Link processing using laser pulses with specially tailored power profiles

Abstract

A laser pulse with a specially tailored temporal power profile, instead of a conventional temporal shape or substantially square shape, severs an IC link. The specially tailored laser pulse preferably has either an overshoot at the beginning of the laser pulse or a spike peak within the duration of the laser pulse. The timing of the spike peak is preferably set ahead of the time when the link is mostly removed. A specially tailored laser pulse power profile allows the use of a wider laser pulse energy range and shorter laser wavelengths, such as the green and UV, to sever the links without appreciable damage to the substrate and passivation structure material located on either side of and underlying the links.

1 . A laser-based processing method of removing target material from selected electrically conductive link structures of redundant memory or integrated circuitry, each selected link structure including a link having opposite side surfaces and top and bottom surfaces, the opposite side surfaces being separated by a distance that defines a link width, at least the side and bottom surfaces being positioned adjacent passivation structure material in a circuit fabricated on a substrate, comprising:
 directing a laser output pulse for incidence on a selected link structure, the laser output pulse being in the form of a unitary pulse characterized by a laser spot and a laser pulse temporal power profile;   the laser spot having a spot size at a laser spot position on the selected link structure, the spot size being larger than the link width; and   the laser pulse temporal power profile having rising and falling edges, an average power, and a pulse duration and characterized by a power spike, the power spike having a spike duration that is substantially shorter than the pulse duration, a peak power that is greater than an average power of the laser output pulse, and a time of occurrence from the rising edge to the falling edge, and the peak power, spike duration, and time of occurrence of the power spike cooperating to establish for the laser output pulse a specially tailored laser pulse power profile that effects severing of the selected link structure while not causing appreciable damage to the substrate or the passivation structure material positioned adjacent the side and bottom surfaces.   
   
   
       2 . The laser processing method of  claim 1 , in which the power spike is coincident with the rising edge of the laser pulse temporal power profile and has a peak power value that is more than about 10% over the average power of the laser output pulse.