Masatoshi Miyake

Effects of Polarization Reversal and Surface Conditions on the Ferroelectric Electron Emission

The electron emission from ferroelectric ceramics has been observed without prepoling. The grid electrodes and the solid electrode are coated on the top and the bottom of a thin lead-zirconate-titanate (PZT) ceramic plate, respectively. The ratio of the interelectrode width to the thickness of the ceramic determines the potential distribution inside the ceramic. With an appropriate ratio, the polarization can be reversed between the grid electrodes. The prepoled PZT ceramic was not essential for the electron emission, because the shape of the waveform of the emission current after prepoling is nearly the same as that obtained without prepoling. However, the peak value of the emission current depends to a large extent on the polarities of the spontaneous polarization and the applied electric field. In addition, the surface condition such as microcracking is as crucial as polarization reversal for the electron emission.

Effects of Mask and Necking Deformation on Bowing and Twisting in High-Aspect-Ratio Contact Hole Etching

The effects of mask characteristics on high-aspect-ratio contact hole (HARC) etching profiles were investigated. The evaluation of etching profiles produced with different taper angle masks confirmed that the bowing amount and mask selectivity worsened with decreasing mask taper angle. The relationship between mask taper angle and distribution of scattered ion flux on the sidewall of a tapered mask was calculated. The scattered ion flux was heavily concentrated in the upper part of the sidewall in the case of a tapered mask, and this was considered to be the main cause of the bowing formation. Direct observation of an etched sidewall by atomic force microscopy (AFM) revealed that the roughness of the necking was strongly related to the roughness of the bottom part of the etched sidewall. To evaluate the dependence of twisting on nonuniform necking, the incident ion flux in a circular hole was calculated. As a result, in the case of nonaxisymmetric necking, an imbalance of ion flux in the bottom of the hole appeared and broke the etching symmetry in the bottom part of the hole, causing twisting. In addition, the probability of twisting was found to increase with increasing necking growth rate irrespective of mask electrification. Therefore, mask deformation and nonuniform necking in the upper part of the sidewall during HARC etching are considered the main factors causing bottom degradation. Accordingly, a vertical and nondeformed mask is very important for a smaller critical dimension (CD) and HARC etching.

High-Temperature Annealing by Subatmospheric-Pressure Radio-Frequency Capacitively Coupled Plasma

High-temperature annealing was performed by a novel annealing system using subatmospheric-pressure radio-frequency capacitively coupled plasma (SAP-CCP). The heating characteristics and stability of discharge were studied. An electrode temperature of 1900 °C was obtained with a stable and uniform glow-like discharge. Also, the characteristics of annealing were investigated using silicon wafers implanted with boron ions accelerated by 5 kV at doses of 2.0×1015 cm-2. The sheet resistance decreased with increasing annealing temperature in the same manner as in conventional rapid thermal annealing. As a result, a sheet resistance of 86 Ω/sq was successfully achieved at an electrode temperature of 1080 °C without any surface roughness.

The generation and application of micro discharge plasmas

Summary form only given. The dielectric barrier discharge lamp has been developed and commercially supplied as a tunable UV light source. However, a high-voltage (over several tens of kilovolts) is required to drive the device. We have attempted to reduce the driving voltages without reducing the light intensity by using new types of micro discharge plasmas, such as, micro-hollow cathode discharge (MHCD) and surface plasma produced by a ferroelectric electron emission (FEE). These plasmas can be driven with a relatively low voltage pulses at atmospheric pressure. We have studied how to generate and operate these micro discharge plasmas as UV excimer light sources.

Bottom profile degradation mechanism in high aspect ratio feature etching based on pattern transfer observation

The hypothetical mechanism of bottom profile degradation, such as distortion and twisting in high aspect ratio feature etching, was verified based on the pattern transfer observation of etched pattern. The authors mainly focused on trench pattern sample to make the investigation easier, that is, direct observation of the sidewall roughness, using an atomic force microscope, as well as analysis of the depth dependence of pattern deformation in high aspect ratio trench etching. Using Fourier transformation analysis for the trench sidewall roughness, it was found that lower spatial frequency component of the masks sidewall roughness is amplified at the bottom region of the trench and that higher spatial frequency component of over 10 μm−1 disappears. However, the higher spatial frequency component is transferred directly to the upper sidewall of the trench. The observation of the pattern deformation profile, as a function of etch depth, revealed that the ratio of line width roughness to line edge roughness ...

The effect of the surface microstructures on the emission characteristics of ferroelectric cathode

Summary form only given. The pulsed electron source using a ferroelectric cathode can easily produce an electron beam of high current density with relatively low driving voltage. The originally proposed mechanism in which the screening electrons captured on the surface of the ferroelectric cathode were pulled away by coulomb potential of spontaneous polarization is not adequate to explain the experimental data. It has been shown that the surface plasma triggered by a reversal of spontaneous polarization is crucial for the electron emission (Shur et al., 1997). Microscopic studies have been conducted from a point of view on the mechanism of ferroelectric electron emission (FEE) under the influence of surface microstructures (Miyake et al., 1997, Zhang et al., 1998). Commercially available disk shaped PZT ceramics of 500 /spl mu/m thickness are used as cathodes. The gold electrodes were deposited; fully solid on the bottom surface and grid electrode of 100 /spl mu/m width and 300 /spl mu/m separations on the top surface. Negative pulsed voltage with the rise time of 100 ns is applied to the bottom surface. The luminescence is always observed whenever the electron emission occurs. The luminescence points are mostly found not on the edge of the grid electrode but on the cutoff points of the grid electrode. After the several shots, many micro cracks are formed near the cutoff points.

Electron emission characteristics form PZT and BaTiO/sub 3/ ceramics cathodes

Summary form only given. Effect of spontaneous polarization on the ferroelectric electron emission (FEE) is investigated by using ferroelectric materials having different value of P/sub s/. G. Rosenman et al. (1993) suggested that the screening electrons can be emitted from the bare surface of ferroelectric materials by changing or reversing P/sub s/ in a short time. On the other hand, Puchkarev et al. (1995) pointed out that the surface plasma plays an important role for the strong electron emission. In this paper, we tried to make this controversy more clear.