What method and process are you using to deposit the Al ?
50-80nm is not small, it's miniscule. Under optimal
conditions, grain diameters in 1um Al films can be
over 5 um !
Possible reasons for small Al grains:
1. contamination (substrate, chamber, materials...)
2. substrate bias
hope this helps
klaus
--
(TEEL) Tokyo Electron Europe Limited
PVD Process Support (ex MRC)
Klaus Beschorner Tel +49-7033-45683
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71120 Grafenau, Germany Mobile +49-174 315 7754