ICMCTF1999 Session GP: GP Posters

Wednesday, April 14, 1999 5:00 PM in Room Atlas Foyer

Wednesday Afternoon

Time Period WeP Sessions | Topic G Sessions | Time Periods | Topics | ICMCTF1999 Schedule

GP-1 Stabilized Field Emission Behavior of Diamond-like Carbon Coated Si Tips
S.-H. Ahn (Myong-Ji University, Korea); K.-R. Lee (Korea Institute of Science and Technology, Korea); D.-R. Jeon (Myong-Ji University, Korea)

Micromachined Si tips have been considered as a strong candidate for cold cathode materials. However, as prepared tips generally showed unstable emission behaviors presumably due to native oxide, chemical reactions with residual gases, adsorped impurities, arc between the tip and gate electrode and changes in tip geometry. In order to stabilize the emission behavior, diamond-like carbon (DLC) films were deposited on the micromachined Si tips by DC magnetron sputtering method. Before the coating, the Si tips was cleaned by r.f. glow discharge of Ar at the bias voltage of -400 V and the pressure 4mTorr. The films were then deposited at the DC current 0.3 A. Ar pressure during the sputtering was varied from 10 to 30 mTorr. The content of π bond decreased with decreasing the Ar pressure as confirmed by EELS spectra. We focused on the stability of the emission behaviors by repeating the I-V measurement from 100 to 2500 V.

With increasing the number of I-V measurements, the on-set electric field decreased to 24V/µm in both as prepared and DLC coated Si tips. However, the emission current of as prepared Si tips decreased with increasing the number of I-V measurement and eventually disappeared after 9 measurements. This result implied that the number of tips emitting electrons decreased with the I-V measurement. On the other hand, DLC coated tips exhibited increased emission current with increasing the number of I-V measurement. We can thus conclude that the DLC coating can protect the Si tips resulting in stabilized emission behavior. We also reported the effect of the structure of DLC films on the emission behaviors.

GP-2 Fabrication and Characterization of Silicon Field Emission Arrays Coated with Carbon-Based Materials Using ECR-CVD
K.-J. Cheng, F.-G. Tarntair, W.-K. Hong, T.-H. Teng (National Chiao Tung University, Taiwan, R. O. C.); J.-J. Wu, J.-Y. Wen (Academia Sinica, Taiwan, R. O. C.); C.-F. Kuo, L.-C. Chen (National Taiwan University, Taiwan, R. O. C.); K.-H. Chen (Academia Sinca, Taiwan, R. O. C.); H.-C. Cheng (National Chiao Tung University, Taiwan, R. O. C.)
In this article, various carbon-based materials including diamondlike carbon (DLC), PH3 doping DLC, SiC, doping SiC thin films have been successfully coated on the microsize silicon field emission tips by ECR-CVD at low temperature. The characteristics of emission current against applied voltage for as-deposited carbon-based films show superior emission at lower field compared to those blunt undoped diamond-clad, Cr-clad and pure Si microtips. Beside, there is significant improvement on emission properties after in-situ doping the as deposited films. The Raman, XPS and Auger spectrum were investigated those as deposited-based coating to clear the role of carbon content which lacks the diamond NEA property played in the enhanced field emission. To take the advantages of low field emission, low temperature, large area capability growth, ERC-CVD carbon-based clad Si field emission microtips attractive for flat display applications.
GP-3 Correlation Between Field Emission and Nanostructure of Carbon Films
A. Goehl, T. Habermann, G. Mueller (Bergische Universitdt Wuppertal, Germany); B. Schultrich, H.-J. Scheibe (Fraunhofer - Institut f|r Werkstoff und Strahltechnik, Germany); K. Theinissen (Bergische Universitdt Wuppertal, Germany)
Flat carbon films with an internal nanostructure represents a possible solution for field emitter displays. To achieve the necessary stability and homogeneity it is aimed to share the emission between many emission centers. A first overview is obtained by a large area fluorescent and transparent anode. For the quantitative investigation a special equipment was established which allows to explore the spatial distribution and the temporal development of these centers. It is based on a field emission probe with a small current collecting area. By scanning a two-dimensional imaging is possible. The local emission characteristics have been thoroughly investigated for nanostructured carbon films prepared by modified Laser-Arc technique. In dependence on the deposition conditions various types of emission site distributions has been observed. They are correlated with the structure of the nanoscaled composite of carbon in different bonding states.
GP-4 Substoichiometric Titanium Nitride Coatings as Machinable Surfaces in Ultraprecision Cutting
H.-R. Stock, J. Kohlscheen (Stiftung Institut fuer Werkstofftechnik, Germany)
In ultraprecision cutting monocrystalline diamond is nowadays the only acceptable tool material. The major problem with diamond tools is that only few materials are turnable, e. g. aluminium or brass. In contrast, turning ferrous alloys like steel causes severe diamond tool wear. Therefore, steel parts have to be coated with a diamond turnable material, e. g. electroless nickel with phosphorous contents about 20 at. %. Looking for a new diamond turnable material with better mechanical properties than electroless nickel, we investigated substoichiometric titanium nitride coatings deposited by reactive magnetron sputtering. The coating thickness was about 20 µm and the nitrogen content was varied between 0 and 30 at. %. We characterized the chemical composition of the coatings with GDOES and XRD. The mechanical properties were investigated by hardness measurement and scratch test. The machinability of the coatings with monocrystalline diamond tools was tested by ultraprecision cutting. We found that coatings consisting of the α-Ti phase with solved nitrogen yielded surfaces with optical quality. These coatings are homogeneous with moderate hardness. Increasing the nitrogen content leads to the formation of the ε-Ti2N and δ-TiN phase showing columnar growth and increased hardness which causes chipping of the diamond tool and decreased surface quality. The adhesion of the coatings was increased by varying substrate bias and nitrogen content at the coating/substrate interface. With a coating containing 3 at.% nitrogen a fresnel structure could be obtained by ultraprecision cutting.
GP-5 A Complete Dry Lithography Using Plasma Processes
S.O. Kim (Inha University, South Korea); B.K. Park, D.S. Kim, J.K. Park (Howon University, South Korea); K.S. Lee (Dongshin University, South Korea); D.C. Lee (Inha University, South Korea)
The thin films of plasma polymerization were fabricated by the plasma polymerization of inter-electrode capacitively coupled gas flow system. After delineating the pattern as accelerating voltage of 30kilovolt, ranging the dose of 1~500 µC/cm2, the pattern was developed with dry type and formed by plasma etching. By analyzing the molecule structure using FT-IR, it was confirmed that the thin films of PPMST contain the functional radicals of the MST monomer. The thin films of PPMST had a highly cross-linked structure resulting in a higher molecule weight than the conventional resist. The deposition rate of the PPMST thin films was 230~600 Angstrom/minite as a function of 50~200watt power and 200~60Angstrom/minite as a function 0.1~0.7torr pressure. The etching rate of the thin films of PPMST was 875~3520 Angstrom/minite as a function of 50~200watt power and 2870~360Angstrom/minite as a function of 0.2~0.7torr pressure. The sensitivity and contrast of the PPMST resist were 5 µC/cm2 and 4.5, respectively. The resolution of resist was 50nanometer and various patterns having the size of 0.2 micron, 100nanometer, 70nanometer, 50nanometer, 35nanometer, 20nanometer were successfully formed.
GP-6 A Study of Hillock Formation on Chemical Mechanical Polished Aluminum Films Deposited at Various Temperature
P.S. Shih (National Chiao Tung University, Taiwan, R.O.C.); T.C. Chang (National Nano Device Laboratory, Taiwan, R.O.C.); C.Y. Chang (National Chiao Tung University, Taiwan, R.O.C.)

As TFT-LCDs are developed to larger sizes with higher resolution, lower electrical resistivity and higher resistance to hillock formation are required for the interconnections of TFT-LCDs. Aluminum with very low electrical resistivity has been used as the interconnection of TFT-LCDs, but its thermal and mechanical stability are inferior and results in hillock formation.

In this work, we have investigated the Al deposition temperature dependences on hillock formation. Al films deposited from room temperature to 500OC are used in this study. All the as-deposited Al films are subject to chemical mechanical polishing to reduce the surface roughness to about 4 nm and then thermal annealed at 300OC for 30 minutes. After thermal annealing, the surface roughnesses are increased to 16.5 and 5.5 nm for Al films deposited at room temperature and 500OC, respectively. Therefore, the increments of surface roughness reduce from 13.5 nm to 1.5 nm as Al deposition temperature increases from room temperature to 500OC. The increments of surface roughness decrease significantly with increasing deposition temperature. Hillock rarely forms on Al film deposited at 500OC. Therefore, Al film deposited at 500OC with chemical mechanical polishing is very suitable for interconnection of TFT-LCDs.

GP-7 Plasmachemical Si-C-N-Deposition and its In Situ Diagnostics by Optical Emission Spectroscopy
S. Peter, J. Radecker, C. Spaeth, F. Richter (Technische Universitäet Chemnitz, Germany); U. Kreissig (Forschungszentrum Rossendorf, Germany)

Si-C-N films plasmachemically deposited from Si(CH3)4-H2-N2/NH3-Ar mixtures attract attention due to their resistance to wear and corrosion. The deposition of the electrically insulating films was carried out using a low frequency bipolar pulsed discharge. In the investigated range of substrate temperatures (< 450 °C) no thermal decomposition of the precursor occurs, therefore the deposition was completely plasmaactivated.

The aim of our investigations was to find out, which information about the dominating reaction paths can be derived from the analysis of the plasmainduced optical emission of atoms, molecules, ions and radicals. For that purpose the results of OES were correlated with the molar deposition rates of the film forming elements Si, C, N and H.

The relative degree of dissociation of H2 and N2 obtained aktinometrically was only little influenced by the content of this gases in the reactive gas mixture.

Significant changes with the process parameters, however, were observed in the emission intensities of the molecular radicals CH, CN and NH. Owing to their low excitation energies (each nearly 3 eV) we expect that their absolute intensities in a good approximation are proportional to the respective radical concentration in the gas phase provided that the density and energy distribution of the exciting electrons remain nearly constant. As an interesting result the CH-emission at 431 nm shows a dependence on the process parameters very similar than that of the carbon deposition rate.

With increasing gas phase concentration of atomic nitrogen the growing films contain silicon and nitrogen up to the ratio characteristically for Si3N4.

GP-8 Improvement of ICP Plasma with Periodic Control of Axial Magnetic Field
O. Beom-Hoan, S.-G. Park (Inha University, South Korea)
As the critical dimension of the semiconductor fabrication process is getting smaller, it is important to improve a plasma source for higher ion density with higher uniformity, in order to overcome several etching related problems, such as microloading effect, charging effect, and so on. Various types of plasma sources, such as ECR, planar ICP (or TCP), helical ICP, Helicon, Helical Resonator, or SWP, have been researched to raise the plasma density or to remove or decrease microloading effect effectively. Among them, ICP type plasma source, well known to provide uniform high density plasma, accomplished 4% uniformity and high ion density of 1010 cm-3 at the operating pressure condition of 0.1 ~ 100 mTorr by using bucket structure array of permanent magnets. Furthermore, many researchers are interested in the axial magnetic field due to the fact that low magnetic field of about 20 gauss improves the plasma density or selectivity, but uniformity has not been improved. Here, we report the result of improved technique, named ‘Enhanced ICP’, to accomodate very uniform and stable plasma with low electron temperature and high ion density. With oxygen gas, ashing uniformity of below 1% has been accomplished with improved plasma density and low electron temperature of 1 eV. It was accomplished by applying axial magnetic field with periodic on/off control on the normal ICP plasma chamber. As the plasma parameters are observed to be varied periodically according to the variation of the on/off control frequency, this periodic on/off control of magnetic field is considered to be the most important thing to obtain the high uniformity with improved plasma density. This on/of frequency control, which might vary as chamber geometry or operating condition changes, is thought to resonate the period of mode sweeping across different plasma modes to enhance plasma uniformity.
GP-9 Influence of Diffusion Temperature on Structure of Cr-Ti Coating on Carbon Steel
B. Lou (University of Cambridge, United Kingdom)
In this paper, the Cr-Ti coatings on carbon steel are processed with heat-diffusing method in vacuum condition. The structures and components of coating formed at 800°c, 900°c and 1000°c for 1.5h are examined by SEM with electron probe and XRD. The results of component analysis show that chromium and titanium atoms diffused into the surface of steel when diffused at 800°c. As diffusing temperature increase, chromium atoms diffuse rapidly than titanium atoms do. As temperature reaches up to 1000°c, the distribution of two elements in the white layer of coating is uneven. Chromium is rich outside and titanium is rich inside of surface of coating. The results of phase analysis show that there is mainly TiC in the coating formed at 800°c. Some M7C3-type chromium carbide accrues besides TiC when diffused at 900°c. All of TiC, M7C3-type and M23C6-type chromium carbides are formed in the coating formed at 1000°c. The conclusions are that the temperature for Cr diffusing into the coating is high than that for Ti during Cr and Ti codiffusing. The composite compound layer of TiC, (Fe,Cr)3C, Cr7C3 and Cr23C6 can be obtained when diffused at 1000°c, in which chromium carbides are rich in surface of coating.
GP-10 Characterization of Tantalum Oxide Films Grown by Pulsed Laser Deposition
S Boughaba, M Ul-Islam, M.J. Graham, I.G. Sproule (National Research Council, Canada)
Tantalum oxide (TaOx) films were deposited by KrF excimer laser ablation of Ta2O5 targets in oxygen gas ambient. The deposition was performed over silicon substrates. The films were characterized in terms of composition using Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES). The crystallinity and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy, respectively. The index of refraction, extinction coefficient and energy band-gap of the films were measured using a spectrophotometer in the UV-NIR range. The impact of varying the substrate temperature (from room temperature to up to 400°C) and gas pressure (1-50 mTorr) on film properties and growth rate was thoroughly investigated. Differences in the stoichiometry (including a Ta/O ratio around 0.4) were observed when the deposition parameters were varied. For all growth conditions, the tantalum oxide films were found to be homogeneous in composition through their thickness. Sharp interface transition regions between TaOx and silicon were obtained. According to the XRD measurements, the structure of the films was found to be amorphous-like within the temperature range investigated. In terms of optical properties, films with indices of refraction as high as 2.2, extinction coefficients of zero, and energy band-gaps of up to 4.1 eV were grown.
GP-11 Plasma Post Oxidation Process for Automobile Parts
J.-M. Baek (Plasma Technology Center, Institute for Advanced Engineering, South Korea); J.-M. Hong (Plasma Technology Center, Institue for Advanced Engineering, South Korea); Y.-R. Cho, K.-H. Lee (Plasma Technology Center, Institute for Advanced Engineering, South Korea)
A combined plasma nitrocarburizing and plasma post-oxidation process has been treated on a plain carbon steel (AISI 1035) which is widely used for automobile parts to verify the improvement of anti-corrosion and anti-wear properties using a environmental friendly plasma technique instead of conventional wet hard coating method. In the plasma oxidation process, various gas mixtures of water vapor, O2, H2 and N2 were used for the optimum phase control of Fe3O4 and Fe2O3 oxide layer on the nitrocarburized surface. To improve the adhesion properties of Fe3O4 oxide layer an additional O2 plasma activation process was performed after the nitrocarburizing process of the sample. Experimental results will be discussed with the data analyzed using SEM, X-Ray diffraction (XRD), Auger electron spectroscopy (AES). In addition, the advantages of the plasma process over the conventional post-oxidation process for industrial application also will be discussed.
Time Period WeP Sessions | Topic G Sessions | Time Periods | Topics | ICMCTF1999 Schedule