Some historical background concerning studies on residual water molecules in vacuum chambers and devices are introduced. The effect of adsorbed water molecules on pumping process in initial and steady state is outlined. Pumping delay time due to sojourn time of the molecule is also discussed.

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  Water vapor has previous been considered to be detrimental to sputtering processes. However, the intentional addition of water vapor during sputter deposition has recently attracted attention as a method to control the structure, as well as physical and chemical properties of metal and oxide thin films. The crystal orientation and surface flatness of metal films, as well as etching rates of conducting oxide films are improved by the addition of water vapor to the sputtering gas. Hydroxide and hydrate thin films, which are electrochemically active, have also been formed using water vapor as a reactive gas. H₂O molecules are dissociated into H atoms and OH radicals in the plasma, and these active species are incorporated into the deposited thin films. H₂O molecules are also incorporated effectively into the hydrate films at low substrate temperatures, and this has been shown to improve proton conductivity.

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  Concept of ultra clean (UC) dry-process proposed by present authors in 1990s has been widely used in various thin film fabrication fields from the view point of research as well as volume production stages of electronic devices. Original basic concept for UC-process sometimes are lead to another wrong concept direction, usually caused by a compromise for temporal trial, space limitation, facility, and so on. In this paper, UC technological items originally proposed is briefly reviewed. Influence of vacuum atmosphere by chamber baking, moisture content in process gas lines, outgasing of co-sputtering cathode equipped with magnetic fluid, and particle sources in fore-pump. are re-checked again in research process for perpendicular magnetic recording media.

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  In order to precisely control the microelectronics manufacturing processes, it is essential to reduce or remove the moisture in the gases, which is desorbed from the surface of gas supply system. The equilibrium concentration of adsorbed moisture and its heat of adsorption on variously finished stainless steel surfaces have been introduced in this paper, and the removal characteristics of adsorbed moisture have been investigated using Atmospheric Pressure Ionization Mass Spectrometry (APIMS). The multi-layers of the adsorbed moisture on electro-polished surface of 316L stainless steel could be removed with only continuous purging at room temperature. Also, the effect of batch purging for adsorbed moisture on the surface has been described. However, since it has been speculated that the adsorbed moisture with about 10¹⁵ molecules/cm² remains on the surface only with room temperature purging, a careful operation of gas supply system is needed to use high purity gas without desorbed moisture from the surface, after seal-off the gas in gas supply system.

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  Two types of simple non-evaporable getter (NEG) assemblies have been constructed using commercial St707 strips. The first one can be activated by direct current heating at 15 A. The second can be activated by indirect heating using a tantalum heater at 12 A. The base pressure of the chambers pumped solely by the first and the second NEG assemblies reached 2.4×10⁻⁸ and <1×10⁻⁸ Pa, respectively.

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