Processing a memory link with a set of at least two laser pulses

Abstract

A set ( 50 ) of laser pulses ( 52 ) is employed to sever a conductive link ( 22 ) in a memory or other IC chip. The duration of the set ( 50 ) is preferably shorter than 1,000 ns; and the pulse width of each laser pulse ( 52 ) within the set ( 50 ) is preferably within a range of about 0.1 ps to 30 ns. The set ( 50 ) can be treated as a single “pulse” by conventional laser positioning systems ( 62 ) to perform on-the-fly link removal without stopping whenever the laser system ( 60 ) fires a set ( 50 ) of laser pulses ( 52 ) at each link ( 22 ). Conventional IR wavelengths or their harmonics can be employed.

1 . A method for laser severing a conductive link in an integrated circuit (IC), the method comprising: 
 providing position data representative of locations of one or more conductive links;    generating at least two laser pulses, the laser pulses including a first laser pulse and a second laser pulse, wherein each of the first and second laser pulses produce a laser spot at the integrated circuit, and the first and second laser pulses have different energy densities; and    directing, based on the position data, the laser pulses to a selected conductive link to sever the selected conductive link, wherein the laser spots are in movement relative to the selected conductive link while the laser pulses are directed to the selected conductive link, and the first and second laser pulses are sequentially directed to the selected conductive link.    
     
     
         2 . The method of  claim 1 , wherein the step of directing the laser pulses includes providing a focusing lens that is in relative movement with respect to the selected conductive link while the laser pulses are directed to the selected conductive link.  
     
     
         3 . The method of  claim 1 , comprising directing the laser pulses through a gating device.  
     
     
         4 . The method of  claim 1 , wherein the selected conductive link comprises a link of a memory device or a logic device.  
     
     
         5 . The method of  claim 1 , wherein a passivation layer overlies the selected conductive link.  
     
     
         6 . The method of  claim 1 , wherein a burst comprising the laser pulses has a width less than 500 ns.  
     
     
         7 . The method of  claim 6 , wherein the burst comprises more than two laser pulses.  
     
     
         8 . The method of  claim 1 , wherein the second laser pulse starts after the end of the first laser pulse.  
     
     
         9 . The method of  claim 1 , wherein each of the laser pulses has energy characteristics, and the number of laser pulses and the energy characteristics of each of the laser pulses are determined as a function of the thickness of the selected conductive link to be severed.  
     
     
         10 . The method of  claim 1 , wherein the selected conductive link has a width less than or equal to about 1 μm.  
     
     
         11 . The method of  claim 1 , wherein the step of generating the laser pulses is performed using a mode locked laser.  
     
     
         12 . The method of  claim 1 , wherein the step of directing the laser pulses to the selected conductive link includes producing first and second laser spots of the first and second laser pulses, respectively, that overlap at the selected conductive link.  
     
     
         13 . The method of  claim 1 , wherein each of the first and second laser pulses has a single peak pulse shape.  
     
     
         14 . The method of  claim 1 , wherein the laser pulses have an ultraviolet (UV) or near UV wavelength.  
     
     
         15 . The method of  claim 1 , wherein a spot size of at least one of the laser pulses is greater than a width of the selected conductive link.  
     
     
         16 . The method of  claim 1 , wherein the step of generating the laser pulses is performed using a Q-switched laser.  
     
     
         17 . The method of  claim 1 , wherein the step of generating the laser pulses includes using an A-O, Q-switched, solid-state laser having an A-O Q-switch that is step controlled such that an RF signal to the Q-switch is reduced from a high power level to an intermediate level to generate the first laser pulse, and the RF signal to the Q-switch is reduced from the intermediate RF level to a smaller RF level to generate the second laser pulse.  
     
     
         18 . The method of  claim 1 , wherein at least one of the laser pulses has a pulse width of less than 25 picoseconds.  
     
     
         19 . The method of  claim 1 , wherein the step of generating the laser pulses comprises first generating two or more laser pulses and second generating two or more laser pulses to sever respective conductive links, wherein the laser pulses in the first and second generating steps have different energy density profiles.  
     
     
         20 . The method of  claim 1 , wherein the first and second laser pulses have different energy characteristics.  
     
     
         21 . The method of  claim 1 , wherein the step of generating the laser pulses comprises using harmonic conversion.  
     
     
         22 . A method for laser severing a conductive link in an integrated circuit (IC), the method comprising: providing position data representative of locations of one or more conductive links; 
 generating at least two laser pulses, the laser pulses including a first laser pulse and a second laser pulse, wherein the first and second laser pulses have different energy densities; and    directing, based on the position data, the laser pulses to a selected conductive link to sever the selected conductive link, wherein the first and second laser pulses are sequentially directed to the selected conductive link.    
     
     
         23 . A method for laser severing a conductive link in an integrated circuit (IC), the method comprising: 
 providing position data representative of locations of one or more conductive links;    generating a beam comprising at least two laser pulses, the laser pulses including a first laser pulse and a second laser pulse, wherein the first and second laser pulses have different energy densities; and    directing, based on the position data, the laser pulses to a selected conductive link to sever the selected conductive link, wherein the selected conductive link and the beam are in relative movement while the laser pulses are directed to the selected conductive link, and the first and second laser pulses are sequentially directed to the selected conductive link.    
     
     
         24 . A method for laser severing a conductive link in an integrated circuit (IC), the method comprising: 
 providing position data representative of locations of one or more conductive links;    generating at least two laser pulses, the laser pulses including a first laser pulse and a second laser pulse, wherein the first and second laser pulses have different energy densities; and    sequentially directing on-the-fly, based on the position data, the laser pulses to a selected conductive link to sever the selected conductive link.    
     
     
         25 . A method for laser severing a conductive link in an integrated circuit (IC), the method comprising: 
 providing position data representative of locations of one or more conductive links;    generating a beam comprising at least two laser pulses, the laser pulses including a first laser pulse and a second laser pulse, wherein the first and second laser pulses have different energy densities; and    sequentially directing on-the-fly, based on the position data, the laser pulses to a selected conductive link to sever the selected conductive link.