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WO2019138404A1 - Impression directe de résistances intégrées - Google Patents

Impression directe de résistances intégrées Download PDF

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Publication number
WO2019138404A1
WO2019138404A1 PCT/IL2019/050037 IL2019050037W WO2019138404A1 WO 2019138404 A1 WO2019138404 A1 WO 2019138404A1 IL 2019050037 W IL2019050037 W IL 2019050037W WO 2019138404 A1 WO2019138404 A1 WO 2019138404A1
Authority
WO
WIPO (PCT)
Prior art keywords
pulses
substrate
circuit
droplets
donor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IL2019/050037
Other languages
English (en)
Inventor
Hanina Golan
Dmitri Burshtyn
Gil Tidhar
Gideon Fostick
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Orbotech Ltd
Original Assignee
Orbotech Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Orbotech Ltd filed Critical Orbotech Ltd
Priority to CN201980005680.7A priority Critical patent/CN111684550A/zh
Publication of WO2019138404A1 publication Critical patent/WO2019138404A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/22—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming
    • H01C17/24—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming by removing or adding resistive material
    • H01C17/242—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming by removing or adding resistive material by laser
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/22—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming
    • H01C17/26—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming by converting resistive material
    • H01C17/265—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming by converting resistive material by chemical or thermal treatment, e.g. oxydation, reduction, annealing
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/16—Printed circuits incorporating printed electric components, e.g. printed resistor, capacitor, inductor
    • H05K1/167—Printed circuits incorporating printed electric components, e.g. printed resistor, capacitor, inductor incorporating printed resistors
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/101—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern by casting or moulding of conductive material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/107—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern by filling grooves in the support with conductive material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/12—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
    • H05K3/1283—After-treatment of the printed patterns, e.g. sintering or curing methods
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/22—Secondary treatment of printed circuits
    • H05K3/26—Cleaning or polishing of the conductive pattern
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/22—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming
    • H01C17/26—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming by converting resistive material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/09—Shape and layout
    • H05K2201/09209—Shape and layout details of conductors
    • H05K2201/09218—Conductive traces
    • H05K2201/09263—Meander
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/10—Using electric, magnetic and electromagnetic fields; Using laser light
    • H05K2203/107—Using laser light
    • H05K2203/108—Using a plurality of lasers or laser light with a plurality of wavelengths
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/11—Treatments characterised by their effect, e.g. heating, cooling, roughening
    • H05K2203/1194—Thermal treatment leading to a different chemical state of a material, e.g. annealing for stress-relief, aging
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/12—Using specific substances
    • H05K2203/128—Molten metals, e.g. casting thereof, or melting by heating and excluding molten solder
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/13—Moulding and encapsulation; Deposition techniques; Protective layers
    • H05K2203/1333—Deposition techniques, e.g. coating
    • H05K2203/1344—Spraying small metal particles or droplets of molten metal
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/0011—Working of insulating substrates or insulating layers
    • H05K3/0017—Etching of the substrate by chemical or physical means
    • H05K3/0026—Etching of the substrate by chemical or physical means by laser ablation

Definitions

  • the present invention relates generally to laser- induced material transfer, and particularly to printing electronic components on a substrate by laser-induced forward transfer (LIFT) .
  • LIFT laser-induced forward transfer
  • LDW laser direct-write
  • LIFT Laser-induced forward transfer
  • laser photons provide the driving force to catapult a small volume of material from a donor film toward an acceptor substrate.
  • the laser beam interacts with the inner side of the donor film, which is coated onto a non-absorbing carrier substrate.
  • the incident laser beam in other words, propagates through the transparent carrier before the photons are absorbed by the inner surface of the film.
  • material is ejected from the donor film toward the surface of the substrate, which is generally placed, in LIFT systems that are known in the art, either in close proximity to or even in contact with the donor film.
  • the applied laser energy can be varied in order to control the thrust of forward propulsion that is generated within the irradiated film volume.
  • PCT International Publication WO 2010/100635 whose disclosure is incorporated herein by reference, describes a system and method of repairing electrical circuits in which a laser is used to pre-treat a conductor repair area of a conductor formed on a circuit substrate.
  • the laser beam is applied to a donor substrate in a manner that causes a portion of the donor substrate to be detached therefrom and to be transferred to a predetermined conductor location.
  • PCT International Publication WO 2015/181810 whose disclosure is incorporated herein by reference, describes a method for material deposition, which includes defining a locus and an electrical resistance of an embedded resistor to be formed on a printed circuit substrate and to contact conductive traces on the printed circuit substrate.
  • a transparent donor substrate having opposing first and second surfaces and a donor film including a metal formed over the second surface, is positioned in proximity to the printed circuit substrate, with the second surface facing toward the printed circuit substrate.
  • Pulses of laser radiation are directed to pass through the first surface of the donor substrate and impinge on the donor film so as to induce ejection from the donor film of droplets of molten material, which form particles of the metal on the printed circuit substrate, while scanning the pulses so as to fill the locus with an aggregation of the particles that provides the defined resistance between the conductive traces that are in contact with the aggregation.
  • Embodiments of the present invention that are described hereinbelow provide novel methods and systems for LIFT-based fabrication of circuit components on a substrate, as well as circuit components produced by such methods .
  • a method for fabrication of an electrical device includes identifying a locus on a circuit substrate on which a resistor having a specified resistance is to be formed between first and second endpoints of the locus.
  • a transparent donor substrate having opposing first and second surfaces and a donor film including a resistive material formed over the second surface, is positioned in proximity to the identified locus on the circuit substrate, with the second surface facing toward the circuit substrate.
  • Pulses of laser radiation are directed to pass through the first surface of the donor substrate and impinge on the donor film so as to induce ejection of droplets of the resistive material from the donor film onto the circuit substrate at respective, neighboring locations along the locus with a separation between the neighboring locations selected so as to form a circuit trace having the specified resistance between the first and second endpoints.
  • the separation is selected so as to control a size of an area of contact between the droplets at the neighboring locations, which determines the resistance of the circuit trace.
  • directing the pulses includes adjusting an energy level of the pulses so as to control one or more physical properties of the droplets, which determine the resistance of the circuit trace.
  • identifying the locus includes identifying a gap between conductors on the circuit substrate, and directing the pulses of the laser radiation includes forming the circuit trace within the gap.
  • identifying the gap includes making a measurement of the gap, and forming the circuit trace responsively to the measurement.
  • forming the trace includes setting the separation between the neighboring locations onto which the droplets are ejected responsively to the measurement so that the circuit trace will have the specified resistance.
  • forming the circuit trace includes adjusting and one or more physical properties of the droplets by setting an energy of the pulses responsively to the measurement so that the circuit trace will have the specified resistance.
  • Making the measurement can include capturing and processing an image of the circuit substrate in order to identify and measure the gap.
  • the method includes, before the ejection of the droplets, forming a trench along the locus in the circuit substrate, wherein directing the pulses of the laser radiation includes injecting the droplets into the trench.
  • the trench has a width that is less than an average diameter of the droplets.
  • the method includes annealing the circuit trace.
  • directing the pulses includes setting an energy and focal size of the pulses of the laser radiation that impinge on the donor film so that each pulse induces the ejection of a single droplet of the resistive material from the donor film.
  • the energy of the pulses is set to a first value in order to induce the ejection of the single droplet per pulse
  • the method includes, after forming the circuit trace, directing further pulses of the laser radiation at a second energy value, greater than the first value, to impinge on the donor film so as to cause a spray of small particles of the resistive material to be ejected from the donor film and overlay an end of the circuit trace.
  • directing the pulses includes directing multiple pulses of the laser radiation to impinge simultaneously at different, respective points on the donor film so as to fabricate multiple resistive circuit traces on the circuit substrate concurrently. Additionally or alternatively, directing the pulses includes scanning the pulses so as to form the circuit trace in a meander pattern between the first and second endpoints .
  • directing the pulses includes scanning the pulses over the donor substrate using an acousto-optic deflector, measuring an intensity of the pulses, and controlling the acousto-optic deflector responsively to the measured intensity so as to compensate for fluctuations in an energy of the pulses that impinge on the donor
  • a system for fabrication of an electrical device includes a transparent donor substrate, having opposing first and second surfaces and a donor film including a resistive material formed over the second surface.
  • a positioning assembly is configured to position the donor substrate in proximity to a locus on a circuit substrate on which a resistor having a specified resistance is to be formed between first and second endpoints of the locus, with the second surface of the donor substrate facing toward the circuit substrate.
  • An optical assembly is configured to direct pulses of laser radiation to pass through the first surface of the donor substrate and impinge on the donor film so as to induce ejection of droplets of the resistive material from the donor film onto the circuit substrate at respective, neighboring locations along the locus with a separation between the neighboring locations selected so as to form a circuit trace having the specified resistance between the first and second endpoints.
  • Fig. 1 is schematic side view of a system for fabrication of embedded resistors, in accordance with an embodiment of the invention
  • Fig. 2 is a schematic sectional view of a locus for deposition of an embedded resistor on an acceptor substrate, showing LIFT-driven ejection of a metal droplet from a donor film toward the site in accordance with an embodiment of the present invention
  • Fig. 3A is a schematic, pictorial illustration of an optical assembly used in a system for fabrication of embedded resistors, in accordance with an embodiment of the present invention
  • Fig. 3B is a schematic view of an optical assembly used in a system for fabrication of embedded resistors, in accordance with another embodiment of the present invention.
  • Fig. 4 is a flow chart that schematically illustrates a method for fabrication of embedded resistors, in accordance with an embodiment of the invention
  • Fig. 5 is a schematic top view of a circuit substrate showing circuit traces and embedded resistors formed on the substrate, in accordance with an embodiment of the invention
  • Fig. 6A is a schematic detail view of a connection between a circuit trace and an embedded resistor, in accordance with an embodiment of the invention.
  • Fig. 6B is a schematic, sectional view of the circuit trace and embedded resistor shown in Fig. 6A, taken along the line B-B in Fig. 6A, in accordance with an embodiment of the invention;
  • Fig. 6C is a schematic, sectional view of the circuit trace and embedded resistor shown in Fig. 6A, taken along the line C-C in Fig. 6A, in accordance with an alternative embodiment of the invention.
  • Fig. 6D is a schematic, sectional view of the circuit trace and embedded resistor shown in Fig. 6A, taken along the line D-D in Fig. 6A, in accordance with an embodiment of the invention.
  • Embodiments of the present invention that are described herein provide methods and systems for LIFT printing of resistors of small size and fine precision.
  • the disclosed methods are capable of fabricating embedded resistors on circuit substrates at higher density than techniques that are known in the art, while maintaining accuracy that is sufficient for most commercial applications .
  • an embedded resistor having a specified resistance, is fabricated in a certain locus on a circuit substrate between a pair of endpoints, such as a pair of conductive terminals, on the substrate.
  • a transparent donor substrate having a donor film comprising a resistive material formed over one of its surfaces, is positioned in proximity to the locus where the resistor is to be printed on the circuit substrate, with the donor film facing toward the circuit substrate.
  • a laser directs pulses of radiation to pass through the donor substrate and impinge on the donor film so as to induce ejection of droplets of the resistive material from the donor film onto the circuit substrate.
  • the laser beam and substrate position are controlled so that the droplets are deposited in succession at respective, neighboring locations along the locus .
  • the resistance of the embedded resistor is controlled by setting the separation between the droplet locations to a selected value.
  • the resistivity of the trace formed by the droplets increases with increasing separation between the droplet locations. More specifically, the separation is selected so as to control the size of the area of contact between neighboring droplets, which in turn determines the resistivity of the circuit trace.
  • a trench is formed along the locus of the resistor in the circuit substrate before ejection of the droplets, and the pulses of laser radiation cause the droplets to be injected into the trench.
  • the inventors have found that using such a trench, which may have a width that is less than an average diameter of the droplets, in useful in precisely controlling the width and resistivity of the resistive trace.
  • the resistive trace may be annealed (for example, by thermal treatment using a laser beam) after LIFT printing in order to trim and/or stabilize the resistance to the desired value.
  • Fig. 1 is a schematic side view of a system 20 for LIFT-based material deposition of an embedded resistor on an acceptor substrate 22, in accordance with an embodiment of the present invention.
  • System 20 comprises an optical assembly 24, in which a laser 26 emits pulsed radiation, which is focused by suitable optics 30 onto a LIFT donor sheet 32.
  • a scanner 28 such as a rotating mirror and/or an acousto-optic beam deflector under control of a control unit 40, scans the laser beam so as to irradiate different spots on donor sheet 32.
  • Control unit 40 thus controls optical assembly 24 so as to write the donor material over a predefined locus on substrate 22, with spacing between neighboring droplets controlled in accordance with the desired resistance.
  • the locus where the resistor is to be deposited comprises a trench 46 in substrate 22, which is formed in a gap within a conductive trace 44 on substrate 22.
  • Laser 26 may comprise, for example, a pulsed Nd:YAG laser with frequency-doubled output, which permits the pulse amplitude to be controlled conveniently by control unit 40.
  • the pulse duration is in the range of 0.1 ns to 1 ns, with pulse energy in the range of 0.5 to 40 pj.
  • Optics 30 are similarly controllable in order to adjust the size of the focal spot formed by the laser beam on donor sheet 32, with spot sizes in the range between 5 and 500 pm.
  • the above laser pulse characteristics are presented by way of example, and other types of lasers, with different pulse energies and spot sizes, may alternatively be used depending on application requirements.
  • Substrate 22 typically comprises a dielectric material on which a conductive structure is printed, such as a printed electrical circuit, including trace 44.
  • Substrate 22 may be either rigid or flexible.
  • substrate 22 may comprise a laminated epoxy or ceramic sheet, for example, or a flexible circuit substrate, as are known in the art.
  • system 20 may be used to print embedded resistors on substrates of other sorts, such as glass, thermoplastics, thermoset materials, and other polymer and organic materials, and even paper-based materials.
  • Donor sheet 32 comprises a donor substrate 34 with a donor film 36 formed on the surface that faces toward acceptor substrate 22.
  • Donor substrate 34 comprises a transparent optical material, such as a glass or plastic sheet
  • donor film 36 comprises a suitable resistive material, such as a Ni x Cri- x alloy, with x in the range of 0.3 to 0.7, for example.
  • the thickness of donor film 36 is between 0.1 pm and 3 pm.
  • other resistive compounds can be used in donor film 36, for example, CrSiN, CrSi, AIO2, or NiCrAl .
  • other suitable compounds that may be used in LIFT-based fabrication of embedded resistors will be apparent to those skilled in the art after reading the present description and are considered to be within the scope of the present invention.
  • Control unit 40 causes a motion assembly 38 to shift either acceptor substrate 22 or optical assembly 24, or both, in order to align the beam from laser 26 with the locus on the acceptor substrate onto which the material from donor film 36 is to be written.
  • Donor sheet 32 is positioned above the locus in proximity to acceptor substrate 22, at a desired gap width from the acceptor substrate. Typically, this gap width is at least 0.1 mm, or possibly greater, subject to proper selection of the laser beam parameters.
  • Optics 30 focus the laser beam to pass through the outer surface of donor substrate 34 and to impinge on donor film 36, thereby causing droplets of molten metal to be ejected from the film, across the gap and onto acceptor substrate 22. This LIFT process is described in greater detail hereinbelow with reference to Fig. 2.
  • system 20 in this embodiment comprises a camera 42, which captures an electronic image of substrate 22, including trace 44, in registration with optical assembly 24.
  • camera 42 comprises a high-resolution image sensor with high- magnification optics, in order to enable control unit 40 to accurately measure the length of the gap in trace 44 into which the resistor is to be deposited.
  • control unit 40 can use a priori information, such as computer-aided manufacturing (CAM) data, in determining the length of the gap.
  • Control unit 40 uses the actual and/or a priori gap dimensions in adjusting the resistor deposition parameters, such as the spacing between neighboring droplets, so as to ensure that the embedded resistor will have the desired resistance. These adjustments are described further hereinbelow.
  • control unit 40 comprises a general-purpose computer, with suitable interfaces for controlling and receiving feedback from optical assembly 24, motion assembly 38, and other elements of system 20.
  • System 20 may comprise additional elements (omitted from the figures for the sake of simplicity) , such as an operator terminal, which can be used by an operator to set the functions of the system, and other pre-processing and post-processing stations. These and other ancillary elements of system 20 will be apparent to those skilled in the art and are omitted from the present description for the sake of simplicity.
  • Some of the pre- and post-processing steps involved in producing embedded resistors are described below. A number of these steps involve application of laser radiation to substrate 22 and/or to structures formed on the substrate. These steps may be performed by laser 26 and optical assembly 24, with operational parameters different from those used in the LIFT deposition process, or they may alternatively be carried out in other laser- based processing stations, which are omitted from the figures for the sake of simplicity.
  • Fig. 2 is a schematic sectional view of a locus at which an embedded resistor is deposited on substrate 22, showing LIFT-driven ejection of a metal droplet 54 from donor film 36 into trench 46, in accordance with an embodiment of the present invention.
  • This figure illustrates the effect of irradiating film 36 with a pulsed laser beam 50, with pulse duration comparable to the time required for heat diffusion through the film, as described in the above-mentioned PCT publications.
  • This choice of laser pulse parameters gives rise to a "volcano" pattern 52 in the donor film.
  • Each laser pulse in this "volcano- jetting" regime causes a single droplet 54 to be emitted with high directionality, typically within about 5 mrad of the normal to the film surface.
  • the sizes of the droplets can be controlled by adjusting the energy, pulse duration, and focal spot size of laser beam 50 on donor film 36, as well as the thickness of the donor film.
  • the volume of droplet 54 can typically be adjusted within the range of 10 to 100 femtoliter .
  • the laser pulse energy and other operating parameters may be adjusted so that each laser pulse causes multiple droplets to be ejected from donor film 36, possibly operating in the "spray regime" that is defined below.
  • LIFT-driven ejection of droplets takes place when the laser fluence exceeds a given threshold, which depends on the donor film thickness, the donor material, the laser pulse duration, and other factors.
  • a given threshold which depends on the donor film thickness, the donor material, the laser pulse duration, and other factors.
  • "volcano-j etting" ejection will occur over a range of laser fluence values extending from the LIFT threshold up to an upper limit, which is typically about 50% greater than the threshold fluence. Above this upper fluence limit, each laser pulse will tend to induce ejection of many small droplets from the donor film, with nanoscale droplet dimensions.
  • This latter, high-fluence regime is referred to herein as the "spray regime" and can be useful in producing a protective coating over parts of the embedded resistor, as described further hereinbelow.
  • Droplets 54 traverse the gap between donor film 36 and substrate 22, and then solidify rapidly as metal particles 56 on the surface of the substrate.
  • the diameters of particles 56 depend on the sizes of droplets 54 that produced them, as well as on the size of the gap traversed by the particles between film 36 and substrate 22.
  • particles 46 have diameters in the range of 5-10 pm, and the diameter can be reduced to less than 2 pm by appropriate setting of the LIFT parameters described above.
  • Scanner 28 in optical assembly 24 (Fig. 1) precisely sets the spacing d that separates the locations of neighboring particles 56, under the control of control unit 40. This spacing is selected so as to control the size of the area of contact between the neighboring particles, which determines the resistivity of the circuit trace formed by the particles. (Larger spacing means smaller area of contact, which translates into greater resistivity, and vice versa.) The resistance of the trace is thus determined by the particle spacing, together with the length and width of the trace.
  • control unit 40 can be calibrated to set the spacing d along with the irradiation parameters of optical assembly 24, such as the energy and duration of the laser pulses and the gap between donor film 36 and acceptor substrate 22, so as to achieve a desired resistivity.
  • the resistivity can be expressed in terms of a "bulk factor, " meaning the ratio between the resistivity of the trace formed by particles 56 and the bulk resistivity of the material making up film 36.
  • the inventors have found that the relation between the spacing d and the bulk factor for a given donor film and irradiation parameters is consistent and repeatable, and thus can be calibrated experimentally and used in recipes for deposition of embedded resistors. Specifically, in the configuration of system 20 that is illustrated in Figs.
  • the inventors were able to achieve bulk factors in the range of 3-30. For example, in printing a line of NiCr with a width of two droplets and spacing d chosen to give 50% overlap between neighboring particles 56, the inventors repeatedly achieved a bulk factor of 10.
  • Fig. 3A is a schematic, pictorial illustration showing details of optical assembly 24, in accordance with an embodiment of the present invention.
  • Scanner 28 in this embodiment creates multiple beams 50 simultaneously. These beams can be used to produce multiple embedded resistors concurrently, and thus increase the throughput of system 20. (Alternatively, only a single laser beam can be used, as illustrated in Fig. 1, possibly with a dual-axis scanning mirror.)
  • Laser 26 emits a single, pulsed beam of optical radiation, which may comprise visible, ultraviolet or infrared radiation.
  • a deflector 60 such as an acousto optic deflector (AOD) , splits the input beam into multiple output beams.
  • AOD acousto optic deflector
  • Such an AOD may comprise, for example, a piezoelectric crystal 62, which is driven by a multi frequency drive signal in order to generate acoustic waves in the deflector that split the input beam.
  • At least one scanning mirror 64 scans the beams over donor sheet 32 via optics 30. Although only a single mirror 64 is shown in Fig.
  • alternative embodiments may employ dual-axis mirrors, which may be scanned together or independently, and/or any other suitable types of single- or dual-axis deflectors and scanners that are known in the art, such as a fast steering mirror, galvo-scanner, piezoelectric, or MEMS device.
  • Acousto-optic deflector 60 may be driven in various different modes in order to generate and steer the multiple output beams.
  • a number of suitable drive techniques, along with ancillary focusing and scanning optics, that may be adapted for use in optical assembly 24 are described, for example, in U.S. Patent 8,395,083, whose disclosure is incorporated herein by reference.
  • a multi-frequency drive signal causes the acousto-optic deflector to diffract the input beam into multiple output beams at different, respective angles. Further details of this sort of scheme are described in PCT International Publication WO 2016/020817, whose disclosure is incorporated herein by reference.
  • Fig. 3B is a schematic side view showing details of optical assembly 24, in accordance with another embodiment of the present invention. The features of this embodiment can be usefully combined with those of the embodiment of Fig. 3A in order to more precisely control the optical assembly generally and an acousto-optic modulator (AOM) 61 in particular.
  • AOM acousto-optic modulator
  • a beamsplitter 66 picks off a small portion of the beam from laser 26 following AOM 61, while most of the beam energy reaches a scanner 69 (which can be the same as shown Fig 3A or of any other suitable type that is known in the art, such as the types mentioned above.) Scanner 69 scans the laser beam or beams over donor sheet 32 via optics 30.
  • a power sensor 68 receives the portion of the beam picked off by beamsplitter 66 and measures the intensity of each laser pulse. Power sensor 68 feeds the measurements in real time to control unit 40, which uses the measured information in compensating for fluctuations in the energy of the laser pulses. Based on the measurements, control unit 40 assesses the actual energy of the laser pulses, and modifies the energy of subsequent pulses so that a series of consecutive pulses attains the average value that is necessary to achieve the target resistance (or more specifically, resistance per unit length) . In the pictured example, control unit 40 increases or decreases the energy of the next laser pulse by setting the attenuation level of AOM 61 so that the level of laser power that reaches donor sheet 32 is controlled as desired. Alternatively, control unit 40 may control AOD 60 (Fig. 3A) and/or may directly control laser 26 in order to maintain the desired power level.
  • Control unit 40 can set the laser power as needed in order to compensate for changes in the size of the gap into which the resistor is to be printed. For example, control unit 40 may adjust the energy level of the pulses so as to control physical properties of the droplets, which determine the resistance of the resulting circuit trace.
  • the physical properties that can be controlled in this manner include particularly the droplet volume, as well as the density, porosity, and quality of adhesion between the droplets .
  • Fig. 4 is a flow chart that schematically illustrates a method for fabrication of embedded resistors, in accordance with an embodiment of the invention. The method is described, for the sake of convenience and clarity, with reference to the elements of system 20 that are shown in the preceding figures. Alternatively, however, the principles of this method may be applied in other sorts of suitably-configured LIFT systems, as will be apparent to those skilled in the art after reading the present description. Although the steps of the method are presented here serially, the method may be parallelized (using multiple beams, as shown in Fig. 3, for example) and/or pipelined, in order to produce multiple embedded resistors concurrently with high throughput.
  • an operator of system 20 pre calibrates the volume resistivity of the LIFT deposition process, at a pre-calibration step 70.
  • This step can include, for example, measurement of the sheet resistivity of donor film 36 (possibly including compensation for donor structure non-uniformities) and sample printing of resistors followed by in-situ measurement of the resulting resistance.
  • correction factors for the actual printing steps are computed and loaded into control unit 40.
  • the correction factors are a part of the printing recipe, which includes control of droplet overlaps, laser energy used in the process, and post-processing steps such as laser annealing.
  • control unit 40 inspects the gap in trace 44 in which a resistor is to be deposited and calculates the deposition parameters to be applied in forming the resistor, at an inspection step 72.
  • control unit 40 measures the actual gap dimensions in trace 44, and modifies the geometry and recipe for printing the resistor to compensate for any variations in the gap length relative to the original design, as reflected in the CAM data, for example.
  • control unit 40 computes a length correction factor, which it then applies in the printing recipe to control factors such as the droplet spacing, laser energy used in the LIFT process, and post-process steps such as laser annealing, in order to ensure that the embedded resistor will meet the applicable specifications.
  • the surface of substrate 22 is prepared for LIFT deposition, at a surface preparation step 74.
  • System 20 may apply laser ablation at this step in order to clean the surface of the gap in trace 44 where the resistor is to be formed, as well as possibly excavating trench 46 to contain the resistor.
  • This step may use the same laser beam as in the subsequent LIFT printing step, or a different laser, or possibly different beams of the same laser.
  • the creation of a narrow trench 46 at this step is useful in enhancing capture and adhesion of droplets 54 to substrate 22 and enables reliable creation of resistive traces whose width is no more than a single particle 56.
  • narrow trenches may be used to confine the spread of droplets 54 and thus create resistors of dimensions comparable to or even smaller than traces 44.
  • the inventors have applied LIFT deposition to produce resistors in trenches of width less than 10 pm and depth less than 12.5 pm.
  • laser 26 or other means may be applied to prepare conductive traces 44 on substrate 22 for connection of the ends of the resistor to the traces.
  • the edge of the trace adjoining the locus of the resistor may be cleaned and straightened.
  • port holes may be excavated within the edges of traces 44, to be filled with droplets 54 of the resistor material (as illustrated in Fig. 6C, for example) .
  • control unit 40 After preparation of the substrate, laser 26 and scanner 28 are operated to produce a resistive trace within the gap, at a LIFT deposition step 76.
  • control unit 40 typically adjusts optical assembly 24 to operate in the single-drop "volcano-j etting" regime while printing the resistive trace.
  • control unit 40 sets the spacing between neighboring droplets 54 in accordance with the applicable recipe, while adjusting for the material and trace gap parameters that were found at steps 72 and 74.
  • control unit 40 may modify the LIFT parameters of optical assembly 24 to operate in the spray regime, in order to overlay the ends of the resistive trace in the port holes of conductive trace 44 with a protective layer of closely- bonded small droplets.
  • This layer is useful in sealing the ends of the trace and thus protecting against subsequent degradation of the bond between particles 56 and trace 40. Such degradation might otherwise occur, for example, due to penetration of wet chemicals that are used in cleaning of substrate 22 after resistor deposition.
  • control unit 40 may probe substrate 22 in order to measure the resistance following step 76, and then anneal the resistive trace accordingly to reduce the resistance to the target value.
  • an image of the resistive trace may be captured, using ultraviolet illumination, for example, and then analyzed to measure slight variations in dimensions. These slight variations can be correlated with small variations in resistance, and the annealing applied at step 78 can be used to compensate for these variations and thus improve resistor accuracy.
  • other measurement techniques can be applied at this stage, for example measurement of density using X- rays or eddy current sensing.
  • annealing may be applied as a part of the fabrication recipe, possibly to adjust for the length of the gap that was measured at step 72.
  • the area of the resistive trace on substrate 22 is cleaned, at a cleaning step 80.
  • This step may again use laser 26 or another laser source to ablate resistive material from the edges of the resistive trace in order to remove any material deviating from the target width and shape of the trace. Additionally or alternatively, other sorts of cleaning may be applied, such as chemical cleaning, to remove waste material.
  • control unit 40 again operates camera 42 to capture an image of the embedded resistor, at a final inspection step 82.
  • Control unit 40 processes the image in order to identify any quality control defects, as well as to adjust the parameters of system 20 that will be applied in subsequent iterations through the above process.
  • Fig. 5 is a schematic top view of circuit substrate 22, showing a pattern 90 of circuit traces 44 and embedded resistors 98, 100, 102 formed on the substrate, in accordance with an embodiment of the invention.
  • traces 44 are connected to pads 92, to which an integrated circuit (IC) chip (not shown) is to be bonded.
  • Pads 92 and traces 44 are formed on substrate 22 by means of printed circuit production techniques that are known in the art, such as photolithographic or direct-writing techniques.
  • Gaps 96 are left open in traces 44 as loci for LIFT printing of embedded resistors, using the process described above.
  • traces 44 to the right of pads 92 in Fig. 5 a number of different types of embedded resistors 98, 100 and 102 have been printed.
  • the widths of the resistive traces in the resistors are limited by the droplet size and trench width, but may be made as small as 6 pm with careful control of process parameters.
  • Resistor 98 simply comprises a straight resistive trace
  • resistors 100 and 102 represent two different sorts of meander patterns.
  • These meander patterns can achieve trace lengths roughly three times that of resistor 98 for a given size of gap 96, and thus can produce resistance values roughly three times greater.
  • Other meander patterns can be used to achieve even larger trace lengths, though at the cost of occupying a wider area on the substrate. To ensure accurate resistance values, it can be useful to clean the spaces between the bends of the meander patterns of resistors 100 and 102 carefully at step 80.
  • Figs. 6A-D schematically show details of a connection between the end of one of circuit traces 44 and embedded resistor 98, in accordance with an embodiment of the invention.
  • Fig. 6A shows a top view
  • Figs. 6B, 6C and 6D are sectional views of the circuit trace and embedded resistor, taken respectively along the lines B-B, C-C and D-D in Fig. 6A.
  • Figs. 6B and 6C show alternative embodiments, in the form of alternative views at the same location on resistor 98, depending on process parameters.
  • a trench 110 has been excavated in the surface of substrate 22, for example by laser ablation at step 74.
  • the width of the trench may be on the order of or even less than the average diameter of droplets 54, and thus holds particle 56 snugly.
  • the size of particle 56 and the depth of trench 110 are such that the particle is entirely contained within the trench.
  • particle 56 extends above the top of trench 110 onto the surface of substrate 22.
  • a port hole 112 has similarly been excavated or otherwise formed in the end of trace 44.
  • Droplets 54 of resistive material are injected by the LIFT process at step 76 to form one or more particles 56 in port hole 112, followed by a spray 114 of smaller particles, to seal off the port hole against incursion of corrosive materials .
  • Figs. 5 and 6A-D are presented here by way of example, and not limitation. Other shapes and forms will be apparent to those skilled in the art after reading the present description and are considered to be within the scope of the present invention. Furthermore, the principles of the present invention may be applied in producing embedded circuit components of other sorts, including components with capacitive and/or inductive properties.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Plasma & Fusion (AREA)
  • Manufacturing Of Printed Wiring (AREA)
  • Parts Printed On Printed Circuit Boards (AREA)
  • Apparatuses And Processes For Manufacturing Resistors (AREA)

Abstract

Un procédé de fabrication d'un dispositif électrique comprend l'identification d'un lieu sur un substrat de circuit sur lequel une résistance ayant une résistance spécifiée doit être formée entre des premier et second points d'extrémité du lieu. Un substrat donneur transparent, ayant des première et seconde surfaces opposées et un film donneur comprenant un matériau résistif formé sur la seconde surface, est positionné à proximité du lieu identifié sur le substrat de circuit, la seconde surface faisant face au substrat de circuit. Des impulsions de rayonnement laser sont dirigées de façon à frapper le film donneur de façon à induire l'éjection de gouttelettes du matériau résistif du film donneur sur le substrat de circuit au niveau des emplacements voisins respectifs le long du lieu avec une séparation entre les emplacements voisins sélectionnés de façon à former une trace de circuit ayant la résistance spécifiée entre les premier et second points d'extrémité.
PCT/IL2019/050037 2018-01-11 2019-01-08 Impression directe de résistances intégrées Ceased WO2019138404A1 (fr)

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Cited By (4)

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WO2022144608A1 (fr) * 2020-12-28 2022-07-07 Orbotech Ltd. Impression lift de fines lignes métalliques
US20220347778A1 (en) * 2020-06-28 2022-11-03 Orbotech Ltd. Laser Printing of Solder Pastes
US20240042773A1 (en) * 2022-08-04 2024-02-08 Reophotonics, Ltd. Large area laser printing system and method
EP4395476A4 (fr) * 2021-08-26 2025-01-15 Shennan Circuits Co., Ltd. Carte de circuit imprimé à résistance enterrée et procédé de traitement

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TWI835579B (zh) * 2023-03-09 2024-03-11 友達光電股份有限公司 雷射光源系統

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US20030174877A1 (en) * 2001-12-31 2003-09-18 Orbotech Ltd Method for inspecting patterns
US20100309308A1 (en) * 2008-01-16 2010-12-09 Orbotech Ltd. Inspection of a substrate using multiple cameras
JP2015144252A (ja) * 2013-12-15 2015-08-06 オーボテック リミテッド プリント回路配線の修復
US20170189995A1 (en) * 2014-05-27 2017-07-06 Orbotech Ltd. Printing of 3d structures by laser-induced forward transfer
US20170250294A1 (en) * 2014-10-19 2017-08-31 Orbotech Ltd. LIFT printing of conductive traces onto a semiconductor substrate

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US20030174877A1 (en) * 2001-12-31 2003-09-18 Orbotech Ltd Method for inspecting patterns
US20100309308A1 (en) * 2008-01-16 2010-12-09 Orbotech Ltd. Inspection of a substrate using multiple cameras
JP2015144252A (ja) * 2013-12-15 2015-08-06 オーボテック リミテッド プリント回路配線の修復
US20170189995A1 (en) * 2014-05-27 2017-07-06 Orbotech Ltd. Printing of 3d structures by laser-induced forward transfer
US20170250294A1 (en) * 2014-10-19 2017-08-31 Orbotech Ltd. LIFT printing of conductive traces onto a semiconductor substrate

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220347778A1 (en) * 2020-06-28 2022-11-03 Orbotech Ltd. Laser Printing of Solder Pastes
WO2022144608A1 (fr) * 2020-12-28 2022-07-07 Orbotech Ltd. Impression lift de fines lignes métalliques
EP4395476A4 (fr) * 2021-08-26 2025-01-15 Shennan Circuits Co., Ltd. Carte de circuit imprimé à résistance enterrée et procédé de traitement
US20240042773A1 (en) * 2022-08-04 2024-02-08 Reophotonics, Ltd. Large area laser printing system and method

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CN111684550A (zh) 2020-09-18

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