Young Chai Kim

Low temperature remote plasma cleaning of the fluorocarbon and polymerized residues formed during contact hole dry etching

We investigated the remote oxygen and hydrogen plasma cleaning to remove reactive ion etching (RIE) induced fluorocarbon and polymerized residues formed during the dry etching of the contact hole. After the RIE process, RIE induced fluorinated surface and/or fluorocarbon formation with a very homogeneous spatial distribution at several tens of A depth from the surface was observed. The photoresist films before and after the RIE process showed a similar ashing behavior. Ashing rate generally increased with increasing the process temperature and plasma power. X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis showed that the carbon and fluorine associated contamination can be effectively removed by oxygen plasma but it left a small amount of carbon residue and sacrificial silicon oxide. Hydrogen plasma cleaning was necessarily required to remove the residual carbon contaminants formed on the silicon surface after oxygen plasma ashing. Two step cleaning, oxygen plasma ashing with an intentionally left very thin photoresist layer and subsequent hydrogen plasma cleaning, is a very effective cleaning process to remove residual carbon and polymer without forming a SiO2 layer. This article presents the systematic evaluation of the remote oxygen and hydrogen plasma cleaning of RIE induced polymer residues.We investigated the remote oxygen and hydrogen plasma cleaning to remove reactive ion etching (RIE) induced fluorocarbon and polymerized residues formed during the dry etching of the contact hole. After the RIE process, RIE induced fluorinated surface and/or fluorocarbon formation with a very homogeneous spatial distribution at several tens of A depth from the surface was observed. The photoresist films before and after the RIE process showed a similar ashing behavior. Ashing rate generally increased with increasing the process temperature and plasma power. X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis showed that the carbon and fluorine associated contamination can be effectively removed by oxygen plasma but it left a small amount of carbon residue and sacrificial silicon oxide. Hydrogen plasma cleaning was necessarily required to remove the residual carbon contaminants formed on the silicon surface after oxygen plasma ashing. Two step cleaning, oxygen plasma ashing with an in...

Effects of amine and amine oxide compounds on the zeta-potential of emulsion droplets stabilized by phosphatidylcholine

Abstract A positively charged submicron emulsion based on phospholipid was suggested and their surface electrical properties were investigated at various pHs. Additives used to change the zeta potential of emulsion were decyldimethylamine oxide (DeDAO), dodecyldimethylamine oxide (DDAO) stearylamine (SA) and dodecylamine (DA). Also the emulsion droplet size and size distribution were measured to study the effects of additives on the emulsion properties. By adding additives, the zeta potential of emulsion droplet has been significantly changed but there were little effects on emulsion size and size distribution. In a wide range of pH (≈8.0), all additives yielded the positive zeta potential values. But at pH 10, amine compounds generated the negative-charged emulsion droplets while amine oxide compounds generated the neutral emulsion droplet. From this study, it was found that amine oxide compounds as well as amine compounds can be used to modify the zeta potential of emulsion droplets from negatively charged to positively charged below pH 8.0 for the effective drug delivery vehicles.

Synthesis of microporous gallosilicates with the CGS topology

Zeolite TNU-1 (Taejon National University Number 1), a gallosilicate possesing the CGS topology with a three dimensional system of medium and small pores, crystallises in the presence of Ga in conditions in which the presence of Al yields merlinoite-type zeolites.

Synthesis and characterization of Ga-substituted MER-type zeolites

Abstract Ga-substituted merlinoite (MER)-type zeolites are hydrothermally synthesized using aluminosilicate MER crystals as seeds under wholly inorganic conditions. The presence of Ga in tetrahedral positions is evidenced by powder X-ray diffraction, 29 Si and 71 Ga MAS NMR, and IR spectroscopies. The bulk Si/(Ga+Al) ratio in the framework determined by elemental analysis is in the range 1.9–3.0, depending on the initial Si/Ga ratio of the synthesis mixture. An attempt to fully substitute framework Al by Ga was not successful: a gallosilicate with GIS topology, denoted TNU-2, is produced when aluminosilicate MER seed crystals are not added to the synthesis mixture. This clearly shows that the structure-directing ability of Ga is different from that of Al in the synthesis conditions used here.

The conversion of natural gas to higher hydrocarbons using a microwave plasma and catalysts

Methane, the major constituent of natural gas, had been converted to higher hydrocarbons by a microwave plasma. The yield of C2+ products increased from 29.2% to 42.2% with increasing the plasma power and decreasing the flow rate of methane. When the catalysts were used in the plasma reactor, the selectivities of ethylene and acetylene increased while the yield of C2+ remained constant. Among the various catalysts used, the Fe catalyst showed the highest ethylene selectivity of 30%. When we introduced the actual natural gas, more C2+ products were obtained (46%). This is due to the ethane and propane in the natural gas. When an electric field inductance for evolving the high plasma was applied, a high yield in C2+ products of 63.7% was obtained for the Pd-Ni bimetal catalyst.

Selective reduction of nitric oxide by methane on cobalt-ion-exchanged synthetic clinoptilolite zeolite in oxygen-rich atmosphere

Selective reduction of NO by CH4 in the presence of excess O2 has been studied on cobalt-ion-exchanged synthetic clinoptilolite (Co-CLI) zeolite. The catalytic results are compared with those obtained from Co-ZSM-5 and Co-FER, the two most widely studied catalysts for this reaction. At T ≥ 500 ºC, Co-CLI is much more active for NO reduction than Co-ZSM-5, but it is less active than Co-FER. However, it is found that the selectivity for CH4 toward reacting with NO at high temperatures (T ≥ 450 ºC) is higher on Co-CLI than on Co-ZSM-5 or Co-FER. On the basic of the overall catalytic results, the importance of zeolite pore size as a structural parameter influencing the activity of intrazeolitic Co2+ ions for NO reduction by CH4 is discussed.

Anti-complement effects of anion-substituted poly(vinyl alcohol) membranes

In a continuation of our previous studies on blood compatibility profiles of anion-substituted poly(vinyl alcohol) (PVA) membranes, in which hydroxyl groups have been replaced with carboxymethyl (C-PVA) and sulfonyl groups (S-PVA), we have studied the activation of complement components and the changes in white cell and platelet countin vitro and compared them with those of unmodified PVA, Cuprophane, and low-density polyethylene. Complement activation of fluid phase components, C3a, Bb, iC3b, and SC5b-9, and of bound phases, C3c, C3d, and SC5b-9, were assessed by enzyme-linked immunosorbent assay (ELISA) and immunoblot, respectively. The changes in the number of white cells and platelets following complement activation were counted using a Coulter counter. C-PVA and S-PVA activated C3 to a lesser extent than did PVA, which we attribute to the diminished level of surface nucleophiles of the samples. In addition, C- and S-PVA exhibit increased inhibition of Bb production, resulting in a decrease in the extent of C5 activation. Consequently, because of the reduced activation of C3 and C5, C- and S-PVA samples cause marked decreases in the SC5b-9 levels in plasma. We also found that the negatively charged sulfonate and carboxylate groups of the samples cause a greater extent of adsorbtion of the positively charged anaphylatoxins, C3a and C5a, because of strong electrostatic attraction, which in turn provides an inhibition of chemotaxis and activation of leukocytes. The ability to inhibit complement production, together with the binding ability of anaphylatoxins of the C- and S-PVA samples, leads to a prominent decrease in lysis of leukocytes as well as activation of platelets.

Characteristics of Polymer Residues Formed at the Via Hole and Photoresist Ashing Properties of Remote Oxygen/Nitrogen Plasma.

The low-temperature remote oxygen/nitrogen plasma ashing process that removes both the photoresist and polymer residues containing carbon and fluorine after reactive ion etching (RIE) process was investigated. The fluorocarbon residue was distributed with a depth of several tens of angstroms from the surface with a relatively homogeneous spatial distribution after the RIE process. X-ray photoelectron spectroscopy (XPS) analysis also showed the formation of fluorocarbon films during RIE with mainly C–C, C–CFx (x=1,2,3), CF, and CF2 bonds. The ashing rate increased with increasing amount of nitrogen addition to oxygen gas and showed saturation at approximately 10% of nitrogen addition. Mass spectrometry measurement revealed that the amount of atomic oxygen increased with the addition of nitrogen to oxygen gas. This study revealed that atomic oxygen is the primary reactive species responsible for removal of photoresist in the remote oxygen/nitrogen ashing process.

Remote RF plasma cleaning for the removal of organic impurity

Summary form only given, as follows. The trends in modern silicon-based microelectronics are pointing in the direction of in-situ processing at low temperature to achieve reliable profiles and to make use of compatible processes. Low energy plasma process, called the plasma cleaning, can be used to clean silicon surfaces from the carbon contaminants and native oxide without any pretreatment of the wafers. In the integrated circuit (IC) fabrication, the photoresist (PR) ashing and PR stripping processes are generally followed the silicon etching process to remove the PR and polymerized residues. However, it was founded no tendency on surface but a benefit of the plasma treatment by means of cleaning the surface. In this work, we investigate the surface reaction of plasma generated in inductively coupled remote plasma with connection of mass spectroscopy.

Atom recombination on SiO/sub 2/ and Si(100) surfaces

Summary form only given, as follows. The probability of recombination was measured for recombination of hydrogen and oxygen atoms on SiO/sub 2/ and Si(100) surfaces at 298 K, 500 K, 700 K, 900 K and 1100 K in the range of 0.1 torr with hydrogen and oxygen gas. The probability of recombination was a first order reaction with respect to the atom concentration from 298 K to 1100 K. The Arrhenius plots were very complex. All observations were explained by assuming a surface with a small fraction of active sites that irreversibly bind chemisorbed atoms. We have proposed a process of atom recombination at the surface active sites.