A Chrome AR film for Binary Photomasks

A photomask typically consists of a bulk transparent substrate and a thin metallic film with etched pattern on the surface for light absorption. Stray light reflecting off of the top surface of the photomask is especially problematic because it is focused onto the wafer surface, causing unwanted exposure of the photoresist. . Lithographic performance can be significantly improved if this reflection is reduced with an antireflective layer on the top surface of the photomask. There are commercially developed antireflective films for chrome based photomasks. These films were designed to meet certain specifications for optical density and reflectivity. The goal of this project was to develop a process to replicate these commercial films at RIT. X-ray Photoelectron Spectroscopy ~XPS) was performed on the commercial samples to obtain depth profiles of the atomic constituents of the chrome-based films. Absolute reflectivity and transmission data were obtained on these films using a Perkin-Elmer Lamba-11 UV/VIS Spectrophotometer. Finally, a sputter deposition process was developed to deposit a chrome film with bulk properties similar to those of the commercial films. The process was tuned so that the reflectivity of the RIT film closely matched the reflectivity of the commercial films. The result was an antireflective optically dense film appropriate for photomasks for optical lithography

The Urban Origins of Suburban Autonomy by Richardson Dilworth

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97257/1/j.1538-165X.2005.tb01441.x.pd

Does the Supreme Court Matter? Civil Rights and the Inherent Politicization of Constitutional Law

More than a decade ago, in a colloquium sponsored by the Virginia Law Review, scholars of the civil rights movement launched a fierce assault on Michael J. Klarman\u27s interpretation of the significance of the Supreme Court\u27s famous school desegregation ruling in Brown v. Board of Education. Klarman\u27s backlash thesis, initially set forth in a series of law review and history journal articles and now serving as the centerpiece of his new book, revolves around two central claims. First, he argues that the advancements toward racial equality generally attributed to Brown were instead the inevitable products of long-term political, social, and economic transformations that would have undermined Jim Crow regardless of Supreme Court intervention. Second, he credits Brown with a role in this historical process only through a chain of indirect causation: the Supreme Court decision galvanized massive resistance and racial violence in the South, which civil rights activists capitalized upon by engineering televised confrontations that mobilized public opinion across the nation, which created the climate for the passage of the federal civil rights and voting rights legislation of the mid-1960s, which directly and profoundly transformed southern race relations. Although the contours of this general story are part of the standard historical narrative, firmly grounded in the secondary source literature and taught in almost every university classroom, Klarman\u27s specific charge that civil rights scholars have greatly exaggerated the importance of Brown set off a bit of a firestorm. The first wave, which accompanied the 1994 Virginia Law Review article, included not only the expected differences of historiographical analysis but also criticism of a surprisingly personal nature. The response by David J. Garrow, titled Hopelessly Hollow History, ascribed Klarman\u27s views on Brown to the professorial urge for interpretive novelty, which often produces useful advancements but in some unfortunate cases results in revisionist interpretations whose rhetorical excesses are quickly revealed for what they are when old, but indisputable historical evidence, is inconveniently brought back to the pictorial foreground. Garrow highlighted Klarman\u27s failure to acknowledge the direct influence of Brown on the instigation of the 1955 Montgomery [bus] boycott, a causal analysis that emphasizes the crucial inspiration for southern black activists who finally had the moral authority and legal force of the Supreme Court on their side. While conceding Klarman\u27s point that Brown resulted in little school desegregation during the decade after 1954, Garrow blamed the Court itself for emboldening resistance to its decree through the infamous all deliberate speed implementation guidelines known as Brown II. Under this scenario, primary fault for the limited reach of Brown rested in the justices\u27 constrained vision of enforcement rather than in their premature placement of desegregation on the nation\u27s political agenda. In the final sentence of his rejoinder, Garrow dismissed Klarman\u27s entire project with undisguised condescension for the law professor treading on historians\u27 turf: [C]commentators would be well-advised to keep their professional desire for interpretive novelty in check, for rhetorically excessive overstatements and oversimplifications oftentimes do turn out to be hopelessly hollow once a fuller understanding of the historical record is brought to bear

Gray Assist Bar OPC

Assist bar Optical Proximity Correction (OPC) has been demonstrated to increase across pitch performance and depth-of- focus of semi-dense to isolated lines1. As the sub-resolution assist feature (SRAF) or assist bar’s size increases, so does its desired lithographic effect, as well as its undesired printability. In other words, when large assist features are required at isolated pitches, the assist features may print. A frequency-preserving assist bar solution is the most preferred one, but difficult to realize for opaque assist features due to printability. The concept of frequency-preserving Gray Assist Bar OPC has been introduced as a method to extend imaging performance for small features across a wide rage of duty ratios3. In this paper, we will present the experimental validation of this concept. The Gray Assist Bar mask was manufactured using a two-level lithography process, and the optical properties have been characterized using a Woollam VUV VASE system. Additional metrology was performed using an AFM (SNP9000) and CD SEM (KLA8250XR). Exposures on a 0.75NA 193nm scanner clearly show the expected effects. The use of the Gray Assist Bar features reduces the through pitch critical dimension (CD) variations significantly and can hence be regarded as an ‘Optical Proximity Correction’. The isofocal inflection point of aerial images is shifted in cases with Gray Assist Bars, resulting in flatter bossung curves and a larger depth of focus (DOF) for the various features through pitch at their target size. This results in larger overlapping process windows. The Gray Assist Bars has also shown a very low printability, even with aggressive off-axis illumination (OAI) settings

Sensory neuron differentiation is regulated by Notch signaling in the trigeminal placode

AbstractTrigeminal sensory neurons develop from the neural crest and neurogenic placodes, and have been studied as a principal model of sensory neuron formation. While the Notch pathway has been extensively characterized in central nervous system development and other developmental processes, it has not been well characterized in sensory neurogenesis. Here we studied the functional role of Notch signaling in the trigeminal ophthalmic (opV) placode, a prime model of sensory neurogenesis. To establish a good spatiotemporal description of Notch pathway genes in the chick trigeminal placode, a stage-specific expression analysis was conducted, showing that expression of most Notch pathway genes and effectors are expressed in the placode, with expression primarily being confined to ectodermal cells. Expression was highest at stages of peak neuronal differentiation. To test the function of Notch signaling in opV placode cell differentiation, Notch receptor cleavage was blocked using the gamma-secretase inhibitor, DAPT, or signaling was activated by misexpression of the Notch intracellular domain (NICD). Notch activation resulted in a significant reduction in sensory neurogenesis. Cells remained in the ectoderm and did not differentiate. Expression of the opV specification marker Pax3 was also lost in targeted cells. DAPT exposure resulted in a dramatic increase in neurogenesis without increasing proliferation, where many differentiated cells were found in the mesenchyme and, surprisingly, within the ectoderm. This is the first result clearly showing prolific neuronal differentiation in the ectoderm of the trigeminal placodes after experimental manipulation of a molecular signaling pathway, thus identifying Notch signaling as a primary regulator of the sensory neuron fate in the opV placode

Conference of Microelectronics Research 2000

https://scholarworks.rit.edu/meec_archive/1009/thumbnail.jp

Electron Beam Induced Etching

The mechanisms of electron beam induced etching have been studied both experimentally and theoretically. Specifically, a steady-state and a time-dependent continuum model of the process have been developed which uniquely includes the effect of the etch product desorption and diffusion. Both analytical and numerical methods were employed for the modeling, and various experimental designs were used for validation. Initially, a steady-state model was developed to understand an observed so-called “moat” profile which could adequately be described by a finite etch product surface residence time. Subsequently a thorough time-dependent model was written to investigate scanning parameter effects on EBIE. A design of experiments was performed to validate the model and to extract the fundamental parameters for the etching of silica by xenon difluoride. Finally, two technical applications were explored: spontaneous etching passivation on Ta-based extreme ultraviolet lithography masks and carbon nanotube etching

Does the Supreme Court Matter? Civil Rights and the Inherent Politicization of Constitutional Law

More than a decade ago, in a colloquium sponsored by the Virginia Law Review, scholars of the civil rights movement launched a fierce assault on Michael J. Klarman\u27s interpretation of the significance of the Supreme Court\u27s famous school desegregation ruling in Brown v. Board of Education. Klarman\u27s backlash thesis, initially set forth in a series of law review and history journal articles and now serving as the centerpiece of his new book, revolves around two central claims. First, he argues that the advancements toward racial equality generally attributed to Brown were instead the inevitable products of long-term political, social, and economic transformations that would have undermined Jim Crow regardless of Supreme Court intervention. Second, he credits Brown with a role in this historical process only through a chain of indirect causation: the Supreme Court decision galvanized massive resistance and racial violence in the South, which civil rights activists capitalized upon by engineering televised confrontations that mobilized public opinion across the nation, which created the climate for the passage of the federal civil rights and voting rights legislation of the mid-1960s, which directly and profoundly transformed southern race relations. Although the contours of this general story are part of the standard historical narrative, firmly grounded in the secondary source literature and taught in almost every university classroom, Klarman\u27s specific charge that civil rights scholars have greatly exaggerated the importance of Brown set off a bit of a firestorm. The first wave, which accompanied the 1994 Virginia Law Review article, included not only the expected differences of historiographical analysis but also criticism of a surprisingly personal nature. The response by David J. Garrow, titled Hopelessly Hollow History, ascribed Klarman\u27s views on Brown to the professorial urge for interpretive novelty, which often produces useful advancements but in some unfortunate cases results in revisionist interpretations whose rhetorical excesses are quickly revealed for what they are when old, but indisputable historical evidence, is inconveniently brought back to the pictorial foreground. Garrow highlighted Klarman\u27s failure to acknowledge the direct influence of Brown on the instigation of the 1955 Montgomery [bus] boycott, a causal analysis that emphasizes the crucial inspiration for southern black activists who finally had the moral authority and legal force of the Supreme Court on their side. While conceding Klarman\u27s point that Brown resulted in little school desegregation during the decade after 1954, Garrow blamed the Court itself for emboldening resistance to its decree through the infamous all deliberate speed implementation guidelines known as Brown II. Under this scenario, primary fault for the limited reach of Brown rested in the justices\u27 constrained vision of enforcement rather than in their premature placement of desegregation on the nation\u27s political agenda. In the final sentence of his rejoinder, Garrow dismissed Klarman\u27s entire project with undisguised condescension for the law professor treading on historians\u27 turf: [C]commentators would be well-advised to keep their professional desire for interpretive novelty in check, for rhetorically excessive overstatements and oversimplifications oftentimes do turn out to be hopelessly hollow once a fuller understanding of the historical record is brought to bear