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 laser system for severing a conductive link in an integrated circuit (IC), comprising: 
 a laser source operable to generate a beam comprising at least two laser pulses, the laser pulses including a first laser pulse and a second laser pulse; and    a beam positioning system operable to utilize position data representative of locations of one or more conductive links and to coordinate directing the laser pulses to a 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, the first and second laser pulses are sequentially directed to the selected conductive link, at least one of the first and second laser pulses is insufficient to sever the selected conductive link, and the laser pulses sever the selected conductive link.    
     
     
         2 . The system of  claim 1 , comprising a focusing lens between the laser source and the integrated circuit, wherein the focusing lens is in relative movement with respect to the selected conductive link while the laser pulses are directed to the selected conductive link.  
     
     
         3 . The system of  claim 1 , comprising a laser pulse gating device between the laser source and the integrated circuit.  
     
     
         4 . The system of  claim 1 , wherein the selected conductive link comprises a link of a memory device or a logic device.  
     
     
         5 . The system of  claim 1 , wherein a passivation layer overlies the selected conductive link.  
     
     
         6 . The system of  claim 1 , wherein a burst comprising the laser pulses has a width less than 500 ns.  
     
     
         7 . The system of  claim 6 , wherein the burst comprises more than two laser pulses.  
     
     
         8 . The system of  claim 1 , wherein the second laser pulse starts after the end of the first laser pulse.  
     
     
         9 . The system 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 system of  claim 1 , wherein the selected conductive link has a width less than or equal to about 1 μm.  
     
     
         11 . The system of  claim 1 , wherein the laser source includes a mode locked laser.  
     
     
         12 . The system of  claim 1 , wherein the first and second laser pulses produce first and second laser spots, respectively, that overlap at the selected conductive link.  
     
     
         13 . The system of  claim 1 , wherein each of the first and second laser pulses has a single peak pulse shape.  
     
     
         14 . The system of  claim 1 , wherein the laser pulses have an ultraviolet (UV) or near UV wavelength.  
     
     
         15 . The system 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 system of  claim 1 , wherein the laser source includes a Q-switched laser.  
     
     
         17 . The system of  claim 1 , wherein the laser source includes 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 system of  claim 1 , wherein at least one of the laser pulses has a pulse width of less than 25 picoseconds.  
     
     
         19 . The system of  claim 1 , wherein the beam positioning system is operable to direct a first set of two or more laser pulses and a second set of two or more laser pulses to sever respective conductive links, wherein the laser pulses in the first and second sets have different energy density profiles.  
     
     
         20 . The system of  claim 1 , wherein the first and second laser pulses have different energy characteristics.  
     
     
         21 . The system of  claim 1 , wherein the first and second laser pulses have different energy densities.  
     
     
         22 . The system of  claim 1 , wherein the laser pulses have a harmonically converted wavelength.  
     
     
         23 . A laser system for severing a conductive link in an integrated circuit (IC), comprising: 
 a laser source operable to generate at least two laser pulses, the laser pulses including a first laser pulse and a second laser pulse, and each of the first and second laser pulses producing a laser spot at the integrated circuit; and    a beam positioning system operable to utilize position data representative of locations of one or more conductive links and to coordinate directing the laser pulses to a 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, the first and second laser pulses are sequentially directed to the selected conductive link, at least one of the first and second laser pulses is insufficient to sever the selected conductive link, and the laser pulses sever the selected conductive link.    
     
     
         24 . A laser system for severing a conductive link in an integrated circuit (IC), comprising: 
 a laser source operable to generate at least two laser pulses, the laser pulses including a first laser pulse and a second laser pulse; and    a beam positioning system operable to utilize position data representative of locations of one or more conductive links and to coordinate directing the laser pulses to a selected conductive link, wherein the first and second laser pulses are sequentially directed to the selected conductive link, at least one of the first and second laser pulses is insufficient to sever the selected conductive link, and the laser pulses sever the selected conductive link.    
     
     
         25 . A laser system for severing selected conductive links in an integrated circuit (IC), comprising: 
 a laser for generating for each selected conductive link two or more laser pulses, each of the laser pulses producing a laser spot at the integrated circuit, wherein at least one of the laser pulses is insufficient to sever the selected conductive link; and    a beam positioner for providing continuous relative movement between the laser spots and the selected conductive link, and for directing the laser pulses to the selected conductive link so that the laser pulses sever the selected conductive link.