Characterization of Thin Film Growth Processes and Evolving Film Properties

Thursday, April 13, 2000 8:30 AM in Room San Diego

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8:30 AM F5-1 Ultrathin SiO@sub 2@ Film Growth on Si by Highly Concentrated Ozone
S. Ichimura, A. Kurokawa, K. Nakamura, H. Itoh, H. Nonaka (Electrotechnical laboratory, Japan); K. Koike (Iwatani International Corporation, Japan)
The growth mechanism of SiO@sub2@ thin film on Si(100) and Si(111) by ozone was investigated using various surface/interface analytical techniques such as XPS, STM, AFM, SHG (Second Harmonic Generator), and MEIS (Medium E nergy Ion Scattering spectroscopy). Two different ozone generators were fabricated and used for the investigation. The first ozone generator, which was used for the study of the initial oxidation, supplies low pressure (<10@super -2@ Pa) and high purity (>80%) ozone gas by vaporization of pure liquid ozone at low temperature (< 100 K). The second ozone generator, used mainly for the oxide film growth, supplies high pressure (1 atm) ozone gas with concentration <30% by desorbing ozone adsorbed on silica-gel. @paragraph@ Through the comparison of ozone oxidation to the oxidation with molecular oxygen, followings were made clear. i) Atomic oxygen dissociated from ozone molecules at Si surface directly attacks backbond of Si, hence it can oxidize hydrogen -terminated Si which oxygen molecules can not. ii) Formation of suboxide at the SiO@sub2@/Si interface is suppressed, leading to stable Si-O-Si network formation even at low pressure and low temperature condition. iii) The oxide thin film growth proceeds in layer-by-layer manner, and the interface keeps the original step/terrace structures at the interface after the growth of about 1 nm thick oxide film. In addition to these features, the existence of no (or very thin) structural transition layers was suggested for the ozone oxide film by the MEIS experiments and the etching experiment with dilute HF solution, while those experiments for thermally grown oxide showed the existence of the transition layers with thickness about 1 nm. Based on these results, the superior features and growth mechanism of SiO@sub2@ by ozone will be discussed.
9:10 AM F5-3 Influence of Sputtering Power and the Substrate-target Distance on the Properties of ZrO2 Films Prepared by rf Reactive Sputtering
P. Gao (University of Minho, Portugal); L-J. Meng (Instituto Superior de Engenharia do Porto, Portugal); M.P. Dos Santos, V. Teixeira, M. Andritschky (University of Minho, Portugal)
The ZrO2 films have been deposited onto glass substrates by rf reactive magnetron. The effects of the rf power and substrate-target distance on films properties have been studied. The X-ray diffraction results show that the monoclinic phase is a dominant phase although a small part of the tetragonal phase of ZrO2 can be observed in the films. All films show a random orientation. The films prepared at small target-substrate distance and the high rf power show a strong orientation along the [200] direction. As the distance is increased and the rf power is decreased, the intensity of this peak decreases drastically and the [111] peak intensity increases gradually. The average crystallite size increases with the increasing of sputtering power and decreases with the increasing substrate-target distance. The surface becomes rough as the sputtering power decreases and the substrate-target distance increases. The transmittance decreases as the sputtering power decreases and the substrates-target distance increases. The refractive index of the film decreases and the extinction coefficient increases as sputtering power decreases and the substrate-target distance increases. In this work, all these results will be discussed.
9:30 AM F5-4 Investigation of the System for Plasma Enhanced Chemical Vapor Deposition of Hard Coatings
P. Spatenka (University of South Bohemia, Czech Republic); Ch. Taeschner, K. Bartsch (Institut für Festkörper- und Werkstofforschung Dresden, Germany); A. Leonhardt (Institute for Solid State and Materials Research Dresden, Germany); M. Sery (University of South Bohemia, Czech Republic); J. Pavel (J. Pavel Company, Czech Republic)
The system for plasma enhanced chemical vapour deposition of TiN and (TiAl)N hard coatings was studied by means of the Langmuir probe technique to obtain better control of the film growth. Two planar reactors with showerhead grounded electrode and powered substrate holder were used for this study. The substrate were heated up to 500@super o@ C. A negative pulses were applied to the substrate holder. A mixture of argon, hydrogen and nitrogen and tinaniumtetrachlorid and/or aluminumtrichlorid were used as the working gas. The electron density, electron temperature and plasma potential were investigated in dependence on the pressure, power, reactor temperature and working gas composition. It has been found that both the plasma potential and the electron density decreased with pressure and this tendency was independent of the composition of the working gas. The highest value of the electron density was 2.0x10@super 16@m@super -3@ at 1.5mbar and this value decreased to 6.9x10@super 15@m@super -3@ at 2.5 mbar. Simultaneously a drop of the plasma potential from 0 V at 1.5 mbar down to -23V at 2.5mbar was observed. Addition of the reactive gas caused a further decrease of the plasma potential under -50V. The rise in the reactor temperature resulted in an enhancement of the plasma potential. The plasma potential changed from -29V at 120@super o@C up to -0.7V at 410@super o@C with simultaneous increase in the electron density from 5.7x10@super 15@m@super -3@ up to 3.5x10@super 16@m@super -3@. The measurements during the deposition process indicate very good stability of the plasma used for the deposition of (TiAl)N whereas some instability occurs during deposition of TiN. A significant difference in the ion current of about a factor 8 between particular positions indicated different gas composition at various positions in the reactor. This corresponded with different Ti/Al ration found in films deposited at various positions on the substrate holder.@paragraph@One of us, Petr Spatenka, acknowledges financial support by the Grant Agency of Czech Republic, Grant No. 202/98/0116.
9:50 AM F5-5 Deposition of TiN Thin Film on Si(100) by HCD Ion Plating
J.H. Huang, G.P. Yu, W.C. Chou (National Tsing Hua University, Republic of China)
Titanium nitride (TiN) film was deposited on Si(100) substrate using a hollow cathode discharge ion plating (HCD-IP) technique. Based on the previous experimental results, one of the optimum deposition conditions was chosen. The TiN film thickness and the angle between specimen surface and the evaporating source (coating angle) were selected as the controlling parameters. The purpose of this study is to investigate the effect of these two processing parameters on the properties of TiN film. After deposition, the thin film structure was characterized by X-ray diffraction (XRD), cross-sectional transmission electron microscopy (XTEM), and high-resolution scanning electron microscopy (SEM). N/Ti ratios of the thin film were determined using Rutherford backscattering spectrometer (RBS). The resistivity of TiN film was measured by four-point-probe. The hardness of the thin film was obtained from ultra-microhardness tests. Atomic force microscope (AFM) was used to measure the roughness of the thin film. The results showed that (111) is the dominant preferred orientation in the TiN film for most of the deposition conditions and for all coating angles, especially as film thickness greater than 1 mm. Hardness values of TiN film were 23 - 24 GPa and did not vary with the coating angle. The hardness can be correlated to the (111) preferred orientation of the TiN film. The hardness increased with the (111) texture coefficient and level off as the texture coefficient approached to 1. The packing factor has a linear relationship with the film thickness. Resistivity decreased with increasing thickness and increasing packing factor for all coating angles. At a similar thickness or packing factor, specimens coated at angles different from 0@super o@ had a much higher resistivity than those coated at 0@supero@.
10:30 AM F5-7 Effects of Nitrogen on the Properties of Amorphous Silicon Carbon Niitrogen Alloys
Y. Gao (Nan Yang Technological University, Singapore); D.H. Zhang (Nanyang Technological University, Singapore); J. Wei (Gintic Institute of Manufacturing Technology, Singapore); P. Hing, X. Shi (Nan Yang Technological University, Singapore)
Silicon-carbon-nitrogen alloys deposited by DC magnetron sputtering system with RF bias, using graphite and silicon targets, at different nitrogen partial pressure were systematically investigated. The analysis techniques for the alloy films include X-ray photoelectron spectroscopy (XPS), UV/VIS absorption /transmission, Fourier transform infrared spectroscopy (FT-IR) and Raman scattering and X-ray diffraction (XRD). The bonds between Si-N, Si-Si, C-N, C-O, C-C, N-H and Si-C have been observed in the alloy and the bonds between C-N have also been found to be single, double and triple bonds. However, the Si-C bond is not as many as others and the bond does not change significantly with nitrogen composition. As N@sub2@ partial pressure is increased, the N/(C+Si) and C/(N+Si) ratios both increase. However, the single C-N bond is found to decrease while the double and triple C-N bonds are found to increase. These observations indicate that the bonding between carbon and nitrogen dominates in SiCN alloy although their bondings with Si are also observable. In addition to the above, the deposition rate, energy band-gap, electrical conductivity, film hardness and crystallization have also been examined, and they all very with nitrogen partial pressure. Our results could provide useful information for the application of the alloy in microelectronics.
10:50 AM F5-8 Morphological and sStructural Characteristics of Homoepitaxial 4H-SiC Thin Films by Chemical Vapor Deposition Using Bis-trimethylsilylmethane Precusor
J.-K. Jeong, H.J. Na, M.Y. Um, H.J. Kim (Seoul National University, Korea)
Single crystal 4H-SiC films were grown on 8.0@super o@ off-oriented (0001) 4H-SiC at a low temperature (1370@super o@C) by metal-organic chemical vapor deposition (MOCVD). The correlation between the structural properties of the films and the growth parameters, in particular, the substrate temperature, and the flow rate of source material BTMSM was investigated to elucidate the possible benefits of single precursor on low-temperature thin film growth. Reciprocal space mapping result of (0004) Bragg spot showed that full width at half maximum (FWHM) of the rocking curve of the epi-layer grown at 1370@super o@C was 9.3 arcsec, which is very excellent value, considering the lowest value reported up to now is 13 arcsec @footnote 1@. Also, the homoepitaxy window of high quality monocrystalline 4H-SiC was found in terms of the growth temperature and the supersaturation of source material. @FootnoteText@ @footnote 1@ A. J. Steckl, J. Devrajan, S. Tlali, H. E. Jackson, C. Tran, S. N. Gorin and L. M. Ivanova, Appl. Phys. Lett. 69 (1996) 3824.
11:10 AM F5-9 The Properties of Mg Activation in GaN:Mg Films by Using RTA and Furnace Treatment
C-F. Lin, H-C. Cheng (National Chiao Tung University, Taiwan, R. O. C); Gou-Chung Chi (National Central University, Taiwan, R. O. C)
The GaN:Mg films were grown by LP-MOCVD on polished optical-grade C-face (0001) sapphire substrates. Sapphire was placed on a graphite susceptor in a horizontal type reactor with a RF heater. Trimthylgallium (TMGa), ammonia (NH@sub 3@) and bis-cyclopentadienyl-magnesium (Cp@sub 2@Mg) were used as the Ga, N and Mg sources, respectively. After growing the buffer layer at 525@super o@C on sapphire substrates, the temperature was raised to 1025 @super o@C to grow a thin undoped GaN epitaxial layers (as the second buffer layers) and 2µm Mg doped p-type GaN layers for this experiment. The Mg-acceptors of GaN:Mg films were activated as the p-type GaN with rapid thermal annealing (RTA) and Furnace treatments. The GaN:Mg films were activated successfully using the RTA system in N@sub 2@ ambient below 1000@super o@C for 1 min. From the PL spectra, the FWHM and emission intensity of DAP peaks treated with RTA were sharper and stronger than with Furnace. Compared the electric properties of GaN:Mg films with RTA and Furnace activation process, the activation efficiency was similar and hole mobility was higher of GaN:Mg films with 800@super o@C RTA treatment. The surface states of GaN:Mg films were damaged by high temperature RTA treatment, the higher bulk resistivity were induced by the increasing the nitrogen vacancy during the high temperature and long time treatment. The activated hole concentration was 2.4„e10@super 17@ cm@super -3@ and the bulk resistivity was 1.6 @ohm@cm with 800@super o@C RTA treatment. When the hole concentration increased, the mobility in both series of GaN:Mg films were decreased because of ionic acceptors scattering effect. The RTA system provided the fast, low temperature and better electric properties for the p-type GaN:Mg activation process.
11:30 AM F5-10 Characterization of Hot Wall Epitaxy Grown AgInTe@sub2@ films
R.K. Bedi (Guru Nanak Dev Unversity, India); A. Singh, A. Mahajan, R. Kumar, I.S. Athwal (Guru Nanak Dev University, India)
Silver Indium Telluride (AgInTe@sub2@) films have been grown by Hot Wall Epitaxy (HWE) technique onto the KCl substrate kept at different temperatures in vacuum of 1x10@super -5@ torr. The experimental conditions are optimised to obtain better crystallinity of the films. Besides Scanning and Transmission electron microscopy, the electrical conductivity, Hall mobility and carrier concentration as a function of temperature are investigated. @paragraph@ Observations reveal that the electrical conductivity of films increases with the increase in temperature and show higher mobility when compared to those prepared on glass substrate. The films appear to be p-type; thus, indicating holes as dominant charge carrier. Results on electron microscopy indicate that HWE grown AgInTe@sub2@ films show comparatively better crystallinity and crystallite size increases with the increase in substrate temperature.
11:50 AM F5-11 About the Mechanism of the Film Composition Formation During Magnetron Sputtering of Alloys
L.R. Shaginyan (Institute for Problems of Material Science, Ukrainian National Academy of Science, Ukraine); M. Mishina (Institute of Physics Academy of Sciences of the Czech Republic); J. Musil (University of West Bohemia, Czech Republic); L. Jastrabik (Institute of Physics Academy of Sciences of the Czech Republic)
The films were deposited by unbalanced magnetron sputtering of W-30at%Ti alloy target. The influence of the working gas (Ar) pressure, substrate bias, substrate location and discharge current on the film and gas phase composition were studied. At low working gas pressures (0,05-0,1 Pa) the gas phase composition (Ti@super +@/W@super +@>1) and the composition of the film (Ti/W=0,18) revealed large difference. Taking into account low scattering probability of sputtered species in the gas phase (the "substrate-target" distance was 5 cm) it was concluded that the main factor influencing the film composition is the re-sputtering of the light Ti atoms from the unbiased substrate by energetic neutrals reflected from the target. The increase of the Ti/W up to 0,32 for the film deposited at 3 times lower discharge current confirmed this suggestion. At high gas pressures (5-25 Pa) the film composition Ti/W=0,46 was close to the target (Ti/W=0,43). The reasons of this effect are the diffusive transport of sputtered particles and the absence of the substrate bombardment by neutrals at these conditions. The presence of a small amounts of the oxygen (0,6%) in the films deposited at a certain conditions and simultaneous increasing of Ti/W from 0,19 up to 0,21 allowed us to suggest the presence of the chemical sputtering together with physical sputtering. The last process may increase Ti content in the film due to additional transport of Ti by TiO molecules, which ions (0,2% relatively Ti@super +@) were revealed by mass-spectroscopy in the gas phase during the sputtering. The films deposited simultaneously onto two substrates one of which was normal and the other parallel relatively the flux of sputtered particles had equal composition. These results allowed to suggest the absence of the difference in the angular distribution for different sputtered particles.