Pattern transfer printing method

Abstract

There is provided a pattern transfer printing (PTP) method comprising: (i) processing a belt comprising a plurality of pattern transfer sheets having a pattern of trenches for transferring the pattern transfer sheets in a controllable manner for paste filling and successive pattern transfer, (ii) continuously and uniformly mixing at least two types of conductive printing pastes having different particle sizes and / or continuously and uniformly mixing at least one type of conductive printing paste with an NIR (near infrared) absorbing dye to form a uniform paste mixture, (iii) filling the trenches on the conveyed pattern transfer sheet with the paste mixture, (iv) transferring the wafer in a controllable manner for pattern transfer, and (v) transferring the slurry mixture from the pattern transfer sheet onto the transferred wafer by releasing the slurry mixture from the trenches when the laser beam is irradiated. The method results in highly precise ultrafine conductive wires, for example for photovoltaic (PV) applications.

Description

Technical Field

[0001] This invention relates to the field of pattern transfer printing (PTP), and more specifically, to the field of photovoltaic cell manufacturing. Background Technology

[0002] Printing metallic features on the receiving substrate is typically performed by applying a high-viscosity metal paste, primarily based on silver or copper, gold, or other metal powders combined with liquid organic components. Printing conductor (metal) lines (also known as grid lines) on silicon PV (photovoltaic) cells is a critical manufacturing step that significantly impacts cell efficiency and cost. Recent advances in PV cell design and processes, such as PERC (passivated emitter and back contact), TOPCon (tunneling oxide passivated contact), and HJT (intrinsic thin-film heterojunction), require a continuous reduction in grid line width to 10 micrometers or even smaller. This width reduction presents significant challenges to at least two aspects of PV cell processes: (i) high-quality printing of ultrafine metal grid lines with the desired high aspect ratio, and (ii) maintaining low line resistance and low contact resistance, despite the extremely small line cross-section and minimal contact area between the printed lines and the silicon wafer.

[0003] The currently used screen printing (SP) method, limited by the printing of ultra-fine lines, can be replaced by pattern transfer printing (PTP) to address the challenges of printing technology. Pattern transfer printing has proven its ability to print ultra-fine silver lines—for example, see Lossen et al. (2015), Pattern Transfer Printing (PTP™) for c-Si solar cell metallization, 5th Workshop on Metallization for Crystalline Silicon Solar Cells, EnergyProcedia 67: 156-162, the entire contents of which are incorporated herein by reference. It teaches pattern transfer printing (PTP™) as a non-contact printing technology for advanced front-side metallization of c-Si PV solar cells, based on laser-induced deposition of a polymer donor substrate comprising multiple trenches filled with metal paste.

[0004] Shin et al. (2015, Bimodally dispersed silver paste for the metallization of a crystalline silicon solar cell using electrohydrodynamic jet printing, Solar Energy Materials & Solar Cells 136: 148–156) and Han et al. (2008, Preparation of Conductive Silver Paste Using Bimodal Particles, Journal of Nanoscience and Nanotechnology 8: 5576–5580) respectively taught bimodally dispersed silver pastes for electrohydrodynamic jet printing and screen printing, the entire contents of which are incorporated herein by reference. Summary of the Invention

[0005] The following is a simplified summary of the invention to provide a preliminary understanding of the invention. This summary does not necessarily identify key elements or limit the scope of the invention, but is merely intended to illustrate the following description.

[0006] One aspect of the present invention provides a pattern transfer printing (PTP) method, the method comprising: processing a belt comprising a plurality of pattern transfer sheets having patterns having corresponding grooves as segments thereof, for controllably conveying the pattern transfer sheets for paste filling and sequentially performing pattern transfer; continuously and uniformly mixing at least two types of conductive printing pastes with different particle sizes to form a uniform paste mixture; filling the grooves on the conveyed pattern transfer sheets with the paste mixture; controllably conveying a plurality of wafers for pattern transfer; and transferring the paste mixture from the pattern transfer sheets to the conveyed wafers by releasing the paste mixture from the grooves upon irradiation with a laser beam.

[0007] One aspect of the present invention provides a pattern transfer printing (PTP) method, the method comprising: processing a tape comprising a plurality of pattern transfer sheets having corresponding groove patterns as segments thereof for controllably conveying the pattern transfer sheets for paste filling and sequential pattern transfer; continuously and uniformly mixing at least one type of conductive printing paste with an NIR (near-infrared) absorbing dye to form a uniform paste mixture; filling the grooves on the conveyed pattern transfer sheets with the paste mixture; controllably conveying a plurality of wafers for pattern transfer; and transferring the paste mixture from the pattern transfer sheets to the conveyed wafers by releasing the paste mixture from the grooves upon irradiation with a laser beam, wherein the NIR absorbing dye is configured to absorb at the wavelength of the laser beam irradiation.

[0008] These, additional and / or other aspects and / or advantages of the invention are set forth in the following detailed description; may be inferred from the detailed description; and / or can be learned through practice of the invention. Attached Figure Description

[0009] To better understand the embodiments of the present invention and to illustrate how the embodiments of the present invention can be implemented, reference will now be made to the accompanying drawings by way of example only, in which the same reference numerals always indicate corresponding elements or sections.

[0010] In the attached diagram:

[0011] Figure 1A This is a high-level schematic flowchart illustrating a pattern transfer printing (PTP) method according to some embodiments of the present invention.

[0012] Figure 1B This is a high-level schematic cross-sectional view of a pattern transfer sheet on a belt according to some embodiments of the present invention.

[0013] Figure 1C This is a high-level schematic cross-sectional view of the transfer line from the pattern transfer sheet to the substrate, showing the paste mixture filling the grooves on the pattern transfer sheet according to some embodiments of the present invention.

[0014] Figure 2 A comparative reflectance measurement of the slurry composition disclosed according to some embodiments of the present invention with that of prior art slurries is provided.

[0015] Figure 3A The image shows lines printed using existing technology pastes, while Figures 3B to 3D Comparative images are provided of printed lines of a paste composition disclosed according to some embodiments of the present invention and lines printed with pastes of the prior art.

[0016] Figure 4ACross-sectional images of a printing line having coarse and fine silver particles in a disclosed paste mixture according to some embodiments of the present invention are provided, compared to which... Figure 4B Cross-sectional images of printing lines of prior art paste containing only coarse silver particles are provided.

[0017] Figure 5 This is a high-level schematic side view illustration of units and elements in a PTP system according to some embodiments of the present invention.

[0018] Figures 6A to 6C This is a high-level schematic illustration of a filling head according to some embodiments of the present invention.

[0019] It will be understood that, for the sake of simplicity and clarity, the elements shown in the figures are not necessarily drawn to scale. For example, for clarity, the dimensions of some elements may be enlarged relative to others. Furthermore, reference numerals may be repeated in the figures where deemed appropriate to indicate corresponding or similar elements. Detailed Implementation

[0020] In the following description, various aspects of the invention will be described. Specific configurations and details are set forth for purposes of explanation in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without the specific details presented herein. Furthermore, well-known features may have been omitted or simplified so as not to obscure the invention. Referring specifically to the accompanying drawings, it is emphasized that the details shown are by way of example and are presented only for the purpose of illustrative discussion of the invention, and to provide the most useful and readily understood description of what is believed to be the principles and concepts of the invention. In this regard, no attempt has been made to show the structural details of the invention in more detail than necessary for a basic understanding of the invention; the description taken in conjunction with the drawings makes it apparent to those skilled in the art how various forms of the invention can be practiced in practice.

[0021] Before explaining at least one embodiment of the invention in detail, it should be understood that the invention is not limited in its application to the details of the construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments that can be practiced or performed in various ways, as well as combinations of the disclosed embodiments. Furthermore, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered limiting.

[0022] Unless otherwise specifically stated, as is apparent from the following discussion, it should be understood that throughout the discussion, terms such as “processing,” “computing,” “counting,” “determining,” “enhancing,” “deriving,” or similar terms refer to the behavior and / or process of a computer or computing system or similar electronic computing device that manipulates and / or converts data represented as physical quantities, such as electronic quantities, within the registers and / or memory of the computing system into other data similarly represented as physical quantities within the memory, registers, or other such information storage, transmission, or display devices of the computing system.

[0023] The embodiments of the present invention provide efficient and economical methods and mechanisms for pattern transfer printing, and thereby provide improvements to the technical field of producing electrical contacts, and more specifically to the technical field of producing photovoltaic cells.

[0024] A pattern transfer printing (PTP) method is provided, comprising: (i) processing a strip having a plurality of pattern transfer sheets with grooved patterns for controllably conveying the pattern transfer sheets for paste filling and sequential pattern transfer; (ii) continuously and uniformly mixing at least two types of conductive printing pastes with different particle sizes and / or continuously and uniformly mixing at least one type of conductive printing paste with NIR (near-infrared) absorbing dye to form a homogeneous paste mixture; (iii) filling the grooves on the conveyed pattern transfer sheets with the paste mixture; (iv) controllably conveying a wafer for pattern transfer; and (v) transferring the paste mixture from the pattern transfer sheets to the conveyed wafer by releasing the paste mixture from the grooves upon irradiation with a laser beam. The method produces highly precise ultrafine conductive lines, such as ultrafine conductive lines (also known as “grid lines”) for photovoltaic (PV) applications.

[0025] The following provides disclosures regarding the use of two or more types of pastes and / or the use of mixed release dyes, followed by a general description of the PTP system as more fully provided in U.S. Patent Application No. 18 / 429,655, and a description of the option of mixing dyes in pastes as more fully provided in U.S. Patent Application No. 17 / 971,689. The entire contents of both applications are incorporated herein by reference.

[0026] Figure 1AThis is a high-level flowchart illustrating a pattern transfer printing (PTP) method 500 according to some embodiments of the present invention. The method steps can be performed with respect to any PTP system, such as those described herein, which may optionally be configured to implement method 500. Method 500 may be implemented at least in part by at least one computer processor or by at least one control unit 105 (e.g., one or more personal computers, PCs, and / or one or more programmable logic controllers, PLCs, or combinations thereof). Some embodiments include a computer program product comprising a computer-readable storage medium having a computer-readable program implemented using the computer-readable storage medium, and the computer-readable program being configured to perform the relevant steps of PTP method 500. PTP method 500 may include the following steps, regardless of their order.

[0027] PTP method 500 includes: processing a belt comprising a plurality of pattern transfer sheets having corresponding groove patterns as segments thereof for controllably conveying the pattern transfer sheets for paste filling and sequential pattern transfer (step 510); continuously and uniformly mixing at least two types of conductive printing pastes with different particle sizes to form a homogeneous paste mixture (step 520) and / or continuously and uniformly mixing at least one type of conductive printing paste with NIR (near-infrared) absorbing dye to form a homogeneous paste mixture (step 525); filling the grooves on the conveyed pattern transfer sheets with the paste mixture (step 530); controllably conveying a plurality of wafers for pattern transfer (step 540); and transferring the paste mixture from the pattern transfer sheets to the conveyed wafers by releasing the paste mixture from the grooves when a laser beam irradiates a receiving substrate (e.g., a silicon wafer) (step 550). See also Figure 1C To provide advanced schematic diagrams.

[0028] Figure 1A The arrows in the diagram schematically indicate three different types of implementations disclosed herein: (i) continuously and uniformly mixing at least two conductive printing pastes with different particle sizes (step 520), (ii) continuously and uniformly mixing at least one type of conductive printing paste with NIR absorbing dye (step 525), or (iii) continuously and uniformly mixing at least two conductive printing pastes with different particle sizes and continuously and uniformly mixing at least one type of conductive printing paste with NIR absorbing dye (steps 520 and 525) to form a homogeneous paste mixture.

[0029] In some embodiments, at least two types of conductive printing paste may include a first coarse-grained type having a median particle size (e.g., diameter) between 0.5 µm and 5 µm, and a second fine-grained type (referred to as nanoparticles) having a median particle size (e.g., diameter) between 50 nm and 200 nm. In a non-limiting example, the median particle size of the first coarse-grained type may be 2 µm ± 1 µm and the median particle size of the second fine-grained type may be 80 nm ± 50 nm (e.g., 70 nm to 80 nm, 80 nm to 100 nm, 50 nm to 80 nm, or any other intermediate value or subrange).

[0030] In various embodiments, fine-grained pastes can be formed, for example, from 5% to 25% by weight of a paste mixture. Both coarse and fine grains can be made of the same conductive material, such as silver. Fine grains can enhance and improve the adhesion of the paste mixture to the substrate (e.g., silicon) and potentially improve the conductivity between the substrate and the lines, as well as within the lines, by filling voids (e.g., compared to...). Figure 4A and Figure 4B ).

[0031] In some embodiments, mixing at least two types of conductive printing pastes (step 520) may further include mixing a NIR (near-infrared) absorbing dye configured to absorb at the wavelength of the laser beam irradiation to form a homogeneous paste mixture (step 525). The NIR absorbing dye may be configured to absorb at the wavelength of the laser beam irradiation.

[0032] In some embodiments, mixing at least one type of conductive printing paste with NIR absorbing dye (step 525) may also include mixing at least two types of conductive printing paste with different particle sizes to form a homogeneous paste mixture (step 520).

[0033] In various embodiments, the NIR absorbing dye may include any of the dyes disclosed herein, for example, forming a paste mixture of 0.5% to 5% by weight. It should be noted that because silicon is practically transparent in this spectral range, the use of NIR laser irradiation ensures that laser irradiation for the transfer paste lines will not damage the silicon wafer.

[0034] Laser sources can include pulsed lasers and / or continuous wave (CW) lasers or quasi-CW lasers, such as IPG Photonics. TM The company's YLM-150 / 1500-QCW-AC-Y11 TMUsing a paste mixture with two or more particle sizes and / or a mixture of NIR absorbing dyes can reduce the power required by the laser source, for example, to about half the laser power required by existing printing pastes (see, for example, below on...). Figures 3A to 3D In the table, the power is reduced from 600 W to 300 W or even to 200 W because the reduced reflection lowers the power required to release the paste lines from the trenches. The inventors note that, given the prior art, the reduction in the power of the laser source required for paste release is unexpected; the prior art typically teaches increasing the power used to enable high-quality release of narrow grid lines (e.g., approximately 10 µm) from corresponding narrow trenches on the pattern transfer sheet. The inventors note that the disclosed PTP method 500 reduces light reflectivity (and correspondingly increases the irradiation absorption of the paste, e.g., see...). Figure 2 The NIR wavelength used allows for reduced laser power. Furthermore, the disclosed PTP method 500 reduces paste particle debris generated near the printing line by mixing fine-grained paste with coarse-grained paste or including any of NIR absorbing dyes. The disclosed PTP method 500 can release the paste line without using a dedicated release layer, thereby simplifying the preparation process of the pattern transfer film on the tape and reducing manufacturing costs.

[0035] In various embodiments, the PTP method 500 can be configured to form transfer paste lines (grid lines) up to 10 µm wide and having an aspect ratio of at least 0.8.

[0036] In various embodiments, the PTP method 500 can be configured to form uniform transfer paste lines (grid lines) with minimal debris and low ripple (see, for example, [link to relevant documentation]). Figures 3B to 3D ).

[0037] The inventors realized through experimentation that the quality of the printed ultrafine lines largely depends on the quality of the mixed paste. Optimal conditions for mixing the paste can be achieved using the filling unit 122 of the printing system before filling the grooves in the pattern transfer sheet 530. Continuous mixing of the paste during the operation of the filling unit 122 ensures that the paste does not separate or dry out between the initial mixing and the application of the paste.

[0038] The disclosed PTP method 500 produces highly precise ultrafine conductive lines, such as those for photovoltaic (PV) applications. The transferred lines are uniform, characterized by a high aspect ratio and low waviness, and the disclosed PTP method produces minimal debris while reducing the power output required by the laser source—because less radiation is reflected from the paste mixture after adding fine-grained paste or NIR absorbing dye to coarse-grained paste—see, for example, [link to relevant documentation]. Figure 2 .

[0039] Figure 1B This is a high-level schematic cross-sectional view of a strip (pattern transfer sheet) 205 according to some embodiments of the present invention. Figure 1C This is a high-level schematic cross-sectional view of the transfer lines of the paste mixture 201, which is filled into the trenches 210 on the pattern transfer sheet 205 (in the paste filling step 530) according to some embodiments of the present invention, from the pattern transfer sheet 205 to the substrate 205 (e.g., the silicon wafer in the paste transfer step 550). In some embodiments, the strip 205 may be transparent for laser irradiation and includes at least a top polymer layer 214, which includes trenches 210 formed thereon by imprinting, pneumatic forming, or laser forming. In the illustrated non-limiting example, the trenches 210 are illustrated in a non-limiting manner as a trapezoidal cross-section. The paste mixture, comprising coarse-grained paste and fine-grained paste and / or NIR absorbing dye, is filled into the trenches by a paste filling unit 120 having a filling head 122, and subsequently released from the trenches onto the wafer by laser irradiation to form conductive lines (gate lines). Figure 1C (as further described below.) Other details are disclosed below and in U.S. Application No. 17 / 971,689, the entire contents of which are incorporated herein by reference.

[0040] Figure 2 A comparative reflectance measurement of a disclosed slurry composition according to some embodiments of the present invention with that of a prior art slurry is provided. Figure 2 The reflectivity is provided according to existing technology for silver paste (by Heraeus) TM SOL9681 manufactured TM A comparison of the irradiation wavelength of the slurry and the irradiation wavelengths of two disclosed slurry mixtures, one of which has a fine particle size (with 24% by weight of Novacentrix). TM Metalon HPS-U11 manufactured TM SOL9681 for slurry mixing TM Slurry - SOL9681 TM The slurry contains silver particles with an average size of 2 µm and Metalon HPS-U11 TM The slurry contains silver nanoparticles with an average size of 80 nm, and another disclosed slurry mixture contains NIR absorbing dye (SOL9681 mixed with 1% by weight of LUNIR5 dye powder manufactured by Luminochem). TM (Slurry). Reflectance measurement was performed using an integrating sphere and Spectralon. TM Cary 4000 for Diffuse Reflection Material Calibration TMThe measurements were performed on a spectrophotometer. As the results show, both incorporating fine-grained slurry into prior art slurries and incorporating NIR absorbing dyes into prior art slurries reduced the reflectance of the slurry mixtures across most of the measurement range—from 400 nm to 1100 nm and beyond in the visible and infrared ranges. Specifically, at NIR laser wavelengths from 1060 nm to 1070 nm, both mixtures reduced reflectance from 30% to between 20% and 25%, resulting in a significant reduction in the laser power required to achieve the same slurry release power. It should be noted that, due to the wide wavelength range of reflectance reduction, the disclosed slurry mixtures offer similar benefits at other wavelengths in the 400 nm to 1100 nm range when using other types of lasers. It should also be noted that slurry mixtures of coarse and fine-grained slurries showed significantly reduced reflectance in the visible range (400 nm to 800 nm) and in NIR above 1100 nm compared to NIR absorbing dyes.

[0041] In a non-limiting example, the slurry mixture may include between 0.5 wt% and 5 wt% of NIR absorbing dye (e.g., between 0.5 wt% and 1 wt%, between 1 wt% and 2 wt%, between 2 wt% and 3 wt%, between 3 wt% and 5 wt%, or any intermediate value) and / or between 10 wt% and 50 wt% of fine particles (nanoparticles) (e.g., between 10 wt% and 20 wt%, between 20 wt% and 30 wt%, between 30 wt% and 50 wt%, or any intermediate value) – either or both mixed with coarse particles.

[0042] Figures 3B to 3D Printing lines of the disclosed paste compositions according to some embodiments of the present invention are provided, as well as lines printed using prior art pastes. Figure 3A Comparative images are provided. Each line is shown at 5x and 20x optical magnification, and the required power, line dimensions (width and aspect ratio – width divided by height), degree of debris, and line waviness are indicated in the table below. Therefore, the disclosed PTP method 500 demonstrates improved PTP performance, resulting in cleaner, finer, and straighter deposited lines using lower irradiation power. This is in contrast to the prior art SOL9681. TM Compared to slurry ( Figure 3A ), Figure 3B and Figure 3D The coarse and fine particle mixture in both includes 24% by weight of Metalon HPS-U11 TM SOL9681 for fine-grained slurry mixing TM Coarse-grained slurry, and Figure 3C and Figure 3DThe NIR absorbing dyes in the sample include 1% by weight of LUNIR5 dye.

[0043] Table: Performance comparison of the disclosed method with existing technologies

[0044] Required laser power Achieved line width Achieved aspect ratio Horizontal line ripple Debris level Existing technology slurry, Figure 3A 600 W 24 µm to 27 µm 0.4 to 0.46 high high Publicly available slurry mixtures—coarse and fine particle sizes, Figure 3B 300 W 22 µm 0.55 middle Low The disclosed slurry mixture—containing NIR absorbing dyes, Figure 3C 300 W 21 µm 0.59 Low Low The disclosed slurry mixture—both coarse and fine-grained—contains NIR-absorbing dyes. Figure 3D 200 W 21 µm 0.62 Low No debris

[0045] The disclosed PTP method 500 reduces the power level of the laser source required to transfer lines from grooves on a pattern transfer sheet to a wafer. While transferring existing pastes requires 600 W of laser power, the disclosed paste mixture requires only half the power—300 W, or even a third—200 W for transfer, primarily due to the reduced reflectivity of the paste mixture (see, for example). Figure 2 ).

[0046] Compared with existing methods, the disclosed PTP method 500 enables the printing of finer lines (21 μm to 22 μm, approximately 20% finer than the existing 0.4 to 0.46) with a higher aspect ratio (0.62, 50% higher aspect ratio).

[0047] Printing lines using the disclosed PTP method 500 result in cleaner lines (less or no printing paste debris on the substrate) and lower waviness (more uniform straight lines).

[0048] The initial results further indicate that the disclosed PTP method 500 also leads to improved physical contact in the silver particles and between the silver particles and the substrate (which may also help reduce line resistance and / or reduce contact resistance between the line and the silicon substrate).

[0049] Figure 4A Cross-sectional images of a printing line having coarse and fine silver particles in a disclosed paste mixture according to some embodiments of the present invention are provided, compared to which... Figure 4B Cross-sectional images of printing lines from prior art pastes containing only coarse silver particles are provided. (Example) Figure 4A As demonstrated, fine-grained particles fill the gaps between coarse-grained metal particles and the silicon texture of the wafer, and potentially (i) reduce gate line resistance, and (ii) achieve better bonding between the printed lines and the textured silicon substrate, thereby potentially improving the efficiency of PV cells. The inventors point out that thoroughly and continuously mixing the slurry to produce a uniform slurry mixture results in a uniform distribution of nanoparticles (fine-grained particles) within micron-sized particles (coarse-grained particles), compared to the coarse-grained lines of the prior art. Figure 4B Compared to this, this could potentially improve the conductivity within the line and between the line and the substrate. Figure 4AFurthermore, incorporating nanoparticles of the same material (e.g., silver) into the gate lines requires no additional processes (such as cleaning dye particles from the silicon surface when using a dedicated release layer).

[0050] Advantageously, compared to prior art premixed pastes, the disclosed PTP method 500 (i) eliminates the need for any premixing, which can deteriorate in terms of uniformity over time and during use (smaller and larger particles may separate within the paste during storage, transport, or application), (ii) allows for precise adjustment of the paste composition for each preparation batch, (iii) controls the degree of irradiation absorption of the paste mixture (which can also deteriorate over time for premixed pastes), and (iv) ensures continuous and uniform mixing of the paste throughout the printing process, resulting in consistent high-quality printing. For example, the disclosed PTP method 500 offers advantages over prior art bimodal dispersed metal pastes because the fine particles are significantly smaller than those available in such pastes (e.g., smaller particles in commercially available bimodal dispersed metal pastes are typically between 100 nm and 300 nm, rather than the disclosed 70 nm to 80 nm, due to processing and storage limitations, which makes a significant difference in functionality such as filling voids and improving conductivity). Furthermore, compared to existing bimodal paste mixtures configured for application by inkjet printing or screen printing, the disclosed paste mixture is configured for transfer by the disclosed PTP method 500, and therefore has completely different properties adapted to these application methods.

[0051] Advantageously, for the increasingly higher linewidth-to-height ratios required—which results in the line contact width relative to the silicon substrate being reduced to a relatively small amount of coarse grain (a grain size of 2 µm compared to a 10 µm linewidth, and also see, for example, [reference needed]) Figure 4B — The disclosed PTP method 500 involves mixing fine-grained particles (see, for example, [link to relevant documentation]). Figure 4A This increases and improves the contact area between the line and the substrate, thereby providing a larger surface area for the conductive particles and improving the compliance of the transfer line with the roughness of the silicon substrate.

[0052] In some implementations, using a paste mixture that includes both coarse and fine particles as well as NIR absorbing dyes can further improve PTP performance and printing line quality.

[0053] In some embodiments, the disclosed PTP method 500 can also achieve printed lines with a high aspect ratio (narrower and taller lines with a greater aspect ratio) due to better conductivity, lower waviness (straighter lines), and reduced debris. Advantageously, the disclosed PTP method 500 may eliminate the need for post-processing of the transferred lines (e.g., by heating), such as to remove paste debris or other residues and / or to increase the conductivity of the paste.

[0054] The high uniformity of the slurry mixture is achieved by the disclosed PTP method 500 through continuous movement of the slurry mixture via the slurry filling head 122 described below.

[0055] Figure 5 This is a high-level schematic side view illustration of the units and elements in a PTP system 100 according to some embodiments of the present invention. Figure 5 The advanced schematic side view illustration provides a non-limiting example of the arrangement of elements in processing unit 200 relative to paste filling unit 120 (e.g., performing paste filling step 530) and paste transfer unit 350 (e.g., performing pattern transfer step 550). A brief description follows. Figure 5 The units and elements illustrated herein, with further details of non-limiting embodiments provided in successive figures, are shown. One or more control units 105 may be configured to monitor and / or control units of the PTP system 100 via various processors and to coordinate the operation of the PTP system 100. It should be noted that the corresponding PTP method is described in more detail in U.S. Application No. 18 / 429,655, the entire contents of which are incorporated herein by reference.

[0056] The PTP system 100 is configured to apply a pattern of conductive material onto a wafer via non-contact printing. The PTP system 100 includes a tape processing unit 200 configured to process a tape 205, which includes multiple pattern transfer sheets 205A and 205B having corresponding groove patterns as segments thereof. The tape processing unit 200 is configured to controllably convey pattern transfer sheets 205A for paste filling and successive pattern transfer sheets 205B for pattern transfer, respectively. The tape processing unit 200 is configured to move the tape 205 in a step-repeating manner (one sheet after another) from a feed roller 222 to a take-up roller 242. The PTP system 100 also includes a paste filling unit 120 configured to fill the grooves on the conveyed pattern transfer sheets 205A with conductive printing paste. The belt processing unit 200 can be further configured to convey pattern transfer sheets one by one for paste filling (indicated sheet 205A) and / or pattern transfer (indicated sheet 205B), while continuously monitoring tension and the machine orientation (MD, along the belt) and lateral machine orientation (CMD, perpendicular to MD) position of the belt 205. The PTP system 100 also includes a wafer handling and positioning unit 400 configured to controllably convey multiple wafers 90 for pattern transfer at locations very close to the pattern transfer sheets (e.g., within a range of 0.1 mm to 0.5 mm). The PTP system 100 also includes a paste transfer unit 350 configured to transfer conductive printing paste from the respective pattern transfer sheet 205B to the respective conveyed wafer 90B by releasing printing paste from the trench under the irradiation of a laser beam 80.

[0057] The cells of the PTP system 100 are mounted in a compact manner on a rigid frame to minimize the system's footprint. As a general design feature, tape processing is performed along a vertical direction (indicated as "z") and along a horizontal direction (indicated as "y", called the machine direction, MD), while wafer processing is performed along a direction perpendicular to it, for example, along another horizontal direction (indicated as "x", called the lateral machine direction, CMD).

[0058] The processing unit 200 can be configured to convey pattern transfer sheets (e.g., pattern transfer sheet 205A) one by one for paste filling in step 530 of the paste filling method by means of a movable paste filling head 122 and / or for pattern transfer (e.g., pattern transfer sheet 205B) in step 550 of the paste transfer method performed in the paste pattern transfer unit by means of a movable scanning device 355 (e.g., movable along the x and y axes and optionally tiltable at an angle θ, or possibly an optical head that scans along the y axis, is movable along the x axis, and optionally tiltable at an angle θ). For example, the planes of the paste filling unit 120 and the pattern transfer sheet 205B can be set at an angle of 0° to 30° away from the vertical xz plane.

[0059] In one embodiment, one or more top adjusters 225 and bottom adjusters 245 may be configured to buffer the stepping and repetitive motion of the belt 205 from the feed roller 222 to the take-up roller 242, respectively, when the pattern transfer sheet 205A is filled with paste and / or when the paste of the pattern transfer sheet 205B is transferred, so as to ensure that these are performed with the respective pattern transfer sheets in a stationary position. The top adjuster 225 and / or the bottom adjuster 245 may be configured to maintain tension in the belt 205, wherein the belt moves through at least a portion of the PTP system 100.

[0060] It should be noted that in the PTP system 100, the paste filling unit 120 is positioned almost vertically (along the z-axis) to ensure a short travel distance from the paste-filled pattern transfer sheet 205A to the pattern transfer sheet 205B at the paste transfer unit 350, thus minimizing changes in the state of the filling paste (e.g., due to pre-printing drying). For example, the near-vertical position can be configured to minimize the travel distance of the pattern transfer sheet from state 205A to state 205B, and thereby optionally position the laser scanning device directly behind the vertical filling unit, closer to the roller 227A located between 205A and 205B. Figure 5 The diagram is schematically illustrated. The near-vertical position of the paste filling unit 120 is advantageous compared to the prior art horizontal position of the paste filling unit because it reduces the distance between the paste filling position (205A) and the paste transfer position (205B) of the pattern transfer sheet 205.

[0061] The front side 102 of the PTP system 100 can be configured to have an easily accessible feed roller 222 and a take-up roller 242 to meet replacement and maintenance requirements, and an easily accessible slurry filling unit 120 (from the same front side 102) to meet slurry filling and maintenance requirements.

[0062] The PTP system 100 may optionally include a belt reuse unit 250 configured to clean the pattern transfer sheet after pattern transfer to provide a reusable pattern transfer sheet. For example, the belt reuse unit 250 may include a belt cleaning unit 252 in which the belt 205 can be mechanically cleaned, for example, using a scraper, ultrasonic waves, and / or other methods, and / or chemically cleaned using a cleaning solution; it may also include a belt drying unit 255 having idle rollers 244, 246 positioned as needed to maintain safe belt movement. The belt 205 may be moved by one or more belt drive motors 230 (illustrated) and further supported by one or more rollers 227 along the path of the belt 205 through the PTP system 100.

[0063] The paste filling unit 120 may include a movable paste filling head 122 and a movable opposing roller 125, the movable opposing roller 125 being configured to support the back side of the pattern transfer sheet 205A during paste filling. A non-limiting example of the paste filling unit 120 is shown below. Figures 6A to 6C See the illustration for more details.

[0064] In some embodiments, the wafer processing and positioning unit 400 may include at least one platform 410 (hereinafter referred to as an xz platform) movable along the x and z axes, wherein each platform 410 includes at least one retainer, and wherein each retainer supports the wafer 90 and is capable of moving the wafer along the y and θ axes (the θ axis relates to the rotation of the wafer about the xy plane). In some embodiments, the two xz platforms 410 of the wafer processing and positioning unit 400 may be configured to operate in parallel relative to each other. Each platform 410 may include two retainers for holding the wafer 90, each retainer ensuring movement of the wafer along the y and θ axes, thus enabling faster wafer processing and continuous wafer movement during pattern transfer. Multiple cameras image the incoming wafer, enabling more accurate wafer alignment within the printing system, and thus more accurate alignment of the printed conductive lines onto the wafer pattern.

[0065] The paste transfer unit 350 (e.g., a laser scanning device, such as a pulsed laser or a continuous wave CW laser) may include a laser scanning device (scanning head) 355 (e.g., movable along the CMD via a linear platform, ball screw platform, etc.), the laser scanning device (scanning head) 355 being configured to control the irradiation of the pattern transfer sheet 205B via a laser beam for depositing paste from the patterned grooves of the pattern transfer sheet 205B.

[0066] The PTP system 100 may also include a print quality control unit (not shown) configured to control the print quality of the pattern transfer, particularly detecting minute defects such as openings or gaps within the printed grid lines transferred onto the wafer or other defects in the pattern. For example, the print quality control unit may be based on an imaging camera that transmits acquired images of the wafer to a processor 452 for imaging processing.

[0067] The belt processing unit 200 can be configured to move the belt 205 while feeding pattern transfer sheets 205A one by one for paste filling (at the paste filling unit 120) and / or for pattern transfer (at the pattern transfer unit 350) by continuously controlling the belt tension and the precise position of the sheet in both the MD and CMD coordinates.

[0068] The CMD positions of the feed roller 222 and take-up roller 242 can be continuously controlled and corrected if necessary by means of one or more control units 105, for example by controlling their drive motors. The top adjuster 225 and bottom adjuster 245 can be configured to support the rapid stepping movement of the pattern transfer sheets 205A, 205B (as segments of belt 205) to their respective positions for paste filling and pattern transfer. Idle rollers 227 (some only indicated) can be configured to guide the belt movement via the belt handling unit 200.

[0069] The tape processing unit 200 can be configured to quickly and accurately supply and replace tape segments (pattern transfer sheets) for printing wafers. The tape processing unit 200 can be further configured with a compact design that minimizes space requirements and is housed within a stable and rigid frame or chassis to support its operation and facilitate easy maintenance. The tape reuse unit 250 can be located within the frame and along the path of the tape 205, enabling the tape 205 to be reused—making the entire process more efficient and economical.

[0070] The disclosed PTP method 500, PTP system 100, and band 205 can be used to print ultrafine lines of metal paste mixtures to generate electronic circuits, for example, to generate wires, pads, or other features on laminates for PCBs or other printed circuit boards, or on silicon wafers for photovoltaic (PV) cells, for example. Other applications may include generating conductive features during the manufacturing process of mobile phone antennas, decorative and functional automotive glass, semiconductor integrated circuits (ICs), semiconductor IC package connections, printed circuit boards (PCBs), PCB component assembly, optical, biological, chemical, and environmental sensors and detectors, radio frequency identification (RFID) antennas, organic light-emitting diode (OLED) displays (passive or active matrices), OLED irradiation sheets, printed cells, and other applications. For example, in non-limiting solar energy applications, the metal paste may include one or more metal powders, optional glass frits and one or more modifiers, one or more volatile solvents and one or more non-volatile polymers and / or one or more resins. Non-limiting examples of pastes include those from Heraeus TM The SOL9651BTM.

[0071] Figures 6A to 6C This is a high-level schematic illustration of a filling head 122 according to some embodiments of the present invention. Figure 6A and 6C A schematic side view of the cross-section is provided, and Figure 6B A stereoscopic view is provided, viewed from below the filling head 122.

[0072] The paste filling unit 120 may include a frame on which a paste filling head 122 and a bottom roller 124 (not shown) are mounted, and which move simultaneously relative to the frame. Movement of the paste filling head assembly may be controlled by one or more control units 105, for example, via corresponding flexible frames (not shown) attached to the paste filling head 122, drive motors (not shown), and / or frame motion systems (not shown). The bottom roller 125 may be configured to resist the paste filling head 122 and support the pattern transfer sheet 205A during paste filling of the pattern transfer sheet 205A by the paste filling head 122. The bottom roller may be configured to roll during operation, possibly controllably (see additional details in U.S. Application No. 18 / 429,655, the entire contents of which are incorporated herein by reference).

[0073] The slurry filling unit 120 can be configured to rapidly, uniformly, and accurately fill high-viscosity slurry into trenches with a high aspect ratio, as described herein with respect to PTP method 500. The slurry filling unit 120 can be further configured to clean the surface of the belt 205 after filling, for example, as disclosed in WIPO Publication No. 2015128857, the entire contents of which are incorporated herein by reference.

[0074] like Figures 6A to 6C As schematically illustrated, the filling head 122 of the slurry filling unit 120 may include: at least two supply openings 161, 169, an inner cavity 165, and at least one dispensing opening 160, which are in fluid communication (e.g., see...). Figure 6B and Figure 6C The pressurized slurry supply unit 155 is configured to circulate slurry 190 through the printhead 150. The pressure in the pressurized slurry supply unit can be regulated to maintain continuous circulation of the slurry mixture through the supply openings 161, 169 and the cavity 165 and to control the distribution of the slurry mixture through the distribution opening 160. For example, the pressurized slurry supply unit 155 may include a slurry pump 152 and a pressurized slurry reservoir 154 in fluid communication with the cavity 165 of the printhead 150, the pressurized slurry reservoir 154 and the slurry pump 152 configured to circulate the slurry mixture and to continuously and uniformly mix the slurry mixture. In a non-limiting example, the slurry pump 152 may include a rotary pressure-sealed displacement system with a self-sealing rotor / stator design for dispensing precise volumes, such as those from Dymax. TM eco-PEN450 TM .

[0075] In various embodiments, the slurry filling unit 120 includes at least one pressure sensor 140 configured to measure the pressure of the circulating slurry; for example, as a non-limiting example, in Figures 6A to 6C The pressure sensor 140, schematically illustrated and associated with the slurry mixer 130, or in Figure 6A Pressure sensors 140A and 140B are schematically illustrated at either end of the printhead 150. Alternatively or additionally, pressure measurement can be implemented within components of the pressurized slurry supply unit 155, such as the slurry pump 152 and / or the slurry reservoir 154. The slurry filling unit 120 may also include at least one processor 167 and / or controller (in... Figure 6C(Schematic illustration) At least one processor 167 and / or controller communicates with control unit 105 and is configured to adjust the pressure in pressurized slurry supply unit 155 (or components of pressurized slurry supply unit 155) based on a measured pressure of the circulating slurry mixture. Slurry filling unit 120 may also include one or more slurry mixers 130 configured to mix the circulating slurry. Slurry mixer 130 may, for example, be a static mixer that mixes slurry by utilizing its pressurization. In a non-limiting example, slurry mixer 130 may include a disposable plastic static mixer made of a large-diameter plastic housing containing multiple mixing elements, such as those from Stamixco. TM GXF-10-2-ME TM .

[0076] The pressurized slurry supply unit 155 may also be configured to introduce a slurry mixture into the cavity 165 via at least one inlet opening 161 of the at least two supply openings and receive a circulated slurry mixture via at least one outlet opening 169 of the supply opening in the printhead body 150. Typically, the inlet opening 161 and outlet opening 169 are located at the top of the printhead 150 opposite to the dispensing opening 160, which faces the pattern transfer sheet with grooves to be filled with a uniform slurry mixture. Alternatively or additionally, the inlet opening 161 and / or outlet opening 169 may be located on the side and / or extension of the printhead 150.

[0077] The pressurized slurry supply unit 155 may include a pressure-controlled slurry reservoir 154 in fluid communication with a slurry pump 152 and a mixer 130. The pressure-controlled slurry reservoir 154 may be configured to deliver a slurry mixture to the slurry pump 152, which may be configured to deliver the slurry mixture to an inlet opening 161 via the mixer 130. The pressurized slurry supply unit 155 may be further configured to mix a slurry mixture from an outlet opening 169 with a slurry mixture delivered from the pressure-controlled slurry reservoir 154 to the slurry pump 152. For example, as... Figure 6A and Figure 6CAs schematically illustrated, slurry 190 in slurry reservoir 154 can be conveyed (191) to slurry pump 152 and mixed (192) with slurry mixture 197 from outlet opening 169 of printhead 122, to be pumped into mixer 130 by slurry pump 152. Slurry mixture 193 from mixer 130 can be conveyed (194) to inlet opening 161 of printhead body 150, wherein slurry mixture 196 moves along inner cavity 165, and some slurry 195 can be dispensed through dispensing opening 160 to form patterns on transfer sheet 205, such as lines subsequently (after tape movement, from transfer sheet 205) printed on receiving substrate such as wafer 90. For example, the printed lines (gate lines) may include silver lines approximately 20 μm wide on a silicon wafer for PV cells (see Lossen et al., 2015, as a non-limiting example), or narrower ultrafine lines having a width of approximately 10 μm, 15 μm, an intermediate value, or smaller. The remaining slurry mixture 197 is then mixed with slurry mixture 191 from slurry reservoir 154 (e.g., delivered via nozzle 163 at junction 151) to compensate for the dispensing amount, and the slurry is circulated through slurry filling unit 120 to maintain its mechanical properties and support continued mixing of the slurry to maintain its chemical homogeneity. In some embodiments, slurry filling unit 120 may be further configured to alter the slurry composition, for example, by adding additives such as solvents, to keep the slurry mixture homogeneous, and pressure in slurry filling unit 120 may also be monitored. For example, additives such as solvents may be added to the slurry entering mixer 130 if desired. Although mixtures of coarse and fine slurries, or mixtures of coarse slurry with NIR absorber dyes, can be initially loaded into the slurry reservoir 154, the design of the printhead 122 enables proper, thorough, and uniform mixing within the mixer 130 and throughout the cycle of the slurry mixture through the slurry filling unit head 122. The high uniformity of the slurry mixture is achieved by the disclosed PTP method 500 through continuous movement of the slurry mixture through the slurry filling unit head 122. For example, during the slurry filling process, the slurry mixture can be dynamically mixed by the slurry mixer 130 within the slurry filling unit 120. Optimal mixing quality and slurry uniformity can be advantageously achieved through dynamic mixing within the slurry mixer 130 and the cavity 165 of the filling unit head 122 as part of the filling process, which is not possible by using a pre-mixed slurry without the disclosed continuous and uniform mixing.

[0078] In various embodiments, the dispensing slit, such as the opening 160 defined by the slit edge 162 (e.g., a metal slit lip), the print head 150, and the cavity 165 can be elongated (see, for example, see...). Figure 6BIt is constructed according to the characteristics of the slurry mixture (e.g., viscosity value), the specified throughput and specified characteristics (e.g., length, width, and optional cross-section) of the lines or other elements dispensed by the printhead 150. In some embodiments, the dispensing opening 160 may include one or more slits, one or more openings, a plurality of linearly arranged openings, such as one or more rows of circular or elliptical openings, etc.

[0079] In various embodiments, the slurry material may include a conductive silver-based metal slurry and can typically have a high viscosity (e.g., in the range of tens to hundreds of Pa·s). For example, in non-limiting solar applications, the metal slurry may comprise metal powder, optional glass frit and modifiers, volatile solvents and non-volatile polymers and / or resins. Non-limiting examples of slurries include coarse-grained slurries (e.g., from Heraeus). TM SOL9651B TM ), fine-grained slurry (e.g., from Novacentrix) TM Metalon HPS-U11 TM ) and / or optionally a mixture with NIR absorbing dyes (e.g., LUNIR5 dye powder from Luminochem).

[0080] The slurry filling unit 120 may include one or more pressure sensors 140, 140A, 140B configured to measure the pressure of the circulating slurry at one or more corresponding locations along the slurry circulation path. For example, pressure sensors 140, 140A, 140B may be configured to: be adjacent to inlet opening 161 and outlet opening 169; be in fluid communication with the interior cavity 165 of printhead body 150; and / or be associated with any of the mixer 130, slurry reservoir 154, and / or slurry pump 152. Pressure-related indications from pressurized slurry reservoir 154 and / or slurry pump 152 may also be used to monitor slurry circulation through slurry filling head 122 and / or monitor and, possibly, modify slurry properties, such as slurry viscosity, for example, by adding solvent. The slurry filling unit 120 may also include at least one controller (e.g., as part of or communicating with control unit 105) and / or as at least one computer processor 167, such as… Figure 6CAs illustrated in the figure, the at least one controller communicates, for example, via a communication link with any component of the slurry filling unit 120, and is configured to adjust the pressure in the pressure-controlled slurry reservoir 154 and / or slurry pump 152 based on a measured pressure of the circulating slurry, for example, received from one or more pressure sensors 140, 140A, 140B. In a non-limiting example, any pressure sensor in the pressure sensor 140 may include, for example, a small-profile, media-compatible piezoresistive silicon pressure sensor (e.g., from TE Connectivity) encapsulated in a stainless steel housing. TM MEAS 86A TM Or equivalent sensor).

[0081] In various embodiments, the pressure-controlled slurry reservoir 154 and slurry pump 152 may open adjacent to the outlet opening 169 of the printhead 150, and the slurry filling unit 120 may include a conduit 135 connecting the outlet of the mixer 130 to the inlet opening 161 of the printhead 150. In some embodiments, the pressure-controlled slurry reservoir 154 and slurry pump 152 may open adjacent to the outlet opening 169 of the printhead 150, the mixer 130 may be adjacent to the inlet opening 161 of the printhead 150, and the conduit 135 may connect the slurry pump 152 to the mixer 130. A pressure sensor 140 may be associated with the mixer 130. The size and orientation of the slurry reservoir 154 and the slurry pump 152 may vary; for example, both the slurry reservoir 154 and the slurry pump 152 may be configured perpendicular to the printhead 150 (see, for example, see...). Figure 6A Alternatively, one or both of the slurry reservoir 154 and the slurry pump 152 may be configured at an angle to the print head 150. For example, the slurry pump 152 may be tilted to distribute its weight more evenly across the print head 150, such as... Figure 6B and Figure 6C The illustration is intended to be illustrative.

[0082] In various embodiments, the conduit 135 can be adjusted to accommodate any arrangement of the slurry reservoir 154, the slurry pump 152, and the mixer 130, in order to make the slurry filling unit 120 more compact or to adjust the slurry filling unit 120 to meet given space and weight distribution requirements within the printing press. The retainer 145 is schematically illustrated (see, for example, [reference]). Figure 6A The retainer 145 serves as an attachment element for attaching the paste filling unit 120 to the printing press (for a non-limiting example, see, for example, U.S. Patent No. 9,616,524). In a non-limiting example, the conduit 135 may connect between the opening 131 in the mixer 130 and the opening 138 of the connector 137 located at the inlet opening 161 in the printhead 150 (see, for example, U.S. Patent No. 9,616,524). Figure 6A Alternatively, conduit 135 may be connected between opening 131 in slurry pump 152 and opening 138 in mixer 130 (see, for example, [link to relevant documentation]). Figure 6C ).

[0083] Return to Figure 1B The transfer sheet with 205 and pattern may include at least one polymer layer, which may be selected from at least one of the following materials: polyethylene, polypropylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, fully aromatic polyester, other copolyesters, polymethyl methacrylate, other copolyacrylates, polycarbonate, polyamide, polysulfone, polyethersulfone, polyetherketone, polyamide-imide, polyether-imide, aromatic polyimide, alicyclic polyimide, fluorinated polyimide, cellulose acetate, cellulose nitrate, aromatic polyamide, polyvinyl chloride, polyphenols, polyarylates, polyphenylene sulfide, polyphenylene ether, polystyrene.

[0084] The grooves 210 may be periodic, and / or may include grooves, recesses, and / or indentations imprinted into the top polymer layer 214 in a similar manner, and may have similar or different profiles. For example, the grooves 210 may have various profiles (cross-sectional shapes), such as trapezoidal, circular, square, rectangular, and / or triangular profiles. In various embodiments, the pattern of the grooves 210 on the strip 205 may include an array of continuous grooves 210 and / or separated indentations. It should be noted that the term "groove" should not be construed as limiting the shape of the groove 210 to linear elements, but is understood broadly to include grooves 210 of any shape.

[0085] The band 205 may include a top polymer layer 214 and a bottom polymer layer 212, the bottom polymer layer 212 having a higher melting temperature than the imprinting temperature of the top polymer layer 214. In some embodiments, the top polymer layer 214 may be made of a semi-crystalline polymer and have a melting temperature, for example, below 150°C, below 130°C, below 110°C, or an intermediate value. In some embodiments, the top polymer layer 214 may be made of an amorphous polymer and have a glass temperature below 160°C, for example, below 140°C, below 120°C, below 100°C, or an intermediate value. The bottom polymer layer 212 may have a higher melting temperature or glass transition temperature than the top polymer layer 214. For example, the bottom polymer layer 212 may have a melting temperature above 150°C, above 160°C (e.g., biaxially oriented polypropylene), above 170°C, and up to 400°C (e.g., certain polyimides), or an intermediate value.

[0086] In some embodiments, the thicknesses of the top polymer layer 214 and the bottom polymer layer 212 (respectively) can be between 10 μm and 100 μm, for example, between 15 μm and 80 μm, between 20 μm and 60 μm, between 25 μm and 45 μm, or other intermediate values, with the bottom polymer layer 212 preferably being at least as thick as the top polymer layer 214. The polymer layers can be bonded by an adhesive layer 213 that is thinner than 10 μm (e.g., thinner than 8 μm, thinner than 6 μm, thinner than 4 μm, thinner than 2 μm, or intermediate values) and is also transparent to laser irradiation. For example, in some embodiments, the top polymer layer 214 can be several μm thicker than the depth of the trench 210, for example, 5 μm, 3 μm to 7 μm, 1 μm to 9 μm, or up to 10 μm thick. For example, trench 210 may be 20 μm deep, top polymer layer 214 may be 20 μm to 30 μm thick, and the thickness of bottom polymer layer 212 may be in the range of 25 μm to 45 μm (it should be noted that a thicker bottom polymer layer provides better mechanical properties). It should be noted that the term "trench" should not be construed as limiting the shape of trench 210 to linear elements, but is understood broadly to include trench 210 of any shape.

[0087] The temperature and thickness of the top polymer layer and the bottom polymer layer (214 and 212, respectively) can be designed so that the top polymer layer 214 has good molding, ductility, and a certain mechanical strength, while the bottom polymer layer 212 has good mechanical strength. Both the top polymer layer and the bottom polymer layer (214 and 212, respectively) can be designed to have good adhesive properties.

[0088] In various embodiments, the support portion of the pattern transfer sheet 205 may include a stretchable substrate having specified tensile properties, such as a polymer substrate, or the support portion of the pattern transfer sheet 205 may include a rigid substrate, such as a glass substrate.

[0089] In some embodiments, using the disclosed paste mixture in PTP method 500 enables the printing of paste patterns (e.g., paste grid lines) on the receiving substrate 90 at much higher aspect ratios, such as at least 0.7 and up to 1 to 2 instead of the prior art's 0.4 to 0.5; and enables the printing of extremely narrow grid lines and / or mesh lines, down to or below 10 µm wide, instead of the prior art's 25 µm to 30 µm and above. Furthermore, avoiding the use of volatile compounds in the paste mixture (in embodiments without NIR absorber dyes) expands the range of printable pastes and makes the process less sensitive to the drying of the paste mixture.

[0090] The printing paste layer may include organic and solid components of a metal such as silver, copper, tin, or bismuth that can serve as a conductive medium. The organic components can be selected to provide the specific pressure required to overcome the resistance of the printing paste layer separating from the trench. For example, the specified pressure can be achieved by adjusting the content of the organic components in the printing paste layer and / or the coating within the trench, and / or by adjusting the ratio of the solid components of the conductive metal medium. For example, when the printing paste layer has high viscosity and high damping characteristics upon contact with the inner wall of the trench, and / or if the content of the solid component is high, or if the organic component has strong adhesion, the resistance of the printing paste layer can be relatively large, and the corresponding specified pressure can be configured to be higher.

[0091] Non-limiting examples of NIR absorbing dye components include diimine ion complexes, dithioene complexes, and / or phthalocyanines. The illustrated diimine ion complexes may include, for example, an alkyl chain as one or more residues R and a compound such as 2SbF6. - Counterions such as those (not shown).

[0092]

[0093] Additional, non-limiting examples of the components of the NIR absorbing dye in any of the disclosed embodiments (as part of the coating and / or as part of the slurry mixture) may include any of the following: cyanine (tetramethylindole (di)-carboncyanine) dyes, such as, for example, open-chain cyanine (R2N) + =CH[CH=CH] n - NR2), Aryl=N + =CH[CH=CH] n -NR2), closed-chain anthocyanin (Aryl=N) + =CH[CH=CH] n -N=Aryl), neutral anthocyanins (R2N) + =CH[CH=CH] n -CN and R2N + =CH[CH=CH] n -CHO), for example, with the extended [CH=CH] n Chains, or variants or mixtures thereof; phthalocyanine or naphtholine dyes (including four isoindole units linked by a nitrogen atom ring) or their metal complexes (e.g. with aluminum or zinc), dithioene metal complexes (having one to three dithioene ligands), such as those having nickel, such as squaricine dyes III, quinone analogs, diimine compounds and azo derivatives, and / or any variants, derivatives and / or combinations thereof.

[0094] Advantageously, the NIR absorbing dye is directly mixed into the paste mixture without the need for solvents or binders, and leaves virtually no unwanted paste debris after the paste line is transferred to the silicon wafer. Furthermore, the disclosed mixture avoids the use of a separate release layer as described in U.S. Application No. 17 / 971,689, and thus also avoids its residue deposition on the wafer.

[0095] Therefore, in addition to commercially available printing pastes (e.g., from Heraeus) TM SOL9651B TM In addition to slurry mixtures containing coarse and fine metal particles, slurry mixtures may include NIR absorbing dyes, such as diimine ion complexes, dithioene complexes, and / or phthalocyanines illustrated herein. It should be noted that NIR absorbing dyes may be added to silver pastes and / or silver epoxy paste mixtures.

[0096] Some embodiments include a paste for use in a pattern transfer process (the pattern transfer process includes filling the paste into grooves in a polymer pattern transfer sheet arranged in a prescribed pattern, and continuously releasing the paste from the grooves onto a receiving substrate upon laser beam irradiation). For example, in the case of NIR irradiation, the paste includes a release material configured to enhance the release of the paste from the grooves, wherein the release material includes at least one NIR absorbing dye, the NIR absorbing dye including at least one of diimine ion complexes, dithioene complexes, phthalocyanines, derivatives, salts, and / or combinations thereof. Non-limiting examples include those from TCI (Tokyo Chemical Industries, Ltd.) and Epolin. TM Epolight TM 1117 (tetra(decyl)ammonium structure) and / or Luminochem TM Lunir5 TM The dye.

[0097] Various embodiments include methods and systems for applying a coating to trenches, as disclosed in U.S. Application No. 17 / 971689, the entire contents of which are incorporated herein by reference. However, the inventors note that, advantageously, the disclosed slurry mixture is transferred to form ultrafine lines (fine, straight, with a high aspect ratio and minimal slurry debris) – without requiring any coating in the trenches.

[0098] From Figures 1A to 6C The elements can be combined in any operable combination, and the illustration of certain elements in some figures but not in others is for illustrative purposes only and not for limitation.

[0099] In the above description, embodiments are examples or implementations of the invention. Various presentations such as “one embodiment,” “implementation,” “some embodiments,” or “a number of embodiments” do not necessarily refer to the same embodiment. Although various features of the invention may be described in the context of a single embodiment, these features may also be provided individually or in any suitable combination. Conversely, although the invention may be described herein in the context of a single embodiment for clarity, the invention may also be implemented in a single embodiment. Some embodiments of the invention may include features of the different embodiments disclosed above, and some embodiments may include elements of the other embodiments described above. Elements of the invention disclosed in the context of a particular embodiment should not be considered as limiting use to that particular embodiment. Furthermore, it should be understood that the invention may be practiced or carried out in various ways, and the invention may be implemented in some embodiments other than those outlined in the above description.

[0100] This invention is not limited to those diagrams or corresponding descriptions. For example, the process does not need to move through each illustrated box or state, or in the exact same order as illustrated and described. Unless otherwise defined, the meanings of technical and scientific terms used herein should be commonly understood by one of ordinary skill in the art to which this invention pertains. Although the invention has been described with respect to a limited number of embodiments, these embodiments should not be construed as limiting the scope of the invention, but rather as examples of some preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the invention. Therefore, the scope of the invention should not be limited by what has been described to date, but rather by the appended claims and their legal equivalents.

Claims

1. A pattern transfer printing method, comprising: The process includes a belt of multiple pattern transfer sheets, each having a corresponding groove pattern, as segments thereof, for controllably conveying the pattern transfer sheets for paste filling and sequential pattern transfer. At least two types of conductive printing pastes with different particle sizes are continuously and uniformly mixed to form a homogeneous paste mixture. The grooves on the conveyed pattern transfer sheet are filled with the paste mixture. Multiple chips can be transferred in a controllable manner for pattern transfer, and The paste mixture is transferred from the pattern transfer sheet to the conveyed wafer by releasing the paste mixture from the trench when irradiated by a laser beam.

2. The pattern transfer printing method according to claim 1, wherein, The at least two types of conductive printing pastes include at least a first coarse-grained type and a second fine-grained type, the first coarse-grained type having a median particle size between 0.5 µm and 5 µm, and the second fine-grained type having a median particle size between 50 nm and 200 nm.

3. The pattern transfer printing method according to claim 1 or 2, wherein, The median particle size of the first coarse-grained type is 2 µm ± 1 µm, and the median particle size of the second fine-grained type is 80 nm ± 50 nm.

4. The pattern transfer printing method according to any one of claims 1 to 3, wherein, The mixing also includes continuously and uniformly mixing near-infrared absorbing dyes to form a homogeneous slurry mixture, the near-infrared absorbing dyes being configured to absorb at the wavelength of the laser beam irradiation.

5. The pattern transfer printing method according to any one of claims 1 to 4, wherein the method is configured to form a transfer paste line at most 10 µm wide and having an aspect ratio of at least 0.

8.

6. The pattern transfer printing method according to any one of claims 1 to 5, wherein the method is configured to form a uniform transfer paste line with minimal debris and low waviness.

7. A pattern transfer printing method, comprising: The process includes a belt of multiple pattern transfer sheets, each having a corresponding groove pattern, as segments thereof, for controllably conveying the pattern transfer sheets for paste filling and sequential pattern transfer. At least one type of conductive printing paste is continuously and uniformly mixed with a near-infrared absorbing dye to form a homogeneous paste mixture. The grooves on the conveyed pattern transfer sheet are filled with the paste mixture. Multiple wafers are transported in a controllable manner for pattern transfer, and the paste mixture is transferred from the pattern transfer sheet to the transported wafers by releasing the paste mixture from the trenches during laser beam irradiation. The near-infrared absorbing dye is configured to absorb at the wavelength of the laser beam irradiation.

8. The pattern transfer printing method according to claim 7, wherein, The mixing also includes the continuous and uniform mixing of at least two types of conductive printing pastes with different particle sizes to form a homogeneous paste mixture.

9. The pattern transfer printing method according to claim 8, wherein, The at least two types of conductive printing pastes include at least a first coarse-grained type and a second fine-grained type, the first coarse-grained type having a median particle size between 0.5 µm and 5 µm, and the second fine-grained type having a median particle size between 50 nm and 200 nm.

10. The pattern transfer printing method according to claim 8 or 9, wherein, The median particle size of the first coarse-grained type is 2 µm ± 1 µm, and the median particle size of the second fine-grained type is 80 nm ± 50 nm.

11. The pattern transfer printing method according to any one of claims 8 to 10, wherein the method is configured to form a transfer paste line at most 10 µm wide and having an aspect ratio of at least 0.

8.

12. The pattern transfer printing method according to any one of claims 8 to 10, wherein the method is configured to form a uniform transfer paste line with minimal debris and low waviness.

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