Ultrashort laser pulse wafer scribing

摘要

Systems and methods are provided for scribing wafers with short laser pulses so as to reduce the ablation threshold of target material. In a stack of material layers, a minimum laser ablation threshold based on laser pulse width is determined for each of the layers. The highest of the minimum laser ablation thresholds is selected and a beam of one or more laser pulses is generated having a fluence in a range between the selected laser ablation threshold and approximately ten times the selected laser ablation threshold. In one embodiment, a laser pulse width in a range of approximately 0.1 picosecond to approximately 1000 picoseconds is used. In addition, or in other embodiments, a high pulse repetition frequency is selected to increase the scribing speed. In one embodiment, the pulse repetition frequency is in a range between approximately 100 kHz and approximately 100 MHz.

主权项

1. A method of cutting a work piece including one or more layers formed over a substrate, the method comprising:
generating a beam of laser pulses; shaping the generated beam of laser pulses only through diffraction to produce spatial irradiance profiles with flattened tops, 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 in the one or more layers, the kerf passing through the one or more layers to a top surface of the substrate.