System and method for vacuum deposition

Abstract

The invention relates to a layer deposition system, in particular for depositing at least one localised layer in a plasma-supported deposition system via a mask which partially shades a substrate, which in particular is a solar wafer, on a substrate carrier. The invention also relates to a method and a system for depositing a localised layer pattern on a wafer-like substrate in a vacuum deposition process. The invention contains a layer deposition system which is intended in particular for depositing at least one localised layer in a plasma-supported deposition system, wherein the layer deposition system contains a movable substrate carrier for receiving at least one solar wafer substrate, which is intended for transporting at least one substrate and at least one mask, which masks the substrate, between a charging station and a deposition station, wherein the movable substrate carrier and / or the mask has a magnetic field, wherein the substrate can be arranged on the substrate carrier, and the mask can be arranged on the substrate, precisely with respect to one another, and wherein the mask adheres magnetically as a result of the magnetic field.

Description

[0001] System and method for vacuum deposition

[0002] The invention relates to a layer deposition system, in particular for depositing at least one localized layer in a plasma-assisted deposition system via a mask that partially shades a substrate, which is in particular a solar wafer, on a substrate carrier. Furthermore, the invention relates to a method for depositing a localized layer in a plasma-assisted deposition system, wherein the deposition system comprises a substrate carrier designed to support at least one substrate, in particular a solar wafer, and at least one magnetic mask covering at least one substrate in at least one deposition station. The method comprises at least one deposition step, wherein in the deposition step, at least one film is deposited on localized regions of the substrate in which the mask has openings.

[0003] Vacuum processes are widely used for the deposition of thin films, e.g., for the deposition of silicon layers in amorphous, nano-, micro-, or polycrystalline states. These layers are typically deposited using silicon-containing gases, e.g., SiH4. Hydrogen can be added to the process gas to improve defect passivation.

[0004] Vacuum deposition processes are typically carried out in reactor chambers at low pressures ranging from approximately one to several thousand Pa. Deposition can be achieved by evaporation, sputtering, or the decomposition of gases. The latter process can be achieved by radio wave plasma excitation, also called PECVD (Plasma Enhanced Vapor Deposition), or thermal decomposition on hot surfaces. These processes can be carried out at elevated temperatures of 100 to 300 °C.

[0005] Certain technologies, such as the interdigital back contacts of silicon heterojunction solar cells, require the deposition of localized layer patterns on a substrate. It is known to use a shadow mask for the deposition of localized silicon structures on a silicon wafer used as a substrate. For example, patent application EP3886185 describes how mechanical masking can be used to deposit localized silicon structures on a silicon wafer substrate.

[0006] DE 10 2018 123 523 A1 describes, in principle, the idea that mask frames could support interchangeable mask elements in a coating system. However, the patent application does not make these ideas feasible because important questions, such as how the masks could be used sufficiently reliably or how sufficient mechanical stability of the mask elements could be achieved, remain unanswered in the document.

[0007] The object of the invention is to provide a solution for a masked film deposition process and a suitable machine for industrial solar cell production that solves the problems described above.

[0008] It has been found that in order to obtain clean structures with defined edges in vacuum processes that do not show smearing, it is important that the shadow mask is tightly adhered to the substrate surface.

[0009] At the same time, it is also important that there is as little movement as possible between the mask and the substrate, even when the substrate and the mask are transported from a loading station to a deposition chamber.

[0010] The object is achieved by a layer deposition system which is particularly intended for depositing at least one localized layer in a plasma-assisted deposition system, wherein the layer deposition system contains a movable substrate carrier for receiving at least one solar wafer substrate, which is intended for transporting at least one substrate and at least one mask masking the substrate between a loading station and a deposition station, wherein the movable substrate carrier and / or the mask has a magnetic field, wherein the substrate and the mask thereon can be arranged on the substrate carrier in alignment with one another, and wherein the mask is magnetically adhered by the magnetic field.

[0011] As an alternative to a magnetic substrate carrier or in addition, the mask itself can have permanent magnetic properties and a magnetic field, particularly in areas of application where temperatures occur below the temperature resistance of the magnets.

[0012] It has been shown that a magnetic mask material, particularly a ferromagnetic material, provides an advantageous solution for these purposes. Using a substrate carrier with a magnetic field, the magnetic shadow mask can be fixed to the substrate and the substrate carrier. This prevents relative movement between the substrate carrier, the substrate, and the mask during transport and deposition, and the mask adheres tightly to the substrate. The substrate and the mask are placed at defined, designated positions; in particular, the mask is precisely aligned to the substrate. This alignment or positioning makes it possible to produce electronic structures such as the contact structures of IBC solar cells (the abbreviation IBC stands for "Interdigitated Back Contact").The positioning requirement involves maintaining positional tolerances below the specified tolerances. Maximum permissible tolerances are in the range of 1 mm, but often significantly lower, for example, 0.5 mm or 0.2 mm. If multiple deposition processes are performed consecutively using masks, the permissible tolerances between the position of the previous mask and the position of the currently used mask may be smaller than the permissible tolerances for the position of the first mask relative to the position of the substrate. To achieve sufficiently precise positioning within the permissible tolerances, both functional regions manufactured using a mask, in particular base or emitter regions of the solar cell, and special position markers that serve solely for mask positioning can be used.

[0013] Another advantage of the proposed solution is that the mask adheres evenly to the substrate. Magnetic adhesion is well suited for this, as it allows the preferably thin mask to be pressed onto the substrate with a well-distributed force that exceeds the force of gravity alone. The inventive solution, with thin and lightweight masks, does not require mechanical aids such as clamps or frames. The solution is therefore simple and cost-effective. This is especially true when considering the machinery required for automated handling.

[0014] Layer deposition systems for coating solar wafers, which are used in the production of solar cells, are highly automated machines in the solar industry. Such machines are required to achieve high throughputs, typically several thousand substrates per hour. At the same time, the produced solar cells must be highly efficient, meaning the surface area of ​​the solar wafer must be utilized as fully as possible. High production yields are also required; waste resulting from mask use, e.g., due to mask slippage, must be virtually eliminated. Specialists who build and automate such layer deposition systems can use their expertise to ensure that substrates are loaded onto the substrate carriers with precise positioning and that the masks are loaded and fixed in place with precise positioning on the substrates.Currently common substrates include square or pseudo-square solar wafers with edge lengths in the range of 182 mm or 210 mm, or split solar wafers, e.g., with dimensions of 182 mm x 91 mm. The thickness of Si solar wafers is often between 100 pm and 200 pm at the time of application. In addition to solar wafers, such coating systems can also be used to coat other substrates similar to solar wafers, e.g., glass wafers or thin-film solar cells on glass substrates. Another important requirement for machines used to manufacture solar cells is very low costs per coated substrate; this requirement prohibits the adoption of expensive machine solutions from other technology areas where different price requirements apply.

[0015] Contrary to expert fears that magnetic fields of the substrate carrier could interfere with magnetic fields and / or ions that define a plasma deposition process, surprisingly, such negative effects were not observed.

[0016] The magnetically adhered mask prevents relative movement between the substrate carrier, substrate, and mask, thus minimizing or preventing mechanical damage to the substrate. This is particularly important for already passivated silicon wafers, such as crystalline silicon wafers passivated by an intrinsic amorphous silicon layer, as used in silicon heterojunction solar cells.

[0017] The close fit of the mask to the substrate enables precise pattern deposition with less smearing of the pattern boundaries.

[0018] There are various ways to realize the magnetic field of the substrate carrier.

[0019] Electrical coils can be integrated into the substrate carrier, which are activated by applying a current. This means that a power source must be connected to the substrate carrier during transport and processing. Electrical coils can be used to switch a magnetic field on and off as needed.

[0020] One possible solution is to integrate permanent magnets into the substrate carrier in a specific pattern to fix the magnetic mask to the substrate and substrate carrier. These permanent magnets can be implemented as flat magnets in round or rectangular form, or in any other shape. The thickness of the magnets can range from 0.1 to 2 mm. The lateral dimensions of the magnets can range from 5 mm to 200 mm. The material of the permanent magnet should be selected to withstand process temperatures of 100 to 300 °C. Magnets based on samarium-cobalt alloys, for example, can be used for this purpose. Another solution is to integrate one or more ferromagnetic plates into the substrate carrier. These plates are made of a magnetizable material and magnetized to a specific magnetic field strength.The material used for this purpose should have high magnetic remanence to maintain the magnetic field across multiple processes. For example, a FeAlNiCo alloy of iron with aluminum, nickel, and cobalt is a material with high remanence. However, other ferromagnetic steels with high remanence and coercivity can also be used. Carbon steels and chromium steels, for example, exhibit sufficiently large hysteresis curves in their magnetic behavior and will be used for this purpose in exemplary embodiments.

[0021] Another solution involves generating a magnetic field on the substrate carrier by using a magnetizable material for the substrate carrier itself. The substrate carrier is magnetized before use, at least in the areas where a magnetic mask is placed on the substrate carrier over a substrate. For this purpose, a substrate carrier made of a material with high remanence (as described above for the integrated plate) can be used.

[0022] The orientation of the magnetic field can be unidirectional, meaning that a north or south pole of the magnet or a multiple of the magnets points in one direction, for example up or down.

[0023] The magnetic field with one or the other polarity can be advantageously directed towards the mask.

[0024] The magnetic field can also be realized in the form of a one- or two-dimensional pattern. The pattern can be realized by a local variation in the magnetic field strength or by changing polarity.

[0025] A magnetic pattern can be realized by local field strength fluctuations caused either by the positioning of individual magnets in a specific spacing pattern or by local magnetizations of a magnetizable substrate carrier or a magnetizable plate attached to the substrate carrier.

[0026] The pattern can be a magnetic field with locally different polarities. Individual magnets could be mounted on a substrate carrier in rows with different polarities, with, for example, the north pole of the magnets in a first row pointing in a first direction and the north pole of the magnets in a second row pointing in a second direction opposite to the first direction.

[0027] In some variants, adjacent magnets or magnetized zones in a magnetizable plate each have opposite polarity.

[0028] The strength of the magnetic field, measured on the surface of the substrate carrier facing the side where the substrate and mask are applied, can range between 5 and 100 mT (milli-Tesla). The magnetic field strength can be advantageously adjusted to the thickness of the substrate and / or the mask. This allows the force with which the mask is pulled against the substrate to be adjusted so that, on the one hand, the mask adheres evenly to the substrate and, on the other hand, the mask can be removed without mechanically overloading it.

[0029] The substrate carrier may be provided with reference and alignment marks or pins that enable repeatable alignment of the substrate and the mask.

[0030] The magnetic shadow mask, sometimes also referred to as mask in the following description, which is fixed, for example, by the magnetic forces of the magnetic substrate carrier, can consist of any magnetic, in particular ferromagnetic, material.

[0031] In various embodiments, the shadow mask is designed as a mask for a single substrate or as a mask for multiple substrates.

[0032] To facilitate handling in automated systems, a mask is preferably used that has no magnetic field itself or only a low magnetic field of less than 5 mT. Therefore, a ferromagnetic material with low remanence or coercive field strength, also known as a soft magnetic material, is preferred for the mask.

[0033] A mask made of "INVAR," an alloy of approximately 64-68% iron and approximately 32-36% nickel, has been found to be a preferred material solution. Invar has low remanence and a thermal expansion coefficient close to that of silicon (Invar: ~1.6 E-6 Kl;

[0034] Silicon: ~2.6 E-6 Kl). The latter property is also important during heating from room temperature at approximately 20°C to the process temperature of 100 to 300°C. The similar thermal expansion coefficients of the Invar mask and the silicon substrate reduce the risk of mechanical damage to the passivation layers due to relative movements between the mask and the substrate during heating and cooling cycles in exemplary embodiments of HJT solar cell manufacturing steps.

[0035] The mask can also be coated to protect it from corrosion or mechanical damage. This coating can help extend the lifetime of the mask. This is particularly helpful for removing residual deposited material on the mask during the deposition process. The residual material can be removed, for example, in a chemical etching bath or a plasma-assisted vacuum etching process. The coating can be made of any material that can withstand the removal process. For chemical etching, a metallic coating based on nickel (Ni) or chromium (Cr) can be used. Alternatively or additionally, a coating containing filled or purely fluorinated polymers can be applied. In plasma etching processes, for example, fluorine-based coatings, for example, with aluminum or nickel, can protect the ferromagnetic base material of the mask.

[0036] The mask can be the same size as the substrate to be masked. The mask can also have larger dimensions in at least one X, Y direction. The mask can also have a smaller dimension in at least one X, Y direction.

[0037] The mask may also include alignment marks or openings to align the mask with the wafer substrate and / or the substrate carrier.

[0038] The deposition system used for the localized deposition of a layer on a substrate has at least one deposition chamber and a magnetic substrate carrier.

[0039] The deposition system may also include a loading station in which the substrate and mask can be loaded onto and unloaded from the magnetic substrate carrier.

[0040] The magnetic substrate carrier can be used to transport the substrate with a shadow mask placed above it from the loading station to the coating chamber.

[0041] In these cases, the loading station is designed to allow the loading and unloading of the mask and substrate. Typically, in industrial film deposition systems for solar cell production lines, the loading station is equipped with an automatic loading device. Loading and unloading can be performed either through individual and sequential processes for the mask and substrate, or alternatively as a single process for the assembly of the substrate mask. The coating chamber client accommodates the substrate carrier with the substrate and the shadow mask during the masked deposition of a film on the substrate. The coating chamber is usually a vacuum chamber equipped with a vacuum pump or vacuum pumping system to create a specific pressure range used during film deposition. The coating chamber also has means for depositing a film.The latter can be achieved using an evaporation source activated by thermal heating or by electron or ion heating. Alternatively, deposition can also be achieved by a sputtering process, such as magnetron sputtering. Other examples include deposition by gas decomposition or chemical vapor deposition (CVD), e.g., catalytic hot-wire deposition or plasma-enhanced vapor deposition (PECVD), in which an electrical discharge generates a plasma to assist the chemical vapor deposition.

[0042] The deposition chamber is also partially equipped with a process gas inlet system to provide the necessary process gases for the deposition of the layer. The deposition chamber may also provide means for generating a plasma of the process gases to activate the process gas species used for the deposition of the layer.

[0043] In addition, the deposition system can be equipped with a load lock chamber so that the magnetic substrate carrier can be transported from the loading station to the deposition chamber without having to break a vacuum in the deposition chamber.

[0044] The coating system can also be equipped with heating means, including within the coating chamber, to generate an elevated temperature between 80 and 250 °C for substrate processing. Heating means can also be installed in other areas of the coating system, e.g., to preheat the substrate carrier at the loading station and / or the loadlock chamber.

[0045] The invention also includes a method for depositing a localized layer in a plasma-assisted deposition system, wherein the deposition system comprises a substrate carrier intended to carry at least one substrate, in particular a solar wafer, and at least one mask covering at least one substrate in a deposition station, wherein, prior to the deposition step, at least one substrate and at least one mask are positioned and magnetically attached to the substrate carrier in a loading step, wherein the substrate carrier thus loaded is then transported to a deposition location, wherein during the transport and in the deposition step, the substrate carrier and / or the mask emits a magnetic field in order to keep the substrate and the mask positioned on the substrate carrier.Industrial coating systems such as PECVD coating systems in the solar industry are equipped with large coating chambers for high machine throughputs, allowing many substrates to be coated in a short time. For cost and speed reasons, the volumes of the deposition chambers are designed to be as small as possible. Therefore, there is hardly any space in such coating chambers for the precise positioning of masks. Outside the coating chamber, for example, in a loading area, there is more space, so that the precise attachment of a mask to a substrate carrier with a substrate is a task that an experienced automation machine builder can expertly solve. Due to the magnetic attachment, the mask remains in place during transport to the deposition site or into the deposition chamber and during the subsequent deposition.The local coatings through the openings in the mask can thus be carried out on the intended substrate surface areas, resulting in high-quality products at the end of the manufacturing process.

[0046] The substrate carrier in the deposition system can be moved between at least two deposition steps in at least two deposition stations. The substrate carrier can transport the substrate with the mask between a loading station and a deposition station. The loading station can be a loading station, an unloading station and / or a transfer station. Transport can take place through intermediate stations through which the substrate carrier is moved to one or more stations and which enable temperature control of the substrate carrier and / or the substrate and / or the mask. Temperature control enables the setting of a specific temperature range. The temperature range can be set, for example, between 100 and 300°C, preferably between 150 and 250°C. This temperature range is also used for the deposition of amorphous and micro- or nanocrystalline silicon layers in the production of heterojunction solar cells.

[0047] The method according to the invention can be implemented in various variants. In one chamber, several coatings can be carried out consecutively using the same mask (for example, the deposition of an intrinsic amorphous silicon passivation layer (i-aSi) followed by the deposition of a nanocrystalline phosphorus-doped surface field layer (n-ncSi) on an n-doped crystalline Si solar wafer). However, the coating can also be divided into at least two coating chambers, which are successively approached by substrate carriers loaded with substrates and masks. Dedicated masks can also be used for specific coating chambers, whereby the substrates are combined with the dedicated parts before a coating step and separated from them again after the coating step. The coating process can comprise corresponding loading and unloading steps.

[0048] For example, the intermediate station is a transfer station in which the substrate carrier, including the substrate and mask, is transported between a vacuum deposition station and a loading station. The transfer station can also be equipped with devices that enable temperature control of the substrate carrier. The transfer station can also consist of several individual stations in which temperature control and / or evacuation or ventilation takes place in several stages. In other examples, the intermediate station is a pretreatment station for surface conditioning before coating, a post-treatment station for post-treatment of a deposited layer, a measuring station, an intermediate storage facility, and / or other facilities.

[0049] In the layer deposition system according to the invention, the mask can have a film-like shape that is used without a frame in the layer deposition system. The attribute "film-like" describes that one dimension of the mask, namely the thickness, is smaller than the other dimensions (length and width). This attribute also indicates that the mask has rather low mechanical rigidity. Despite its film-like shape, this mask also functions without a frame; it does not have to be clamped in a frame because deformation of the mask, e.g. due to layer stresses, is prevented by the magnetic holding forces. The film-like shape results in the practical advantages that the mask can also be used in minimally dimensioned coating chambers and that the small mask volume also results in a low mask weight and correspondingly low mechanical demands on the coating system.

[0050] The method of the invention is used in particular to produce localized layers for the production of a so-called IBC solar cell, IBC = Interdigitated Back Contact. Here, layer portions are deposited through the mask onto a substrate consisting of a silicon wafer. The layer portions consist in particular of amorphous and / or microcrystalline and / or nanocrystalline silicon. In terms of process technology, the production of local structures, such as the base and emitter contact structures of the IBC solar cell, using a shadow mask is a very simple solution because the desired structures are present immediately after coating. Alternative production options such as full-surface coating, coating with photoresist, photolithography, etching via a resist mask and resist ashing are more complex and expensive.

[0051] In a manufacturing process for heterojunction IBC solar cells, several amorphous and / or nanocrystalline and / or microcrystalline layers are deposited onto a crystalline silicon wafer. Various electrical and optical properties of the layers can be adjusted via the crystallinity. The resulting crystallinity of the deposited layers depends not only on the deposition parameters (e.g., pressure, gas composition, plasma feed power, frequency, temperature) but also on partially locally different substrate surfaces. The layers are sometimes also produced as gradient or multilayer layers. For cost reasons, the number of different masks used is often kept to a minimum. If possible, an intrinsic amorphous passivation layer and a nano- or microcrystalline doped surface field layer are deposited one after the other using the same mask.

[0052] The method according to the invention can be used to deposit a pattern of a doped silicon layer on a silicon substrate in at least one corresponding deposition step. Patterns for technical purposes can have repeated structures, such as the black and white squares on a chessboard.

[0053] Such patterns can be used to deposit layers locally on designated connection areas, whereby these layers participate in the formation of locally adjacent base and emitter connection areas of an IBC solar cell. Solar cells are two-terminal components that have a positive terminal and a negative terminal. In conventional two-sided solar cells, the two terminals are located on opposite sides of the solar wafer; for example, the entire front side of the solar wafer is the negative terminal and the base of the solar cell, and largely the entire back side of the solar wafer is the positive emitter terminal. In IBC solar cells, both the negative and positive terminals are located on the back of the solar wafer, with offset patterns of correspondingly coated negative and positive connection areas being connected together to form the negative and positive terminals at the latest in the solar module.The entire solar wafer is typically made of silicon, a semiconductor material in which electron-hole pairs are generated from light quanta in solar radiation. In an n-doped base, the electrons are connected to the negative terminal of the solar cell via the base terminal regions, the Meta II contacts located there, and the connected leads. The positively charged holes are connected to the positive terminal of the solar cell via the emitter terminal regions.

[0054] The method according to the invention can be at least one deposition step within an IBC solar cell manufacturing process, in which at least one amorphous and / or at least one nanocrystalline and / or at least one microcrystalline silicon layer or silicon alloy layer is deposited on a crystalline silicon solar wafer. Such solar cells are also referred to as heterojunction solar cells because the pn junction is realized from electronically different materials, namely, on the one hand, the crystalline wafer and, on the other hand, deposited layers with different crystallinities and correspondingly different electrical properties.The base and emitter connection regions are preferably coated with at least two layers each, namely an intrinsic amorphous layer that serves to passivate the wafer surface and a highly doped layer that collects the majority charge carriers or minority charge carriers from the absorber layer according to their polarity, thus promoting the desired charge carrier separation in the solar cell. Depending on the different coatings, several masks can be used, whereby one mask can also be used for multiple deposition processes, as long as the same deposition pattern is required as the result of the deposition.

[0055] In a preferred embodiment, the method according to the invention can be embedded in a particularly efficient manufacturing process for an IBC heterojunction solar cell, wherein a pattern of a doped layer of the first type is generated on the back of the silicon wafer substrate through a magnetically adherent shadow mask. Before generating the pattern of the doped layer of the first type, a passivation layer is deposited over the entire surface of the back of the silicon wafer substrate, which passivation layer preferably consists of an intrinsic, at least partially amorphous silicon layer. A doped layer of the second type is deposited over the entire surface of this passivation layer and the pattern of the doped layer of the first type. In further steps, electrically conductive contact structures adapted to the pattern are generated. The contacts of a first polarity are located in regions of the layer structures generated by the mask.The contacts of the second polarity are electrically isolated from these and are located outside the areas of the first polarity defined by the masks. This manufacturing process is particularly short and correspondingly cost-effective. Various embodiments of the invention will be explained below with reference to figures and illustrations.

[0056] Illustrations:

[0057] Figure 1 shows a top view of a magnetic field emitting substrate carrier, a wafer substrate and a ferromagnetic mask.

[0058] Figure 2 shows a substrate carrier generating a magnetic field, a wafer substrate and a ferromagnetic mask in a side view.

[0059] Figure 3 shows another substrate carrier that generates a magnetic field and is designed to accommodate more than one substrate and a ferromagnetic mask.

[0060] Figure 4 shows a section through different substrate carriers, each with a different magnetic field, in a side view with integrated individual magnets of different orientation and positioning.

[0061] Figure 5 shows a section through various substrate carriers in side views, each with an integrated magnetized plate indicating the magnetic poles.

[0062] Figure 6 shows a cross-section through various magnetized substrate carriers made of a magnetizable material with indication of the magnetic poles.

[0063] Figures 7, 8, 9 show some of the different possibilities of the 2-dimensional arrangement of the magnetic poles of the substrate carrier.

[0064] Figure 10 shows a PECVD system for depositing a layer through a mask that is magnetically attached to a substrate support.

[0065] Figure 1 shows a substrate carrier 1 that emits a magnetic field and is designed to hold a single wafer-shaped substrate 2 and a single ferromagnetic mask 3 for depositing a layer through the mask 3. The substrate carrier here has alignment aids 6 for aligning the substrate 2 with the mask 3 in the designated area. In the illustrated embodiment, the alignment aids 6 are pin-like structures in the substrate carrier for mechanical alignment. In other embodiments not shown, the alignment aids are optical markings for the visual or optical alignment of the substrate 2 with the mask 3. Figure 2 shows a schematic side view of the stack comprising the magnetic substrate carrier 1 with an alignment aid 6, the wafer-shaped substrate 2, specifically a halved solar wafer here, and the ferromagnetic shadow mask 3.The magnetic poles of the substrate carrier are marked by the letter N (for north pole) and by the letter S (for south pole).

[0066] Figure 3 shows a magnetic substrate carrier 1 for holding more than one substrate, here square solar wafers. The substrates are aligned in their individual positions using alignment aids 6. Masking is performed in one embodiment with individual masks for each substrate or, in other embodiments, with a mask covering more than one substrate. In an advantageous solution, a single mask is used to mask all substrates arranged on the substrate carrier 1.

[0067] Figure 4 schematically shows various embodiments of magnetic substrate carriers 1. Individual magnets 4 are integrated into the carrier base plate 8 at localized positions. The magnets 4 are inserted from the top side 9 of the substrate carrier 1 or from the bottom into openings in the carrier base plate 8. In the embodiments shown, the magnets 4 are arranged at intervals in the first embodiment (counted from the top) or in a dense pack next to one another in the second embodiment. The carrier base plate 8 in the 3rd embodiment consists, seen from above, of an upper part 8a and a lower part 8b in order to integrate the magnets 4 inside the substrate carrier 1. In the 4th embodiment, the magnets 4 are inserted from below into the recesses provided for this purpose in the carrier base plate 8.

[0068] Figure 5 shows various variants of substrate carriers 1, wherein the integration of magnetic plates 5 into the carrier base plate 8 varies in the various variants. The magnetic plate 5 is unipolarly magnetized, wherein in the examples shown the plate has one pole on one side and the opposite pole on the opposite side. A not-shown embodiment of substrate carriers intended to accommodate more than one substrate and more than one mask has a single magnetic plate for attaching the individual masks to the respective substrates. In the lowest embodiment shown, two individual magnetic plates 5 are integrated into a carrier base plate 8.

[0069] Figure 6 shows three embodiments of magnetic carrier base plates 8, each in a side view of the cross-section, in which the magnetizable material of the carrier base plate 8 is magnetized differently, resulting in different carrier base plates 13, 14, 15. In addition to the carrier base plate 8, the substrate carrier 1 can have further elements that are not shown here for the sake of clarity. The uppermost carrier base plate 8 is unipolarly magnetized with a magnetic polarity on one side of this carrier base plate 13. The carrier base plate 14 is magnetized in a way in which the polarities on one side of the carrier plate 14 vary in a spaced-apart pattern. In the embodiments of the two upper carrier base plates 13, 14, the substrate carrier 1 is only locally magnetized, namely here in a region in which a mask is attached to a substrate.The substrate carrier 1 of the lowermost carrier base plate 15 shown is magnetized over its entire circumference. In embodiments not shown, the size of the magnetized areas differs from the illustrated embodiments.

[0070] Figure 7 shows in a plan view the two-dimensional pattern of the magnetic polarity of a substrate carrier 1, wherein all north poles of the magnets or a magnetized plate 5 or a magnetized carrier base plate 13, 15 point to one side, namely the illustrated view side.

[0071] Figure 8 shows a plan view of a magnetic substrate carrier 1 with a two-dimensional pattern of magnetic polarities, wherein the polarities vary in a row-like pattern and rows of north and south poles point to the substrate side.

[0072] Figure 9 shows a plan view of a magnetic substrate carrier 1 with a further polarity pattern, which alternates between the north pole and the south pole facing the substrate side. This pattern is also typically generated when a substrate carrier 1 or a carrier base plate 8 is magnetized with locally distributed magnetizing magnets or induction coils. This preferred pattern has the advantage that the combined forces of all individual magnets are small, thus making handling of the mask correspondingly easy.

[0073] Figure 10 outlines a PECVD coating system 10 for the local application of a layer to a substrate 2 through a shadow mask or the mask 3. In the arrangement shown, the PECVD coating system 10 has a loading station 11 for loading the substrate 2 and the mask 3 onto the magnetic substrate carrier 1 and a PECVD deposition chamber 12 for the deposition of the layer onto the magnetic substrate carrier 1 and in particular onto the substrate arranged thereon and the mask positioned above it. Here, both the loading and unloading of the substrate carrier 1 takes place in the loading station 11; in other exemplary embodiments not shown, the layer deposition system has a loading station and additionally an unloading station. Those skilled in the art will know that a PECVD coating system 10 has many other components, of which an RF generator 16, a vacuum pump 17, and a gas supply 18 are outlined here only as examples.

[0074] Reference symbol

[0075] 1 magnetic substrate carrier

[0076] 2 Substrat

[0077] 3 Mask (ferromagnetic)

[0078] 4 Magnet

[0079] 5 Magnetized plate

[0080] 6 alignment aids

[0081] 8 Support base plate

[0082] 8a Upper part of the support base plate

[0083] 8b Lower part of the support base plate

[0084] 10 PECVD deposition system

[0085] 11 Charging station

[0086] 12 PECVD deposition chamber

[0087] 13, 14, 15 Carrier base plates with different magnetizations

[0088] 16 RF generator

[0089] 17 Vacuum pump

[0090] 18 Gas supply

[0091] 110 Substrate carrier top for holding substrate and mask

Claims

Patent claims 1. A layer deposition system (10), in particular for depositing at least one localized layer in a plasma-assisted deposition system, wherein the layer deposition system contains a movable substrate carrier (1) for receiving at least one solar wafer substrate, which is intended for transporting at least one substrate (2) and at least one mask (3) masking the substrate (2) between a loading station (11) and a deposition station (12), wherein the movable substrate carrier (1) and / or the mask (3) has a magnetic field, wherein the substrate (2) and the mask (3) thereon can be arranged in alignment with one another on the substrate carrier (1), and wherein the mask (3) is magnetically adhered between the mask and the substrate carrier by the magnetic field.

2. Layer deposition system (10) according to claim 1, wherein the magnetic field of the substrate carrier (1) is constructed by individual magnets (4) integrated into the substrate carrier.

3. Layer deposition system (10) according to claim 1, wherein the magnetic field of the substrate carrier (1) is constructed by at least one magnetized plate (5) attached to the substrate carrier (1).

4. Layer deposition system (10) according to claim 1, wherein the magnetic field of the substrate carrier (1) is built up by a magnetization of the substrate carrier (1) which consists of a magnetizable material.

5. Layer deposition system (10) according to one of claims 1 to 4, wherein the magnetic field of the substrate carrier (1) is unipolar.

6. Layer deposition system (10) according to one of claims 1 to 4, wherein the magnetic field of the substrate carrier (1) has an alternating polarity.

7. Layer deposition system (10) according to one of claims 1 to 6, wherein the magnetic field of the substrate carrier (1) is concentrated on the region in which the substrate (2) and / or the mask (3) are arranged.

8. Layer deposition system (10) according to one of claims 1 to 7, wherein the mask (3) is used as a shadow mask for more than one substrate (2).

9. A layer deposition system according to any one of claims 1 to 8, wherein the mask (3) consists of an alloy of 32-36% Ni (nickel) and 64-68% Fe (iron).

10. A film deposition system according to at least one of the preceding claims, wherein the mask (3) has a film-like shape which is used without a frame in the film deposition system.

11. A method for depositing a localized layer in a plasma-assisted deposition system (10), wherein the deposition system (10) comprises a substrate carrier (1) intended to support at least one substrate (2), in particular a solar wafer, and at least one magnetic mask (3) covering at least one substrate (2) in at least one deposition station (12), wherein the method comprises at least one deposition step, wherein in the deposition step at least one film is deposited on localized areas of the substrate (2) in which the mask (3) has openings, characterized in that prior to the deposition step, at least one substrate (2) and at least one mask (3) are positioned and magnetically attached to the substrate carrier (1) in a loading step, wherein the thus loaded substrate carrier (1) is then transported to a deposition location,wherein during the transport and in the deposition step, the substrate carrier (1) and / or the mask (3) emits a magnetic field to keep the substrate (2) and the mask (3) positioned on the substrate carrier (1).

12. The method according to claim 11, wherein the substrate carrier (1) is moved in the deposition system (10) between at least two deposition steps in at least two deposition stations (12).

13. A method according to any one of claims 11 or 12, wherein the method is a deposition process of locally confined layers within a solar cell manufacturing process.

14. The method according to any one of claims 11 to 13, wherein the method comprises depositing layers locally on surfaces provided for this purpose, said layers being involved in the formation of local, adjacent contacts of an IBC solar cell.

15. The method according to claim 14, wherein in at least one deposition step of the method at least one amorphous and / or at least one nanocrystalline and / or at least one microcrystalline silicon layer or silicon alloy layer is deposited on a crystalline silicon solar wafer.

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