Roy C. Iggulden

Temperature dependence of the Al-fill processes for submicron-via structures

Today, numerous different PVD techniques are used for the filling of sub micron contacts and vias in ULSI devices. One of the most promising approaches is the Al-reflow process. In this process, voids in vias which form during the PVD deposition of Al are eliminated by the thermal diffusion of Al. The ability of the aluminum to diffuse into the voids becomes increasingly dependent on the temperature of the reflow steps as device dimensions decrease. Therefore, it becomes necessary to deposit the Al at high temperatures, with the risk to influence the electrical properties of other underlying metal films and roughen the metal surface due to larger grain sizes. In this paper, the effect of the Al-deposition temperature on contact/sheet resistance and short yield of the deposited film and the influence of high temperature Al depositions on the electrical properties of underneath lying metal stacks are investigated.

Aluminum dual damascene metallization for 0.175 mm DRAM generations and beyond (invited).

This paper presents an overview of issues associated with Al dual damascene process technology. Different integration schemes are discussed and characteristics of metal fill, planarization and reliability are highlighted. Finally, a comparison is made between Al dual damascene, Al RIE, and Cu dual damascene.

Electromigration in aluminum damascene lines

Four different metallization processes for AlCu dual damascene are investigated with respect to their electromigration lifetime and compared to a metallization using subtractive metal etching. It is shown that the electromigration reliability lifetime depends strongly on the metal stack and the metallization process used. Three fill processes that employ PVD Ti and PVD Ti/TiN liners result in poor electromigration, while a process using CVD TiN leads to superior electromigration performance. In this particular case the current density had to be increased to values as high as 2.5 MA/cm2 in order to induce a statistically relevant number of fails in certain structures. Two of the most important parameters that determine the electromigration lifetime in damascene lines are (1) the quality of the Al sidewalls as determined for instance by the presence of a TiAl3 reaction layer and (2) the amount of TiAl3 formation that reduces the bulk AlCu thickness. The texture of the AlCu matrix is of less importance. In f...