KR100951778B1 - Method for patterning thin film by laser printing - Google Patents

Abstract

According to the present invention there is provided a thin film patterning method by parallel laser printing. The method comprises providing a glass or plastic source substrate on which a thin film comprising particles is formed and which is light transmissive, wherein the thin film is formed on the source substrate by stacking a solution containing the particles at room temperature. Wherein said particles are present in agglomerated form in said thin film, wherein said source substrate is present in an agglomerated form, and wherein said particles are light transmissive or opposite to or in contact with a thin film formed on said source substrate and opposing said source substrate surface. Arranging a receiver substrate of opaque material and irradiating the source substrate by passing a pulsed laser beam from the pulsed laser beam irradiation means through a spatial light modulator, wherein the spatial light modulator is in any shape desired by the user. The energy density of the pulsed laser beam is formed in a pattern of Modulating and passing the pulsed laser beam through the source substrate and irradiating the thin film of particles to correspond to the pattern; and irradiating the thin film of particles with the pulsed laser beam. In the patterning step of the source substrate, if the energy density of the pulse laser beam irradiated to the particle thin film portion corresponding to the pattern is spatially modulated by the spatial light modulator, the thermoelastic effect of the particles Wherein the force is greater than the bonding force between the particles and the substrate, such that the portion of the thin film of irradiated laser is separated from the substrate such that a pattern corresponding to the pattern of the spatial light modulator is formed in the thin film of particles. Patterning step in parallel and printing step in the receiver substrate, The thin film having a pattern corresponding to the pattern formed on the source substrate by driving the particles separated from the particle thin film toward the receiver substrate by thermoelastic force during the patterning step on the source substrate to be laminated on the receiver substrate And a step of performing a heat treatment on the thin film formed on the receiver substrate and a parallel printing method on the receiver substrate formed on the receiver substrate.

Description

Thin film patterning method by laser printing {METHOD FOR PATTERNING THIN FILM BY LASER PRINTING}

TECHNICAL FIELD The present invention relates to a thin film patterning method, and more particularly to a simple pattern that is periodically repeated on a substrate without requiring a vacuum process and a photoresist layer, as well as any complex form of high resolution desired by a user. The pattern can be easily formed through spatial modulation of the incident beam, the pattern can be formed without being limited by the type of substrate material, and the pulsed laser rather than a serial method of scanning a focused laser beam. It relates to a method for forming a thin film pattern by parallel laser printing using.

Modern electronic devices commonly require metal thin film patterns for electrodes or metallization lines. These metal thin film patterns are typically formed through a photolithography process combined with vacuum deposition of the thin film. Photolithography has the advantage of enabling high resolution patterning, but requires expensive equipment, multi-step processes, high energy consumption, and also involves the discharge of significant amounts of chemical waste by repeated deposition and etching. With the advent of flexible electronic devices, the importance of the large-area patterning process has been raised. Therefore, many researches and developments have been conducted to find an alternative to the conventional photolithography process represented by high cost and high temperature processes. For example, ink-jet printing, soft-lithography, laser-induced forward transfer (LIFT), and the like. All of these methods have the advantage of additive patterning and some have made significant technological advances, but due to their limitations in resolution, reliability, and processing speed, they still do not replace photolithography.

Specifically, a study using lasers for printing thin film patterns was first presented by J. Bohandy et al. After contacting the silicon substrate with the Cu thin film deposited on the glass substrate serving as the source substrate, the excimer pulse laser (λ = 195 nm, pulse width = 15 ns) was focused using a cylindrical lens to irradiate the thin film ( It has been reported that a line pattern of several tens of micrometer width can be formed on a silicon substrate. This method is called laser-induced forward transfer (LIFT). According to the proposed model, the laser pulse heats the interface part of the thin film directly in contact with the glass, and Cu melt is formed at the interface. The interface part has a boiling point until the melt front gradually moves to reach the free surface of the thin film. Cu vapor is formed by heating to the above temperature. The pressure of the vapor causes the melt to transfer to the silicon substrate and condense on it to form a pattern. Subsequent studies using other metal thin films such as Ag, Au, and Al have been published, and traditional LIFTs can be useful for patterning simple materials that can easily evaporate or melt, but without the complex structure or phase transformation of the material itself. It is not suitable when it is necessary to maintain the unique properties of. Tolbert et al. Inserted a thin absorption layer between the material to be transferred and the glass substrate and used the pressure by the evaporation of the absorption layer as the driving force of the transition. This method has the advantage that the material to be transferred does not evaporate or melt, but has the disadvantage of requiring an additional process such as separately absorbing layer between the substrate and the thin film. In another method, a powder-like material is mixed with a polymer binder to form a paste, which is then coated on a glass substrate to form a pattern. In the transition process, the binder mainly absorbs laser energy and selectively evaporates. The remaining binder, which is not completely evaporated during the transfer process, can be removed by additional heat treatment, and since it does not involve melting and condensation of the material to be transferred, there is an advantage of printing a thicker film than the general LIFT. It is also called matrix-assisted pulsed laser evaporation and direct-write (MAPLE; DW), but it is essentially a category of LIFT and requires additional procedures, such as a paste-making process.

LIFT can be applied not only to inorganic materials but also to the transition of polymers and biomaterials, but essentially takes advantage of the evaporation of a particular material or matrix mixed with it by the focusing of the pulsed laser beam. This serial or spot-by-spot method can be useful for the formation of regular and periodic patterns, such as line patterns with constant widths, but there are limitations to the rapid formation of arbitrary patterns of various shapes and sizes. Cross-sectional shape control is also difficult. In order to induce melting or evaporation of the material in the local area, instantaneous energy absorption must be high, so a high power pulse laser is required. The printing speed is closely related to the repetition rate of the laser used. When transferring a droplet to a receiver substrate by a single pulse, the repetition rate must be high, at least a few kHz, because the time interval between the pulses must be very short. Otherwise, the spacing between pulses will be long and the entire patterning process will be time consuming. In a laser with a fixed average power, the repetition rate increases, and the energy of a single pulse is inevitably lowered. There is a minimum pulse energy necessary for printing. This means that in order to increase the printing speed, a higher power laser must be used in proportion. Moreover, thin films, absorbing layers, pastes, etc. coated on the source substrate cannot be reused, resulting in additional processes, costs, etc. in connection with the disposal of materials.

On the other hand, a patterning technique called nanoparticle patterning has been proposed and utilized, which deposits nanoparticles at desired positions or obtains an assembly composed of nanoparticles, which is different from the macroscopic properties of conventional materials. Specificity such as quantum effect of size material, high specific surface area, etc. makes it applicable to quantum devices, single electron transistors, tera-level memory devices, etc. It is a new technology that can be done.

Patterned nanoparticles act as a basic building block for nano devices. To achieve this, the pattern of nanoparticles is controlled to facilitate the periodic patterning of nanoparticles on a substrate by controlling the spatial distribution of nanoparticles. Forming is considered very important.

To date, various nanoparticle patterning methods have been proposed and used, and one of them is a method of directly patterning onto a substrate by photo or e-beam lithography. In addition, a method of inducing deposition or adsorption of nanoparticles on a substrate (ie, a template) on which a pattern is previously formed, a microcontact printing method, a self assembly method, and the like have been used.

While the patterning process for industrial application should not only freely control the shape and period of the pattern, but the process itself should be simple, fast and economical. Due to the complex multi-step process, it requires a lot of cost and time, and the process itself is a relatively simple self-assembly there is a problem that the shape and period control of the pattern is not free.

In addition, as a prior art, the Republic of Korea Patent (Registration No .: 10-687295 (2007.2.20)) is disclosed in the "nanoparticle patterning method", and the Republic of Korea Patent (Registration No .: 10-638091 (October 18, 2006)) "Ananoparticle patterning method and a method for producing a sintered body using the same" are disclosed, and the Republic of Korea Patent Publication (Publication No .: 10-2006-0108202 (October 17, 2006)) discloses the "nanoparticle focused deposition patterning method" have.

However, the technique disclosed in this document is a method of selectively adsorbing charged nanoparticles by applying an electric field to a substrate (a kind of template) on which a photoresist layer pattern is commonly formed, so that separate lithography and etching are performed. There are drawbacks to the complex process requiring etching and electrostatic deposition. Moreover, as a process such as vacuum deposition is performed, it also causes a process inefficiency to be performed at a high temperature.

In addition, a technique for patterning nanoparticles in a holographic manner is also proposed, but this technique, like the conventional nanoparticle patterning technique described above, can implement only a pattern of periodically repeated patterns, and any complex form desired by a user. There are many limitations in implementing the nanoparticle pattern.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and one object thereof is to form a predetermined thin film pattern on a substrate without a photoresist layer required in conventional photolithography. To provide a thin film patterning method using a pulse laser.

Another object of the present invention is to provide a thin film patterning method using a pulse laser that enables low temperature and large area while maintaining high resolution which is an advantage of photolithography in performing thin film patterning.

It is still another object of the present invention to provide a thin film patterning method using a pulse laser capable of forming any pattern desired by a user on a desired substrate without melting / evaporating and condensing the material.

Still another object of the present invention is to provide a thin film patterning method using a pulse laser capable of forming a simple pattern that is periodically repeated, as well as a pattern of any complex shape desired by a user in a simplified process.

Still another object of the present invention is to provide a thin film patterning method using a pulse laser capable of forming such a pattern without being limited to the type of substrate.

Still another object of the present invention is to provide a thin film patterning method using a pulse laser capable of rapidly forming an electrode or a metal pattern for wiring.

Still another object of the present invention is not to provide serial patterning using a focused laser, but to provide a thin film patterning method using a pulse laser capable of forming a desired pattern on a substrate by one laser irradiation. .

In order to achieve the above object, according to the present invention, a thin film comprising particles is formed and provides a transparent glass or plastic source substrate, wherein the thin film is a solution lamination at room temperature Formed on the source substrate, wherein the particles are present in agglomerated form in the thin film, and in contact with the thin film formed on the source substrate opposite the surface of the source substrate on which the thin film is formed. Arranging a receiver substrate of a light transmissive or opaque material in a state or adjacent thereto, and irradiating the source substrate by passing a pulsed laser beam from a pulsed laser beam irradiation means through a spatial light modulator, wherein the spatial light The modulator is formed in a pattern of any shape desired by the user so that the pulse Irradiating the energy density of the edger beam spatially and causing the pulsed laser beam to pass through the source substrate and irradiate the particle thin film corresponding to the pattern; and the particle thin film Patterning at the source substrate by a pulse laser irradiated onto the substrate, wherein the energy density is spatially modulated by the spatial light modulator so that the energy density of the pulse laser beam irradiated onto the particle thin film portion corresponding to the pattern is greater than or equal to a threshold value The force due to the thermoelastic effect of the particles is greater than the bonding force between the particles and the substrate, so that the thin film portion irradiated with the laser is separated from the substrate, so that a pattern corresponding to the pattern of the spatial light modulator is formed in the particle thin film. Parallel patterning in the source substrate; A pattern formed on the source substrate by printing on a burr substrate, wherein the particles separated from the thin film of particles during the patterning on the source substrate are driven toward the receiver substrate by thermoelastic force to be laminated on the receiver substrate. Forming a thin film having a pattern corresponding to the surface of the receiver substrate, the parallel printing method on the receiver substrate, and performing a heat treatment on the thin film formed on the receiver substrate. There is provided a thin film patterning method by printing.

In one embodiment, the particles can be nanometer sized particles or micrometer sized particles.

In one embodiment, the particles can be conductive metal particles of nanometer size or micro size.

In one embodiment, the particles may be nanometer-sized or micrometer-sized semiconductor particles capable of absorbing the pulsed laser or nanometer-sized or micrometer-sized dielectric particles capable of absorbing the pulsed laser. .

In one embodiment, the pulsed laser beam irradiation means may irradiate an Nd: YAG pulsed laser having a pulse width of nanoseconds.

According to the nanoparticle thin film patterning method using the pulse laser according to the present invention, the nanoparticle thin film formed on the substrate is irradiated in a predetermined pattern form without using a photoresist to selectively irradiate particles in the thin film. By removing it, any complex pattern desired by the user can be formed in the nanoparticle thin film.

In addition, according to the present invention, since it does not involve conventional complicated and inexpensive photolithography and etching processes and does not require a process of forming a pattern on a substrate in advance, the process itself is not only very simple but also particles by a single pulse. Has the advantage of allowing fast patterning.

That is, the conventional nanoparticle patterning process requires a template in which a pattern is formed on a substrate in advance, but in the method of the present invention, since the shape and period of the pattern are determined by the spatial distribution of the pulse laser beam intensity, no template is required. The advantage is that the patterning process is very quick and simple.

In addition, according to the present invention, since the metal particle solution is laminated at room temperature on a transparent substrate and a low temperature heat treatment process is performed, the cost can be greatly reduced unlike the prior art.

In addition, since the receiver substrate is not directly exposed to the laser, the receiver substrate can be made of a light transmissive or light impermeable material, unlike the source substrate, and thus can be easily applied to a semiconductor.

Furthermore, according to the present invention, there is no need to transfer the material through melting / evaporation and condensation of the material, so that a laser having a short pulse width of low power can be used, and furthermore, the critical energy density required for the material transfer is LIFT, MAPLE. It is much lower than conventional serial laser printing such as DW, so that no focused laser beam can be used, and any desired thin film pattern can be printed on the substrate over a large area by one laser irradiation. It can be formed.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

A. Subtractive Patterning

FIG. 1 schematically shows the overall configuration of a nanoparticle patterning device capable of carrying out the method of the present invention, showing the formation of a predetermined pattern on a substrate 40 in a subtractive manner. As will be described later, the patterning method of the present invention can be performed based on the apparatus shown in FIG.

First, prior to describing the patterning method according to the present invention, that is, additive patterning method, the basic principles of the present invention that can be used in the present invention will be described.

As shown, the nanoparticle thin film patterning apparatus capable of performing the patterning method of the present invention includes a pulse laser beam irradiation means 10 serving as a pulse laser source, a beam expander 20, and a spatial light modulator. and a light transmissive substrate 40 on which the nanoparticle thin film 50 is formed.

The beam expander 20 is provided to enlarge the irradiation area of the pulse laser emitted from the irradiation means according to the embodiment, and may not be provided when the pulse laser is configured to emit over a large area from the irradiation means. have.

The spatial light modulator 30 serves as a photo mask, and as described below, the light modulator includes a predetermined pattern corresponding to the pattern to form a desired pattern on the nanoparticle thin film 50. P) is formed, and a pulse laser beam passes through the pattern P, and is irradiated to the substrate 40.

First, a process of performing patterning on the light transmissive substrate 40 in a subtractive manner using the device configured as described above will be described.

First, the light transmissive substrate 40 on which the nanoparticle thin film 50 is formed is provided. Next, the irradiation means 10 emits a pulse laser (Nd: YAG pulse laser according to the preferred embodiment) toward the substrate.

The pulse laser is extended to the range that can be irradiated to the substrate while passing through the beam expander 20.

Subsequently, a pulsed laser having an enlarged irradiation area passes through the spatial light modulator 30, which is pre-formed with a pattern P desired by the user, so that the pulsed laser passes through the light modulator through the corresponding pattern. Done. The pulsed laser beam passing through the pattern P reaches the rear surface of the light transmissive substrate 40 and then passes through the substrate to reach the nanoparticle thin film 50 formed on the opposite surface. The pulse laser is irradiated onto the thin film in a form corresponding to the pattern P, and the thin film 50 is formed into a pattern P 'corresponding to the pattern P, and finally, a pattern desired by the user on the thin film of the substrate. Is formed.

The mechanism of forming a pattern desired by the user on the thin film will be described in more detail as follows.

Thin film of nanoparticles (according to one example of the present invention, a commercial Ag nanoparticle solution having an average size of 25 nm is formed on a substrate by low temperature solution lamination, and this low temperature solution lamination technique itself is a well-known technique, When the pulsed laser is incident on the nanoparticles, the nanoparticles in the thin film retain the thermo-elastic force due to the rapid temperature rise and the resulting thermal expansion due to the laser energy absorption. It acts as a force away from the surface. As a result, when the thermoelastic force is greater than the adhesive force between the nanoparticles and the substrate surface (mostly due to the van der Walls force), the nanoparticles are separated from the substrate surface, and this phenomenon is laser-induced thermal deviation. Thermal desorption (LITD).

That is, since the thermoelastic force is proportional to the temperature rise rate of the nanoparticles, the thermoelastic force possessed by the nanoparticles under laser irradiation with a fixed pulse width is proportional to the pulse energy density (J / cm 2). When the pulse energy density at a specific position is above the threshold energy density, the nanoparticles in the portion are separated from the substrate surface, and the thermoelastic force at the critical energy density is In the same manner as the adhesion force, if the energy density of the pulsed laser beam is spatially modulated and incident on the nanoparticle thin film uniformly formed on the substrate, the nanoparticle pattern can be obtained according to the modulation pattern.

This mechanism is described below with reference to the results of the two beam interference experiments of FIG. 2. When the annealed thin film is placed in a sinusoidal interference profile, the ultimately patterned area initially cracks vertically (see A in FIG. 2). The cracked nanoparticle blocks are then removed in the course of increasing the pulse energy, with B and C in FIG. 2 showing the expected patterning mechanism.

As shown, the critical energy density (denoted “threshold” in B of FIG. 2) for desorption of the multilayered thin film is greater than the critical energy density (denoted “monolayer threhold”) for the single layer thin film. If the energy density of the interference pattern is between these two levels, upward force is exerted on the nanoparticles in contact with the substrate, and this non-uniform force causes vertical cracks in the thin film. As the peak energy density exceeds the threshold, some nanoparticle blocks in the cracked region begin to fall (see top C of FIG. 2). Once the initially cracked areas are completely removed, an additional increase in pulse energy reduces the line width of the pattern, as the areas exposed beyond the critical energy density become wider (see bottom C in FIG. 2).

In one embodiment, the present inventors utilize various solution deposition techniques such as spin coating, drop coating and dip coating on a light transmissive substrate (glass or plastic). Ag nanoparticle thin films were laminated at room temperature with a thickness ranging from 100 nm to 1 μm. After the annealing heat treatment was performed at a temperature of less than 450 ° C. at atmospheric pressure, the Ag thin film was patterned with Nd: YAG. Pulse laser (λ = 1064 nm, pulse width = 6 ns, pulse repetition rate = 10 Hz, maximum average power = 8.5 W). Examples of patterns formed through this process are shown in FIG. 3.

In FIG. 3, A is a photographic image of a "mona lisa" patterned on a glass substrate, wherein a black and white "mona lisa" painting printed on a transparent plastic sheet (polyester) by a desktop computer was used as the photo mask. 3B is one example of a pattern formed on a transparent plastic sheet using a conventional glass photomask, and C and D of FIG. 3 are scanning electron microscopes of patterns fabricated on glass and polyimide substrates, respectively. (SEM) image. As described above, according to the present invention, not only a simple pattern that is periodically repeated, but also any complicated form desired by a user can be easily formed without a photoresist.

The direct laser patterning scheme described herein can be extended to nonmetal materials, such as semiconductors and dielectrics, once the material absorbs the laser wavelength. In addition, since the particles of the thin film formed on the substrate are entangled with each other, the size of the particles is not limited so long as the mechanism of the present invention can be applied. That is, the size of the particles of the thin film does not necessarily have to be nano size, and the present invention can be applied to the case of forming a thin film using a solution composed of larger micro particles. Of course, the thermoelastic force that the particles receive depends on the type and size of the particles, so that the wavelength and pulse width of the appropriate laser may vary accordingly.

In addition, the principle that is clearly distinguished from the conventional LIFT method is that the thermoelastic force, not the vapor pressure of the material, is used as the driving force for the release of the material and the transition of the material, which will be described later, and the parallel process (not the series method of scanning the focused laser beam) Predetermined printing is performed using a parallel process, which will be described in more detail below.

B. Additive Patterning (Printing)

As described above, by irradiating a thin film formed on the transparent substrate with a laser to selectively remove particles by thermoelastic force, it was confirmed that a pattern having a desired shape can be formed on the thin film.

However, the present inventors continued to study the patterning method applying this principle, and thus expanded the patterning method to complete a more efficient patterning method.

That is, the patterning method described above is basically a subtractive patterning method in which predetermined portions of the thin film are selectively removed by the laser beam passing through the optical modulator 30 to form a pattern. According to this method, a part of the thin film is inevitably subtractive, and it may cause a problem of resource utilization of the separated thin film and some inefficiencies related to the cost associated with the thin film, which is a fundamental problem of the subtractive patterning method. It is also a problem.

In addition, as described above, since the laser beam is incident from the back surface of the substrate and enters the thin film laminated on the opposite surface, a limitation arises in that the substrate must be made of a light transmissive material. However, since the electronic device substrate is mostly made of an opaque material such as silicon, there are many restrictions in applying the above patterning method to the manufacture of a typical semiconductor substrate.

Accordingly, the present inventors have expanded the patterning method as described above, and have studied a method capable of recycling thin film materials and forming a pattern of a predetermined pattern on any substrate, regardless of the material constituting the substrate. The results of this study are shown in FIG. 4.

That is, FIG. 4 schematically illustrates a mechanism capable of forming a pattern of a predetermined pattern on an arbitrary substrate according to the present invention. Unlike shown in FIG. 1, according to the present embodiment, patterning is performed on the receiver substrate 60 in an additive manner. That is, in the source substrate 40, a pattern of a predetermined shape is formed in the thin film in a subtractive manner according to the mechanism shown in FIG. 1, and on the receiver substrate 60, as described below, an additive method, that is, printing is prescribed. When the pattern of the shape is formed, it will be described below except for the portion overlapping with FIG.

First, the source substrate 40 corresponds to the light transmissive substrate 40 of FIG. 1, and according to the mechanism described with reference to FIG. 1, a pattern having a shape desired by a user is formed on the source substrate 40.

On the other hand, unlike the one shown in Fig. 1, according to this method, the receiver substrate 60 is attached to the source substrate 40 side on which the thin film is formed (in Fig. 4, the receiver substrate and the source substrate are separated by a considerable distance. Although illustrated as being illustrated for convenience of description, the receiver substrate 60 is in contact with the source substrate 40, or is almost in contact with the source substrate 40 even if not in contact. 40).

Subsequently, the laser beam is irradiated to the back surface of the source substrate 40 through the photo mask 30 in the same manner as shown in FIG. 1. As a result, the pattern corresponding to the pattern P of the predetermined shape formed in the photomask 30 is formed in the source substrate 40 according to the mechanism as shown in FIG. On the other hand, the receiver substrate 60 is disposed in contact or almost in contact with the source substrate 40, so that the nanoparticles of the thin film removed by the laser beam passing through the photomask are moved toward the receiver substrate 60, thereby receiving the receiver. The thin film 70 having a pattern P ″ having a predetermined shape is formed on the substrate 60.

That is, according to the present invention, in addition to forming a predetermined pattern of thin films on the thin film of the source substrate 40, a pattern corresponding to the pattern formed on the source substrate on a separate receiver substrate 60 using the same mechanism A thin film having a film is formed by a printing method.

In this case, unlike the source substrate, since the laser beam does not need to pass through the receiver substrate, that is, the receiver substrate is not directly exposed to the laser, so there is no limitation in the material of the receiver substrate. That is, as described above, when the thin film having a predetermined pattern is formed on the source substrate 40, since the laser is incident from the back surface opposite to the surface on which the thin film is formed, the nanoparticles of the thin film are separated. It must consist of a material that can pass through, such as light-transmissive glass or plastic.

Therefore, there is a limitation in the material of the source substrate that can form a thin film having a predetermined shape pattern, it is difficult to perform the patterning by using the same method for the material such as silicon which is most used in the semiconductor industry The problem is that it can be difficult.

However, instead of forming a thin film only on the source substrate, when the receiver substrate is placed to form a thin film of a predetermined pattern by using nanoparticles separated from the thin film of the source substrate, the receiver substrate is directly like a laser. Since there is no need for exposure to light, there is no particular limitation on the material of the receiver substrate, and patterning is performed in the above manner on a substrate made of any material (light transmissive material, light impermeable material, etc.) such as silicon, glass, plastic, or the like. By doing this, a thin film having a pattern of a predetermined shape can be printed.

On the other hand, as described above, in the present invention, the thermoelastic force is used as the driving force for transition of the material. That is, when the energy is irradiated onto the substrate according to the above process and the pulse energy density at a specific position is greater than or equal to the critical energy density, the thin film of the portion is selectively transferred to the receiver substrate, thus spatially changing the energy density of the laser beam. When modulated and incident, a thin film pattern according to the modulation pattern can be obtained. Thermoelasticity depends on the rate of temperature rise, how fast it rises, and is independent of the absolute value of the temperature rise. Therefore, lasers with short pulse widths, such as nanosecond pulsed lasers, can be separated from the substrate without melting the thin film, and the threshold pulse energy density required for material transfer is very low compared to that of LIFT. There is no need to use. This laser printing method is expected to achieve relatively high resolution as the spatial modulation of light is performed in the same way as conventional lithography, and to enable low-temperature and large-area patterning when combined with solution deposition of thin films. In addition, compared to conventional serial printing such as inkjet printing, LIFT, it is possible to obtain a desired pattern at a time by irradiating the laser in parallel rather than focused. In addition, much higher throughput can be expected compared to conventional printing such as inkjet printing, LIFT, and the like.

In one embodiment, the inventors have evaporated a silver thin film having a thickness of 120 nm to 1 μm onto a glass source substrate using Ag nano-ink (ABC NANOTECH, Inc.) having an average particle diameter of 25 nm and then at room temperature. It dried (low temperature lamination process). Prior to lamination, the ink was diluted with acetone to reduce the time required to dry the laminated thin film and to facilitate thickness control. Subsequently, the spatial light modulator (Nd: YAG pulse laser beam (λ = 1.064 mu m, pulse width = 6 ns, repetition rate = 10 Hz, maximum average power = 8.5 W, output beam diameter = 0.9 cm) was brought into contact with the back surface of the source substrate ( 30) was used to spatially modulate the energy density and enter the thin film. FIG. 5 is optical profiler images obtained by scanning a source substrate and a receiver substrate after a single pulse has been incident. These images clearly show that the material deviating from the source substrate has transferred to the receiver substrate. An encouraging feature of the present invention is that the dried Ag thin film remaining on the source substrate can be reused by dissolving it in an organic solvent such as acetone or re-depositing the thin film in solution thereon. In the latter case, the dried thin film is melted into the newly deposited solution thin film to form a new homogeneous thin film. Therefore, it is possible to solve the disposal of the remaining material and related problems unlike the prior art.

As such, the conventional LIFT and MAPLE-DW schemes are based on vapor pressure due to evaporation of the material, while the present invention utilizes thermoelastic driving forces. Given the very short penetration depth of the near infrared into the metal, the incident laser energy will most likely be absorbed by the particles adjacent to the source substrate. The thermoelastic force that separates these particles from the substrate is expected to repel other particles on the particles (see above). Since the solution-laminated nanoparticle thin film has a weak cohesion, the thermoelastic force may easily shear a portion of the thin film from the thin film remaining on the source substrate and propel it toward the receiver substrate. The thermoelastic force is proportional to the rate of temperature rise, not the absolute value of the temperature rise. This means that particles can be desorbed if the pulse width is short even if the total pulse energy is not so high. The critical pulse energy density for printing was measured to be slightly less than 0.1 J / cm ² , with little effect on the thickness of the thin film. After expanding the output laser beam, we were able to print the pattern over several cm ² using a single pulse with an energy of 850 mJ. Under industrial Nd: YAG lasers with peak outputs up to several kW, wafer-scale patterning will be possible with a single pulse. In this process, the receiver substrate is not directly exposed to the incident laser. This means that patterns can be printed on a wide variety of solid substrates, such as silicon, glass and plastic, without damaging the surface.

On the other hand, the present inventors have concluded that annealing should be performed in order for the formed thin film to have appropriate conductivity and / or mechanical adhesion. In this regard, the inventors have found that when applying the method of the present invention to form a thin film of a predetermined pattern on the receiver substrate, it is preferable to perform annealing after printing. Transfer of the material was also possible with an annealed film, but in this case the printed pattern had very poor adhesion to the receiver substrate. Specifically, the nano-inks contain some organic additives or other materials, such as stabilizers, which fill the spaces between the nanoparticles. These organic components also appear to be heated by direct absorption from the laser light or by heat conduction from the heated Ag particles, acting as a kind of adhesive. However, prior to performing the patterning of the present invention, when the heat treatment is performed on the source substrate on which the thin film is formed (annealed), the organic material serving as the adhesive is removed during the heat treatment process, even if transferred to the receiver substrate. The adhesion seems to be poor.

In this regard, the present inventors used a glass having a thickness of about 100 μm as a source substrate, and obtained a printed pattern on a scale of 10 μm or less (see FIG. 6). In the case of the contact mode method of directly contacting the photo mask with the source substrate, the thinner the source substrate, the finer the pattern can be printed. In order to have a resolution that reaches the diffraction limit of light, You will need printing. The printed film was annealed for about 30 minutes in air, the film remained almost nonconducting up to T = 125 ° C., but after annealing at about 150 ° C., the resistance was 10 ⁻² to 10 ⁻³ Ω · cm. Fell sharply. This indicates that the thin film can be cured around about 150 ° C. with all organic components removed. Increasing the annealing temperature further lowered the resistance until nearly saturated above 225 ° C. The minimum resistance obtained was three to five times greater than the Ag bulk resistance of 2.25 × 10 ⁻⁶ Ω · cm.

In addition, to examine whether the present invention can be applied to forming metal wiring for electronic devices using the process according to the present invention, a pentacene thin film transistor using a printed source electrode and a drain electrode (TFT) was prepared. A heavily doped p-type Si wafer was used as the gate electrode and a thermally grown SiO ₂ layer (200 nm thick) was used as the gate dielectric. After printing the source electrode and the drain electrode, a 60 nm-thick pentacin semiconductor layer was laminated by thermal evaporation. The device has a channel length of L = 17 μm and a channel width of W = 340 μm. FIG. 7A shows the relationship between the drain voltage V _D and the drain current I _D measured at various gate voltages V _G , which shows typical TFT characteristics. 7B shows the I _D vs. V _G plot for the same device biased in the saturated operating region (V _D = -40 V). The ON / OFF ratio of the current was about 10 ⁵ , and the calculated mobility was 2.7 × 10 ⁻² cm ² V ⁻¹ s ⁻¹ . These values are comparable with those reported for typical pentacin TFTs with vacuum deposited metal electrodes. This indicates that the process described in the present invention may be an alternative to the conventional metal wiring technique.

In conclusion, we have demonstrated a parallel laser printing process for metallization, based on the laser-induced thermoelasticity of nanoparticles. Printed nanostructured thin film pattern on various substrates such as silicon, glass and plastic by spatially modulated Nd: YAG pulsed laser beam (λ = 1064 nm, pulse width = 6 ns, maximum average power = 8.5W) It was. A pattern of high fidelity on a scale of 10 μm or less could be printed over several cm ² by a single pulse with an energy of 850 mJ. We have also shown that printed thin film transistors can be fabricated using source and drain electrodes. Such parallel laser printing combined with solution stacking provides simple and cost effective metallization for electronic devices and can be extended to other material systems.

As mentioned above, although preferred embodiment of this invention was described with reference to drawings, it should be noted that this invention is not limited to this embodiment. That is, the present invention may be variously modified and modified within the scope of the present invention described below, and all of them fall within the scope of the present invention.

As mentioned above, although preferred embodiment of this invention was described with reference to drawings, it should be noted that this invention is not limited to this embodiment. That is, the present invention may be variously modified and modified within the scope of the present invention described below, and all of them fall within the scope of the present invention.

1 is a view schematically showing an overall configuration of an apparatus for performing a patterning method using a pulse laser according to an aspect of the present invention.

2 shows the mechanism of the method of the invention.

3 is a diagram showing examples of complex patterns of various shapes formed on a nanoparticle thin film according to the present invention.

4 is a diagram schematically showing the overall configuration of an apparatus for performing a parallel printing method using a pulse laser, according to an aspect of the present invention.

5 is a view showing an optical profiler image of the source substrate and the receiver substrate measured after printing.

6 is a scanning electron microscope (SEM) photograph of a printed silver (Ag) thin film pattern.

FIG. 7 shows the characteristics of a pentacin TFT fabricated using printed Ag source and drain electrodes (channel length of L = 17 μm and channel width of W = 340 μm), where A in FIG. I _D ) is shown the relationship between the drain voltage (V _D ), B of Figure 7 shows the relationship between the drain current (I _D ) and the gate voltage (V _G ).

Claims (11)

delete delete delete delete delete delete Providing a glass or plastic source substrate having a thin film formed thereon, wherein the film is transparent, wherein the thin film is formed on the source substrate by lamination of a solution containing the particles at room temperature; Providing the source substrate, wherein the particles are present in agglomerated form in the thin film; Disposing a receiver substrate of a light transmissive or opaque material opposite or in contact with a surface of the source substrate on which the thin film is formed; Irradiating the source substrate by passing a pulsed laser beam from the pulsed laser beam irradiation means through a spatial light modulator, wherein the spatial light modulator is formed in a pattern of any shape desired by a user to generate energy of the pulsed laser beam. The pulsed laser beam irradiation step of spatially modulating the density and allowing the pulsed laser beam to pass through the source substrate and irradiate the particle thin film corresponding to the pattern; Patterning in the source substrate by the pulse laser irradiated to the particle thin film, the energy density is spatially modulated by the spatial light modulator so that the energy density of the pulse laser irradiated to the portion of the particle thin film corresponding to the pattern is critical If the value is greater than or equal to the value, the force due to the thermoelastic effect of the particles is greater than the bonding force between the particles and the substrate, and the portion of the particle thin film irradiated with the laser is separated from the substrate, so that the pattern corresponding to the pattern of the spatial light modulator is a particle thin film. Parallel patterning at the source substrate, wherein the patterning layer is formed at the source substrate; A printing step on the receiver substrate, wherein the particles separated from the particle thin film during the patterning step on the source substrate are driven onto the receiver substrate by thermoelastic force to be laminated on the receiver substrate, thereby forming Forming a thin film having a pattern corresponding to the pattern on the receiver substrate; Performing heat treatment on the thin film formed on the receiver substrate Thin film patterning method by parallel laser printing comprising a. The method of claim 7, wherein the particles are nanometer sized particles or micrometer sized particles. The method of claim 8, wherein the particles are nanometer-sized or micro-sized conductive metal particles. The parallel type of claim 8, wherein the particles are nanometer-sized or micrometer-sized semiconductor particles capable of absorbing the pulsed laser, or nanometer-sized or micrometer-sized dielectric particles capable of absorbing the pulsed laser. Thin film patterning method by laser printing. 8. The method of claim 7, wherein the pulsed laser beam irradiation means irradiates an Nd: YAG pulse laser having a pulse width of nanoseconds.

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