The influence of driving frequency on discharge structure and production efficiency has been investigated in Ar over the frequency range from 13.56MHz to l00MHz in terms of the relaxation continuum model. Under constant RF voltage, the plasma density increases in proportion to the square of the driving frequency. The net ionization and excitation rates, and the power density, show the same frequency dependence, although the collisional production efficiency per input power density is almost invariant with change of frequency. This has the great advantage for plasma processing and deposition from plasmas that parallel plate discharge in vety high frequency (VHF) will lead to the system being rather free from ion damage or effects of confined plasma volume as compared with those in high frequency (HF) and microwave (MW).
Al-Si hypoeutectic alloys have excellent castability and sufficient strength in combination with other alloying elements. Especially, Al-Si alloy containing Mg used for high-quality die-casting is well-known as a high strength alloy brought by the appropriate heat treatment and consequential precipitation hardening of Mg 2 Si intermediate phase. T6-heat treatment must be applied for maximum strength, but solution at high temperature and quenching treatment often conduct the product deformation and extra cost for fabrication. Therefore only artificial aging (T5-heat treatment) at comparatively lower temperature is mainly applied to industrial die-casting products. However, there are few studies on age hardening characteristics supplied by T5-heat treatment to Al-Si hypoeutectic alloys. To understand the age hardening behavior of Al-10 mass%Si-0.5 mass%Mg and Al-10 mass%Si-0.8 mass%Mg alloys in detail, microstructure observation and hardness measurement were performed. These alloys quenched in iced water, naturally aged at room temperature and artificially aged at 423-523 K, showed conspicuously age hardening behavior. Age hardening of Al-Si-Mg alloy generally considered to be the main cause of the precipitation-based hardening in phase, nevertheless it was seen that precipitation occurred in -Al+Si eutectic phase. Consequently, from the microstructure observation using SEM, it's thought that the age hardening of these alloys was mainly composed of the hardness change in -Al+Si eutectic phase.
A single-phase diode bridge rectifier with a filter capacitor on the DC side is often employed to convert AC input into a DC voltage. The input current of the rectifier contains harmonic currents which cause undesirable power line effects. Recently, a method using the time domain analysis has been proposed to calculate the harmonic currents of rectifier considering noninfinite capacitance, i.e. non-zero DC side impedance. This method is very accurate, but it requires a long computing time and a complicated algorithm. This paper proposes a new method that makes it possible to easily calculate the harmonic currents taking into account the effects of the AC and DC side impedances of rectifier. The proposed method, which is based on the frequency domain method, can be executed only with the algebraic computation, and its accuracy is quite high. The validity of the proposed method is also demonstrat ed by comparison with the results of time simulation.
A new method of monitoring the two-dimensional uniformity of plasma for semiconductor processing is proposed. This method measures electric potential distribution of the surface of an oxidized Si wafer exposed to plasma using an electrostatic probe array. The O2 and H2 plasmas generated using a reactive ion etching equipment are tested. It is shown that the measured electric potential distribution agrees well with the distribution of plasma parameters measured using a Langmuir probe. A good correlation between the measured plasma nonuniformity and the degradation of gate SiO2 of metal-oxide-silicon (MOS) structure is demonstrated.
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