Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
  • B22F7/02—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers
  • B22F7/04—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers with one or more layers not made from powder, e.g. made from solid metal
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/20—Exposure; Apparatus therefor
  • G03F7/2022—Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/20—Exposure; Apparatus therefor
  • G03F7/2002—Exposure; Apparatus therefor with visible light or UV light, through an original having an opaque pattern on a transparent support, e.g. film printing, projection printing; by reflection of visible or UV light from an original such as a printed image
  • G03F7/2014—Contact or film exposure of light sensitive plates such as lithographic plates or circuit boards, e.g. in a vacuum frame
  • G03F7/2016—Contact mask being integral part of the photosensitive element and subject to destructive removal during post-exposure processing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/24—After-treatment of workpieces or articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/0042—Photosensitive materials with inorganic or organometallic light-sensitive compounds not otherwise provided for, e.g. inorganic resists
  • G03F7/0043—Chalcogenides; Silicon, germanium, arsenic or derivatives thereof; Metals, oxides or alloys thereof
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/20—Exposure; Apparatus therefor
  • G03F7/2002—Exposure; Apparatus therefor with visible light or UV light, through an original having an opaque pattern on a transparent support, e.g. film printing, projection printing; by reflection of visible or UV light from an original such as a printed image
  • G03F7/2014—Contact or film exposure of light sensitive plates such as lithographic plates or circuit boards, e.g. in a vacuum frame
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/40—Treatment after imagewise removal, e.g. baking
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/24—After-treatment of workpieces or articles
  • B22F2003/247—Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/24—After-treatment of workpieces or articles
  • B22F2003/248—Thermal after-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/05—Light metals
  • B22F2301/052—Aluminium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/10—Copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/25—Noble metals, i.e. Ag Au, Ir, Os, Pd, Pt, Rh, Ru
  • B22F2301/255—Silver or gold
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
• • 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
  • H05K1/02—Details
  • H05K1/09—Use of materials for the conductive, e.g. metallic pattern
  • H05K1/092—Dispersed materials, e.g. conductive pastes or inks
  • H05K1/097—Inks comprising nanoparticles and specially adapted for being sintered at low temperature
• • 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
  • H05K2201/01—Dielectrics
  • H05K2201/0137—Materials
  • H05K2201/0145—Polyester, e.g. polyethylene terephthalate [PET], polyethylene naphthalate [PEN]
• • 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
  • H05K2203/01—Tools for processing; Objects used during processing
  • H05K2203/0104—Tools for processing; Objects used during processing for patterning or coating
  • H05K2203/013—Inkjet printing, e.g. for printing insulating material or resist
• • 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
  • H05K2203/05—Patterning and lithography; Masks; Details of resist
  • H05K2203/0548—Masks
• • 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
  • H05K2203/07—Treatments involving liquids, e.g. plating, rinsing
  • H05K2203/0756—Uses of liquids, e.g. rinsing, coating, dissolving
  • H05K2203/0766—Rinsing, e.g. after cleaning or polishing a conductive pattern
• • 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
• • 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
  • H05K2203/1131—Sintering, i.e. fusing of metal particles to achieve or improve electrical conductivity
• • 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
  • H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
  • H05K3/06—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed chemically or electrolytically, e.g. by photo-etch process
• • 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
  • H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
  • H05K3/06—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed chemically or electrolytically, e.g. by photo-etch process
  • H05K3/061—Etching masks
  • H05K3/064—Photoresists
• • 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
  • H05K3/46—Manufacturing multilayer circuits
  • H05K3/4644—Manufacturing multilayer circuits by building the multilayer layer by layer, i.e. build-up multilayer circuits
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
  • H10K10/40—Organic transistors
  • H10K10/46—Field-effect transistors, e.g. organic thin-film transistors [OTFT]
  • H10K10/462—Insulated gate field-effect transistors [IGFETs]
  • H10K10/464—Lateral top-gate IGFETs comprising only a single gate
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
  • H10K10/40—Organic transistors
  • H10K10/46—Field-effect transistors, e.g. organic thin-film transistors [OTFT]
  • H10K10/462—Insulated gate field-effect transistors [IGFETs]
  • H10K10/466—Lateral bottom-gate IGFETs comprising only a single gate
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/60—Forming conductive regions or layers, e.g. electrodes
  • H10K71/611—Forming conductive regions or layers, e.g. electrodes using printing deposition, e.g. ink jet printing
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/621—Providing a shape to conductive layers, e.g. patterning or selective deposition
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K77/00—Constructional details of devices covered by this subclass and not covered by groups H10K10/80, H10K30/80, H10K50/80 or H10K59/80
  • H10K77/10—Substrates, e.g. flexible substrates

Definitions

• the present disclosure relates generally to fabrication techniques for printable electronic devices and, in particular, to a technique for aligning layers in fabricating a multilayer printable electronic device.
• Printing functional inks on flexible and low-cost substrates is an increasingly popular method of fabricating electronic devices.
• a multilayer printing process which is frequently utilized in fabricating electronic devices, remains challenging because it is difficult to achieve the required alignment or registration precision when an upper layer is printed over an under layer.
• a self-alignment process was proposed (Palfinger ef a/. , Adv. Mater. 2010, 22, 51 15-51 19) for printing organic transistors.
• the first metal layer is patterned by nano-imprint lithography or a micro- contact printing process followed by a wet etching step.
• This patterned metal layer later acts as a mask to pattern the next metal layer via a traditional or a roll-to-roll (R2R) photo-lithography process and a lift-off step.
• R2R roll-to-roll
• metal layers are vacuum evaporated, and several photolithography, wet-etching, and lift-off steps are required.
• UV-curable metal inks which are UV-curable resins filled with metal particles, are potential candidates for use in a self-alignment process to replace the vacuum deposited metal layers.
• UV-curable metal inks contain photo initiators and cross-linkers, which remain in the film and reduce the conductivity of the resulting metal film.
• printed metal films are opaque, the UV penetration depth is very limited in this kind of film, and the thickness that can be cross-linked is also very limited.
• the achievable patterning resolution of the inks is fundamentally limited to the size of its metal particles.
• the present disclosure provides a new self-aligning technique for fabricating multi-layer printable electronic devices.
• This method enables high- precision alignment of the metal pattern printed on the upper layer with the ink pattern on the lower or under layer.
• a metal nano particle ink or any other equivalent ink acts as a negative photoresist so that the first metal layer printed or deposited on a transparent substrate can act as a mask.
• Intense light pulses are then applied from the backside of the substrate to partially sinter the metal nano particles that are exposed.
• the metal nano-particles in the shaded area are not sintered and thus can be washed away.
• Partially sintered particles are then fully sintered in a post sintering step.
• Partially sintering involves exposing the particles to the minimum required optical power with the shortest pulses to minimally sinter the exposed particles so they are just barely connected to the functional layer to resist washing off the functional layer during subsequent washing.
• one inventive aspect of the present disclosure is a method for aligning metal layers in fabricating a multilayer printable electronic device.
• the method entails providing a transparent substrate upon which a first metal layer is deposited, providing a transparent functional layer over the first metal layer, depositing metal nano particles over the functional layer to form a second metal layer, exposing the metal nano particles to intense pulsed light via an underside of the substrate to partially sinter exposed particles to the functional layer whereby the first metal layer acts as a photo mask, and washing away unexposed particles using a solvent to leave partially sintered metal nano particles on the substrate.
• the functional material may be a conductor, semiconductor, dielectric, electroluminescent, photovoltaic, or any other electronic function.
• Figure 1 illustrates an example of how metal nano particles are used as a negative photoresist
• Figure 2 illustrates, by way of example, a method of self-aligning metal patterning based on the photo sintering of metal nano particles
• Figure 3A illustrates a dried coating of silver nano particle ink produced on PET film
• Figure 3B illustrates the coating of silver nano particles on PET after the sample was exposed to intense pulsed light under another PET film bonded with dark tape strips on its upper surface;
• Figure 3C illustrates the coating of silver nano particles on PET when the exposed sample is immersed into dehydronapthalene for development
• Figure 3D illustrates the coating that remains after the unexposed sample was washed with dehydronapthalene
• Figure 4A illustrates the pre-existing silver pattern of silver nano particles coating on PET
• Figure 4B illustrates the coating formed of silver nano particles on the opposite side of the above PET after the sample was exposed to light from the side with the pre-existing silver pattern and washed with a solvent
• Figure 5A illustrates a pre-existing silver pattern formed of silver nano particles on one side of PET;
• Figure 5B illustrates the pattern of silver nano particles on the opposite side after the sample was exposed to light from the patterned side and washed with a solvent;
• Figures 6A-6D depict the processed coating of silver nano particle ink on PET film wherein the coating, before being developed in water, was exposed to intense pulsed light from the back side of the PET which was previously printed with a silver pattern;
• Figures 7A and 7B depict a coating of silver nano particles on PET film wherein the coating was exposed to intense pulsed light from a back side of its substrate;
• Figures 8A and 8B depict a coating of silver nano particle ink on a PMMA- covered PET film wherein 300nm PMMA was coated on the PET with the printed silver pattern and the sample was exposed to intense pulsed light from the back side of the PET with subsequent development carried out in water;
• Figures 9A and 9B depict a coating of silver nano particle ink on PMMA- covered PET film wherein 300nm PMMA was coated on a PET surface with the printed silver pattern and the sample was exposed to intense pulsed light from the back side of the PET and the subsequent development was carried out in ethanol; and
• Figures 10A and 10B depict a line of silver nano particle ink on a PMMA- covered PET film wherein the line of ink was printed on 300nm-PMMA on PET film using an inkjet printer and the light exposure was from the back side of the PET film and the development was carried out in water.
• a method (or process) of using a photonic sintering process and metal nano particle inks for self-alignment metal patterning This method obviates the need for multiple photolithography steps or for metal vacuum deposition.
• High-precision alignment between the metal pattern in the upper layer and the lower and under layer is achieved by using the metal nano particle ink as a negative photoresist.
• the first metal layer printed on a transparent substrate acts as a mask to block light applied from the back side of the substrate.
• the intense light pulses applied from the backside of the substrate partially sinter the nano particles that are exposed, i.e. not covered by the mask.
• the metal nano-particles that are masked are unaffected by the sintering and thus can be washed away.
• the method is primarily intended for use in fabricating electronic devices having a multilayer structure by printing or an equivalent low-cost deposition process.
• Many electronic devices require a multilayer structure, in which the pattern of one of the upper layers has to be precisely aligned with the pattern in the layer underneath in order to function correctly or optimally.
• a transistor requires that the metal electrodes in the upper layer be precisely aligned with the ones in the layer underneath.
• the method disclosed herein uses photonic sintering of metal nano particles to precisely align the metal pattern in the upper layer with the metal pattern in the layer beneath. In other words, this method facilitates fabrication of multilayer printable electronic device which require precise alignment of the upper and lower layers.
• Metal nano particles exhibit strong plasmonic absorption in the wavelength range from UV to near IR, and thus can be heated by light. Metal nano particles also have very low melting temperature because of their nano size and thus can be sintered at a very low temperature such as, for example, 120°C. As such, it is possible to use the heat generated by the plasmonic absorption to sinter the particles onto the substrate. Both laser and intense pulsed light may be used to directly irradiate and thus sinter metal nano-particle particles to produce coatings and patterns on the substrate.
• the photonic sintering of metal nano particles can cause the individual particles to form a dense metal film. This process is somewhat similar to the UV- caused crosslinking of a polymer, which makes the polymer insoluble. However, there are a few fundamental differences between the two: 1 ) the UV-crosslinking reaction is directly caused by the photons in the UV light, and therefore the cross- linking depth is limited by the depth of light penetration. In the case of printed metal films, the cross-linking depth is limited to the surface area; while the sintering of the metal nano particles are caused by the local heat generated by the intense, short light pulses. Although the light pulse is also limited in depth of penetration, the heat generated by the light pulses can transfer over a reasonable range (100's nm).
• This transfer range is sufficiently large to sinter metal films used in typical printable electronics (having a typical thickness of ⁇ 100's nm). Moreover, photonic sintering yields very good lateral patterning resolution (100's nm vs 10's ⁇ ). Furthermore, the heat transfer range can be controlled by varying the pulse intensity, frequency and duration; 2) the UV-crosslinking process requires photo initiators and cross- linkers, which will remain in the films and affect their properties.
• the sintering of the metal nano particles is basically a particle melting process, such that the resulting films have properties very similar to the bulk material; 3) the UV- crosslinking process uses the inks that are based on the UV curable polymer filled with metal particles, normally several micrometers in diameter or length. The achievable patterning resolution cannot be smaller than the particle size.
• Figure 1 illustrates a method of using metal nano particles to function as a negative photoresist.
• the metal nano particles are first deposited on the substrate by a suitable deposition method, such as coating or printing, using metal nano particle-suspended liquid, or so-called nano ink.
• the particles are exposed to intense pulsed light, through a photo mask, whose wavelength substantially covers or matches that of the plasmonic absorption of the particles.
• the exposed particles are partially sintered by the absorbed energy to thereby adhere to the substrate when a solvent is used to wash away the unexposed particles in the development process.
• a post sintering process is performed to fully sinter the particles onto the substrate to become a dense metal film with desired performance characteristics.
• Figure 2 illustrates the self-alignment method for metal patterning.
• the method employs photonic sintering of metal nano particles.
• the nano particle ink is deposited on the substrate surface with the first metal pattern underneath, either separated by a transparent layer of material for special functions or by the substrate itself.
• the light is shined from the back side of the substrate.
• the metal pattern on the under layer acts as a photo mask.
• Exposed particles adhere to the substrate due to photonic-induced partial sintering.
• These partially sintered particles remain on the surface through the development process. After being thermally annealed, the remaining material, which is precisely aligned to the pre-existed metal pattern, is fully sintered in a post sintering process to obtain the desired performance characteristics, such as conductivity.
• Figure 2 shows the structure of a stack composed of a transparent substrate 10 upon which a first metal layer 12 is deposited, a transparent functional layer 14 over the first metal layer, and a second metal layer 16 that is formed by depositing metal nano particles on the transparent functional layer 14.
• the metal nano particles are then partially photonically sintered to leave partially sintered particles 18 that form a pattern or line that remain after the second metal layer is washed with an appropriate solvent.
• the sintered particles 18 that remain after sintering are aligned with the first metal layer.
• the functional layer is made of a functional material which may be a conductor, semiconductor, dielectric, electroluminescent, photovoltaic, or any other electronic function.
• Photonic sintering of metal nano particles is fundamentally different from the conventional UV-induced photo crosslinking of polymer widely used in photolithography-based fabrication techniques.
• the conventional UV-induced photo crosslinking process relies on light penetration in the film to be cured. The UV light does not penetrate well in a printed metal film.
• the photonic sintering patterning process is fundamentally still a sintering process, in which particles are fused together at their surfaces through the heat generated by the plasmonic absorption of the metal nano particles. The heat may be quickly transferred from the exposed particles to adjacent unexposed particles, due to the high thermal conductivity of metal, causing sintering in the unexposed area, both in the thickness direction and side direction of the nano particle coating.
• the present method employs partial sintering. It uses the minimum required optical power with the shortest pulses to minimally sinter the exposed particles so they are just barely connected or fused to the level that they become resistant to the solvent used to disperse or suspend the nano particles and have a sufficient adhesion on the substrate. With this, the unexposed nano particles can be easily and cleanly washed away with the solvent used to disperse the particles in their original liquid sample or ink, and the exposed ones will stay on the substrate.
• the desired performance characteristic, such as electrical conductivity, of the obtained film formed by the partially connected nano particles might be poor at this stage, but can be dramatically improved to the application- required level after the particles are fully sintered in a post sintering process.
• the method was demonstrated by coating a thin layer of silver nano particles on a piece of DuPont PET film (Melinex ST 505) and exposing the coating to intense pulsed light under another piece of PET film with dark polymer tape strips bonded on its upper surface.
• the coating of silver nano particles on PET film was prepared using XF-1 silver nano ink produced by Xerox research center in Canada (XRCC) and the blade coating equipment (509MC) of Erichsen, and dried at room temperature (as shown by Figure 3A).
• XRCC Xerox research center in Canada
• Figure 3A Another piece of PET film with bonded dark tape strips on its upper surface was used as a photo mask and placed on top of the coated PET film as illustrated by way of example in Figure 1 .
• the nano-particle coating was exposed to the programmed intense pulsed light (2.4kV, double exposure at 200 microseconds for each one, with a plate displacement of 5 mm in each cycle) in the photonic curing R&D system (Sinteron 2000 from Xenon Corporation) through the above mask, the lit part turned a gold color, while the blocked and thus unexposed parts kept their original color (as shown in Figure 3B).
• the unexposed parts turned a black color instantly (as shown in Figure 3C) and gradually diffused into the solvent.
• the transparent PET was recovered in the unexposed area to show the corresponding patterns of the dark tape strips, after the unexposed silver particles were completely washed away with sharp edges left in the remaining coating (as shown in Figure 3D).
• the resistance of the remaining coating (which was 660 nm thick) was measured to be in the range of 30 to 60 kQ between two adjacent corners. The resistance value dropped to 0.9 to 1 .3 ⁇ after the sample was thermally annealed at 130°C for 30 minutes.
• Melinex ST 505 from DuPont with a stable printed silver pattern on one side was coated with XF-1 silver nano ink produced by the Xerox Research Center in Canada (XRCC) on another side using the blade coating equipment, e.g. the 509MC from Erichsen).
• the room temperature-dried coating was placed in the photonic curing R&D system (e.g. Sinteron 2000 from Xenon Corporation) with the pre-printed silver facing up and the new coating facing down for light exposure (which was carried out, for example, at 2.4kV, with double exposure at 180 microseconds for each one, and with a plate displacement of 5 mm in each cycle).
• the sample was immersed into a baker containing dehydronapthalene (as one example of a suitable solvent) to wash the unexposed area.
• dehydronapthalene as one example of a suitable solvent
• ultrasonic waves were applied to the solution by placing the dehydronapthalene-containing baker in an ultrasonic water bath.
• the coating which had, in this example, a thickness of 1010 nm, was seen to have the reversed pattern of the printed silver pattern, as shown in the comparison of a printed silver grid ( Figure 4A) with the patterned coating ( Figure 4B).
• the area blocked by the pre-existing (pre-printed) silver pattern was removed and the two separate patterns were precisely aligned with each other.
• the lowest resistance of the remaining coating between two adjacent corners was measured to be 130 kQ, which dropped to 1 .2 ⁇ after the sample was thermally annealed at 130°C for 30 minutes.
• each pattern of the remaining silver particle coating was observed to precisely mirror the corresponding pre-existing silver pattern that was used to block the light.
• Figures 5A and 5B it can be observed under an optical microscope that, after the process is complete, the area covered by the pre-existing silver pattern on the other side of the PET film (Figure 5A) is free of silver on the silver nano particle-coated side of the film ( Figure 5B). Even the edge defects in the pre-existing silver pattern are transferred to the newly generated pattern, which further demonstrates the high precision of the alignment between the two layers.
• a PET film (ST 505 from Dupont) with a silver pattern printed on one side was spread-coated with silver nano ink (EMD5603 from Sunjet) on its other side using a glass tube. After being dried at 65°C, the coating was exposed in the photonic curing R&D system (Sinteron 2000 from Xenon Corporation) with the printed silver pattern facing up and the new coating facing down. The light exposure was carried out in the condition of 2.6kV, continuous exposure at 120 microseconds, and a plate displacement of 1 mm/s.
• the sample was immersed into water in a baker, which was placed in the water bath of an ultrasonic cleaner for 1 minute, and then rinsed with clean water.
• the dried coating was seen to have the nano particles completely removed in the area blocked by the printed silver on the opposite side of the PET film, and the edges of the remaining coating precisely mirrored the ones of the printed silver (as shown by way of example in Figure 6). After post thermal annealing, the remaining coating was measured to be highly conductive.
• a silver nano particle paste (ANP-NRC- 140812 from Advanced Nano Product Co.) was diluted with a-terpinol and spread- coated on the PET film (ST 505 of Dupont) with a silver pattern printed on its other side using a glass tube. After being dried at 65°C, the coating was exposed in the photonic curing R&D system (Sinteron 2000 from Xenon Corporation) with the printed silver pattern facing up and the coating facing down. The light exposure was carried out in the condition of 2.8kV, continuous exposure at 300 microseconds, and a plate displacement of 1 mm/s.
• the sample was immersed into methanol in a baker, which was placed in the water bath of an ultrasonic cleaner for 10 minutes, and then rinsed with clean methanol.
• the dried coating was seen to have the nano particles completely removed from the area blocked by the printed silver on the opposite side of its substrate, and the edges of the remaining coating precisely mirrored the ones of the printed silver (as shown by way of example in Figure 7.
• silver nano ink EMD5603 from Sunjet
• the dried coating was exposed in the photonic curing R&D system (Sinteron 2000 of Xenon Corporation) with bare PET facing up and the new coating facing down.
• the light exposure was carried out in a condition of 2.6kV, continuous exposure at 200 microseconds, and a plate displacement at 1 mm/s.
• the nano particles over the pre-existing silver pattern were completely removed and the exposed particles remained, having been partially sintered by the light.
• the edges of the two layers precisely match with each other as shown by way of example in Figure 8.
• the nano particles were even deposited within the narrow gaps of the preexisting silver lines (as depicted in Figure 8A).
• the obtained pattern of the nano- particle coating in this case has better edge quality than that of the one when the pre-existing silver pattern was on the other side of the PET film ( Figure 6).
• Example 6 a layer of 300 nm-thick PMMA was first deposited on the PET surface with a printed silver pattern in a process as described above, and the silver of Advanced Nano Product Co. (ANP-NRC-140812) was spread coated on the PMMA using a glass tube in the process as described earlier. The dried coating was exposed in the photonic curing R&D system (Sinteron 2000 from Xenon Corporation) with bare PET facing up and the new coating facing down, and in the condition of 2.8kV, continuous exposure at 300 micro seconds, and plate displacement at 1 mm/s. Subsequently, the sample was developed in ethanol with the assistance of ultrasonic waves.
• Figure 9 shows the obtained pattern of the silver nano particle coating with sharper edges than that when the pre-existed silver pattern was on the other side of the PET film as in Example 4.
• the improved resolution described above is mostly due to the reduced light diffraction.
• the PET film was 170 ⁇ thick and the light source used for exposure was not collimated in the setup, the light masked from the pre-existing silver pattern may diffract into the other area of the nano particle coating on the another side of the PET film.
• the coating is sitting on the pattern layer with an interlayer only 300 nm thick, such diffraction is substantially decreased.
• the present method would work very well.
• Example 7 For printable electronics, it is desirable to be able to precisely print the material only in a desired area.
• Example 7 the present method was demonstrated in self-aligned silver line printing.
• Silver nano ink (EMD5603) from Sunjet was printed on the PMMA covered surface as described in Example 5 using an inkjet printer (DMP5005) from Damatix as parallel lines.
• the dried lines (200 nm thick) were exposed in the photonic curing R&D system (Sinteron 2000 from Xenon Corporation) with bare PET facing up and the printed lines facing down in the condition of 2.6kV, continuous exposure for 200 microseconds, and plate displacement of 1 mm/s.
• FIG 10A shows the area where a printed line crosses over two pre-existing silver lines. The material in the line was removed in the area where there were pre-existing silver lines underneath, resulting in the structure similar to a top-gated transistor or a bottom-gated transistor.
• Figure 10B shows that the etched edges of the printed line precisely match the line edges of the preexisting silver line, thus demonstrating that the self-aligning technique disclosed herein can be used to fabricate high-precision aligned layers for a printable electronic device.
• the present method provides for self-alignment of a first layer with a second layer.
• This method for aligning layers is useful, as noted above, in fabricating a multilayer printable electronic device.
• the first and second layers may be printed with conductive metal nano particle ink to form part of a bottom-gated or top-gated transistor.
• the method may be summarized as including the following steps, acts or operations: providing a transparent substrate upon which a first metal layer is deposited, providing a transparent functional layer (such as, for example, a dielectric layer or a semiconducting layer) over the first metal layer, depositing metal nano particles over the functional layer to form a second metal layer, exposing the metal nano particles to intense pulsed light via an underside of the substrate to partially sinter exposed particles to the functional layer whereby the first metal layer acts as a photo mask, and washing away unexposed particles using a solvent to leave partially sintered metal nano particles on the substrate. Partially sintered particles may then be post sintered in order to fully sinter the particles to the substrate.
• a transparent functional layer such as, for example, a dielectric layer or a semiconducting layer
• Post sintering may be accomplished by photonic sintering or thermal treatment (annealing). Washing may be enhanced by exposing the partially sintered particles to ultrasonic waves.
• a particle- carrying solvent is first evaporated before exposing the particles to the intense pulsed light.
• the substrate is a polyethylene terephthalate (PET) film and the metal nano particles are silver nano particles. Based on the test results and examples described above, it stands to reason that other metal nano inks and other substrates may be employed to achieve substantially similar self-alignment results.
• the substrate may alternatively be a polyethylene-naphthalate (PEN) film, a polyimide film, a polycarbonate film, or glass.
• the particles may alternatively be gold, copper or aluminum. Partial sintering may be achieved with pulsed light having a wavelength of 300 to 900 nm, a voltage level of 1 kV-3kV, and an exposure time of 100-1000 microseconds.

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