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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]
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 ===== Cheesing / bamboo structures ===== ===== 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|}} {{::​azonenberg:​process_examples:​copper_power_rail.jpg?​400|}}
 
process_tech.txt · Last modified: 2015/12/17 17:52 by azonenberg
 
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