Energy efficient, laser-based method and system for processing target material

Abstract

An energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided. The system includes a controller for generating a processing control signal and a signal generator for generating a modulated drive waveform based on the processing control signal. The waveform has a sub-nanosecond rise time. The system also includes a gain-switched, pulsed semiconductor seed laser for generating a laser pulse train at a repetition rate. The drive waveform pumps the laser so that each pulse of the pulse train has a predetermined shape. Further, the system includes a laser amplifier for optically amplifying the pulse train to obtain an amplified pulse train without significantly changing the predetermined shape of the pulses.

1 . A method of using a laser to sever multiple selected target links in associated ones of multiple electrically conductive link structures fabricated in an integrated circuit, the target links formed with passivation layer material overlying electrically conductive link material, comprising:
 providing position data representative of locations of the multiple electrically conductive link structures;   generating, for emission and propagation along a beam axis, multiple laser pulses of which consecutive pulses have substantially no temporal overlap at or above a predetermined power level;   providing a beam positioning system that imparts rapid relative motion of the integrated circuit and the beam axis along which the multiple laser pulses propagate, the beam positioning system, in response to the position data, moving the beam axis between successive ones of the multiple selected target links and directing the beam axis to the multiple selected target links so that multiple ones of the laser pulses within a specified duration impinge on the link material of each of the multiple selected target links; and   coordinating control of the rapid relative motion of the integrated circuit and the beam axis and control of the impingement on the link material of the multiple ones of the laser pulses within the specified duration to successively remove, by interaction of the multiple ones of the laser pulses with the link material and without stopping the beam axis over any one of the multiple selected target links, portions of the overlying passivation layer material and link material to sever the multiple target links.   
     
     
         2 . The method of  claim 1 , wherein a pulse width of each of the multiple laser pulses impinging on the link material of any one of the multiple selected target links is less than 25 picoseconds. 
     
     
         3 . The method of  claim 1 , further comprising directing the multiple laser pulses through a gating device. 
     
     
         4 . The method of  claim 1 , wherein the multiple selected target links comprise links of a memory device or a logic device. 
     
     
         5 . The method of  claim 1 , wherein first and second pulse sets of the multiple ones of the laser pulses within the specified duration impinge on the link material of respective first and second selected target links, and wherein a repetition rate between the first and second pulse sets is greater than about 1 kHz. 
     
     
         6 . The method of  claim 5 , wherein the repetition rate is greater than about 20 kHz. 
     
     
         7 . The method of  claim 1 , wherein the specified duration has a range of between 10 ns and 200 ns and the multiple ones of laser pulses include a series of pulses. 
     
     
         8 . The method of  claim 1 , wherein at least one of the multiple selected target links has a width less than or equal to about 1 μm. 
     
     
         9 . The method of  claim 1 , wherein the multiple laser pulses form laser spots on the overlying passivation layer and link materials, and wherein the laser spots have the same spot sizes. 
     
     
         10 . The method of  claim 1 , wherein the step of generating the multiple laser pulses is performed using a mode locked laser. 
     
     
         11 . The method of  claim 1 , wherein the laser pulses within a specified duration produce corresponding laser spots at the integrated circuit, and wherein the laser spots overlap at one of the multiple selected target links. 
     
     
         12 . The method of  claim 1 , wherein each of the multiple laser pulses impinging on the link material of any one of the multiple selected target links has a single peak pulse shape. 
     
     
         13 . The method of  claim 1 , wherein the multiple laser pulses have a wavelength of less than 2000 nm. 
     
     
         14 . The method of  claim 1 , wherein the multiple laser pulses impinging on the link material of any one of the multiple selected target links have a total energy of about 0.02 nanojoules to about 3 microjoules per laser output pulse. 
     
     
         15 . The method of  claim 1 , wherein each of the multiple selected target links has a width, wherein the laser pulses within a specified duration produce corresponding laser spots at the integrated circuit, and wherein at least one of the laser spots has a spot size that is greater than one of the widths of the multiple selected target links. 
     
     
         16 . The method of  claim 1 , wherein the multiple laser pulses produce corresponding laser spots at the integrated circuit, and wherein the beam positioning system includes translation stages operable to support the integrated circuit and move any one of the multiple selected target links relative to the laser spots. 
     
     
         17 . The method of  claim 1 , wherein the step of generating the multiple laser pulses is performed using a Q-switched laser. 
     
     
         18 . The method of  claim 1 , further comprising changing an energy characteristic of at least one of the multiple laser pulses. 
     
     
         19 . The method of  claim 1 , wherein at least one of the multiple ones of the laser pulses removes a portion of the link material. 
     
     
         20 . The method of  claim 1 , wherein the link material of one of the multiple selected target links has a link thickness and at least one of the laser pulses within a specified duration removes from the one of the multiple selected target links a portion of the link material. 
     
     
         21 . The method of  claim 1 , wherein at least some of the laser pulses within a specified duration have different energy characteristics. 
     
     
         22 . The method of  claim 1 , wherein the step of generating the multiple laser pulses is performed by an operational configuration of a laser and an amplifier. 
     
     
         23 . The method of  claim 1 , wherein the beam positioning system includes a platform that supports the integrated circuit, and wherein the rapid relative motion includes motion of the platform as the laser pulses within the specified duration sever the multiple selected target links. 
     
     
         24 . The method of  claim 1 , wherein the specified duration of multiple ones of the laser pulses is in a range from several picoseconds to about 10 nanoseconds. 
     
     
         25 . The method of  claim 1 , further comprising operatively coupling a focusing lens to the beam positioning system, and wherein the rapid relative motion includes relative motion of the focusing lens with respect to the multiple selected target links as they are severed by the laser pulses within the specified duration. 
     
     
         26 . The method of  claim 1 , further comprising operatively coupling a focusing lens to the beam positioning system, and wherein:
 the multiple selected target links comprise links of a memory device or a logic device;   the specified duration of multiple ones of the laser pulses is in a range from several picoseconds to about 10 nanoseconds.   the multiple laser pulses have wavelengths between less than 2000 nm;   first and second pulse sets of the multiple ones of the laser pulses within the specified duration impinge on the link material of respective first and second selected target links, and a repetition rate between the first and second pulse sets is greater than about 1 kHz;   the laser pulses within the specified duration produce at the integrated circuit corresponding laser spots that overlap at one of the multiple selected target links; and   the rapid relative motion includes relative motion of the focusing lens with respect to the multiple selected target links as they arc severed by the laser pulses within the specified duration.   
     
     
         27 . The method of  claim 26 , wherein the specified duration is sufficient to ablate the conductive link and the multiple ones of laser pulses include a series of pulses including short pulses in rapid succession. 
     
     
         28 . A method of using a laser to sever multiple selected target links in associated ones of multiple electrically conductive link structures fabricated in an integrated circuit, the target links formed with passivation layer material overlying electrically conductive link material, comprising:
 providing position data representative of locations of the multiple electrically conductive link structures;   generating, for emission and propagation along a beam axis, a series of pulses including short pulses in rapid succession;   providing a beam positioning system that imparts rapid relative motion of the integrated circuit and the beam axis along which the series of pulses propagate, the beam positioning system, in response to the position data, moving the beam axis between successive ones of the multiple selected target links and directing the beam axis to the multiple selected target links so that multiple ones of the series of pulses within a specified duration impinge on the link material of each of the multiple selected target links; and   coordinating control of the rapid relative motion of the integrated circuit and the beam axis and control of the impingement on the link material of the multiple ones of the series of pulses within the specified duration to successively remove, by interaction of the multiple ones of the series of pulses with the link material and without stopping the beam axis over any one of the multiple selected target links, portions of the overlying passivation layer material and link material to sever the multiple target links.   
     
     
         29 . A method of using a laser to sever multiple selected target links in associated ones of multiple electrically conductive link structures fabricated in an integrated circuit, the target links formed with passivation layer material overlying electrically conductive link material, comprising:
 providing position data representative of locations of the multiple electrically conductive link structures;   generating, for emission and propagation along a beam axis, first and second output pulses, the duration of each pulse starting at 50% of peak pulse power and ending at 50% of peak pulse power, wherein the second pulse starts after the end of the first pulse;   providing a beam positioning system that imparts rapid relative motion of the integrated circuit and the beam axis along which the multiple laser pulses propagate, the beam positioning system, in response to the position data, moving the beam axis between successive ones of the multiple selected target links and directing the beam axis to the multiple selected target links so that multiple ones of the laser pulses within a specified duration impinge on the link material of each of the multiple selected target links; and   coordinating control of the rapid relative motion of the integrated circuit and the beam axis and control of the impingement on the link material of the multiple ones of the laser pulses within the specified duration to successively remove, by interaction of the multiple ones of the laser pulses with the link material and without stopping the beam axis over any one of the multiple selected target links, portions of the overlying passivation layer material and link material to sever the multiple target links.   
     
     
         30 . A method of using a laser to sever multiple selected target links in associated ones of multiple electrically conductive link structures fabricated in an integrated circuit, the target links formed with passivation layer material overlying electrically conductive link material, comprising:
 providing position data representative of locations of the multiple electrically conductive link structures;   generating, for emission and propagation along a beam axis, multiple laser pulses, the duration of each pulse starting at 50% of peak pulse power and ending at 50% of peak pulse power, wherein one of the multiple pulses starts after the end of an immediately preceding one of the multiple pulses;   providing a beam positioning system that imparts rapid relative motion of the integrated circuit and the beam axis along which the multiple laser pulses propagate, the beam positioning system, in response to the position data, moving the beam axis between successive ones of the multiple selected target links and directing the beam axis to the multiple selected target links so that multiple ones of the laser pulses within a specified duration impinge on the link material of each of the multiple selected target links; and   coordinating control of the rapid relative motion of the integrated circuit and the beam axis and control of the impingement on the link material of the multiple ones of the laser pulses within the specified duration to successively remove, by interaction of the multiple ones of the laser pulses with the link material and without stopping the beam axis over any one of the multiple selected target links, portions of the overlying passivation layer material and link material to sever the multiple target links.