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--- process_tech [2013/10/20 10:59]
127.0.0.1 external edit
+++ process_tech [2015/12/17 17:49]
azonenberg [Cheesing / bamboo structures]
@@ Line 32: / Line 32: @@
 ===== Cheesing / bamboo structures =====
-Copper processes will typically include "cheesing" or a "bamboo structure" - small rectangular cutouts in large power buses - because copper is more susceptible to electromigration than aluminum is (see [[http://en.wikipedia.org/wiki/Electromigration#Bamboo_structure_and_metal_slotting|Wikipedia article on electromigration]]). Since mass transport in electromigration typically occurs parallel to grain boundaries, the rate of mass transport can be dramatically reduced by making the wire width smaller than the grain size so that grain boundaries are largely perpendicular to the direction of current flow. As a result, the presence of these structures can be used as a very strong hint that the process is copper based.
+Modern processes will typically include "cheesing" or a "bamboo structure" - small rectangular cutouts in large power buses (see [[http://en.wikipedia.org/wiki/Electromigration#Bamboo_structure_and_metal_slotting|Wikipedia article on electromigration]]). Since mass transport in electromigration typically occurs parallel to grain boundaries, the rate of mass transport can be dramatically reduced by making the wire width smaller than the grain size so that grain boundaries are largely perpendicular to the direction of current flow. As a result, the presence of these structures can be used as a hint that the trace in question carries high current.
-FIXME: Is this backwards? Some aluminum stuff uses bamboo too.
+Xilinx CoolRunner-II CPLD (180nm aluminum, 4 metal layers)
-Xilinx CoolRunner-II CPLD (180nm copper, 4 metal layers)
 {{::azonenberg:process_examples:copper_power_rail.jpg?400|}}