AMD will soon begin producing 45-nanometer chips.  45nm is a small chip, and the smaller the chip, the relatively larger a speck of dust becomes.  As chips become smaller, dust can make more of them contaminated and unusable.  At the same time, you need greater efficiency in chip production.  Read more about it here.

http://www.linuxworld.com/news/2006/121306-amd-
seeks-efficiency-in-making.html?page=1