Patent ID: 8198566
Filing Date: 2012-06-12
Classification: B23K,H01L

Abstract:
1. A method for laser processing a workpiece including a low-k dielectric material supported by a wafer substrate, comprising: generating a first laser output of a first set of laser pulses including at least first and second laser pulses having a first set of laser parameters including a pulsewidth shorter than 100 picoseconds and having a substantially raw Gaussian irradiance profile characterized by a center region of a raw peak irradiance amount and a peripheral region of a raw peripheral irradiance amount that is less than the raw peak irradiance amount; propagating the first set of lasers pulses of the first laser output along an optical path through a beam-shaping component that imparts greater uniformity to the first laser output to provide the first set of laser pulses with first shaped laser output such that the irradiance profile of the first set of laser pulses becomes characterized by a shaped peak irradiance amount that is reduced relative to the raw peak irradiance amount at the center region and by a shaped peripheral irradiance amount that is increased relative to the raw peripheral irradiance amount at the peripheral region determined by a shaped perimeter; propagating a major portion of the first shaped laser output of the first set of laser pulses through a generally noncircular aperture positioned along the optical path at a distance optically downstream of the beam-shaping component and configured to convert the major portion of the first shaped laser output into first shaped apertured output such that the irradiance profile of the first set of laser pulses becomes characterized by an apertured peripheral region having a generally noncircular cross section and an apertured perimeter that is smaller the shaped perimeter; directing the first shaped apertured output to impinge the low-k dielectric material such that the first and second laser pulses form first and second noncircular spot areas in the low-k dielectric material causing removal of an amount the low-k dielectric material, the second spot area partly overlapping the first spot area by a spot overlap region on the low-k dielectric material, the spot overlap region determining a spot nonoverlap nonregion of the second and first spot areas that corresponds to a bite size of the second laser pulse, the bite size being set within a range from 1 nm to 10 μm, and the beam shaping component, the generally noncircular aperture, the pulsewidth, and the bite size cooperating to cut through the low-k dielectric material such that the cut forms a kerf having a substantially flat and clean bottom and the substrate is undamaged.