ICMCTF1998 Session C2/G4: Ellipsometry, Plasma Diagnostics and Optical Methods for Process Monitoring and Control

Tuesday, April 28, 1998 8:30 AM in Sunset Room

Tuesday Morning

Start	Invited?	Item
8:30 AM		C2/G4-1 Process Monitoring and Control of Low Temperature Reactively Sputtered AlN S.R. Kirkpatrick, D.M. Mihut, M.L. Kuruppu, J.R. Swanson III, S.L. Rohde, D. Thomson, J.A. Woollam (University of Nebraska) Using a new process control/monitoring system linking in situ ellipsometry, quadropole mass spectrometry, and target voltage analysis, the growth processes for AlN film growth can be studied simultaneously (1)at the target, (2)in the gas phase and (3)at the substrate. Iterative optimization is replaced almost entirely by in situ, real-time process control/monitoring; reducing development time by more than an order of magnitude. To demonstrate this, AlN was reactively sputtered using an unbalanced magnetron on to 2024-Al, Si, and 52100 steel substrates. Differing ion intensities were achieved by varying the current in a Helmholz coil placed behind the substrate, and the effects of bias and pulsed bias were studied by X-ray analysis, AES, profilometry, microhardness, and adhesion tests. X-ray analysis confirmed the formation of hexagonal Aluminum Nitride, with a preferred orientation of (0002). A detailed analysis of aluminum nitride with nitrogen flow was compared with the ellipsometric and target voltage vs. nitrogen flow data to determine the optimal N2 flow rate. The sputtering rate of AlN was minimally 28% of the metal sputtering rate.
8:50 AM		C2/G4-2 Deposition of Tungsten Thin Films by Dual Frequency Inductively Coupled Plasma Assisted CVD P. Colpo, F. Rossi (European Commission, Joint Research Centre, Italy) An innovative Inductively Coupled Plasma source has been designed and tested for the deposition of W/WC multilayers by PACVD from WF₆. The reactor is equiped with a double inductor powered by 2 Low and High frequencies for induction heating of the substrate and plasma production respectively. Characterisation of the plasma source by magnetic and Langmuir probes as well as Energy Resolved Ion Mass spectrometry indicate that plasma densities as high as 5 10₁₂ cm^-3 can be obtained over a large pressure range. Modelling of the ICP source equivalent circuit is related to impedance measurements. Good agreement between modelling and experiment is obtained. Ion energy distribution functions as a function of pressure are presented and related to the first results of W deposition. Relationship between microstructure and plasma parameters are presented
9:10 AM		C2/G4-3 Mass and IR Diagnostics in PECVD of Silicon Oxide Films Using Organosilicon Reactant Y. Inoue, Y. Takahara, H. Sugimura, O. Takai (Nagoya University, Japan) Recently coating of silicon oxide films onto polymer has been strongly needed, so that plasma-enhanced chemical vapor deposition (PECVD) using organosilicon compounds, which is possible to lower process temperature, has been extensively studied. At present, however, the deposition mechanism of silicon-oxide films at low temperature is not clear. In this study we investigated the behavior of organosilicon molecules in rf-PECVD of silicon oxide films using two kinds of diagnosing techniques, mass analysis of gas species in the plasma and in situ IR absorption measurement on the film surface. We used an inductively-coupled rf PECVD system. After the evacuation below 1 Pa, tetramethoxysilane (TMOS) gas was introduced into the chamber. The pressure of TMOS and the rf power were kept at 10 Pa and 50 W. We used a quadrapole mass spectrometer (QMS) to analyze the gas in the plasma sampled through a pinhole on the substrate holder. In situ observation of film surface was carried out by a Fourier transform infrared spectrometer (FT-IR). We observed a reduced fragmentation pattern of TMOS gas in the plasma when the ionization part of QMS was activated. The intensity of the peak at m/e=152, mass number of TMOS molecule, was 1/100 compared with that of same peak without discharge. This fact means that the 99% of TMOS molecules are modified in the plasma. The ions generated in the plasma was measured directly by inactivating the ionization part of QMS. In the mass region of m/e>152, some discrete peaks were observed clearly. Polymerization of reactant molecules and their fragments occur in the vapor phase.
9:30 AM		C2/G4-4 Plasma Diagnostics During Low Dielectric Constant Film Deposition in a Helicon Plasma Reactor S.M. Yun, H.Y. Chang (KAIST, Korea); M.G. Kang, C.K. Choi (Cheju National University, Korea) Various plasma parameters such as electron density, electron temperature, electron energy distribution function (EEDF), radical density and substrate temperature are measured during low dielectric constant film deposition in a helicon plasma reactor. The electron density, electron temperature, and EEDF are measured by a Langmuir probe. The electron density and temperature are obtained directly from the I-V curve of the Langmuir probe. EEDF is measured by the 2nd harmonic method using a lock-in amp. Low dielectric constant films are deposited using SiF₄/O₂ and FSi(OC₂H₅)₃/O₂ mixtures on 5 inch p (100) Si wafers. The film characteristics such as chemical bonding and dielectric constant are measured by fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), and metal insulator structure (MIS). The source gases are dissociated greatly into radicals such as F, Si, and O when the high density plasma above 10¹² cm^-3 is obtained. Thus, the deposition process is different between the helicon plasma CVD where the dissociated radicals participate in the film formation, and the thermal CVD where the source gases chemically react on the substrate. In the case of SiF₄/O₂, method the film composition is not different between the helicon plasma CVD and thermal CVD. However, in the case of FSi(OC₂H₅)₃/O₂ method the film composition is different between the two methods. The reasons of these results are explained by the plasma diagnostics and film characterization.
10:10 AM		C2/G4-6 Break
10:30 AM	Invited	C2/G4-7 New Developments in Precision Optical Coatings R.B. Sargent, M.J. Cumbo (OCLI) Improvements in the performance of precision optical coatings have led to their increasing acceptance in a variety of light-filtering applications. For example, the development of environmentally-stable filters in the past decade resulted in widespread use of such coatings in medical and aerospace instrumentation. Recently environmentally-stable filters possessing unprecedented spectral performance have been demonstrated. This extension of the technology has led to the use of precision optical coatings for extremely demanding applications such as dense wavelength division multiplexing (DWDM) telecommunication systems. DWDM systems employ multiple optical carriers at different wavelengths which are combined for transmission over the same optical fiber. One popular method for combining and separating wavelenghts in DWDM system is based on the transmission and reflection characteristics of interference filters. The spectral requirements for DWDM devices are very demanding and result in challenging filter specifications with regard to spectral shape and wavelength positioning. Additionally, DWDM devices must operate over wide temperature ranges and be compatible with a variety of devices such as optical amplifiers. This paper reviews new requirements for precision optical coatings, with an emphasis on those used in DWDM applications, and details the excellent performance which is achievable.
11:30 AM		C2/G4-10 Ellipsometry and Transport Studies of Thin-film Metal Nitrides A. Nebojsa, J. Hora, J. Humlicek (Masaryk University Brno, Czech Republic); M. Strasky, J. Spousta, T. Sikola (Technical University Brno, Czech Republic) We present the results of a systematic spectroellipsometric and conductivity study of metallic nitride (mostly TiN) thin films prepared by the ion-beam-assisted deposition technique. We correlate the dc resistivity with the contactless, noninvasive ellipsometric method of extracting the free- and bound-carrier response in the infrared, visible, and ultraviolet spectral ranges. We find the optimum conditions for the ellipsometric measurements, and demonstrate the potential of the technique on several series of the filmed samples grown at varying substrate temperatures and ion-beam energies. The high polarizibility of free carriers at optical frequencies presents nontrivial problems of the optimization. We discuss the relative merit of the ellipsometric data taken at proper angles of incidence in different spectral ranges, aiming at the maximized precision and accuracy of the sought film parameters. We also test the algorithms of fast parameter retrieval for the use in in-situ measurements. The implications of the trial to replace the spectroellipsometric data with single- or double-wavelength laser measurements in the in-situ environment, aiming at the increased speed and simplified data treatment, are discussed. Finally, we address the issue of optimum data sampling during the growth of both homogeneous and graded TiN films on silicon.