Patent•
Laser system and method for processing a memory link with a burst of laser pulses having ultrashort pulse widths
09 Jan 2001-
TL;DR: In this paper, a burst of ultrashort laser pulses is employed to sever a conductive link in a nonthermal manner and offers a wider processing window, eliminates undesirable HAZ effects, and achieves superior severed link quality.
Abstract: A burst of ultrashort laser pulses is employed to sever a conductive link (22) in a nonthermal manner and offers a wider processing window, eliminates undesirable HAZ effects, and achieves superior severed link quality. The duration of the burst is preferably in the range of 10 ns to 500 ns; and the pulse width of each laser pulse within the burst is generally shorter than 25 ps, preferablyshorter than or equal to 10 ps, and most preferably about 10 ps to 100 fs or shorter. The burst can be treated as a single 'pulse' by conventional laser positioning systems (62) to perform on-the-fly link removal without stopping whenever the laser system (60) fires a burst of laser pulses at each link (22). Conventional wavelengths or their harmonics can be employed.
Citations
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19 Dec 2000
TL;DR: In this article, an energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided.
Abstract: An energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided. The system includes a controller for generating a processing control signal and a signal generator for generating a modulated drive waveform based on the processing control signal. The waveform has a sub-nanosecond rise time. The system also includes a gain-switched, pulsed semiconductor seed laser for generating a laser pulse train at a repetition rate. The drive waveform pumps the laser so that each pulse of the pulse train has a predetermined shape. Further, the system includes a laser amplifier for optically amplifying the pulse train to obtain an amplified pulse train without significantly changing the predetermined shape of the pulses. The amplified pulses have little distortion and have substantially the same relative temporal power distribution as the original pulse train from the laser. Each of the amplified pulses has a substantially square temporal power density distribution, a sharp rise time, a pulse duration and a fall time. The system further includes a beam delivery and focusing subsystem for delivering and focusing at least a portion of the amplified pulse train onto the target material. The rise time (less than about 1 ns) is fast enough to efficiently couple laser energy to the target material, the pulse duration (typically 2-10 ns) is sufficient to process the target material, and the fall time (a few ns) is rapid enough to prevent the undesirable changes to the material surrounding the target material.
234 citations
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14 Mar 2005
TL;DR: In this paper, a femtosecond laser based laser processing system has been proposed for the utilization of the unique heat control in micromachining, and the system has greater output beam stability, continuously variable repetition rate and unique temporal beam shaping capabilities.
Abstract: A femtosecond laser based laser processing system having a femtosecond laser, frequency conversion optics, beam manipulation optics, target motion control, processing chamber, diagnostic systems and system control modules. The femtosecond laser based laser processing system allows for the utilization of the unique heat control in micromachining, and the system has greater output beam stability, continuously variable repetition rate and unique temporal beam shaping capabilities.
190 citations
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03 Feb 2005
TL;DR: In this article, an apparatus, system and method for dicing of semiconductor wafers using an ultrafast laser pulse of femtosecond and picosecond pulse widths directly from the ultra fast laser oscillator without an amplifier is presented.
Abstract: The present invention relates to the apparatus, system and method for dicing of semiconductor wafers using an ultrafast laser pulse of femtosecond and picosecond pulse widths directly from the ultrafast laser oscillator without an amplifier. Thin and ultrathin semiconductor wafers below 250 micrometer thickness, are diced using diode pumped, solid state mode locked ultrafast laser pulses from oscillator without amplification. The invention disclosed has means to avoid/reduce the cumulative heating effect and to avoid machine quality degrading in multi shot ablation. Also the disclosed invention provides means to change the polarization state of the laser beam to reduce the focused spot size, and improve the machining efficiency and quality. The disclosed invention provides a cost effective and stable system for high volume manufacturing applications. An ultrafast laser oscillator can be a called as femtosecond laser oscillator or a picosecond laser oscillator depending on the pulse width of the laser beam generated.
172 citations
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07 Nov 2006TL;DR: In this article, a method and system for locally processing a predetermined microstructure formed on a substrate without causing undesirable changes in electrical or physical characteristics of the substrate or other structures formed on the substrate are provided.
Abstract: A method and system for locally processing a predetermined microstructure formed on a substrate without causing undesirable changes in electrical or physical characteristics of the substrate or other structures formed on the substrate are provided. The method includes providing information based on a model of laser pulse interactions with the predetermined microstructure, the substrate and the other structures. At least one characteristic of at least one pulse is determined based on the information. A pulsed laser beam is generated including the at least one pulse. The method further includes irradiating the at least one pulse having the at least one determined characteristic into a spot on the predetermined microstructure. The at least one determined characteristic and other characteristics of the at least one pulse are sufficient to locally process the predetermined microstructure without causing the undesirable changes.
147 citations
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11 Aug 2004
TL;DR: In this paper, the authors presented an object of the present invention to provide a laser irradiation apparatus which can form a linear beam spot with a short optical path length, and reduce displacement of a condensing point at opposite ends in a direction of its line.
Abstract: It is an object of the present invention to provide a laser irradiation apparatus which can form a linear beam spot with a short optical path length, form a linear beam spot being long in a long-side direction, and reduce displacement of a condensing point at opposite ends in a direction of its line. In a laser irradiation apparatus having an optical system for shaping a laser beam emitted from a laser oscillator into a linear beam spot having a long-side direction and a short-side direction, the optical system includes a long-side direction condensing cylindrical lens disposed between a first short-side direction condensing cylindrical lens and a second short-side direction condensing cylindrical lens. Displacement of a position of a homogeneous plane is generated by the long-side direction condensing cylindrical lens so that a distance from the homogeneous plane to the second short-side direction condensing cylindrical lens is constant not depending on a field angle.
137 citations
References
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29 Mar 1995TL;DR: In this article, the authors proposed a method for laser induced breakdown of a material with a pulsed laser beam where the material is characterized by a relationship of fluence breakdown threshold (Fth) versus laser beam pulse width (T) that exhibits an abrupt, rapid, and distinct change or at least a clearly detectable change in slope at a predetermined laser pulse width value.
Abstract: In one aspect the invention provides a method for laser induced breakdown of a material with a pulsed laser beam where the material is characterized by a relationship of fluence breakdown threshold (Fth) versus laser beam pulse width (T) that exhibits an abrupt, rapid, and distinct change or at least a clearly detectable and distinct change in slope at a predetermined laser pulse width value. The method comprises generating a beam of laser pulses in which each pulse has a pulse width equal to or less than the predetermined laser pulse width value. The beam is focused to a point at or beneath the surface of a material where laser induced breakdown is desired. The beam may be used in combination with a mask in the beam path. The beam or mask may be moved in the X, Y and Z directions to produce desired features. The technique can produce features smaller than the spot size and Rayleigh range due to enhanced damage threshold accuracy in the short pulse regime.
472 citations
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27 May 1998
TL;DR: In this paper, a refractive laser surgery process is disclosed for using compact, low-cost ophthalmic laser systems which have computer-controlled scanning with a non-contact delivery device for both photo-ablation and photo-coagulation in corneal reshaping.
Abstract: A refractive laser surgery process is disclosed for using compact, low-cost ophthalmic laser systems which have computer-controlled scanning with a non-contact delivery device for both photo-ablation and photo-coagulation in corneal reshaping. The basic laser systems may include flash-lamp and diode pumped UV solid state lasers (193-215 nm), compact excimer laser (193 nm), free-running Er:glass (1.54 microns), Ho:YAG (2.1 microns), Q-switched Er:YAG (2.94 microns), and tunable IR lasers, (750-1100) nm and (2.5-3.2) microns. The advantages of the non-contact, scanning device used in the process over other prior art lasers include being safer, reduced cost, more compact and more precise and with greater flexibility. The theory of beam overlap and of ablation rate and coagulation patterns is also disclosed for system parameters. Lasers are selected with energy of (0.01-10) mJ, repetition rate of (1-10,000), pulse duration of 0.01 nanoseconds to a few hundreds of microseconds, and with spot size of (0.05-2) mm for use with refractive laser surgery.
265 citations
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24 Feb 1998TL;DR: In this article, a method and apparatus is disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates.
Abstract: A method and apparatus is disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment
254 citations
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25 Jan 2001
TL;DR: In this article, the authors proposed a method of laser processing or laser modification of materials using a combination of ultrafast laser pulses and high-repetition rate (>100 kHz) bursts, which defines a new and unexpected regime for material processing.
Abstract: A method of laser processing or laser modification of materials. The combination of ultrafast laser pulses and high-repetition rate (>100 kHz) bursts (or continuous operation) defines a new and unexpected regime for material processing. The high repetition rate controls thermal and/or other relaxation processes evolving between each ultrafast laser pulse that ‘prepares’ the sample surface or bulk to alter the interaction with subsequent ultrafast laser pulses and thereby improve or optimize the process, or enable a new process, that are not available at lower repetition rate. The addition of this laser-controlled thermal component, and/or the general control of relaxation processes, overcomes several current limitations of ultrafast laser processing at lower repetition rates (<100 kHz), providing means to further harness the many attributes of ultrafast lasers for general material processing and material modification applications.
244 citations
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19 Dec 2000
TL;DR: In this article, an energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided.
Abstract: An energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided. The system includes a controller for generating a processing control signal and a signal generator for generating a modulated drive waveform based on the processing control signal. The waveform has a sub-nanosecond rise time. The system also includes a gain-switched, pulsed semiconductor seed laser for generating a laser pulse train at a repetition rate. The drive waveform pumps the laser so that each pulse of the pulse train has a predetermined shape. Further, the system includes a laser amplifier for optically amplifying the pulse train to obtain an amplified pulse train without significantly changing the predetermined shape of the pulses. The amplified pulses have little distortion and have substantially the same relative temporal power distribution as the original pulse train from the laser. Each of the amplified pulses has a substantially square temporal power density distribution, a sharp rise time, a pulse duration and a fall time. The system further includes a beam delivery and focusing subsystem for delivering and focusing at least a portion of the amplified pulse train onto the target material. The rise time (less than about 1 ns) is fast enough to efficiently couple laser energy to the target material, the pulse duration (typically 2-10 ns) is sufficient to process the target material, and the fall time (a few ns) is rapid enough to prevent the undesirable changes to the material surrounding the target material.
234 citations