Atomic and Electronic Design ob Ceramic/Metal Interfaces

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Adhesive energies and atomic/electronic structure of metal to ceramic interfaces have been investigated by using the first principle molecular dynamics method based on the density-function theory. This investigation have been conducted through the tight collaboration between Prof.Ohuchi and Dr.Kohyama. The most important finding of the research was that in case of SiC (110) and SiC (100) and Al bonding, there is a strong attractive C-Al interactions with both ionic and covalent characters in the bonded interface, which are considered to play a favorable role in adhesion between SiC and Al. These theoretical results are confirmed by the bonding experiments conducted by Prof.Suga. By means of the surface activated bonding method, he has succeeded in bonding ceramic-metal system at room temperature. TEM study on the microstructure of the bonded interfaces, which has been continued since the last year, showed that a direct bonding of such ceramic-metal interface is formed actually only by contact between such clean surfaces. However, a closer observation of the bonded interface between Al2O3 and Al using the high resolution TEM showed that there is a strong distorted region of several nm thickness which possesses another structure which is different from both Al2O3 and Al. Formtion of such thin intermediate layr was interpreted as a result of strong deformation of the interfaces in contac that would lead to compensate the lattice mismatch. There results have been analyzed and complied for further development of interface engineering, and published in several international conferences. Also possibilities of these findings in application of the packaging technology in the near future has been discussed with fairly good expectations.