Boundary element for a process tank

Abstract

Boundary element (10, 20, 30) for a process tank for receiving a chemical process solution, wherein the boundary element (10, 20, 30) is provided with at least one slot (12, 22, 32) for passing wafers through the boundary element (10, 20, 30), wherein an inner wall (11, 21, 31) of the slot (12, 22, 32) is structured such that the chemical process solution flowing out of the process tank experiences a change in momentum such that an outflowing volume flow is reduced, wherein the structuring of the inner wall (11, 21, 31) of the slot (12, 22, 32) comprises drop-shaped indentations (13, 23).

Description

The present invention relates to a delimiting element for a process basin. The process basin is suitable for receiving a chemical process solution. The restriction member is provided with at least one slot for passing wafers through the restriction member. The inner wall of the slot is structured in such a way that process solution flowing out of the process basin experiences such a change in momentum that the volume flow flowing out is reduced. The limiting element of the invention can reduce the outflow of process solution from the process basin. Because less process solution exits the process basin, process costs can be saved, since either less process solution is needed or less process solution has to be circulated. The invention can be used, inter alia, in the production of solar cells or else of printed circuit boards, for example printed circuit boards for the electrical industry.The production of solar cells from multi-crystalline silicon solar cells is known and contains a wet chemical texture process. For texturing, a solution of hydrofluoric acid (HF) and nitric acid (HNO 3) is used. This reacts with silicon in a strongly exothermic reaction to form hexafluorosilicic acid (H 2 SiF 6) and nitrogen monoxide (NO), which in contact with atmospheric oxygen further reacts to form nitrogen dioxide (NO 2).The texture process is usually carried out in continuous flow systems (inline etching systems). In this case, the wafers are transported horizontally through the installation on transport rollers. Hold-down rollers ensure that the wafers do not lose contact with the transport rollers. Inside the facility are areas where the wafers are exposed to a chemical process solution either by spraying or by dipping. The process solution may be located in a process basin. Since the wafers are horizontally guided through the installation in this method, the wafers require the maximum area, which limits the number of wafers processed simultaneously and thus the throughput of the installations.During the processing of wafers, it is possible in principle to distinguish between an inline method and a batch method. In an inline method, the wafers are transported through the system in series one after the other. It is also possible for a plurality of rows of wafers to be transported simultaneously next to one another (multi-track inline method). In contrast, in the batch method, the wafers are not individually conveyed while resting on a conveyor belt or the like, but by a carrier (carrier) in which a plurality of wafers are stacked.DE 10 2007 035 086 B3 relates to the accumulation of treatment liquids in a working container and the conveying of flat material in a horizontal orientation through the working container of continuous installations for wet-chemical or electrolytic surface treatment on both sides as a dipping treatment.WO 2020 / 157 229 A1 discloses an apparatus and an inline method for processing wafers, in which the wafers are transported through the installation in a vertically oriented manner. This enables an increased throughput compared to horizontally transported wafers. The vertically oriented wafers can be executed in and out of the process basin in particular by slots in delimiting elements of the process basin. An escape of process solution from the slots is to be counteracted in that the slots are as narrow as possible and the delimiting elements in the region of the slots are as thick as possible, since this respectively increases the hydraulic resistance of the slots.Against this background, it is an object of the present invention to provide delimiting elements for process basins through which wafers can likewise be passed, which, however, still further reduce the outflow of process solution from the process basin.The object is achieved by the subject matters of the patent claims. The object is achieved in particular by a delimiting element for a process basin for receiving a chemical process solution, wherein the delimiting element is provided with at least one slot for passing wafers through the delimiting element, characterized in that the inner wall of the slot is structured in such a way that process solution flowing out of the process basin experiences a pulse change such that the volume flow flowing out is reduced, wherein the structuring of the inner wall of the slot comprises drop-shaped indentations. A limiting element of the invention according to exemplary embodiments is shown in FIGS. 1 to 2. In the present disclosure, the terms "boundary element" and "boundary wall" are used interchangeably unless otherwise indicated.The structuring of the inner wall comprises drop-shaped indentations. The volume flow flowing out can be reduced particularly efficiently with the aid of indentations in the inner wall, in particular if the indentations are arranged in such a way that they form an acute angle with the direction of flow out of the process solution. A portion of the outwardly flowing process solution flows into the indentations and from there passes back into the main volume of the slot such that it obstructs the volume flow flowing out, which is thereby reduced. If the indentations are arranged in such a way that they form an acute angle with the outflow direction of the process solution, this effect is particularly pronounced and the reduction in the outflow volume flow is correspondingly particularly great. The geometry of the indentations can also have an influence on the extent of the reduction in the volume flow flowing out. Drop-shaped indentations, for example those as shown by way of example in FIGS. 1 and 2, are particularly efficient.The indentations need not necessarily consist entirely of empty volumes, although this is entirely possible in embodiments of the invention, as shown for example in FIG. 2. The term "empty volume" is to be understood such that recesses are provided in the material of the delimiting element in the region of the empty volume and these recesses are not filled with a filling material, for example the material of the delimiting element or an alternative solid. In embodiments of the invention, it can be provided to fill a part of the empty volume of the indentations with a filling material, for example with the material of the delimiting element or with an alternative solid material. Combinations of the material of the delimiting element with an alternative solid material are also possible for the configuration of the filling material. By targeted filling of a part of the empty volume, the flow within the indentations can be influenced in such a way that the volume flow flowing out is particularly efficiently reduced. Indentations in which a part of the empty volume is filled with a filling material are shown by way of example in FIG. 1.The material of the delimiting element depends on the respective application, in particular on the process temperature and / or the constituents of the chemical etching solutions. Materials which can be printed with the aid of a 3D printer are preferred, since the production of complex structures is thus the simplest. Furthermore, stainless steel or plastics may be mentioned as preferred materials. Among the plastics, PP (polypropylene), ECTFE (ethylene chlorotrifluoroethylene), PE (polyethylene), HD-PE (high-density polyethylene), PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene) and PVC (polyvinyl chloride) are particularly preferred.The outflow direction of the process solution from the process basin can vary depending on the fill level of the process basin with process solution and depending on the position within the slot. However, the main outflow direction is directed horizontally outwards from the process basin. In the present disclosure, when the direction of outflow of the process solution is meant, this means the direction running horizontally out of the process basin along the slot, unless otherwise stated. Any vertical directional components are thus neglected.In the present specification, when the terms "vertical" and "horizontal" are used, it means "substantially vertical" and "substantially horizontal", respectively, unless otherwise specified. The surface of the process solution located in the process basin can preferably serve as a reference point. This surface is aligned horizontally in the absence of wave movements or other movements of the process solution. An area vector perpendicular to the surface of the process solution is thus vertical. The term "substantially horizontal" therefore preferably describes an orientation or movement which is substantially parallel to the surface of the process solution located in the process basin, while the term "substantially vertical" describes an orientation or movement which is substantially orthogonal to the surface of the process solution located in the process basin.Preferably, a surface vector standing perpendicular on a substantially horizontally oriented surface forms an angle of at most 20°, further preferably at most 10°, further preferably at most 5°, further preferably at most 1°, further preferably about 0° with a surface vector standing perpendicular on the surface of the process solution. Preferably, the vector of a substantially horizontal direction of movement forms an angle of at least 70° and at most 110°, further preferably of at least 80° and at most 100°, further preferably of at least 85° and at most 95°, further preferably of about 90°, with a surface vector standing perpendicular to the surface of the process solution.Preferably, a surface vector standing perpendicularly on a substantially vertically oriented surface forms an angle of at least 70° and at most 110°, further preferably of at least 80° and at most 100°, further preferably of at least 85° and at most 95°, further preferably of about 90°, with a surface vector standing perpendicularly on the surface of the process solution. Preferably, the vector of a substantially vertical movement direction forms an angle of at most 20°, more preferably at most 10°, more preferably at most 5°, more preferably at most 1°, more preferably about 0° with a surface vector standing perpendicular to the surface of the process solution.At a given delimiting element, the outflow direction of the process solution can be easily determined, even if the delimiting element has not yet been joined together with further delimiting elements to form a process basin. For this purpose, it is merely necessary to establish in which orientation the delimiting element is arranged during intended use, and based thereon the horizontal outflow direction of the process solution through the slot is determined. For this purpose, experimental investigations are not necessarily required. Rather, the skilled person already recognizes from the geometry of the delimiting element and the slots how the outflow direction of the process solution is.The angle which the indentations form with the outflow direction of the process solution can be determined independently of the geometric configuration of the indentations on the basis of cross sections, wherein cross sections are meant, as shown for example in FIGS. 1-5 and 2-5. In such a cross section, the indentations are shown as secondary volumes branching off from the main volume of the slot and extending into the material of the delimiting element. The terms "main volume" and "subvolume" are not intended to express that the main volume is necessarily greater in magnitude than the magnitude of the subvolumes, although this may well be the case in some embodiments of the invention. Rather, the term "main volume" is intended to indicate that it is the portion of the slot that serves the primary function of the slot, namely the passing of wafers through the restriction element. The term "secondary volume" in contrast denotes the indentations as regions deviating from the main volume of the slot. An imaginary line from the beginning of the indentation to the end of the indentation parallel to the outflow direction of the process solution from the process basin can be referred to as the base line of the indentation. The base line of the indentation thus represents the boundary line between the indentation and the main volume of the slot.In order to determine the angle that the indentation forms with the outflow direction of the process solution, the center point of the base line of the indentation and the centroid of the indentation are first determined. The angle which the indentation forms with the outflow direction of the process solution is the angle which the connecting line, which is directed from the center of the base line of the indentation to the centroid of the indentation, forms with the outflow direction of the process solution. For determining the centroid, preferably only the empty volume of the indentation is taken into account.In preferred embodiments, the indentations are configured such that their horizontal extent, i.e. the extent in the plane of a cross section as shown in FIGS. 1-5 and 2-5, is exactly greater than or equal to their vertical extent, i.e. the extent orthogonal to the cross-sectional plane. In particular, embodiments in which a determination of the angle formed by the indentations with the outflow direction of the process solution is preferably carried out on the basis of cross sections as shown, for example, in FIGS. 1-5 and 2-5.In other embodiments, the indentations may have a relevant vertical extent, in particular a vertical extent which is greater than the horizontal extent of the indentations. In such cases, too, the determination of the angle that the indentations form with the outflow direction of the process solution can be carried out on the basis of cross sections as shown, for example, in FIGS. 1-5 and 2-5. This applies in particular in embodiments in which the vertical extension is configured to be regular, for example in the form of a channel. In particular in the case of large and irregular vertical expansion components, however, a determination of the angle which the indentations form with the outflow direction of the process solution can be disadvantageous on the basis of cross sections, since individual cross sections can often only insufficiently reproduce the actual spatial expansion of the indentations in such cases. It can therefore be useful to determine the angle formed by the indentations with the outflow direction of the process solution using an alternative method.Such an alternative method is based on using the center of gravity of the base surface of the indentation instead of the center point of the base line of the indentation. The base of the indentation is (analogous to the base line of the indentation) an imaginary surface representing the boundary surface between the indentation and the main volume of the slot. Similarly, instead of the centroid that the indentation has in a cross section, the centroid of the indentation is used. The angle that the indentation forms with the outflow direction of the process solution is then determined as the angle that the connecting line, which is directed from the center of gravity of the base surface of the indentation to the center of volume of the indentation, forms with the outflow direction of the process solution. In this case, the vertical portion of the direction vector from the center of gravity of the base area of the indentation to the center of gravity of the volume of the indentation is neglected. The angle is therefore determined which the horizontal portion of the direction vector forms from the center of gravity of the base area of the indentation to the center of gravity of the volume of the indentation with the outflow direction of the process solution. For determining the center of gravity of the volume, preferably only the empty volume of the indentation is taken into account.It is particularly advantageous if the indentations are arranged in such a way that they form an acute angle with the outflow direction of the process solution. The angle can preferably be >0°, further preferably at least 5°, further preferably at least 10°, further preferably at least 15°, further preferably at least 20°, or further preferably at least 25°. The angle can preferably be <90°, further preferably at most 80°, further preferably at most 70°, further preferably at most 60°, further preferably at most 50°, or further preferably at most 40°. The angle can preferably be in a range from >0° to <90°, further preferably from 5° to 80°, further preferably from 10° to 70°, further preferably from 15° to 60°, further preferably from 20° to 50°, or further preferably from 25° to 40°.A particularly advantageous embodiment of the invention can consist in not providing the indentations as purely passive volume elements which counteract the outflowing volume flow solely in that they absorb a part of the outflowing process solution and impede and reduce the outflowing volume flow by the return flow into the main volume of the slot, but rather in actively configuring the indentations in such a way that a countercurrent to the outflowing process solution can be generated by supplying the indentations with a fluid via a feed line. In such a case, it is appropriate to configure the indentations as channels in order to ensure a particularly efficient inflow of the fluid. Both gaseous and liquid fluids or combinations thereof are suitable. The fluid can be gaseous, for example. Nitrogen, compressed air or combinations thereof are particularly preferred. The fluid may be liquid. For example, it is possible to use process solution as fluid. This is particularly advantageous because, when the fluid is mixed with the outflowing process solution, there are no changes in the composition of the process solution, in particular no dilution. Combinations of gaseous and liquid fluids are also possible. Preferably, the fluid is selected from the group consisting of nitrogen, compressed air, process solution and combinations of two or more thereof.The pressure of the gaseous fluid should preferably be less than 6.0 bar, more preferably less than 3.0 bar or less than 1.5 bar, for example at most 1.2 bar. The pressure of the gaseous fluid can be, for example, at least 0.1 bar, at least 0.2 bar or at least 0.5 bar, in particular at least 0.8 bar. Preferably, the pressure of the gaseous fluid is in a range from 0.1 to <3.0 bar, from 0.2 to <2.0 bar, or from 0.5 to <1.5 bar, for example from 0.8 to 1.2 bar or from about 1.0 bar. By this is meant the relative pressure of the gaseous fluid with respect to atmospheric air pressure.The pressure of the liquid fluid should preferably be at most 1.0 bar, more preferably at most 0.7 bar or at most 0.5 bar, for example at most 0.4 bar. The pressure of the liquid fluid can be, for example, at least 0.02 bar, at least 0.05 bar or at least 0.1 bar, in particular at least 0.2 bar. Preferably, the pressure of the liquid fluid is in a range from 0.02 to 1.0 bar, from 0.05 to 0.7 bar, or from 0.1 to 0.5 bar, for example from 0.2 to 0.4 bar or from about 0.3 bar. By this is meant the relative pressure of the liquid fluid with respect to atmospheric air pressure.According to the invention, it is also possible to design the slots as narrow as possible and / or to design the delimiting element (in particular in the region of the slots) as thick as possible in order to further increase the hydraulic resistance of the slots. It is possible in particular to provide a greater thickness of the delimiting element for the region of the slots than for the remaining regions of the delimiting element, as shown for example in FIGS. 1 to 4. Such a configuration is even particularly advantageous since a large slot depth can thereby be achieved without the entire delimiting element having to have a large thickness. In particular, the thickness of the frame region of the delimiting element can be less than the thickness (depth) of the slots.It is also possible to configure the delimiting element asymmetrically in such a way that the depth in the region of the slot beyond the depth of the frame region is less in the direction of the interior of the process basin than in the direction of the outer side of the process basin. In particular, this makes it possible to prevent the volume of the process basin from being reduced unduly at the expense of increasing the depth of the slots.Preferably, the thickness of the delimiting element (in particular in the region of the slots) is at least 10% of the wafer length, further preferably at least 13.5%, further preferably at least 15% of the wafer length, further preferably at least 20% of the wafer length, further preferably at least 27% of the wafer length. Preferably, the thickness of the delimiting element (in particular in the region of the slots) is at most 50% of the wafer length, further preferably at most 45% of the wafer length, further preferably at most 40% of the wafer length, further preferably at most 35% of the wafer length, further preferably at most 30% of the wafer length. The thickness of the delimiting element (in particular in the region of the slots) is preferably in a range from 10% to 50% of the wafer length, for example from 13.5% to 45% of the wafer length, from 15% to 40% of the wafer length, from 20% to 35% of the wafer length, or from 27% to 30% of the wafer length. Wafer lengths of 156 mm to 210 mm are currently to be found in the photovoltaic industry.Preferably, the thickness of the delimiting element (in particular in the region of the slots) is in a range from 15 mm to 80 mm, more preferably from 20 mm to 60 mm, more preferably from 30 mm to 50 mm. The thickness of the delimiting element (in particular in the region of the slots) is preferably at least 15 mm, for example at least 20 mm or at least 30 mm. The thickness of the delimiting element (in particular in the region of the slots) is preferably at most 80 mm, for example at most 60 mm or at most 50 mm.The width of the at least one slot is preferably at most 5 times, more preferably at most 3 times the wafer thickness, but preferably at least 1.1 times, more preferably at least 1.5 times the wafer thickness. The width of the slit is preferably in a range from 220 μm to 1000 μm, more preferably from 300 μm to 600 μm.The slots are preferably chamfered on the inlet side, that is to say the edge between the front and a slot is preferably provided with a chamfer. This enables the wafers to be inserted even particularly reliably in the case of tolerances in the transport system.Preferably, the width of the slots narrows in the direction of passage. This contributes to an even better guidance of the wafers through the slots. In such embodiments, the aforementioned width of the slits denotes the width of the slits at the narrowest point. In the case of a tapering slot width, the ratio of the slot width at the widest point to the slot width at the narrowest point is preferably in a range from 1.1:1 to 2:1, more preferably from 1.2:1 to 1.5:1. However, in view of the usually large ratio of the thickness of the delimiting element (in particular in the region of the slots) to the width of the slots, the side walls of a slot generally run at least approximately parallel to the outflow direction of the process solution even with a tapering slot width.For single-track inline methods, it is sufficient that the delimiting element is provided with exactly one (in particular vertically running) slot for passing through the (in particular vertically aligned) wafers. In multi-track inline processes, a plurality of rows of wafers are simultaneously transported side by side. For such cases, the delimiting element can be provided with more than one (in particular vertically running) slot for passing through the (in particular vertically aligned) wafers. In particular, the number of slits should correspond to the number of parallel-processed rows of wafers. In preferred embodiments, the delimiting element is provided with 2 to 1000, more preferably 5 to 500, more preferably 10 to 200, more preferably 20 to 100, more preferably 30 to 50 (in particular vertically extending) slots for passing through the (in particular vertically oriented) wafers.The distance between the slits is determined by the distance between the parallel processed rows of wafers. The distance between the slots is preferably 2 times to 100 times, more preferably 5 times to 50 times, more preferably 10 times to 30 times, more preferably 20 times to 25 times the width of the slots. The distance between the slots can be, for example, at least 2 times, at least 5 times, at least 10 times, or at least 20 times the width of the slots. The distance between the slots can be, for example, at most 100 times, at most 50 times, at most 30 times, or at most 25 times the width of the slots. The distance between the slits is preferably 0.4 mm to 40 mm, more preferably from 1 mm to 10 mm, more preferably from 2 mm to 6 mm, more preferably from 4 mm to 5 mm, more preferably from 4.5 mm to 4.9 mm, more preferably from 4.7 mm to 4.8 mm. The distance between the slots can be, for example, at least 0.4 mm, at least 1 mm, at least 2 mm, at least 4 mm, at least 4.5 mm, or at least 4.7 mm. The distance of the slots from one another can be, for example, at most 40 mm, at most 10 mm, at most 6 mm, at most 5 mm, at most 4.9 mm, or at most 4.8 mm.The slots can be introduced into the delimiting element in various ways. The delimiting element is preferably already produced with slots, in particular by means of additive manufacturing, for example 3D printing. This allows maximum freedom in the geometric configuration of the structuring of the inner wall of the slot, in particular with regard to the shape of the indentations preferably provided.The dimensions of the slots preferably correspond substantially to the dimensions of the wafers in the front view of the vertical alignment. This enables the vertically oriented wafers to be passed through the slots in the horizontal direction of movement without the slots having unnecessarily large dimensions which could be associated with an increased and undesired emergence of process solution from the process basin. What is meant are the geometric dimensions of the main volume of the slots. The structuring of the inner wall with indentations or other configurations enables a further reduction of the volume flow flowing out, as described in detail above.The slots preferably have a height in a range from 10 mm to 1000 mm, more preferably from 20 mm to 500 mm, more preferably from 50 mm to 300 mm, more preferably from 100 mm to 200 mm, more preferably from 150 mm to 170 mm, more preferably from 156 mm to 168 mm, more preferably from 160 mm to 165 mm. The height of the slots can be, for example, at least 10 mm, at least 20 mm, at least 50 mm, at least 100 mm, at least 150 mm, at least 156 mm, or at least 160 mm. The height of the slots can be, for example, at most 1000 mm, at most 500 mm, at most 300 mm, at most 200 mm, at most 170 mm, at most 168 mm, or at most 165 mm.In some embodiments, the slots preferably have a height in a range from 10 mm to 1000 mm, further preferably from 50 mm to 500 mm, further preferably from 100 mm to mm, further preferably from 150 mm to 250 mm, further preferably from 200 mm to 225 mm, further preferably from 210 mm to 222 mm, further preferably from 214 mm to 219 mm. The height of the slots can be, for example, at least 10 mm, at least 50 mm, at least 100 mm, at least 150 mm, at least 200 mm, at least 210 mm, or at least 214 mm. The height of the slots can be, for example, at most 1000 mm, at most 500 mm, at most 300 mm, at most 250 mm, at most 225 mm, at most 222 mm, or at most 219 mm.The width of the slit is preferably at most 5 times, more preferably at most 3 times the wafer thickness, but preferably at least 1.1 times, more preferably at least 1.5 times the wafer thickness. The width of the slit may be, for example, in a range of 1.1 to 5 times or 1.5 to 3 times the wafer thickness. The width of the slit is preferably in a range from 220 μm to 1000 μm, more preferably from 300 μm to 600 μm. The width of the slot may be, for example, at least 220 μm or at least 300 μm. The width of the slot may be, for example, at most 1000 μm or at most 600 μm. This means in each case the width of the main volume of the slots. Any indentations are not taken into account when specifying the width of the slot.The depth of the slots is determined in some embodiments substantially by the depth (thickness) of the delimiting element. In some embodiments, a greater thickness of the restriction member is provided for the region of the slots than for the frame region of the restriction member surrounding the region of the slot, as shown, for example, in Figures 1-4. Preferably, the depth of the slits is at least 10% of the wafer length, more preferably at least 13.5% of the wafer length, more preferably at least 15% of the wafer length, more preferably at least 20% of the wafer length, more preferably at least 27% of the wafer length. Preferably, the depth of the slots is at most 50% of the wafer length, further preferably at most 45% of the wafer length, further preferably at most 40% of the wafer length, further preferably at most 35% of the wafer length, further preferably at most 30% of the wafer length. The depth of the slits may be, for example, in a range of 10% to 50% of the wafer length, 13.5% to 45% of the wafer length, 15% to 40% of the wafer length, 20% to 35% of the wafer length, or 27% to 30% of the wafer length. Preferably, the depth of the slots is in a range from 15 mm to 80 mm, more preferably from 20 mm to 60 mm, more preferably from 30 mm to 50 mm. The depth of the slots can be, for example, at least 15 mm, at least 20 mm, or at least 30 mm. The depth of the slots can be, for example, at most 80 mm, at most 60 mm, or at most 50 mm.The present invention also relates to a process basin for receiving a chemical process solution, which comprises one or more delimiting elements of the invention. It is advantageous if the at least one slot for passing wafers through the delimiting element is oriented vertically. This enables vertically oriented wafers to be able to be carried into and / or out of the process basin in the horizontal direction of movement.Limiting the process basin on all sides by means of conventional limiting elements does not represent a satisfactory solution for an apparatus which is to be suitable for carrying out an inline method. This would prevent the vertically oriented wafers from being able to be carried into and out of the process basin in the horizontal direction of movement. Rather, the wafers would have to be lifted vertically, guided over the delimiting element and subsequently lowered vertically into the process basin, which is not compatible with an inline method.The process basin of the present invention is therefore bounded on at least one side by a bounding element of the present invention provided with at least one slot for passing wafers through the bounding element. The inner wall of the slot is structured in such a way that process solution flowing out of the process basin experiences such a pulse change that the volume flow flowing out is reduced, wherein the structuring of the inner wall of the slot comprises drop-shaped indentations.It is advantageous, for example, if the process basin contains two delimiting elements according to the present invention. These two delimiting elements can be arranged in particular on opposite sides of the process basin. This allows the wafers to be introduced into the process basin on one side and to be discharged from the process basin on the opposite side of the process basin. The remaining delimiting elements of the process basin (in the case of rectangular process basins, also two in number) can be configured in a conventional manner. In particular, no slits need to be provided, since no wafers generally need to be guided through these side walls of the process basin oriented parallel to the transport of the wafers through the process basin. Apart from the slits that are necessarily present and their configuration described herein, the delimiting element of the present invention can be configured analogously to the remaining delimiting walls of the process basin with respect to the other configuration.According to preferred embodiments of the invention, process basins with a rectangular base are used. The width of the process basin depends primarily on the number of wafers to be processed in parallel and on their thickness and distance from one another. The width of the process basin is preferably in a range from 100 mm to 1000 mm, more preferably from 200 mm to 800 mm, more preferably from 500 mm to 700 mm. The length of the process basin depends primarily on the desired process time that the wafers are to be moved in the process basin, wherein the transport speed of the wafers through the process basin is to be taken into account. The length of the process basin is preferably in a range from 100 mm to 5000 mm, more preferably from 300 mm to 4000 mm, more preferably from 800 mm to 3000 mm. The height of the process basin is determined substantially according to the dimensions of the wafers to be processed, i.e. due to the vertical alignment according to their length or width. The process basin preferably has a height which allows the process solution to accumulate to a height which exceeds the height of the wafers, so that the wafers in the process basin are completely immersed in the process solution. The height of the process basin is preferably in a range from 20 mm to 2000 mm, more preferably from 50 mm to 1000 mm, more preferably from 100 mm to 500 mm, more preferably from 150 mm to 300 mm, more preferably from 160 mm to 250 mm, more preferably from 180 mm to 220 mm.The present invention also relates to an apparatus for processing wafers with a chemical process solution, the apparatus comprising a process basin of the present invention. The device preferably further comprises transport means and hold-down means and is preferably designed such that wafers oriented vertically between the transport means and the hold-down means can be introduced into the process basin and discharged from the process basin in the horizontal direction of movement. The configuration of the limiting element of the invention preferably allows continuous operation of the device.The apparatus of the present invention is an apparatus for processing wafers with a chemical processing solution. Preferably, silicon wafers, in particular multicrystalline or monocrystalline silicon wafers, are to be subjected to a texture process with the aid of the device according to the invention. The processing of the wafers is therefore preferably texturing. Such texturing of wafers is known and is used above all in the production of solar cells. The process solution used for multicrystalline wafers preferably comprises hydrofluoric acid (HF) and nitric acid (HNO 3), that for monocrystalline wafers comprises a mixture of aqueous potassium hydroxide solution (KOH) and one or more organic additives.The apparatus of the present invention comprises a process basin for receiving the chemical process solution. The apparatus can also comprise a plurality of process basins, for example for parallel processing of a plurality of wafers or for sequential processing of a wafer with different process solutions. It is also possible for a plurality of wafers to be processed simultaneously and / or successively in the same process basin.The apparatus of the present invention preferably comprises transport means and hold-down means. The transport means serve for transporting the wafers through the apparatus. The hold-down means ensure that the wafers do not lose contact with the transport means. Transport means and hold-down means are in particular arranged in such a way that the wafers can be aligned vertically between the transport means and the hold-down means and can be guided through the apparatus in the horizontal direction of movement, in particular into the process basin, through the process basin and out of the process basin.The distance between the transport means and the hold-down means preferably corresponds substantially to the length or the width of the wafers and not to the thickness of the wafers. The distance between the transport means and the hold-down means is determined by the vertical orientation of the wafers between the transport means and the hold-down means. In certain embodiments, the transport means and / or the hold-down means are arranged to be movable in the vertical direction, so that the distance between them can be adapted flexibly to the length or width of the processed wafers. As a rule, the length of the wafers corresponds to the width of the wafers. The wafers thus generally have a square base area.Preferably, the clear distance between the transport means and the hold-down means lies in a range from 10 mm to 1000 mm, more preferably from 20 mm to 500 mm, more preferably from 50 mm to 300 mm, more preferably from 100 mm to 200 mm, more preferably from 150 mm to 170 mm, more preferably about 156 mm. The clear distance between the transport means and the hold-down means is preferably at least 10 mm, more preferably at least 20 mm, more preferably at least 50 mm, more preferably at least 100 mm, more preferably at least 150 mm, more preferably about 156 mm. The clear distance between the transport means and the hold-down means is preferably at most 1000 mm, more preferably at most 500 mm, more preferably at most 300 mm, more preferably at most 200 mm, more preferably at most 170 mm, more preferably about 156 mm.In some embodiments, the clear distance between the transport means and the hold-down means is preferably in a range from 10 mm to 1000 mm, more preferably from 50 mm to 500 mm, more preferably from 100 mm to 300 mm, more preferably from 150 mm to 250 mm, more preferably from 204 mm to 226 mm, more preferably about 210 mm. The clear distance between the transport means and the hold-down means is preferably at least 10 mm, more preferably at least 50 mm, more preferably at least 100 mm, more preferably at least 150 mm, more preferably at least 204 mm, more preferably about 210 mm. The clear distance between the transport means and the hold-down means is preferably at most 1000 mm, further preferably at most 500 mm, further preferably at most 300 mm, further preferably at most 250 mm, further preferably at most 226 mm, further preferably about 210 mm.The transport means and the hold-down means are preferably aligned substantially parallel to one another within the device. This is also advantageous for the vertical alignment of the wafers between the transport means and the hold-down means.The transport means and / or the hold-down means can be designed, for example, in the form of transport belts. Such embodiments of the invention are possible, but are less advantageous, since such transport belts must be guided through the device together with the wafers, in particular also into the process basin, through the process basin and out of the process basin. In addition to the wafer being introduced and removed, the problem thus arises of the conveyor belts being introduced into the process basin and the conveyor belts being removed from the process basin, whereby the possibilities for the design of the delimiting element are considerably restricted.Particularly preferably, therefore, the transport means are transport rollers and the hold-down means are hold-down rollers. The configuration in the form of rollers has the advantage that a transport of the wafers through the device, in particular also into the process basin, through the process basin and out of the process basin, is possible without the transport means and the hold-down means themselves likewise having to be guided into the process basin, through the process basin and out of the process basin. In particular, the transport rollers and the hold-down rollers are preferably stationary. The rollers therefore preferably only execute a rotational movement during the transport of the wafers, but no translational movement. The rollers therefore preferably do not move through the device together with the wafers, but remain in place. This results in a variety of degrees of freedom in the configuration of the delimiting element, since these only have to enable the transportation of the wafers into the process basin, through the process basin and out of the process basin, but not the transportation of the transportation means and the holding-down means, since these do not have to be guided into the process basin, through the process basin and out of the process basin. Instead, transport rollers and hold-down rollers are preferably provided inside and outside the process basin, which rollers remain in place in each case.Preferably, the transport means and / or the hold-down means have at least one depression, preferably exactly one depression per wafer, for receiving the wafers. This is advantageous in order to protect the wafers from lateral tilting.In certain preferred embodiments, the hold-down means are designed with an additional weight in front of the limiting element in order to ensure a particularly good guidance against the liquid flowing out.The device of the present invention is suitable in particular for carrying out inline methods, as already results from the alignment of the wafers between transport means and hold-down means and the transport of the wafers through the device ensured thereby. In an inline method, the wafers are transported individually in series one after the other through the system. It is also possible for a plurality of rows of wafers to be transported simultaneously next to one another (multi-track inline method).The device of the invention is configured in particular for the inline transport of vertically oriented wafers into the process basin, through the process basin and out of the process basin. The spacing of the transport means and the hold-down means corresponds, on account of the vertical orientation of the wafers, in particular to the length or the width of the wafers, wherein the length and width of the wafers are generally identical in view of the usually square base area of the wafers. The length and width of the wafers exceed their thickness by a multiple, generally at least 100 times.The device preferably has a tank which is connected to the process basin in such a way that chemical process solution can be transferred from the tank into the process basin. The device preferably has a pump for transferring the chemical process solution from the tank into the process basin.By means of the limiting element according to the invention, the volume flow of process solution flowing out of the process basin can be significantly reduced. In order to be able to return process solution, which possibly flows out of the process basin on account of a residual volume flow remaining despite these measures, into the process basin, the device preferably has at least one collecting basin for receiving process solution emerging from the process basin. The collecting basin is preferably connected to the tank in such a way that process solution absorbed in the collecting basin can be returned to the tank. This ensures that process solution emerging from the process basin is not lost, but can be used again for processing the wafers.The present invention also relates to an inline method for processing wafers with a chemical process solution, comprising the following steps: a) providing vertically oriented wafers, b) providing a process basin according to the present invention with process solution located therein, c) introducing the vertically oriented wafers into the process basin, d) carrying the vertically oriented wafers through the process basin and the process solution located therein, such that the wafers are brought into contact with the process solution, e) carrying out the vertically oriented wafers from the process basin, wherein the introduction, passage and execution according to steps c) to e) takes place in a substantially horizontal direction of movement. Preferably, the process is carried out with an apparatus of the present invention.The process of the present invention is an inline process. In an inline method, the wafers are transported through the system in series one after the other. It is also possible for a plurality of rows of wafers to be transported simultaneously next to one another (multi-track inline method).Preferably, a plurality of rows of wafers, in particular 2 to 1000 rows of wafers, for example 5 to 500 rows of wafers, 10 to 200 rows of wafers, 20 to 100 rows of wafers, or 30 to 50 rows of wafers, are transported simultaneously next to one another through the same process basin. The distance between two rows of wafers transported simultaneously next to one another through the process basin is preferably 0.4 mm to 40 mm, more preferably from 1 mm to 10 mm, more preferably from 2 mm to 6 mm, more preferably from 4 mm to 5 mm, more preferably from 4.5 mm to 4.9 mm, more preferably from 4.7 mm to 4.8 mm.The method of the invention is a method for processing wafers with a chemical process solution. Preferred wafers are silicon wafers, in particular multicrystalline silicon wafers. The processing of the wafers is preferably texturing. Such texturing of wafers is known and is used above all in the production of solar cells. The process solution used preferably comprises hydrofluoric acid (HF) and nitric acid (HNO 3) for processing multicrystalline wafers or an aqueous solution of potassium hydroxide (KOH) or sodium hydroxide (NaOH), to which one or more additives are added for processing monocrystalline wafers.According to step a) of the method according to the invention, vertically oriented wafers are provided. The length and width of the wafers exceed their thickness by a multiple, generally 100 times to 1000 times. As a result, wafers have two main surfaces, each defined by the length and width of the wafers. Wafers with round main surfaces are also conceivable, in which the main surfaces are bounded by their circumference. A substantially vertical orientation of the wafers corresponds to an orientation in which the two main surfaces of a wafer are arranged such that surface vectors standing perpendicular to the main surfaces are oriented substantially horizontally. Preferably, the surface vectors of the two main surfaces form an angle of at least 70° and at most 110°, further preferably of at least 80° and at most 100°, further preferably of at least 85° and at most 95°, further preferably of about 90°, with the vector of the horizontal direction of movement of the wafers according to the movement of steps c) to e) of the method.According to step b) of the method according to the invention, a process basin with process solution located therein is provided. The process solution preferably contains hydrofluoric acid (HF) and nitric acid (HNO 3) in the case of texturing of multicrystalline wafers or a mixture of potassium hydroxide solution (KOH) and one or more organic additives in the case of texturing of monocrystalline wafers.The processing of the wafers with the chemical process solution is carried out by the wafers being guided through the process basin, such that the wafers are brought into contact with the process solution located in the process basin. The time period between the introduction of the wafers into the process basin and the removal of the wafers from the process basin is preferably 15 to 180 seconds, more preferably 30 to 120 seconds, more preferably 60 to 90 seconds, for monocrystalline wafers preferably 0.5 to 15 minutes, more preferably 1 to 10 minutes, more preferably 2 to 6 minutes.The vertically oriented wafers are introduced, passed through and executed according to steps c) to e) of the method according to the invention in a substantially horizontal direction of movement. This means that the wafers are guided in such a way that the distance of the center of gravity of the individual wafers from the surface of the process solution during steps c) to e) remains substantially unchanged. Preferably, the difference of the maximum distance and the minimum distance of the center of gravity of the individual wafers from the surface of the process solution during steps c) to e) is at most 20%, further preferably at most 10%, further preferably at most 5%, further preferably at most 2%, further preferably at most 1%, of the length of the corresponding wafers.The movement speed of the wafers during steps c) to e) of the method is preferably in a range from 0.5 m / min to 10 m / min, more preferably from 1 m / min to 6 m / min.The present invention also relates to the use of the device and / or the method of the invention for the production of solar cells and / or printed circuit boards. The invention can be used in particular to introduce wafers for solar cells which are processed vertically into a process basin (in particular continuously) and in the process keep the outflow of process solution particularly low. The invention can also be used for the etching of glasses, which are likewise preferably continuously moved into a process basin. The invention can also be used for the chemical surface treatment of workpieces which pass through a process basin for this purpose.DESCRIPTION OF THE FIGURESFIG. 1 shows an embodiment of a delimiting element 10 of the present invention, wherein the structuring of the inner wall 11 of the slot 12 comprises drop-shaped indentations 13. A part of the empty volume 14 of the indentations 13 is filled with a filling material 15. FIG. 1-1 is a perspective view of a restriction member 10. The region of the slot 12 is surrounded by a frame region 16. FIG. 1-2 is a front view of the limiting element 10 with a slot 12 and a frame area 16. FIG. 1-3 is a side view of the delimiting element 10, it can be seen that the delimiting element 10 is designed with a greater depth in the region of the slot 12 than in the frame region 16, The delimiting element 10 is designed asymmetrically in such a way that the depth in the region of the slot 12 in the direction of the interior of the process basin (left in FIG. 1-3 ) exceeding the depth of the frame region 16 is less than in the direction of the outer side of the process basin (right in FIG. 1-3 ). FIG. 1-3 also shows a sectional plane B-B. FIG. 1-4 shows a top view of the sectional plane B-B from FIGS. 1-3 along the viewing direction indicated by arrows in FIGS. 1-3. In FIGS. 1-4, a region C is marked by a circle. FIG. 1-5 shows an enlargement of the region C of FIGS. 1-4. It can be seen that the inner wall 11 of the slot 12 comprises drop-shaped indentations 13, wherein a part of the empty volume 14 of the indentations 13 is filled with a filling material 15. The indentations 13 are arranged to form an acute angle with the flow-out direction of the processing solution (from left to right in FIGS. 1-5 ). FIG. 2 shows an embodiment of a delimiting element 20 of the present invention, wherein the structuring of the inner wall 21 of the slot 22 comprises drop-shaped indentations 23. The indentations 23 consist entirely of empty volume 24. FIG. 2-1 is a perspective view of a restriction member 20. The region of the slot 22 is surrounded by a frame region 26. FIG. 2-2 is a front view of the limiting element 20 with a slot 22 and a frame region 26. FIG. 2-3 is a side view of the delimiting element 20, it can be seen that the delimiting element 20 is designed with a greater depth in the region of the slot 22 than in the frame region 26, The delimiting element 20 is designed asymmetrically in such a way that the depth in the region of the slot 22 in the direction of the interior of the process basin (left in FIG. 2-3 ) exceeding the depth of the frame region 26 is less than in the direction of the outer side of the process basin (right in FIG. 2-3 ). FIG. 2-3 also shows a sectional plane B-B. FIG. 2-4 shows a plan view of the sectional plane B-B from FIG. 2-3 along the viewing direction indicated by arrows in FIG. 2-3. In FIGS. 2-4, a region C is marked by a circle. FIG. 2-5 shows an enlargement of the region C from FIG. 2-4. It can be seen that the inner wall 21 of the slot 22 comprises drop-shaped indentations 23, wherein the indentations 23 consist entirely of empty volumes 24. The indentations 23 are arranged to form an acute angle with the flow-out direction of the processing solution (from left to right in FIGS. 2-5 ).FIGS. 3 and 4 show a delimiting element 30 as an illustrative example, wherein the structuring of the inner wall 31 of the slot 32 has channels 33. A counter-current to the outflowing process solution can be generated by the channels 33 by supplying the channels 33 with a fluid via a feed line 37. FIG. 3-1 is a front view of the inside of a limiting element 30 of the present invention with a slot 32 and a frame region 36. Two sectional planes A-A and B-B are also shown, the sectional plane A-A running through the slot 32. FIG. 3-2 shows a plan view of the sectional plane B-B from FIG. 3-1 along the viewing direction indicated by arrows in FIG. 3-1. In FIGS. 3-2, two areas E and G are marked by circles. The delimiting element 30 is designed asymmetrically in that the depth beyond the depth of the frame region 36 in the region of the slot 32 in the direction of the interior of the process basin (at the bottom in FIGS. 3-2 ) is less than in the direction of the outer side of the process basin (at the top in FIGS. 3-2 ). FIG. 3-3 shows an enlargement of the region E from FIG. 3-2. The inner wall 31 of the slot 32 has channels 33. In addition, a lead 37 can be seen. The channels 33 are arranged to form an acute angle with the flow-out direction of the process solution (from bottom to top in FIGS. 3-3 ). FIG. 3-4 shows an enlargement of the region G from FIG. 3-2. The channels 33a have a connection to the supply line 37 in the sectional plane B-B. In the case of other channels 33 b, the connection to the feed line 37 is in a different sectional plane, so that no connection to the feed line 37 can be seen in FIGS. 3-4. The channels 33 are arranged to form an acute angle with the flow-out direction of the process solution (from bottom to top in FIGS. 3-4 ). FIG. 4-1 shows a top view of the sectional plane A-A from FIG. 3-1 along the viewing direction indicated by arrows in FIG. 3-1. It can be seen that the structure 38 has a main feed line 37 a. In the area of the slot, a plurality of channels 33 can be seen. Three sectional planes D-D, H-H and L-L are also shown. The delimiting element is designed asymmetrically in that the depth beyond the depth of the frame region in the region of the slot in the direction of the interior of the process basin (on the right in FIG. 4-1 ) is less than in the direction of the outer side of the process basin (on the left in FIG. 4-1 ). FIG. 4-2 is a plan view of the sectional plane D-D of FIG. 4-1 along the viewing direction indicated by arrows in FIG. 4-1. Inside the structure is the main lead 37a. FIG. 4-3 is a plan view of the sectional plane H-H of FIG. 4-1 along the viewing direction indicated by arrows in FIG. 4-1. The inner wall of the slot 32 has a plurality of channels 33. The channels 33 are arranged to form an acute angle with the direction of outflow of the process solution (from right to left in FIGS. 4-3 ). FIG. 4-4 is a plan view of the sectional plane L-L of FIG. 4-1 along the viewing direction indicated by arrows in FIG. 4-1. The structure 38 has a main feed line 37 a. In the region of the slot, a plurality of secondary feed lines 37 bare shown.List of reference characters10, 20, 30 Delimiting element 11, 21, 31 Inner wall 12, 22, 32 Slot 13, 23 Indentations 14, 24 Empty volume 15 Filling material 16, 26, 36 Frame region 33, 33 a, 33 bChannel 37 Feed line 37 a Haupt feed line 37 b Neben feed line 38 Structure

Claims

Delimiting element (10, 20, 30) for a process basin for receiving a chemical process solution, wherein the delimiting element (10, 20, 30) is provided with at least one slot (12, 22, 32) for passing wafers through the delimiting element (10, 20, 30), wherein an inner wall (11, 21, 31) of the slot (12, 22, 32) is structured in such a way that the chemical process solution flowing out of the process basin experiences a pulse change such that an outflowing volume flow is reduced, wherein the structuring of the inner wall (11, 21, 31) of the slot (12, 22, 32) comprises drop-shaped indentations (13, 23).The restriction member (10, 20, 30) according to claim 1, wherein the indentations (13, 23) are arranged to form an acute angle with an outflow direction of the chemical process solution.A process basin for receiving a chemical process solution, wherein the process basin comprises one or more delimiting elements (10, 20, 30) according to at least one of claims 1 to 2, and wherein the at least one slot (12, 22, 32) is vertically oriented.An apparatus for processing wafers with a chemical process solution comprising a process basin according to claim 3.Inline method for processing wafers with a chemical process solution comprising the following steps: a) providing vertically oriented wafers, b) providing a process basin according to claim 3 with chemical process solution present therein, c) introducing the vertically oriented wafers into the process basin, d) passing the vertically oriented wafers through the process basin and the chemical process solution present therein, such that the wafers are brought into contact with the chemical process solution, e) carrying out the vertically oriented wafers from the process basin, wherein the introduction, passage and execution according to steps c) to e) takes place in a substantially horizontal direction of movement.Use of the device according to claim 4 for the production of solar cells and / or printed circuit boards.

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