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Design and analysis framework for trusted and assured microelectronics

Published in:
GOMACTech 2019, 25-28 March 2019.

Summary

An in-depth understanding of microelectronics assurance in Department of Defense (DoD) missions is increasingly important as the DoD continues to address supply chain challenges. Many studies take a "bottom-up" approach, in which vulnerabilities are assessed in terms of general-purpose usage. This is beneficial in developing a general knowledge foundation. However, it does not offer much insight for program managers, technical leads, etc. to determine, for a specific mission and operating environment, the risks and requirements to using a microelectronic device. It is critical to develop a systematic approach that considers mission objectives, as the same component could be used in a weapon system or a surveillance system with significantly different requirements. We have been developing a Trusted and Assured Microelectronics (T&AM) Framework, which considers the entire system life cycle to produce mission-specific metrics and assessments. A radar system exemplar illustrates the approach and how the metric can be used as a Figure of Merit for quantitative analysis during development.
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Summary

An in-depth understanding of microelectronics assurance in Department of Defense (DoD) missions is increasingly important as the DoD continues to address supply chain challenges. Many studies take a "bottom-up" approach, in which vulnerabilities are assessed in terms of general-purpose usage. This is beneficial in developing a general knowledge foundation. However...

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A scalable fabrication process for liquid crystal-based uncooled thermal imagers

Published in:
J. Microelectromech. Syst., Vol. 25, No. 3. June 2016, pp. 479-88.

Summary

A novel sensor is being developed for a new uncooled imager technology that is scalable to large formats (tens of megapixels), which is greater than what is achieved by commercial microbolometer arrays. In this novel sensor, a liquid-crystal transducer is used to change a long-wavelength infrared scene into a visible image that can be detected using a conventional visible imager. This approach has the potential for making a more flexible thermal sensor that can be optimized for a variety of applications. In this paper, we describe the microfabrication processes required to create an array of sealed thermally isolated micro-cavities filled with liquid crystals to be used for an uncooled thermal imager. Experimental results from the fabricated arrays will also be discussed.
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Summary

A novel sensor is being developed for a new uncooled imager technology that is scalable to large formats (tens of megapixels), which is greater than what is achieved by commercial microbolometer arrays. In this novel sensor, a liquid-crystal transducer is used to change a long-wavelength infrared scene into a visible...

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Nanochannel fabrication based on double patterning with hydrogen silsesquioxane

Published in:
J. Vac. Sci. Technol. B, Microelectron. Process. Phenon., Vol. 33, No. 2, March 2015, 020601.

Summary

A double patterning process is presented to pattern sub-35 nm wide channels in hydrogen silsesquioxane with near 100% pattern densities. Using aligned electron beam lithography, each side of the nanochannel structure is patterned as a separate layer. A 50000 uC/cm^2 high-dose anneal is applied to the first layer after exposure. Channels with widths below ~60 nm are shown to exhibit footing with standard tetramethyl ammonium hydroxide developers. This problem is resolved by adding surfectant during the development of the final channel structure. The resulting process produced channels
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Summary

A double patterning process is presented to pattern sub-35 nm wide channels in hydrogen silsesquioxane with near 100% pattern densities. Using aligned electron beam lithography, each side of the nanochannel structure is patterned as a separate layer. A 50000 uC/cm^2 high-dose anneal is applied to the first layer after exposure...

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Switchable electrowetting of droplets on dual-scale structured surfaces

Published in:
J. Vac. Sci. Technol. B, Microelectron. Process. Phenon., Vol. 30, No. 6, November 2012, 06F801.

Summary

The authors report on the development of surfaces containing artificially fabricated structures of dual nanometer and micrometer surfaces that allow an aqueous droplet to be reversibly switched by electrowetting from a Cassie state with low adhesion to a Wenzel state with high adhesion. A variety of geometries were fabricated to study parameters that affect switchable wetting-dewetting. Nanometer parallel corrugations, posts, and holes were fabricated and combined with micrometer features consisting of parallel corrugations, streets, and checkerboard patterns of varying widths and pitches. It was observed that many combinations of the dual-textured surfaces produced superhydrophobic wetting states and aqueous droplets on these surfaces could be electrically controlled to switch from a Cassie state to a Wenzel state. Reversible switching between these wetting states occurred on specific combinations of surface geometries, namely surfaces that had parallel corrugations.
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Summary

The authors report on the development of surfaces containing artificially fabricated structures of dual nanometer and micrometer surfaces that allow an aqueous droplet to be reversibly switched by electrowetting from a Cassie state with low adhesion to a Wenzel state with high adhesion. A variety of geometries were fabricated to...

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SOI circuits powered by embedded solar cell

Published in:
2011 IEEE SOI Conf., 3-6 October 2011.

Summary

Solar cells embedded in the SOI substrate were successfully used as the sole energy source to power a ring oscillator fabricated using an ultra-low-power fully depleted SOI process on the same wafer. The speed of the ring oscillator increased with increasing light intensity and showed a fastest oscillation with a 4.5 ns stage delay and 0.26 fJ power-delay product. The maximum power generated by the solar cell was 9.6 mW/cm2 with an efficiency of 11.6%.
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Summary

Solar cells embedded in the SOI substrate were successfully used as the sole energy source to power a ring oscillator fabricated using an ultra-low-power fully depleted SOI process on the same wafer. The speed of the ring oscillator increased with increasing light intensity and showed a fastest oscillation with a...

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Uniformity study of wafer-scale InP-to-silicon hybrid integration

Published in:
Appl. Phys. A, Mat. Sci. & Process., Vol. 103, No. 1, April 2011, pp. 213-218.

Summary

In this paper we study the uniformity of up to 150 mm in diameter wafer-scale III-V epitaxial transfer to the Si-on-insulator substrate through the O2 plasma-enhanced low-temperature (300°C) direct wafer bonding. Void-free bonding is demonstrated by the scanning acoustic microscopy with sub-um resolution. The photoluminescence (PL) map shows less than 1 nm change in average peak wavelength, and even improved peak intensity (4% better) and full width at half maximum (41% better) after 150 mm in diameter epitaxial transfer. Small and uniformly distributed residual strain in all sizes of bonding, which is measured by high-resolution X-ray diffraction Omega- 2Theta mapping, and employment of a two-period InP-InGaAsP superlattice at the bonding interface contributes to the improvement of PL response. Preservation of multiple quantum-well integrity is also verified by high-resolution transmission electron microscopy.
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Summary

In this paper we study the uniformity of up to 150 mm in diameter wafer-scale III-V epitaxial transfer to the Si-on-insulator substrate through the O2 plasma-enhanced low-temperature (300°C) direct wafer bonding. Void-free bonding is demonstrated by the scanning acoustic microscopy with sub-um resolution. The photoluminescence (PL) map shows less than...

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Epitaxial graphene transistors on SiC substrates

Published in:
IEEE Trans. Electron Devices, Vol. 55, No. 8, August 2008, pp. 2078-2085.

Summary

This paper describes the behavior of top-gated transistors fabricated using carbon, specifically epitaxial graphene on SiC, as the active material. Although graphene devices have been built before, in this paper, we provide the first demonstration and systematic evaluation of arrays of a large number of transistors produced using standard microelectronics methods. The graphene devices presented feature high-k dielectric, mobilities up to 5000 cm2/V · s, and Ion/Ioff ratios of up to seven, and are methodically analyzed to provide insight into the substrate properties. Typical of graphene, these micrometer-scale devices have negligible band gaps and, therefore, large leakage currents.
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Summary

This paper describes the behavior of top-gated transistors fabricated using carbon, specifically epitaxial graphene on SiC, as the active material. Although graphene devices have been built before, in this paper, we provide the first demonstration and systematic evaluation of arrays of a large number of transistors produced using standard microelectronics...

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Orthodox etching of HVPE-grown GaN

Published in:
J. Crystal Growth, Vol. 305, No. 2, July 15, 2007, pp. 384-392 (Proc. of the 4th Int. Workshop on Bulk Nitride Semiconductors IV, 16-22 October 2006).

Summary

Orthodox etching of HVPE-grown GaN in molten eutectic of KOH+NaOH (E etch) and in hot sulfuric and phosphoric acids (HH etch) is discussed in detail. Three size grades of pits are formed by the preferential E etching at the outcrops of threading dislocations on the Ga-polar surface of GaN. Using transmission electron microscopy (TEM) as the calibration tool, it is shown that the largest pits are formed on screw, intermediate on mixed and the smallest on edge dislocations. This sequence of size does not follow the sequence of the Burgers values (and thus the magnitude of the elastic energy) of corresponding dislocations. This discrepancy is explained taking into account the effect of decoration of dislocations, the degree of which is expected to be different depending on the lattice deformation around the dislocations, i.e. on the edge component of the Burgers vector. It is argued that the large scatter of optimal etching temperatures required for revealing all three types of dislocations in HVPE-grown samples from different sources also depends upon the energetic status of dislocations. The role of kinetics for reliability of etching in both etches is discussed and the way of optimization of the etching parameters is shown.
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Summary

Orthodox etching of HVPE-grown GaN in molten eutectic of KOH+NaOH (E etch) and in hot sulfuric and phosphoric acids (HH etch) is discussed in detail. Three size grades of pits are formed by the preferential E etching at the outcrops of threading dislocations on the Ga-polar surface of GaN. Using...

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Impact of photoacid generator leaching on optics photocontamination in 193-nm immersion lithography

Published in:
J. Micro/Nanolith. MEMS MOEMS, Vol. 6, No. 1, January-March 2007, pp. 013001-1 - 013001-7.

Summary

Leaching of resist components into water has been reported in several studies. Even low dissolution levels of photoacid generator (PAG) may lead to photocontamination of the last optical surface of the projection lens. To determine the impact of this phenomenon on optics lifetime, we initiate a set of controlled studies, where predetermined amounts of PAG are introduced into pure water and the results monitored quantitatively. The study identifies the complex, nonlinear paths leading to photocontamination of the optics. We also discover that spatial contamination patterns of the optics are strongly dependent on the flow geometry. Both bare SiO2 surfaces as well as coated CaF2 optics are studied. We find that for all surfaces, at concentrations typical of leached PAG, below 500 ppb, the in situ self-cleaning processes prevent contamination of the optics.
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Summary

Leaching of resist components into water has been reported in several studies. Even low dissolution levels of photoacid generator (PAG) may lead to photocontamination of the last optical surface of the projection lens. To determine the impact of this phenomenon on optics lifetime, we initiate a set of controlled studies...

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Contribution of photoacid generator to material roughness

Published in:
J. Vac. Sci. Technol. B, Microelectron. Process. Phenon., Vol. 24, No. 6, November/December 2006, pp. 3031-3039 (EIPBN 2006, 30 May-2 June 2006).

Summary

The authors have developed an atomic-force-microscopy-based technique to measure intrinsic material roughness after base development. This method involves performing an interrupted development of the resist film and measuring the resulting film roughness after a certain fixed film loss. Employing this technique, the authors previously established that the photoacid generator (PAG) is a major material contributor of film roughness and that PAG segregation in the resist is likely responsible for nanoscale dissolution inhomogeneities. The additional roughness imparted on a test polymer by incorporation of a series of iodonium, sulfonium, diazo, and imido PAGs was measured. The roughness was then correlated to the inhibition properties of the various PAGs. This was accomplished both through a NMR technique that measures interaction of the PAG with the polymer and by evaluating the dissolution inhibition properties of the PAG through a percolation model. Several PAGs that result in significantly lower material roughness and thus the potential for significantly reduced linewidth roughness in resist imaging have been identified.
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Summary

The authors have developed an atomic-force-microscopy-based technique to measure intrinsic material roughness after base development. This method involves performing an interrupted development of the resist film and measuring the resulting film roughness after a certain fixed film loss. Employing this technique, the authors previously established that the photoacid generator (PAG)...

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