TW201931963A - Method and system for fabrication of an electrical device - Google Patents

Abstract

A method for fabrication of an electrical device includes identifying a locus on a circuit substrate on which a resistor having a specified resistance is to be formed between first and second endpoints of the locus. A transparent donor substrate, having opposing first and second surfaces and a donor film comprising a resistive material formed over the second surface, is positioned in proximity to the identified locus on the circuit substrate, with the second surface facing toward the circuit substrate. Pulses of laser radiation are directed to impinge on the donor film so as to induce ejection of droplets of the resistive material from the donor film onto the circuit substrate at respective, neighboring locations along the locus with a separation between the neighboring locations selected so as to form a circuit trace having the specified resistance between the first and second endpoints.

Description

Method and system for making electronic device

[Cross Reference of Related Applications]

This application claims the right to US Provisional Patent Application No. 62 / 615,982, filed on January 11, 2018, which is incorporated herein by reference.

The present invention relates generally to laser-induced material transfer, and more particularly, to printing electronic components on a substrate by laser-induced forward transfer (LIFT).

In laser direct-write (LDW) technology, a laser beam is used to form a patterned surface with a spatially resolved three-dimensional structure by controlled material ablation or deposition. Laser-induced forward transfer (LIFT) is a laser direct writing technique that can be applied to deposit micropatterns on a surface.

In laser-induced forward transfer, laser photons provide a driving force to project a small volume of material from a donor film toward an acceptor substrate. Generally, a laser beam interacts with the inside of a donor film that is applied to a non-absorbent carrier substrate. In other words, the photons are absorbed by the inner surface of the film after the incident laser beam has propagated through the transparent carrier. Above a certain energy threshold, the material is sprayed from the donor film towards the surface of the substrate. In laser-induced forward transfer systems known in the art, the substrate is usually placed in close proximity or even in contact with the donor film. The applied laser energy can be varied to control the forward thrust before generating within the volume of the irradiated film.

Laser-induced forward transfer techniques using metal donor films have been developed for a variety of applications, such as electronic circuit repair. For example, PCT International Publication No. WO 2010/100635 (the disclosure of which is incorporated herein by reference) describes a system and method for repairing electronic circuits in which a laser is used to pre-process a circuit substrate One of the previous conductors is a conductor repair area. A laser beam is applied to a donor substrate in one of the following ways: a portion of the donor substrate is detached from the donor substrate and transferred to a predetermined conductor position.

As another example, PCT International Publication No. WO 2015/181810 (the disclosure of which is incorporated herein by reference) describes a material deposition method that includes defining a substrate to be formed on a printed circuit board and printing the substrate with the printed substrate. A conductive trace on the circuit substrate contacts a locus of an embedded resistor and a resistor. A transparent donor substrate is positioned close to the printed circuit substrate. The transparent donor substrate has a first surface and a second surface opposite to each other, and a donor film formed on the second surface. The donor film includes a metal. , Wherein the second surface faces the printed circuit board. Guide the pulse of laser radiation through the first surface of the donor substrate and irradiate the donor film to induce droplets of molten material (the droplets will form metal particles on the printed circuit substrate) Spray from a donor film while scanning a pulse wave to fill the trajectory with an aggregate of particles, the aggregate providing a defined resistance between conductive traces that contact the aggregate.

The embodiments of the present invention described below provide a novel method and system for making circuit components on a substrate based on laser-induced forward transfer, and circuit components produced by such methods.

Therefore, according to an embodiment of the present invention, a method for manufacturing an electronic device is provided. The method includes identifying a track on a circuit substrate, and a resistor having a specified resistance is formed between a first end point and a second end point of the track on the circuit substrate. A transparent donor substrate is positioned near the track identified on the circuit substrate. The transparent donor substrate has a first surface and a second surface opposite to each other, and is formed on the second surface. A donor film comprising a resistive material, wherein the second surface faces the circuit substrate. A pulse of laser radiation is guided through the first surface of the donor substrate and irradiated on the donor film to induce droplets of the resistive material to be ejected from the donor film onto the circuit substrate along the circuit board. At the corresponding adjacent positions of the trajectory, a separation between the adjacent positions is selected to form a circuit trace having the specified resistance between the first endpoint and the second endpoint ( circuit trace).

In a disclosed embodiment, the interval is selected to control a size of a contact area between the droplets at the adjacent positions, the size determining the resistance of the circuit trace. Alternatively or additionally, guiding the pulses includes adjusting an energy level of the pulses to control one or more physical properties of the droplets, the one or more physical properties determining the circuit trace Its resistance.

In some embodiments, identifying the trace includes identifying a gap between a plurality of conductors on the circuit substrate, and the pulse waves guiding the laser radiation are included in the gap to form the circuit trace. In one embodiment, identifying the gap includes measuring the gap and forming the circuit trace in response to the measuring. In one embodiment, forming the trace includes setting the interval between the adjacent positions onto which the droplets are ejected in response to the measurement, so that the circuit trace will have the specified resistance. In another embodiment, forming the circuit trace includes adjusting one or more physical properties of the droplets by setting an energy of the pulse wave in response to the measurement, so that the circuit trace will With this specified resistance. Performing the measurement may include capturing and processing an image of the circuit substrate to identify and measure the gap.

Additionally or alternatively, the method includes forming a trench along the trajectory in the circuit substrate before the ejection of the droplets, wherein the pulses that guide the laser radiation include a The droplets are injected into the trench. In a disclosed embodiment, the trench has a width smaller than an average diameter of one of the droplets.

Still further or alternatively, the method includes annealing the circuit trace.

In some embodiments, guiding the pulse waves includes setting an energy and a focal size of the pulse waves of the laser radiation irradiated on the donor membrane, so that the pulse waves are Each pulse wave induces a single droplet of the resistive material from the jet of the donor film. In one embodiment, the energy of the pulse waves is set to a first value to induce the ejection of the single droplet per pulse wave, and the method includes: after forming the circuit trace, at a rate greater than the first The second energy value directs other pulses of the laser radiation to irradiate the donor film, so that a spray layer formed of small particles of the resistive material is sprayed and superposed on the donor film. Covered on one end of the circuit trace.

In a disclosed embodiment, guiding the pulse waves includes guiding multiple pulse waves of the laser radiation to simultaneously irradiate at different corresponding points on the donor film to make a plurality of resistors in parallel on the circuit substrate Sex circuit trace. Additionally or alternatively, guiding the pulse waves includes scanning the pulse waves to form the circuit trace in a meander pattern between the first endpoint and the second endpoint.

In addition or as an alternative, guiding the pulse waves includes using an acoustic-optic deflector to scan the pulse waves on the donor substrate and measuring the intensity of one of the pulse waves. And in response to the measured intensity, the acousto-optic deflector is controlled to compensate for the fluctuation of one of the pulse waves radiating on the donor substrate.

According to an embodiment of the present invention, a system for manufacturing an electronic device is also provided. The system includes a transparent donor substrate having a first surface and a second surface opposite to each other, and a donor film formed on the second surface. The donor film includes a resistive material. . A positioning assembly is used for positioning the donor substrate near a track on a circuit substrate. On the circuit substrate, a specified resistance will be formed between a first end point and a second end point of the track. A resistor, wherein the second surface of the donor substrate faces the circuit substrate. An optical assembly is used to guide the pulse of laser radiation through the first surface of the donor substrate and irradiate the donor film to induce droplets of the resistive material to be ejected from the donor film to the donor film. Corresponding adjacent positions along the track on the circuit substrate, wherein an interval between the adjacent positions is selected to form a circuit having the specified resistance between the first terminal and the second terminal. Trace.

Overview

The embodiments of the invention described herein provide a method and system for laser-induced forward transfer printing of resistors with small size and fine precision. The disclosed method enables the fabrication of embedded resistors on circuit substrates at a higher density than techniques known in the art, while maintaining sufficient accuracy for most commercial applications.

In the embodiment described below, an embedded resistor with a specified resistance is made between a pair of terminals (such as a pair of conductive terminals) on a substrate in a certain track on a circuit substrate. To make a resistor, a transparent donor substrate is positioned close to a circuit substrate on which a track of a resistor is to be printed. The transparent donor substrate has a donor film formed on one of its surfaces. The donor film includes a A resistive material, wherein the donor film faces the circuit substrate. A laser guides the pulse of radiation through the donor substrate and irradiates the donor film to induce droplets of the resistive material to be ejected from the donor film onto the circuit substrate. The position of the laser beam and the substrate are controlled such that the droplets are successively deposited along the trajectory at corresponding adjacent positions.

The resistance of the embedded resistor is controlled by setting the separation between the droplet positions to a selected value. In general, the resistivity of a trace formed by a droplet increases as the interval between the droplet locations increases. More specifically, the interval is selected to control the size of the contact area between adjacent droplets, which in turn determines the resistivity of the circuit trace.

In some embodiments, before the droplets are ejected, a trench is formed in the circuit substrate along the track of the resistor, and the pulse of laser radiation causes the droplets to be injected into the trench. The inventors have found that the use of such trenches that can be smaller in width than the average diameter of one of the droplets helps to precisely control the width and resistivity of the resistive trace. Additionally or alternatively, after laser-induced forward transfer printing, the resistive traces may be annealed (for example, by heat treatment using a laser beam) to trim and / or stabilize the resistance to Desired value.

systems mannual

FIG. 1 is a schematic side view of a system 20 for laser-induced forward transfer-based material deposition of an embedded resistor on a receiver substrate 22 according to an embodiment of the present invention. The system 20 includes an optical assembly 24. In the optical assembly 24, a laser 26 emits pulse wave radiation, which is focused by suitable optics 30 onto a laser-induced forward transfer donor sheet 32 . A scanner 28 (eg, a rotating mirror and / or an acoustic-optic beam deflector) scans the laser beam onto the donor sheet 32 under the control of a control unit 40 Different spots are irradiated. Therefore, the control unit 40 controls the optical assembly 24 to write the donor material on a predefined trajectory on the substrate 22, wherein the distance between adjacent droplets is controlled according to the required resistance. In the illustrated example, the track in which the resistor is deposited includes a trench 46 in the substrate 22, and the trench 46 is formed in a gap in a conductive trace 44 on the substrate 22.

The laser 26 may, for example, include a pulse wave Nd: YAG laser with a frequency-doubled output, which allows the pulse wave amplitude to be easily controlled by the control unit 40. In general, to achieve good laser-induced forward transfer deposition results, as described below, pulse durations are in the range of 0.1 nanoseconds (ns) to 1 nanosecond, with pulse energy in the range of 0.5 microjoules (µJ) to In the range of 40 microjoules. The optical device 30 is similarly controllable to adjust the size of a focal spot formed by the laser beam on the donor sheet 32, wherein the spot size is in a range between 5 microns (µm) and 500 microns in. The above laser pulse wave characteristics are presented by way of example, and as another option, depending on the application requirements, other types of lasers with different pulse wave energy and spot size can be used.

The substrate 22 typically includes a dielectric material having a conductive structure (such as a printed electronic circuit) printed on it including the traces 44. The substrate 22 may be rigid or flexible. Therefore, the substrate 22 may include, for example, a laminated epoxy resin sheet or ceramic sheet, or a flexible circuit substrate as known in the art. Alternatively, the system 20 can be used to print embedded resistors on other kinds of substrates, such as glass, thermoplastics, thermosetting materials, and other polymers and organic materials, and even paper-based materials.

The donor sheet 32 includes a donor substrate 34. A donor film 36 is formed on a surface of the donor substrate 34 facing the acceptor substrate 22. The donor substrate 34 includes a transparent optical material (such as a glass sheet or a plastic sheet), and the donor film 36 includes a suitable resistive material (such as a Ni _x Cr _1-x alloy), where x is, for example, 0.3 To 0.7. Generally, the thickness of the donor film 36 is between 0.1 μm and 3 μm. Alternatively, other resistive compounds such as CrSiN, CrSi, AlO ₂ , or NiCrAl may be used in the donor film 36. In addition, as an alternative, after reading this description, those skilled in the art will understand other suitable compounds that can be used in laser-induced forward transfer based fabrication of embedded resistors, and these other suitable compounds Compounds are considered to be within the scope of this invention.

The control unit 40 causes a movement assembly 38 to displace the acceptor substrate 22 or the optical assembly 24 or both so that the light beam from the laser 26 and the acceptor substrate will cause the material from the donor film 36 to be removed. The track written to is aligned. The donor sheet 32 is positioned close to the acceptor substrate 22 above the track to a desired gap width from the acceptor substrate. Generally, this gap width is at least 0.1 millimeters (mm) or possibly greater, depending on the proper selection of the laser beam parameters. The optical device 30 focuses the laser beam to pass through the outer surface of the donor substrate 34 and irradiates the donor film 36, so that droplets of molten metal are ejected from the film across the gap to the acceptor substrate 22. The laser-induced forward transfer process will be described in more detail below with reference to FIG. 2.

In order to support the accurate deposition of droplets in the gaps in the traces 44 on the substrate 22, the system 20 in this embodiment includes a camera 42, which is aligned with the optical assembly 24 to capture the An electronic image of the substrate 22. Generally, the camera 42 includes a high-resolution image sensor with one of the high-magnification optics to enable the control unit 40 to accurately measure the length of the gap in the trace 44 where the resistor is to be deposited. Alternatively or additionally, the control unit 40 may use a-priori information such as computer-aided manufacturing (CAM) data to determine the length of the gap. The control unit 40 uses the actual gap size and / or the prior gap size to adjust the resistor deposition parameters (such as the distance between adjacent droplets) to ensure that the embedded resistor will have the required resistance. These adjustments are explained further below.

Generally, the control unit 40 includes a general-purpose computer having a suitable interface to control the optical assembly 24, the motion assembly 38, and other components of the system 20 The component receives feedback. The system 20 may include additional components (omitted from the figure for simplicity), such as an operator terminal, which can be used by an operator to set the functions of the system and other pre-processing and post-processing stations. These and other auxiliary components of the system 20 will be apparent to those skilled in the art and will not be repeated in this description for the sake of brevity.

The following describes some of the pre-processing steps and post-processing steps involved in generating embedded resistors. Several of these steps involve applying laser radiation to the substrate 22 and / or a structure formed on the substrate. These steps may be performed by laser 26 and optical assembly 24 with operating parameters different from those used in the laser-induced forward transfer deposition process, or as an alternative, these steps may be performed at It is implemented in other laser-based processing stations which are omitted from the figure for the sake of simplicity.

FIG. 2 is a schematic cross-sectional view of a trace on which an embedded resistor is deposited on the substrate 22 according to an embodiment of the present invention, showing a metal droplet 54 from the donor film 36 to the thunder in the trench 46 Shot-induced forward transfer-driven spray. This figure illustrates the effect of irradiating film 36 with a pulsed laser beam 50, where the pulse duration is equivalent to the time required for thermal diffusion through the film, as described in the PCT application mentioned above . This choice of laser pulse parameters causes a "volcano" pattern 52 in the donor membrane. Each laser pulse in this "volcano-jetting" state causes a single droplet 54 to be emitted with high directivity (usually within about 5 milliradians (mrad) from the normal of the membrane surface). The size of the droplets can be controlled by adjusting the energy of the laser beam 50, the duration of the pulse wave, the focal spot size of the laser beam 50 on the donor film 36, and the thickness of the donor film. Depending on these parameter settings, the volume of the droplet 54 can usually be adjusted in the range of 10 femtoliter to 100 femtoliter.

As another option, the laser pulse energy and other operating parameters can be adjusted so that each laser pulse causes multiple droplets to be emitted from the donor film 36, and it is possible that the "spray regim" )"run.

When the laser fluence exceeds a given threshold, laser-induced forward transfer-driven ejection of droplets will occur. The given threshold depends on the thickness of the donor film, the donor material, Laser pulse duration, and other factors. For short laser pulses (as described above, with a duration of 0.1 nanoseconds to 1 nanosecond), the threshold of forward transfer from self-induced laser will be extended to a range of laser flux values up to an upper limit For single droplet "volcanic eruption" jets, the upper limit is usually about 50% higher than the threshold flux. Above the upper limit of this flux, each laser pulse will often induce many small droplets to be ejected from the donor membrane at nanoscale droplet sizes. This latter high-flux state is referred to herein as the "sprayed state" and can help create a protective coating on certain parts of the embedded resistor, as explained further below.

The droplet 54 traverses the gap between the donor film 36 and the substrate 22 and then rapidly solidifies on the surface of the substrate into metal particles 56. The diameter of the particles 56 depends on the size of the droplets 54 that generate them, and the size of the gap that the particles traverse between the film 36 and the substrate 22. Generally, in the state of volcanic eruption, the particles 46 have a diameter in the range of 5 micrometers to 10 micrometers, and the diameter can be reduced to less than 2 micrometers by appropriately setting the above laser-induced forward transfer parameters.

The scanner 28 in the optical assembly 24 (FIG. 1) accurately sets the distance d between the positions of the adjacent particles 56 under the control of the control unit 40. This distance is selected to control the size of the contact area between adjacent particles, which determines the resistivity of the circuit traces formed by the particles. (The larger the pitch, the smaller the contact area, which translates into a larger resistivity, and vice versa.) Therefore, the resistance of a trace is determined by the particle pitch along with the length and width of the trace.

Assuming the donor film 36 has a specific composition and thickness, the control unit 40 can be calibrated to set the distance d and the irradiation parameters of the optical assembly 24 (such as the energy and duration of the laser pulse), and the donor film The gap between 36 and the acceptor substrate 22 achieves a desired resistivity. The resistivity can be expressed in terms of a "bulk factor", which means the ratio between the resistivity of the trace formed by the particles 56 and the bulk resistivity of the material constituting the film 36. The inventors have found that the relationship between the distance d and the bulk factor and irradiation parameters of a given donor film is consistent and repeatable, and therefore can be calibrated experimentally and deposited on the embedded resistor formulation ( recipe). Specifically, in the configuration of the system 20 illustrated in FIGS. 1 and 2, the inventors were able to achieve a body factor in the range of 3 to 30. For example, when the printing width is two droplets and the pitch d is selected to give one NiCr line with 50% overlap between adjacent particles 56, the inventors repeatedly reached a body factor of 10.

FIG. 3A is a schematic diagram illustrating details of the optical assembly 24 according to an embodiment of the present invention. The scanner 28 in this embodiment simultaneously forms a plurality of light beams 50. These beams can be used to generate multiple embedded resistors in parallel and thus increase the throughput of the system 20. (Alternatively, as illustrated in Figure 1, only a single laser beam may be used with a dual axis scanning mirror.)

The laser 26 emits a single pulsed beam of optical radiation, which may include visible radiation, ultraviolet radiation, or infrared radiation. A deflector 60 (such as an acoustic-optic deflector (AOD)) splits the input beam into a plurality of output beams. Such an acousto-optic deflector may include, for example, a piezoelectric crystal 62 that is driven by a multi-frequency driving signal to generate an acoustic wave in the deflector that separates an input light beam. At least one scanning mirror 64 scans the beam on the donor sheet 32 via the optical device 30. Although only a single mirror 64 is shown in Figure 3A, alternative embodiments (not shown) may employ a dual axis mirror that can be scanned together or independently, and / or any other known in the art Suitable types of single-axis or dual-axis deflectors and scanners, such as a fast steering mirror, a galvo-scanner, a piezoelectric device, or a microelectromechanical system (Micro -Electro-Mechanical System (MEMS) device.

The acoustooptic deflector 60 may be driven in various different modes to generate the plurality of output light beams and turn the plurality of output light beams. For example, U.S. Patent No. 8,395,083, the disclosure of which is incorporated herein by reference, sets forth several suitable drive technologies and assisted focusing and scanning optics that may be suitable for use in the optical assembly 24. According to one of these technologies, a multi-frequency drive signal causes the acousto-optic deflector to diffract the input beam into multiple output beams at different angles. PCT International Publication No. WO 2016/020817, the disclosure of which is incorporated herein by reference, sets forth further details of this type of scheme.

FIG. 3B is a schematic side view showing details of an optical assembly 24 according to another embodiment of the present invention. The features of this embodiment can be effectively combined with the features of the embodiment shown in FIG. 3A to more accurately control the optical assembly in general and an acoustic-optic modulator (AOM) in particular. 61.

In the embodiment shown in FIG. 3B, a beam splitter 66 removes a small portion of the light beam from the laser 26 after the acousto-optic modulator 61, and most of the beam energy reaches a scanner 69 (which can be connected with The one shown in FIG. 3A is the same or may be any other suitable type known in the art, such as the types mentioned above.) The scanner 69 passes the laser beam on the donor sheet 32 via the optical device 30 Scan it.

A power sensor 68 receives the portion of the light beam removed by the beam splitter 66 and measures the intensity of each laser pulse. The power sensor 68 feeds the measured value to the control unit 40 in real time. The control unit 40 uses the measured data to compensate for the fluctuation of the energy of the laser pulse. Based on the measured values, the control unit 40 evaluates the actual energy of the laser pulse and modifies the energy of subsequent pulses so that a series of continuous pulses can reach the target resistance (or more specifically, the resistance per unit length). Required average. In the example shown, the control unit 40 increases or decreases the energy of the next laser pulse by setting the attenuation level of the acousto-optic modulator 61, and controls the arrival of the donor sheet as needed. The level of laser power of the material 32. Alternatively, the control unit 40 may control the acousto-optic deflector 60 (FIG. 3A) and / or may directly control the laser 26 to maintain the required power level.

The control unit 40 may set the laser power as necessary to compensate for a change in the size of the gap into which the resistor is to be deposited. For example, the control unit 40 can adjust the energy level of the pulse wave to control the physical properties of the droplets, which determine the resistance of the resulting circuit trace. The physical properties that can be controlled in this way specifically include droplet volume, as well as density, porosity, and adhesion qualities between droplets.

Technology for resistor manufacturing

FIG. 4 is a flowchart schematically illustrating a method for manufacturing an embedded resistor according to an embodiment of the present invention. For convenience and clarity, the method is explained with reference to the elements of the system 20 shown in the previous figures. However, as an alternative, the principles of this method can be applied in other types of laser-induced forward transfer systems with suitable configurations, as such a skilled person will understand after reading this description. Although the steps of the method are presented here continuously, the method can be parallelized (for example, as shown in Figure 3, using multiple beams) and / or pipelined, and then High output yields multiple embedded resistors in parallel.

As a preliminary step, at a pre-calibration step 70, an operator of the system 20 pre-calibrates the volume resistivity of the laser-induced forward transfer deposition process. This step may include, for example, measuring the sheet resistivity of the donor film 36 (which may include compensating for the non-uniformity of the donor structure) and printing a sample of the resistor, and then performing the in-situ ( in- situ ) measurement. Based on these measurements, correction factors for the actual printing steps are calculated and loaded into the control unit 40. The correction factor is part of the printing recipe and includes control of droplet overlap, laser energy used in the process, and post-processing steps (such as laser annealing).

At an inspection step 72, using the image captured by the camera 42, the control unit 40 inspects the gap in the trace 44 where a resistor will be deposited and calculates the deposition parameters to be applied when forming the resistor. At this step, the control unit 40 measures the actual gap size in the trace 44 and modifies the geometry and formula for the printed resistor to compensate for the gap length relative to the original design as reflected in computer-aided manufacturing data, for example. No change. Based on this, the control unit 40 calculates a length correction factor, which is then applied to the printing recipe to control, for example, droplet pitch, laser energy used in the laser-induced forward transfer process, and post-processing steps (Such as laser annealing) to ensure that embedded resistors will meet applicable specifications.

At a surface preparation step 74, the surface of the substrate 22 is prepared for laser-induced forward transfer deposition. The system 20 may apply laser ablation at this step to clean the surface of the trace 44 in which the resistor will form a gap and possibly dug a trench 46 to accommodate the resistor. This step can use the same laser beam as in the subsequent laser-induced forward transfer printing step, or use a different laser, or possibly different beams of the same laser. Forming a narrow trench 46 at this step helps to enhance the capture and adhesion of the droplets 54 to the substrate 22, and enables the reliable formation of resistive traces with a width no larger than a single particle 56. In addition, narrow trenches can be used to limit the spread of the droplets 54 and thus form resistors that are comparable in size to the traces 44 or even smaller. For example, the inventors have applied laser-induced forward transfer deposition to create resistors in trenches less than 10 microns wide and less than 12.5 microns deep.

Additionally or alternatively, a laser 26 or other means may be applied to prepare the conductive traces 44 on the substrate 22 so that the ends of the resistor are connected to the traces. For example, the edge of the trace adjacent the track of the resistor can be cleaned and straightened. In addition or as an alternative, port holes may be dug in the edges of the traces 44 and these port holes will be filled with droplets 54 of the resistor material (for example, as illustrated in Figure 6C) ).

After preparing the substrate, at a laser-induced forward transfer deposition step 76, the laser 26 and the scanner 28 are operated to generate a resistive trace in the gap. As mentioned earlier, when printing resistive traces, the control unit 40 typically adjusts the optical assembly 24 to operate in a single drop "volcanic eruption" state. During this phase, the control unit 40 sets the distance between adjacent droplets 54 according to the applicable recipe, and adjusts the material parameters and the trace gap parameters obtained at steps 72 and 74 at the same time.

After the resistive trace is printed in this manner, the control unit 40 may modify the laser-induced forward transfer parameter of the optical assembly 24 to operate in a sprayed state, and then be protected by one of the tightly formed small droplets The resistive layer overlays the end of the resistive trace located in the port hole of the conductive trace 44. This layer helps seal the ends of the traces and therefore the subsequent degradation of the bond between the particles 56 and the traces 40. Such degradation may originally occur, for example, due to the penetration of a wetting chemical used when cleaning the substrate 22 after the resistor is deposited.

If necessary, after forming a resistive trace at step 76, at a annealing step 78, the laser 26 (or another focused heat source) is used to anneal the resistive trace. Such annealing tends to increase the size of the contact area between adjacent particles 56 and therefore improves the stability of the resulting resistor. Annealing can also reduce the resistivity of resistive traces. In some cases, especially when an accurate resistance value is required, the control unit 40 may probe the substrate 22 after step 76 to measure the resistance, and then anneal the resistive traces accordingly to reduce the resistance to Target value.

Alternatively, or in addition, an image of one of the resistive traces may be captured and then analyzed using ultraviolet illumination, for example, to measure a slight change in size. These slight changes may be related to small changes in resistance, and the annealing applied at step 78 may be used to compensate for these changes and thus improve resistor accuracy. Alternatively, other measurement techniques may be applied at this stage, such as using X-ray or eddy current sensing to measure density. As an alternative or in addition, annealing may be applied as part of the recipe to make it possible to adjust the length of the gap measured at step 72.

After the above steps, an area of the resistive traces on the substrate 22 is cleaned at a cleaning step 80. This step can again use the laser 26 or another laser to ablate the resistive material from the edge of the resistive trace to remove any material that deviates from the target width and shape of the trace. Additionally or alternatively, other types of cleaning (such as chemical cleaning) may be applied to remove waste.

Finally, at a final inspection step 82, the control unit 40 operates the camera 42 again to capture an image of one of the embedded resistors. The control unit 40 processes the image to identify any quality control defects through the above process and adjust the parameters of the system 20 to be applied in subsequent iterations.

FIG. 5 is a schematic plan view of a circuit substrate 22 according to an embodiment of the present invention, which shows a circuit trace 44 and a pattern 90 of one of the embedded resistors 98, 100, and 102 formed on the substrate. In this example, the trace 44 is connected to a pad 92, and an integrated circuit (IC) chip (not shown) will be bonded to the pad 92. The pads 92 and the traces 44 are formed on the substrate 22 by a printed circuit generation technique (such as a lithography technique or a direct writing technique) known in the art. In the trace 44, the gap 96 is kept open as a trajectory for laser-induced forward transfer printing of the embedded resistor using the process described above.

In the trace 44 to the right of the pad 92 shown in FIG. 5, several different types of embedded resistors 98, 100, and 102 have been printed. In each case, the resistance R will be determined by the bulk resistivity r of the donor film 36 (measured in ohms per unit length for a given trace width) and the bulk factor BF (by The laser induced forward transfer parameter is determined, as explained above) and the product of the length L of the resistive trace is given by: R = r × BF × L. The width of the resistive traces in the resistor is limited by the droplet size and the trench width, but can be made as small as 6 microns by carefully controlling the process parameters.

The resistor 98 simply includes a straight resistive trace, while the resistors 100 and 102 represent two different kinds of zigzag patterns. For a given size of the gap 96, these zigzag patterns can reach a trace length that is approximately three times the trace length of the resistor 98, and thus can produce a resistance value that is approximately three times as large as the resistor 98. Other zigzag patterns can be used to achieve even larger trace lengths, however this comes at the cost of occupying a wider area on the substrate. To ensure an accurate resistance value, it may be useful to carefully clean the space between the bends of the zigzag pattern of the resistors 100 and 102 at step 80.

6A to 6D schematically show details of a connection between one end of one of the circuit traces 44 and one of the embedded resistors 98 according to an embodiment of the present invention. Figure 6A shows a top view, and Figures 6B, 6C, and 6D are cross-sectional views of circuit traces and embedded resistors taken along lines B-B, C-C, and D-D shown in Figure 6A, respectively. Depending on the process parameters, Figures 6B and 6C show alternative embodiments in the form of alternative views at the same location on the resistor 98.

As shown in FIGS. 6B and 6C, a trench 110 has been dug in the surface of the substrate 22 by laser ablation at step 74, for example. The width of the trench can be approximately or even smaller than the average diameter of the droplets 54 and, therefore, the particles 56 are snugly held. In the embodiment shown in FIG. 6B, the size of the particles 56 and the depth of the trench 110 allow the particles to be completely contained in the trench. In the alternative embodiment shown in FIG. 6C, the particles 56 extend above the top of the trench 110 onto the surface of the substrate 22.

As shown in Figure 6D, a port hole 112 has been similarly dug or otherwise formed in the end of the trace 44. At step 76, droplets 54 of the resistive material are injected by a laser-induced forward transfer process to form one or more particles 56 in the port hole 112, and then a spray layer 114 formed of smaller particles is formed to Isolate port holes to prevent entry of corrosive materials.

The shapes and forms of the resistors shown in FIGS. 5 and 6A to 6D are presented herein by way of example and not limitation. Those skilled in the art will understand other shapes and forms after reading this description, and these other shapes and forms are considered to be within the scope of the present invention. In addition, the principles of the present invention can be applied to generate other types of embedded circuit components, including those with capacitive and / or inductive properties.

Therefore, it should be understood that the embodiments described above are described by way of example, and the present invention is not limited to the content specifically shown and described above. Rather, the scope of the invention encompasses the combinations and sub-combinations of the various features described above, as well as variants and finishes that will be envisioned by those skilled in the art after reading the foregoing description and have not been disclosed in the prior art.

20‧‧‧System

22‧‧‧ Receptor substrate

24‧‧‧ Optical Assembly

26‧‧‧Laser

28‧‧‧Scanner

30‧‧‧Optics

32‧‧‧ donor sheet

34‧‧‧ donor substrate

36‧‧‧ Donor Film

38‧‧‧ Sports Assembly

40‧‧‧control unit

42‧‧‧ Camera

44‧‧‧ conductive traces / circuit traces

46‧‧‧ditch

50‧‧‧pulse laser beam

52‧‧‧ "Volcano" pattern

54‧‧‧Metal Droplets

56‧‧‧ metal particles

60‧‧‧ Deflector / Acoustooptic Deflector

61‧‧‧Acoustooptic Modulator (AOM)

62‧‧‧Piezoelectric Crystal

64‧‧‧scanning mirror

66‧‧‧ Beamsplitter

68‧‧‧Power Sensor

69‧‧‧Scanner

70 ~ 82‧‧‧step

90‧‧‧ pattern

92‧‧‧ pad

96‧‧‧ Clearance

98‧‧‧Embedded Resistor

100‧‧‧Embedded Resistor

102‧‧‧Embedded Resistor

110‧‧‧ditch

112‧‧‧Porthole

114‧‧‧ spray coating

B-B, C-C, D-D‧‧‧ lines

d‧‧‧pitch

The following detailed description of the embodiments of the present invention will be read in conjunction with the accompanying drawings, which will more fully understand the present invention. In the drawings:

FIG. 1 is a schematic side view of a system for making an embedded resistor according to an embodiment of the present invention; FIG.

FIG. 2 is a schematic cross-sectional view of a trajectory for depositing an embedded resistor on an acceptor substrate according to an embodiment of the present invention, showing a laser droplet of a metal droplet from a donor film toward a site; Induced forward-driven ejection (LIFT-driven ejection);

FIG. 3A is a schematic diagrammatic illustration of an optical assembly used in a system for manufacturing an embedded resistor according to an embodiment of the present invention; FIG.

FIG. 3B is a schematic diagram of an optical assembly used in a system for manufacturing an embedded resistor according to another embodiment of the present invention; FIG.

FIG. 4 is a flowchart schematically illustrating a method for manufacturing an embedded resistor according to an embodiment of the present invention; FIG.

FIG. 5 is a schematic top view of a circuit substrate according to an embodiment of the present invention, which shows circuit traces and embedded resistors formed on the substrate;

FIG. 6A is a schematic detailed view of a connection between a circuit trace and an embedded resistor according to an embodiment of the present invention; FIG.

FIG. 6B is a schematic cross-sectional view of the circuit trace and the embedded resistor shown in FIG. 6A taken along line B-B shown in FIG. 6A according to an embodiment of the present invention;

Figure 6C is a schematic cross-sectional view of the circuit trace and embedded resistor shown in Figure 6A taken along line C-C shown in Figure 6A according to an alternative embodiment of the present invention; and

FIG. 6D is a schematic cross-sectional view of the circuit trace and the embedded resistor shown in FIG. 6A taken along the line D-D shown in FIG. 6A according to an embodiment of the present invention.

Claims (32)

A method for manufacturing an electronic device, the method includes: identifying a locus on a circuit substrate, on the circuit substrate, between a first endpoint and a second endpoint of the locus Forming a resistor having a specified resistance; positioning a transparent donor substrate near the track identified on the circuit substrate, the transparent donor substrate having a first surface opposite to the first surface and a second A surface, and a donor film formed on the second surface, the donor film including a resistive material, wherein the second surface faces the circuit substrate; and guiding the pulse of laser radiation through the donor The first surface of the substrate is irradiated on the donor film to induce droplets of the resistive material to be ejected from the donor film to corresponding adjacent locations on the circuit substrate along the trajectory, where A separation between adjacent positions is selected to form a circuit trace having the specified resistance between the first terminal and the second terminal. The method of claim 1, wherein the interval is selected to control a size of a contact area between the droplets at the adjacent positions, the size determining the resistance of the circuit trace. The method of claim 1, wherein guiding the pulses includes adjusting an energy level of the pulses to control one or more physical properties of the droplets, the one or more physical properties determining the This resistance of the circuit trace. The method of claim 1, wherein identifying the trajectory includes identifying a gap between a plurality of conductors on the circuit substrate, and wherein the pulse waves that guide the laser radiation are included in the gap to form the circuit trace. line. The method of claim 4, wherein identifying the gap includes measuring the gap and forming the circuit trace in response to the measuring. The method of claim 5, wherein forming the circuit trace comprises setting the interval between the adjacent positions onto which the droplets are ejected in response to the measurement, so that the circuit trace is caused Will have that specified resistance. The method of claim 5, wherein forming the circuit trace comprises adjusting the physical property or properties of the droplets by setting an energy of the pulse wave in response to the measurement to cause the circuit The trace will have that specified resistance. The method of claim 5, wherein performing the measurement comprises capturing and processing an image of the circuit substrate to identify and measure the gap. The method according to claim 1, comprising: before the spraying of the droplets, forming a trench along the trajectory in the circuit substrate, wherein the pulse waves guiding the laser radiation include The droplets are injected into the trench. The method of claim 9, wherein the trench has a width smaller than an average diameter of one of the droplets. The method of claim 1, comprising annealing the circuit trace. The method according to claim 1, wherein the pulses of guiding the laser radiation include setting an energy of a laser beam irradiated on the donor film and a spot size, so that the Each of the pulse waves induces a single droplet of the resistive material from the jet of the donor film. The method of claim 12, wherein the energy of the pulses is set to a first value to induce the ejection of the single droplet per pulse, and wherein the method includes: after forming the circuit trace, The other pulses of the laser radiation are guided onto the donor film with a second energy value greater than the first value, so that a spray layer formed from small particles of the resistive material is sprayed from the donor. A body film is sprayed and overlaid on one end of the circuit trace. The method according to claim 1, wherein guiding the pulse waves includes guiding multiple pulse waves of the laser radiation to irradiate at different corresponding points on the donor film at the same time, so that multiple pulse waves are produced in parallel on the circuit substrate. Resistive circuit traces. The method of claim 1, wherein directing the pulses comprises scanning the laser radiation to form the circuit in a meander pattern between the first endpoint and the second endpoint. Trace. The method of claim 1, wherein guiding the pulse waves includes using an acoustic-optic deflector to scan the pulse waves on the donor substrate, and measuring the pulse waves. An intensity, and the acousto-optic deflector is controlled according to the measured intensity to compensate for fluctuation of one of the pulse waves irradiating on the donor substrate. A system for making an electronic device includes: a transparent donor substrate having a first surface and a second surface opposite to each other, and a donor film formed on the second surface, the donor The film contains a resistive material; a positioning assembly for positioning the donor substrate near a track on a circuit substrate, on the circuit substrate, at a first end and a second end of the track A resistor having a specified resistance is formed between the points, wherein the second surface of the donor substrate faces the circuit substrate; and an optical assembly for guiding the pulse of laser radiation through the donor substrate The first surface is irradiated on the donor film to induce droplets of the resistive material to be ejected from the donor film to corresponding adjacent positions along the trajectory on the circuit substrate, where the phases An interval between adjacent positions is selected to form a circuit trace having the specified resistance between the first terminal and the second terminal. The system of claim 17, wherein the interval is selected to control one of a size of a contact area between the droplets at the adjacent positions, the size determining the resistance of the circuit trace. The system of claim 17, wherein the optical assembly is used to adjust an energy level of the pulse waves to control one or more physical properties of the droplets, and the one or more physical properties determine the This resistance of the circuit trace. The system according to claim 17, wherein the trace includes a gap between a plurality of conductors on the circuit substrate, and wherein the circuit trace is formed in the gap. The system described in claim 20 includes a control unit for measuring the gap and controlling the formation of the circuit trace in response to the measurement. The system according to claim 21, wherein the control unit is configured to set the interval between the adjacent positions onto which the droplets are ejected in response to the measurement, so that the circuit trace will be With this specified resistance. The system according to claim 21, wherein the control unit is configured to adjust the one or more physical properties of the droplets by setting an energy of the pulse waves in response to the measurement so as to cause the circuit trace The line will have that specified resistance. The system described in claim 21 includes a camera for capturing an image of the circuit substrate, and wherein the control unit processes the image to identify and measure the gap. The system of claim 17, wherein the optical assembly is used to form a trench in the circuit substrate along the trajectory and inject the droplets into the trench before the jetting of the droplets. The system of claim 25, wherein the trench has a width smaller than the average diameter of one of the droplets. The system of claim 17, wherein the optical assembly is used to anneal the circuit trace. The system according to claim 17, wherein the optical assembly sets an energy and a focus size of a light beam of the laser radiation irradiated on the donor film, so that each pulse of the pulse waves The wave induces a single droplet of the resistive material from the jet of the donor film. The system of claim 28, wherein the energy of the pulse waves is set to a first value to induce the ejection of the single droplet per pulse wave, and wherein the optical assembly is further used to: form the circuit After the trace, a second energy value greater than the first value is used to guide the other pulses of the laser radiation onto the donor film, so that a sprayed layer formed by the small particles of the resistive material starts from the A donor film is sprayed and overlaid on one end of the circuit trace. The system according to claim 17, wherein the optical assembly is used to guide the multiple pulses of the laser radiation to different corresponding points on the donor film at the same time, so as to produce a plurality of parallel waves on the circuit substrate. Resistive circuit traces. The system of claim 17, wherein the optical assembly is configured to scan the laser radiation to form the circuit trace in a zigzag pattern between the first endpoint and the second endpoint. The system according to claim 17, wherein the optical assembly comprises: an acousto-optic deflector for scanning the pulse waves on the donor substrate; a sensor for measuring the pulses An intensity of one wave; and a control unit coupled to control the acousto-optic deflector in response to the measured intensity to compensate for fluctuations in the energy of one of the pulse waves irradiated on the donor substrate.