FABRICATION OF SUBMICRON SINGLE-CRYSTALLINE AND BAMBOO AL LINES BY RECRYSTALLIZATION

We have developed a process for the fabrication of single-crystalline and bamboo Al lines by recrystallization. A groove pattern of submicro meter dimensions is fabricated into an oxide layer by electron-beam-li thography and reactive-ion-etching. Blanket Al sputter deposition and heating, led to melting and subsequent filling of the grooves. The mic rostructure of the Al was examined with Backscatter Kikuchi Diffractio n (BKD) and TEM. The presence of an in-plane temperature gradient duri ng heating and cooling had a profound influence on the microstructure of the resolidified Al lines. The lines fabricated without a temperatu re gradient were 'bamboo' and had the common (111) fiber texture. Thos e fabricated with a temperature gradient were 'distorted' single-cryst als. Both types of lines have a low resistivity, indicating a high pur ity. The lines are electromigration lifetime-tested at 200 degrees C a nd with a current density of 2 or 8 MA/cm(2). After 1800 hrs, one of t he 15 single-crystalline lines had failed. Two out of the 7 bamboo lin es had failed. In these two, facetted voids were observed.