JP2017513040A - Metallization by direct laser writing in pulse mode - Google Patents

Abstract

The manufacturing method includes coating the substrate 22 with a matrix 28 containing a material to be patterned on the substrate. The pattern is fixed in the matrix by directing the pulse energy beam to impinge on the pattern trajectory to adhere the material to the substrate along the pattern without completely sintering the material in the pattern. . The matrix remaining on the substrate outside the fixed pattern is removed. After removal of the matrix, the material in the pattern is sintered.

Description

  The present invention relates generally to the generation of printed wiring on a circuit board, and more particularly to a method and system for direct writing of metal features.

  Direct laser sintering of metal ink is a known technique for printed wiring metallization. For example, US Patent Application Publication No. 2008/0286488 describes a method for forming a conductive film based on depositing a non-conductive film on a substrate surface. The film includes a plurality of copper nanoparticles. When at least a portion of the film is exposed, the exposed portion becomes conductive due to photosintering or coalescence of the copper nanoparticles.

  Kumpulainen et al., In Optics & Laser Technology 43 (2011), pages 570-576, “Low Temperature Nanoparticulate Sintering with Continuous Laser and Pulsed Lasers”. The authors include additives such as dispersants and dispersion media in which the nanoparticulate ink printed on the substrate surface changes viscosity and provides superior printing properties by separating the ink nanoparticles. , "Printable electronics" is mentioned. In the sintering process, the ink particles are heated to a specific ink specific temperature and the dispersion medium and dispersant are evaporated from the ink. With additional heating after evaporation, the nanoparticles begin to aggregate. Laser sintering is said to allow printed structures to accommodate fragile active parts produced with other technologies by allowing for reduced sintering time and selective sintering. This paper describes tests using two different types of lasers: pulsed and continuous.

  After the priority date of this patent application, Theodorakos et al., Applied Surface Science 336 (2015), “Selective Laser Sintering of Ag Nanofibers Applied Technology”, page 157-162. doing. The authors refer to continuous wave (CW) lasers, nanosecond pulsed lasers, picosecond pulsed lasers operating at 532 nm and 1064 nm as an efficient means of selective laser sintering of Ag nanoparticle ink layers on flexible substrates. We are investigating the possibilities of three different laser sources. Theoretical simulation shows that when a picosecond laser pulse is used, the heat affected part is limited to only a few micrometers around the irradiated area of the ink layer. These predictions were confirmed experimentally.

  Embodiments of the present invention provide improved methods and systems for laser direct writing of wiring on a substrate.

  Therefore, a method for manufacturing according to an embodiment of the present invention is provided. The method includes coating the substrate with a matrix containing a material to be patterned on the substrate, and pulsed to adhere the material to the substrate along the pattern without completely sintering the material in the pattern. Fixing the pattern in the matrix by directing the energy beam into the pattern trajectory. The matrix outside the fixed pattern remaining on the substrate is removed. After removal of the matrix, the material in the pattern is sintered.

  In some embodiments, the material to be patterned includes nanoparticles. In the disclosed embodiment, the material in the nanoparticles is electrically conductive and the pulsed energy beam is applied to the final wire resistance after pattern fixation is achieved by complete sintering of the material in the pattern after removal of the matrix. A pulse of radiation having an energy fluence and repetition frequency selected to remain at least 10 times higher than the typical resistivity.

  Typically, directing the pulsed energy beam includes directing a train of pulses of the energy beam to impact each position within the trajectory on the substrate.

  In disclosed embodiments, the pulse energy beam has a pulse repetition frequency of at least 1 MHz, and in some cases at least 10 MHz.

  Typically, the matrix includes an organic compound in addition to the material to be patterned, and the step of directing the pulsed energy beam is selected to evaporate the organic compound from the matrix without completely sintering the material in the pattern. Directing a train of pulses of energy beam having a fluence per pulse. The fluence per pulse applied in pattern fixation is sufficient for the material to allow the organic compound to evaporate through the pores in the material without causing ablation or delamination of the material due to evaporation of the organic compound. Is selected to maintain good porosity.

  In some embodiments, sintering the material includes applying a bulk sintering process to the pattern that is secured to the substrate. Alternatively, sintering the material includes directing a further pulse of a pulsed energy beam to sinter a pattern fixed on the substrate.

  In disclosed embodiments, coating the substrate includes drying the matrix on the substrate before irradiating the coated substrate. Additionally or alternatively, removing the matrix includes contacting the solvent to remove the matrix outside the fixed pattern that remains on the substrate.

  A method for manufacturing according to an embodiment of the present invention is also provided. The method includes coating a substrate with a matrix containing a material to be patterned on the substrate and directing a pulsed energy beam having a pulse that includes a tilted time profile for impinging on a point on the coated substrate. And directing the pulse energy beam to include a sufficient fluence to fix the material to the substrate and to sinter the material on the point.

  In disclosed embodiments, the matrix includes an organic compound in addition to the material immobilized on the substrate, and the tilted time profile and fluence allows the material to be ablated or stripped due to evaporation of the organic compound. The organic compound is selected to evaporate from the matrix prior to sintering. In some embodiments, the material includes nanoparticles, and sintering of the material causes the nanoparticles to fuse at that point. In the disclosed embodiment, the duration of the pulse is 20 nanoseconds or less.

  In some embodiments, directing the pulsed energy beam includes forming a pattern of material on the substrate by directing the pulse and impinging on a sequence of points defining a pattern on the coated substrate. including. The points in the column cannot overlap each other. Typically, the method includes the step of removing the matrix outside the pattern trajectory that remains on the substrate after pattern formation.

  A system for manufacturing according to an embodiment of the present invention is additionally provided. The system includes a coating apparatus configured to coat the substrate with a matrix that includes a material to be patterned on the substrate. The drawing device directs the pulse energy beam to impinge on the pattern trajectory so that the material adheres to the substrate along the pattern without completely sintering the material in the pattern. It is configured to be fixed to. The matrix removal device is configured to remove the matrix remaining on the substrate and outside the fixed pattern. The sintering apparatus is configured to sinter the material in the pattern after removal of the matrix.

  Further provided is a system for manufacturing according to an embodiment of the present invention. The system includes a coating apparatus configured to coat the substrate with a matrix that includes a material to be patterned on the substrate. The drawing apparatus has a pulse energy with a pulse that includes a tilted time profile to cause the material to be fixed to the substrate and to cause the material to sinter at a point on the coated substrate and to strike the point on the coated substrate. It is configured to direct the beam.

  The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which:

1 is a schematic diagram showing a laser direct drawing system and stages in operation of the system according to an embodiment of the present invention. 1 is a schematic top view of a substrate on which a wiring pattern is drawn according to an embodiment of the present invention, one of which is illustrated in successive stages of the pattern forming process. FIG. 1 is a schematic top view of a substrate on which a wiring pattern is drawn according to an embodiment of the present invention, one of which is illustrated in successive stages of the pattern forming process. FIG. 1 is a schematic top view of a substrate on which a wiring pattern is drawn according to an embodiment of the present invention, one of which is illustrated in successive stages of the pattern forming process. FIG. 1 is a schematic top view of a substrate on which a wiring pattern is drawn according to an embodiment of the present invention, one of which is illustrated in successive stages of the pattern forming process. FIG. 1 is a schematic top view of a substrate on which a wiring pattern is drawn according to an embodiment of the present invention, one of which is illustrated in successive stages of the pattern forming process. FIG. 1 is a schematic cross-sectional view of a substrate on which wiring is drawn, according to one embodiment of the present invention, one of which is illustrated in successive stages of the process of forming the wiring. 1 is a schematic cross-sectional view of a substrate on which wiring is drawn, according to one embodiment of the present invention, one of which is illustrated in successive stages of the process of forming the wiring. 1 is a schematic cross-sectional view of a substrate on which wiring is drawn, according to an embodiment of the present invention, one of those illustrated with continuous time in fixing the wiring. FIG. 1 is a schematic cross-sectional view of a substrate on which wiring is drawn, according to an embodiment of the present invention, one of those illustrated with continuous time in fixing the wiring. FIG. 1 is a schematic cross-sectional view of a substrate on which wiring is drawn, according to an embodiment of the present invention, one of those illustrated with continuous time in fixing the wiring. FIG. 1 is a schematic cross-sectional view of a substrate on which wiring is drawn, according to an embodiment of the present invention, one of those illustrated with continuous time in fixing the wiring. FIG. 4B is a schematic cross-sectional view of the substrate and wiring of FIGS. 4A-4D after wiring annealing, according to one embodiment of the present invention. FIG. 6 is a plot illustrating the dependence of the pulse energy threshold on the fixation and damage of wiring drawn on a substrate, according to one embodiment of the invention. 1 is a schematic top view of a substrate with spots drawn on an array of points by a pulsed beam having various pulse parameters according to an embodiment of the present invention. FIG. FIG. 3 is a schematic top view of a pattern formed on a substrate by applying a pulsed beam to a sequence of points according to an embodiment of the invention.

[Overview]
As described in the above PCT patent application PCT / IL2014 / 000013, one-step direct laser sintering of metal inks and other nanoparticulate sinterable inks may not yield sufficiently uniform results. Many. (As used herein and in the claims, the term “nanoparticle” means a microparticle with at least one dimension that is smaller than 100 nm.) At least part of the cause of this problem is local sintering. Derived from the conduction of heat generated during the process. Inhomogeneous heat diffusion under these conditions causes thermal fluctuations and consequently inconsistent sintering. This effect is most noticeable when dealing with high resolution patterning of metal features as small as a few microns. At the same time, direct sintering of metal inks requires a high laser fluence on the order of tens to hundreds of J / cm ² , so this process is slow and inefficient when the area corresponds to large patterns. is there.

  In some embodiments of the present invention, the drawing and sintering steps are separated by a method that improves the uniformity and reliability of the resulting wiring. The substrate can be coated with a suitable matrix and dried to remove excess solvent after coating. (Such matrices usually have inks, pastes or suspensions containing nanoparticles, and are generically referred to herein simply as “NP inks” for reasons of convenience). Next, a pulse energy beam light source such as a laser scans the substrate without completely sintering the nanoparticles to draw a desired pattern. As used herein and in the claims, the term “without fully sintering” means that the nanoparticles in the bulk of the matrix remain substantially separated from one another, and thus the metal nano In the case of particles, this means that the resistivity of the wiring at this stage is still at least 10 times higher compared to the final resistivity achieved after full sintering.

  This stage of the process in which the energy beam draws the pattern is referred to herein as “fixing” the pattern within the matrix. In some embodiments, the beam scans with a train of pulses (or “burst”) over the trajectory of a pattern drawn on the substrate. The pulse has a fluence sufficient to adhere the material to the substrate along the pattern, but well below the full sintering threshold. This fixation stage stabilizes relative to the unirradiated matrix so that the irradiated matrix is not subsequently removed. The use of pulsed irradiation at this stage improves the quality of the pattern wiring by reducing the possibility of damage due to rapid expansion of the gas trapped in the matrix.

  During this fixation phase, until the nanoparticulate material is fully sintered, the material remains sufficiently porous to allow organic compounds in the matrix to evaporate through the pores in the material. This prevents material ablation or delamination, which could otherwise be caused by very rapid evaporation of organic compounds. In order to ensure this type of controlled evaporation, the laser (or other energy source) typically impinges at each position in the pattern at a high repetition frequency, eg, at least 1 MHz, and in some cases higher than 10 MHz. To direct the train of pulses. The fluence per pulse is selected so that the desired porosity of the matrix is maintained until fixation is complete.

  After the pattern is fixed in this way, the matrix is removed from all non-fixed areas, so that only the stabilized pattern remains. Such removal can be achieved, for example, by applying a chemical solvent or by radial ablation. Typically, the substrate is then heated uniformly in a bulk sintering process to sinter the nanoparticles in the remaining pattern. This approach provides uniform metallization as opposed to non-uniformities often encountered when direct laser sintering is used. This approach is also particularly useful for printing thick lines. This is because the laser fixing stage is less sensitive to thickness than full laser sintering, while bulk sintering works well with thick ink wiring, for example, in a furnace.

  Accordingly, these embodiments provide a simple and fast metallization process with fewer steps than conventional methods. The first stage of the process involves only a relatively low laser power. Then, using a high power source with a large cover area, such as a heat source or light strip illumination, a high power flash lamp, or an actual metallization stage that requires a high fluence with a high power laser or laser array ( A bulk sintering process) can be performed. These embodiments are suitable for use in patterning delicate flexible substrates such as plastics and foils because they avoid the locally high temperatures associated with one-step direct laser sintering.

  In other embodiments, a pulsed laser or other energy beam is used for sintering and fixation. In this case, the inventor has found that pulses with a slanted time profile achieve significantly better results compared to conventional pulses (such as square wave pulses) that have approximately uniform intensity over time. discovered. The tilted time profile is beneficial in that it evaporates organic compounds from the matrix coated on the substrate before sintering and thus fusing the nanoparticulate material. The pulsed time profile and fluence of the pulse is selected to improve this effect and thus avoid ablation or delamination of the patterned material due to evaporation of the organic compound. These one-stage embodiments are particularly suitable (although they can be used otherwise) to form spots that are individually sintered on the substrate, or patterns that are constructed from the spots.

  In embodiments of the present invention, the use of a pulsed laser for direct writing (either fixed or direct sintering) provides high resolution with the possibility of adaptive registration as used in digital imaging technology. Is realized. Metal lines and other features formed by the disclosed technique can reach a small width of only a few microns. The resolution is limited only by the laser spot size, which can generally be focused to the 1-2 μm range or even smaller. Resolution and quality with respect to linewidth accuracy can be improved by adjusting laser parameters during scanning. In this way, any pattern can be drawn, sometimes operating directly from computer-aided design and computer-aided manufacturing (CAD / CAM) data.

  In some embodiments, the entire drawing and sintering cycle is performed without contacting the substrate. This feature is particularly beneficial for applications such as the production of photovoltaic cells and plastic electronics foils.

  Other possible applications of the technology described herein include, for example, rear display metallization of liquid crystal and organic light emitting diode (OLED) displays, touch screen metallization, shunting of OLED illuminators. lines), printed electronic circuits and devices on plastic foil. The techniques described herein, with the necessary changes, are made from various NP materials (including not only metals but also semiconductors and dielectric particles (including ceramic particles)), various dielectrics, ceramics, semiconductors, polymers, The present invention can be similarly applied to a drawing pattern on a paper or metal substrate.

The embodiments disclosed herein refer specifically to the formation of a single metallization layer for the sake of brevity, but in alternate embodiments, each layer can be separated by appropriate iterations of the technology. Wiring can be drawn on multiple layers using the same ink or different inks.
[Description of system]

  Reference is now made to FIGS. 1 and 2A-2E, which schematically illustrate the process of system 20 and laser direct writing, according to one embodiment of the present invention. FIG. 1 illustrates the components and the stages in the process performed by the system 20. 2A-2E are schematic top views of the substrate 22 on which wiring patterns are drawn in the system 20, illustrated by successive stages in the process. As described above, the substrate 22 may comprise, for example, glass or other dielectric, ceramic, semiconductor, plastic foil or other polymer material, paper, or metal.

  Initially, coating device 24 applies substrate 22 (FIG. 2A) to a layer of matrix 28 (FIG. 2B) that is uniform in thickness, such as metal nanoparticle (NP) ink, metal NP paste, or metal composite ink or paste. Cover with. Such inks or pastes are, for example, silver, copper, nickel, palladium, and / or gold nanoparticles, and alloys of such metals, or in some cases non-metals such as silicon or ceramic nanoparticles Nanoparticles can be included. The layer thickness of the matrix 28 can vary from about 0.2 μm to over 10 μm depending on the final result required. The coating device 24 may apply any suitable area coating technique known in the art, such as screen printing, slot die or bar coating, spray coating, gravure printing, or spin coating.

  Optionally, the drying device 26 dries the matrix applied to the substrate 22. The ink or paste applied by the coating device 24 typically contains a large amount of solvent, while the metal volume content at this stage is 40% or less. Thus, it may be beneficial, but not essential, to dry the matrix prior to the laser scanning step in order to improve the stability of the matrix and reduce the loss of laser energy to the solvent. Possible drying methods include low temperature firing (by convection or radiation), air flow, vacuum drying, or a combination of these techniques.

  The laser drawing apparatus 30 fixes the pattern of the wiring 42 in the matrix 28 as illustrated in FIG. 2C. In a typical implementation, the substrate 22 coated with the matrix 28 is placed on a suitable table 34 and a beam scanner 36 scans the beam of a pulsed laser 32 (or other suitable pulse energy source) over the substrate. To do.

  The laser 32 “draws” the desired pattern in the matrix by exposing the matrix to a well-defined row of laser pulses at predetermined locations on the film. The pattern is typically determined by the controller 38 based on the appropriate CAD / CAM data stored in the memory 40. As will be discussed further herein, pulse parameters including wavelength, spot size, fluence, duration, pulse shape, scan rate, and repetition frequency are selected to optimize pattern quality. To achieve high throughput, multiple laser beams (generated using multiple lasers or generated by splitting a single high power pulsed laser beam into sub-beams as illustrated in FIG. 1) It can be scanned simultaneously on different areas of the substrate. Each beam can be controlled individually.

  Various types of lasers and laser systems can be used in the laser drawing apparatus 30. In some embodiments, the laser diode light source is directly modulated at high speed to emit pulses of the desired shape on a time scale of 1 nanosecond to tens of nanoseconds. In some of these embodiments, the pulse shape is ramped (as will be further described herein) and has a ramp time adjusted to match the thickness of the interconnect. Also, the pulse parameters can be adjusted according to the width of the wiring. Shorter pulses are used when very thin lines are required. Also, the choice of pulse parameters depends on whether the device 30 is used only for fixation before bulk sintering, or whether the laser 32 is used to fully sinter the wiring.

  Alternatively, a CW laser light source, such as a CW fiber laser, can be modulated with the high repetition frequency necessary to provide the desired pulsed beam. An external high speed modulator such as an electro-optic or acousto-optic modulator may be used for this purpose.

  FIG. 3A is a schematic cross-sectional view showing one of the wires 42 secured in the matrix 28 by the drawing device 30 according to one embodiment of the present invention. The wiring 42 typically does not contain a large amount of sintered metal at this stage, but due to exposure to the laser (as a result of photon or thermal effects), compared to the surrounding matrix 28, It is in a state of a stable substance that has higher adhesion to the substrate 22 and is difficult to be removed from the substrate 22. As described above, the laser parameters of the drawing device 30 are selected to provide the necessary local changes in the characteristics of the matrix. The optimal parameters will depend on the exact material and dimensions of the matrix and the chosen drawing method, and in each case will be determined by empirical testing and evaluation. In any case, the power applied at this stage is significantly less than that required for complete sintering of the nanoparticles in the matrix.

  After irradiation, the matrix removal device 44 removes the unfixed matrix 28 from the entire area of the substrate 22 and leaves only the wiring 42 (FIG. 2D). The apparatus 44 may comprise, for example, a solvent bath for immersing the substrate and washing away the matrix outside the pattern. Alternatively or additionally, the device 44 may apply other types of removal techniques, such as chemical or physical ablation of an unfixed matrix.

  FIG. 3B is a schematic cross-sectional view of the wiring 42 remaining on the substrate 22 after the matrix 28 is removed by the device 44.

  Finally, the wiring 42 remaining on the substrate 22 after removal of the matrix is sintered in a sintering device 46 to provide a sintered wiring 50 as shown in FIG. 2E. The sintering apparatus 46 may comprise a conventional sintering furnace when the substrate 22 is suitable for processing in a conventional sintering furnace (eg, as is generally true for glass substrates). Alternatively, the sintering device 46 may use light sintering, which is generally more suitable for delicate substrates such as plastic foil. Further alternatively, other sintering methods such as plasma sintering or microwave sintering may be suitable for delicate substrates. Both of these methods allow the metal ink pattern to be sintered without damaging the underlying plastic substrate.

  In general, photosintering (or microwave or plasma sintering) is easy when working with copper inks in the ambient atmosphere and when working with inks that contain other metals that are susceptible to oxidation, due to the nature of easily oxidizing copper. Priority is given to furnace sintering. In a suitable atmosphere (ie, non-oxidizing atmosphere and / or reducing atmosphere), copper ink furnace sintering may also be used.

  The sintering apparatus 46 shown in FIG. 1 uses light sintering with a high intensity light source 48 that scans the surface of the substrate 22. The light source 48 may, for example, have a set of laser diodes arranged in a row or stacked, thus providing the required fluence over a larger area. Oclaro Inc. (San Jose, CA), Coherent Inc. (Santa Clara, California), or using a commercially available laser diode bar in the near infrared range (approximately 800-1000 nm), such as that produced by Jenoptik (Jena, Germany), averages on the order of several kilowatts Output can be achieved.

In the next section of this specification, a method that can be applied by the drawing device 30 to fix a desired pattern in the matrix 28 is described. In an alternative embodiment, as illustrated in FIGS. 6A and 6B, the writing device 30 performs sintering by providing sufficient energy to the target points on the substrate that define the pattern. Can do. In this latter case, a separate sintering device 46 is not necessary. The techniques described herein are applied in conjunction with the materials and methods described in the above PCT patent application PCT / IL2014 / 00000014 and other suitable materials and methods known in the art. Can be done.
[Pattern fixation by pulse laser]

  Reference is now made to FIGS. 4A-4E, which are schematic cross-sectional views of the substrate 22 at successive stages of drawing the wiring 52 on the substrate, according to one embodiment of the present invention. FIGS. 4A-4D show the matrix 28 in continuous time during wiring fixation. On the other hand, FIG. 4E shows the wiring 52 after annealing.

  Specifically, FIGS. 4A-4D illustrate the cumulative effect of a burst of pulses directed by a laser 32 for a given position in the matrix 28. FIG. At the start of the process, the nanoparticles 50 are suspended in the bulk volatile organic compound component of the matrix 28. Each successive laser pulse heats the matrix and evaporates a greater amount of organic compound components, resulting in an increase in the density of nanoparticles 50 in the matrix 28 each time the pulse strikes. However, due to the diffusion of heat within the matrix and substrate, the increase in density is nearly uniform throughout the volume of the matrix. Thus, as shown in FIG. 4D, pores remain between the nanoparticles 50 in the matrix 28. Even after almost all of the organic material has been drained from the matrix, the evaporative material can escape through the pores. The nanoparticles fuse together to form a wiring 52 as shown in FIG. 4E only during the subsequent sintering step.

  In contrast, the inventors have found that when CW lasers are used for pattern fixation, the density of nanoparticles tends to increase, especially in the upper layer of the matrix, so that the organic material is confined below it. did. Heating these trapped organic materials leads to rapid explosive evaporation, which causes ablation or delamination of surrounding nanoparticle material, thus reducing the quality of the wiring formed on the substrate.

  In contrast, when radiation pulses are used for fixation, to facilitate the gradual evaporation of the organic compound components of the matrix 28 over the course of the burst of pulses, while avoiding solidification of the upper layer of nanoparticles 50. The pulse parameters are selected. The inventors have discovered that short pulses with pulse widths ranging from about 1 nanosecond to tens of nanoseconds provide the best results. A high repetition frequency (at least 1 MHz and possibly more than 10 MHz) is desirable to achieve rapid fixation of the wiring, and thus high process throughput. Typically, pulse fluence and other parameters are selected to maximize throughput as much as possible without damaging the wiring.

  FIG. 5 is a plot illustrating the effective range for wiring fixation with laser pulses, according to one embodiment of the present invention. For data points in the plot, the abscissa indicates the number of pulses applied to a given point on the substrate 22 and the ordinate indicates the energy fluence per pulse. The lower curve 60 shows the minimum fluence required to fix the pattern in the matrix for any given number of pulses. In other words, as long as the pulse at a given point has at least this minimum fluence over a specified number of pulses, the matrix is not washed away from this point after the fixation phase. The upper curve 62 shows the maximum fluence that can be used without damaging the wiring for a given number of pulses. Above this fluence level, rapid heating of the matrix tends to cause ablation and / or delamination.

Curves 60 and 62 thus define an effective range for matrix 28 pulse locking. As can be seen from FIG. 5, as the number of low fluence pulses increases, the effective range increases and thus the range of process tolerances increases. Within these boundaries, the fluence of pulses and the number of pulses applied at each location can be selected to maximize the throughput of the process while achieving a fixed with the desired consistency. The optimal choice will also depend on the thickness and composition of the matrix 28 and other process parameters such as laser wavelength and spot size. Curves 60 and 62 were generated using a diode laser operating at a wavelength of 980 nm on a 460 nm thick matrix film. Alternatively, pulsed lasers in other parts of the ultraviolet, visible or infrared range can be used. The number of pulses (as reflected in curve 60) required to fix the pattern tends to change exponentially with the film thickness.
[Pulse laser sintering]

  FIG. 6A is a schematic top view of a substrate with spots 74 and 78 drawn on an array of points by a pulsed beam having various pulse parameters, according to one embodiment of the present invention. In this embodiment, the substrate is coated with a matrix comprising nanoparticulate material. The pulsed laser beam was directed to impinge on the substrate at each point in the array with sufficient fluence to fix the material to the substrate and to sinter the material at that point. Again, the laser beam was a diode laser operating at a 980 nm wavelength in the pulse mode. The peak power of the laser pulses applied in forming the spots 74 and 78 was increased from bottom to top in the array shown in FIG. 6A. On the other hand, the pulse duration increased from left to right and the longest pulse duration was set to about 20 nanoseconds. Similar results were obtained at other wavelengths.

  Two different pulse waveforms were used to sinter the spot shown in FIG. 6A. A square pulse waveform 70 was used to sinter spot 74, while a ramped pulse waveform 72 was used to sinter spot 78. Waveform 72 “slopes” in the sense that the instantaneous output of the pulse gradually increases over the pulse duration, with the maximum output occurring near the end of the pulse. The tilted time profile, and the fluence of tilted pulses, allows the organic compound to be removed from the matrix prior to sintering the nanoparticulate material without causing material ablation or flaking due to explosive evaporation of the organic compound. Selected to evaporate. As illustrated by spot 78, this beneficial effect of a ramped waveform is seen over a wide range of peak power and pulse duration. In contrast, a spot 74 formed using the waveform 70 shows a region 76 that has been damaged due to ablation and delamination of the nanoparticle material.

  The sloped waveform 72 is particularly useful in forming a single sintered spot on the substrate. These spots typically have a larger diameter than the laser beam itself due to the lateral thermal diffusion of the beam energy over the neighboring region of the matrix. (The tilted beam waveform is generally not so important in a linear scan because each other point in the line except the first point is preheated as the preceding point is sintered. .) A single spot of this kind can be used to form a pattern on a substrate by directing a laser pulse to impinge on a row of points defining the pattern on the coated substrate. The points in this column need not overlap each other. That is, the beam regions of the laser pulses used to form adjacent spots need not themselves overlap. This is because each spot has a larger area than the laser beam used to fix and sinter the spot. After the pattern is formed in this manner, the matrix remaining on the substrate and remaining outside the pattern trajectory is removed as in the above embodiment.

  FIG. 6B is a schematic top view of a pattern 80 formed on a substrate by applying a pulsed beam to a sequence of points 82, according to one embodiment of the present invention. In this example, the points 82 themselves do not overlap, but the pattern 80 is composed of lines formed by overlapping spots 78. Virtually any desired shape pattern can be efficiently formed in this manner.

  It will be appreciated that the embodiments described above are given by way of example, and that the present invention is not specifically limited to the forms shown and described herein. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described herein above, and those not disclosed in the prior art that would occur to those skilled in the art upon reading the above description. Includes changes and modifications.

Claims (38)

Coating the substrate with a matrix comprising a material to be patterned on the substrate;
Directing a pulse energy beam to impinge on the trajectory of the pattern in the matrix to fix the pattern in the matrix, so that the material in the pattern is not completely sintered without the sintering. Adhering the substance to the substrate along a pattern;
Removing the matrix remaining on the substrate outside of the fixed pattern;
Sintering the material in the pattern after removing the matrix.   The method of claim 1, wherein the material to be patterned comprises a plurality of nanoparticles. The substance in the plurality of nanoparticles is electrically conductive;
The resistivity of the wiring after fixing the pattern is selected to remain at least 10 times higher than the final resistivity achieved by complete sintering of the material in the pattern after removal of the matrix. The pulse energy beam has a pulse of radiation having a high energy fluence and a repetition frequency,
The method of claim 2.   The method of claim 1, wherein directing the pulsed energy beam comprises directing a train of pulses of the energy beam to collide at each position in the trajectory on the substrate.   The method of claim 1, wherein the pulsed energy beam has a pulse repetition frequency of at least 1 MHz.   The method of claim 5, wherein the pulse repetition frequency is at least 10 MHz. The matrix has an organic compound in addition to the material to be patterned,
Directing the pulsed energy beam comprises a plurality of energy beams having a fluence per pulse selected to evaporate the organic compound from the matrix without completely sintering the material in the pattern. Comprising directing a train of pulses,
The method of claim 1.   The fluence per pulse applied in fixing the pattern causes the organic compound to evaporate through a plurality of holes in the material without causing ablation or delamination of the material due to the evaporation of the organic compound. The method of claim 7, wherein the material is selected to remain sufficiently porous to allow.   The method according to any one of claims 1 to 8, wherein the step of sintering the material comprises applying a bulk sintering process to the pattern fixed on the substrate.   Sintering the material comprises directing a plurality of further pulses of the pulse energy beam to sinter the pattern fixed on the substrate. The method according to item.   9. A method according to any one of the preceding claims, wherein coating the substrate comprises drying the matrix on the substrate prior to irradiation of the coated substrate.   9. The step of removing the matrix comprises the step of contacting the solvent to remove the matrix remaining on the substrate outside the fixed pattern. The method according to item. Coating the substrate with a matrix comprising a material to be patterned on the substrate;
Directing a pulse energy beam having a plurality of pulses including a tilted time profile to impinge on a point on the coated substrate, the pulse energy beam at a point on the coated substrate; Securing the material to the coated substrate and having a fluence sufficient to sinter the material, the method for manufacturing comprising: The matrix has an organic compound in addition to the substance fixed to the substrate,
The tilted time profile and the fluence are selected to evaporate the organic compound from the matrix prior to sintering the material without causing ablation or delamination of the material due to evaporation of the organic compound. ,
The method of claim 13. The substance has a plurality of nanoparticles;
Sintering of the material causes fusion of the plurality of nanoparticles at the point;
The method of claim 13.   14. The method of claim 13, wherein the duration of the pulse is 20 nanoseconds or less.   Directing the pulse energy beam forms the pattern of the material on the substrate by directing the pulse and impinging on a sequence of points defining a pattern on the coated substrate. 17. A method according to any one of claims 13 to 16 comprising steps.   The method of claim 17, wherein the plurality of points in the row do not overlap each other.   The method of claim 17, comprising removing the matrix remaining on the substrate outside of the pattern trajectory after formation of the pattern. A coating apparatus for coating the substrate with a matrix comprising a material to be patterned on the substrate;
Directing a pulsed energy beam to collide with the pattern trajectory in order to adhere the material to the substrate along the pattern without completely sintering the material in the pattern. A drawing device fixed to the matrix;
A matrix removal device for removing the matrix remaining on the substrate outside the fixed pattern;
And a sintering device for sintering the material in the pattern after removal of the matrix.   21. The system of claim 20, wherein the material to be patterned comprises a plurality of nanoparticles.   The substance in the plurality of nanoparticles is electrically conductive, the pulse energy beam has a plurality of radiation pulses, and the energy fluence and repetition frequency of the plurality of radiation pulses are determined by the wiring after the pattern is fixed. 22. The resistivity is selected to remain at least 10 times higher than the final resistivity achieved by full sintering of the material in the pattern after removal of the matrix. The system described in.   21. The system of claim 20, wherein the drawing device directs a train of pulses of the energy beam to collide with each position in the trajectory of the substrate.   21. The system of claim 20, wherein the pulse energy beam has a pulse repetition frequency of at least 1 MHz.   25. The system of claim 24, wherein the pulse repetition frequency is at least 10 MHz. The matrix has an organic compound in addition to the material to be patterned,
The drawing apparatus directs a train of pulses of the energy beam having a fluence per pulse selected to evaporate the organic compound from the matrix without completely sintering the material in the pattern; The system according to claim 20.   The fluence per pulse applied in fixing the pattern evaporates the organic compound through a plurality of holes in the material without causing ablation or delamination of the material due to evaporation of the organic compound. 27. The system of claim 26, wherein the material is selected to remain sufficiently porous to allow it to do so.   The system according to any one of claims 20 to 27, wherein the sintering apparatus applies a bulk sintering process to the pattern fixed on the substrate.   28. A system according to any one of claims 20 to 27, wherein the sintering apparatus applies a further plurality of pulses of the pulsed energy beam to sinter the pattern fixed on the substrate.   28. A system according to any one of claims 20 to 27, comprising a drying device for drying the matrix on the substrate before irradiating the coated substrate.   28. A system according to any one of claims 20 to 27, wherein the matrix removal device contacts a solvent to remove the matrix remaining on the substrate outside the fixed pattern. A coating apparatus for coating the substrate with a matrix comprising a material to be patterned on the substrate;
A pulsed energy beam having a plurality of pulses including an inclined time profile at a fluence sufficient to fix the material to the coated substrate and sinter the material at a point on the coated substrate. And a drawing device that impinges at a point on the coated substrate. The matrix has an organic compound in addition to the substance fixed to the substrate,
The inclined time profile and the fluence are such that the organic compound evaporates from the matrix prior to sintering the material without causing ablation or delamination of the material due to evaporation of the organic compound. Selected,
The system of claim 32. The substance has a plurality of nanoparticles,
When the material is sintered, the plurality of nanoparticles fuse at the point,
The system of claim 32.   The system of claim 32, wherein the duration of the plurality of pulses is 20 nanoseconds or less.   The drawing device directs the plurality of pulses to create a pattern of the substance on the substrate by colliding onto a row of points defining a pattern on the coated substrate; 36. A system according to any one of claims 32 to 35.   40. The system of claim 36, wherein the plurality of points in the column do not overlap each other.   37. The system of claim 36, comprising a matrix removal device that removes the matrix remaining on the substrate outside the pattern trajectory.

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