• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1734-1737
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• 2015

Insulating characteristics of Cl₂-He mixture gases in gas discharges were analysed to evaluate ability of these gases for using in medium voltage and many industries. These are electron transport coefficients, which are the electron drift velocity, density-normalized longitudinal diffusion coefficient, and density-normalized effective ionization coefficient, in Cl₂-He mixtures. A two-term approximation of the Boltzmann equation was used to calculate the electron transport coefficients for the first time over a wide range of E/N (ratio of the electric field E to the neutral number density N). The limiting field strength values of E/N, (E/N)_lim, for these binary gas mixtures were also derived and compared with those of the pure SF₆ gas.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.65-65
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• 1999

Dry etching technique provides more easy controllability on the etch profile such as anisotropic etching than wet etching process and the results of lots of researches on the characterization of various plasmas or ion beams for semiconductor etching have been reported. Chlorine-based plasmas or chlorine ion beam have been often used to etch several semiconductor materials, in particular Si-based materials. We have studied the effect of He flow rate on the Si and SiO2 dry etching using chlorine-based plasma. Experiments were performed using reactive ion etching system. RF power was 300W. Cl2 gas flow rate was fixed at 58.6 sccm, and the He flow rate was varied from 0 to 120 sccm. Fig. 1 presents the etch depth of si layer versus the etching time at various He flow rate. In case of low He flow rate, the etch rate was measured to be negligible for both Si and SiO2. As the He flow increases over 30% of the total inlet gas flow, the plasma state becomes stable and the etch rate starts to increase. In high Ge flow rate (over 60%), the relation between the etch depth and the time was observed to be nearly linear. Fig. 2 presents the variation of the etch rate depending on the He flow rate. The etch rate increases linearly with He flow rate. The results of this preliminary study show that Cl2/He mixture plasma is good candidate for the controllable si dry etching.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.169-175
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• 1998

The plasma etching of polysilicon was performed with the HBr/$Cl_2/He-O_2$ gas mixture. The residual layers after photoresist strip were investigated using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The etch residue was identified as silicon oxide deposited on the top of the patterned polysilicon. In order to clarify the formation mechanism of the etch residue, the effects of various gas mixtures such as $Cl_2/He-O_2$and HBr/$Cl_2$were investigated. We found that the etch residue is well formed in the presence of oxygen, suggesting that the etch residue is caused by the reaction of oxvgen and non-volatile silicon halide compounds. Wet cleaning and dry etch cleaning processes were applied to remove the polysilicon etch residue, which can affect the electrical characteristics and further device processes. XPS results show that the wet cleaning is suitable for the removal of the etch residue.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.10
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• pp.846-851
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• 2007

In this work, the etching characteristics of $Ge_2Sb_2Te_5(GST)$ thin films were investigated using an inductively coupled plasma (ICP) of $Cl_2/Ar$ gas mixture. To analyze the etching mechanism, an optical emission spectroscopy (OES) and surface analysis using X-ray photoelectron spectroscopy (XPS) were carried out. The etch rate of the GST films decreased with decreasing Ar fraction. At the same time, high selective etch rate over $SiO_2$ films was obtained and the selectivity over photoresist films decreased with increasing the he fraction. From XPS results, we found that Te halides were formed at the etching surface and Te halides limited the etch rate of the GST films.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.211-211
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• 1999

Titanium nitride (TiN) thin films have useful properties including high hardness, good electrical conductivity, high melting point, and chemical inertness. The applications have included wear-resistant hard coatings on machine tools and bearings, decorative coating making use of the golden color, thermal control coatings for widows, and erosion resistant coatings for spacecraft plasma probes. For all these applications as feature sizes shrink and aspect ratios grow, the issue of good step coverage becomes increasingly important. It is therefore essential to manufacture conformal coatings of TiN. The growth of TiN thin films by chemical vapor deposition (CVD) is of great interest for achieving conformal deposition. The most widely used precursor for TiN is TiCl4 and NH3. However, chlorine impurity in the as-grown films and relatively high deposition temperature (>$600^{\circ}C$) are considered major drawbacks from actual device fabrication. To overcome these problems, recently, MOCVD processes including plasma assisted have been suggested. In this study, therefore, we have doposited Ti(C, N) thin films on Si(100) and D2 steel substrates in the temperature range of 150-30$0^{\circ}C$ using tetrakis diethylamido titanium (TDEAT) and titanium isopropoxide (TIP) by pulsed DC plamsa enhanced metal-organic chemical vapor deposition (PEMOCVD) method. Polycrystalline Ti(C, N) thin films were successfully grown on either D2 steel or Si(100) surfaces at temperature as low as 15$0^{\circ}C$. Compositions of the as-grown films were determined with XPS and RBS. From XPS analysis, thin films of Ti(C, N) with low oxygen concentration were obtained. RBS data were also confirmed the changes of stoichiometry and microhardness of our films. Radical formation and ionization behaviors in plasma are analyzed by optical emission spectroscopy (OES) at various pulsed bias and gases conditions. H2 and He+H2 gases are used as carrier gases to compare plasma parameter and the effect of N2 and NH3 gases as reactive gas is also evaluated in reduction of C content of the films. In this study, we fond that He and H2 mixture gas is very effective in enhancing ionization of radicals, especially N resulting is high hardness. The higher hardness of film is obtained to be ca. 1700 HK 0.01 but it depends on gas species and bias voltage. The proper process is evident for H and N2 gas atmosphere and bias voltage of 600V. However, NH3 gas highly reduces formation of CN radical, thereby decreasing C content of Ti(C, N) thin films in a great deal. Compared to PVD TiN films, the Ti(C, N) film grown by PEMOCVD has very good conformability; the step coverage exceeds 85% with an aspect ratio of more than 3.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.1
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• pp.119-125
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• 2006

The present study including two experiments was designed to determine the effect of media containing different rare earth elements (REE) on proliferation and fatty acids accumulation in 3T3-L1 cell cultures. In Experiment 1, 3T3-L1 preadipocytes in 96-well plates ($1.5{\times}10^4cells/ml$) were cultured with Dulbecco's modified Eagle's medium (DMEM) containing 10% fetal bovine serum (FBS) for 24 h. Then the media were changed to the following 10 different media for 48 h: DMEM containing 10% FBS for the control; the above media containing $5{\mu}M$, $10{\mu}M$ or $15{\mu}M$ of $LaCl_3$, $CeCl_3$ or the mixture of these REE chlorides. The proliferation rate of the cells was measured and compared by a non-isotope method-XTT method. In Experiment 2 the cells in 24-well plates ($1.5{\times}10^4cells/ml$) were cultured in DMEM containing 10% FBS for 7 days until confluent and then were changed to above DMEM containing dexamethasone, methyl-isobutylxanthine and insulin (DMI) for two days. Afterwards the media were changed to the 10 different media with REE supplements as in Experiment 1 and cultured for 6 days. The cells were then harvested for fatty acids analysis by gas chromatography. It was found that supplementation of La (5, 10 and $15{\mu}M$), Ce ($5{\mu}M$ and $15{\mu}M$) and the mixture REE (5, 10 and $15{\mu}M$) stimulated (p<0.05) the proliferation of 3T3-L1 preadipocytes (Experiment 1). In the differentiating 3T3-L1 cells supplementation of La ($5{\mu}M$ and $10{\mu}M$), Ce ($5{\mu}M$) and the mixture REE ($5{\mu}M$ and $15{\mu}M$) decreased (p<0.05) the concentration of monounsaturated fatty acids (MUFA) per $10^5cells$, while the supplementation of La ($5{\mu}M$), Ce ($5{\mu}M$) and the mixture REE ($15{\mu}M$) increased (p<0.05) the ratio of saturated fatty acids (SFA) to MUFA. These results indicate that the supplementation of REE to the media may affect proliferation, differentiation and lipogenesis rates of 3T3-L1 cells. However, the effect may depend upon the level or type of REE applied.