Method of reworking structures incorporating low-k dielectric materials

Abstract

Methods of etching a semiconductor structure using ion milling with a variable-position endpoint detector to unlayer multiple interconnect layers, including low-k dielectric films. The ion milling process is controlled for each material type to maintain a planar surface with minimal damage to the exposed materials. In so doing, an ion beam mills a first layer and detects an endpoint thereof using an optical detector positioned within the ion beam adjacent the first layer to expose a second layer of low-k dielectric film. Once the low-k dielectric film is exposed, a portion of the low-k dielectric film may be removed to provide spaces therein, which are backfilled with a material and polished to remove the backfill material and a layer of the multiple interconnect metal layers. Still further, the exposed low-k dielectric film may then be removed, and the exposed metal vias polished.

1 - 6 . (canceled)  
   
   
       15 . A system for delayering a semiconductor structure including a first layer of material overlaying a second layer of low-k dielectric film, comprising: 
 a processing chamber;    an ion beam milling source in said processing chamber for generating a beam of ions to mill said semiconductor structure;    a platen in said processing chamber for supporting said semiconductor structure in said beam of ions;    a crystal endpoint detector in said processing chamber;    a photospectrometer outside of said processing chamber;    means for connecting said crystal endpoint detector to said photospectrometer; and    means for positioning said crystal endpoint detector proximate said platen to monitor milling of said semiconductor structure.    
   
   
       16 . A system in accordance with  claim 15  wherein said crystal endpoint detector comprises a sapphire crystal.  
   
   
       17 . A system in accordance with  claim 15  and further including means for introducing a gas into said processing chamber.  
   
   
       18 . A system in accordance with  claim 15  wherein said ion beam milling source comprises an Argon ion beam-milling source.  
   
   
       19 . A system in accordance with  claim 18  and further comprising a charge-neutralizing filament positioned to enclose the Argon ion beam when said Argon ion beam milling source is in operation.  
   
   
       20 . A system in accordance with  claim 15  wherein and further including means for cooling said semiconductor structure.  
   
   
       21 - 27 . (canceled)  
   
   
       28 . A system in accordance with  claim 15  wherein said platen comprises a liquid-cooled platen.  
   
   
       29 . A system in accordance with  claim 28  wherein said liquid-cooled platen is capable of cooling in a range of −15 to +35 degrees centigrade.  
   
   
       30 . A system in accordance with  claim 15  wherein said ion beam milling source comprises an inert noble gas.  
   
   
       31 . A system in accordance with  claim 15  wherein said inert noble gas is selected from the group consisting of helium, neon, xenon, and radon.  
   
   
       32 . A system in accordance with  claim 15  further including a circumferential charge neutralizing filament surrounding said ion beam milling source.  
   
   
       33 . A system in accordance with  claim 15  wherein said crystal endpoint detector is positioned within said beam of ions for milling said semiconductor structure.  
   
   
       34 . A system for delayering a semiconductor structure including a first layer of material overlaying a second layer of low-k dielectric film, comprising: 
 a processing chamber;    an ion beam milling source in said processing chamber for generating a beam of ions to mill said semiconductor structure;    a platen in said processing chamber for supporting said semiconductor structure in said beam of ions; and    a fiber optic photospectrometer endpoint detector system of said processing chamber having a crystal endpoint detector residing within said beam of ions for milling said semiconductor structure.    
   
   
       35 . A system for delayering a semiconductor structure including a first layer of material overlaying a second layer of low-k dielectric film, comprising: 
 a processing chamber;    an ion beam milling source in said processing chamber for generating a beam of ions to mill said semiconductor structure;    a platen in said processing chamber for supporting said semiconductor structure in said beam of ions;    a sapphire crystal endpoint detector in said processing chamber;    a photospectrometer outside of said processing chamber;    means for connecting said sapphire crystal endpoint detector to said photospectrometer; and    means for positioning said sapphire crystal endpoint detector proximate said platen to monitor milling of said semiconductor structure,    wherein said sapphire crystal endpoint detector resides within said beam of ions for milling said semiconductor structure.    
   
   
       36 . A system in accordance with  claim 35  wherein said ion beam milling source comprises an inert noble gas selected from the group consisting of argon, helium, neon, xenon, and radon.  
   
   
       37 . A system in accordance with  claim 35  further including a circumferential charge neutralizing filament surrounding said ion beam milling source.  
   
   
       38 . A system in accordance with  claim 35  wherein said means for connecting said sapphire crystal endpoint detector to said photospectrometer comprises a fiber optic cable.  
   
   
       39 . A system in accordance with  claim 38  wherein said fiber optic cable is connected at a first end to said sapphire crystal endpoint detector within said processing chamber and at a second end to said photospectrometer outside of said processing chamber.  
   
   
       40 . A system in accordance with  claim 38  further including a ferro-fluidic vacuum feed-through accommodating a stainless steel tube housing said fiber optic cable.  
   
   
       41 . A system in accordance with  claim 40  wherein said stainless steel tube housing said fiber optic cable are motor operated, said method further including an electromechanical positioning device for positioning said sapphire crystal endpoint detector to regions of interest on semiconductor substrate.