Micromachining with short-pulsed, solid-state UV laser
AssigneeElectro Scientific Industries, Inc.
InventorsWeisheng Lei, Glenn Simenson, Hisashi Matsumoto, John Davignon
Life of this patent
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Abstract
In some embodiments, laser output including at least one laser pulse having a wavelength shorter than 400 microns and having a pulsewidth shorter than 1,000 picoseconds permits the number of pulses used to clean a bottom surface of a via or the surface of a solder pad to increase process throughput. An oscillator module in cooperation with an amplification module may be used to generate the laser output.
Claims32
A method for increasing laser via drilling throughput by minimizing a total number of pulses used to drill a via having desirable operational characteristics, wherein the total number N of pulses includes a bulk number N0 of bulk removal pulses employed to remove bulk material to form the via with a laser removal-bulk material interaction and a bottom surface cleaning number δN of bottom surface cleaning pulses employed to clean a bottom surface of the via with a laser cleaning-material interaction, comprising:
- generating, from a laser, laser output having a wavelength shorter than 400 nanometers, a fluence F, and at least one laser pulse having a pulsewidth τ, shorter than 1000 picoseconds, for cleaning the bottom surface of the via, where δN has a relationship to F/τ1/2 and such that δN/N0 is less than or equal to 1;
- and
- directing the laser output from the laser to a target position to remove a major portion of the bulk material and clean the bottom surface of a via, such that laser pulses of the laser output for removing the major portion of the bulk material and for cleaning the bottom surface of the via have a wavelength shorter than 400 nanometers and a pulsewidth shorter than 1000 picoseconds.
A method for laser drilling a blind via in a workpiece including a bulk material and an underlying bottom surface material wherein a laser-bulk material interaction determines a bulk set of optimal laser processing parameters for efficiently removing a major portion of the bulk material to form the blind via and wherein a laser cleaning-material interaction determines a cleaning set of optimal laser processing parameters for efficiently cleaning the bottom surface with a fewest number of bottom surface-cleaning pulses employed to clean the bottom surface of the blind via without causing operational damage to the bottom surface of the blind via, such that the cleaning set of optimal laser processing parameters is less efficient for removing bulk material than is the bulk set of optimal laser processing parameters, comprising:
- determining for a wavelength shorter than 400 nm optimal ranges of fluence, pulsewidth, and repetition rate within the cleaning set for minimizing the number of laser pulses to clean the bottom of a blind via,
- employing a solid-state laser to generate laser output at a wavelength shorter than 400 nanometers having parameters within the cleaning set of optimal laser processing parameters, the laser output including multiple laser pulses having pulsewidths shorter than 500 picoseconds;
- employing image-shaping optics to shape the laser output;
- and
- directing the multiple laser pulses of the laser output at a target position to remove the major portion of the bulk material to form the blind via in the workpiece and to clean the bottom surface material.
Dependencies are inferred from the claim text.