powered down for an extended period. By the time the satellites were reconfigured and returned to full operational state, much scientific data had been lost. Fortunately, no permanent damage occurred in any of the systems and they were all successfully re-activated

Realization of CoFeB|MgO|CoFeB magnetic tunnel junction devices through materials analysis, process integration and circuit simulation

Spin based magnetic tunnel junctions (MTJs) consist of two ferromagnetic thin films separated by a nonmagnetic insulating barrier. The MTJ exhibits two switchable resistive states, making them ideal candidates for non-volatile memory. The discovery of high Tunneling Magnetoresistance (TMR) in MgO based MTJs has brought spintronics into the forefronts of modern technology. A device structure CoFeB|MgO|CoFeB achieved by physical vapor deposition (PVD) has revolutionized the hard-drive industry to go beyond densities of gigabyte per square inch. There is increasing interest in the application of these devices toward other technical areas, such as sensors, logic and reconfigurable computing. In these structures, the thicknesses of the layers are in the order of a few nanometers. For integration of these devices in other platforms, particularly on silicon, to augment the well-developed CMOS technology, it is imperative to (1) investigate processing constraints, (2) develop appropriate physical models, and (3) build circuit models for effective circuit implementation. The work presented in this dissertation focuses on these three important aspects for the realization of CoFeB|MgO|CoFeB MTJs on silicon. A systematic annealing study has been carried out to investigate the role of boron in the device structure. It has been shown using electron energy loss spectroscopy (EELS), and 2D x-ray diffraction (2D XRD) that boron diffuses into MgO with an activation energy of 1.30.4 eV and facilitates the crystallization of CoFe with (200) out-of-plane oriented crystals, with MgO as a template. The grain size of CoFe has been definitively shown to be smaller than the grain size of MgO, which were otherwise believed to be the same. A process temperature of 385°C has been determined to be the optimum limit of processing. A low temperature (\u3c385°C) process employing standard integrated circuit fabrication techniques has been developed. The partial crystallization of CoFe necessitates the modification of the tunneling model. A new model that combines the Julliëre\u27s, free electron and tight-binding model with the probabilistic distribution of grains on either side of the tunneling barrier has been proposed. This model explains the variation of TMR as a function of temperature in devices made by PVD. A generalized circuit macromodel has been developed representing field-switchable magnetic tunnel junctions (MTJs) characterized by two distinct voltage-dependent resistance values in parallel and antiparallel states. General-purpose subcircuit implementations are designed for a switchable voltage-dependent resistor capable of implementation using any version of SPICE. Transient simulation of a flash-comparator circuit using multiple MTJs in series is successfully demonstrated showing the robustness of the model