Patent ID: 8624157

Claim:
A method of cutting a work piece including a plurality of layers formed over a substrate, each of the plurality of layers having a respective laser ablation threshold that varies with laser pulse width, the method comprising: determining a minimum laser ablation threshold for each of the plurality of layers; selecting the highest of the minimum laser ablation thresholds; generating a beam of laser pulses having a fluence in a range between the selected laser ablation threshold and approximately ten times the selected laser ablation threshold; shaping the generated beam of laser pulses through diffraction to convert the laser pulses into flat laser pulses with substantially uniform spatial irradiance profiles, wherein the shaping produces, at the work piece, a series of laser spots with edges that are flattened, each including an asymmetrical aspect ratio with a first dimension being longer than a second dimension, the shaping spatially spreading the energy of each of the laser pulses as the aspect ratios of the respective laser spots change from symmetrical to asymmetrical; aligning the longer first dimension of each laser spot in a cutting direction along the work piece so as to distribute the energy of each laser pulse in the cutting direction; and providing relative movement, in the cutting direction, between the beam and the work piece so as to scribe a kerf between a plurality of integrated circuits formed in the plurality of layers, the kerf passing through the plurality of layers to a top surface of the substrate.