Local metallization of semiconductor substrates using laser beams

Abstract

The present disclosure describes local metallization of a semiconductor substrate using a laser beam, and the resulting structure, such as a microelectronic device, a semiconductor substrate and / or a solar cell. For example, a solar cell includes a substrate and a plurality of semiconductor regions disposed in or above the substrate. A plurality of conductive contact structures are electrically connected to the plurality of semiconductor regions. Each conductive contact structure includes a locally deposited metal portion disposed in contact with a corresponding semiconductor region.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority and the benefit of earlier filing dates to U.S. Provisional Application No. 62 / 773,172 filed on November 29, 2018, U.S. Provisional Application No. 62 / 773,168 filed on November 29, 2018, U.S. Provisional Application No. 62 / 773,148 filed on November 29, 2018, and U.S. Provisional Application No. 62 / 654,198 filed on April 6, 2018, each of which is hereby incorporated by reference in its entirety. Technical Field

[0003] Embodiments of the present disclosure relate to the fields of renewable energy or semiconductor processing, and in particular, involve localized metallization of substrates using a laser beam, and the resulting structures. Background Art

[0004] Photovoltaic cells (often referred to as solar cells) are well-known devices for converting solar radiation directly into electrical energy. Generally speaking, solar cells are manufactured on semiconductor wafers or substrates using semiconductor processing techniques to form pn junctions near the surface of the substrate. Solar radiation that impinges on the substrate surface and enters the substrate forms electron and hole pairs in the bulk of the substrate. The electron and hole pairs migrate to p-doped and n-doped regions in the substrate, thereby generating a voltage difference between the doped regions. The doped regions are connected to conductive regions on the solar cell to direct current from the cell to an external circuit coupled thereto.

[0005] Electrical conversion efficiency is an important characteristic of solar cells because it is directly related to the ability of the solar cell to generate electricity; higher efficiency provides added value to the end customer; and, all other things being equal, higher efficiency also reduces the manufacturing cost per watt. Likewise, simplified manufacturing methods offer the opportunity to reduce manufacturing costs by reducing the unit cost of production. Therefore, techniques for improving solar cell efficiency and techniques for simplifying the manufacture of solar cells are generally needed.

[0006] BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figures 1A to 1H Cross-sectional views illustrating various operations in a method of fabricating a solar cell.

[0008] Figure 2 An exemplary workflow for constructing a solar cell is shown.

[0009] Figure 3A and Figure 3B A digital image containing a cross-sectional view of a solar cell.

[0010] FIG. 4A to FIG. 4C A cross-sectional view of a solar cell is shown.

[0011] Figure 5 shows a cross-sectional view of a solar cell,

[0012] Figure 6 A digital image containing a cross-sectional view of a solar cell.

[0013] Fig. 7A shows a cross-sectional view of a solar cell,

[0014] FIG. 7B to FIG. 7D Each shows a plan view of a solar cell.

[0015] FIG. 8A to FIG. 8C A side view of a solar cell is shown.

[0016] 9A to 9D is a digital image of various operations in a method of manufacturing a solar cell.

[0017] Fig. 10A and Fig. 10B is a digital image of various operations in a method of manufacturing a solar cell.

[0018] FIG. 11A to FIG. 11E Exemplary substrates manufactured using the methods, means or apparatus described herein are shown. DETAILED DESCRIPTION

[0019] The following specific embodiments are merely exemplary in nature and are not intended to limit the application and use of these embodiments or such embodiments. As used herein, the word "exemplary" means "used as an example, instance or illustration". Any embodiment described herein as exemplary is not necessarily preferred or advantageous over other embodiments. In addition, it is not intended to be bound by any express or implied theory presented in the aforementioned technical field, background technology, summary of the invention or the following specific embodiments.

[0020] References to the phrase "one embodiment" or "an embodiment" are not necessarily to the same embodiment. The particular features, structures, or characteristics may be combined in any suitable manner consistent with the present disclosure.

[0021] Terminology. The following paragraphs provide definitions and / or context for terms found in this disclosure (including the appended claims):

[0022] "Region" or "portion" describes a discrete area, volume, portion, or location of an object or material that has definable characteristics but not necessarily fixed boundaries.

[0023] “Comprising” is an open term and does not exclude other structures or steps.

[0024] "Configured to" refers to a structure by indicating a device, such as a unit or component, including a structure that performs one or more tasks during operation, and such structure is configured to perform the task even if the device is not currently in operation (e.g., not turned on / activated). A device "configured to" perform one or more tasks is expressly intended not to invoke the interpretation of 35 U.S.C. § 112(f) (i.e., the sixth paragraph) as a method or step plus function.

[0025] The terms "first", "second", etc. are used as labels for the nouns that follow them and do not imply any type of order (e.g., spatial, temporal, logical, etc.). For example, reference to a "first" solar cell does not necessarily mean that such solar cell is the first solar cell in a sequence; rather, the term "first" is used to distinguish such solar cell from another solar cell (e.g., a "second" solar cell).

[0026] Unless expressly stated otherwise, "coupled" means that an element, feature, structure or node is directly or indirectly joined or communicates with or can be directly or indirectly joined or communicated with another element, node or feature, and not necessarily directly mechanically joined together.

[0027] "Prevent / inhibit" describes reducing, diminishing, minimizing, or effectively or physically eliminating something, such as completely avoiding a result, outcome, or future state.

[0028] "Exposure to a laser beam" describes the process of subjecting a material to incident laser light and is used interchangeably with "subjecting to laser light," "treating with laser light," and other similar phrases.

[0029] "Doped regions," "semiconductor regions," and similar terms describe regions of semiconductor disposed in, on, over, or on a substrate. Such regions may have N-type conductivity or P-type conductivity, and the doping concentration may vary. Such regions may refer to multiple regions, such as a first doped region, a second doped region, a first semiconductor region, a second semiconductor region, and the like. These regions may be formed from polysilicon on the substrate, or may be part of the substrate itself.

[0030] "Thin dielectric layer", "tunneling dielectric layer", "dielectric layer", "thin dielectric material" or intermediate layer / material refers to a material on a semiconductor region, between a substrate and another semiconductor layer, or between doped regions or semiconductor regions on or in a substrate. In a certain embodiment, the thin dielectric layer can be a tunneling oxide or nitride layer having a thickness of about 2 nanometers or less. A thin dielectric layer can refer to a very thin dielectric layer through which electrical conduction can be achieved. The conduction can be attributed to quantum tunneling and / or the presence of smaller regions that are directly physically connected through thin points in the dielectric layer. Exemplary materials include silicon oxide, silicon dioxide, silicon nitride, and other dielectric materials.

[0031] "Intermediate layer" or "insulating layer" describes a layer that provides electrical insulation, passivation, and suppression of light reflectivity. The intermediate layer can be several layers, such as a stack of intermediate layers. In some contexts, the intermediate layer can be interchangeable with a tunneling dielectric layer, while in other contexts, the intermediate layer is a masking layer or "anti-reflective coating layer" (ARC layer). Exemplary materials include silicon nitride, silicon oxynitride, silicon oxide (SiOx), silicon dioxide, aluminum oxide, amorphous silicon, polycrystalline silicon, molybdenum oxide, tungsten oxide, indium tin oxide, tin oxide, vanadium oxide, titanium oxide, silicon carbide and other materials and combinations thereof. In a certain example, the intermediate layer may include a material that can act as a moisture barrier. Moreover, for example, the insulating material can be a passivation layer for a solar cell. In a certain example, the intermediate layer can be a dielectric double layer, such as silicon oxide (SiOx) (e.g., with a high hydrogen content), aluminum oxide (Al2O3) dielectric double layer.

[0032] "Locally deposited metal" and "metal deposition" are used to describe the formation of metal areas by exposing a metal source to a laser that forms and / or deposits metal from the metal source onto portions of a substrate. This process is not limited to any particular theory or mechanism of metal deposition. In a certain example, locally deposited metal can be formed when a metal foil is exposed to a laser beam that forms and / or deposits metal from a metal foil (such as all metal foils exposed to the laser beam) onto portions of a silicon substrate. This process may be referred to as "laser assisted metallization patterning" or LAMP technology. The locally deposited metal can have a thickness of 1 nanometer (nm) to 20 micrometers (μm), a width approximately defined by the laser beam size, and physical and electrical properties that match those of the source metal foil.

[0033] "Patterning" refers to a process that facilitates separation or isolation of portions of source metal, and may specifically refer to weakening areas of metal foil between the bulk of the metal foil and deposited areas of the metal foil (i.e., deposited metal). This patterning may be the result of heating, perforating, deforming, or otherwise manipulating the metal foil by the same laser process, LAMP, that deposited the metal foil onto the substrate, and may facilitate the removal of a large portion of the metal foil (i.e., undeposited metal foil) from the resulting device. References to LAMP include such patterning unless otherwise specified.

[0034] "Substrate" may refer to, but is not limited to, a semiconductor substrate such as silicon and specifically such as a monocrystalline silicon substrate, a polycrystalline silicon substrate, a wafer, a silicon wafer, and other semiconductor substrates for solar cells. In one example, such substrates may be used in microelectronic devices, photovoltaic cells or solar cells, diodes, photodiodes, printed circuit boards, and other devices. These terms are used interchangeably herein. The substrate may also be glass, a polymer layer, or another material.

[0035] "About" or "approximately." As used herein, with respect to recited values, including, for example, integers, fractions, and / or percentages, the term "about" or "approximately" generally means that the recited value encompasses a range of values ​​(e.g., + / - 5% to 10% of the recited value) that one of ordinary skill in the art would consider equivalent to the recited value (e.g., performing substantially the same function, acting in substantially the same manner, and / or having substantially the same results).

[0036] In addition, certain terms may be used in the following description for reference purposes only, and therefore, these terms are not intended to be limiting. For example, terms such as "upper", "lower", "above", and "below" refer to directions provided for reference in the accompanying drawings. Terms such as "front", "back", "rear", "side", "outer", and "inner" describe the orientation and / or position of certain portions of a component within a consistent but arbitrary reference system, which can be clearly understood by reference to the text describing the component in question and the related drawings. Such terms may include the words specifically mentioned above, their derivatives, and words of similar meaning.

[0037] As described in further detail below, aspects of the present disclosure are directed to improving solar cell conversion efficiency and / or reducing manufacturing costs by providing new processes for manufacturing solar cell structures.

[0038] Local metallization of substrates (e.g., semiconductor substrates) using laser beams, and the resulting structures, such as microelectronic devices, semiconductor substrates, and / or solar cells, are described herein. According to one or more examples of the LAMP technique, metal for conductor contacts is efficiently deposited and patterned, and the process can be completed in one operation with a laser. In an exemplary process, a metal foil (as a metal source) is placed over the surface of a substrate (such as a semiconductor solar cell), and portions of the metal foil are exposed to a laser beam to generate local high-density plasma and heat for local metal deposition while patterning the source metal foil (source metal layer).

[0039] After the deposition and patterning process, the residue of the source of the metal layer can be removed in the subsequent process. For example, the portion of the metal foil that is not exposed to the laser beam is removed (i.e., the undeposited metal foil is removed). In another example, the portion of the metal foil is exposed to a laser beam (such as another laser beam) applied subsequently and / or is exposed to a laser with different properties (e.g., power, frequency, etc.). The subsequent processing can provide further patterning of the metal foil so as to remove the undeposited metal foil. In some embodiments, the LAMP technique is repeated on the substrate in continuous steps to form a metal layer on the substrate. Specifically, the first foil is subjected to the first LAMP technique to form a first conductive contact structure on a first portion or region of the substrate, and the second foil is subjected to the second LAMP technique on a second portion or region of the substrate. The second LAMP technique can occur after the portion of the first foil that is not subjected to the first LAMP technique is removed, and these second portions or regions can be located on the substrate region where these portions of the first foil are removed. Similarly, the portion of the second foil that is not subjected to the second LAMP technique can be removed, and the third, fourth, etc. are similar. The LAMP technique can be continuously performed to form a metal layer on the substrate. This embodiment may be used in instances where the portion of the foil to be removed is difficult to remove due to its shape or proximity to other features on the substrate, such as metal features.

[0040] Without being bound by theory, the above-described localized metal deposition achieved by exposing the metal foil to a laser beam can be achieved by partial or complete melting of the laser irradiated portion of the metal foil, by partial or complete ablation of the metal foil portion that is subsequently redeposited on the wafer surface, and / or by laser sputtering of the metal foil portion during the laser deposition and patterning process of the metal foil. In a certain example, a first portion of the metal foil is exposed to a laser beam and subsequently deposited on the wafer surface while the source metal foil layer is patterned. In addition, certain embodiments cause the first portions of these metal foils to be fully or at least partially connected to an adjacent second portion of the metal foil that has not been exposed to laser irradiation. The region of the metal foil between the first portion and the second portion may have a relatively weakened physical structure (compared to the second portion) that promotes separation of the second portion from the first portion to produce a discrete conductive path.

[0041] Conventional metal deposition and patterning of metal layers for solar cells may include metal deposition using a vacuum chamber or metal plating using a chemical bath. One or more patterning operations are also typically performed to determine areas where deposited metal needs to be removed. In contrast, the disclosed metallization method effectively achieves metal deposition and patterning in a single process operation, thereby eliminating or eliminating the need for previously required processes. However, in addition to conventional metal deposition (e.g., after this), LAMP technology can also be used.

[0042] Several embodiments discussed herein can provide metallization that is lower in cost and faster than using optical lithography (and omitting the associated etching process), as well as potentially more accurate patterning with smaller feature widths and higher aspect ratios than screen printing. LAMP technology is capable of directly depositing metal and patterning metal on a substrate by laser using inexpensive metal foil in a single operation process, and presents a significant cost advantage over competing technologies. LAMP technology is also capable of manufacturing relatively small features. Specifically, tighter spacing and higher efficiency can be achieved compared to structures that are usually formed using screen printing. In a certain example, the conductive contacts of screen printing may include a silver paste having a thickness of up to 50 microns and a minimum feature size of 50 microns. In contrast, LAMP technology can produce a thickness of about 1 nanometer to 20 microns and a minimum feature size of about 25 microns. The deposition thickness can be controlled by the starting thickness of the source material and the laser conditions. The deposition thickness can be in the range of about 5% to about 25% of the thickness of the source material. The thickness of the source material partially limits the laser conditions (especially pulse duration) required for LAMP. The thickness of the source material partially limits the laser conditions (particularly the pulse duration) required for LAMP. In one embodiment, the thickness of the metal source material may be in the range of about 1 nm to 1 μm. In a certain example, performing a laser-assisted metallization process (LAMP) may include sputtering a metal in a thin source material onto a thin polymer or film using a picosecond laser or a femtosecond laser, wherein the thickness of the thin source material may be in the range of about 1 nm to 1 μm. In a certain embodiment, the thickness of the metal source material may be in the range of 1 μm to 100 μm, such as in the range of 1 μm to 10 μm, 5 μm to 25 μm, 10 μm to 50 μm, 25 μm to 75 μm, or 50 μm to 100 μm. In a certain example, performing a laser-assisted metallization process (LAMP) may include sputtering a metal in a metal foil onto a substrate using a picosecond laser or a femtosecond laser, wherein the thickness of the metal foil may be in the range of about 1 μm to 100 μm. In various embodiments of the LAMP technology, metal thickness parameters before and after LAMP as described in Table 1 are disclosed.

[0043] Table 1

[0044]

[0045] Other advantages include providing a viable method to replace the use of silver with lower cost aluminum (in the form of aluminum foil) for metallization of semiconductor features. In addition, the aluminum deposited using the LAMP technique can be a pure monolithic metal compared to screen-printed silver, which has a higher resistance due to its porosity. In addition to the examples of Table 1, in various examples using aluminum as the metal foil, the solar cell can have one (or more) aluminum layers with a thickness of about 1 nm to 500 μm. The metal foil can include aluminum in an amount greater than about 97% and silicon in an amount ranging from about 0 to 2%.

[0046] The thickness of an exemplary aluminum (Al) metal foil is approximately in the range of 1-100 μm, such as in the range of 1-15 μm, 5-30 μm, 15-40 μm, 25-50 μm, 30-75 μm or 50-100 μm. The Al metal foil may be a tempered grade metal foil, such as but not limited to F grade (free state), O grade (all soft), H grade (strain hardened) or T grade (heat treated). The aluminum metal foil may or may not be anodized and may include one or more coatings. Multilayer metal foils may also be used. Exemplary metal foils include metal foils of aluminum, copper, tin, tungsten, manganese, silicon, magnesium, zinc, lithium and combinations thereof, with or without aluminum in a stacked layer or as an alloy.

[0047] In another example, the operation of forming a metal and patterning a metal layer for a semiconductor device (e.g., a solar cell) can include first forming a first metal layer on a substrate (e.g., a metal seed layer) by conventional or LAMP techniques, positioning a second metal layer (such as aluminum foil) on the first metal layer, and bonding a portion of the first metal layer to the second metal layer, for example, using a laser. The metal seed layer can include a deposited tin, tungsten, titanium, copper, and / or aluminum layer. The metal seed layer can be deposited using a sputtering process. The thickness of the metal seed layer can be in the range of 0.05 to 50 μm.

[0048] LAMP technology is applicable to interdigitated back contact (IBC) solar cells and other types of solar cells, including: continuous emitter back contact solar cells, front contact and / or back contact solar cells with trench architecture (e.g., where doped regions are separated by trenches / gaps or intrinsic regions), thin films, heterojunction with intrinsic thin layers (HIT) solar cells, tunnel oxide passivated contact (TOPCon) solar cells, organic solar cells, front contact solar cells, front contact cells with overlapping cells or subcells (e.g., shingled super cell solar cells), passivated emitter and rear cell (PERC) solar cells, single PERC solar cells, passivated emitter with rear local diffusion (PERL) cells, 3 or 4 terminal tandem cells, laminates, and other types of solar cells. LAMP technology is also applicable to solar cells with multiple subcells coupled by metallization structures (sometimes referred to as multi-diode structures). For example, grooves separate adjacent subcells and metallization (such as foil) connects adjacent subcells together. The grooves may be formed by laser scribing and subsequently cleaved to separate and physically separate one subcell from another subcell, thereby forming one or more adjacent subcells from a common original solar cell. The subcells may be physically and electrically connected by a metallization structure, wherein the metallization structure may be located above the grooves and across the gaps formed by the grooves.

[0049] An exemplary method of manufacturing a solar cell includes forming an intermediate layer, such as an anti-reflective coating (ARC) layer, on or above a substrate (on the front surface and / or the back surface). The intermediate layer may have openings or holes that expose a portion of the substrate. A metal foil may be located above the intermediate layer, and in some instances, the metal foil appears to float above the substrate. The metal foil may be exposed to a laser beam above, partially above, offset from, and / or adjacent to the openings in the intermediate layer. Exposing the metal foil to the laser beam forms a plurality of conductive contact structures electrically connected to the lower region of the substrate. Each conductive contact structure includes a locally deposited metal portion electrically connected to the substrate. In an instance of a back contact, the conductive contact structure is located on the back side, while an instance of a front contact has a conductive contact structure located on both the front and back sides. LAMP technology may be used for one or both faces. The intermediate layer may be formed on and / or above the substrate, covering the entire front and / or back surfaces of the substrate.

[0050] An exemplary metal foil is a continuous sheet of metal that can cover the entire substrate, including one or more openings in the middle layer, and extend beyond all edges of the substrate. In another example, the metal foil covers only a portion of the substrate, such as a portion including one or more openings in the middle layer. In this example, the width of the metal foil can be relatively narrow and is considered a metal strip. For the purposes of this disclosure, the metal strip is considered a metal foil.

[0051] The solar cell may include a patterned backplane, an encapsulant, and / or a colored (dyed) back encapsulant. The metal foil may be hidden in the gap region between adjacent solar cells (across the gap between them) using a masking or concealing material (such as a tape), which is placed between the edge of the solar cell and the metal foil. The metal foil may also be anodized or otherwise colored to match the solar cell so that it is not easily visible or distinguishable from the solar cell when viewed from the front (i.e., the metal foil is masked or concealed). The metal foil may also include an adhesive, such as to adhere the metal foil to a substrate for pre-LAMP processing and / or post-LAMP processing. Alternatively or in addition, the substrate includes an adhesive to fix the metal foil for pre-LAMP processing and / or post-LAMP processing. A dielectric material, such as a damage buffer material (DBM) or an oxide material may also be disposed between the substrate and the metal foil.

[0052] A positioning process may be performed to hold the metal foil in place on / over the substrate using a vacuum and / or tacking process to position or secure the metal foil to the substrate. The positioning process may include hot pressing, where rollers and / or heat may be used to position or secure the metal foil over the substrate. A vacuum process, hot pressing process, or other similar process may also be used to uniformly position the metal foil and prevent air gaps or air pockets between the metal foil and the substrate.

[0053] In one example, the power, wavelength and / or pulse duration of the laser used for the LAMP technique is selected so that multiple locally deposited metal portions are formed, but the foil is not completely ablated. The power, wavelength and / or pulse duration can be selected / adjusted based on the composition, melting temperature and / or thickness of the metal foil. In one example, the laser has a wavelength between about 250 nm and about 2000 nm (such as 250 nm to 300 nm, 275 nm to 400 nm, 300 nm to 500 nm, 400 nm to 750 nm, 500 nm to 1000 nm, 750 nm to 1500 nm, or 1000 nm to 2000 nm), and the laser peak power is higher than 5x10-4 W / mm2, and the laser is a pulsed laser with a pulse frequency of about 1kHz and about 10MHz (such as about 1kHz and about 10MHz, such as 1kHz to 1000kHz, 500kHz to 2000kHz, 1000kHz to 5000kHz, 2000kHz to 7500kHz or 5000kHz to 10mHz. The pulse duration can be between 1fs and 1ms, such as 1fs to 250fs, 100fs to 500fs, 250fs to 750fs, 500fs to 1ns, 750fs to 100ns, 1ns to 2 The laser beam may have a width of about 20 μm to about 50 μm, such as 20-30 μm, 25-40 μm, and 30-50 μm.

[0054] In a certain example, a non-locally deposited portion of the metal foil is removed from a portion of the metal foil deposited on a substrate, which may result in the locally deposited portion of the metal foil having edge features, such as edge features formed by physically separating, destroying or tearing a bulk metal foil that has not been subjected to the LAMP technique. The edge features may include torn edges or sharp torn edges. In a certain example, a first portion of a metal (in this example, an aluminum foil) is deposited or directly fixed to the surface of a solar cell by the LAMP technique, while a second portion of the metal (which is adjacent to the first portion) is not subjected to the LAMP technique and is not deposited or directly fixed to the surface of the solar cell. The first and second portions of the metal foil are attached to each other, and the region between them may be patterned to weaken the region, preferably using the same LAMP technique in the same process step of depositing the first portion. The second portion is removed and physically separated or torn from the first portion, resulting in an edge structure along the side of the first portion. The edge structure or feature may be sharp and / or torn in appearance, and is distinguished from the rounded or curved edges of the metallized features left behind due to welding, brazing, plating or otherwise depositing the metal to the substrate. These edge structures can also be polished to remove sharp or rough features in subsequent steps.

[0055] Exposure of the foil to a laser beam may also form other unique features compared to conventional metallization methods, including the formation of a "U-shaped" structure or valley where the laser beam has contacted the foil. The width of the "U-shape" is approximately equal to the width of the laser beam used. In a certain embodiment, the conductive contact structure is at least temporarily connected by extending from the conductive contact structure to the edge portion of the area of ​​the metal foil that was not exposed to the laser beam until the area not exposed to the laser beam is removed.

[0056] In a certain example, exposing the metal foil to the laser beam forms a spatter or sputtering feature on the solar cell (e.g., on the foil and / or substrate). Such spatter features can be used to determine whether the solar cell is formed using the LAMP technique. In some examples, the spatter features can be removed from at least the metal foil, for example to facilitate bonding a second material to the foil, such as a carrier sheet for removing the foil that has not been exposed to the laser beam, or other components of the solar cell, solar cell string, or higher-order structure (such as an interconnect, a foil extending from another cell), or other electrically connected or non-electrically connected components of the solar cell, solar cell string, or higher-order structure. Such spatter can be removed by polishing or etching.

[0057] To increase the metal thickness (e.g., for conductivity or structural purposes) and to facilitate removal of undeposited portions of the first metal foil layer, the laser-assisted metallization can be repeated to build up a multi-layer metal foil structure. Specifically, a second metal source (such as a metal foil, wire, or ribbon) can be located above the first metal foil, wherein the second metal source can be subjected to a laser beam at selected locations above locations of the first metal foil that are not locally deposited (i.e., directly electrically connected) to the semiconductor region, thereby welding or bonding the second metal source to the first metal foil. The second metal source is then mechanically removed, thereby selectively removing areas of the first metal foil that are not locally deposited to the semiconductor region on the substrate.

[0058] Additionally, a second metal source is used to provide additional metallization thickness to all or part of the solar cell, such as for constructing busbars, where the additional metal thickness is beneficial for electrical conduction. Here, the second metal source can be bonded to the first metal foil by laser at selected locations on the first metal foil that are not locally deposited and / or at locations that are the same or approximately the same as where the first metal foil is locally deposited to the semiconductor region. The process can be limited to the interconnection area between adjacent solar cells, or applied to a string of adjacent solar cells.

[0059] In addition, a second metal source is located on a solar cell substrate that includes a locally metallized area or portion, such as an area or portion formed by a first metal foil or by conventional metallization techniques. The second metal source is bonded to the local metallization in selected areas to provide additional metallization in these selected areas. In a certain example, the second metal source is patterned so as to both increase the metal thickness in some areas and be used as a carrier sheet to remove non-locally deposited portions of the first metal foil in other areas. The second metal source can be bonded to the first metal foil using a tack welding process. The tack welding process includes forming an array of spot welds, which can be performed using lasers, hot compression bonding (e.g., by using spikes, spike rollers, needle rollers, or nail beds) or conventional soldering and welding techniques. The second metal source can also be bonded to the first foil using a conductive adhesive. In another embodiment, the carrier is a plastic, polymer, and / or film that can be used as an insulator, a moisture barrier, a protective layer, etc.

[0060] Figures 1A to 1D Cross-sectional views of an exemplary solar cell are shown at various operational steps in a method of fabricating the solar cell.

[0061] refer to Figure 1A, an intermediate layer 102 is formed on or over a solar cell substrate 100. The intermediate layer 102 has an opening 104 therein. Although specific reference is made to forming the intermediate layer on or over a substrate, it should be understood that the above directions are relative and that the intermediate layer can be formed on the back side, front side, or even back side and front side of a selected substrate, for example, for metallization of the front side, back side, or front side and back side of a substrate.

[0062] The intermediate layer 102 is formed with the opening 104 (e.g., patterned by deposition), or the opening 104 is formed in a blanket deposited intermediate layer. In the latter case, in one embodiment, the opening 104 is formed in the intermediate layer 102 by patterning using laser ablation and / or photolithography and etching processes.

[0063] The intermediate layer 102 may be formed on the back side of the substrate 100 opposite to the light receiving surface 101 of the substrate 100. A passivation layer and / or an intermediate layer (eg, ARC) may also be formed on the back side of the substrate 100. Specifically, the intermediate layer 102 may be a back side anti-reflection layer (BARC).

[0064] The light receiving surface 101 may have a textured light receiving surface. A hydroxide-based wet etchant may be used to texture the light receiving surface 101 of the substrate 100. A textured surface is a surface having a regular or irregular shape that is used to scatter incident light and reduce the amount of light reflected away from the light receiving surface 101 of the solar cell. A passivation and / or insulation (e.g., ARC) layer may be formed on the light receiving surface 101.

[0065] Although the present disclosure is primarily directed to back-contact solar cells, the methods and techniques discussed herein, particularly the LAMP technology, can be applied to the metallization of substrates in other solar cell types, such as front-contact solar cells (e.g., PERC solar cells, single PERC solar cells, HIT solar cells, TopCon solar cells, PERL cells and tandem cells, as well as other types of solar cells).

[0066] The opening 104 in the intermediate layer 102 can expose portions of a plurality of semiconductor regions formed in or above the substrate 100, including portions of a plurality of first semiconductor regions and second semiconductor regions (e.g., N-type and P-type semiconductor regions, and vice versa) formed in or above the substrate 100. The substrate 100 can include a single crystal silicon substrate, such as a bulk single crystal N-type doped silicon substrate, or a layer disposed on a single crystal solar cell substrate, such as a polycrystalline silicon layer. The substrate 100 can have N-type doped regions and P-type doped regions disposed therein / on it, portions of which are exposed by the opening 104 in the intermediate layer 102. In front contact solar cell embodiments, the semiconductor regions on one side of the solar cell can have the same conductivity type (e.g., P-type or N-type).

[0067] N-type and / or P-type semiconductor regions may be disposed on a dielectric layer, such as a tunnel oxide layer including silicon oxide having a thickness of about 2 nanometers or less. The N-type and / or P-type semiconductor regions may be formed of polysilicon, which is formed, for example, by a plasma enhanced chemical vapor deposition (PECVD) process. The N-type polysilicon emitter region may be doped with N-type impurities such as phosphorus, and the P-type polysilicon emitter region may be doped with P-type impurities such as boron. In a certain embodiment, the N-type and P-type semiconductor regions are separated from each other. In a certain example, the N-type and P-type semiconductor regions have a trench or an intrinsic (or lightly doped) region formed between them. The trench may extend partially into the substrate and may be covered by the intermediate layer 102. The doping concentration of the lightly doped region may be substantially less than that of the N-type and P-type semiconductor regions. A dielectric layer, such as a tunnel oxide or silicon dioxide layer, may be located between the N-type and P-type semiconductor regions and the substrate 100, and may be located laterally between the N-type and P-type semiconductor regions.

[0068] refer to Figure 1B , the metal foil 106 is located on the intermediate layer 102. In a certain embodiment, positioning the metal foil 106 on the intermediate layer may include positioning the metal foil on the substrate 100. In a certain example, positioning the metal foil 106 on the substrate 100 may include covering the entire substrate 100. In a certain embodiment, a portion of the metal foil 106 may be located on the substrate 100, while other portions may be located away from the substrate 100, for example, extending away from the substrate in a lateral direction, such as Figure 1BAs shown. In a certain embodiment, in order to fix the metal foil 106 and the substrate 100, a positioning process can be performed, including using a vacuum and / or a positioning welding process to keep the metal foil 106 in a suitable position on the substrate 100. In a certain example, the positioning process includes performing a hot pressing process. In another example, a roller can be used to place or position the metal foil 106 on the substrate 100. In a certain embodiment, as shown in the figure, a vacuum process, a hot pressing process or other similar processes can evenly place the metal foil to prevent air gaps or air pockets between the metal foil and the substrate. In a certain example, a roller can be used to evenly place the metal foil 106 on the substrate 100.

[0069] The metal foil 106 may have a surface area substantially greater than the surface area of ​​the solar cells when the metal foil 106 is positioned over the substrate 100. However, in another embodiment, before the metal foil 106 is placed over the solar cells, the large foil may be cut to provide the metal foil 106 with a surface area substantially the same as the surface area of ​​the substrate 100. For example, the metal foil may be laser cut, water jet cut, etc., before or even after the metal foil is placed on or over the substrate 100.

[0070] In a certain embodiment, the metal foil 106 is an aluminum (Al) foil having a thickness in the range of about 5-100 microns. In one embodiment, the Al foil is an aluminum alloy foil including aluminum and a second element such as, but not limited to, copper, manganese, silicon, magnesium, zinc, tin, lithium, or a combination thereof. In one embodiment, the Al foil is a tempered grade foil such as, but not limited to, grade F (free state), grade O (fully soft), grade H (strain hardened), or grade T (heat treated). In one embodiment, the aluminum foil may be an anodized aluminum foil. In another embodiment, the aluminum foil is not anodized.

[0071] refer to Figure 1C , the metal foil 106 can be exposed to the laser beam 108 in a position above the opening 104 in the intermediate layer 102, thereby exposing a portion of the semiconductor region in or above the substrate 100. In a certain embodiment, a region of the metal foil 106 is selectively exposed to the laser beam 108 in a position at least partially above the opening 104 in the intermediate layer 102. In some embodiments, the metal foil 106 is exposed to the laser beam 108 in a position offset from (e.g., partially above or not above) the opening 104 in the intermediate layer 102. In a certain example, the metal foil 106 is exposed to the laser beam 108 in a position adjacent to the opening 104.

[0072] refer to Figure 1D , exposing the metal foil 106 to a laser beam 108 forms a plurality of conductive contact structures 110 , which are electrically connected to semiconductor regions in or above the substrate 100 .

[0073] According to one or more embodiments of the present disclosure, each conductive contact structure 110 is or includes a locally deposited metal portion. In one such embodiment, the metal foil 106 acts as a source or metal, and is referred to as a local source because the metal foil 106 is first placed on the substrate surface. The metal foil 106 is then exposed to a laser process, such as a laser beam, which deposits the metal in the metal foil 106 (metal source) onto a portion of the substrate. It should be understood that the resulting locally deposited metal portion may have edge features that can be distinguished from metal structures formed by other deposition processes such as plating, fusion welding, or thermal bonding, which can provide conformal structures without edge features.

[0074] Reference again Figure 1D , a second portion 112 or portion 114 of the metal foil 106 not exposed to the laser beam 108 remains on the intermediate layer 102. As depicted, portion 112 is a central portion, while portion 114 is an edge portion and may be an overhanging portion. In certain embodiments, such second portions are not deposited or fixed to the solar cell or intermediate layer 102. In a certain embodiment, Figure 1D The structure can be implemented as a solar cell without removing portions 112 and / or 114 of metal foil 106. This structure can be used for back surface metallization of front contact solar cells. In addition, a second metal source can be bonded / attached to portions 112, 114, such as Figure 1E The overhanging portion of the edge portion 114 can be used to couple to another solar cell to form a solar cell string, see for example Figure 1F It should be understood that Figure 1D 114 in the figure may extend to the side of the wafer so as to be connected to a bus bar inside or outside the page (for example, considering that 110 and 112 extend inside or outside the page, and the bus bar can be connected to these parts). Referring again to Figures 1A to 1F The described process may be repeated with a continuous foil to form conductive contact structures on different portions of the substrate, such as a second, third, etc. portion or region of the substrate, each of which is a discrete area on the substrate.

[0075] refer to Figure 1E, the second metal source 115 can be located on the substrate 100. The second metal source can include a metal foil, a wire or a strip. As shown, the second metal source 115 can be patterned, such as pre-patterned, and is located on the portions 112, 114. In some instances, after the second metal source 115 is placed on the portions 112, 114, the second metal source can be positioned as a sheet and patterned. A bonding process can be performed to bond the second metal source to the portions 112, 114. In a certain instance, the second metal source 115 can be subjected to a laser beam in a selected position on the portions 112, 114, for example, a welding process is performed to bond the second metal source 115 111 to the portions 112, 114. In some instances, attaching the second metal source 115 can include applying a conductive adhesive, tacking, stamping and / or any other similar attachment type process to connect the second metal source 115 to the portions 112, 114. In one example, the second metal source 115 can be bonded 111 to both portions 112. In some examples, the second metal source 115 can be bonded 111 to portions 112 or 114. Additionally, in some embodiments, the second metal source can be positioned and / or bonded to Figure 1D A metal foil 106 is shown. A semiconductor region 105 is also shown.

[0076] refer to Figure 1F ,from Figure 1D Enter the side view of the page 90 °, which shows a solar cell string 167. As shown, the edge portion 114 can also be called an interconnection portion, which can electrically connect one solar cell to another solar cell. In one example, coupling a solar cell to another solar cell in this way can form a solar cell string, thereby realizing a parallel or series electrical relationship between the cells. In a particular embodiment, the overhang portion can represent a foil portion that is large enough to overlap with one or more additional cells for metallization of the one or more additional cells. In a certain example, a single piece and / or a single foil can be used for multiple solar cells (e.g., 2, 3 or more solar cells) in this way. In a certain embodiment, two or more batteries can be connected together by their respective edge portions 114. For example, the edge portions 114 of adjacent batteries can be connected at 116 by various processes, such as by bonding (e.g., welding) and / or including conventional and laser bonding, laser welding, thermocompression bonding, brazing processes, etc. In another example, the substrate 100 can have a separate edge portion 114. These individual edge portions 114 can be bonded and / or welded together to electrically connect one substrate to another substrate, for example, to form a solar cell string. In some examples, the individual edge portions 114 can be attached together using a conductive adhesive, a tacking process, a stamping process, and / or any other type of suitable attachment process.

[0077] refer to Figure 1G , which schematically shows the location of the semiconductor region 105. In a certain embodiment, as shown in the figure, the semiconductor region may include multiple semiconductor regions, such as a first semiconductor region, a second semiconductor region, etc. In a certain example, the first semiconductor region may be an N-type semiconductor region and the second semiconductor region may be a P-type semiconductor region. In some examples, the semiconductor region 105 may have the same conductivity type as that in some front-contact solar cells, for example, all N-type or P-type. In a certain embodiment, the semiconductor region 105 may include polycrystalline silicon. A thin dielectric layer, such as a tunnel oxide layer, may be disposed between the semiconductor region 105 and the substrate 100.

[0078] like Figure 1G As shown, the semiconductor regions 105 are laterally separated from each other by regions 119. The regions 119 may be gaps, intrinsically doped regions, or lightly doped regions. Two openings for each semiconductor region 105 in the intermediate layer 102 are shown for connecting the conductive contact structure 110 to the semiconductor region 105. The portion 112 electrically connects the conductive contact structure 110 to each semiconductor region 105. In other words, the portion 112 on the left electrically connects the two leftmost conductive contact structures 110, while the portion 112 on the right electrically connects the two rightmost conductive contact structures 110. In a specific example, the semiconductor regions 105 are N-type and / or P-type semiconductor regions and are separated by trenches formed between them, which partially extend into the substrate and are covered by the intermediate layer 102. The separation may also be achieved by lightly doped regions 119, wherein the doping concentration of the lightly doped regions may be substantially lower than that of the N-type and / or P-type semiconductor regions. However, the semiconductor regions 105 may have the same conductivity type as in some front-contact solar cells, i.e., all N-type or P-type. Portions 114 are edge portions and may be overhanging portions that may be used to couple to another solar cell.

[0079] refer to Figure 1H , which schematically shows the location of the semiconductor region 104. In one embodiment, as shown in the figure, the semiconductor region 104 may include a portion of the substrate 100 itself. Figure 1G , semiconductor region 104 may include multiple semiconductor regions: a first semiconductor region, a second semiconductor region, etc., which may be N-type semiconductor regions and P-type semiconductor regions. In some examples, semiconductor region 104 may have the same conductivity type as that in some front-contact solar cells, for example, all N-type or P-type.

[0080] Reference again Figure 1G and Figure 1H, the second metal source can be bonded and / or attached to the portions 112, 114. The second metal source can include metal foil, wire, or tape. In an example, the bonding and / or attachment can include welding, laser, soldering, conductive adhesive, tack welding, stamping, and / or any other similar bonding / attachment.

[0081] Figure 2 1100 is a flowchart representing various operations in a method of manufacturing a solar cell. Optionally, at operation 1102, a plurality of semiconductor regions are formed in or above a substrate. At operation 1104, an intermediate layer is formed above the substrate. In a certain example, the intermediate layer may have openings that expose portions of the substrate. These openings may be formed by laser ablation or etching. At operation 1106, a metal foil is positioned above the openings in the intermediate layer. At operation 1108, the metal foil is exposed to a laser beam to form a plurality of conductive contact structures electrically connected to the exposed portions of the substrate, and the metal foil is patterned. Optionally, at operation 1110, at least a portion of the metal foil is removed. Optionally or additionally, at operation 1112, a spatter feature is removed from the metal foil that is not exposed to the laser beam. Operation 1112 may be performed before operation 1110. Optionally or additionally, at operation 1114, a second metal source (such as a metal wire, foil or tape, conductive material) may be attached to the metal foil. The second metal source may be attached to the conductive contact structure described above with respect to operation 1108. Operation 1114 may be performed before operation 1110. Operation 1114 may be performed before or after operation 1112. The above operations may be repeated, for example, with successive foils.

[0082] An exemplary structure of the LAMP technique is shown in Figure 3A and Figure 3B Depicted in. Figure 3A and Figure 3B Digital image containing a cross-sectional view of a solar cell processed using LAMP technology. Figure 3A , the metal foil is exposed to a laser beam to form a plurality of conductive contact structures 110 or "locally deposited" metal portions electrically connected to a substrate 100, which may include a plurality of N-type and / or P-type semiconductor regions located in or above the substrate 100. Second portions or portions 112 of the metal foil are located on either side of the conductive contact structures 110, which portions are not locally deposited to the substrate 100. These portions 112 may remain on the intermediate layer 102 above the substrate. These portions 112 are as shown in FIG. Figures 1A to 1H The central portion is depicted. Conductive contact structure 110 may be connected at least temporarily until portion 112 is removed, leaving edge portion 121. Portion 112, edge portion 121, and conductive contact structure 110 form a U-shape. Although in this view, edge portions are shown, in some examples, edge portion 121 is not formed.

[0083] Since the portion 112 is not directly connected to the substrate 100, there is a gap 119 between the portion 112 and the substrate 100. Figures 1A to 1H The intermediate layer 102 is depicted covering the gap. Figure 3B As can be seen from the figure, Figure 3A As shown in the enlarged view of FIG. 1 , when the second portion or portion 112 is removed, the resulting conductive contact structure 110 or locally deposited metal portion may have edge features, such as sharp or torn edge features, leaving at least a portion on the edge portion 121. Such edge features may be distinguished from metal structures formed by other metal deposition processes, such as plating processes that may provide conformal structures without edge features.

[0084] Return to reference Figures 1A to 1H After exposing the metal foil 106 to the laser beam 108 , portions 112 and 114 of the metal foil 106 may be removed, and portion 112 may be selectively exposed to the laser beam. FIG. 4A to FIG. 4C An exemplary structure is depicted in .

[0085] FIG. 4A to FIG. 4C A cross-sectional view of a solar cell is shown. Figure 4A As shown, removing the second portion of the metal foil may leave conductive contact structures 110 at locations in the intermediate layer 102 that have exposed portions of a plurality of N-type and / or P-type semiconductor regions in or above the substrate 100. Figure 4B , the formation of sharp or torn edge features 113 on either side of the conductive contact structure 110 is shown. As described above, these edge features 113 are formed by removing the second portion of the metal foil that is not exposed to the laser beam. Figure 1C , Figure 1D , Figure 1E , Figure 1F , Figure 1G and Figure 1H In some embodiments, some portions 112 and 114 are removed while other portions 112 and 114 remain. In certain embodiments, exposing metal foil 106 to laser beam 108 includes removing all or substantially all portions of the metal foil that are not exposed to the laser beam.

[0086] Figure 4CThe positions of N-type and / or P-type semiconductor regions 105 are shown. In the illustrated embodiment, the N-type and / or P-type semiconductor regions 105 are separated from each other, and each semiconductor region has two conductive contact structures 110. Alternatives (not shown) include one, three or more conductive contact structures for each semiconductor region. In a certain example, the N-type and / or P-type semiconductor regions may have grooves formed between them, which extend partially into the substrate and are covered by the intermediate layer 102. In one example, the N-type and / or P-type semiconductor regions may be separated by intrinsic or lightly doped regions between them, for example, wherein the doping concentration of the lightly doped regions may be substantially lower than that of the N-type and / or P-type semiconductor regions. In some embodiments, the semiconductor region 105 may have the same conductivity type as that in some front-contact solar cells, i.e., all N-type or P-type. It is contemplated that, as described above, the conductive contact structure 110 may be enhanced with a second metal source as described.

[0087] Return to reference Figures 1A to 1G , after applying the laser beam 108 to the metal foil 106, in some instances, only portions 114 of the metal foil 106 that were not exposed to the laser beam 108 are removed, while portions 112 of the metal foil 106 remain. In some embodiments, the portions 112 may be selectively exposed to the laser beam 108 or to a different / subsequent laser beam, which may use the same laser at different laser settings / variations.

[0088] Figure 5 A cross-sectional view of a solar cell is shown. Figure 5 As shown, the laser forms a conductive contact structure 110 and a portion 112 above the intermediate layer 102, such as an ARC or BARC layer. Portion 114 has been removed. The location of the N-type and / or P-type semiconductor region 105. In one example, the N-type and / or P-type semiconductor regions are separated, for example, by a lightly doped region 197 between them, for example, wherein the doping concentration of the lightly doped region can be substantially lower than that of the N-type and / or P-type semiconductor region. In some embodiments, the semiconductor region 105 can have the same conductivity type as in some front-contact solar cells, i.e., all N-type or P-type. It is contemplated that, as described above, the conductive contact structure 110 can be enhanced with a second metal source as described. It is also contemplated that, as described above, portion 112 can be formed by a second metal source as described.

[0089] Figure 6is a digital image of a cross-sectional view of a solar cell after using the LAMP technique. The inset 109 in the upper left corner of the digital image shows the area of ​​the cut-away cross-sectional view of the solar cell, indicated by a circle. In this example, portions 112 of the metal foil 106 are retained. These portions 112 are portions of the metal foil 106 that were not exposed to the laser beam or were exposed to a laser beam with different properties (e.g., power, frequency, etc.). The portions 112 may also be exposed to different laser beams in subsequent process steps. In addition, as Figure 6 As shown, the laser forms a conductive contact structure 110 that can be a connecting portion 112, wherein the portion 112 is located above the substrate 100. In a certain embodiment, the portion 112 can carry current between the conductive contact structures 110. In a certain embodiment, exposing the metal foil to the laser beam can form a spatter feature 127 on the solar cell. Such spatter features can be used to determine whether the solar cell is formed using one or more of the laser-assisted metallization processes disclosed herein (e.g., as distinguished from welding or brazing processes). In addition, optionally, these spatter features on 112 can be removed by mechanical cleaning (such as a brush), or chemical cleaning, water jet processes, high-pressure air blowing processes, and mechanical grabbing and peeling can be used to completely remove the area 112. Figure 6 Further shown is a clear gap 119 between portion 112 and substrate 100, the intermediate layer (see FIG. Figures 1A to 1H The depicted intermediate layer 104) covers the gap. An edge portion 121 can also be seen in this view.

[0090] 7A to 7D An alternative embodiment is shown in which the metal foil forms a bus bar extending transversely to the conductive contact structure and conducts current across the conductive contact structure. Fig. 7A The busbars 117 extend transversely to the conductive contacts and contact the conductive contacts 110a, which contact the substrate 100 through the openings 104 in the intermediate layer 102. Figure 7B As shown in the plan view of FIG. 1 , the openings 104 may be in pairs, as shown (e.g., referring to FIG. Figure 1G , Figure 1H ). As shown, the conductive contact structure 131a can be connected to the bus bar 117, and the conductive contact structure 131b can be connected to the bus bar of opposite polarity (not shown). The finger electrodes 131a and 131b can also include a portion 112 of a metal foil, such as Figure 5 B. In general, 131a, 131b may include any of the exemplary metallization configurations presented herein. In one example, the metal deposition process may form an ohmic contact between the metal foil and the substrate. In one example, an ohmic contact may be formed between the bus bar 117 and the conductive contact structure 131a or 131b. It is contemplated that, as described with respect to 7A to 7D The described bus bars may be formed from a metal foil and / or a second metal source, as described above.

[0091] refer to Figure 7C The bus bar 117 may have an interconnection portion to electrically connect the bus bar 117 of one solar cell to the bus bar of another solar cell (not shown). The finger electrodes 131a and 131b may be localized deposition areas, such as described above. Figure 4A In one example, the metal deposition process may form an ohmic contact between the metal foil and the substrate. In one example, an ohmic contact may be formed between the bus bar 117 and the conductive contact structures 131a and / or 131b.

[0092] refer to Fig.7D ,and 7A to 7C Contrary to the situation shown, the bus bars (in this case, bus bars 117a and 117b) may optionally extend beyond the edge of substrate 100, as shown. Fig.7D As shown. In some instances, bus bars may be formed on either end of substrate 100, see, for example, bus bars 117a and 117b. In other embodiments, the solar cell may have one or more bus bars in the middle of the cell. Bus bars 117a and 117b may carry current between conductive contact structures 131a, 131b, respectively. In a certain embodiment, bus bars 117a and 117b may carry current without creating a large amount of resistance between conductive contacts 131a, 131b. In a certain instance, the metal deposition process may form an ohmic contact between the metal foil and the substrate. In a certain instance, an ohmic contact may be formed between bus bars 117a and 117b and conductive contact structures 131a and / or 131b.

[0093] FIG. 8A to FIG. 8C Additional examples of solar cells utilizing multi-diode technology are shown. Fig. 8A is a side view of a solar cell, wherein the conductive contact structure 110 extends along the length of the substrate 100 . Figure 8B A pair of subcells 125a and 125b are shown, where the conductive contact structure 110 can extend along approximately half of the length of the substrate 100. In some examples, the conductive contact structure 110 can extend along approximately 1 / 3, 1 / 4, 1 / 5, and / or any fraction of the length of the substrate 100. The conductive contact structure 110 can be as Fig. 8A125a and 125b. The metal foil 110 may be formed continuously as shown in FIG. 123 and then laser scribed or otherwise ablated at 123 to form two subcells 125a and 125b. The metal foil 110 may extend over the scribed or ablated portion 123 to electrically and / or mechanically bridge and / or connect the two subcells 125a and 125b. Alternatively, they may be formed as separate structures, for example, without the need for separate or ablated interconnect foils. Figure 8C is a side view of a solar cell, wherein a bus bar 117 extends transversely to the conductive contact structure 110 and conducts current across the conductive contact structure 110 .

[0094] In various embodiments discussed herein, removal of the second portion or portions of the metal foil that is desired to be removed can be accomplished by a mechanical process. The mechanical process can include peeling off the portions, thereby separating the second portion from the first portion by tearing or ripping. Laser ablation and chemical etching can also be used to remove the second portion.

[0095] 9A to 9D Contains images of various operations in a method of manufacturing a solar cell. Fig.9A In the first method, a metal source (e.g., a metal foil) is placed or positioned on the surface of a silicon wafer, and then the metal foil is deposited and patterned using a laser. That is, the metal in the metal foil is locally deposited onto the silicon wafer in locations corresponding to the laser scribing / patterning process. The metal can then be removed by a mechanical lift-off process such as Fig. 9B The foil that was not laser scribed (or subjected to the laser) is removed as shown. Fig. 9C and Fig.9D An enlarged view of a locally deposited metal portion disposed on a substrate is shown. 9A to 9D Described in more detail.

[0096] Fig.9A 406. The arrangement 400 may include a metal foil 402 placed or mounted on a silicon substrate 406. The portion of the metal foil 402 above the substrate 406 is exposed to a laser beam in a position where the opening in the intermediate layer exposes the underlying semiconductor region. A portion 404 of the metal foil 402 is not exposed to the laser beam. As depicted, a portion 407 of the metal foil 402 may overhang the silicon substrate 406. In some embodiments, the portion 404 may be exposed to another laser beam having different properties (e.g., power, frequency, etc.) at another step. The arrangement 400 may include a vacuum table to hold the substrate 406 in place and the metal foil 402 in place atop the substrate 406 to prevent air gaps or bubbles in the metal foil 402.

[0097] Fig. 9BPortion 404 of metal foil 402 is shown removed from substrate 406, for example, by a lift-off process. Specifically, excess portion 404 can be lifted off substrate 406. Portion 404 can be the portion of the metal that was not exposed to the laser, as described above. Portion 404 can also be exposed to another laser beam with different properties (e.g., power, frequency, etc.) to provide further patterning or ablation. The metal foil can also be removed by blowing (e.g., compressed air), spraying (e.g., using a high-pressure water jet process), applying an adhesive to portion 404 and pulling the adhered portion 404, or other metal removal methods.

[0098] Fig. 9C and Fig.9D Shows that in the removal Fig. 9B An exemplary resulting solar cell structure after portion 404 is shown. Fig. 9C and Fig.9D Conductive contacts including metal 410 (e.g., aluminum) are shown, which remain as a result of localized deposition (by exposing metal foil 402 to a laser beam) over openings 417 in an intermediate layer 412 of substrate 406. The locally deposited metal 410 is located over the intermediate layer 412, which may be disposed over substrate 406. The locally deposited metal 410 is located over, partially over, offset from, and / or adjacent to the openings in the intermediate layer 412. Fig. 9C As shown, the locally deposited metal 410 is partially over or offset from the contact openings in the intermediate layer 412 (ie, partially over or offset from the exposed openings 417 in the intermediate layer 412). Fig.9D Locally deposited metal 410 is shown aligned with and over contact openings in intermediate layer 412 (not shown because they are covered by metal 410). Fig. 9C and Fig.9D Metal 410 is shown partially deposited on both the intermediate layer 412 and the substrate 406 through the opening 417. The intermediate layer in such a structure can act as an insulator, so that a conductive path to the substrate is formed only through the opening 417. As used herein, "substrate" generally refers to the semiconductor region below the intermediate layer.

[0099] FIG. 10A to FIG. 10B are images of various operations in another method of manufacturing a solar cell using the LAMP technology.

[0100] Fig. 10A A portion 504A of the metal foil is shown removed from the substrate, with excess portion 504A peeling away from the substrate.

[0101] Fig. 10B Shown in Fig. 10AThe solar cell structure after removing the portion 504A of the metal foil 502. However, here, at 510 (e.g. Figure 1D A metal (eg, aluminum) is locally deposited by LAMP technology at the conductive contact structure 110 in FIG. 1 , and a portion 504B of the metal is not exposed to the laser beam but remains (eg, Figure 1D 112 in). These portions 504B not exposed to the laser do not pass the Fig. 10A On the other hand, these portions 504B remain on the intermediate layer between the regions 510 where metal has been removed. Subsequent processing may include exposing the portions 504B to a laser beam or another laser beam with different properties (eg, power, frequency, etc.).

[0102] It should be understood that Figures 1A to 10B Any of all structures shown in may represent a partially completed solar cell, respectively, as further processing may be performed. Alternatively, any of these structures show a completed solar cell.

[0103] FIG. 11A to FIG. 11E An exemplary semiconductor substrate manufactured using the methods, methods or devices described herein according to some embodiments is shown. The semiconductor substrate is a solar cell 1520a-e and may include a silicon substrate 1525. The silicon substrate 1525 may be cleaned, polished, planarized and / or thinned or otherwise processed. The semiconductor substrate 1525 may be a single crystal or multicrystalline silicon substrate, i.e., an N-type or P-type. The solar cell may have a front side 1502 and a back side 1504, wherein the front side 1502 is opposite to the back side 1504. The front side 1502 may be referred to as a light receiving surface 1502, and the back side 1504 may be referred to as a back surface 1504. The solar cell may include a first doped region 1521 and a second doped region 1522. In a certain embodiment, the first doped region may be a P-type doped region (e.g., doped with boron), and the second doped region may be an N-type doped region (e.g., doped with phosphorus). The solar cell 1520a-e may include an intermediate layer (e.g., an anti-reflective coating ARC) 1528 located on the front side 1502 of the solar cell. The solar cells 1520a-e may include a back side intermediate layer (eg, a back side anti-reflective coating (BARC)) 1526 on the back side 1504 of the solar cell.

[0104] Fig.11AAn exemplary back-contact solar cell manufactured using the methods, means or apparatus described herein is shown. The back-contact solar cell 1520a may include a first doped region 1521 and a second doped region 1522 disposed on the back side 1504 of the solar cell 1520a. In a certain example, the first doped region 1521 and the second doped region 1522 may be doped semiconductor regions. The first doped region 1521 and the second doped region 1522 may be doped polysilicon regions. A thin oxide layer 1573 (e.g., a tunnel oxide layer) may be disposed between the first doped region 1521 and the second doped region 1522 and the substrate 1525. The first doped region 1521 and the second doped region 1522 may alternatively be located in the substrate 1525. Conductive contact structures 1511, 1512 are located on the back side 1504 of the solar cell 1520a, wherein the conductive contact structures 1511, 1512 include metals deposited locally on the first doped region 1521 and the second doped region 1522. The first doped region 1521 and the second doped region 1522 may have a separation region 1577 formed therebetween. In one example, the first doped region 1521 and the second doped region 1522 have trenches formed therebetween, which partially extend into the substrate and are covered by the intermediate layer 1562. The trenches may be replaced by an intrinsic or lightly doped semiconductor region.

[0105] Fig. 11B Another example of a back-contact solar cell 1520b manufactured using the methods, means, or apparatus described herein according to some embodiments is shown. The back-contact solar cell 1520b may include a first doped region 1521 and a second doped region 1522 disposed on the back side 1504 of the solar cell 1520b. In a certain example, the first doped region 1521 and the second doped region 1522 may be doped semiconductor regions extending in a continuous layer. In one example, the first doped region 1521 and the second doped region 1522 are separated by a lightly doped region 1579 therebetween, wherein the doping concentration of the lightly doped region may be substantially less than that of the first doped region 1521 and the second doped region 1522. In a certain embodiment, a thin oxide layer 1573 (e.g., a tunnel oxide layer) may be disposed between the first doped region 1521 and the second doped region 1522 and the substrate 1525. In a specific embodiment, the first doped region 1521 and the second doped region 1522 may be doped polysilicon regions. The first doped region 1521 and the second doped region 1522 may alternatively be located in the substrate 1525. In one embodiment, the conductive contact structures 1511 and 1512 are located on the back side 1504 of the solar cell 1520 c , wherein the conductive contact structures 1511 and 1512 include locally deposited metal formed on the first doped region 1521 and the second doped region 1522 by LAMP technology.

[0106] Fig. 11CAn exemplary front-contact solar cell manufactured using the methods, means, or apparatus described herein according to some embodiments is shown. The front-contact solar cell 1520c may include a first doped region 1521 disposed on the back side 1504 of the solar cell 1520c. In a certain example, a second doped region 1522 may be disposed on the front side 1502 of the solar cell 1520c. Although one example of the second doped region 1522 is shown, one or more of the second doped regions 1522 may be used. Conductive contact structures 1511, 1512 may be located on the front side and back side 1504 of the solar cell 1520c, wherein the conductive contact structures 1511, 1512 include locally deposited metal formed on the first doped region 1521 and the second doped region 1522 by LAMP technology. The second doped region 1522 may be offset from the first doped region 1521, as shown. The second doped region 1522 may be aligned with the first doped region 1521, for example, vertically aligned.

[0107] Fig.11D An exemplary front-contact solar cell manufactured using the methods, means, or apparatus described herein according to some embodiments is shown. The front-contact solar cell 1520d may include a first doped region 1521 disposed on the back side 1504 of the solar cell 1520d. The conductive contact structures 1511, 1512 may be formed on the front side 1502 and the back side 1504 of the solar cell 1520d, respectively, by LAMP technology, wherein the conductive contact structures 1511, 1512 include locally deposited metals located on the first doped region 1521 and the second doped region 1522. The first doped region 1521 and the second doped region 1522 may include amorphous silicon regions. The solar cell 1520d may include an intermediate layer (e.g., an anti-reflective coating layer ARC) 1526 on the front side 1502 of the solar cell 1520d. The solar cell 1520d may include a back intermediate layer (e.g., a back anti-reflective coating BARC) 1526 located on the back side 1504 of the solar cell 1520d. A thin oxide layer 1530 may be disposed between the first doping region 1521 and the substrate 1525 .

[0108] Fig.11EAnother exemplary front contact solar cell manufactured using the methods, means or apparatus described herein according to some embodiments is shown. Solar cell 1520e may include first doped regions 1521a, 1521b disposed on the back side 1504 of solar cell 1520e. In a certain example, second doped regions 1522a, 1522b may be disposed on the front side 1502 of solar cell 1520d. In a certain embodiment, conductive contact structures 1511, 1512 may be formed on the front side and back side 1504 of solar cell 1520b, respectively, by LAMP technology, wherein conductive contact structures 1511, 1512 include locally deposited metals located on first doped regions 1521a, 1521b and second doped regions 1522a, 1522b. The first doped regions 1521a, 1521b may include doped polysilicon regions. Solar cell 1520e may include an intermediate layer (e.g., an anti-reflective coating ARC) 1526 located on the front side 1502 of solar cell 1520e. The solar cell 1520e may include a back side intermediate layer (eg, a back side anti-reflective coating (BARC)) 1526 on the back side 1504 of the solar cell 1520e.

[0109] Although certain materials are specifically described with reference to the above embodiments, in such embodiments, other materials may be easily substituted for some of the materials, and these embodiments remain within the spirit and scope of the embodiments of the present disclosure. For example, in a certain embodiment, a substrate of a different material, such as a substrate of a certain family of materials, may be used in place of a silicon substrate. In another embodiment, any type of substrate used in the manufacture of microelectronic devices may be used in place of a silicon substrate, for example, a printed circuit board (PCB) and / or other substrate may be used. In addition, although primarily reference is made to back-contact solar cell arrangements, it should be understood that the methods described herein may also be applied to front-contact solar cells. In other embodiments, the above methods may be applicable to manufacture other than solar cells. For example, the manufacture of light emitting diodes (LEDs) may benefit from the methods described herein.

[0110] In addition, although solar cells are described in great detail herein, the methods and / or processes described herein can be applied to various substrates and / or devices, such as semiconductor substrates. For example, semiconductor substrates can include solar cells, light emitting diodes, micro-electromechanical systems, and other substrates.

[0111] Furthermore, although many of the embodiments described involve making direct contact between a semiconductor and a metal foil as a metal source. The concepts described herein may also be applicable to solar applications (e.g., HIT cells) where contact is made to a conductive oxide such as indium tin oxide (ITO) rather than directly contacting the semiconductor. Additionally, embodiments may be applicable to other patterned metal applications, PCB trace formation.

[0112] Therefore, local metallization of semiconductor substrates using a laser beam and the resulting structures are proposed.

[0113] Although specific embodiments have been described above, even if only a single embodiment is described with respect to a particular feature, these embodiments are not intended to limit the scope of the present disclosure. Unless otherwise specified, the examples of features provided in the present disclosure are intended to be illustrative rather than limiting. The above description is intended to cover those alternatives, modifications, and equivalents that will be apparent to those skilled in the art that have the beneficial effects of the present disclosure.

[0114] The scope of the present disclosure includes any feature or combination of features disclosed herein (expressly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Accordingly, new claims may be made during the examination of the present application (or an application claiming priority thereto) for any such combination of features. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims, and features from related independent claims may be combined in any appropriate manner, and not just in the specific forms enumerated in the appended claims.

Claims

1. A method for manufacturing a solar cell, the method comprising: providing an intermediate layer for the substrate, the intermediate layer comprising an opening leading to an exposed portion of the substrate, and wherein the intermediate layer is an insulator; positioning a metal foil over the opening in the intermediate layer; as well as The metal foil is exposed to a laser beam to form a plurality of conductive contact structures, each conductive contact structure having a locally deposited metal portion electrically connected to the exposed portion of the substrate, wherein the locally deposited metal portion is connected to an adjacent portion of the metal foil not exposed to the laser beam through a weakened structure of the metal foil, the weakened structure of the metal foil comprising a pattern. 2 . The method of claim 1 , wherein positioning the metal foil over the substrate comprises positioning a continuous sheet of the metal foil over the substrate. 3 . The method of claim 1 , wherein the substrate comprises a plurality of N-type and P-type semiconductor regions, and wherein the opening in the intermediate layer exposes portions of the plurality of N-type and P-type semiconductor regions.

4. The method according to claim 1, further comprising: A plurality of semiconductor regions are formed in or over the substrate.

5. The method according to claim 1, further comprising: After said exposing the metal foil to the laser beam, at least a portion of the metal foil is removed. 6 . The method of claim 5 , wherein removing at least a portion of the metal foil not exposed to the laser beam comprises forming an edge feature at an edge of the conductive contact structure.

7. The method of claim 1, wherein said exposing said metal foil to said laser beam forms a spatter feature. The method of claim 7 , further comprising removing the spatter features.

9. A solar cell comprising: substrate; a plurality of semiconductor regions, the plurality of semiconductor regions being disposed in or on the substrate; a plurality of conductive contact structures electrically connected to the plurality of semiconductor regions, each conductive contact structure comprising a locally deposited metal structure disposed in direct contact with at least one of the plurality of semiconductor regions, wherein the locally deposited metal structure is connected to a portion of the metal foil through a weakening structure of the metal foil, the weakening structure of the metal foil comprising a pattern; and An intermediate layer is disposed on the substrate, wherein the intermediate layer comprises an opening, the opening exposing portions of the substrate corresponding to the plurality of conductive contact structures, and wherein the intermediate layer is an insulator. 10 . The solar cell of claim 9 , wherein the plurality of semiconductor regions are a plurality of N-type and P-type polysilicon regions disposed in or on the substrate.

11. The solar cell according to claim 9, further comprising: A metal foil portion is disposed over at least a portion of the intermediate layer.

12. The solar cell of claim 11, wherein the metal foil portion is in contact with one of the locally deposited metal structures.

13. The solar cell of claim 12, wherein the electrically conductive contact structure comprises an edge feature.

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