Seigou Takashima

Behavior of atomic radicals and their effects on organic low dielectric constant film etching in high density N2/H2 and N2/NH3 plasmas

An organic film, FLARE™, is one of the most prospective candidates for interlayer insulating films with low dielectric constants (low k). This organic low k film was etched in inductively coupled high-density plasmas employing N2/H2 and N2/NH3 gases. By changing the mixing ratio of these gases, the anisotropic etching profile was obtained. The etching plasmas were evaluated by quadruple mass spectroscopy and the vacuum ultraviolet absorption spectroscopy employing microplasma as a light source. N and H radical densities were estimated on the order of 1011–1012 cm−3 and 1012–1013 cm−3, respectively. The behavior of etch rate corresponded well to that of H radical density. H radicals were found to be important species for organic low k film etching, while N radicals could not etch without ion bombardments. On the other hand, N radicals were found to be effective for the formation of protection layer on the sidewall against the etching by the H radicals. The ratio of H and N radical densities would be import...

Vacuum ultraviolet absorption spectroscopy employing a microdiacharge hollow-cathode lamp for absolute density measurements of hydrogen atoms in reactive plasmas

We have developed a measurement technique for absolute H-atom densities in process plasmas using vacuum ultraviolet absorption spectroscopy employing a high-pressure microdischarge hollow-cathode lamp (MHCL) as a Lyman α (Lα, 121.6 nm) emission light source. Characterization of the Lα emission-line profile could be simplified by using a high-pressure discharge at about 1 atm. The effect of self-absorption in the MHCL was reduced to an insignificant level by decreasing the H2 partial pressure. The contribution of the collisional broadening to the Lα emission profile was estimated from the saturation characteristics of the absorption intensity when the optical thickness of the plasma was varied. The technique was applied to the measurement of the absolute H-atom density in an inductively coupled H2 plasma.

Measurement and control of absolute nitrogen atom density in an electron-beam-excited plasma using vacuum ultraviolet absorption spectroscopy

The absolute nitrogen (N) atom density in an electron-beam-excited plasma (EBEP) operating at an ultralow pressure has been investigated by vacuum ultraviolet absorption spectroscopy, employing a microdischarge hollow-cathode lamp. The measured N atom density was estimated to be around 6×1011 cm−3, and the dissociation fraction was 4.9% at a N2 pressure of 0.05 Pa, an electron-beam current of 10 A, and an electron-beam acceleration voltage of 120 V. The EBEP potentially enables us to control the electron density and electron energy independently with the electron-beam current and electron-beam acceleration voltages, respectively. It was found that N atom densities increased with increasing electron-beam current and electron acceleration voltage under low-pressure conditions. The EBEP shows great promise as a N atom source operating at an ultralow pressure.

Development of vacuum ultraviolet absorption spectroscopy technique employing nitrogen molecule microdischarge hollow cathode lamp for absolute density measurements of nitrogen atoms in process plasmas

We have developed a vacuum ultraviolet absorption spectroscopy (VUVAS) technique employing a high-pressure nitrogen molecule (N2) microdischarge hollow cathode lamp (N2 MHCL) as a light source of the atomic nitrogen (N) resonance lines for measuring absolute N densities in process plasmas. The estimations of self-absorption and the emission line profiles of the N2 MHCL, which are necessary for absolute N density determination, were carried out. The measurement of absolute N densities have been demonstrated for an inductively coupled N2 plasma using the VUVAS system employing the N2 MHCL.

Absolute concentration and loss kinetics of hydrogen atom in methane and hydrogen plasmas

A measurement technique of the absolute concentration of hydrogen (H) atoms in methane (CH4) and/or hydrogen molecule (H2) plasmas has been established. The H-atom concentration was evaluated by vacuum ultraviolet absorption spectroscopy (VUVAS) using a high-pressure H2 microdischarge hollow cathode lamp (H2-MHCL) as the Lyman α (Lα 121.6 nm) light emission source. A measurement technique of the background absorption caused by species other than H atoms at the Lα line was developed by using the VUVAS technique with the MHCL employing nitrogen molecules (N2-MHCL). The lines around Lα used for the background absorption measurements are 2p23s 4P5/2–2p3 4S3/20 at 119.955 nm, 2p23s 4P3/2–2p3 4S3/20 at 120.022 nm, and 2p23s 4P1/2–2p3 4S3/20 at 120.071 nm of the N atom. By using the VUVAS technique with the MHCLs and subtracting the background absorption from the absorption of H atoms at Lα, we have achieved the measurement of the H-atom concentration in an inductively coupled plasma operated in CH4 and/or H2. T...

Behavior of hydrogen atoms in ultrahigh-frequency silane plasma

We have investigated the behavior of the absolute density of hydrogen (H) atoms in ultrahigh-frequency (UHF), (500 MHz) silane (SiH4) plasma by using a vacuum ultraviolet absorption spectroscopy technique with a microdischarge hollow cathode lamp. In the UHF plasma using SiH4 highly diluted with hydrogen molecule (H2) at a pressure of 20 Pa, an UHF power of 1000 W, and a total flow rate of 200 sccm, the absolute density of H atoms slightly increased from 7.4×1011 to 7.9×1011 cm−3 with increasing the SiH4 flow rate ratios from 0% to 2.5% and then the H atom density decreased at the ratio of 5%. The decrease of the density is due to the increase of the reaction between the H atom and the SiH4 molecule. The behavior of the absolute density of H atoms was compared with that of the Balmer α(Hα) emission intensity. It was found that the behaviors of the absolute H atom density and the Hα emission intensity were quite different. Moreover, the kinetics of H atom density in SiH4 plasmas have been clarified on the ...

Investigation of Nitrogen Atoms in Low-Pressure Nitrogen Plasmas Using a Compact Electron-Beam-Excited Plasma Source

We developed a new compact electron-beam-excited plasma (EBEP) source with a multihole grid. The source can be reliably operated under low-pressure conditions by controlling the electron-beam current and electron-beam energy independently. In this study, we applied the compact EBEP source to the generation of nitrogen plasma. The absolute nitrogen (N) atom densities in the plasma were evaluated using vacuum ultraviolet absorption spectroscopy (VUVAS) with a high-pressure microdischarge hollow cathode (MHCL) as a light source. The electron density and electron temperature were measured using a Langmuir probe. The behavior of N atom densities and electron densities in the plasma are discussed.

Growth of Preferentially Oriented Microcrystalline Silicon Film Using Pulse-Modulated Ultrahigh-Frequency Plasma

Microcrystalline silicon films were formed on glass substrate at 300°C using pulse-modulated ultrahigh-frequency plasma, with variation of the pulse duty ratio (10–100%) and the pulse frequency (2–50 kHz). We found that the ratio of (111) to (220) crystalline orientation of films can be precisely controlled by changing the duty ratio or frequency. Variation in crystalline orientation closely correlated with the ratio of silicon atom density to hydrogen atom density in the plasma. Strongly preferential (111) growth was achieved, and we propose that the mechanism for this involves the ratio between silicon species and hydrogen atoms in the pulse-modulated plasma.

Diagnostics of Plasma Induced Damages on Low-k SiOCH Films

Department of Electrical Engineering and Computer Science, Nagoya University. Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan Phone: +81-52-789-3461 E-mail: takasima@nuee.nagoya-u.ac.jp Plasma Nanotechnology Research Center, Nagoya University. Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan 3 Process Technology Department, Semiconductor Technology Development Division, Semiconductor Business Group, Sony Corporation, 4-14-1 Asahi-cho, Atsugi-shi, Kanagawa 243-0014, Japan JST-CREST, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan