Electro Scientific Industries, Inc.

Kevin P Fahey

Brian W Baird

Richard S Harris

Lian-Cheng Zou

Michael J Wolfe

Yunlong Sun

James N O'Brien

Thomas R McNeil

UV laser cutting throughput through silicon and like materials is improved by dividing a long cut path () into short segments (), from about 10 &#x3bc;m to 1 mm. The laser output () is scanned within a first short segment () for a predetermined number of passes before being moved to and scanned within a second short segment () for a predetermined number of passes. The bite size, segment size (), and segment overlap () can be manipulated to minimize the amount and type of trench backfill. Real-time monitoring is employed to reduce rescanning portions of the cut path(112)where the cut is already completed. Polarization direction of the laser output () is also correlated with the cutting direction to further enhance throughput. This technique can be employed to cut a variety of materials with a variety of different lasers and wavelengths.A multi-step process can optimize the laser processes for each individual layer.

Laser segmented cutting, multi-step cutting, or both

Laser segmented cutting

Patterns with feature sizes of less than 50 microns are rapidly formed directly in semiconductors, particularly silicon, GaAs, indium phosphide, or single crystalline sapphire, using ultraviolet laser ablation. These patterns include very high aspect ratio cylindrical through-hole openings for integrated circuit connections; singulation of processed die contained on semiconductor wafers; and microtab cutting to separate microcircuit workpieces from a parent semiconductor wafer. Laser output pulses () from a diode-pumped, Q-switched frequency-tripled Nd:YAG, Nd:YVO, or Nd:YLF is directed to the workpiece () with high speed precision using a compound beam positioner. The optical system produces a Gaussian spot size, or top hat beam profile, of about 10 microns. The pulse energy used for high-speed ablative processing of semiconductors using this focused spot size is greater than 200 &#x3bc;J per pulse at pulse repetition frequencies greater than 5 kHz and preferably above 15 kHz. The laser pulsewidth measured at the full width half-maximum points is preferably less than 80 ns.

Ultraviolet laser ablative patterning of microstructures in semiconductors

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Portland, OR, United States of America

Kevin P Fahey