An inductively coupled plasma source with an internal straight antenna was developed. By inserting an antenna into plasma, the induction of a strong electric field in the plasma and the efficient transmissions of power to plasma is enabled. However, there was a practical problem in that antenna sputtering occurred. Suppression of antenna sputtering and methods of insulating the antenna were studied. Consequently, it was found that sputtering impurities were reduced by covering the straight antenna with a quartz pipe. Furthermore, the amount of quartz pipe etching could be reduced to as little as 1/10th the original value. As a result of fabricating and evaluating the plasma source in which four straight antennas were arranged in parallel, electron density was determined to be as high as 1011 cm-3 even at a pressure as low as 4 mTorr. When the processing performance of the plasma source was evaluated, the ashing rate of the photoresist and the etching rate of the poly-Si were, respectively, 4.8 µm/min and 450 nm/min. These values are at practically applicable levels.
A strong anomaly of the single Langmuir probe characteristics has been observed in detached recombining plasmas, where the conventional analysis of the probe characteristics gives us a considerably high electron temperature compared with the value determined with the spectroscopic methods. We discuss the reason why such characteristics are obtained in terms of the temperature gradient along the magnetic field associated with the parallel electron transport. Moreover, the validity of the probe measurements in the detached recombining plasmas by using multiple electrodes is also discussed.
We developed a stable and uniform large-area plasma source using surface waves generated from a slot antenna. The propagation of microwaves radiating from the slot antenna was studied and the optimal shape of the slot antenna for uniform plasma generation was determined. The characteristics of a dry etching process using the plasma were also evaluated. It was confirmed that some of the microwaves which radiated from the slot antenna propagate as surface waves in the dielectric window. By adjusting the angle of the slot antenna, the plasma was generated in the direction perpendicular to the axis of the slot antenna. An Ar plasma electron density of the order of 1011/cm3, which exceeds the electron density required for blocking the propagation of microwaves (cutoff frequency), was obtained. On the basis of these observations, it was considered that the microwaves radiating from the slot antenna propagate in the form of surface waves in the direction perpendicular to the axis of the slot antenna, and generate surface-wave plasma. The results of the measurements of the etching rate and ashing rate yielded a poly-Si etching rate of 470 nm/min or greater with a uniformity of 5% or better, and an ashing rate of 3000 nm/min or greater with a uniformity of 7% or better. The poly-Si etching rate was approximately twofold and the ashing rate was approximately fivefold the corresponding values obtained by the conventional chemical dry etching method.
We propose to describe the dynamics of unstable particles in relativistic quantum field theory in terms of semigroups of transformations of the observables. This leads, in contrast to the usual Hilbert space level treatment, to a complete and consistent description of the irreversible dynamics of decay processes. The scheme is explicitly worked out for the massive scalar quantum field and the evolution of the particle density and its higher moments is computed.
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