Papers

AVS1997 Session MS-MoM: Contamination-Free Manufacturing I co-sponsored by the Ultra-Clean Society

Monday, October 20, 1997 8:20 AM in Room J1/4

Monday Morning

Start	Invited?	Item
8:20 AM		MS-MoM-1 Ultra Clean Society's Activities for Manufacturing Science and Technology T. Ohmi (Tohoku University, Japan) Ultra Clean Society(UCS) has been started in 1988 to establish scientific semiconductor manufacturing based on ultraclean processing concept described by 1)ultraclean wafer surface, 2)ultraclean process environment and 3)perfect parameter controlled processes. UCS are now focussing on the development of coming scientific semiconductor manufacturing line approaching to future flow shop manufacturing system instead of current job shop system, where very wide variety of technologies are concurrently developed such as stepper/scanner having compatibility, well regulated high density plasma for RIE, sputtering and P-CVD, metal contamination free ion implanter for low temperature(500 degrees C.) anneal, chemical vapor generation free wet cleaning and photoresist stripping, in-line type CMP, gas delivery system, gas pumping system, wasted gas reuse and recycling system, wasted chemicals reuse and recycling system, wafer transport and stock system in clean air ambience, and etc.
9:00 AM		MS-MoM-3 Real-Time Monitoring of Scattered Laser Light by a Single Particle of the Order of Several Tens Nanometers in the Etching Chamber in Correspondence with its Equipment Status F. Uesugi, N. Ito (NEC Corp., Japan); H. Doi (ANELVA Corp., Japan) In wafer processing plants for DRAM mass production, particle contamination in the reactive ion etching (RIE) chamber is one of the most prevalent causes of low availability of processing equipments and low fabrication yield. Up to now, particle clouds in the RIE chamber has been investigated by laser light scattering.¹ For realization of particle-free RIE process and/or equipment, however, it is neccessary to clarify the mechanism of a single particle outbreak and to observe the track to interpolate the start and end point in the RIE chamber. Therefore, an experimental in-situ particle monitoring system was produced so as to fit these purposes. This system employs 532nm SHG light from a Nd-YAG pulse-laser as a light source and a gated CCD camera which measures scattered light as 2-dimensional images acquired synchronously with current RF power and other status signals of the RIE equipment. A single flaking particle on the order of several tens of nanometers from an electrode in the RIE chamber was observed as an isotropic scattered light pattern. The track of a single particle was also acquired as successive isotropic patterns in one image. Moreover, the fact that the particle outbreak occurred both during and after etching process was clarified. ^ext G. S. Selwyn and A. D. Bailey, J. Vac. Sci. Technol., A14, 649 (1996).
9:20 AM		MS-MoM-4 Pit-Free Electropolishing of Aluminum and its Application for Process Chamber K. Tajiri (Mitsubishi Heavy Industries, Ltd., Japan); Y. Saito (KEK-High Energy Accelerator Research Organization, Japan); Y. Yamanaka (Asahikinzoku Kogyo Co., Ltd., Japan); Z. Kabeya (Mitsubishi Heavy Industries, Ltd., Japan) Electropolishing technology of aluminum (Al) vacuum chamber is considered to be essential for the future ultra-LSI production device to minimize its weight. Therefore, we developed electropolishing technology to obtain pit-free highly smooth (Ra=0.03(Jm) Al surface which covered with oxide film of 200nm thick. This technology is marked by preventing hydrogen gas bubbles to get smooth surface. Since they stick on Al surface and form etch pits at each sticking sites. At first we applied this technology for Al gaskets for vacuum type wave guide in accelerator system. Vacuum sealing performance of the gaskets was extreamly improved by electropolishing treatment and reliability of vacuum wave guide became much better. This electropolishing technology has possibility to apply for various shapes of aluminum components of semiconductor production devices. So, we are now examining the properties such as electric resistance of the surface, outgasing rate and so on.
9:40 AM		MS-MoM-5 TEOS/O₃ CVD to Employ a Clean and High Density Ozone Generator M. Kuzumoto, Y. Okihara, K. Sugawara (Mitsubishi Electric Corp., Japan) We have developed a unique ozone generator with an entirely new structure using an extremely narrow discharge gap of 0.1mm for semiconductor fabrication processes. This unique ozone generator can generate extremely high density (over 250g/Nm³) and clean (metal particle-free) ozone. In addition, the ozone generator is much smaller in size. Those advantages are obtained by using the extremely narrow discharge gap as already reported. We successfully applied it to the TEOS/O₃ (Tetra Ethyl Ortho Silicate/Ozone) CVD method for the production of silicone oxide insulating film with ozone density of up to 120g/Nm³ which has been used mainly for the TEOS/O₃ process because of the limitation of conventional ozone generators. By using higher density ozone produced by this unique ozone generator, it is expected to give significant improvement in film flatness and reduction in film shrinkage. In the symposium, we will present the performance of this unique ozone generator and the results of experiments to apply extremely high density ozone to the TEOS/O₃ CVD method.
10:00 AM		MS-MoM-6 Integrated Compact Gas Delivery System N. Ikeda, Y. Shirai (Tohoku University, Japan); M. Yamaji, Y. Minami (Fujikin Inc., Japan); T. Ohmi (Tohoku University, JAPAN) In 300 mm wafer generation, more compact integrated gas delivery system will be required in order to reduce the foot space. Of course, maintainability and cost are also very important factors in mass production systems. There, $B!(J) concept of ultra clean technology, $B"(J) easy maintenance and high reliability against sealing performance in field work, $B*#(J) fewer number of required parts , must be satisfied for the integration of gas delivery systems. Integration system is constructed keeping all these essential points in mind. By adopting a new metal gasket type sealing method in connection with each component, we introduced a construction method for integrated gas delivery systems which is compatible with other gas delivery systems because of its two valve types. Dry down property of the system is also introduced when the gas delivery system is installed with Chromium Oxide passivation treated components. It gives possibility of safely and precisely controllable gas delivery system (just like city water service style flow system where gas displacement of inert gas is not necessary after use) of ideal ultra clean gas distribution system for scientific semiconductor manufacturing.
10:20 AM		MS-MoM-7 Etching/Deposition Uniformity in Flat Parallel Electrode Plasma Systems Using Shower Head M. Nakagawa (Tokyo Electron Limited, Japan) It has been believed that increase in silicon and LCD substrate dimension might be blocked due to theoretical limit due to maintenance of etching/deposition uniformity in the flat parallel electrode plasma systems. In the chamber, gas is supplied uniformly through a shower head, and is pumped out through only the periphery of the substrate. It has been believed the by-product gas concentration at the peripheral area is larger than the up-stream, so it is difficult to maintain gas concentration uniformity over the substrate when the substrate dimension becoms much larger. This work shows it is not so. it was concluded by algebraic analysis and by numerical calculation, that the above mentioned combination of "the shower head and the peripheral drain" essentially makes the gas concentration virtually equal, in almost the entire area of the sustrate when the reaction rate has a linear relation to the molar fraction. This conclusion is indeppendent of the substrate dimension.
10:40 AM		MS-MoM-8 Self-Consistent Particle Simulation of Radio-Frequency CF₄ Discharge with Implementation of All Ion-Neutral Reactive Collisions K. Denpoh (Tokyo Electron Limited, Japan); K. Nanbu (Tohoku University, Japan) Electronegative gases are commonly used in plasma-assisted etching processes for manufacturing microelectronic devices. In order to design and control such discharges it is important to understand plasma chemistries and the behavior of negative ions. However, most research on discharge modeling and simulation have focused on electrons and positive ions, and ion-neutral or ion-ion collisions have been simplified for lack of detailed collision data. In the present study, the ion-CF₄ collision model including endothermic reactions has been developed for CF₄ discharges. The total cross-section of ion-CF₄ collision is obtained from the Langevin-Hassé model. Then the branching ratio of each reaction path is determined by employing the Rice-Rampsperger-Kassel(RRK) theory. The collision models and collision data are implemented into a self-consistent simulation of RF glow discharge in CF₄. The charged species taken into account are electron, five positive ions, and two negative ions. Their motions and collisions are treated by the Particle in Cell/Monte Carlo (PIC/MC) method. The cross-section data set compiled by Itoh et al. is employed for electron impact collisions with CF₄ molecules. Reactive collisions between CF₄ molecules and positive ions (especially CF₃⁺) are clearly observed in the ion sheath. It is also found that the major loss process of negative ions is due to the recombination with positive ions rather than electron detachment.
11:00 AM		MS-MoM-9 Suppression of Impurity-Backdiffusion in Vacuum Pumping Systems for Ultraclean Low-Pressure Semiconductor Processing K. Ino, K. Sekine, T. Shibata, T. Ohmi (Tohoku University, Japan) Most of the wafer processes in semiconductor manufacturing are carried out in a reduced-gas-pressure ambient in the range of mTorr to several tens mTorr's. Such a processing environment is created by feeding process gases into a process chamber while evacuating the chamber by a vacuum pumping system. A vacuum pumping system for such use bears very stringent performance requirements. First of all, it must exhibit UHV capability to produce an ultraclean environment in the processing chamber when gas flow is suspended. At the same time, however, it must drag a large gas volume typically in the range of several hundreds to thousands sccm. The most important feature is the high impurity compression ratio under a large amount of gas flow in order to guarantee ultraclean environment during processing. The purpose of this work is to experimentally demonstrate the impurity back diffusion phenomena occurring in a reduced-gas-pressure system and to develop an advanced pumping system optimized for such use. Impurity backdiffusion through a backing pump and a UHV turbomolecular pump (TMP) to a low-pressure processing chamber was experimentally studied and the impurity compression ratio under gas flow was measured. The impurity backstreaming is strongly dependent upon not only the pumping system but also the gas flow rate. It is clarified for the first time that the impurity level in the chamber can be made even lower than that for the best performance of the main pump under UHV operation when the gas flow rate is optimized for the system. The degradation mechanism of the pumping speed of TMP*s under large gas flow has been also analyzed. Degradation occurs when the inlet pressure of the TMP moves into a transition regime. The guidelines for designing a vacuum pumping system for use in reduced-gas-pressure processing will be presented in detail at the meeting.
11:20 AM		MS-MoM-10 High Density Microwave Plasma Source without Magnetic Field for Large Area PECVD and Plasma Oxidation M. Hirayama, T. Ohmi (Tohoku University, Japan) High density (>1x10¹²cm^-3) uniform (±2%) plasma has been produced over a 300mm electrode without any magnetic field by 8.3GHz uniform microwave radiated from a radial line slot antenna. Damage-free film formation will be realized in PECVD and plasma oxidation, since the ion energy arriving at the wafer surface is extremely low in this plasma source (<7e V for the gas pressure above 120mTorr). The process gas can be fed into the processing space through a showerhead without plasma ignitions in the showerhead at the relatively high microwave frequency of 8.3GHz. The gap of the processing space can be narrowed below 30mm while keeping excellent uniformity and stability of the plasma. Therefore efficient and uniform removal of the byproduct gas, which is essential for large-area fast film formation, can be realized. The plasma source developed in this work will be the best candidate for future PECVD and plasma oxidation. We have been tried oxidizing silicon wafer surfaces utilizing the high density Ar/He/O₂ plasma excited by 8.3GHz microwave. The gate oxide film whose performance is almost equivalent to that of a thermal oxide film has been successfully formed at extremely low temperature of 430°C.
11:40 AM		MS-MoM-11 Highly-Reliable Ultra Thin Gate Oxide Formation by Employing a New Water Vapor Generator T. Iwamoto, A. Morimoto (Tohoku University, Japan); K. Kawada (Fujikin Inc., Japan); T. Ohmi (Tohoku University, Japan) We have developed a new water vapor generator by using Pt catalytic effect. Generally, gate oxides formed by wet oxidation (pyrogenic system) are more reliable than gate oxides formed by dry O₂ oxidation. However, payrogenic systems are problems because the injecting part of their quartz chamber melts away. Furthermore, because of safety reasons only H₂O/O₂ oxidation ambient is used in semiconductor production. The water vapor generator which employs Pt catalytic effect can generate ultra pure water at a low temperature (400°C) and introduce H₂O, H₂O/O₂, H₂O/H₂ gases into the gate oxidation furnace. And a highly-reliable gate oxide can be formed by using the water vapor generator. In this presentation, we will demonstrate the feature and performance of the new water vapor generator and the electrical characteristics (TDDB, J-V) of ultra thin gate oxide formed by the water vapor generator. To put it concretely, 50% Q_BD value under constant stress (1A/cm²) on 6.2nm oxide film formed in 2% H₂O/Ar ambient is 69.3C/cm² in the substrate injection.