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Characterizations of Mo/Si multilayers for soft X-ray mirrors have been carried out by high-resolution transmission electron microscopy (TEM) and X-ray scatterings. The crystallite size of oriented Mo in the direction normal to the (110) plane has been found to be approximately equal to the designed thickness of the Mo layer below 8 nm. However, when the Mo layer thickness becomes greater than 8 nm, the crystallite size deviates from the designed thickness and saturates at about 10 nm. The Si layer thickness is smaller than the expected one, which is calculated from the periodic length and the Mo layer thickness, indicating that the mixed layer at the interface is formed in the Si layer. The thickness and density of the mixed layer at the Mo-on-Si interface are larger than those at the Si-on-Mo interface. The sum of the thicknesses of the mixed layer is about 1.4 nm, irrespective of the Mo/Si composition. Moreover, the density of the mixed layer at the Mo-on-Si interface becomes larger with the increase of the Mo content.

The effect of reduction of the electron shading charge buildup using pulsed microwave plasma was evaluated. The gate oxide voltage due to the electron shading effect was measured directly using a charging current measurement electrode on which a Si chip with a line-and-space (L&S)-patterned photoresist was mounted. The ratio of the electron saturation current to the ion saturation current (Ies/Iis ratio) in the open area and in the L&S area were also measured. In continuous wave (CW) plasma, the Ies/Iis ratio in the open area was larger than that in the L&S area, which causes the electron shading charge buildup. In pulsed plasma, the Ies/Iis ratio in the open area is equal that in the L&S area during the off-time period. This is the mechanism of the reduction of the electron shading effect by using pulsed plasma.

High-frequency measurements of plasma parameters used in circuit model simulation were carried out to analyze charging damage. The bulk plasma impedance was measured by varying the bias voltage of probes with an impedance analyzer. The sheath condenser and the sheath diode characteristics were derived by fitting parameters in such a way that current–voltage (I–V) Lissajous' waveforms in the simulation agree with those in the measurement obtained using one spherical probe. The accuracy of the circuit model simulation improved by introducing the correction coefficients of the plasma parameters, which were derived by comparison between the calculated value and the measured one. Therefore, the circuit model simulation results agreed closely with the experimental results obtained using a charging damage measurement electrode. Both methods are effective for investigating the reduction of charging damage, in particular, of the etcher used for 12 inch wafers.

The effect of Push–Pull bias (phase-controlled bias) on the plasma potential and sputtering at the chamber-wall was investigated. It was found that the plasma potential could be controlled unrelated to the geometrical configuration of the chamber by using phase-controlled bias. The reason is that by using phase-controlled bias in the plasma with a magnetic field, the earth function of both electrodes facing each other can be controlled. Specifically, with the phase difference set to 180 degrees, the plasma potential was minimized and the decreased energy of incident ions to the chamber-wall reduced sputtering at the chamber-wall. Therefore, a stable process performance without particles caused by a sputtering at the chamber-wall, was expected by using Push-Pull bias in the dielectric UHF-ECR etching system.

Concentric spread plasma (CSP) is a new type of surface-wave-excited plasma that is disc-shaped and that expands concentrically with increasing microwave power. This study compares the results obtained experimentally with those obtained by three-dimensional electromagnetic wave simulations taking into account the energy absorbed by the plasma. It is shown here that at pressures above 100 Pa, the plasma is produced and sustained by Joule heating.

A charging damage measurement electrode was used to model device structures. The charge passed through gate-oxide films (Q p) was measured in a cavity-resonator-type electron cyclotron resonance (ECR) plasma etcher for 12-inch wafers and the reduction of charging damage was investigated. Parallel circuits composed of resistors and condensers were modeled after the current–voltage (I–V) characteristics of the gate-oxide film. The electron shading effect was introduced by mounting a Si chip with line and space (L&S)-patterned photoresist on the probe, which corresponded to the gate electrode. The reduction of charging damage using the time modulation (TM) bias was determined by evaluating Q p and the damaged test element group (TEG) wafer. This charging damage measurement electrode is effective for investigating the reduction of charging damage in particular, of the etcher used for 12-inch wafers.

A new compact electron cyclotron resonance (ECR) plasma source, which is termed slant-slot antenna-type ECR plasma source, is presented. Using this plasma source an ion saturation current density I is of 6.2 mA/cm2±5.2% was obtained over a diameter of 300 mm under ambient conditions of Cl2 gas at 0.7 Pa. The features of the plasma source are an independent circular TM011 mode cavity resonator and slot antennas mounted in the shape of a ring at a constant slant angle to the surface current flowing at the bottom of the cavity resonator. As the result, microwaves of TE01 mode and others having a ring-shaped the electric field distribution can be introduced into the reaction chamber with high stability. This plasma source can generate a plasma with a ring-shaped I is distribution stably, and it can control the I is distribution by means of both the configuration of the magnetic field and the pattern of slot antennas. Therefore, the plasma source can generate a uniform plasma under a wide range of discharge conditions.

A large-diameter unmagnetized argon plasma is generated by an Okamoto cavity operated in a surface-wave mode. A quartz discharge tube (16 cm inner diameter, 12 cm long) is placed inside the cavity. An argon plasma is produced in the discharge tube and effuses in a process chamber. The electron density, electron temperature, ion current density and floating potential in the chamber are measured as a function of spatial position using a Langmuir probe. An electron density over 1011 cm-3, with an electron temperature in the range of 2–3 eV and a floating potential with respect to the chamber wall of less than 5 V is obtained at pressure in the mTorr range with 2.45 GHz, 700 W input microwave power. A high ion current density (over 10 mA/cm2) of uniformity (standard deviation/average) within 4.4% over 16 cm is achieved.

We have developed an apparatus that can measure the three-dimensional distribution of microwave electric field intensity in electron cyclotron resonance (ECR) plasmas. The reflection edge of the incident microwaves depends on the plasma density in the etching chamber: it is the ECR zone when the electron density (n e) is above 1×1011 cm-3 and the electrode when n e is below 1×1011 cm-3. The spatial distribution of the ion saturation current density at the electrode is the same as that of the microwave electric field intensity at the ECR zone. Therefore, in order to obtain uniform ion saturation current density, the intensity of the microwave electric field at the ECR zone must be kept uniform.

The relationship between the plasma uniformity and the microwave electric field was investigated for various levels of microwave power by introducing only the dominant-mode microwave: either the circular TE11 mode or the rectangular TE10 mode. The plasma uniformity was found to change in three stages according to the electron density depending on the microwave transmission characteristics in the plasma. The fluctuations of the plasma emission were also investigated in several types of discharges. A fixed spatial distribution of the microwave electric field was found to be effective for stabilizing the plasma. The high-density plasma above 1×1011 cm-3 was found to be more stable.

A method for 2-D measurement of microwave electric field distribution using thermal sensitive paper has been developed. This measurement method has little influence on the microwave propagation and the plasma generation. In a cavity-resonator microwave plasma generation system, the relationship between the plasma uniformity and the microwave electric field distribution was investigated using this method. The cavity-resonator microwave plasma source was found to generate high-density plasma stably and uniformly over a large area through the excitation of a ring-shaped microwave electric field in the cavity resonator.

Barium ions in a preformed anode plasma were collectively accelerated up to a peak energy of 270 MeV (2.0 MeV/amu) using an electron beam pulse with peak energy of about 0.4 MeV, peak diode current 16 kA and pulse-width of 10 ns (FWHM).

Photolytic etching of polycrystalline silicon has been investigated in an SF6 atmosphere. SF6 molecules were excited by one-photon absorption under D2 lamp irradiation. This reaction was found to have high reaction-efficiency, 130 nm/Jcm-2. The distribution of the etch rate in the sample was remarkably influenced by the gas flow. This reaction was thus caused by photo-excitation of SF6 molecules in atmosphere, and not by that of absorbed SF6 molecules over a polycrystalline silicon surface.