Laser-based method and system for memory link processing with picosecond lasers

Abstract

A laser-based method of removing a target link structure of a circuit fabricated on a substrate includes generating a pulsed laser output at a pre-determined wavelength less than an absorption edge of the substrate. The laser output includes at least one pulse having a pulse duration in the range of about 10 picoseconds to less than 1 nanosecond, the pulse duration being within a thermal laser processing range. The method also includes delivering and focusing the laser output onto the target link structure. The focused laser output has sufficient power density at a location within the target structure to reduce the reflectivity of the target structure and efficiently couple the focused laser output into the target structure to remove the link without damaging the substrate.

1 - 61 . (canceled)  
     
     
         62 . A method for removing target material associated with electrically conductive links, said target material including a passivation material overlying said links, said links being positioned between respective pairs of electrically conductive contacts in a circuit fabricated on a substrate, said links defining a link width, wherein the link may have a passivation layer under the link, said method comprising: 
 providing to a beam positioning system beam positioning data for imparting relative movement of a laser spot position to the substrate in response to processing control signals representing one or more locations of electrically conductive links;    generating for each selected link structure at least two time-displaced laser output pulses, wherein said laser output pulses are characterized by a laser spot size when focused on the link location that is larger than the link width, wherein said pulse energy and power characteristics are such that damage to material underlying the link during link processing is avoided, and insufficient to sever the link; and    coordinating the laser output pulses and the relative movement imparted by the beam positioning system such that the relative movement is substantially continuous while the laser output pulses strike the overlying passivation layer and encompass the link width, the output pulses removing the overlying passivation material associated with the link without causing damage to underlying passivation material or the substrate material underlying the link.    
     
     
         63 . The method of  claim 62 , wherein the step of generating is at least partially accomplished with a Q-switched, solid state laser and wherein the step of coordinating is at least partially accomplished with an optical switch positioned external to the laser.  
     
     
         64 . The method of  claim 62 , further comprising amplifying the laser output pulses.  
     
     
         65 . The method of  claim 62 , wherein said link comprises metal, polysilicide, or polysilicon.  
     
     
         66 . The method of  claim 62 , wherein the underlying layer comprises an underlying layer of SiO 2 .  
     
     
         67 . The method of  claim 62 , wherein the links are processed at a rate of at least 1 kHz to somewhat less than about 20 kHz.  
     
     
         68 . The method of  claim 62 , wherein each of the laser pulses has a pulse width in the range of several picoseconds to about ten nanoseconds.  
     
     
         69 . The method of  claim 62 , wherein each of the laser pulses has a pulse width of less than 5 nanoseconds.  
     
     
         70 . The method of  claim 62 , wherein each of the pulses produces a focused laser spot having a peak power of at least 10 9  W/cm 2 , a diameter of about 1 to 4 micrometers, and duration of several picoseconds to about 10 nanoseconds, whereby said pulses have an energy ranging from about 0.1 nanojoules to about 5 microjoules.  
     
     
         71 . The method of  claim 62 , wherein the laser outputs pulses have an energy of 0.1 microjoules to 3 microjoules, wherein the method further comprises attenuating the laser output pulses by up to 90% such that the energy of the pulses impinging the target material ranges from 10 nanojoules to 3 microjoules.  
     
     
         72 . The method of  claim 62 , wherein each of the pulses has an energy of 0.1 microjoules up to 3 microjoules of energy.  
     
     
         73 . The method of  claim 70 , wherein each of the pulses has an energy of 0.1 microjoules up to 3 microjoules of energy.  
     
     
         74 . The method of  claim 62 , wherein each of the output pulses have approximately the same energy.  
     
     
         75 . The method of  claim 62 , wherein at least two of said output pulses have different pulse widths.  
     
     
         76 . The method of  claim 75 , wherein at least two of the output pulses have different energies.  
     
     
         77 . The method of  claim 62 , wherein the pulses are generated at a wavelength of less than about 2000 nm.  
     
     
         78 . The method of  claim 62 , wherein the beam positioning system causes relative movement at substantially constant speed during processing.