US 7,605,343 B2
Micromachining with short-pulsed, solid-state UV laser
Weisheng Lei, Portland, Oreg. (US); Glenn Simenson, Portland, Oreg. (US); Hisashi Matsumoto, Hillsboro, Oreg. (US); and John Davignon, Hillsboro, Oreg. (US)
Assigned to Electro Scientific Industries, Inc., Portland, Oreg. (US)
Filed on May 24, 2006, as Appl. No. 11/440,697.
Prior Publication US 2007/0272667 A1, Nov. 29, 2007
Int. Cl. B23K 26/38 (2006.01)
U.S. Cl. 219—121.71 32 Claims
OG exemplary drawing
 
1. 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.