A review of problems in pattern fabrication technologies using ultra-violet photolithography and electron-beam lithography is given from the standpoint of application to LSI fabrication. For ultra-violet photolithography, comparison of contact and projection printing, pattern registration accuracy and defects of positive resist pattern are discussed. Electron-beam litho-graphy is discussed, where stability of scanning electron beam exposure system, drawing po-sition accuracy, electron resists characteristics and application to mask fabrication and direct wafer exposure are included.
In the wide range of temperature, 45K to 350K, the thermally stimulated currents in anthracene single crystals are measured by the new method, which we have proposed previously. In this paper, we discuss generally the shallow trapping centers which are observed between 45K and 220K (at heating rate β_??_0.06 K/sec). Complicated curve of thermally stimulated currents, which consists of several peaks, can, be observed in this temperature range. These experimental results suggest a discrete, rather than a continuous, distribution of trapping centers. About ten of these trapping levels have been separated successfully through a thermal cleaning technique and their energy depths are valued at about 0.03_??_0.34 eV. It is shown that the present results are not contradictory to the previously reported results, and furthermore, make it possible to advance a further step towards the understanding of trapping centers, because energy gaps not reported in previous results are covered by the present results.
Frequency stability of methane stabilized lasers was estimated with Allan variance which is a measure of stability in the time domain. Power spectrum density in the frequency domainn was obtained from the beat frequency fluctuation between two lasers. The spectra corresponded to several variation components which can be referred to ambient conditions of the lasers such as temperature, ground born vibration, mechanical vibration and sound. The contribution of each laser to the beat frequency fluctuation was estimated from error signals of laser frequency control systems with spectrum analysis technique. The stability analysis in the frequency domain has been found to be more effective for the improvements of lasers.
The two to three longitudinal mode oscillations from a conventional internal mirror laser with 1_??_2mW output power is degenerated to a single mode by the application of a transverse magnetic field, and then stabilized by cooling the laser tube with a fan driven by a servo system referring to the state of polarization of the output light. The optimum magnetic flux density Bz required to degenerate the longitudinal mode is inversely proportional to the cavity length L (m) of the laser, and is approximately given as Bz=c/2×1.4×106gL [Gauss] c: light velocity [m/sec] g: Lande's factor The frequency stabilization of the system was estimated from the fluctuation of the unbalance signal to be 1.9×10-8