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Microporous structures of nickel-aluminide thick films lining the inner wall of microchannels have been investigated. The microchannels were produced in metal bodies by a powder metallurgical process utilizing microscopic reactive infiltration. In the experiment, a nickel-powder compact containing shaped aluminum wires was sintered at a temperature between the melting points of nickel and aluminum. Infiltration and diffusion of aluminum into the surrounding nickel powder, accompanied by the reaction between the metals, occurred during the sintering and brought about the formation of microchannels lined with a NiAl intermetallic layer. In this process, nickel powder composed the device body, and the aluminum wires gave the shape of the microchannels. The intermetallic layer had a microporous structure when the diameter of the aluminum wire was 500 mm and the porosity of the compact specimen was 23.6-31.5% within the porosity range examined. When the porosity was 36.0%, such a structure, the porous thick film, was not observed. On the other hand, the porous NiAl thick film was produced in all specimens with an aluminum wire of 200 mm in diameter. The voidage of the porous thick film was maximized when the porosity of the compact specimen was 29.8%, and it reached to 53.8% in the case the diameter of the aluminum wire was 500 mm, and 60.2% in the case that was 200 mm.

Realization of an ultra-clean process environment, in which contamination f rom molecules adsorbed by the waf er surf ace i s fully controlled, is extremely important for the production of future submicron ULSI devices. The key to the achievement of such an ultra-clean process environment is the proper treatment of the surface of the stainless steel. That is extensively used in the ultra-hiSh pur ity gas supply Iine and the process chamber. Of central importance is controlling the process ambienee for minimized both outgas and corrosion-related contamination.

When a hypereutectic aluminum-silicon alloy containing 16 wt pct silicon was rapidly solidified into powder using the spinning water atomization process, the individual powder grains were predominantly aluminum that was supersaturated with silicon and also contained well-dispersed 0.02-m silicon particles. Although the silicon particles grew when the powder was extruded into a bar at temperatures from 673 to 803 K at an extrusion ratio of 4.3 and an extrusion speed of 0.9 mm/s, the average diameter was maintained on a submicron level. When the extrusion temperature was decreased from 803 to 673 K, the average diameter of the silicon particles in the extruded bar decreased from 0.8 to 0.5 m, while the Vickers hardness (HV) and the ultimate tensile strength of the extruded bar increased from 120 to 160 (HV) and from 330 to 500 MPa, respectively. Both the hardness and the tensile strength of the extruded bars were several times higher than those of conventionally cast bars of the same alloy with cooling rates from 10 Ϫ1 to 10 2 K/s. On the other hand, the elongation decreased from 5.5 to 3.1 pct when the extrusion temperature was decreased from 803 to 673 K.

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