CN101410219A - Laser-based method and system for removing one or more target link structures - Google Patents

Laser-based method and system for removing one or more target link structures Download PDF

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Publication number
CN101410219A
CN101410219A CNA2007800112965A CN200780011296A CN101410219A CN 101410219 A CN101410219 A CN 101410219A CN A2007800112965 A CNA2007800112965 A CN A2007800112965A CN 200780011296 A CN200780011296 A CN 200780011296A CN 101410219 A CN101410219 A CN 101410219A
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China
Prior art keywords
pulse
laser
target link
wavelength
link structures
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CNA2007800112965A
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Chinese (zh)
Inventor
古博
唐纳德·V·斯马特
詹姆士·J·考丁雷
乔汉·李
唐纳德·J·斯维特科夫
谢巴德·D·约翰逊
乔纳森·S·艾尔曼
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Novanta Inc
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GSI Lumonics Inc
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Publication of CN101410219A publication Critical patent/CN101410219A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/073—Shaping the laser spot
    • B23K26/0736—Shaping the laser spot into an oval shape, e.g. elliptic shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/40—Removing material taking account of the properties of the material involved
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
    • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
    • B23K26/0624—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses using ultrashort pulses, i.e. pulses of 1ns or less
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/77—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
    • H01L21/78—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
    • H01L21/82—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26

Abstract

Laser-based methods and systems for removing one or more target link structures of a circuit fabricated on a substrate includes generating a pulsed laser output at a predetermined wavelength less than an absorption edge of the substrate are provided. The laser output includes at least one pulse having a pulse duration in the range of about 10 picoseconds to less than 1 nanosecond, the pulse duration being within a thermal laser processing range. The method also includes delivering and focusing the laser output onto the target link structure. The focused laser output has sufficient power density at a location within the target link structure to reduce the reflectivity of the target link structure and efficiently couple the focused laser output into the target link structure to remove the target link structure without damaging the substrate.

Description

The removal based on laser of one or more target link structures
The cross reference of related application
The application require sequence number is 60/765,401, in the U.S. Provisional Application No. that on February 3rd, 2006 submitted to, this application is incorporated the application into way of reference on the whole.The application is that sequence number is 10/683,086, the part continuation application of the U. S. application that on October 10th, 2003 submitted to, this U. S. application 10/683,086 is again that sequence number is 09/941,389, the part continuation application of the U. S. application of submitting to August 28 calendar year 2001, U. S. application 09/941,389 is United States Patent (USP) 6 now, 727,458, name is called " the dynamical method and system based on laser that is used to handle target material ", this application 09/941,389 is again that sequence number is 09/473,926, the continuation application of the U. S. application of submitting on December 28th, 1999, U. S. application 09/473,926 is United States Patent (USP) 6 now, 281,471.United States Patent (USP) 6,281,471 disclosure is incorporated the application into way of reference on the whole.This application is again that sequence number is 10/107,890, name be called " being used for method and system " based on the many material devices of laser treatment of heat, the part continuation application of the U. S. application submitted on March 27th, 2002, this application 10/107,890 U.S. Provisional Application No. that require sequence number to be 60/279,644, to submit to March 29 calendar year 2001.The disclosure of U. S. application sequence number 10/107,890 is incorporated the application into way of reference on the whole, and this application is announced with U.S. Patent Application Publication No. 2002/0167581 now.
Background of invention
1. technical field
The present invention relates to the field of laser processing method and system, be specifically related to be used for removing the method and system that is formed on suprabasil one or more conduction one or more target link structures (target link structure).The present invention can be applicable to especially, but be not limited to the laser repairing of redundant semiconductor storage unit.
2. background technology
The size that economy and device performance have ordered about DRAM and logical device reaches very little physical size.In recent years, not only device is little, and interconnection and connector thickness also reduce sharp.
Oxide on some thermal laser processing dependence connectors of connector and the thermal dilation difference between the connector itself, as document HANDBOOK OF LASER MATERIALSPROCESSING, Chapter 19, pp.595-615, " Link Cutting/Making (the connector cutting/manufacturing) " among the Laser Institute of America (2001) is described.The fusion connector that different expansions causes oxide to comprise has built-in high pressure.Oxide on the connector must comprise connector and be in the sufficiently long time of molten condition, oxide is broken and very promptly removes metallic interconnect materials to set up enough pressure.If pressure is too low, connector just can not be removed clean.Optionally optical maser wavelength and laser controller are made every effort to increase laser " energy window " and are not damaged substrate and the material adjacent with connector.
Can find further information in the U.S. Patent application of following representational United States Patent (USP) and announcement about connector fusing (link blowing) method and system, comprise material processed, system's design and designs consideration: U.S. Patent number 4,399,345; 4,532,402; 4,826,785; 4,935,801; 5,059,764; 5,208,437; 5,265,114; 5,473,624; 6,057,180; 6,172,325; 6,191,486; 6,239,406; 2002-0003130; And 2002-0005396.
Provide about the connector processing of memory circuit or other representative document of similar laser treatment application background and comprise: " Laser Adjustment of Linear Monolithic Circuits (the laser adjustment of linear monolithic); " Litwin and Smart, ICAELO, (1983); " ComputerSimulation of Target Link Explosion In Laser Programmable Memory (Computer Simulation of the one or more target link explosion in the laser programmable storage), " Scarfone, Chlipala (1986); " Precision Laser Micromachining (accurately laser capture microdissection machining), " Boogard, SPIEVol.611 (1986); " Laser Processing for Application Specific Integrated Circuits (ASICS) (being used for the laser treatment that special IC is used), " SPIE Vol.774, Smart (1987); " Xenon Laser Repairs Liquid Crystal Displays (xenon laser repairing LCD), " Waters, Laser and Optronics, (1988); " Laser Beam Processing and Wafer ScaleIntegration (laser beam treatment and wafer scale are integrated), " Cohen (1988); " Optimization ofMemory Redundancy Link Processing (optimization that the memory redundancy connector is handled), " Sun, Harris, Swenson, Hutchens, Vol.SPIE 2636, (1995); " Analysis of Laser MetalCut Energy Process Window (the laser metal ablation energy is handled window analysis), " Bernstein, Lee, Yang, Dahmas, IEEE Trans.On Semicond.Manufact., Vol.13, No.2. (2000); " Link Cutting/Making (connector cutting/manufacturing) " in HANDBOOK OFLASER MATERIALS PROCESSING, Chapter 19, pp.595-615, Laser Instituteof America (2001).
The demand of dynamic random access memory of future generation (DRAM) comprises that the connector width is less than 0.5 micron and connector spacing (interval of center to center) the little spacing connector (fine pitch link) less than 2 microns (for example 1.33 microns).Present commercial lasers memory connector repair system is not well suited for satisfying the demand, described laser memory connector repair system use transfer Q, based on the solid state laser of neodymium, this laser wavelength is approximately 1 to 1.3 micron and pulse width and was approximately for 4 to 50 nanoseconds (ns).Large spot size (limited wavelength) and fuel factor (pulse width is limited) are two limiting factors.
The result that copper laser is handled is disclosed in INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURINGTECHNOLOGY (2001) 18:323-331.Use the Nd:YAG laser instrument of treble frequency, the pulse duration of described laser instrument is 50 nanoseconds (ns).Measured heat affected area (HAZ) is for 6 * 10 8W/cm 2Irradiation level be approximately 1 micron, and for being approximately 2.5 * 10 9W/cm 2Irradiation level then greater than 3 microns.
In order to solve described problem, people have carried out some trials.Can be with reference to following United States Patent (USP) and the application of being announced: 5,208,437; 5,656,186; 5,998,759; 6,057,180; 6,300,590; 6,574,250; WO 03/052890; And European patent EP 0902474.Generally speaking, traditional accent Q nanosecond solid state laser is because even its heat treatment essence in the time of the short wavelength, can not be handled little spacing connector.The interaction of material may be no thermal process basically when the femtosecond pulse width, but the complexity of femtosecond pulse laser, expensive and reliability may limit the realization of its reality.Support that the device and the material modification of laser repairing are expensive, and only so can not satisfy the demand.Need be used for improving one's methods of little spacing connector processing and overcome the problem relevant, and under repetitive rate, provide high effectively connector to remove with fuel factor with system, and the complexity that is not associated with the femto-second laser system.
Following list of references [1]-[12] are relevant with the present invention, and wherein some are here quoted:
[1] J.Lee, J.Ehrmann, D.Smart, J.Griffiths and J.Bernstein, " Analyzingthe process window for laser copper-link processing (analysis is used for the processing window that laser copper-connector is handled); " Solid State Technology, pp.63-66, December 2002.
[2] J.B.Bernstein, J.Lee, G.Yang and T.Dahmas, " Analysis of lasermetal-cut energy process window (laser metal-ablation energy is handled the analysis of window); " IEEE Semiconduct.Manufact., Vol.13, No.2, pp.228-234,2000.
[3] J.Lee and J.B.Bernstein, " Analysis of energy process window oflaser metal pad cut link structure (analysis of the energy process window of laser metal liner cutting connector structure); " IEEE Semicondut.Manufact., Vol.16, No.2, pp.299-306, May2003.
[4] J.Lee and J.Griffiths, " Analysis of laser metal cut energy processwindow and improvement of Cu link process by unique fast rise time laserpulse (the laser metal ablation energy is handled the analysis of window and the improvement of the copper connector being handled by unique fast rise time laser pulse); " Proceedings of Semiconductor ManufacturingTechnology Workshop, Hsinchu, Taiwan, pp.171-174, December 2002.
[5] T.Kikkawa, " Quarter-micron interconnection technologies for 256MDrams (1/4th microns interconnection techniques that are used for 256M DRAM); " Extended Abstracts, Int.Conf.Solid Devices and Materials, pp.90-92,1992.
[6] M.D.Perry, B.C.Stuart, P.S.Banks.M.D.Feit and J.A.Sefcik, " Ultrafast Laser for Materials Processing (ultrafast laser that is used for material processed), " be and pp.499-508 p.82, LIA Handbook of Laser Materials Processing, LaserInstitute of America, Magnolia Publishing, Inc., 2001.
[7] H.Liu, G.Mourou, Y.N.Picard, S.M.Yalisove and T.Juhasz, " Effectsof Wavelength and Doping Concentration on Silicon Damage Threshold (about the wavelength of silicon damaging thresholding and the influence of doping content), " Laser and Electro-Optics, Vol.2, p.2, May 2004.
[8] G.Pasmanik, " Pico versus Femto in Micromachining (psec and femtosecond micromachining), " June 2001. for Optoelectronics World, pp.221-224
[9] J.Jandeleit, G.Urbasch, H.D.Hoffmann, H.G.Treusch and E.W.Kreutz, " Picosecond Laser Ablation of Thin Copper Films (picosecond laser of thin copper film melts), " Appl.Phys., Vol.A 63, pp.117-121,1996.
[10] J.C.North and W.W.Weick, " Laser Coding of Bipolar Read-OnlyMemories (laser code of bipolar ROM), " IEEE Journal of Solid StateCircuits, Vol.SC-11, No.4, pp.500-505,1976.
[11] J.B.Bernstein, S.S.Cohen and P.W.Wyatt, " Metal Wire Cutting byRepeated Application of Low-Power Laser Pulses (by the metal wire cutting of repeated application low power laser pulse); " Rev.Sci.Instrum., 63 (6), pp.3516-3518,1992.
[12] M.Lapczyna, K.P.Chen, P.R.Herman, H.W.Tan and R.S.Marjoribanks, " Ultra high repetition rate (133MHz) laser ablation of aluminumwith 1.2-ps pulses (using superelevation repetitive rate (133MHz) laser ablation of the aluminium of 1.2ps pulse), " Appl.Phys., Vol.A 69[Suppl.], S883-S886,1999.
Summary of the invention
The purpose of at least one embodiment of the present invention provides the method for quality and the system of a kind of laser treatment that is used to improve the memory connector (for example, remove, melt, cut off, " fusing " etc.).
Another purpose of at least one embodiment of the present invention provides a kind of method and system that is used for the little spacing memory of laser treatment connector.
In order to realize above-mentioned purpose of the present invention and other purpose, a kind of method based on laser is provided, be used to remove the one or more target link structures that is formed on suprabasil circuit, and do not cause substrate, any dielectric layer between one or more target link structures and substrate or undesirable damage of the connector structure adjacent with one or more target link structures.One or more target link structures is positioned at one group of connector structure.At least some connector structures in this group connector structure can be separated less than the spacing of 2 μ m.Described method comprises that use has the seed laser of first predetermined wavelength, produces laser pulse sequence with the repetitive rate greater than about 1MHz.Described method also comprises at least a portion of optics amplifying laser pulse train, with the output pulse sequence that obtains amplifying.Described method also is included in during the relative motion of substrate, with the pulse transmission of the output pulse sequence that amplifies with focus on the described one or more target link structures.All output pulses of the output pulse sequence of described in fact amplification have pulse duration less than about 100 psecs, at about at least 10 of described one or more target link structures place 9W/cm 2Arrive less than about 1012W/cm 2Pulse power density and about 1.2 microns or the shorter wavelength of the correspondence in the scope.The power density of focusing pulse is low to moderate is enough to avoid undesirable damage.The gross energy height of all focusing pulses is also avoided other connector structure in described group the connector structure is caused undesirable damage simultaneously to being enough to remove one or more target link structures.Described focusing pulse to about 1 micron connector spacing in about 2 micrometer ranges provide 30% or above relative energy handle window.
Described generation step comprised the steps: before the optics amplification procedure, with the preposition pulse energy level that is amplified to of the output of seed laser.
Described method further comprises: before the optics amplification procedure, first predetermined wavelength is displaced to second wavelength.
Described method further comprises: after the optics amplification procedure, in position-based and the velocity information at least one and at least a portion of the output pulse sequence that controllably select to amplify so that one or more target link structures and laser beam position during relative motion synchronously.
Described method further comprises: before the optics amplification procedure, at least one in position-based and the velocity information and controllably select at least a portion of laser pulse sequence so that one or more target link structures and laser beam position during relative motion synchronously.
Described generation step comprises carries out gain switch to seed laser, so that pulse to be provided as required.
The time interval between the pulse of all in fact direct neighbors of described laser pulse sequence was at least 5 nanoseconds.The described step of controllably selecting is reduced to repetitive rate in the scope of about 20KHz to 150KHz.
Described laser pulse sequence comprises pulse duration at least one pulse greater than about 1 nanosecond.And described method further comprises: compression or described at least one pulse of cutting (slice), and to produce the pulse of pulse duration less than about 100 psecs.
Described seed laser is for transferring Q microlaser or laser diode, and its pulse duration is an about nanosecond.
The step of described compression or cutting was performed before the optics amplification procedure.
Described seed laser is a diode pumping solid laser.
Described diode pumping solid laser is a fibre laser oscillator.
Described seed laser is active or laser with active-passive lock mould.
Described seed laser is the high-speed semiconductor laser diode.
Described optics amplification procedure is carried out by at least one fiber amplifier.
The gain of described fiber amplifier is about 30dB.
The scope of described first predetermined wavelength is about 1.3 μ m to about 1.55 μ m, and described method further comprises: the optical maser wavelength of the output pulse sequence that amplifies is displaced to near-infrared or visible wavelength from first predetermined wavelength.
Described generation step utilizes master oscillator-power amplifier (MOPA) to implement.
The quantity of described output pulse and the speed of relative motion cause that the displacement of output pulse exceeds predetermined tolerance limit (tolerance).And described method further comprises: deflection output pulse, and will export pulse steering to the position that is positioned within the described predetermined tolerance limit.
In addition, in order to realize above-mentioned purpose of the present invention and other purpose, a kind of system based on laser is proposed, it is used to remove the one or more target link structures that is formed on suprabasil circuit, and does not cause substrate, any dielectric layer between described one or more target link structures and substrate or undesirable damage of the connector structure adjacent with described one or more target link structures.Described one or more target link structures is positioned at one group of connector structure.At least some connector structures in described group of connector structure can be separated less than the spacing of 2 μ m.Described system comprises the device that comprises seed laser, is used for producing laser pulse sequence with the repetitive rate greater than about 1MHz, and described seed laser has first predetermined wavelength.Described system also comprises and is used at least a portion that optics amplifies described laser pulse sequence, with the device of the output pulse sequence that obtains amplifying.Described system also comprises and is used for during substrate is with respect to the connector structure motion the pulse transmission of the output pulse sequence of described amplification and focuses on described one or more target link structures.All pulses of the output pulse sequence of described in fact amplification have pulse duration less than about 100 psecs, at about at least 10 of described one or more target link structures place 9W/cm 2Arrive less than about 10 12W/cm 2Corresponding pulse power density and about 1.2 microns or shorter wavelength in the scope.The power density of focusing pulse is low to moderate is enough to avoid undesirable damage.The gross energy height of all focusing pulses is also avoided other connector structure in described group the connector structure is caused damage simultaneously to being enough to remove one or more target link structures.Described focusing pulse to about 1 micron connector spacing in about 2 micrometer ranges provide 30% or above relative energy handle window.
The device that is used to produce comprises master oscillator-power amplifier (MOPA).
Described system further comprises: at least one in position-based and the velocity information and controllably select to amplify at least a portion of output pulse sequence so that one or more target link structures and laser beam position synchronous device during relative motion.The device that is used for controllably selecting comprises any one of acousto-optic modulator or electrooptic modulator.
The time interval between the pulse of all direct neighbors in fact of laser pulse sequence was at least 5 nanoseconds.The device that is used for controllably selecting is reduced to repetitive rate the scope of about 20KHz to 150KHz.
Described modulator is a Mach-Zehnder modulators.
Laser pulse sequence comprises pulse duration at least one pulse greater than about 1 nanosecond.Described system further comprises compressor reducer or pulse sheer, is used for compressing respectively or described at least one nanosecond pulse of cutting, to produce the pulse of pulse duration less than about 100 psecs.
Described seed laser is for transferring Q microlaser or laser diode, and its pulse duration is an about nanosecond.
The output of described compressor reducer or described sheer is used to the device reception that optics amplifies.
Described seed laser is a diode pumping solid laser.
Described diode pumping solid laser is a fibre laser oscillator.
Described seed laser is active or laser with active-passive lock mould.
Described seed laser is the high-speed semiconductor laser diode.
The described device that is used for the optics amplification comprises at least one fiber amplifier.
The gain of described fiber amplifier is about 30dB.
The scope of described first predetermined wavelength is that about 1.3 μ m are to about 1.55 μ m, and described system further comprises wavelength shift device (wavelength shifter), is used for the optical maser wavelength of the output pulse sequence of described amplification is displaced to near-infrared or visible wavelength from described first predetermined wavelength.
The described device that is used to produce comprises master oscillator, and the device that is used for the optics amplification comprises power amplifier (MOPA).
The quantity of output pulse and the speed of relative motion cause that the displacement of described output pulse exceeds predetermined tolerance limit.Described system further comprises the traffic beam deflector, is used for described output pulse steering to the position that is positioned within the described tolerance limit.
In addition, in order to realize above-mentioned purpose of the present invention and other purpose, a kind of method is proposed, be used to remove the selected one or more target link structures that is formed on suprabasil circuit, and do not cause to substrate, in undesirable damage of described selected one or more target link structures and any dielectric layer between the substrate or the connector structure adjacent with described selected one or more target link structures.Described selected one or more target link structures is positioned at one group of connector structure.At least some connector structures in described group connector structure can be separated less than the spacing of 2 μ m.Described method comprises laser focusing output is applied to described selected one or more target link structures, to remove described selected one or more target link structures during substrate is with respect to described laser output movement.Described laser output has about at least 70 pulses.All in fact described pulses have pulse duration less than about 100 psecs, at about at least 10 of described selected one or more target link structures place 9W/cm 2Arrive less than about 10 12W/cm 2The corresponding pulse power density of scope and about 1.2 microns or shorter wavelength.The power density of described pulse is low to moderate is enough to avoid undesirable damage.The gross energy height of all pulses is also avoided other connector structure in described group the connector structure is caused undesirable damage simultaneously to being enough to remove described selected one or more target link structures.The output of described laser provides 30% or above relative energy processing window to about 1 micron connector spacing in about 2 micrometer ranges.
The described step that applies is that to utilize wave-length coverage be about 1.0 μ m and is used for described wavelength-shift to the wavelength shift device of near-infrared or visible wavelength of described diode is implemented to the semiconductor laser diode of about 1.55 μ m, at least one fiber amplifier and at least one.
The wavelength of described laser diode is about 1.55 μ m, and described shifter is a frequency multiplier, and the wavelength after the displacement is about 0.75 μ m.
Described shifter is a triductor, and the wavelength after the displacement is a visible wavelength.
The pulse width of all in fact described pulses is corresponding to such duration, the energy density threshold (fluence threshold) that wherein is used to remove selected one or more target link structures is proportional with the square root of pulse width in fact, thereby described selected one or more target link structures is removed in the calorifics mode.
Passivation layer that described selected one or more target link structures is covered on one or more covers, and the power density of wherein one or more pulses produces thermal shock to the passivation layer that covers on one or more and removes passivation layer and the selected one or more target link structures that covers on one or more.The removal of described passivation layer that covers on one or more and described selected one or more target link structures is to realize because of thermal and mechanical stress and the effect of melting the two.
The described passivation layer that covers on one or more is an inorganic passivation layer, and its ABSORPTION EDGE (absorptionedge) is in the scope of ultraviolet wavelength, and described pulse power density is less than about 10 12W/cm 2
The scope of the pulse width of at least one in the described pulse is that about 30 psecs are to about 60 psecs.
The size of laser focusing output is less than about 1.5 microns.
Described laser focusing output comprises that at least one focuses on the pulse of non-circular hot spot, to improve the energy envelope (energy enclosure) of the laser focusing output in selected one or more target link structures.
The speed of number of pulses and described motion causes that the displacement of laser output exceeds predetermined tolerance limit.Described method further comprises: the deflection pulse with pulse steering to the position that is positioned within the described tolerance limit.
The step of described deflection utilizes acousto-optic device or electro-optical device to implement.
Described method further comprises carries out space segmentation (spatially splitting) at least one pulse of described laser output, to form the pulse of one group of space segmentation.Described method further comprise with at least one pulse choice in the space segmentation pulse guide to described selected one or more target link structures, or guide to the second selected one or more target link structures, or guide to this two selected one or more target link structures.
The described step that applies utilizes many lasing light emitters to implement.Described method further comprises: the output optics of above-mentioned lasing light emitter is combined in the common optical path.Described lasing light emitter is dissimilar, and in the lasing light emitter at least one comprises semiconductor laser diode.
Number of pulses is about 70-200.
The energy of at least one described pulse is about 5nJ or following.
In fact the energy of all pulses be about 1nJ or more than.
The output of described laser focusing produces size in about 0.1 micron heat affected area to about 0.85 micrometer range.
The size of described laser focusing output is less than about 1.0 microns.
The time interval scope of the pulse of at least two direct neighbors of described laser output is about 2 nanoseconds to about 10 nanoseconds, thereby corresponding to the effective repetitive rate of scope at the extremely about 500MHz of about 100MHz.The described time interval surpass by with the resolution time spacing of the steam that the last laser pulse produced/plasma plume brightness (plasma plume) of described selected one or more target link structures and the connector structural interaction adjacent with described selected one or more target link structures.
In fact the time interval between the pulse of all direct neighbors be about 5 nanoseconds or more than.
The scope of described pulse power density is about 10 9To about 10 11W/cm 2The pulse width range of at least one pulse is that several psecs are extremely less than about 50 psecs.
In addition, in order to realize above-mentioned purpose of the present invention and other purpose, a kind of method has been proposed, be used to remove the one or more target link structures that is formed on suprabasil circuit, and do not cause substrate, any dielectric layer between described one or more target link structures and substrate or undesirable damage of the connector structure adjacent with described one or more target link structures.Described method comprises: laser focusing output is applied to described one or more target link structures, to remove described one or more target link structures during substrate is with respect to described laser output movement.Described laser output has about at least 70 to 200 pulses.All in fact pulses have less than the pulse width of about 100 psecs with at about at least 10 of described one or more target link layer structure place 10W/cm 2Arrive less than about 10 12W/cm 2The corresponding pulse power density of scope and 1 micron or shorter wavelength.Described pulse to about 1 micron connector spacing in about 2 micrometer ranges provide 30% or above relative energy handle window.
Described wavelength can be less than about 800nm, and the pulse width of one of described pulse can be between about 30 psecs and about 60 psecs.
The described step that applies can be utilized wave-length coverage, and to be about 1.0 μ m be used for described wavelength-shift to the wavelength shift device less than 1 micron of described diode is implemented to the semiconductor laser diode of about 1.55 μ m, at least one fiber amplifier and at least one.
The wavelength of described laser diode can be about 1.55 μ m, and described shifter can be frequency multiplier, and the wavelength after being shifted can be about 0.75 micron.
Described shifter can be triductor, and the wavelength after being shifted can be visible wavelength.
The scope of described pulse power density can be about 10 9To about 10 11W/cm 2The pulse width range of at least one pulse in the described pulse can for several psecs to less than about 50 psecs.
The speed of number of pulses and described motion can cause that the displacement of laser output exceeds predetermined tolerance limit.Described method may further include: the described pulse of deflection with described pulse steering to the position that is positioned within the described tolerance limit.
The step of described deflection can utilize acousto-optic device or electro-optical device to implement.
In addition, in order to realize above-mentioned purpose of the present invention and other purpose, a kind of system has been proposed, be used to remove the one or more target link structures that is formed on suprabasil circuit, and do not cause substrate, any dielectric layer between described one or more target link structures and substrate or undesirable damage of the connector structure adjacent with described one or more target link structures.Described one or more target link structures is positioned at one group of connector structure.At least some connector structures in described group connector structure can be separated by the interval less than the center to center of 2 μ m.Described system comprises: comprise the device of laser subsystem and optical subsystem, described device is used between the moving period that substrate is exported with respect to laser, laser focusing output is applied on the described one or more target link structures to remove described one or more target link structures.Described laser output has at least 70 pulses.All in fact pulses have less than the pulse width of about 100 psecs with at about at least 10 of described one or more target link structures place 9W/cm 2Arrive less than about 10 12W/cm 2The corresponding pulse power density of scope and about 1.2 microns or shorter wavelength.The power density of described pulse is low to moderate is enough to avoid undesirable damage.The gross energy height of all pulses is also avoided other connector structure in described group the connector structure is caused undesirable damage simultaneously to being enough to remove described selected one or more target link structures.Described pulse to about 1 micron connector spacing to about 2 micrometer ranges provide 30% or above relative energy handle window.Described system also comprises and is used for described laser focusing is exported the positioning subsystem that is positioned on the one or more target link structures.
Described wavelength can be less than about 800nm.
Described laser subsystem can comprise that wave-length coverage is about 1.0 μ m and is used for described wavelength-shift with described diode to the wavelength shift device less than 1.2 microns to the semiconductor laser diode of about 1.55 μ m, at least one fiber amplifier and at least one.
Described shifter can be frequency multiplier, and the wavelength after being shifted can be about 0.75 micron.
Described shifter can be triductor, and the wavelength after being shifted can be visible wavelength.
The scope of described pulse power density can be about 10 9To about 10 11W/cm 2The pulse width range of at least one described pulse can for several psecs to less than about 50 psecs.
The speed of number of pulses and described motion can cause that the displacement of described laser output exceeds predetermined tolerance limit.Described system may further include the traffic beam deflector, is used for described pulse steering to the position that is positioned within the described tolerance limit.
Described deflector can be acousto-optic device or electro-optical device.
The detailed description of below reading in conjunction with the accompanying drawings preferred forms of the present invention being done, above-mentioned purpose of the present invention and other purpose, feature and advantage can be more clear.
The accompanying drawing summary
By means of following description, claims and accompanying drawing, these and other feature, aspect and the advantage that the present invention may be better understood, wherein:
Fig. 1 a is presented to be used to use at least one pulse to carry out the block diagram of the part of the laser processing system that connector removes at least one embodiment of the present invention;
The block diagram of the part of the external modulator subsystem of Fig. 1 b demonstration Fig. 1 a, wherein the part of the pulse train of Fang Daing is controllably selected " (on-the-fly) in real time " to be used for connector to handle;
Fig. 1 c is the schematical top view (not drawn on scale) of the one or more target link in row's connector, and this schematical top view has shown in the laser focusing output of connector between the moving period with respect to laser beam, on the one or more target link structures with the form of example;
Fig. 2 a-2b is the block diagram that shows some elements that are included in the optional solid state laser subsystem at least one embodiment of the present invention, and each solid state laser subsystem has master oscillator-power amplifier (MOPA);
Fig. 3 shows to be used to use a schematic representation of apparatus being with a plurality of laser instruments that postpone to trigger to come the combination laser pulse or producing the pulse train of tight spacing;
Fig. 4 is the different thermal characteristics of display application connector and its following substrate, the next curve map that does not damage the exemplary simulation results of substrate by applying two pulses removal connectors with predetermined delay;
Fig. 5 a be with the formal specification of example the curve map that concerns between heat affected area (HAZ), spot size and the connector spacing;
Fig. 5 b uses the material of nanosecond pulse to remove with the exemplary forms explanation;
Fig. 5 c is with the formal specification energy density threshold of the example curve map to the dependence of laser pulse width, and the figure illustrates exemplary pulse width range and exemplary pulse parameter corresponding to embodiments of the present invention;
Fig. 5 d is with the absorption coefficient of the formal specification silicon of the example curve map to the dependence of wavelength, and the figure illustrates the exemplary optical maser wavelength corresponding to embodiments of the present invention;
Fig. 6 a is the block diagram that shows the element of laser subsystem, and wherein the seed laser of Fig. 2 a or Fig. 2 b is the diode-pumped solid laser oscillator, and the diode-pumped solid laser amplifier is used to amplify the output of seed laser;
Fig. 6 b is the block diagram that shows the element of laser subsystem, and wherein the seed laser of Fig. 2 a or Fig. 2 b can be a picosecond laser diode or be used to produce the micro-slice laser of picopulse for example;
Fig. 7 a-7c shows the block diagram can be used for the optional additional design in embodiment of the present invention, comprises at least one configuration among amplification, wavelength-shift and " subtracting counting (down counting) "/" pulse-picked (pulsepicking) ";
Fig. 8 a-8c is the schematic diagram that shows typical master oscillator-power amplifier (MOPA) configuration detail that is used at least one embodiment of the present invention, wherein seed laser amplifies with the generation picopulse with at least one fiber amplifier, and comprises at least one modulator that is used for strobe pulse;
Fig. 9 is based on the block diagram of the memory repair systems of laser, and described memory repair systems comprises picosecond laser system, and has further shown the realization of embodiments of the invention;
Figure 10 a is the curve map of energy and relative processing window-spacing with Figure 10 b, illustrates to be used to use the individual pulse with 21 nanoseconds and 9 nanosecond pulse width to carry out the test result of connector fusing respectively;
Figure 11 a is the curve map of energy and relative processing window-spacing with Figure 11 b, illustrates to be used to use 50 pulse groups with 57 picopulses and 35 picopulses to carry out the test result of connector fusing respectively; And
Figure 12 a and Figure 12 b are the curve maps of energy and relative processing window-number of pulses, illustrates to be used to use pulse group 35 psecs, that wavelength is approximately 532 nanometers respectively 1 μ m spacing and 1.7 μ m spacings to be carried out the test result that connector fuses.
Detailed description preferred embodiment
Summary---laser system structure
With reference to figure 1a, it shows the part of explanation laser processing system 100 and shows the block diagram that is included in some the main system units at least one embodiment of the present invention, and described laser processing system is used for using at least one the output pulse 104 with picosecond pulse width (being the pulse duration etc.) 1041 (for example measuring at half power points) to remove conduction connector 107.At least one embodiment of the present invention can comprise diode pumping solid laser in subsystem 101, have the intermediate pulse 103 of the pulse width 1041 that is positioned at preferred picosecond scope with generation.Described laser instrument can be commercial obtainable for example diode-pumped solid (active or passive) mode-locked laser.In order to work at the preferred wavelength place, the output 103 of system 101 can be passed through optional shifter 105 (for example harmonic oscillator) wavelength-shift, for example is displaced to visible or near ultraviolet wavelength from near-infrared wavelength.
Individual pulse or a plurality of pulse can be selected and be passed to connector 107, and based at least one the physical property in connector 107, substrate 110, upper dielectric layer 1091 and the lower dielectric layer 1092, the pulse of being transmitted can have the predetermined pulse width and the time interval between the pulse (" time interval ").Beam delivery system can comprise Polarization Controller, relay optics (relayoptics), wave beam expansion, zoom optics (zoom optics) and object lens, and these object lens are used at the hot spot of connector 107 places generation near diffraction limited.Optionally external modulator subsystem 108 can move under computer control, so that the power of pulse and change pulse to be provided as requested.For instance, the pulse 102 in the impulse train 106 can be omitted (describing as dotted line).The patent No. is 5,998,759 and 6,281,471 United States Patent (USP) (for example, the 12nd hurdle the 63rd of ' 471 patent walks to the 14th hurdle the 33rd row and relevant drawings) tell about the use of modulator in laser processing system, with during the relative motion of connector and laser beam, provide pulse to come this connector of irradiation as requested.
With reference to figure 1b, it shows the block diagram of a part of the external modulator subsystem 108 of Fig. 1 a, and wherein the part of pulse train 103 controllably is selected for during the relative motion between substrate 110 and the laser beam (" in real time ") and handles connector.Motion can be carried out in three-dimensional: the X motion 113 of substrate 110, and Y motion (not shown), and the motion of the Z axle of at least one optical element 114 in beam delivery system, described substrate 110 is installed on the wafer stage usually.Be 6,114,118 and 6,483 referring to the patent No. that transfers assignee of the present invention please, 071 United States Patent (USP) has wherein been described and has been used for accurate positioning method and system that wafer and laser beam waist are positioned with respect to the connector position.Controller 121 common position-based information, velocity information, or position and speed information and produce control signal 122, described these information associate connector position and laser beam position.Control signal 122 common gatings (i.e. control) optical switch 120.Optical switch 120 provides output pulse 106 usually, and described output pulse 106 is parts of input pulse sequence 103.Therefore, when modulator (for example modulator 108) was used to select at least one output pulse 104 of the one or more connectors of irradiation (or other microstructure), the pulse 103 that is produced can have controlled the output repetitive rate and the time interval.At least one optical element 114 in the beam delivery system can be used at a high speed accurately aligned bundle waist, and the one-step optimization of going forward side by side focuses on the transmission of output pulse.
With reference to figure 1c, the exemplary pulse laser output on the one or more target link 107 comprises two laser focusing pulses 1042 corresponding to selected pulse 104, and described two laser pulses 1042 have the same spot size separately.Distance 1043 is corresponding to the time interval between the pulse during the relative motion 113.If distance 1043 accounts for the relatively little part of connector width, for example less than 25%, an energy part that then is enclosed in the connector will be roughly near desirable spot location.The effective dimensions of distance (or displacement) 1044 ordinary representation laser output, it equals laser spot size under ideal is provided with.When pulse increased at interval at that time, speed of related movement increased, and that is to say, should consider meticulousr connector spacing (spacing of center to center) 1043 more.
Transfer assignee of the present invention and incorporate U.S. Patent application 2002/0167581 the application, that announce here by reference into and described the whole bag of tricks and the subsystem of laser pulse being aimed at one or more connectors.Optical subsystem or variant can be incorporated into when needing in the beam delivery system among Fig. 1 a, described optical subsystem generally includes at a high speed, the single shaft deflector.Please specifically referring to the description of Figure 19 and the Figure 20 and the counterpart of ' 581, the further information of ' 581 disclosure to obtain.In addition, focus on output and can comprise a plurality of hot spots, described hot spot has at least one different hot spot and distributes or power density.For example, Figure 17 of above-mentioned disclosure has showed the focusing pulse as " removing light beam ".
With reference to figure 2a, it shows and can comprise in embodiments of the invention, the block diagram of the additional detail of an optional solid state laser subsystem.Seed laser (for example oscillator 211) produces pulse train 214, and these pulses have the enough energy that are fit to laser amplifier 212 amplifications usually.Seed laser can or be " gain switch " formula with set rate " free-running operation ", producing pulse under computer control.At least a portion of pulse train is amplified,, for example reach the energy level that cuts off (for example removing) connector with single pulse energy to obtain cutting off the essential pulsed laser energy of memory redundancy connector.For the stable and reliability service of impulse laser amplifier, an actual consideration scheme is to allow it be operated in the average power rating.Exercisable consideration scheme causes the engineering compromise between energy, umber of pulse and the repetitive rate in given pulse.
In an option means shown in Fig. 2 b (chi drafting not in scale), the available suitable modem devices 1081 of the part of pulse train 214 (with Fig. 1 a 108 similar or identical) is controllably selected, during the relative motion between substrate 110 and the laser beam (" in real time "), to handle connector, but, more than operation is to finish before the energy level that selected pulse train is being reached be used for connector to be handled through amplifier 212.The repetitive rate that " subtract counting ", " frequency division (divide down) " or " pulse-picked " operation can be used for mating laser amplifier 212, this repetitive rate can be the order of magnitude that is lower than the repetitive rate of seed laser 211.For example, if R is the repetitive rate of pulse train 214, then when every n pulse was selected, R/n was exactly the repetitive rate of the output of modulator 1081.If 214 expression 50MHz pulse trains, then the output of modulator is 50KHz when n=1000.In at least one embodiment, the repetitive rate of pulse train can be removed by non-integer (for example 19.98) and change in relatively little scope, and so that the position of selected pulse and connector is carried out synchronously, variation compensating to kinematic system thus.Such operation can realize by controller 121 in 108 and 1081 arbitrary or both, but and described operation position-based with and/or velocity information.
In at least one embodiment of the present invention, can select the pulse of a plurality of vicinities.For instance, the output 103 of laser amplifier 212,106 show the continuous amplification pulse of selecting of three couples from pulse train 214, the wherein specific then a pair of connector 107 that puts on alternatively provides the input repetitive rate of minimizing and low Mean Input Power for amplifier 212 simultaneously.If 214 expression 100MHz pulse trains, between a pair of continuous output pulse was 10 nanoseconds at interval.Throughput is normally relevant with repetitive rate.Preferably, amplifier output repetitive rate should be enough to provide connector processing frequency and " pulse (pulse on demand) is provided on request " ability fast, the complexity of restriction system position and/or speed control simultaneously.Preferably, three pairs of exemplary pulse at amplifier output 103,106 places can put on nearly three continuous connectors during the relative motion 113 of connector and laser beam.External modulator 108 can be used for stopping that laser energy arrival should processed connector.
Equally, depend on the spectral response of amplifier 212, optionally wavelength shift device 1051 can be used for Wavelength matched favourable (or compatible) wave-length coverage to amplifier 212 with seed laser 211.The specific design index that depends on application-specific, modulator subsystem 1081 and wavelength shift device 1051 can be used separately or be used in combination with subsystem 108, suitably to control final pulse interval and energy level.
With reference to figure 3, it shows a plurality of laser instruments that are used to use band to postpone to trigger and merges laser pulse or produce another option means of the pulse of a series of tight spacings.Predetermined delay (for example t1 to t2) between the trigger impulse can be multiple-pulse and uses definite time interval.The output that merges can be optical amplifier provides seed pulse.For example, two or more pulses (or impulse train) can be used for cutting off connector 107.Described device can be used for providing at interval meticulous control of time pulse (for example to every pulse to being 2 to 10 nanoseconds, 100 to 500MHz effective speeds or " burst transmission rates (burst rate) ").
As incorporating the application's here by reference into and the publication No. that transfers assignee of the present invention is 2002/0167581 (' 581) U.S. Patent application disclosed, laser system can comprise: programmable digital delay line 301, and it is used for control impuls time interval t2-t1; Laser instrument 302; Polarization tube 303, it is used for light beam and merges; And optional amplifier 304, it is used for promoting on request energy level.For instance, in order to understand additional details, please be concrete with reference to the 120th to 122 section, the 194th to 197 section and claim in ' 581.
The optical maser wavelength of subsystem 101 arrives in the scope of 1.3-1.55 micron at about 0.150 micron usually, and latter's scope is corresponding to the diode laser wavelength that uses in the high speed telecommunications.In one embodiment, optical maser wavelength can doubly be taken advantage of (for example three times) by frequency or with shifter 105 Raman shifts (Ramanshifted) to near-infrared, visible or ultraviolet wavelength.
● laser parameter and connector are removed
Be accompanied by the trend (being little spacing connector) that connector spacing and size reduce, the contiguous connector (not shown) of not damaging substrate 110 or may not needing to handle in order to remove connector 107 needs jointly to consider at least three parameters: (a) size of the laser beam on the target and its depth of focus; (b) the beam position precision (for example in the three dimensions with respect to the laser beam waist position of connector---at the Z axle of for example controlled X-Y motion and at least one element 114 between moving period); And (c) heat affected area (HAZ).
With reference to figure 5a, the connector spacing 521 in 3 to 5 micrometer ranges, its theoretical minimum spacing is followed formula:
Minimum spacing=wave beam radius+position error+0.5 connector width (1)
Wherein the fuel factor of laser beam is thought and can be ignored.
For example, the GSI Lumonics Model M430 memory repair systems of being made by assignee of the present invention provides the typical light spot size that is approximately 1.6 microns and be approximately+/-0.2 micron position error.Exemplary pulse widths is about 4-10 nanosecond, and this exemplary pulse widths is corresponding to the heat affected area of about .85-1.4 micron.
Model M430 system can handle the connector that minimum spacing is about 2 microns (supposing that the connector width is about 0.5 micron).
Yet when the connector spacing near with the comparable size of thermal diffusion length (thermal diffusion length) time, the fuel factors in connector 107 zones may significantly increase.So above-mentioned formula becomes:
Minimum spacing=wave beam radius+position error+0.5 connector width+HAZ (2)
Wherein, HAZ (heat affected area) the 522nd, the estimating of fuel factor.Heat affected area (HAZ) is usually by (D*t) 0.5Determine that wherein D is thermal diffusion coefficient and laser pulse width.The actual grade value of material thawing or vaporization also depends on actual energy and the power density on the target.
HAZ may extend beyond focal beam spot 523, thereby influences the outer peripheral areas adjacent with hot spot unfriendly.In some cases, the peripheral area that is influenced can be several times of hot spot itself.Bigger HAZ make usually laser treatment be difficult to control and than inaccuracy.With regard to connector fusing, bigger HAZ size also may be to one of limiting factor of the upper limit of handling window (adjacent connector damages).
The hot spot of diffraction limited and short optical maser wavelength (for example 0.355 micron) can alleviate the problems referred to above to a certain extent, and condition is that hot spot is correctly located with respect to connector.Yet, if the margin of system 524 (comprises X, Y, the Z motion subsystem) be+/-.1 micron (at the strict a little requirement of high speed connector processing), the spot size that needs are about 0.58 micron is passed to 0.38 micron wide connector with laser beam.Suppose 0.355 micron wavelength and the pulse width of 10 nanoseconds (ns), estimated HAZ is about 1.3 microns.Like this, being used to handle the physical constraints of connector can be corresponding to about 1.9 microns spacing.Therefore, expect less pulse width usually.
Reduce pulse width and also reduce HAZ usually.Yet, when fuel factor when beam sizes and site error become very little, there is no need further to reduce fuel factor before improving other important factor (beam size and location).Fuel factor is reduced to picosecond range from nano-seconds can be enough to handle littler spacing connector.For the processing of removing little connector spacing such as (for example excision, " fusing ", melt), can avoid further pulse width being reduced to the femtosecond scope and eliminate the fuel factor of not expecting.
According to the present invention, limited thermal interaction usually occurs in the heat affected area, and the heat affected area is in fact less than the accumulation tolerance limit of connector spacing and laser output with respect to the relative position of target structure.For example, about 0.3 micron to 1 micron heat affected area radius will provide the improved processing of 2 microns or littler connector spacing usually.Preferably, HAZ is less than the margin of laser output in the three dimensions (for example in all directions less than 0.1 micron, then be considered to usually and can ignore).
Here the sequence number of incorporating into way of reference is the reason that 6,281,471 United States Patent (USP) describes the pulse of using the short fast rise time in detail.Particularly, the 4th hurdle the 45th row-Di 5 hurdles the 19th row detailed description reduction reflectivity improve the effect to the coupling of target material.If the structural irradiation level of metallic target is greater than about 10 9W/cm 2, the reflectivity of target structure descends so, and the coupling of laser energy improves.Thermal diffusivity (relevant with HAZ) is usually along with the square root of pulse width changes.Short laser pulse usually reduces or stops in the substrate below the connector that dissipates the heat into fusing, and also reduces or stop hot cross conduction to the material adjacent with connector.
When the connector spacing became littler, the thermal interaction of nanosecond pulse can be more mixed and disorderly, and the accuracy that causes connector to be removed is not enough.Illustrated as Fig. 5 b, can heat and melt the material of larger volume, and the removal of material realizes by being discharged by the power-actuated fusing of the recoil of steam pressure and laser emission pressure.On fine dimension, the volume of the material of being removed and shape can be irregular, and comprise unacceptable huge statistical variation or dispersion (statistical variation).For the pulse of picosecond high-peak power, interacting becomes the non-linear form that statistical variation or dispersion descends, and originally this variation is accompanied by avalanche ionization, wherein descends owing to the high free electron density in the metal causes reflectivity.For such short pulse, laser energy is limited in the thin layer usually, and vaporizes fast usually.Start with the laser energy density that has descended and to melt, material is removed and is become usually more accurately and determine.Use the material removal of picosecond pulse can comprise that also spraying (solid and gas) by material removes heat in the laser treatment zone.For example be accompanied by the dielectric layer 1091 that covers and the existence of interior layer 1092, it can be the mixing of removing with thermal and mechanical stress by melting that the connector of picosecond is removed process.Under described pulse width and power density, in the connector processing region, remove heat by the material ejection, help the removal of one or more target link structures usually.
For instance, it (is 5 referring to the patent No. for example that Fig. 5 c shows for the variation of the energy density threshold of two kinds of example dielectric materials, people's such as 656,186 United States Patent (USP) and Du document, " Laser-Induced Breakdown by Impact Ionization in SiO 2With pulse widths from 7 nsto 150 fs are (by using the pulse duration effects SiO from 7ns to 150fs 2The laser-induced breakdown of internal ionization), " APPL.PHYS., Lett., 64 (23), June 6,1994, pp.3071-3073.As everyone knows, because metal has than higher free electron density energy density threshold lower usually (for example ten times or more) concerning metal.Under breakdown point, threshold value 501,502 changes with material, but statistical variation or dispersion (shown in error bar) is smaller usually.In illustrated example (data of announcing in document provide), 501 change with 1/ (pulse width), but the 502 approximate constants (as described in the patent of ' 186) that are taken as.On breakdown point, keep approximate root mean square relation, but be significantly, especially in the place of nanosecond with the variation that pulse width increases.
The exemplary pulse widths of the breakdown point of metal is generally about 10ps (for example, seeing that the patent No. is 5,656,186 United States Patent (USP)).According to the present invention, typical laser pulse width is less than 1 nanosecond, and most preferably, more approach the exemplary pulse widths of breakdown point, so that harmful fuel factor can be ignored (for example the present invention produces HAZ and the statistical variation or dispersion that has reduced).Yet connector of the present invention is removed normally thermal process of process.Because laser pulse width also preferably approaches breakdown point greater than the pulse width of breakdown point, the interaction between laser pulse and the material mainly is a thermal process (although extremely being weakened).
The present invention usually provides the process of connector removal efficiently, rather than by the etching process slowly that optical absorption depth defines, only is equivalent to the about several nanometers of each pulse concerning most of metals.Because breakdown point is by the material decision, therefore the low side of pulse width is also determined by material.The minimum pulse width of preferred pulse can be in several psecs (ps) to the scope of about 10ps.Maximum pulse is usually less than about 1 nanosecond (ns), and determined by admissible heat affected area usually.Usually, pulse width of the present invention from the breakdown point in scope less than 1ns.Pulse width can be within the scope 505 of about 10-100ps, for example 40-100ps.Most preferred pulse width arrives in the scope 506 of about 50ps to about 40ps or about 10ps at about 10ps.
The laser system that produces picopulse is than femto-second laser, and is simpler usually, more reliable and stable and cost efficiency is higher.Significant difference is to be used to produce the realization of the pulse compression of femtosecond high-peak power pulse.
A plurality of lists of references further describe the interaction in femtosecond-picopulse scope.For example, people such as Chichkov, " Femtosecond; Picosecond, and Nanosecond LaserAblation of Solids (femtosecond of solid, psec and nanosecond laser melt), " APPL.PHYS., A 63,109-115, and 1196 provide theoretical background and experimental result.Femtosecond pulse is found has the heat conduction that enters target, and reasonable down approximate, described hot conduction can be left in the basket, and described process is considered to the direct transformation from the solid to steam, thereby can obtain accurate laser treatment.Depth of ablation and laser pulse energy metric density be the number relation in pairs.For picopulse, melt and be accompanied by heat conduction and in the target of for example metal, form the fusion zone.When the heat conduction in entering target is left in the basket, (it is quite rough hypothesis), so for the picosecond pulse, depth of ablation becomes logarithmic relationship with energy density also be possible usually.Yet owing to have heat wave propagation and form big molten material layer, the processing in the nano-seconds is considered to more complicated usually.
People such as document Jandeleit, " Picosecond Laser Ablation of Thin Copper Films (picosecond laser of thin copper film melts); " APPL.PHYS., A 63,117-121,1996, disclose and melted result of experiment, wherein use the thin copper film internal drilling of picosecond pulse on fused silica.Though pulse width is followed square root relationship usually greater than the high strength picosecond pulse of the exemplary pulse widths of breakdown point, when than nanosecond with more during long pulse, heat affected area that reduces and lower thermic load provide the removal of Fast Heating and target material.On about 3.1 μ m diameter spot about 10 10-10 11W/cm 2Intensity, wavelength is every 40ps pulse of 1.053 microns, removes material of (on average) about .1-.2 μ m.With the result of the known optical absorption depth of the copper of 1.053 micron wave lengths relatively, illustrated that hot conduction determines depth of ablation usually.Pulse-pulse change in the removal material may be significant (for example, 2: 1).Yet HAZ is less relatively, and collateral damage is also minimum.
Therefore, for the whole system ability, than by reducing the beam and focus size and improve the benefit that position error provides, it is not remarkable usually to be reduced to the benefit that pulse width obtained that is lower than breakdown point (usually less than 10ps) from about 10-25ps.In addition, the cost in femtosecond laser source is more much bigger than the cost of picosecond laser system usually, particularly based on the picosecond laser system of optical-fiber laser.
Connector is handled the removal that comprises target structure, and target structure is metallic film normally.The material (for example, passivation layer 1091,1092, substrate 110) that connector is had different light and heat character usually centers on.Therefore, interact than the material processed with homogeneous " piece " material, some many materials interaction mechanism may some complexity.At least one dimension (for example, connector width) is equivalent to visible light or ultraviolet (UV) light wavelength usually.Also have, along with the more appearance of tang spacing technology, the designer of connector treating apparatus requires careful consideration and is enclosed in the interior that part of light spot energy of connector size.In at least one embodiment, optical maser wavelength for example, 0.90 micron or littler, realizes littler spot size on the connector to use the pulse width that reduces less than one micron.
Because minimum spot size is normally proportional with wavelength, thereby any the reducing in the wavelength all will help reducing of available minimum spot size.In addition, for same spot size, under so more short wavelength, depth of focus is bigger usually.For example, for the laser of 1064nm, the spot size of diffraction limited is approximately (promptly roughly, almost, approximately, substantially) 1.2 microns (the f values of the spot size of diffraction limited system=(constant) * wavelength * lens).When wavelength was reduced to 0.8 micron, the spot size of diffraction limited system also correspondingly reduced 20%, promptly reduced to about 0.9 micron.Usually handle for little spacing, preferably less than about 1.5 microns spot size, and most preferably 1 micron or littler.In at least one embodiment of the present invention, can use the light spot profile (for example, the oval hot spot that generates with the distortion optical subsystem) (for example, seeing that application number is 2002/0167581 United States Patent (USP)) of non-circle.Particularly, illustrated at least one embodiment non-circular hot spot is how can improve the energy that is closed in the connector in the 133-136 section.
May run into changes in material (for example, perhaps because design, owing to handle the variation that defective causes, perhaps as handling byproduct), and changes in material is handled energy window by expection along with spacing reduces further influence usually.Connector can be metal (for example aluminium, copper, a gold etc.), polysilicon, or the metal of infusibility.At least one deck silicon nitride (Si 3N 4) 1091 can cover connector, and silica (SiO 2) layer 1092 can separate substrate 110 and connector 107.Yet in some cases, connector may not covered by skin.In addition, the impurity of existence, the alloy in substrate or dielectric layer and dielectric of future generation (for example low dielectric constant polymeric material), each will substantially influence the optical characteristics of material.In greater than the ABSORPTION EDGE of dielectric 1091,1092 and wave-length coverage, use long laser pulse to be easy to cause substrate to damage less than the ABSORPTION EDGE of substrate 110.
For specific optical maser wavelength, connector 107 may come down to reflect.According to the present invention, laser output wavelength is usually less than the substrate ABSORPTION EDGE, and therefore corresponding to absorbing and/or the reflection wavelength zone.Optical maser wavelength is usually above the ABSORPTION EDGE of dielectric layer 1091,1092, and in one embodiment, dielectric layer can be inorganic, and for the general inorganic passivation layer that is used for semiconductor memory at present (Si for example 3N 4, SiO 2Deng), dielectric layer is usually corresponding to maximum in fact emitting area.
With reference to Fig. 5 d, its typical change that absorption coefficient of silicon is shown (for example, at room temperature), absorbs very high when the short wavelength.The doping (not shown) can change absorption usually, and the near infrared absorption limit is displaced to shorter wavelength.The announcement European patent application EP 0,902 474 that on March 17th, 1999 announced has been told about and has been used one or more material shielding substrates, damages to avoid substrate.Use described modification, more short wavelength's laser (and the spot size that reduces) can provide reducing of connector spacing.Shielding material can be a metal, refractory metal, or dielectric.Above-mentioned modification also can be used with the present invention, further to strengthen the property.
According to the present invention, optical maser wavelength can be in from about 0.4 μ m with in the scope of about 1.55 μ m.Exemplary wavelength can be ultraviolet range (for example, 514,212-266nm), near ultraviolet (for example 510,355nm), visible (for example 511, approximately 500nm, for example 532nm) and near infrared spectrum (512, about 750-850nm, or 513, about 1 μ m).As can be seen, silicon is absorbed in the whole wave-length coverage and changed about 1000: 1.Preferred wavelength can be at about .18 micron in the scope of about .55 micron.Its lower limit can be determined by the absorption of layer.For silicon base, when shorter wavelength, absorbing and reflecting all increases.On whole interested wave-length coverage, silicon semiconductor character sharply changes to the characteristic of the metalloid in the ultraviolet range near infrared similar dielectric characteristic.For silica and silicon nitride, in whole visible and near infrared range, internal transmission (internal transmission) and single surface are reflected constant substantially.The spectral transmission curve of general large band gap dielectric substance shows some decline of transmission when ultraviolet wavelength usually.For example, in laser science and technical manual (HANDBOOK OF LASER SCIENCE ANDTECHNOLOGY), the transmission range of silica is defined as the wavelength greater than .18 μ m.The absorption coefficient of silica and silicon nitride in visible wavelength region (＞400nm) all keep relatively low, and increase gradually in the UV wavelength range.
If presetted wavelength is positioned under the ABSORPTION EDGE of substrate, the pulse energy density of bases can reduce, and the processing window can pass through at least one increase in the following factors: (a) beam divergence (depth of focus is shallow); (b) dielectric surface reflection; (c) beam diffraction; (d) multiple scattering (for example causing) by alloy or impurity; (e) internal reflection (it can change along with the numerical aperture of focussed laser beam); (f) multi-coated interference; And (g) non-linear absorption in microstructure (if laser facula in three dimensions correctly the location, so in the forward position of high-peak power laser pulse, free electron density in the metal makes to absorb to be increased, and can realize the metallic interconnect materials removal to remove faster rate than substrate.Substrate is with disconnected physical efficiency (off-link energy) irradiation (for example, lower peak strength), and has than connector free electron still less.
In order to handle connector less than 0.5 micron thickness, for example aluminium or copper connector, peak energy denisty (joule/cm 2) scope is from about 0.2J/cm 2To 300J/cm 2, its representative value is at 2-80J/cm 2Scope.The peak power density scope is from about 5 * 10 9W/cm 2To 1.2 * 10 13W/cm 2, its representative value is 5 * 10 10W/cm 2-2 * 10 12W/cm 2Scope.For the laser of 40ps pulse width with 1 micron spot size, be used to cut off less than the pulse energy scope of the connector of 0.5 micron thickness usually in little joule of scope of 0.001-3, representative value is in little joule of scope of 0.02-1.
Pulse or multiple-pulse all can be used for removing connector.If pulse is used to remove connector, picosecond laser system provides the scope of little joule of the about 1-5 of every pulse usually with the 10KHz-120KHz repetitive rate.Exemplary range is from little joule to maximum 2 little joules less than about 1.Preferably, realize pulse processing, for example seed device (the seeder)/amplifier architecture shown in Fig. 2 a with oscillator/amplifier architecture.
In an embodiment of the invention, multiple-pulse can be used for removing connector, and wherein picosecond laser system provides at least 0.001 little joule of every pulse (1 receive joule (nj)) with 1MHz repetitive rate at least.In the three dimensions relative motion process between connector and laser beam (for example, along X-Y axle 5-50mm/sec), the pulse that puts on connector can be considered to remove the pulse of connector.In another embodiment of the invention, can apply about 15-20 pulse with the repetitive rate of 10-100MHz, each all has 1/10th of use pulse removal connector institute energy requirement these pulses, and the part of cross-section connector.
Embodiments of the present invention also can comprise the amplification pulse of a plurality of tight spacings, for example, two or more pulses, its each all have and use pulse to remove about 50% of the common institute of connector energy requirement.By the control of modulator subsystem 1081, external modulator subsystem 108 or its combination in the laser system 101, but strobe pulse.
In multiple-pulse is handled, can be according to the predetermined physical characteristic (for example, different thermal characteristics) of connector and material around, select to be used for as required the time interval between the pulse of irradiation connector.With reference to Fig. 4, it shows simulation result by way of example, and this result does not damage the effect of substrate by applying two pulses with predetermined delay, shown the different thermal characteristics of utilizing connector and its following substrate to remove connector.According to the simulation result that obtains (this situation is used the nanosecond pulse with square configuration), " two outburst " (for example two pulses) with 50% energy of " single burst (blast) " energy are very interesting.Silicon base plays a part heat sink usually, and than connector, described silicon base can be cooled off very fast.Shown in Fig. 5 a, its result shows that substrate 110 only just is stabilized to room temperature in 10 to 20ns.The recovery of connector 107 (copper) is very slow, and this has illustrated visibly different thermal characteristics.According to described result, second pulse also will be cleared up the residue of cutting position (being that connector is removed) usually, thereby cause " open circuit ".
For example, if use a 60MHz clamping system (for example, picopulse), the interval between the continuous impulse of the output train of impulses can closely be mated with predetermined interval.For example, if wish the bigger time interval, can use the High Speed Modulation apparatus to select any pulse train or impulse train.Higher repetitive rate can be used for reducing pulse interval, and second laser instrument perhaps can be provided as shown in Figure 3.For example, can produce two pulses, its each pulse width and 2-10ns at interval in all having from about 40ps to the 100ps scope.For instance, transfer the Q microlaser to can be used for providing the pulse width of several nanoseconds of the about 10KHz-100KHz of repetitive rate.Nanosecond pulse further can be handled (as shown, for example in the embodiment shown in Fig. 8 b), wherein high-speed modulator is used for " cutting " or compression pulse to picosecond magnitude, amplifies afterwards.About the further details of time pulse shaping, can be referring to the U.S. Patent number 6,281,471 and 4,483,005 that is transferred to assignee of the present invention (name is called " influencing pulse width ").
Can utilize other physical characteristic.Ultrashort pulse is applied to different materials, for example in 50 femtoseconds arrive several picosecond range, the plasma shield of laser beam is normally insignificant, described in several lists of references (for example, people such as Zhu, " Influence of Laser Parameters and MaterialProperties on Micro-Drilling with Femtosecond Laser Pulses (laser parameter and material behavior are to the influence of the micro-drilling of use femto-second laser pulse) ", APPL.PHY.A 67 (Suppl.) 5367-5371 (1999)).Although so efficient, has picopulse, can the coupling than the better laser energy of nanosecond pulse is provided near breakdown point and (for example, long 5% to 25% scope) preferred pulse width more longer than breakdown point not as operation in the femtosecond scope.For example, pulse can be at about 10ps to the scope of 100ps in, and most preferably at about 10ps in the scope of about 40ps, or approximately 10ps arrives in about 50ps scope.Than the coupling of the energy of long pulse, 10-30 nanosecond for example, because exhaust steam/plasma/plumage brightness, may serious degradation.In addition, but the light beam scattering of incident, and produce a large amount of disconnected physical efficiencys, this can reduce the processing energy window.
Therefore, although purpose for " in real time " removal, a series of picopulses are equivalent to a plurality of nanosecond pulses, but when use a plurality of pulses and each all have interpulse time interval of several at least nanoseconds, and the comprehensive interaction and the result of laser and material may be very different.U.S. Patent number 6,552,301 disclose the use of ultrafast laser train of pulse, and each pulse all has the pulse width less than about 10ps, and between each pulse, have the time interval, with utilize by last pulse and target material interaction was produced selected moment effect lasting.In addition, document " LaserMicromachining of Transparent Glasses and Aluminum with ps-pulse bursts at1054nm (clear glass of the picopulse string of use 1054nm and the laser capture microdissection machining of aluminium) ", Herman, CLEO 2000, CDF3, (2000), disclosing the 7.5ns pulse spacing has alleviated plumage brightness sink effect to a certain extent.The time interval can be after applying first high-peak power picopulse application, and the actual resolution time that is used for steam/plasma/plumage brightness according to (at least) to select in advance at interval.Typical scope is about 5 nanoseconds to hundreds of nanosecond.Additional pulse can be applied to effective coupling subsequently.
In relevant work, people such as Lapczyna [12] use from a plurality of locked mode 1.2ps pulse of the 133MHz of 1054nm laser instrument melts aluminium foil.Cut the hole by aluminium foil with 250 pulse trains of about 2 microseconds, described pulse has 1.2ps duration, the 7.5ns pulse interval to pulse.The duration of train of pulse near or be suitable in the time interval of " in real time " connector processing.Fig. 2 of document [12] shows the pulse train total energy density and the corresponding single pulse energy metric density of the aluminium foil that is used for the little processing different-thickness of laser.When nominal when being used for the typical light spot size of connector fusing, disclosed least energy scope will be in tens scopes of receiving joule in the document [12], and require consistent with connector fusing.
In addition, when having high power density (for example, 10 9-10 13W/cm 2) picopulse when being applied to connector, after connector is removed, for example in dielectric layer 1092 or other adjacent materials, the non-linear absorption that the depends on intensity projectile energy of can decaying, and can reduce the possibility that substrate or subsidiary connector damage.The existence of impurity (owing to design, or defective or byproduct are handled in conduct) lattice defect or various processing defectives can strengthen the non-linear absorption in one or more dielectric layers.In addition, some low-dielectric constant dielectric mediums are the optical characteristics of polymeric dielectric for example, can come the controlled removal of support material by non-linear absorption.
● the picosecond laser embodiment
Solid state laser (Nd:YAG for doping neodymium (Nd), Nd:YLF, Nd:YVO4) or for (for example mixing other rare earth element, ytterbium (Yb), neodymium (Nd), erbium (Er)) optical fiber laser, the solid state laser wavelength can be 1.3,1.18,1.09,1.064,1.053 or 1.047 microns.Preferred optical maser wavelength is secondary, three times, four times and the quintuple harmonics of these and other proper laser, obtaining littler spot size and bigger depth of focus, thereby satisfies the design objective of application-specific.For example, also (for example can use optical maser wavelength in ultraviolet, from the 355nm of triple-frequency harmonics, from the 266nm of four-time harmonic with from the 212nm of quintuple harmonics), visible (for example, 532nm from second harmonic), the lasing light emitter of near-infrared wavelength (700-900nm), with respect to traditional wavelength, these lasing light emitters can provide the improvement of spot size.The laser system that locked mode titanium sapphire ultrafast laser (mode-locked Ti:sapphire ultra fast laser) (no compressor reducer) comes to this, it produces the laser pulse of the pulse width of picosecond range to the 850nm scope at 750nm.Another is rare-earth metal doped optical fiber laser, and it is created in the wavelength of 800nm-980nm scope.
Now more detailed description can be comprised exemplary laser subsystem in embodiments of the invention.In the embodiment corresponding to Fig. 1 a, can comprise commercial obtainable diode pumping, passive mode-locking or active mode locking system.External modulator system 108 can be implemented, so that 106 selected pulse is passed to connector 107.
In Fig. 2 a, shown the another one laser configurations that can be used at least one embodiment of the present invention.In the MOPA configuration, psec seed laser (for example, oscillator produces the output in the scope that is used to amplify) and (power) amplifier system are used to obtain required pulse energy.
With reference to Fig. 6 a, it shows the block diagram of other details of explanation laser subsystem, and wherein the seed laser 211 among Fig. 2 a or Fig. 2 b is diode-pumped solid laser oscillators 602.Diode-pumped solid laser amplifier 603 can be used for amplifying the output of seed laser.Oscillator 602 can be a locked mode diode-pumped solid oscillator seed.External modulator subsystem 108 can be used for controlling the number of pulses on each connector and the time interval between the pulse.Than traditional Q-switched laser, mode locking oscillator is normally with the (＞1MHZ) operation of very high repetitive rate.Laser system also can comprise the modulator subsystem 1081 of Fig. 2 b, and when connector carried out the connector processing with respect to laser beam between moving period, control signal 202 (for example, in the typical range of 20-150KHz) was controlled at the number of pulses on each target.Under any circumstance, seed laser (for example, if it is fit to, can be the commercial obtainable lasing light emitter of encapsulation) can comprise an inner preamplifier, pulse energy is amplified to suitable scope, so that carry out power amplification with power amplifier 603.
But arrangement can comprise as the diode pumping of seed laser 602, locked mode, psec fibre laser oscillator.If diode pumping, solid amplifier 603 are fiber amplifiers, so just can construct the full optical fiber laser system.
In U.S. Patent No. 5,400, the typical optical fiber configuration that is applicable to amplification high power pulses, particularly ultrashort pulse is disclosed in 350,5,701,319 and 5,818,630.Typical laser instrument comprises Femtolite and the Wattlite series that the assignee IMRA of ' 350, He ' 630, ' 319 patent is provided.By the light source that ytterbium optical fiber amplifies based on Femtolite, realized reducing to the 0.1ps duration, mean power be 1 watt, the pulse of output wavelength in the 1.03-1.06 micrometer range.1.03-1.06 the wavelength of other of laser micrometer (for example, 780nm) and multiple frequence (second harmonic) output also can obtain from IMRA.In U.S. Patent No. 6,281, among the patent application WO 98/92050 of 471 (transferring assignee of the present invention) and international publication, also can obtain extra information.
Various other Solid State Laser amplifier configurations are applicable at least one embodiment of the present invention.The slab guide technology can be applicable to the amplification of high-peak power, short pulse well.Transfer assignee's of the present invention U.S. Patent Publication 2003/0161375,2003/0160034 and 2003/0021324, and relevant references, some orthoron embodiments are disclosed.Although not as the fiber amplifier technology realizes so easily, waveguide design can provide high-peak power output and high light beam quality, and does not have the Raman shift of undesirable seed wavelength.The slab guide amplifier also can be applicable to the femtosecond pulse amplifier well.
With reference to Fig. 6 b, it has shown the block diagram of the additional detail that optional laser subsystem is described, wherein the seed laser of Fig. 2 is the picosecond laser diode 611 that is used to produce picopulse.The diode seed laser can directly be modulated.
Alternatively, diode laser can be used for producing nanosecond pulse, and described nanosecond pulse is further processed in laser system to produce picopulse (for example more details that show with Fig. 8 b).
In another configuration in addition, seed laser 611 can be active or passive Q-adjusted micro-slice laser.An example of commercial obtainable microlaser is can be from the AOT-YVO-1Q of Advanced OpticalTechnology acquisition.For example AOT is provided at 2 feasible under 20KHz repetitive rate nanosecond pulse width.The frequency multiplication form also is feasible (532nm).JDS Uniphase also can provide micro-slice laser.In either case, modulator can be used for reducing pulse width, for example the more details that show with Fig. 8 b.Diode pumping optical fiber laser amplifier 612 can be used for amplifying the output of seed laser.
Embodiment preferred can comprise as the diode laser of seed device and optical fiber laser amplifier to obtain the picosecond laser pulse.Fiber laser system can have that volume is little, beam quality and control is good, system reliability is high, heat management is easy and operate non-maintaining advantage.U.S. Pat 6,281,471 and WO 98/92050 announced a plurality of features of master oscillator-power amplifier (MOPA), wherein used fiber amplifier to amplify the diode seed laser.
In at least one embodiment, for example,, told about the time interval of " gain switch " control impuls sequence that can be by seed laser in 471 as U.S. Pat 6,281.The design of high-speed pulse laser utilizes usually alone or in combination transfers Q, gain switch or mode-lock operation.If output stability can be accepted, can use " pulse pump " (for example, real-time control of the pump diode module of Fig. 6 a).U.S. Pat 5,812,569 disclose the typical method of the output energy that is used for the stable pulse solid state laser.
The output of laser subsystem 101 (and from amplifier 603) can be carried out wavelength by shifter 105 and move.The wavelength shift device or other wavelength shift devices that comprise the harmonic wave generation module, can be used for according to the demand of handling is shorter or longer wavelength with wavelength-shift.Wavelength-shift or converter technique are well-known, and are put down in writing.The example of wavelength shift device comprises Raman shift device, up-conversion or down coversion, frequency multiplication, or the like.For example, Concept Design Inc. provides secondary, three times and the four-time harmonic conversion of femto second titanium sapphire output (fundamental wavelength is in the 750-850nm scope), and the wavelength available of its generation is short to about 215nm.Coherent, Spectra Physics and Lumera provide the other products that comprises supper-fast frequency shifting device.
With reference to Fig. 7 a-7c, but it shows the block diagram that explanation can be used for the various arrangement in the laser subsystem 101.In Fig. 7 a, wavelength shift device 701 places between seed laser and the amplifier.In the case, the wavelength of seed laser and power amplifier is different.Therefore, carry out wavelength-shift, will be displaced to the wavelength in the power amplifier scope from the output wavelength of seed laser.The example of wavelength shift device comprises Raman shift device, up-conversion or down coversion, frequency multiplication, or the like.
Fig. 7 b has still illustrated another configuration, and wherein preamplifier 702 places between seed laser level and the power-amplifier stage.Preamplifier amplified the output of psec seed laser usually before power amplification, make pulse power usually in being suitable for the favourable scope that optical fiber laser amplifier (or other amplifiers that are fit to) amplifies.Preferably, preamplifier also is based on optical fiber.
Fig. 7 c has still illustrated the another one configuration, comprises the modulator 703 that places the power amplification front.Repetitive rate between power amplifier and seed laser will be used modulator (for example, down counter or frequency divider) not simultaneously usually.Usually, the repetitive rate of coming the self-locking mode seed laser is high relatively, and it is in the MHz scope.Yet because specified average power-limiting, the required repetitive rate of power amplifier can be several in the scope of hundreds of KHz.Therefore, described device is as " down counter " or " pulse-picked device " operation (for example, similar in appearance to or be equivalent to modulator subsystem and the optical switch of Fig. 1 a and 1b).Preferably, as modulator subsystem 108, optical switch is driven by the control signal of position-based and/or velocity information, and thereby synchronous with the miscellaneous part of laser processing system.The example of such down counter spare can be acousto-optic modulator or other high speed optical switch.Described device can use separately or be used in combination with modulator 108, is used to select to be passed to the pulse of connector or other target structures.Wavelength shift device 105 can place output place, as shown in Fig. 7 a-7c.
With reference to Fig. 8 a-8c, shown schematic block diagram, it illustrates in greater detail the structure that can be used for the typical laser system in embodiment of the present invention.For instance, seed laser can be commercial obtainable semiconductor laser diode, and amplifier system comprises at least one fiber amplifier, and can comprise several amplifying stages.
Fig. 8 a explanation has the seed laser of casacade multi-amplifier device.Usually, seed device (oscillator) is gone up repetitive rate to 100KHz or 10MHz with adjustable (that is, revisable, selectable, etc.), produces the pulse of psec duration (10ps-1ns).The 40-50ps duration that typical unit can have the 100KHz repetitive rate.Preamplifier and power-amplifier stage both are comprised.Based on the preamplifier 8111 of single mode optical fiber, preferred, will be amplified to from the pulse of seed device usually and cause in the saturated magnitude of last fiber optic power amplifier 8112 (it can be a casacade multi-amplifier).Usually be configured to based on the power amplifier of optical fiber the output energy level that produces about 5 little joules in 50 little joules scope, described output energy level is enough to satisfy the needs of removing the loss of connector and compensation optical system inside with pulse usually.For 1 micron output wavelength, the optical fiber of selecting for use ytterbium to mix usually.Described optical fiber can be to protect (PM) optical fiber partially.
But Fig. 8 b has shown the extra details of a structure that can be included in the arrangement in the embodiment of the present invention.The laser diode 821 of modulation can produce nanosecond pulse (not two pulses 8211 that proportionally show).Each pulse can be in the energy range of 1-200nj, and it has the exemplary pulse widths of about 2-10ns separately.Transfer the Q microlaser to can be used as the replacement of diode, can between two selections, weigh according to specific design consideration and index.Isolator 831 is generally used for reducing noise level, for example by the caused noise of back reflection.Described pulse is amplified by diode pumping (pump diode 824) and ytterbium amplifier 822 subsequently.Can amplify about 30dB, pulse energy be promoted to little joule of scope and overcome the various losses of internal system.
Second isolator 831 is generally used for reducing the noise level that caused by back reflection.Polarizer 826 is generally used for keeping the polarization of light beam, satisfying design objective, and Fiber Bragg Grating FBG (Fiber BraggGratings, FBG) 825 as wavelength sensitive filter.Pulse width can use subsequently very GHz intensity modulator at a high speed 827 by " cutting " to picosecond range, it preferably has the full power bandwidth of 10GHz at least.Alternatively, can realize configuration more efficiently as 827 by the Mach-Zehnder modulator, wherein nanosecond pulse is compressed into picosecond range, produces the pulse width of approximate 10ps scope.The output pulse 8271 of amplifying that shown (not proportionally), it is removed or is compressed part and dots.In the case, amplifier 822 is with final needed repetitive rate work.
Fig. 8 c has shown the structure detail of the optional seed amplifier that can be included in the embodiment of the invention and " pulse-picked device " configuration.Generally, the configuration of Fig. 8 c is similar to the configuration of Fig. 7 b, but does not for example have wavelength-shift.Picopulse 8311 can directly generate from seed diode 829, and perhaps the external modulation (not shown) by seed diode 829 generates with the final needed repetitive rate of several times (for example, the several times of 1-100KHz).Pulse energy can be about 1nj usually.As mentioned above, (for example be reduced to needed end value at pulse recurrence rate by using the modulator 1081 that is fit to as " down counter " or " pulse-picked device ", 1-100KHz) before, generally amplify (for example, about 30db) signal by amplifier 8111.Shown selected pulse 8281.
Selected picopulse 8281 can be exaggerated by extra level subsequently.Fig. 8 d has shown a kind of configuration of dual-stage amplifier.As mentioned above, parts can comprise the isolator 831 that reduces noise level, keep the polarizer 826 of light beam polarization and as the Fiber Bragg Grating FBG 825 of wavelength filter.Fiber amplifier 841 and 842 is usually all respectively by diode (or diode array) 8411 and 8421 pumpings.The first order can be 30dB, single mode, ytterbium amplifier.The second level can be " big mould " or " big core " the ytterbium amplifier with 30dB gain.The various known method of this area can be used for controlling output mould and corresponding beam quality, and (for example be used for noise (ASE) inhibition, referring to U.S. Patent number 5,818,630 and 5,400,350, and WO 98/92050), so that generation is near the output beam of diffraction limited, to be used to be sent to connector.The three-level system of Fig. 8 c-8d can be created in tens to the output that becomes in hundred little joules of scopes, its beam quality near diffraction-limited.
It is well-known to the method and system of fiber amplifier to transmit pump energy.For instance, Fig. 8 e has shown a kind of method that the diode laser energy is coupled into fiber amplifier by way of example.Dichronic mirror 850 and optical system (for example lens combination) combination by the optical fiber end 852 of vertically riving, are sent to pump light in the optical fiber 851 doping ytterbium, double clad.Amplifier output can be by similar light-dividing device transmission, and wherein pump energy 855 recycles by optical fiber.The technical staff can understand and understand, and other possible appropriate combination that are used for the dissimilar lasing light emitter of seed and amplifier laser instrument can be implemented, to satisfy the design objective of application-specific.
● typical optical fiber laser instrument standard
In at least one embodiment, semiconductor seed laser diode can use with one or more fiber amplifiers.Pulse recurrence rate at about 60MHz in 100MHz or higher scope.The umber of pulse that is used to handle single connector is adjustable to the pulse above 100.The preferred employing up to the speed of about 150KHz (150KHz train of pulse (burst) repetitive rate) carried out the connector processing.Also need the pulse width that to select.Feasible pulse width is preferably less than 100 psecs, for example in about 30 psecs in 60 psecs or shorter scope.The feasible single pulse energy that about 0.02-0.5 is little joule is handled for little spacing connector enough energy is provided, and is attenuated so that be applied to target by the output acousto-optic modulator.In a lot of suitable embodiments, the individual pulse energy of train of pulse can be positioned at 0.1 to be received joule and 100 receives joule, and this depends on the pulse number of application and the gross energy of train of pulse.Wish that pulse is the variation of several percentages or better to the stability of pulse.The high output beam quality of M2=1.1 provides near the diffraction limited hot spot to distribute.
In at least one laser diode fiber amplifier embodiment, can regulate envelope shape and duration.For example, can produce square configuration, or have the envelope of decay gradually.Such shape comes in handy for increasing the processing energy window.Can come modulation shape or duration by modulation seed laser diode or by the control amplifier pump diode.
In some laser diode embodiments based on optical fiber, infrared laser output will be displaced to shorter visible or near-infrared wavelength.As mentioned before, the optical maser wavelength in the subsystem 101 is usually located at about 0.150 micron and arrives in the scope of 1.3-1.55 micron, and latter's scope is corresponding to the diode laser wavelength that is used in the high speed telecommunications.In one embodiment, optical maser wavelength can several times (for example three times) frequently, or with shifter 105 carry out Raman shift to near-infrared, as seen or ultraviolet wavelength.The latter's 1.55 mum wavelengths can most preferably be diode, and can use the optical fiber technology that is used for telecommunications.Therefore frequency multiplication will produce the near-infrared wavelength of about 0.75 μ m, and be suitable for the corresponding spot size that very little spacing connector improves processing.
Laser system with typical laser diode-fiber amplifier standard, by IPG PhotonicsCorp.of Oxford, MA or other fiber laser system manufacturer produce.
● memory repair systems
With reference to Fig. 9, shown a block diagram based on the memory repair systems of laser, comprise picosecond laser system, and further specify a plurality of main system unit of the present invention.
Can realize using the station of micromachining completely of picosecond laser.At least one embodiment of picosecond laser system can be integrated in the M430 series of being produced by GSI Lumonics, or is integrated into other micro-machining systems that have suitable sub-micron tolerance limit and be used for the specification of high speed micromachining.The additional patent of listing below and institute's published application, it has transferred assignee of the present invention, has described the many aspects relevant with the method and system of memory repair:
1.U.S.Pat.No.5,300,756, name is called " Method and System for SeveringIntegrated-Circuit Connection Paths by a Phase Plate Adjusted Laser beam ";
2.U.S.Pat.No.6,144,118, name is called " High Speed Precision PositioningApparatus ";
3.U.S.Pat.No.6,181,728, name is called " Controlling Laser Polarization ";
4.U.S.Pat.No.5,998,759, name is called " Laser Processing ";
5.U.S.Pat.No.6,281,471, name is called " Energy Efficient, Laser-BasedMethod and System for Processing Target Material ";
6.U.S.Pat.No.6,340,806, name is called " Energy-Efficient Method and Systemfor Processing Target Material Using an Amplified, Wavelength-Shifted PulseTrain ";
7.U.S.Application Ser.No.09/572,925, name is called " Method and System ForPrecisely Positioning A Waist of A Material-Processing Laser Beam To ProcessMicrostructures Within A Laser-Processing Site ", submit on May 16th, 2000, and be published as WO 0187534 A2 December calendar year 2001, present U.S.Patent No.6,483,071, Division of S.N.09/572.925;
8.U.S.Pat.No.6,300,590, name is called " Laser Processing "; And
9.U.S.Pat.No.6,339,604, name is called " Pulse Controlin Laser Systems ".
Tell about according to this paper, be apparent that, the invention provides and be used to handle spacing less than 2 microns connector, wherein the heat affected area can be left in the basket, and does not have the complexity of fs-laser system.Can help accurate connector to remove with one or more picopulses.In addition, when comparing, can realize the removal of connector expeditiously, and, have the accuracy of improvement than traditional nanosecond connector processing method with etch processes slowly.Handle and in the high-rate laser treatment system, to realize according to connector of the present invention.
Embodiment, correction data and additional treatments method
At HANDBOOK OF LASER MATERIALS PROCESSING, Chapter 19, p.599, in Laser Institute of America (2001) " Link Cutting/Making (connector excision/making) ", notice and to have disclosed the suitable pulse energy scope that is used for particular procedure by quantity research.The coefficient of performance that is called as " laser energy processing window " generally is used to represent the characteristic of connector fusing performance.Typically study can just successfully excise the low-lying level E of connector LowThe several connectors on the typical wafer are smashed in beginning.Connector subsequently smashes with higher successively energy level, causes that up to pulse substrate or contiguous connector damage E HighThe minimum energy pulse of fusing connector and do not damage substrate or the highest energy pulse of contiguous connector between scope be " energy window ".Contiguous connector damages and (for example below) dielectric breakdown on every side, all is two key factors that are used to handle more and more importance of little pitch structure.
Laser energy processing window is the similar performance coefficient relatively.It is nondimensional normalization tolerance that this relative laser energy is handled window:
Relative energy is handled window=(E High-E Low)/(E High+ E Low)
Therefore window provides a kind of tolerance relatively, and this tolerance has reduced the dependence to Several Factors, comprises that changeability and the wafer in the laser system created conditions.Generally speaking, generation greater than 30% and the laser beam condition of more preferably handling window greater than 40% relative energy help the laser connector and handle, because when treatment conditions in time when changing with different production runs, connector is handled and can successfully be performed.
Test wafer manufactures has 4 kinds of different molten mass pitch structure (1.0,1.35,1.7 and 2.0 μ m), is used for the picosecond pulse laser test.The molten mass that is used for this research is approximately the constructed of aluminium that 0.35 μ m is wide and 0.4 μ m is thick (1% silicon, 0.5% bronze medal).Apply thick tin/titanium (TiN/Ti) layer of (overcoat) 0.05 μ m on the aluminium molten mass, and thick titanium (Ti) layer of (undercoat) 0.02 μ m is covered in primary coat.Silica (SiO by about 0.1 μ m 2) passivation layer formed, after the controllable oxidization etching process, be retained in the top of plating, to guarantee reliable laser ablation process.
In a series of tests, be used to finish the system of test based on GSI Group M 450 wafer repair systems.Pilot system comprises the locked mode solid state laser of 1.064 micron wave lengths, has the 50MHz frequency to produce the time interval of 20ns between the continuous impulse.Available laser system output pulse width is 57ps, 35ps and 8ps.For the train of impulses of N=50, total duration (train of pulse time) is 1 microsecond.The intensity section (time section) of laser output may be uniform or heterogeneous, and is the factor that can influence processing.Laser pulse is focused the minimum 1/e of about 1.35 μ m 2Spot size.Use the accurate wafer stage of M450, and objective table to cause the displacement of connector with respect to the speed of laser pulse at 50 impulse durations be about 0.1 μ m or littler.If the duration of train of pulse is slightly less than about 1 microsecond, the speed that then there is no need to slow down " in real time " handled.For example, for the objective table speed of 100mm/sec, the displacement of .1 μ m will take place in 1 microsecond, and if speed be increased to 200mm/sec .1 μ m displacement then will take place in 500 nanoseconds.Yet,, for example hundreds of nanosecond or still less, can not arrange the pulse of suitable quantity to realize effective connector fusing with suitable interpulse interval if the train of pulse time is too short.If necessary, can be by the relative objective table/beam motion that slows down, or, adopt duration greater than about 1 microsecond by using beam reflector, described beam reflector remains on light beam on the connector during long train of pulse.
Be applied to the number of pulses on the connector, can change along with the use of the acousto-optic modulator that is used for pulse-picked.Determine, for handling test wafers with 1.064 microns optical maser wavelengths, 50 pulses are optimum, and comprise and considering as 0.1 μ m micron displacement of above-mentioned pulse or still less.
For the comparative result of the train of pulse of single Donna scope second pulse width and many picosecond range pulse width, at Figure 10 a, Figure 10 b is shown in Figure 11 a and Figure 11 b.
Nanosecond pulse processing
Figure 10 a and Figure 10 b show the energy level and the relative energy processing window of each index in the test of carrying out with 21ns and the single infrared laser pulses of 9ns respectively.This has shown the connector disposal ability of using traditional nanosecond laser pulses (pulse of every connector).The value of handling window relatively is marked, and with reference to dexter second Y-axle.
For both of these case, in all structures, the high-end of laser energy window limited by adjacent connector damage.For 21ns and 9ns, handle window relatively and be in the scope of 27-67% and the scope of 11-62% respectively.For each structure, the laser energy gap between adjacent connector and silicon base are damaged in the situation of 21ns greater than situation at 9ns.This is because to provide the more time than long pulse be that the heat that produces of laser beam is in silicon base, interior diffusion.Be in identical energy level pulse also be considered to helpful than low peak power.These two kinds of effects all help avoiding silicon base to be damaged.On the other hand, cause the generation that the 9ns pulse causes that connector damages that is later than that adjacent connector damages than the 21ns pulse of low peak power, but not as the situation of silicon base damage so important.
The picopulse string
Figure 11 a and Figure 11 b show the result with the series processing connector structure of 50 pulses of 57ps and 35ps respectively.Pulse frequency is 50MHz.Therefore, the time interval between the pulse is 20ns, and pulse was applied by the duration (train of pulse time) with 1 μ s.
It should be noted that during meticulous stage movement, a plurality of pulses are applied to each one or more target link.Therefore, during each train of pulse, slight displacement takes place in the laser beam on the one or more target link.Under the present speed of accurately objective table and connector spacing, the displacement of 50 pulses is 0.1 μ m or still less.Increase frequency (minimizing pulse distance) with and/or the reflector of using compensation motion, be applied to the number of pulses of connector and during train of pulse applies, keep the little displacement of beam and focus on connector simultaneously for increase, all be optional.
Result from the 57ps pulse width shows, than the data of the nanosecond laser pulses shown in Figure 10 a and Figure 10 b, handles window and significantly improves.For most of structures, shown the upper bound (E of energy process window from the result of 57ps pulse width High) significantly increase, yet lower bound (E Low) increase mild relatively.Handle window relatively between 44% to 72%, and, improve especially remarkable for little pitch structure (1.35 μ m and littler pitch structure).Comparing with 21ns laser pulse result (0.27 and 0.44), is the structure of 1.0 μ m and 1.35 μ m for spacing, has realized 63% and 43% improvement of relative processing window respectively.
In Figure 11 a, see adjacent connector and the silicon base gap between damaging enjoyably, become relative nearer with comparing from the data of nanosecond laser pulses situation.This is owing to the bigger improvement that damages grade from adjacent connector, damages although main failure mode, remains the adjacent connector that runs through the spacing molten mass as the nanosecond laser situation.Though in picosecond several interaction mechanisms can take place, the experimental result prompting can be set up littler effective spot size by " thresholding ".Effectively spot size is considered to littler than the optical diffraction limited spot size calculated value of theory.Therefore, adjacent connector damages and has reduced than nanosecond laser pulses.The upper bound of handling window significantly improves.Multiple-pulse thresholding technology also can help to prevent the damage of the silicon base below the connector structure.Under 57ps laser pulse situation, it is lower slightly than the efficient of the thresholding on the silicon base that the thresholding on the adjacent connector is considered to, and adjacent connector damages the upper bound of having limited the processing window.
Figure 11 b be presented under the situation of pulse width of 35ps (except 1 μ m structure at interval), the upper bound of processing window is limited by the combination of two kinds of failure modes.Change sentence normally, for the structure of spacing from 1.35-2.0 μ m, data point shows that substrate damages and the damage of adjacent connector takes place simultaneously.
Another group experiment is operated with shorter optical maser wavelength.In these experiments, 532nm (green) light is used for the picopulse string.Shorter wavelength has the advantage of less diffraction limited spot size, but because substrate is absorbed on the infrared wavelength sharply to be increased, so, even may also can be difficult based on the suitable pulse characteristic of infrared test prediction of result.In these experiments, 35 picopulses of 20 nanoseconds are by being applied on the one or more target link with upper type at interval with various quantity, and just wavelength is 532nm, and motion objective table speed slowed down, and are applied on the connector with the pulse with greater number.
As the energy window of the function of the number of pulses that is applied to 1 micron pitch connector and 1.7 micron pitch connectors, respectively shown in Figure 12 a and Figure 12 b.1 micron connector spacing, the high-energy limit is damaged restriction by adjacent connector, yet 1.7 microns connector spacings, the high-energy limit is damaged restriction by substrate.Yet, in both cases, in the scope of about 200 pulses, observe the peak value of energy window in 70 pulses of about every connector.This explanation in order to obtain reliable connector fusing, needs bigger number of pulses, and for example 70 pulses or more are especially for less pitch structure and shorter optical maser wavelength.
Common conclusions
Usually, than handling pulse nanosecond, 50,70, or more the The above results under the multiple-pulse shows, when using the picopulse string, is significantly improving aspect the energy window result.For little spacing connector, the pulse of shorter wavelength and greater number is favourable.The adjacent connector that reduces damages and is even more important.Though several interaction mechanisms can take place in picosecond, the experimental result prompting is can produce less effective spot size (below diffraction limit) by " thresholding ".
For pulse and the integral pulse string energy of fixed qty N, material is removed needs higher peak pulse power usually under the pulse width that descends.Yet the peak pulse power of increase may increase the possibility that substrate damages.Therefore, may need to have more low-energy more multiple-pulse of every pulse and longer train of pulse, optimize energy window.On the other hand, if energy is too low, for example is lower than and melts threshold value, the removal of material also can not take place in longer pulse width, and perhaps the connector cutting may incomplete [10] [11].
Pulse width can be in the scope up to about 100ps, and the 10-100 psec generally is suitable.Usually, because the relation of laser instrument cost and complexity, about 1 psec or bigger pulse width grade are favourable.As noted above, for some specific connector and underlying structure, the result who has obtained with the pulse width between 30ps and the 60ps.In some embodiments, pulse width can be in about several psecs in about 50 picosecond range.Handle for picosecond, pulse power density usually can be greater than 10 9W/cm 2, and can be preferably about 10 10-10 12W/cm 2Scope in.For the processing of some connector structures, be a bit larger tham 10 with power density 9W/cm 2, high to about 10 11W/cm 2Pulse, may be optimum.
In pulse width range, obtainable maximum processing energy window will be determined by trading off between substrate damage and the infringement of adjacent connector usually.If under situation, increase peak power than short pulse width, can realize that connector is removed more completely, but the risk that exists substrate to damage.In some medium pulse widths, can realize better compromise.Can reduce substrate than long pulse width and damage, but cause not exclusively removing and residual (" splash ").Because exist adjacent connector to damage (though the damage of adjacent connector will much smaller than obtaining with nanosecond pulse), long pulse width also can reduce window.
In the visualization of amplifying, the cut point of handling with the 8ps pulse width obviously is a cut point the most completely, yet the energy level that the silicon base that window is handled in restriction is damaged generation is lower than the energy level under the situation of 35ps and 57ps pulse width.During fix N, the high-peak power of 8ps pulse causes substrate to damage.
For the laser pulse of 35ps pulsewidth, can observe cut point some splashes on every side, but these cut points are obviously more thorough than the cut point of handling with the 57ps pulse width.With the same in nanosecond laser pulses width situation, use the splash problem of picosecond laser pulse width to increase along with the increase of pulse width.
Theoretical optimum pulse width can be determined to find the maximum window of handling by analyzing failure mode altogether.For the locked mode frequency situation of N=50 and 50MHz, and use the 8ps pulse width, handle the upper bound of window and damaged restriction by silicon base.Use the 57ps pulse width, handle the upper bound of window and damaged restriction by adjacent connector.Shown in silicon base from the result of 35ps pulse width and to have damaged and the appropriateness of adjacent connector between damaging compromise, and for 1.0～2.0mm pitch structure, handling window ranges is about 57～74%, consider these two failure modes, the result that demonstration place of described relative processing window is best to most structures.This is considered to for realizing that current product is acceptable window.
According at least one embodiment of the present invention, offset on the throne moves in the time of can ignoring, and the number of pulses (N) that increases in the train of pulse is expected to improve the processing window, thereby the substrate that reduces to take place with corresponding higher peak power that reduces along with pulse width damages.Can use traffic beam reflector (for example electrical-optical modulator or acousto-optic modulator) to come compensating motion, preferably in conjunction with the laser repetition rate (up to practical limit, wherein steam/the plasma of pulse formerly/plumage brightness influences the coupling of energy to connector) that is increased.
At at least one embodiment that is used for handling very little spacing connector structure, the number of pulses that is applied to connector can surpass 50 pulses of every connector, and can be in 70 of about every connectors or more scope.Suggested as mentioned, have been found that 70-200 pulse is favourable.
In at least one embodiment, repetitive rate can be about 100MHz or higher, for example arrives 500MHz at 100MHz.Under this higher frequency, the pulse of larger amt will be passed to connector at shorter time durations.Yet, frequency should be not high to make energy to the coupling of connector owing to the steam/plasma that is discharged from/plumage brightness of following pulse is before degenerated.
In the big relatively embodiment of number of pulses, for example apply and surpass greater than a microsecond even reach under the situation in the time interval of several microseconds in pulse, objective table can surpass the acceptable standard that hot spot is placed that is used for respect to the motion of connector.In at least one embodiment, during train of pulse, may need some laser pulse deflection, with the compensation relative motion.
Here show and described various system configuration, and various system configuration can comprise visible and near ultraviolet wavelength based on laser.Than infrared laser, the short wavelength provides more effectively reducing of spot size.
Though have illustrated and described embodiment of the present invention, be not to mean these embodiment explanations and describe all possible form of the present invention.Certainly, the word that this specification uses is descriptive rather than restrictive word, and should understand under the situation of not leaving scope and spirit of the present invention and can carry out various modifications.

Claims (75)

1. method based on laser, its removal is formed on the one or more target link structures of suprabasil circuit, and do not cause described substrate, any dielectric layer between described one or more target link structures and described substrate or undesirable damage of the connector structure adjacent with described one or more target link structures, described one or more target link structures is arranged in one group of connector structure, at least some connector structures in described one group of connector structure can be separated less than the spacing of 2 μ m, and described method comprises:
Use has the seed laser of first predetermined wavelength, to produce laser pulse sequence greater than the about repetitive rate of 1MHz;
Optics amplifies at least a portion of described laser pulse sequence, with the output pulse sequence that obtains amplifying; And
During the relative motion of described substrate, with the pulse transmission of the output pulse sequence of described amplification with focus on the described one or more target link structures, all output pulses of the output pulse sequence of described in fact amplification have pulse duration less than about 100 psecs, at about at least 10 of described one or more target link structures place 9W/cm 2Arrive less than about 10 12W/cm 2The respective pulses power density of scope and about 1.2 microns or shorter wavelength, the power density of focusing pulse is low to moderate is enough to avoid described undesirable damage, the gross energy height of all described focusing pulses is to being enough to remove described one or more target link structures, simultaneously also avoid other connector structure in described one group of connector structure is caused described undesirable damage, described focusing pulse provides 30% or above relative energy processing window to about 1 micron connector spacing to about 2 micrometer ranges.
2. the method for claim 1, wherein described generation step comprised the steps: before described optics amplification procedure, with the preposition pulse energy level that is amplified to of the output of described seed laser.
3. the method for claim 1 further comprises: before described optics amplification procedure, described first predetermined wavelength is displaced to second wavelength.
4. the method for claim 1, further comprise: after described optics amplification procedure, in position-based and the velocity information at least one and controllably select at least a portion of the output pulse sequence of described amplification so that described one or more target link structures and laser beam position during described relative motion synchronously.
5. the method for claim 1, further comprise: before described optics amplification procedure, in position-based and the velocity information at least one and controllably select at least a portion of described laser pulse sequence so that described one or more target link structures and laser beam position during described relative motion synchronously.
6. the method for claim 1, wherein described generation step comprises the described seed laser of gain switch, so that pulse to be provided as required.
7. method as claimed in claim 5, wherein, the time interval between the pulse of all direct neighbors in fact of described laser pulse sequence was at least 5 nanoseconds, and the wherein said step of controllably selecting is reduced to described repetitive rate in the scope of about 20KHz to 150KHz.
8. the method for claim 1, wherein, described laser pulse sequence comprises pulse duration at least one pulse greater than about 1 nanosecond, and wherein said method further comprises: compression or described at least one pulse of cutting are to produce the pulse of pulse duration less than about 100 psecs.
9. method as claimed in claim 8, wherein, described seed laser is to be accent Q microlaser or the laser diode of an about nanosecond in the pulse duration.
10. method as claimed in claim 8, wherein, the step of described compression or cutting was performed before described optics amplification procedure.
11. the method for claim 1, wherein described seed laser is a diode pumping solid laser.
12. method as claimed in claim 11, wherein, described diode pumping solid laser is a fibre laser oscillator.
13. the method for claim 1, wherein described seed laser is active or laser with active-passive lock mould.
14. the method for claim 1, wherein described seed laser is the high-speed semiconductor laser diode.
15. the method for claim 1, wherein described optics amplification procedure is carried out by at least one fiber amplifier.
16. method as claimed in claim 15, wherein, the gain of described fiber amplifier is about 30dB.
17. the method for claim 1, wherein, the scope of described first predetermined wavelength is about 1.3 μ m to about 1.55 μ m, and described method further comprises: the optical maser wavelength of the output pulse sequence of described amplification is displaced to near-infrared wavelength or visible wavelength from described first predetermined wavelength.
18. the method for claim 1, wherein described generation step utilizes master oscillator and power amplifier (MOPA) to implement.
19. the method for claim 1, wherein, the quantity of output pulse and the speed of described relative motion cause that the displacement of described output pulse exceeds predetermined tolerance limit, and wherein said method further comprises: the described output pulse of deflection with described output pulse steering to the position that is positioned within the described predetermined tolerance limit.
20. system based on laser, it is used to remove the one or more target link structures that is formed on suprabasil circuit, and do not cause described substrate, any dielectric layer between described one or more target link structures and described substrate or undesirable damage of the connector structure adjacent with described one or more target link structures, described one or more target link structures is arranged in one group of connector structure, at least some connector structures in described one group of connector structure can be separated less than the spacing of 2 μ m, and described system comprises:
Comprise seed laser and be used for to produce the device of laser pulse sequence greater than the repetitive rate of about 1MHz, described seed laser has first predetermined wavelength;
Be used at least a portion that optics amplifies described laser pulse sequence device with the output pulse sequence that obtains amplifying; And
With the pulse transmission of the output pulse sequence of described amplification with focus on device on the described one or more target link structures, all pulses of the output pulse sequence of described in fact amplification have pulse duration less than about 100 psecs, at about at least 10 of described one or more target link structures place during described substrate is for the relative motion of connector structure 9W/cm 2Arrive less than about 10 12W/cm 2The corresponding pulse power density of scope and about 1.2 microns or shorter wavelength, the power density of focusing pulse is low to moderate is enough to avoid described undesirable damage, the gross energy height of all focusing pulses is to being enough to remove described one or more target link structures, simultaneously also avoid other connector structure in described one group of connector structure is caused described undesirable damage, described focusing pulse provides 30% or above relative energy processing window to about 1 micron connector spacing to about 2 micrometer ranges.
21. system as claimed in claim 20, wherein, the described device that is used to produce comprises master oscillator and power amplifier (MOPA).
22. system as claimed in claim 20, further comprise: at least one in position-based and the velocity information and at least a portion of output pulse sequence of controllably selecting described amplification are so that one or more target link structures and laser beam position synchronous device during described relative motion, and the wherein said device that is used for controllably selecting comprises acousto-optic modulator or electrooptic modulator.
23. the system as claimed in claim 22, the time interval between the pulse of all direct neighbors in fact of wherein said laser pulse sequence was at least 5 nanoseconds, and the wherein said device that is used for controllably selecting is reduced to described repetitive rate in the scope of about 20KHz to 150KHz.
24. the system as claimed in claim 22, wherein, described modulator is a Mach-Zehnder modulators.
25. system as claimed in claim 20, wherein, described laser pulse sequence comprises pulse duration at least one pulse greater than about 1 nanosecond, and, wherein said system further comprises compressor reducer or pulse sheer, be used for compressing respectively or described at least one nanosecond pulse of cutting, to produce the pulse of pulse duration less than about 100 psecs.
26. system as claimed in claim 25, wherein, described seed laser is to be accent Q microlaser or the laser diode of an about nanosecond in the pulse duration.
27. system as claimed in claim 25, wherein, the output of described compressor reducer or described sheer is received by the described device that is used for the optics amplification.
28. system as claimed in claim 20, wherein, described seed laser is a diode pumping solid laser.
29. system as claimed in claim 28, wherein, described diode pumping solid laser is a fibre laser oscillator.
30. system as claimed in claim 20, wherein, described seed laser is active or laser with active-passive lock mould.
31. system as claimed in claim 20, wherein, described seed laser is the high-speed semiconductor laser diode.
32. system as claimed in claim 20, wherein, the described device that is used for the optics amplification comprises at least one fiber amplifier.
33. system as claimed in claim 32, wherein, the gain of described fiber amplifier is about 30dB.
34. system as claimed in claim 20, wherein, the scope of described first predetermined wavelength is that about 1.3 μ m are to about 1.55 μ m, and described system further comprises the wavelength shift device, is used for the optical maser wavelength of the output pulse sequence of described amplification is displaced to near-infrared or visible wavelength from described first predetermined wavelength.
35. system as claimed in claim 20, wherein, the described device that is used to produce comprises master oscillator, and the described device that is used for the optics amplification comprises power amplifier (MOPA).
36. system as claimed in claim 20, wherein, the quantity of output pulse and the speed of relative motion cause that the displacement of described output pulse exceeds predetermined tolerance limit, and, wherein said system further comprises the traffic beam deflector, is used for described output pulse steering to the position that is positioned within the described tolerance limit.
37. method, it is used to remove the selected one or more target link structures that is formed on suprabasil circuit and does not cause to described substrate, in undesirable damage of described selected one or more target link structures and any dielectric layer between the described substrate or the connector structure adjacent with described selected one or more target link structures, described selected one or more target link structures is arranged in one group of connector structure, at least some connector structures in described one group of connector structure are separated less than the spacing of 2 μ m, and described method comprises:
Laser focusing output is applied to described selected one or more target link structures, during described substrate is with respect to described laser output movement, to remove described selected one or more target link structures, the output of described laser has about at least 70 pulses, and all in fact described pulses have less than the pulse width of about 100 psecs with at about at least 10 of described selected one or more target link structures place 9W/cm 2Arrive less than about 10 12W/cm 2Corresponding pulse power density and about 1.2 microns or shorter wavelength in the scope, the described power density of described pulse is low to moderate is enough to avoid described undesirable damage, the gross energy height of all described pulses is to being enough to remove described selected one or more target link structures, simultaneously also avoid other connector structure in described one group of connector structure is caused described undesirable damage, described laser output provides 30% or above relative energy processing window to about 1 micron connector spacing to about 2 micrometer ranges.
38. method as claimed in claim 37, wherein, the described step that applies is to utilize wavelength to be used for described wavelength-shift to the wavelength shift device of near-infrared or visible wavelength of described diode is implemented to the semiconductor laser diode of about 1.55 mu m ranges, at least one fiber amplifier and at least one at about 1.0 μ m.
39. method as claimed in claim 38, wherein, the wavelength of described laser diode is about 1.55 μ m, and described shifter is a frequency multiplier, and the wavelength after the displacement is about 0.75 μ m.
40. method as claimed in claim 38, wherein, described shifter is a triductor, and the wavelength after the displacement is a visible wavelength.
41. method as claimed in claim 37, wherein, the pulse width of all in fact described pulses is corresponding to such duration, the energy density threshold that wherein is used to remove selected one or more target link structures is proportional with the square root of pulse width in fact, thereby described selected one or more target link structures is removed in the calorifics mode.
42. method as claimed in claim 37, wherein, the passivation layer that described selected one or more target link structures is covered on one or more covers, the power density of wherein one or more pulses produces thermal shock to the described passivation layer that covers on one or more, and remove described passivation layer and the described selected one or more target link structures that covers on one or more, the removal of described passivation layer that covers on one or more and described selected one or more target link structures produces owing to thermal and mechanical stress and the effect of melting the two.
43. method as claimed in claim 42, wherein, the described passivation layer that covers on one or more is an inorganic passivation layer, and the ABSORPTION EDGE of described inorganic passivation layer is in the scope of ultraviolet wavelength, and wherein said pulse power density is less than about 10 12W/cm 2
44. method as claimed in claim 37, wherein, the scope of the pulse width of at least one pulse in the described pulse is that about 30 psecs are to about 60 psecs.
45. method as claimed in claim 37, wherein, the size of described laser focusing output is less than about 1.5 microns.
46. method as claimed in claim 37, wherein, laser focusing output comprises that at least one focuses on the pulse of non-circular hot spot, to improve the described laser focusing output energy envelope in described selected one or more target link structures.
47. method as claimed in claim 37, wherein, the speed of number of pulses and described motion causes that the displacement of described laser output exceeds predetermined tolerance limit, and wherein said method further comprises: the described pulse of deflection with described pulse steering to the position that is positioned within the described tolerance limit.
48. method as claimed in claim 47, wherein, the step of described deflection utilizes acousto-optic device or electro-optical device to implement.
49. method as claimed in claim 37 further comprises:
Space segmentation is carried out at least one pulse to described laser output, to form the pulse of one group of space segmentation; And
With at least one pulse choice in the pulse of described space segmentation guide to described selected one or more target link structures, or guide to the second selected one or more target link structures, or guide to this two selected one or more target link structures.
50. method as claimed in claim 37, wherein, the described step that applies utilizes a plurality of lasing light emitters to implement, and wherein said method further comprises: the output optics of described lasing light emitter is combined in the common optical path.
51. method as claimed in claim 50, wherein, described lasing light emitter is dissimilar, and in the described lasing light emitter at least one comprises semiconductor laser diode.
52. method as claimed in claim 37, wherein, number of pulses is about 70-200.
53. method as claimed in claim 37, wherein, the energy of at least one in the described pulse is about 5nJ or following.
54. method as claimed in claim 37, wherein, the energy of all in fact described pulses be about 1nJ or more than.
55. method as claimed in claim 37, wherein, described laser focusing output produces size in about 0.1 micron heat affected area to about 0.85 micrometer range.
56. method as claimed in claim 37, wherein, the size of described laser focusing output is less than about 1.0 microns.
57. method as claimed in claim 37, wherein, the pulse of at least two direct neighbors of described laser output has the time interval that scope is about 2 nanoseconds to about 10 nanoseconds, thereby corresponding to the effective repetitive rate of scope at the extremely about 500MHz of about 100MHz, and, the described time interval surpasses the time interval of the steam/plasma plume brightness that is used to dissipate, and described steam/plasma plume brightness is produced by last laser pulse and described selected one or more target link structures and the connector structural interaction adjacent with described selected one or more target link structures.
58. method as claimed in claim 57, wherein, in fact the time interval between the pulse of all direct neighbors be about 5 nanoseconds or more than.
59. method as claimed in claim 37, wherein, the scope of described pulse power density is about 10 9To about 10 11W/cm 2, and wherein the pulse width range of at least one pulse is that several psecs are extremely less than about 50 psecs.
60. method, it is used to remove the one or more target link structures that is formed on suprabasil circuit, and do not cause that described method comprises to described substrate, any dielectric layer between described one or more target link structures and described substrate or undesirable damage of the connector structure adjacent with described one or more target link structures:
Laser focusing output is applied to described one or more target link structures, during described substrate is with respect to described laser output movement, to remove described one or more target link structures, described laser output has about 70 to 200 pulses, and all in fact described pulses have less than the pulse width of about 100 psecs with at about at least 10 of described one or more target link structures place 10W/cm 2Arrive less than about 10 12W/cm 2The corresponding pulse power density of scope and 1 micron or shorter wavelength, described pulse to about 1 micron connector spacing to about 2 micrometer ranges provide 30% or above relative energy handle window.
61. method as claimed in claim 60, wherein, described wavelength is less than about 800nm, and the pulse width of one of wherein said pulse is between about 30 psecs and about 60 psecs.
62. method as claimed in claim 60, wherein, the described step that applies is that to utilize wave-length coverage be about 1.0 μ m and is used for described wavelength-shift to the wavelength shift device less than 1 micron of described diode is implemented to the semiconductor laser diode of about 1.55 μ m, at least one fiber amplifier and at least one.
63. method as claimed in claim 62, wherein, the described wavelength of described laser diode is about 1.55 μ m, and described shifter is a frequency multiplier, and the wavelength after being shifted is about 0.75 micron.
64. method as claimed in claim 62, wherein, described shifter is a triductor, and the wavelength after being shifted is a visible wavelength.
65. method as claimed in claim 60, wherein, the scope of described pulse power density is about 10 9To about 10 11W/cm 2, and the pulse width range of at least one pulse in the wherein said pulse is that several psecs are extremely less than about 50 psecs.
66. method as claimed in claim 60, wherein, the speed of number of pulses and described motion causes that the displacement of described laser output exceeds predetermined tolerance limit, and wherein said method further comprises: the described pulse of deflection with described pulse steering to the position that is positioned within the described tolerance limit.
67. method as claimed in claim 60, wherein, the step of described deflection utilizes acousto-optic device or electro-optical device to implement.
68. system, it is used to remove the one or more target link structures that is formed on suprabasil circuit, and do not cause described substrate, any dielectric layer between described one or more target link structures and described substrate or undesirable damage of the connector structure adjacent with described one or more target link structures, described one or more target link structures is positioned at one group of connector structure, at least some connector structures in described one group of connector structure are separated by the interval less than the center to center of 2 μ m, and described system comprises:
The device that comprises laser subsystem and optical subsystem, described device is used for during the motion that described substrate is exported with respect to laser laser focusing output being applied on the described one or more target link structures to remove described one or more target link structures, described laser output has at least 70 pulses, and all in fact described pulses have less than the pulse width of about 100 psecs with at about at least 10 of described one or more target link structures place 9W/cm 2Arrive less than about 10 12W/cm 2The corresponding pulse power density of scope and about 1.2 microns or shorter wavelength, the power density of described pulse is low to moderate is enough to avoid described undesirable damage, the gross energy height of all described pulses is to being enough to remove described selected one or more target link structures, simultaneously also avoid other connector structure in described one group of connector structure is caused described undesirable damage, described pulse provides 30% or above relative energy processing window to about 1 micron connector spacing to about 2 micrometer ranges; And
Positioning subsystem, it is used for described laser focusing output is navigated to described one or more target link structures.
69. as the described system of claim 68, wherein, described wavelength is less than about 800nm.
70. as the described system of claim 68, wherein, described laser subsystem comprises that wave-length coverage is about 1.0 μ m and is used for described wavelength-shift with described diode to the wavelength shift device less than 1.2 microns to the semiconductor laser diode of about 1.55 μ m, at least one fiber amplifier and at least one.
71. as the described system of claim 70, wherein, described shifter is a frequency multiplier, and the wavelength after the displacement is about 0.75 micron.
72. as the described system of claim 70, wherein, described shifter is a triductor, and the wavelength after the displacement is a visible wavelength.
73. as the described system of claim 68, wherein, the scope of described pulse power density is about 10 9To about 10 11W/cm 2, and the pulse width range of at least one pulse in the wherein said pulse is that several psecs are extremely less than about 50 psecs.
74. as the described system of claim 68, wherein, the speed of number of pulses and described motion causes that the displacement of described laser output exceeds predetermined tolerance limit, and, wherein said system further comprises the traffic beam deflector, with described pulse steering to the position that is positioned within the described tolerance limit.
75. as the described system of claim 74, wherein, described deflector is acousto-optic device or electro-optical device.
CNA2007800112965A 2006-02-03 2007-02-05 Laser-based method and system for removing one or more target link structures Pending CN101410219A (en)

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