A copper(Cu) thick film conductor containing glass and metal oxide for aluminum niride(AlN) substrate was developed. The conductor showed adhesion strength and reliability which were almost comparable to those of Ag-Pd conductors and also had good solder wettability and erosion properties. The Cu conductors must be fired in a nitrogen atmosphere containing oxygen gas. When they were fired under a low oxygen concentration, the gasses thermally decomposed and their properties changed which meant that the molten gasses could not flow smoothly to the AlN surface, so adhesion strength decreased. On the other hand, under high oxygen concentration, the adhesion strength increased because the thermal decomposition and property changes were suppressed. However, poorer solder wettability was brought about because copper was oxidized. Metal oxide added to the conductor could improve the wettability without decreasing the adhesion strength, even if it was fired at the higher oxygen concentration. Suitable metal oxides were CdO, Co3O5 and Fe2O3.

This paper describes mixed gas systems of SO2 and NO2 which are the essential corrosive gases in an ordinary atmospheric environment of electronic parts. It describes the corrosion product compositions and the behavior of copper in mixed and separate gases. Results of our tests show the following: (1) The weight of corrosion products with the SO2-NO2 mixed gas approximate the sum of those with the individual gases, however, the corrosion products of SO2 are affected by NO2. (2) Tests of the SO2-NO2 mixed gas closely simulates tests of electronic parts in the ordinary atmospheric environment.

This paper presents ceramic multi-layer substrates for mobile communication using alumina-glass composite ceramics and co-fired copper conductors. Electrical characteristics in GHz frequencies of the substrate, copper conductor, transmission line, via hole and coupling between the striplines were evaluated. The results showed that the ceramic multi-layer substrate had good electrical characteristics enough for GHz-band applications. Using the ceramic multi-layer substrates, one can drastically reduce the size of RF circuit boards for mobile communication equipment.

The performance of copper interconnects formed by the low-kinetic-energy ion bombardment process has been investigated. The copper films formed on SiO2 by this technology under a sufficient amount of ion energy deposition exhibit perfect orientation conversion from Cu (111) to Cu (100) upon post-metallization thermal annealing. We have discovered such crystal orientation conversion is always accompanied by a giant-grain growth as large as 100 µm. The copper film resistivity decreases due to the decrease in the grain boundary scattering, when the giant-grain growth occurs in the film. The resistivity of giant-grain copper film at a room temperature is 1.76 µΩcm which is almost equal to the bulk resistivity of copper. Furthermore, a new-accelerated electromigration life-test method has been developed to evaluate copper interconnects having large electromigration resistance within a very short period of test time. The essence of the new method is the acceleration by a large-current-stress of more than 107 A/cm2 and to utilize the self heating of test interconnect for giving temperature stress. In order to avoid uncontrollable thermal runaway and resultant interconnect melting, we adopted a very efficient cooling system that immediately removes Joule heat and keeps the interconnect temperature constant. As a result, copper interconnects formed by the low-kinetic-energy ion bombardment process exhibit three orders of magnitude longer lifetime at 300 K than Al alloy interconnects.