Feasibility of 50-nm device manufacture by 157-nm optical lithography: an initial assessment

The normalized process latitude (NPL) is used to assess the feasibility of 50-nm device manufacture by 157-nm optical lithography. A first NPL quantification assuming steady improvement of processing technology shows that 157-nm optical lithography is infeasible. A second NPL quantification investigates the amount of technology acceleration required to make 50-nm manufacture possible. It is concluded that photolithography is a viable lithography technique for the 50-nm technology generation only with significant improvements in focus control, photomask making, photoresist contrast, as well as aberration levels.published_or_final_versio

Quantification of image quality

Traditionally, the common window method is used to quantify image quality in optical lithography. The common window method can take dose variation. focus error, mask critical dimension error and aberrations into account. However, the demerit of the common window method is its computation time. In this paper, a new metric called Normalized Process Latitude (NPL) is proposed. The NPL considers dose variation, focus error, mask critical dimension error and aberrations to output its fmal quantification value. Its processing time for quantifying one feature is usually within 10 seconds on a PC with 1GHz CPU and 256MB DRAM. We perform several comparisons between the total window value and the NPL. It is found that the NPL draws similar conclusion as the total window. We can conclude that NPL is a sensible figure ofmerit for image quantification.published_or_final_versio

Doctors' personal health care choices: A cross-sectional survey in a mixed public/private setting

<p>Abstract</p> <p>Background</p> <p>Among Western countries, it has been found that physicians tend to manage their own illnesses and tend not have their own independent family physicians. This is recognized as a significant issue for both physicians and, by extension, the patients under their care, resulting in initiatives seeking to address this. Physicians' personal health care practices in Asia have yet to be documented.</p> <p>Methods</p> <p>An anonymous cross-sectional postal questionnaire survey was conducted in Hong Kong, China. All 9570 medical practitioners in Hong Kong registered with the Hong Kong Medical Council in 2003 were surveyed. Chi-square tests and logistic regression models were applied.</p> <p>Results</p> <p>There were 4198 respondents to the survey; a response rate of 44%. Two-thirds of respondents took care of themselves when they were last ill, with 62% of these self-medicating with prescription medication. Physicians who were graduates of Hong Kong medical schools, those working in general practice and non-members of the Hong Kong College of Family Physicians were more likely to do so. Physician specialty was found to be the most influential reason in the choice of caregiver by those who had ever consulted another medical practitioner. Only 14% chose consultation with a FM/GP with younger physians and non-Hong Kong medical graduates having a higher likelihood of doing so. Seventy percent of all respondents believed that having their own personal physician was unnecessary.</p> <p>Conclusion</p> <p>Similar to the practice of colleagues in other countries, a large proportion of Hong Kong physicians self-manage their illnesses, take self-obtained prescription drugs and believe they do not need a personal physician. Future strategies to benefit the medical care of Hong Kong physicians will have to take these practices and beliefs into consideration.</p

Observation of Van Hove singularities in twisted graphene layers

Electronic instabilities at the crossing of the Fermi energy with a Van Hove singularity in the density of states often lead to new phases of matter such as superconductivity, magnetism or density waves. However, in most materials this condition is difficult to control. In the case of single-layer graphene, the singularity is too far from the Fermi energy and hence difficult to reach with standard doping and gating techniques. Here we report the observation of low-energy Van Hove singularities in twisted graphene layers seen as two pronounced peaks in the density of states measured by scanning tunneling spectroscopy. We demonstrate that a rotation between stacked graphene layers can generate Van Hove singularities, which can be brought arbitrarily close to the Fermi energy by varying the angle of rotation. This opens intriguing prospects for Van Hove singularity engineering of electronic phases.Comment: 21 pages 5 figure

Behavioural Significance of Cerebellar Modules

A key organisational feature of the cerebellum is its division into a series of cerebellar modules. Each module is defined by its climbing input originating from a well-defined region of the inferior olive, which targets one or more longitudinal zones of Purkinje cells within the cerebellar cortex. In turn, Purkinje cells within each zone project to specific regions of the cerebellar and vestibular nuclei. While much is known about the neuronal wiring of individual cerebellar modules, their behavioural significance remains poorly understood. Here, we briefly review some recent data on the functional role of three different cerebellar modules: the vermal A module, the paravermal C2 module and the lateral D2 module. The available evidence suggests that these modules have some differences in function: the A module is concerned with balance and the postural base for voluntary movements, the C2 module is concerned more with limb control and the D2 module is involved in predicting target motion in visually guided movements. However, these are not likely to be the only functions of these modules and the A and C2 modules are also both concerned with eye and head movements, suggesting that individual cerebellar modules do not necessarily have distinct functions in motor control

Simple model of electronic density of states of graphite and its application to the investigation of superlattices

A model of graphite which is easy to comprehend and simple to implement for the simulation of scanning tunneling microscopy (STM) images is described. This model simulates the atomic density of graphite layers, which in turn correlates with the local density of states. The mechanism and construction of such a model is explained with all the necessary details which have not been explicitly reported before. This model is applied to the investigation of rippling fringes which have been experimentally observed on a superlattice, and it is found that the rippling fringes are not related to the superlattice itself. A superlattice with abnormal topmost layers interaction is simulated, and the result affirms the validity of the moiré rotation pattern assumption. The "odd-even" transition along the atomic rows of a superlattice is simulated, and the simulation result shows that when there is more than one rotated layer at the top, the "odd-even" transition will not be manifest. ©2005 The Japan Society of Applied Physics