For future high-speed and high-density opto-electronic multi-chip module (OE-MCM) packaging, we developed two advanced transferred microsolder bump bonding techniques. One uses 80% Au-Sn, which allows module packaging using processes at various temperatures because it has a higher melting temperature than 100% In and 60% Sn-Pb solders. The other uses multiple transfers of bumps to achieve accurate three-dimensional flip-chip bonding with precise vertical and horizontal alignments within an error of 0 5 m. These techniques will thus be very useful in developing high-speed and high-density OE-MCM's for multi-functional board-level interconnection in future optical communication systems.Index Terms-Flip chip, microelectric packaging, OE-MCM, optical alignment, self alignment, solder bump.

SUMMARYAs a next-generation film carrier packaging technique intended for applications to high-speed large-capacity optical modules, OE-COF (Optoelectronic Chip on Film) packaging is proposed, in which LSIs and optical devices are installed on an optoelectronic compound film (OE film) by means of solder bumps. Its realizability is discussed. A 10-channel VCSEL of the 0.85-µm band with a 250-µm pitch is flip-chip mounted on an OE film by using thirty-six 80% Au-Sn solder bumps with a diameter of 40 µm. In regard to the basic configuration that couples an optical waveguide via a 45° mirror formed on the OE film, a mechanically strong flip-chip mounting of the VCSEL on an OE film and a low-loss optical coupling structure of the VCSEL and the OE film are discussed. As a result, a lowthermal-expansion OE film (11 × 10 -6

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Ge islands are grown by molecular beam epitaxy (MBE) on Si(111) surfaces with an SPE-grown buffer layer, which was expected to prevent intermixing between the epitaxial Ge layer and the Si substrate. The epilayer composition analyzed from the spacing of the Moiré fringe indicates that the Ge islands should be a Si-Ge alloy rather than pure Ge and that the alloying of Ge with Si is greater near the edges of the island. The alloying phenomenon was verified by the compositional depth profile analysis using the scanning Auger electron microscope (SAM) technique. The Si incorporation into the Ge islands observed here cannot be explained by a bulk diffusion mechanism and is a seriously anomalous phenomenon since Si diffusion into Ge would be negligible at the growth temperature and time used ill this experiment.